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. 2024 Apr 16;19(4):e0302076. doi: 10.1371/journal.pone.0302076

Polymicrobial bloodstream infections a risk factor for mortality in neonates at the national hospital, Tanzania: A case-control study

Joel Manyahi 1,*, Agricola Joachim 1, Frank Msafiri 1, Mary Migiro 1, Anthon Mwingwa 1, Mabula Kasubi 2, Helga Naburi 3, Mtebe Venance Majigo 1
Editor: Iddya Karunasagar4
PMCID: PMC11020784  PMID: 38625965

Abstract

Background

Polymicrobial bloodstream infections (BSI) are difficult to treat since empiric antibiotics treatment are frequently less effective against multiple pathogens. The study aimed to compare outcomes in patients with polymicrobial and monomicrobial BSIs.

Methods

The study was a retrospective case-control design conducted at Muhimbili National Hospital for data processed between July 2021 and June 2022. Cases were patients with polymicrobial BSI, and controls had monomicrobial BSI. Each case was matched to three controls by age, admitting ward, and duration of admission. Logistic regression was performed to determine independent risk factors for in-hospital and 30-day mortality.

Results

Fifty patients with polymicrobial BSI and 150 with monomicrobial BSI were compared: the two arms had no significant differences in sex and comorbidities. The most frequent bacteria in polymicrobial BSI were Klebsiella pneumoniae 17% (17/100) and Enterobacter species 15% (15/100). In monomicrobial BSI, S. aureus 17.33% (26/150), Klebsiella pneumoniae 16.67% (25/150), and Acinetobacter species 15% (15/150) were more prevalent. Overall, isolates were frequently resistant to multiple antibiotics tested, and 52% (130/250) were multidrug resistance. The 30-day and in-hospital mortality were 33.5% (67/200) and 36% (72/200), respectively. On multivariable analysis, polymicrobial BSIs were independent risk factors for both in-hospital mortality (aOR 2.37, 95%CI 1.20–4.69, p = 0.01) and 30-day mortality (aOR 2.05, 95%CI 1.03–4.08), p = 0.04). In sub-analyses involving only neonates, polymicrobial BSI was an independent risk factor for both 30-day mortality (aOR 3.13, 95%CI 1.07–9.10, p = 0.04) and in-hospital mortality (aOR 5.08, 95%CI 1.60–16.14, p = 0.006). Overall, the median length of hospital stay post-BSIs was numerically longer in patients with polymicrobial BSIs.

Conclusion

Overall, polymicrobial BSI was a significant risk for mortality. Patients with polymicrobial BSI stay longer at the hospital than those with monomicrobial BSI. These findings call for clinicians to be more aggressive in managing polymicrobial BSI.

Background

Bloodstream infections (BSI) in low-middle-income countries (LMICs) are steadily associated with poor treatment outcomes, with the rising concern associated with antibiotic-resistant bacteria. BSI has been reported in 10–13% of inpatients with severe febrile illness in East and West Africa, with an estimated case fatality rate of 12% [1, 2].

Following the reduction of malaria, a frequent cause of febrile illness in Tanzania, BSIs remain a common cause of hospitalization in children with febrile illness. In Tanzania, BSIs is detected in 11–14% of children with severe febrile illness [3, 4]. Studies have shown that BSIs in adults and children result in worse outcomes, such as high mortality and length of hospital stay [5–8]. In addition, increasing evidence of antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum beta-lactamases (ESBL), and multidrug-resistant (MDR) bacteria in BSIs, has been reported in Tanzania [3–5, 9].

Studies in Tanzania have reported that BSIs due to antibiotic-resistant bacteria had a significantly higher risk of death than those with antibiotic susceptible bacteria [5, 8, 9]. Mortality in children with ESBL BSI was approximately 2-fold higher than in non-ESBL septicemia [9]. Our recent study found that patients with MDR BSIs (aOR = 15) had a higher risk of dying than those with non-MDR BSIs [5]. However, studies still need to evaluate the outcomes of polymicrobial BSIs in Tanzania thoroughly.

Polymicrobial BSIs are frequently difficult to treat, and choosing the appropriate empiric antibiotics effective for more than one pathogen is more challenging. It is, therefore, vital to promptly identify the pathogens causing polymicrobial BSIs and administer the proper empiric antibiotics/drugs. In addition, studies on adults and children from other settings have demonstrated that mortality attributable to polymicrobial BSIs is higher than in monomicrobial BSIs [10–13]. Therefore, we carried out this retrospective case-control study at Muhimbili National Hospital (MNH) to ascertain the impact of polymicrobial BSIs on patient outcomes. A better understanding of the risk factors for worse outcomes in patients with BSIs would improve clinical outcomes for patients.

Materials and methods

Study setting and design

This was a retrospective case-control study for the data processed between July 2021 and June 2022 at MNH, Dar es Salaam, Tanzania. The data for this study were accessed and collected between July 1, 2022, and September 30, 2022. MNH is a tertiary-level hospital in Tanzania and serves as a teaching hospital for Muhimbili University of Health and Allied Sciences (MUHAS). It has a 1,500-bed capacity and attends up to 2,000 outpatients daily. The hospital has an infection control policy and an infection prevention and control (IPC) unit. Furthermore, blood culture sample in all wards is collected under aseptic condition and transferred to the laboratory within one hour of collection. Under ideal situations, the laboratory reporting system allows to flag clinicians with preliminary results immediately when the blood culture flag-positive and final results 2–3 days after the blood culture is positive. In this retrospective case-control study, cases were patients with polymicrobial BSIs, and controls were patients with monomicrobial BSIs. Each case was matched to three controls by age ±5 years (neonates ±5 days), admission date, and admitted wards.

Blood culture results of patients aged 0–86 years with polymicrobial and monomicrobial growth were first retrieved from the laboratory registry. Patients’ information, including ages, sex, admission wards, date of admission, time of diagnosis of BSIs, date of discharge, comorbidity, and clinical outcomes (death or survival), were collected from clinical case notes. All cases and their matched controls with complete demographics and clinical information were included in the analysis. Only the first episode was included in cases where patients had two or more blood cultures positive with similar organisms. Patients with incomplete demographics and medical records were excluded from the analysis.

Microbiological methods for blood culture at MNH

Blood samples for culture were incubated in the BD BACTEC FX 200 at MNH, central pathology laboratory. Only one set of blood cultures was performed in adults and pediatrics. A set of BD BACTEC Plus Aerobic and Anaerobic/F Culture Vials (Becton Dickinson, BD) were processed for adults. For pediatrics, 1–3 mL of blood sample was collected in the BD BACTEC Peds PlusTM/F Culture Vials. Blood culture vials in BD BACTEC 200 were incubated for a maximum of five days before being regarded as a negative culture.

Positive blood cultures were Gram-stained and sub-cultured into sheep blood agar, chocolate agar, and MacConkey agar. Identification of bacteria was based on colonial morphology, Gram stain, and biochemical tests, including conventional API20E (BioMérieux, Marcy, I’Etoile, France) and Staphaurex (Remel Europe Ltd, Dartford, UK). Antimicrobial susceptibility testing was performed and interpreted according to clinical and laboratory standard institute (CLSI) guidelines [14].

Definition of terms

Polymicrobial BSI was defined as bacteremia with at least two different organisms from the same blood culture. The onset of BSI was defined as the day when the blood was drawn for culture that subsequently produced positive pathogenic growth. Laboratory-confirmed BSIs was defined as blood culture with the growth of recognizable pathogens in patients with signs and symptoms of BSIs. Coagulase-negative staphylococci were considered a pathogen in immunosuppressed patients and neonates, in accordance with hospital blood culture standard operational procedure. Micrococcus, Corynebacterium, Viridans Group streptococci, and Bacillus species were considered as contaminants. The 30-day mortality was defined as death from any cause within 30 days of the onset of BSI. In-hospital mortality was defined as death from any cause during index hospitalization following diagnosis of BSI. The length of hospital stay was calculated from the date of diagnosis of BSIs. It excluded all patients with in-hospital mortality.

In addition, appropriate treatment was defined as empirical antimicrobial therapy with an antibiotic that has in vitro activity against the isolated pathogen based on susceptibility testing results.

Statistical analysis

Categorical variables were presented as frequency and percentages. A comparison of categorical variables between cases and controls was performed using Pearson chi-square. The median length of hospital stays among cases, and controls was compared using the Wilcoxon rank-sum test. Binary logistic regression compared outcomes of interest (30-day and in-hospital mortality) between cases and controls. All plausible biological variables (Admission ward, comorbidity, and appropriate treatment) with p-values < 0.20 on the bivariate analysis were included in the logistic regression modal for the multivariable analysis.

Multivariable logistic regression was performed to find an independent association of polymicrobial and monomicrobial BSIs to 30-day and in-hospital mortality. We adjusted for age, sex, admission ward, appropriate treatment, and comorbidity as potential confounders, defining confounders as factors that change the effect size by ≥10%.

We performed a sub-analysis for neonates and non neonates, where bivariate and multivariable logistic regression were performed. Independent associations between polymicrobial BSIs and outcomes of interest (30-day and in-hospital mortality) were adjusted for age, sex, admission ward, and comorbidity. All statistical analysis was performed using STATA version 16 (College Station, TX). A significance level of ≤0.05 was used, and all p-values refer to two-sided tests.

Ethics approval and consent to participate

Ethical approval was granted by the Muhimbili University of Health and Allied Sciences senate and publications committee Ref. No DA.25/111/01C/157. Permission to conduct the study was approved by Muhimbili National Hospital management. As the study was a retrospective study using identified patients, informed consent was waived by Muhimbili University of Health and Allied Sciences senate and publication committee. All methods were carried out under relevant guidelines and regulations in the declaration.

Results

Demographics and clinical characteristics

Between July 2021 and June 2022, 3398 blood cultures were processed at the microbiology laboratory of MNH. Overall, the proportion of BSI was 19% (642/3398). From 642 patients with BSI, we obtained 50 cases with polymicrobial BSI, matched to 150 controls with monomicrobial BSI in a ratio of 1:3. The age distributions among the cases and controls ranged from 1 day to 86 years, with majority of partipants being neonates. There were no significant differences in sex and comorbidities between polymicrobial BSI and monomicrobial BSI (Table 1).

Table 1. Demographic-clinical characteristics of the participants.

Variable Monomicrobial BSIs(N = 150) Polymicrobial BSIs (N = 50) p-value
Age (median, IQR) 1 (1–40) 1 (1–40)
<1month 69 23
<1 year 18 6
2–16 year 9 3
>17 years 54 18
Sex, Male 75 (50%) 26 (52%) 0.8
Ward, ICU 90 (60%) 31 (62%) 0.8
Comorbidity, Yes 68 (45.3%) 22 (44%) 0.87
Appropriate treatment, Yes 72 (48%) 18 (36%) 0.14
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IQR- Interquartile ratio; ICU-intensive care unit

Microbiology of bloodstream infections

Table 2 provides the microbiology for both polymicrobial and monomicrobial BSIs. The bacteria-causing polymicrobial and monomicrobial BSIs were similar, with the predominance of Gram-negatives, although they varied in frequency. The most frequent bacteria in polymicrobial BSIs were Klebsiella pneumoniae 17% (17/100) and Enterobacter species 15% (15/100). Combinations of these two bacteria, as well as S. aureus/Pseudomonas aeruginosa and Acinetobacter species/CoNS, were also frequent, occurring in three instances each. In monomicrobial BSIs, S. aureus 17.33% (26/150), Klebsiella pneumoniae 16.67% (25/150), and Acinetobacter species 10% (15/150) were more prevalent (Table 2).

Table 2. Bacterial isolates from monomicrobial and polymicrobial bloodstream infections.

Bacteria Monomicrobial BSI N(%) Polymicrobial BSI N(%)
K. pneumoniae 25 (16.67) 17 (17.00)
E. coli 17(11.33) 7 (7.00)
Enterobacter spp 13(8.67) 15(15.00)
*Other Enterobacterales 13 (8.67) 16 (16.00)
Acinetobacter spp 15 (15) 9 (9.00)
P. aeruginosa 14 (9.33) 8 (8.00)
#Non-Enterobacterales 4 (2.67) 6(6.00)
S. aureus 26 (17.33) 9(9.00)
CoNS 20 (13.33) 9(9.00)
Streptococcus spp 2(1.33) 3(3.00)
Candida spp 1 (0.67) 1 (1.00)
Total 150 100
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*Other Enterobacterales: Morganella morganii, Serratia mercescens, Providencia spp, Citrobacter species

#Non-Enterobacterales: Aeromonas spp, Chromobacteria violaceum; CoNS:Coagulase negative Staphylococcus

Antimicrobial susceptibility pattern

Overall, isolates were frequently resistant to multiple antibiotics tested, and 53% (130/243) were multidrug resistance. We observed that 77% (27/35) of S. aureus and 85% (25/29) of coagulase-negative Staphylococcus were resistant to cefoxitin, hence methicillin-resistant strains. All Enterobacterales were frequently resistant to all antibiotics tested except for meropenem and amikacin. Furthermore, S. aureus was less resistant to chloramphenicol (28%), clindamycin (38%), and trimethoprim-sulfamethoxazole (45%) (Table 3).

Table 3. Antimicrobial susceptibility patterns of bacteria from bloodstream infections.

Percent Resistance
Bacteria (n) AMP AMC TZP CRO CAZ FEP MEM AMK CN CIP CHL SXT P FOX ERY CLI
K. pneumoniae (42) 100 80 75 72 71 76 44 39 61 69 68 59
E. coli (24) 92 81 75 80 74 90 26 44 53 76 36 100
Enterobacter spp (28) 100 89 60 76 81 74 79 36 70 79 69 70
*Other Enterobacterales (29) 84 75 38 84 52 87 45 38 60 58 53 69
Acinetobacter spp (24) 70 89 59 68 57 37 65 50 46 55
P. aeruginosa (22) 58 39 31 24 32 58 47
#Non-Enterobacterales (10) 63 33 44 0 22 56 22 14 67
S. aureus (35) 60 58 28 45 100 77 80 38
CoNS (29) 62 94 16 90 100 85 89 90
Overall 91 79 64 80 64 72 43 36 62 64 48 67 100 81 84 64
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AMK-Amikacin, AMC-Amoxycillin-clavulanic acid, AMP-Ampicillin, FOX-Cefoxitin, CAZ-Ceftazidime, CRO-Ceftriaxone, CHL-Chloramphenicol, CIP-Ciprofloxacin, CLI-Clindamycin, ERY-Erythromycin, GEN-Gentamicin, MEM-Meropenem, TZP-Tazobactam-piperacillin, P-Penicillin, SXTTrimethoprim-sulfamethoxazole. Other Enterobacterales: Morganella morganii, Serratia mercescens, Providencia spp, Citrobacter species

#Non-Enterobacterales: Aeromonas spp, Chromobacteria violaceum. CoNS:Coagulase negative Staphylococcus

Outcomes in bloodstream infections

Overall, the 30-day mortality was 33.5% (67/200). The risk of mortality was higher in polymicrobial BSI compared to monomicrobial BSI, with an odd ratio (OR) of 1.83 (95% confidence interval (CI) 0.95–3.54), though the difference was not statistically significant (p = 0.07). However, after adjusting for possible confounders including sex, age, the admission ward, appropriate treatment, and comorbidity in a multivariable model, polymicrobial BSI independently predicted 30-day mortality, aOR 2.05, 95%CI 1.03–4.08), p = 0.04. Additionally, in-hospital mortality was 36% (72/200), with cases dying more frequently than controls (50% vs. 31.3%). We observed that polymicrobial BSI was a risk factor for in-hospital death based on univariable analysis crude odd ratio (cOR), 2.19, 95%CI 1.14–4.21, p = 0.02. We considered sex, age, the admission ward, appropriate treatment, and comorbidity in the final multivariable analysis model as potential confounding variables. After adjusting for these variables, we found that polymicrobial BSIs adjusted odd ratio (aOR) 2.37, 95% CI 1.20–4.69, p = 0.01, had an independent association with in-hospital mortality (Table 4).

Table 4. Multivariable analysis assessing the association between BSIs and mortality.

Outcome Monomicrobial BSIs Polymicrobial BSIs cOR, 95%CI, p-value aOR, 95%CI, p-value
All patients N = 150 N = 50
30-days mortality (%) 30 44 1.83 (0.95–3.54), 0.07 2.05, (1.03–4.08), 0.04
In-hospital mortality (%) 31.3 50 2.19 (1.14–4.21), 0.02 2.37, (1.20–4.69), 0.01
Neonates only N = 69 N = 23
30-days mortality (%) 42.03 65.22 2.78, 1.04–7.39, 0.04 4.02, 1.32–12.23, 0.01
In-hospital mortality (%) 42.03 73.91 4.20, 1.48–11.92, 0.007 6.18, 1.89–20.22, 0.003
Non-neonates N = 81 N = 27
30-days mortality (%) 19.75 25.93 1.42, 0.51–3.94, 0.50 1.55, 0.55–4.41, 0.59
In-hospital mortality (%) 22.22 29.63 1.47, 0.55–3.91, 0.45 1.59, 0.58–4.36, 0.36
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BSI: Bloodstream infections, cOR: crude odd ratio, aOR: adjustable odd ratio, CI: Confidence interval

In sub-analyses involving only neonates, we found that polymicrobial BSI had an independent association with both 30-day mortality (aOR 4.02, 95% CI 1.32–12.32, p = 0.01) and in-hospital mortality (aOR 6.18, 95% CI 1.89–20.22, p = 0.003) after adjusting for, sex, appropriate treatment, and comorbidities. For all age groups and neonates, the median length of hospital stay post-BSIs was numerically longer in patients with polymicrobial than in those with monomicrobial BSIs, though the difference was not statistically significant (Table 5).

Table 5. Length of hospital stay post-bloodstream infections.

Outcome Monomicrobial BSIs Polymicrobial BSIs p-value
All patients N = 105 N = 28
LOS (median, IQR) 13 (5–24) 26 (6–37) 0.2
Neonates only N = 43 N = 8
LOS (median, IQR) 13 (6–32) 32 (21.5–62) 0.07
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LOS: Length of hospital stay, IQR: Interquartile range, BSI: Bloodstream infections

In a sub-analysis of non-neonates, we observed that polymicrobial BSI had no association with both in-hospital and 30-day mortality (Table 5).

Discussion

Our study demonstrates that polymicrobial BSIs are significantly associated with in-hospital mortality compared to monomicrobial BSIs in patients of all age groups. We observed significantly higher 30-day mortality in participants with polymicrobial BSI than those with monomicrobial BSI. We also found that patients with polymicrobial BSIs had a longer median length of hospital stay than patients with monomicrobial BSIs, but the differences were not statistically significant. A similar finding has been reported from previous studies, which found polymicrobial BSIs increase the risk of mortality [11, 15]. The difficulties in selecting appropriate empiric antimicrobials targeting multiple pathogens and delays in reporting blood culture results could impact our study’s observed findings.

Most participants in this study received inappropriate treatment, which was more common in the polymicrobial BSI arm; however, we adjusted for inappropriate treatment in our analysis, and polymicrobial remained the main contributor to mortality. We could not account for the turn-around time of reporting polymicrobial BSI bacteriology results to clinicians as a possible contributor to the delay in initiation of treatment, possibly leading to increased mortality. Subsequently, ceftriaxone was the most commonly prescribed empiric antibiotic on review of clinical case notes, and most bacteria we isolated were resistant to this antibiotic. Our findings call for microbiologists and clinicians to be more vigilant when blood culture reveals polymicrobial BSI. We noted that the blood culture standard operating procedure does not detail how to communicate when polymicrobial BSIs are detected. On the other hand, the guidelines for treating sepsis consider only aerobic and anaerobic polymicrobial BSIs, and consideration is not given to aerobic-aerobic polymicrobial BSIs.

When we examined the neonates’ risk factors for 30-day mortality, we found polymicrobial BSIs were an independent risk for mortality in neonates after adjusting for all possible confounders. The previous study in other settings has observed similar findings in neonates, where polymicrobial bloodstream infections were associated with 3 fold increased risk of mortality compared to monomicrobial bloodstream infection [10]. However, other studies in neonates have found comparable 30-day mortality between polymicrobial and monomicrobial BSIs [16, 17]. Immature immunity in neonates increases vulnerability to serious infections leading to an increased mortality risk. On the other hand, inappropriate antibiotic therapy compounded by overwhelming virulence from more than one pathogen would have led to the severity of illness in neonates, leading to the worse clinical outcomes observed.

Studies have reported that polymicrobial infections are associated with forming polymicrobial biofilms, which tend to increase pathogens’ virulence, host immune evasion, and antibiotic resistance, hence poor treatment outcomes [18–20]. Polymicrobial BSI occurs more in neonates with severe underlying conditions and prolonged indwelling central venous catheters [16]. As central venous catheters were not commonly used at MNH during study time, the observed cases can be attributed to overwhelming illness.

We found that the median length of hospital stay was longer in patients with polymicrobial BSIs than in patients with monomicrobial BSIs. This could be due to the ineffectiveness of empiric antibiotic therapy since it was impossible for the prescribed empiric antibiotics to be effective in two different organisms. Therefore, the likelihood of receiving inappropriate treatment resulting in failure and prolonged hospital stays was obvious. Our findings are similar to those reported in the studies conducted in other settings [13, 21–23]. This finding calls for establishing a local cumulative antibiogram to guide empiric therapy in suspected bacteria infections, as it currently not existing in health facilities in the country.

The microbiology of polymicrobial BSIs was similar to that of monomicrobial infections in this study, with the predominant Gram-negative bacteria. This indicates that the sources for polymicrobial and monomicrobial BSIs are the same. Other studies examining the microbiological profiles of polymicrobial and monomicrobial BSIs have reported similar microbiology patterns in both cases [12, 17, 24]. However, depending on the variability of the population studied, the predominance of either Gram-positive or Gram-negative has been reported. On the other hand, we found that most bacteria causing BSIs in our study were MDR, which limits the available treatment options in our settings. The findings of this study emphasize the need for microbiology laboratories to promptly perform and report antimicrobial susceptibility results to guide evidence-based antibiotics therapy.

One of the important caveats of our study was that it was a retrospective design dependent on recorded information from clinical case notes. Information like the severity of BSIs and the classification of BSIs (community onset versus hospital onset) was not documented in the clinical case notes, and this means missing data could introduce information bias. However, missing end-point outcomes would be non-differentially distributed evenly across polymicrobial and monomicrobial BSIs. Furthermore, we performed multivariable analysis to control for possible confounding variables associated with mortality. Another important limitation of our study is that we could not assess the risk factors for polymicrobial BSIs because of the missing information. Understanding risk factors for polymicrobial BSIs would be critical to controlling and preventing infections before they even occur. However, our findings call for microbiologists and clinicians to manage polymicrobial BSIs because of the associated risk aggressively.

Conclusion

In neonates, polymicrobial BSI is an independent risk for 30-day and in-hospital mortality. Overall, the median length of hospital stay was longer in patients with polymicrobial BSI than those with monomicrobial BSI. These findings highlight the need for clinicians to be more aggressive when polymicrobial BSI is detected. The laboratory should also prompt notify clinician when polymicrobial growth is detected in blood culture.

Supporting information

S1 Data

(XLSX)

pone.0302076.s001.xlsx (69.6KB, xlsx)

Acknowledgments

The authors acknowledge the members of the bacteriology section at the central pathology laboratory, MNH.

Data Availability

Minimal data have been included in the submission as a Supporting information.

Funding Statement

The author(s) received no specific funding for this work.

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  • 22.Song F, Zhang K, Huang J, Qian Z, Zhou H, Cai J, et al. Clinical Characteristics, Risk Factors, and Outcomes of Patients with Polymicrobial Klebsiella pneumoniae Bloodstream Infections. Biomed Res Int. 2021;2021:6619911. Epub 20210619. doi: 10.1155/2021/6619911 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Sancho S, Artero A, Zaragoza R, Camarena JJ, González R, Nogueira JM. Impact of nosocomial polymicrobial bloodstream infections on the outcome in critically ill patients. Eur J Clin Microbiol Infect Dis. 2012;31(8):1791–6. Epub 20111214. doi: 10.1007/s10096-011-1503-8 . [DOI] [PubMed] [Google Scholar]
  • 24.Goldman S, Itshaki O, Shochat T, Gafter-Gvili A, Yahav D, Rubinovitch B, et al. Risk Factors and Outcome of Polymicrobial Bacteremia: A Retrospective Cohort Study. Isr Med Assoc J. 2020;22(5):279–84. . [PubMed] [Google Scholar]

Decision Letter 0

Iddya Karunasagar

23 Oct 2023

PONE-D-23-28734Polymicrobial bloodstream infections a risk factor for mortality at the national hospital, Tanzania: A case-control studyPLOS ONE

Dear Dr. Manyahi,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Please address all points raised by the reviewers and comments made directly on the manuscript. 

==============================

Please submit your revised manuscript by Dec 07 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Iddya Karunasagar

Academic Editor

PLOS ONE

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Additional Editor Comments:

Both reviewers have raised a number of points in data analysis and presentation that needs improvement. Please address all comments point by point.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The evidence for poly-microbial BSI is not very clear just isolation of two or more bacteria from blood culture does not substantiate the the poly-microbial BSI.

Line 164 and 165 Acinetobacter and CONS, Pseudomonas and S.aureus in these combinations CONS and S.aureus could be skin contaminants in which case BSI is mono-microbial only. Therefore selection criteria of poly-microbial BSI cases to be clearly defined in which clinical conditions or comorbidities poly-microbial BSI is a possibility only such case to be selected.

Line 166 and 167 Acinetobacter 15% (15/150) calculation error.

While mentioning the antibiotic resistance consider the antibiotics used for blood stream infections not clindmycin, cotrimoxazole and chloramphenicol for S.aureus.

Which are the disease comorbidities were considered for statistical analysis because these disease comorbidities will play very significant role in hospital mortality and 30 day mortality in patients with BSI besides the antimicrobial resistance.

Reviewer #2: The paper made an interesting reading, dealing with polymicrobial infections Vs Monomicrbial Infections , the microbiological and clinical impact of these with respect to 30 day mortality and the extended hospital stay etc.

Comments for the same are attached , the authors are advised to kindly refer to the same and address all the points mentioned

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachment

Submitted filename: reviewof Plos one artice.docx

pone.0302076.s002.docx (14.3KB, docx)
PLoS One. 2024 Apr 16;19(4):e0302076. doi: 10.1371/journal.pone.0302076.r002

Author response to Decision Letter 0

8 Dec 2023

Reviewer #1: The evidence for polymicrobial BSI is not very clear just isolation of two or more bacteria from blood culture does not substantiate the polymicrobial BSI.

Comment: Line 164 and 165 Acinetobacter and CONS, Pseudomonas and S.aureus in these combinations CONS and S.aureus could be skin contaminants in which case BSI is mono-microbial only. Therefore, selection criteria of polymicrobial BSI cases to be clearly defined in which clinical conditions or comorbidities polymicrobial BSI is a possibility only such case to be selected.

Response: Thank you for the comment. Our laboratory SoP for a blood culture states very clearly when to consider CoNS, and other possible skin contaminants as true pathogens, and we strictly adhered to the laboratory SoP in defining pathogens. S. aureus in blood culture is always considered a pathogen in our interpretation of the blood culture positive

Comment: Line 166 and 167 Acinetobacter 15% (15/150) calculation error.

Response: We appreciate for the comment, we have addressed calculation error

Comment: While mentioning the antibiotic resistance consider the antibiotics used for blood stream infections not clindamycin, cotrimoxazole and chloramphenicol for S. aureus.

Response: We appreciate for the comment. However, our results show the susceptibility pattern based on laboratory testing and not based treatment of S. aureus blood stream infections. In reporting AST results to clinician, our laboratory considers both bacteria and site of infections.

Comment: Which are the disease comorbidities were considered for statistical analysis because these disease comorbidities will play very significant role in hospital mortality and 30-day mortality in patients with BSI besides the antimicrobial resistance.

Response: Unfortunately, clinical conditions were so diverse, and a breakdown presentation was difficulties. Therefore, in our analysis we categorized either presence of comorbidity or not.

Reviewer #2: The paper made an interesting reading, dealing with polymicrobial infections Vs Monomicrobial Infections , the microbiological and clinical impact of these with respect to 30 day mortality and the extended hospital stay etc.

Comments for the same are attached , the authors are advised to kindly refer to the same and address all the points mentioned

The paper deals with the differences (Both Microbiological yield and clinical outcomes) in patients with Polymicrobial and Monomicrobial Bacteremia Infections; The Following observations are in order and must be addressed before the manuscript can be taken forward

Comment: The title of the paper does not reveal that the major component of the study is in children, adolescents, neonates, infants or adults. However, the Table No 4 & 5 refer to clinical outcomes in neonates only.

Response: Thank you for the comment. We agree that the title does not mention the major components of the participants. Our study aimed at creating awareness of the negative effects of polymicrobial bloodstreams on patient care for both laboratory personnel and clinicians. Being a lab-based retrospective, we therefore enrolled all patients with polymicrobial bloodstreams matching their counterparts by age, date of admission, and admitting wards. However, because we had a significant number of participants who were neonates, we decided to perform a sub-analysis for neonates only, as appears in Tables 4 and 5. On the other hand, we have done sub-analysis in none neonates, Therefore, we have modified the title to show the component affected.

Comment: Moreover, the Table – 1 which deals with age and sex distribution does not give a breakdown of the age groups and refers to a median age alone.

Response: Thank you for the comment. Our study design was a case control, which was matched by age; therefore, we found most participants were populated in the same age category. However, we have added age breakdown in table1

Comment: The discussion section refers to certain observations which have been compared with other studies and these deal with outcomes in neonates only.

Response: We appreciate for the comment, we have improved our citation and omitted references which do not match with our study population

Comment: In the section “Materials and Methods “ “study setting and design ‘ the authors have stated that results are obtained in age groups from 1-86 years and of these 50 patients were selected and 150 controls. What was the age distribution taken into consideration when this selection was made. The clinical outcomes may be different in different age groups with polymicrobial bacteremia.

Response: We appreciate for the good comment, in this study we included all age groups from 0-86. Understanding the age have influence on the clinical outcome, first we adjusted for age in multivariable analysis. Then we did stratification analysis for neonate only and non-neonate. Having this analysis, we are assured we have controlled the age a possible confounder influencing our outcome of interest.

Comment: The authors have stated a definition for Polymicrobial infections in the section “Definition of terms”. However, the term polymicrobial need not be restricted to 2 organisms as there are instances of blood stream infections caused by more than 2 organisms, including a yeast. How has the selection for polymicrobial infections data been made. Moreover the Results section talks of common organisms as Nos/ 100 which means that the authors have considered only 2 organisms per blood culture in a patient (total no of patients being 50).

Response: Thank you for this observation. We completely agree polymicrobial infections can be caused by two or more bacteria. Unfortunate, during the review of the laboratory data, we did not come to an instance of having more than two pathogens. Furthermore, we had one case of polymicrobial bloodstream infections involving bacteria and candida species.

Comment: The clinical outcomes for blood stream infections in conditions such as Perforation peritonitis, Carcinoma colon etc may depend on the nos of organisms causing the Polymicrobial Infection. Has this been taken into account. There is no mention anywhere in the manuscript and yeasts do not form part of the study.

Response: In our analysis we considered co-morbidities as one of the confounders, which could influence our outcome of interest, and in multivariable analysis we controlled for comorbidities, however, we found this did not influence our outcome. Furthermore, we did not document any case with perforation or peritonitis, but there was only one case of polymicrobial infections in patient with rectal carcinoma. In table 2, we have mentioned yeast being part of the study.

Comment: The authors have stated that Viridans streptococcus and Corynebacteria have been disregarded as contaminants. However, these organisms may assume huge clinical significance in certain clinical situations such as immunocompromise and malignancies in patients with BSI’s. The authors have not provided a break up of clinical conditions in the 50 cases and 150controls which in itself may skew the clinical outcome data of patients.

Response: Thank you for the comment. Our laboratory SoP for a blood culture states very clearly when to consider CoNS, Viridans Streptococcus, Corynebacterium as true pathogens, and we strictly followed the lab SoP regarding these as pathogenic. Unfortunately, clinical conditions were diverse, and a breakdown presentation in a table would be difficult for a reader.

Comment: The description of Results section under “Antimicrobial Susceptibility Pattern” does not match the data outlined in Table -3.

Response: Thank you for observation, we have edited on the total number of MDR bacteria

Comment: There is no reference to certain Resistance mechanisms such as Carbapenem resistant Enterobacterales (CRE), Amp C enzymes MLSBi/c detection in S. aureus. All of these do impact treatment outcomes. How have these been factored in the selection of 50 cases and 150 controls in the study as these would most certainly affect the final analyses

Response: Thank you for the valid comment. In the selection of cases and controls, we did not consider if patients had resistant strains or not because our study hypothesized that polymicrobial bloodstream infections were associated with poor treatment outcomes, and we designed this study as a case control to answer our research question. We had thought of controlling for MDR or resistant strains, but the analysis could have been different and not for a case-control study, maybe cross-sectional.

Comment: The section on Discussion gives vague references to 30-day mortality and extended hospital stay etc without actual figures and how these may compare with similar data brought out in other studies. There are equal references to other studies in neonates without actually discussing the distribution of cases among neonates in the present study.

Response: Thank you for the comments, we have improved our reference to include reference from similar study group.

Comment: Based on the data presented and discussed the authors may have to modify the conclusion section as no definite conclusions emerge out of the discussion cited.

Response: Thank you, we have rephrased our conclusion.

Attachment

Submitted filename: Response to reviewerd.docx

pone.0302076.s003.docx (20.2KB, docx)

Decision Letter 1

Iddya Karunasagar

28 Feb 2024

PONE-D-23-28734R1Polymicrobial bloodstream infections a risk factor for mortality in neonates at the national hospital, Tanzania: A case-control studyPLOS ONE

Dear Dr. Manyahi,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================Please address all comments of the reviewer and please indicate the changes in your response.==============================

Please submit your revised manuscript by Apr 13 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Iddya Karunasagar

Academic Editor

PLOS ONE

Additional Editor Comments:

Manuscript still needs improvement as per reviewer comments.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: The authors need to mark ALL the sentences in the manuscript where they have responded to the reviewer's comments. This has not been done.

There are still some grammatical errors that need correction.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachment

Submitted filename: PONE-D-23-28734_R1.pdf

pone.0302076.s004.pdf (941.7KB, pdf)
PLoS One. 2024 Apr 16;19(4):e0302076. doi: 10.1371/journal.pone.0302076.r004

Author response to Decision Letter 1

5 Mar 2024

Reviewer #3: The authors need to mark ALL the sentences in the manuscript where they have responded to the reviewer's comments. This has not been done.

There are still some grammatical errors that need correction.

Response: Thank you for the comments to improve our manuscript. We have added yellow highlights in areas we have made changes in a Revised Manuscript with Track Changes. Furthermore, we have addressed some of the grammatical errors as suggested.

In addition, below are authors response from the previous reviewers

Response to review

Review of the paper titled Polymicrobial Blood stream Infections; a risk factor for mortality at the National Hospital Tanzania; A case control study

Reviewer #1: The evidence for polymicrobial BSI is not very clear just isolation of two or more bacteria from blood culture does not substantiate the polymicrobial BSI.

Comment: Line 164 and 165 Acinetobacter and CONS, Pseudomonas and S.aureus in these combinations CONS and S.aureus could be skin contaminants in which case BSI is mono-microbial only. Therefore, selection criteria of polymicrobial BSI cases to be clearly defined in which clinical conditions or comorbidities polymicrobial BSI is a possibility only such case to be selected.

Response: Thank you for the comment. Our laboratory SoP for a blood culture states very clearly when to consider CoNS, and other possible skin contaminants as true pathogens, and we strictly adhered to the laboratory SoP in defining pathogens. S. aureus in blood culture is always considered a pathogen in our interpretation of the blood culture positive

Comment: Line 166 and 167 Acinetobacter 15% (15/150) calculation error.

Response: We appreciate for the comment, we have addressed calculation error

Comment: While mentioning the antibiotic resistance consider the antibiotics used for blood stream infections not clindamycin, cotrimoxazole and chloramphenicol for S. aureus.

Response: We appreciate for the comment. However, our results show the susceptibility pattern based on laboratory testing and not based treatment of S. aureus blood stream infections. In reporting AST results to clinician, our laboratory considers both bacteria and site of infections.

Comment: Which are the disease comorbidities were considered for statistical analysis because these disease comorbidities will play very significant role in hospital mortality and 30-day mortality in patients with BSI besides the antimicrobial resistance.

Response: Unfortunately, clinical conditions were so diverse, and a breakdown presentation was difficulties. Therefore, in our analysis we categorized either presence of comorbidity or not.

Reviewer #2: The paper made an interesting reading, dealing with polymicrobial infections Vs Monomicrobial Infections , the microbiological and clinical impact of these with respect to 30 day mortality and the extended hospital stay etc.

Comments for the same are attached , the authors are advised to kindly refer to the same and address all the points mentioned

The paper deals with the differences (Both Microbiological yield and clinical outcomes) in patients with Polymicrobial and Monomicrobial Bacteremia Infections; The Following observations are in order and must be addressed before the manuscript can be taken forward

Comment: The title of the paper does not reveal that the major component of the study is in children, adolescents, neonates, infants or adults. However, the Table No 4 & 5 refer to clinical outcomes in neonates only.

Response: Thank you for the comment. We agree that the title does not mention the major components of the participants. Our study aimed at creating awareness of the negative effects of polymicrobial bloodstreams on patient care for both laboratory personnel and clinicians. Being a lab-based retrospective, we therefore enrolled all patients with polymicrobial bloodstreams matching their counterparts by age, date of admission, and admitting wards. However, because we had a significant number of participants who were neonates, we decided to perform a sub-analysis for neonates only, as appears in Tables 4 and 5. On the other hand, we have done sub-analysis in none neonates, Therefore, we have modified the title to show the component affected.

Comment: Moreover, the Table – 1 which deals with age and sex distribution does not give a breakdown of the age groups and refers to a median age alone.

Response: Thank you for the comment. Our study design was a case control, which was matched by age; therefore, we found most participants were populated in the same age category. However, we have added age breakdown in table1

Comment: The discussion section refers to certain observations which have been compared with other studies and these deal with outcomes in neonates only.

Response: We appreciate for the comment, we have improved our citation and omitted references which do not match with our study population

Comment: In the section “Materials and Methods “ “study setting and design ‘ the authors have stated that results are obtained in age groups from 1-86 years and of these 50 patients were selected and 150 controls. What was the age distribution taken into consideration when this selection was made. The clinical outcomes may be different in different age groups with polymicrobial bacteremia.

Response: We appreciate for the good comment, in this study we included all age groups from 0-86. Understanding the age have influence on the clinical outcome, first we adjusted for age in multivariable analysis. Then we did stratification analysis for neonate only and non-neonate. Having this analysis, we are assured we have controlled the age a possible confounder influencing our outcome of interest.

Comment: The authors have stated a definition for Polymicrobial infections in the section “Definition of terms”. However, the term polymicrobial need not be restricted to 2 organisms as there are instances of blood stream infections caused by more than 2 organisms, including a yeast. How has the selection for polymicrobial infections data been made. Moreover the Results section talks of common organisms as Nos/ 100 which means that the authors have considered only 2 organisms per blood culture in a patient (total no of patients being 50).

Response: Thank you for this observation. We completely agree polymicrobial infections can be caused by two or more bacteria. Unfortunate, during the review of the laboratory data, we did not come to an instance of having more than two pathogens. Furthermore, we had one case of polymicrobial bloodstream infections involving bacteria and candida species.

Comment: The clinical outcomes for blood stream infections in conditions such as Perforation peritonitis, Carcinoma colon etc may depend on the nos of organisms causing the Polymicrobial Infection. Has this been taken into account. There is no mention anywhere in the manuscript and yeasts do not form part of the study.

Response: In our analysis we considered co-morbidities as one of the confounders, which could influence our outcome of interest, and in multivariable analysis we controlled for comorbidities, however, we found this did not influence our outcome. Furthermore, we did not document any case with perforation or peritonitis, but there was only one case of polymicrobial infections in patient with rectal carcinoma. In table 2, we have mentioned yeast being part of the study.

Comment: The authors have stated that Viridans streptococcus and Corynebacteria have been disregarded as contaminants. However, these organisms may assume huge clinical significance in certain clinical situations such as immunocompromise and malignancies in patients with BSI’s. The authors have not provided a break up of clinical conditions in the 50 cases and 150controls which in itself may skew the clinical outcome data of patients.

Response: Thank you for the comment. Our laboratory SoP for a blood culture states very clearly when to consider CoNS, Viridans Streptococcus, Corynebacterium as true pathogens, and we strictly followed the lab SoP regarding these as pathogenic. Unfortunately, clinical conditions were diverse, and a breakdown presentation in a table would be difficult for a reader.

Comment: The description of Results section under “Antimicrobial Susceptibility Pattern” does not match the data outlined in Table -3.

Response: Thank you for observation, we have edited on the total number of MDR bacteria

Comment: There is no reference to certain Resistance mechanisms such as Carbapenem resistant Enterobacterales (CRE), Amp C enzymes MLSBi/c detection in S. aureus. All of these do impact treatment outcomes. How have these been factored in the selection of 50 cases and 150 controls in the study as these would most certainly affect the final analyses

Response: Thank you for the valid comment. In the selection of cases and controls, we did not consider if patients had resistant strains or not because our study hypothesized that polymicrobial bloodstream infections were associated with poor treatment outcomes, and we designed this study as a case control to answer our research question. We had thought of controlling for MDR or resistant strains, but the analysis could have been different and not for a case-control study, maybe cross-sectional.

Comment: The section on Discussion gives vague references to 30-day mortality and extended hospital stay etc without actual figures and how these may compare with similar data brought out in other studies. There are equal references to other studies in neonates without actually discussing the distribution of cases among neonates in the present study.

Response: Thank you for the comments, we have improved our reference to include reference from similar study group.

Comment: Based on the data presented and discussed the authors may have to modify the conclusion section as no definite conclusions emerge out of the discussion cited.

Response: Thank you, we have rephrased our conclusion.

Attachment

Submitted filename: Response to reviewers comment.docx

pone.0302076.s005.docx (18.9KB, docx)

Decision Letter 2

Iddya Karunasagar

27 Mar 2024

Polymicrobial bloodstream infections a risk factor for mortality in neonates at the national hospital, Tanzania: A case-control study

PONE-D-23-28734R2

Dear Dr. Manyahi,

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Acceptance letter

Iddya Karunasagar

5 Apr 2024

PONE-D-23-28734R2

PLOS ONE

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