Abstract
Objectives
Our observational, retrospective study aimed to determine the correlation between bacteria isolated from bronchial aspirates of pediatric ICU patients (PICU) with respiratory infections and those obtained from conjunctival swabs of the same patients exhibiting clinical conjunctivitis
Material and methods
Throughout the period from 2015 to 2022, we reviewed all clinically significant bronchial aspirates (≥105 CFU/mL) and positive conjunctival swabs obtained from PICU patients. These records were retrieved from the microbiology database, cross-referencing the data to identify patients who tested positive for both during the same clinical episode
Results
The median age of the patients was 5 months (interquartile range: 1-7). Among the cohort, twenty-one patients exhibited positivity in both bronchial aspirate and conjunctival swab samples, showcasing a microbial match in 85.71% of cases (18 out of 21). The most frequently isolated microorganisms were Haemophilus influenzae (55.6%), followed by Pseudomonas aeruginosa (14.3%), Klebsiella aerogenes (9.5%), and Escherichia coli, Stenotrophomonas maltophilia, and Enterobacter cloacae, each accounting for 4.8% of the isolates
Conclusions
Our study demonstrates a strong concordance between the isolated microorganisms from both samples in patients presenting clear symptoms of clinical conjunctivitis. These findings provide a basis for future prospective studies that may leverage conjunctival swabs as a predictive tool for identifying microorganisms involved in respiratory infections
Keywords: bronchial aspirate, conjunctival swab, respiratory bacterial superinfection
Abstract
Objetivos
Nuestro estudio observacional y retrospectivo tuvo como objetivo determinar la correlación entre las bacterias aisladas de aspirados bronquiales de pacientes de UCI pediátrica (UCIP) con infecciones respiratorias y las obtenidas de hisopos conjuntivales de los mismos pacientes que presentaban conjuntivitis clínica
Material y métodos
A lo largo del periodo comprendido entre 2015 y 2022, se revisaron todos los aspirados bronquiales clínicamente significativos (≥105 UFC/mL) y los hisopos conjuntivales positivos obtenidos de pacientes de UCIP. Estos registros se recuperaron de la base de datos de microbiología, cruzando los datos para identificar a los pacientes que dieron positivo en ambos durante el mismo episodio clínico
Resultados
La mediana de edad de los pacientes fue de 5 meses (rango intercuartílico: 1-7). Entre la cohorte, veintiún pacientes presentaron positividad tanto en las muestras de aspirado bronquial como en las de hisopo conjuntival, mostrando una coincidencia microbiana en el 85,71% de los casos (18 de 21). Los microorganismos más frecuentemente aislados fueron Haemophilus influenzae (55,6%), seguido de Pseudomonas aeruginosa (14,3%), Klebsiella aerogenes (9,5%) y Escherichia coli, Stenotrophomonas maltophilia y Enterobacter cloacae, cada uno de los cuales representó el 4,8% de los aislamientos
Conclusiones
Nuestro estudio demuestra una fuerte concordancia entre los microorganismos aislados de ambas muestras en pacientes que presentan síntomas claros de conjuntivitis clínica. Estos hallazgos proporcionan una base para futuros estudios pros-pectivos que podrían aprovechar los hisopos conjuntivales como herramienta predictiva para identificar microorganismos implicados en infecciones respiratorias
Palabras clave: aspirado bronquial, hisopo conjuntival, sobreinfección bac-teriana respiratoria
INTRODUCTION
Purulent conjunctivitis is a common infectious disease during childhood. The predominant pathogens of bacterial conjunctivitis in children are Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis [1]. Bacterial conjunctivitis is more common than the viral form in children. These microorganisms are normal inhabitants of the nasopharynx, especially in children, and can spread to other sites, including the eye, ear, and lower respiratory tract [2]
Respiratory syncytial virus (RSV) is a common cause of childhood pneumonia, and bacterial coinfections can affect clinical severity in those requiring Pediatric Intensive Care Unit (PICU). The prevalence of bacterial coinfections has been established in RSV-positive pneumonia [3]. Some studies have shown that co-detections are associated with longer need for mechanical ventilation and hospital stays. Almost one-third of the patients harbored bacterial pathogens [4], although other studies have detected a bacterial coinfection rate of 43.6% in hospitalized children using washed sputum culture [5]
Hospital-acquired respiratory infections are common in the intensive care unit (ICU). Hospital-acquired pneumonia (HAP), defined as occurring in patients with at least 48 hours of hospital admission, is highly prevalent in the ICU. The common pathogens associated with HAP include Enterobacterales, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. In 30% of cases, the infection is polymicrobial. Microbiological confirmation is a crucial step in the diagnosis of hospital respiratory infections. Routinely, diagnosis is based on qualitative or quantitative cultures of respiratory samples, and a pathogen is isolated from these samples and identified in about 70% of suspected cases [6]
The objective of this study is to ascertain whether a correlation exists between bacteria isolated from bronchial aspirates of patients infected in the respiratory tract and those isolated from conjunctival samples of these patients exhibiting clinically relevant conjunctivitis
MATERIAL AND METHODS
Throughout the study period, there were 7459 admissions to the PICU, with 1472 bronchial aspirates and 259 conjunctival swabs sent for microbiological culture. For this investigation, only positive and clinically significant (≥ 105CFU/mL) bronchial aspirates and conjunctival swabs were selected from the Microbiology department database, focusing on Pediatric Intensive Care Unit (PICU) patients between 2015 and 2022. Conjunctival swabs were exclusively obtained when clinical conjunctivitis was present and were not acquired as part of colonization studies. Respiratory isolates from patients were cross-referenced in the database to identify cases where a positive conjunctival swab was also present. The isolated microorganisms and their sensitivity patterns were subsequently compared. Patient medical records were scrutinized, with age and underlying infections documented. To be included in this retrospective study, patients had to have both samples collected during the same clinical episode
The study complies with the postulates of Helsinki´s Declaration. No human biological material or identifiable human data were used, therefore ethical approval was exempted
RESULTS
The median age of the patients was 5 months (range 0.5-22). Twenty-one patients had both positive bronchial aspirate and conjunctival swab results. However, in three out of these 21 cases, the microorganisms isolated from the bronchial aspirate and conjunctival swab did not match. The details of the isolated microorganisms and sampling dates for both types of samples are presented in Table 1. In the remaining 18 cases, the microorganisms isolated from the bronchial aspirate matched with those isolated in the conjunctival swab, and vice versa. The susceptibility profiles of the isolated microorganisms were also the same in these cases. The coincidence in the isolated microorganisms from both samples in this cohort was 85.71% (18 out of 21). In only three patients, the isolated microorganisms differed in both samples (14.29%). It is worth noting that in two out of these three cases, the samples were collected more than three weeks apart. The most frequently isolated microorganisms were H. influenzae (55.6%, 10 out of 21 isolates), followed by P. aeruginosa (14.3%, 3 out of 21 isolates), K. aerogenes (9.5%, 2 out of 21 isolates) and E.cloacae, S.maltophilia and E.coli with 4.8% of the isolates (1 out of 21 isolates). Notably, Pseudomonas aeruginosa and Enterobacterales isolates are associated with nosocomial respiratory infections, including ventilator-associated pneumonia or tracheobronchitis, and aspirative pneumonia. H. influenzae isolates are commonly associated with bacterial superinfections in patients with active viral infections
Table 1.
Age, samples and microorganisms isolated in each patient
| Patient* | Age | BAS microorganism isolated | Conjunctival microorganism isolated | Difference in days between the two samples | Antimicrobial resistance features | Respiratory infection |
|---|---|---|---|---|---|---|
| 1 | 1 month | H. influenzae | H. influenzae | 17 | Positive betalactamase. Same susceptibility pattern | RSV + bacterial superinfection |
| 2 | 3 months | P. aeruginosa | P. aeruginosa | Same day | Same susceptibility pattern | Hospital acquired respiratory infection |
| 3 | 6 months | K. pneumoniae | H. influenzae | 50 | Not the same microorganisms | Hospital acquired respiratory infection |
| 4 | 12 months | H. influenzae | H. influenzae | 1 | Negative betalactamase. Same susceptibility pattern | RSV + bacterial superinfection |
| 5 | 7 months | H. influenzae | H. influenzae | Same day | Negative betalactamase | Ventilator associated pneumonia (VAP) |
| 6 | 22 months | P. aeruginosa | H. influenzae | 28 | Not the same microorganisms | Aspirative pneumonia |
| 7 | 1 month | H. influenzae | H. influenzae | Same day | Negative betalactamase. Same susceptibility pattern | RSV + bacterial superinfection |
| 8 | 15 days | H. influenzae | H. influenzae | Same day | Negative betalactamase. Same susceptibility pattern | RSV + bacterial superinfection |
| 9 | 16 days | H. influenzae | H. influenzae | Same day | Negative betalactamase. Same susceptibility pattern | RSV+ bacterial superinfection |
| 10 | 2 months | H. influenzae | H. influenzae | 1 | Negative betalactamase. Same susceptibility pattern | Pertussis and bacterial superinfection |
| 11 | 15 days | H. influenzae | H. influenzae | 1 | Negative betalactamase. Same susceptibility pattern | Rhinovirus + bacterial superinfection |
| 12 | 5 months | E. coli | E. coli | 3 | Same susceptibility pattern | Tracheobronchitis associated to mechanical ventilation |
| 13 | 1 month | P. aeruginosa+ S. marcescens | S. aureus | Same day | Not the same microorganisms | RSV + bacterial superinfection |
| 14 | 6 months | K. aerogenes | K. aerogenes | 2 | Same susceptibility pattern | Ventilator associated pneumonia |
| 15 | 1 month | H. influenzae | H. influenzae. | Same day | Negative betalactamase. Same susceptibility pattern | Metapneumovirus + bacterial superinfection |
| 16 | 17 months | P. aeruginosa VIM | P. aeruginosa | 39 | Rectal colonization with P. aeruginosa VIM |
Nosocomial respiratory infection |
| 17 | 13 months | K. aerogenes | K. aerogenes | 2 | Same susceptibility pattern | Hospital acquired respiratory infection |
| 18 | 8 months | P. aeruginosa | P. aeruginosa | 10 | Same susceptibility pattern | Hospital acquired respiratory infection |
| 19 | 6 months | E. cloacae | E. cloacae | 7 | Same susceptibility pattern | Aspirative pneumonia |
| 20 | 6 months | S. maltophilia | S. maltophilia | 1 | Same susceptibility pattern | Hospital acquired respiratory infection |
| 21 | 3 months | H. influenzae | H. influenzae | Same day | Negative betalactamase. Same susceptibility pattern | RSV + bacterial superinfection |
The years have been avoided to ensure the anonymity of the samples and the patients. BAS: Bronchial aspirates, RSV: Respiratory syncitial virus
DISCUSSION
H. influenzae, M. catarrhalis, and S. pneumoniae are common colonizers of the oropharynx and can also cause bacterial conjunctivitis and otitis by spreading from the respiratory tract to the ear and conjunctiva [2]. Additionally, Enterobacterales, S. aureus, P. aeruginosa, and A. baumannii are pathogens causing HAP, the most common infection in the intensive care unit (ICU) [6]. These microorganisms can also cause hospital-acquired conjunctivitis. Although in our study we did not analyze viral conjunctival infections, viruses such as RSV and SARS-CoV-2 can cause conjunctivitis, albeit less frequently. For instance, in the study conducted by Wrotek et al. [7], focusing on the prevalence of complications in hospitalized children due to RSV, among 111 children examined, 12 also presented with conjunctivitis. Regarding COVID-19, a meta-analysis published by Nasiri et al. [8] revealed that among 7300 patients with COVID-19, the pooled prevalence of ocular manifestations was 11.03%, with conjunctivitis being the most prevalent ocular condition (88.8%)
In our observational study, we searched for patients admitted to the PICU who underwent sampling of bronchial aspirate and conjunctival swabs. We collected patients with positive cultures for significant microorganisms, as described above. We observed an 85.7% agreement between the micro-organisms isolated in both types of samples
Given the high degree of concordance between micro-organisms in both types of samples, we question whether the conjunctival swab could be useful in predicting which microorganism is causing the respiratory infection. There is currently no scientific evidence on the usefulness of the conjunctival swab for this purpose. However, there are manuscripts describing the usefulness of the methicillin-resistant S. aureus (MRSA) nares screening (MNS) to help limit empiric anti-MRSA antibiotic therapy in both children and adults [9,10]. The specificity and the negative predictive value of the MNS to predict a clinical MRSA infection were both 95.5% and it has proven to be useful for limiting unnecessary anti-MRSA therapy, making it a useful antimicrobial stewardship tool for hospitalized children [9]. Additionally, rectal colonization studies for the detection of carbapenemase-producing microorganisms appear to be useful in predicting sepsis caused by these microorganisms. Colonized patients are more likely to develop bacteremia due to these micro-organisms than those who are not colonized [11]. Therefore, a prospective study to corroborate our observation is mandatory. The conjunctival swab could be useful in predicting the microorganism that is causing the respiratory infection if similar results are obtained. This prospective study should be designed without the limitations of our retrospective study, including a small number of patients and patients with a conjunctival swab who had clinical conjunctivitis rather than being included as part of colonization studies. Therefore, conjunctival swabs should be taken as part of colonization studies without clinical symptoms to determine whether there is a coincidence with the microorganisms isolated in respiratory specimens
In conclusion, we observed a high coincidence between the microorganisms isolated in both types of samples. These results provide the basis for future prospective studies to evaluate the conjunctival swab as a tool for predicting the microorganisms that are causing respiratory infection. The usefulness of the conjunctival swab in the identification of microorganisms causing respiratory pathology in children should be tested. The conjunctival swab could have potential use as a tool for antimicrobial stewardship programs in patients with respiratory bacterial infection or superinfection for adjustment of antibiotic therapy in cases where bronchial aspirate or respiratory samples cannot be obtained
FUNDING
None to declare
CONFLICTS OF INTEREST
The authors declare no conflicts of interest.
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