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. 2023 Jan 9;23:14. doi: 10.1186/s12879-022-07942-x

Bacterial co-infection and antibiotic stewardship in patients with COVID-19: a systematic review and meta-analysis

Maria Calderon 1,, Grace Gysin 2,4, Akash Gujjar 4, Ashleigh McMaster 1, Lisa King 4, Daniel Comandé 3, Ewan Hunter 1, Brendan Payne 1,2
PMCID: PMC9828368  PMID: 36624396

Abstract

Introduction

Understanding the proportion of patients with COVID-19 who have respiratory bacterial co-infections and the responsible pathogens is important for managing COVID-19 effectively while ensuring responsible antibiotic use.

Objective

To estimate the frequency of bacterial co-infection in COVID-19 hospitalized patients and of antibiotic prescribing during the early pandemic period and to appraise the use of antibiotic stewardship criteria.

Methods

Systematic review and meta-analysis was performed using major databases up to May 5, 2021. We included studies that reported proportion/prevalence of bacterial co-infection in hospitalized COVID-19 patients and use of antibiotics. Where available, data on duration and type of antibiotics, adverse events, and any information about antibiotic stewardship policies were also collected.

Results

We retrieved 6,798 studies and included 85 studies with data from more than 30,000 patients. The overall prevalence of bacterial co-infection was 11% (95% CI 8% to 16%; 70 studies). When only confirmed bacterial co-infections were included the prevalence was 4% (95% CI 3% to 6%; 20 studies). Overall antibiotic use was 60% (95% CI 52% to 68%; 52 studies). Empirical antibiotic use rate was 62% (95% CI 55% to 69%; 11 studies). Few studies described criteria for stopping antibiotics.

Conclusion

There is currently insufficient evidence to support widespread empirical use of antibiotics in most hospitalised patients with COVID-19, as the overall proportion of bacterial co-infection is low. Furthermore, as the use of antibiotics during the study period appears to have been largely empirical, clinical guidelines to promote and support more targeted administration of antibiotics in patients admitted to hospital with COVID-19 are required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07942-x.

Keywords: Bacterial co-infection, COVID-19, Antibiotic stewardship

Introduction

The COVID-19 pandemic has impacted health systems worldwide, with SARS-CoV-2 infection being implicated in more than 6 million deaths to date [1, 2]. Some clinical guidelines have recommended empirical antibiotic therapy to treat suspected bacterial respiratory co-infection in COVID-19 patients, and tools to support and promote antibiotic stewardship in this population are therefore needed [3, 4].

Distinguishing between viral pneumonia and bacterial co-infection at presentation and during the course of COVID-19 disease can be challenging due to various similarities, including characteristically high inflammatory markers and the frequent presence of pulmonary infiltrates on chest X-ray or computed tomography (CT) imaging [5]. There is therefore potential for considerable overuse of antibiotics in the management of COVID-19 pneumonia, with the attendant risk of an increase in the prevalence of antimicrobial resistance in affected populations. Given the current pandemic context, the implications of this for public health and health systems are likely to be considerable. Clinical guidelines to support the most effective treatment for patients while promoting the responsible use of antibiotics should be informed by an understanding of what proportion of patients admitted to hospital with COVID-19 pneumonia have confirmed acute respiratory bacterial co-infection and of the commonly associated pathogens.

We performed a systematic review to estimate the frequency of confirmed bacterial co-infection in patients admitted to hospital with COVID-19 pneumonitis, the frequency of empirical antibiotic use in this patient group, and to identify any antibiotic stewardship criteria that have been used during the COVID-19 pandemic to date.

Methods

We registered the review protocol at the PROSPERO international prospective register of systematic reviews (CRD 42020181215). We followed the method for the elaboration of systematic reviews recommended by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [6]. Although the PRISMA statement is mainly used in systematic reviews of intervention studies, several domains are also applicable to systematic reviews of prevalence [7]. As PRISMA is the most widely used tool for the reporting of systematic reviews, we used it in the present work. The PRISMA checklist for this study is presented in Additional file 1: Material S1.

Selection criteria and search strategy

We included studies with patients admitted to a hospital setting with suspected lower respiratory tract infection (LRTI) and with SARS-CoV-2 infection confirmed by PCR. Due to the high number of publications, we only included original studies with at least 10 participants and which provided enough information to appraise the methods used. Randomised and non-randomised studies that presented at least one of the following outcomes of interest were included: (a) prevalence of bacterial co-infection in patients with confirmed SARS-CoV-2 infection; (b) the proportion of patients with confirmed SARS-CoV-2 infection that were commenced on empirical antibiotic treatment. Where available, we collected information on the duration and type of antibiotics and on any related adverse events. In cases receiving specific treatment for COVID-19 as part of a clinical trial, we only included standard-of-care comparator arms. We excluded antibiotic use for indications other than bacterial LRTI (e.g., azithromycin used as specific therapy for SARS-CoV-2 at the beginning of the pandemic was excluded). In order for our findings to be readily generalisable, we excluded pregnant women and patients with chronic immunosuppressive conditions, these being specific populations with different and increased infection risk profiles. We also excluded studies that mentioned bacterial co-infection rates but did not provide clinical details (e.g., cost-effectiveness analyses or modelling studies). Given that many authors provided only limited descriptions of antibiotic use, we performed two sub-analyses: one of studies clearly stating bacterial co-infection confirmed by cultures taken less than 48 h from point of admission, and another including only studies that clearly stated the empirical use of antibiotics. In the latter, we also describe any antibiotic stewardship strategies.

We also performed sub-group analyses of any available data on critically ill patients, defined as those patients identified by study authors as requiring admission to high-dependency or intensive care. Definitions of bacterial co-infection provided by study authors were accepted.

We searched the following databases up to May 5, 2021: Pubmed, LILACS, Embase, Web of Science and Cochrane Library. Our search strategy is given in Additional file 1: Material S2. Searches were limited to papers written in English, German, Russian, French, Spanish, or Portuguese. Reference lists from all included articles were also scrutinised to identify additional studies of potential interest.

Screening and data extraction

We used a two-stage screening process to identify publications that would be eligible for inclusion: title and abstract, followed by full text review. Any original manuscripts referenced by systematic reviews but not identified by the initial search were also included if they were eligible. All publications were then screened in duplicate and independently by reviewers working in pairs (MC, GG, AG, LK, AM, DC); any disagreements in screening were resolved by a third, independent reviewer (EH or BP). Data from eligible papers were extracted by two independent reviewers into separate, piloted and standardised Microsoft Excel spreadsheets; the third reviewer was then asked to resolve any discrepancies and a single consensus dataset was produced after discussion.

Data analysis

We present the results of all included studies according to the selected outcomes of interest. We analysed our data using a proportion meta-analysis. We applied an arc-sine transformation to stabilise the variance of proportions (Freeman-Tukey variant of the arc-sine square-root of transformed proportions method), where y = arcsine[√(r/(n + 1))] + arcsine[√(r/(n + 1)/(n + 1)], with a variance of 1/(n + 1), with n being the population size. The pooled proportion was calculated as the back-transformation of the weighted mean of the transformed proportions, using inverse arcsine variance weights for the fixed and random effects models. Where heterogeneity between studies was found we applied DerSimonian-Laird weights for the random effects model. We calculated the I2 statistic as a measure of the overall variation in the proportion that was attributable to between-study heterogeneity. STATA 17.0 was used for all analyses.

Study quality assessment

To describe the quality of the prevalence data extracted from the included studies, we used The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for cross-sectional/prevalence data [8]. This is a tool that has been developed acknowledging that prevalence data can come from different study designs, as in our case.

Quality of included studies were assessed independently by two investigators; any disagreements were resolved by a third senior investigator.

Results

Database searches identified 6798 studies. After removing duplicates and reviewing the secondary reference lists from included papers we screened a total of 4,132 studies for title and abstract. Of these, 162 (3.9%) went to full text review and 85 (2.1%) were selected for data extraction (Fig. 1).

Fig. 1.

Fig. 1

Flowchart of included studies. Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med 6(7): e1000097. https://doi.org/10.1371/journal.pmed1000097. For more information, visit www.prisma-statement.org

The independent assessment of the quality of included papers is described in the Additional file 1: Material S3. Using the selected quality assessment tool, we identified that the majority of included studies had appropriate samples for their specific objectives, adequate description of participants and diagnosis of condition.

Data derived from a total of 31,123 individuals were included for analysis. The study designs of all included papers comprised case series, cohorts, registries, and clinical trials. The majority of papers were from China (29, 34.1%) and USA (16, 18.8%). The main characteristics of the included studies are shown in Table 1. Full references of included studies are provided in Additional file 1: Material S4.

Table 1.

Main characteristics of included studies

Author, Year (Ref) Country Centre(s) Study period N Age (years)
Mean/SD(range)
or *Median/IQR
Female (%) Ventilatory support ITU admission Mortality (%)
NIV MV
Alharty et al., 2020 (1) SaudiArabia Single 20/03/20–31/05/20 352 50.6/13.3 45/352 (12.8%) 0/352 (0%) 352/352 (100%) 352/352 (100%) 113/352 (32.1%)
Allou et al., 2021 (2) France Single 01/03/20–30/04/20 36 66/56–77* 11/36 (30.5%) 3/36 (8.3%) 2/36(5.6%) 10/36 (27.8%) 0/36 (0%)
Amit et al., 2020 (3) Israel Multi 05/03/20–27/04/20 156 72/60–82* 48/156 (30.8%) 39/156 (25%) 93/156(59.7%) 156/156 (100%) 87/156 (55.8%)
Asmarawati et al., 2021 (4) Indonesia Single 14/03/20–30/09/20 218 52.4/14.4 98/218 (44.9%) NR 23/218 (10.5%) 52/218 (23.8%) 21/218 (9.6%)
Ayding Bahat et al., 2020 (5) Turkey Single 11/03/20–24/04/20 25 60.5/15 15/25 (60%) NR NR 8/25(32%) 5/25(20%)
Balena et al., 2020 (6) Italy Single 01/03/20–15/06/20 148 80/72–86* 83/148 (66%) 31/148 (21%) 4/148 (4%) NR 34/128 (23%)
Baraboutis et al., 2020 (7) Greece Single 16/03/20–12/04/20 49 63/20–95* 19/49 (38.8%) NR 8/49 (16.3%) NR 6/49 (12.2%)
Bardi et al., 2021 (8) Spain Single 01/03/20–01/06/20 140 61/57–67* 32/140 (23%) NR 134/140 (96%) 140/140 (100%) 51/140 (36%)
Barrasa et al., 2020 (9) Spain Single 04/03/20–31/03/20 48 67/53–74* 21/48 (43.8%) 0/48 (0%) 45/48 (94%) 48/48(100%) 16/48 (36%)
Barry et al., 2020 (10) Saudi Single 22/03/20–31/05/20 99 44.0/(19–87) 33/99 (33.3%) 9/99 (9.1%) 13/99 (13.1%) 22/99(22.2%) 12/99 (12%)
Basakaran et al., 2021 (11) UK Multi 21/02/20–01/05/20 254 59/49–69* 90/254 (35.4%) NR 151/254 (59.5%) 254/254 (100%) 2/254 (0.8%)
Bhatt et al., 2021 (12) USA Multi 01/03/20–07/05/20 375 63.2/16.2 146/375 (38.9%) 7/375 (1.8%) 17/375 (4.5%) 175/375 (46.7%) 149/375 (39.7%)
Buckner et al., 2020 (13) USA Multi 02/03/20–26/03/20 105 69/23–97* 52/105 (49.5%) 1/105 (1.0%) 17/105 (16.2%) 51/105 (48.6%) 35/105(33.3%)
Chen et al., 2020 (14) China Single 01/01/20–10/02/20 203 54/(20–91) 95/203 (46.8%) NR 39/203 (19.2%) 39/203 (19.2%) 26/203 (12.8%)
Chen et al., 2021 (15) China Single 11/01/20–31/03/20 408 48/34–60* 212/408 (51.9%) NR NR NR 3/408 (0.7%)
Cheng et al., 2020 (16) China Single 08/01/20–08/05/20 147 36/24–54* 62/147 (42.1%) NR NR 3/147 (2%) 0/147 (0%)
Chengy et al., 2020 (17) China Single 01/01/20–18/03/20 62 61/49.3–67.5* 44/62 (70.9%) NR NR NR 0/62 (0%)
Chong et al., 2021 (18) USA Single 8/03/20–22/06/20 244 63/51–75* 96/244 (40.6%) 18/244 (7.4%) 71/244 (29.1%) 118/244 (48.4%) NR
Choubey et al., 2021 (19) UK Single 01/03/20–31/05/20 209 NR NR NR NR NR NR
Contou et al., 2020 (20) France Single 01/03/20–30/02/20 92 NR/(55–70) 19/92 (20.6%) NR 83/92 (90%) 92/92 (100%) 45/92 (49%)
D’Onofrio et al., 2020 (21) Belgium Single 12/03/20–12/04/20 110 73/60–82* 62/110 (56.4%) NE NE 29/110(26.4%) 34/110 (30.9%)
Desai et al., 2020 (22) Italy Single 01/04/20–30/09/20 536 62.9/12.8 5268/536 (50%) NR NR NR 116/536 (21.6%)
Dolci et al., 2020 (23) Italy Single 01/02/20–31/03/20 83 61/(49–67) 11/83 (13.3%) NR NR NR 44/83 (53.0%)
Ekadashi et al., 2021 (24) India Single 23/03/20–23/08/20 158 NR NR NR NR NR NR
Elabbadi et al., 2021 (25) France Single 01/02/20–31/05/20 101 61/53–69* 22/101 (10.8%) NR 83/101(82.2%) 101/101 (100%) 21/101 (20.8%)
Falcone et al., 2021 (26) Italy Single 04/03/20–30/04/20 315 NR 105/315 (33.3%) 68/315 (21.6%) 55/315 (17.5%) 85/315 (26.9%) 70/315 (22.2%)
Fan et al., 2021 (27) China Single 01/01/20–31/01/20 55 46.46/14.41 25/55 (45.5%) NR NR NR 0/55 (0%)
Garcia-Vidal et al., 2021 (28) Spain Single 01/02/20–30/04/20 989 62/48–74* 437/989 (44.2%) NR NR 146/989 (14.8%) 99/989 (10.0%)
Gayam et al., 2020 (29) USA Single 01/03/20–30/04/20 350 NR NR NR NR NR NR
Goncalves et al., 2021 (30) USA Single 01/03/20–20/04/20 242 66/14.75 119/242 (49.2%) NR NR NR 52/242 (22.7%)
Guan et al., 2020 (31) China Single NR 61 56.8/15.1 NR NR NR NR 1/61 (1.6%)
He et al., 2020 (32) China Single 01/02/20–28/02/20 192 45/NR 93/192(48.4%) NR NR NR 5/192 (2.6%)
He et al., 2021 (33) China Multi 01/01/20–28/02/20 905 47/35–57* 463/905 (51.2%) NR NR NR 57/905 (6.2%)
Huang et al., 2020(34) China Single 16/12/19–02/01/20 41 49.0/41.0–58.0* 11/41 (26.8%) 10/41 (24%) 2/41(5%) NR 6/41(14.6%)
Huang et al., 2020 (34) China Single 16/12/19–02/01/20 13 49/41–61* 2/13 (15%) 8/13 (62%) 2/13 (15%) 13/13 (100%) 5/13(38%)
Huang et al., 2021 (35) USA Single 01/03/20–31/05/20 41 66.6/19.1 21/41(51.2%) 26/41(63.4%) 15/41(37%) 15/41(36.6%) 15/41(36.6%)
Hughes et al., 2020 (36) UK Multi 20/02/20–20/04/20 836 69/55–81* 317/836 (37.9%) NR NR NR NR
Humières et al., 2021(37) France Multi 29/01/20–31/05/20 197 59/(50–68) 48/197 (24.8%) NR 129/197(67%) 197/197 (100%) 71/197 (26.0%)
Karaba et al., 2021 (38) USA Multi 01/03/20–31/05/20 1016 62/48–74* 473/1016(46.5%) NR NR NR NR
Karami et al., 2021 (39) Netherlands Multi 01/03/20–31/05/20 925 70/59–77* 334/925 (36.1%) NR NR NR 214/925 (23.1%)
Kimming et al., 2020(40) USA Single 01/03/20–27/04/20 111 NR 49/111 (44.1%) NR NR NR 30/111 (27%)
Kolenda et al., 2020 (41) France Multi 01/03/20–15/04/20 99 NR NR NR NR NR NR
Lardaro et al., 2021 (42) USA Multi 01/03/20–30/04/20 542 64.8/16.5 273/542 (50.4%) NR 162/542 (29.9%) 86/542 (15.9%) 78/542 (14.4%)
Li et al., 2020 (43) China Single 20/01/20–14/02/20 225 50.0/14.0 105/225 (46.7%) NR NR NR 2/225 (0.9%)
Li et al., 2020 (44) China Single 27/01/20–17/03/20 1495 NR NR NR NR NR NR
Liu et al., 2020 (45) China Single 18/01/20–12/03/20 140 65.5/54.3–73.0* 91/140 (65.0%) NR NR NR NR
Liu et al., 2021 (46) China Single 01/01/20–28/02/20 53 38/28–47* 27/53 (50.9%) 32/53 (63.4%) 1/53(1.9%) 1/53 (1.9%) 0/53 (0%)
Liu et al., 2021 (47) China Single 26/01/20–18/03/20 1123 61/50–69* 563/1123 (50.1%) NR NR NR 111/1123 (9.9%)
Mady et al., 2020 (48) Saudi Arabia Single 12/08/20–12/09/20 61 51/42.5–58.8* 7/61 (11.5%) 32/61 (52.5%) 29/61 (47.5%) 61/61 (100%) 19/61 (31.1%)
Mahmoudi et al., 2020 (49) Iran Single 17/02/20–20/10/20 340 NR NR NR NR NR NR
Mason et al., 2021 (50) UK Multi 01/03/20–31/05/20 800 NR/(18–100) 310/800 (38.7%) NR NR NR NR
M. Movahed et al., 2021 (51) Iran Single 22/02/20–19/04/20 854 55.6/17.63 382/854 (44.7%) NR NR 183/854(21/4%) 119/854 (13.9%)
Nassir et al., 2021 (52) Pakistan Single 01/02/20–30/06/20 100 58/49–57* 11/100 (11%) NR 35/100 (35%) 79/100 (79%) 30/100 (30%)
Nebreda et al., 2020 (53) Spain Single 08/03/20–31/05/20 712 NR NR NR NR NR NR
Pulia et al., 2021 (54) USA Multi 15/03/20–18/05/20 73 NR 38/73 (52.1%) NR 8/73 (10.9%) NR NR
Quartuccio et al., 2020(55) Italy Single 01/02/20–30/04/20 69 56.2/14.2 25/69 (36.2%) 0/69 (0%) 0/69 (0%) 0/69 (0%) 0/69 (0%)
Richardson et al., 2020 (56) USAe Multi 01/03/20–04/04/20 5700 63.0/52.0–75.0 2263/5700 (39.7%) NR 320/5700 (5.6%) 373/5700 (6.5%) 553/5700 (9.7%)
Rippa et al., 2021 (57) Italy Single 25/02/20– 6/04/20 731 64/(55–76) 235/731 (32.1%) NR NR 45/731(6.1%) NR
Rothe et al. 2020 (58) Germany Single 01/02/20–30/04/20 140 63.5/(17–99) 50/140 (35.7%) NR 41/14 0(29.3%) 56/140 (40%) 18/140 (12.8%)
Seaton et al., 2020 (59) Scotland Multi 20/04/20–30/04/20 531 72/61–82* 257/531 (48.4%) NR NR 110/531 (20.7%) NR
Shah et al., 2020 (60) USA Single 03/02/20–31/03/20 33 63/50–75* 12/33 (36.4%) 0/33(0%) 6/11 (55%) 11/26 (42%) 1/26 (4%)
Shao et al., 2020 (61) China Multi 23/01/20–23/03/20 126 NR/(19–91) 58/126 (46.0%) NR NR NR 1/126 (0.1%)
Sharifipour et al., 2020 (62) Iran Multi NR 19 67/4.6 8/19 (42.1%) NR NR 19/19(100%) 18/19(94.7%)
Silva et al., 2021 (63) Brazil Single 01/05/20–30/11/20 212 NR 86/212 (40.5%) NR NR 212/212(100%) 107/212(52.9%)
Singh et al., 2021 (64) USA Single 16/03/20–01/08/20 4259 45.2/20–43* 2513/4259 (55.5%) NR NR NR NR
Soogard et al., 2021 (65) Switzerland Single 25/02/20–31/05/20 162 64.4/50.4–74.2* 63/162(38.9%) NR 34/162(20.9%) 41/162(25.3%) 17/162(10.5%)
Staub et al., 2021 (66) USA Single 01/03/20–15/05/20 131 56/17.4 53/131(39.7%) NR NR NR 13/131 (9.9%)
Stevens et al., 2021 (67) USA Single 01/03/20–28/04/20 346 45/18 176/346 (51%) NR NR 0/346 (0%) 0/346 (0%)
Tang et al., 2021 (68) China Single 28/01/20–15/03/20 78 47.7/17.2 37/78(47.4%) NR NR 8/78 (10.3%) NR
Thelen et al., 2021 (69) Netherlands Multi 28/02/20–02/06/20 678 70/58–78* 235/678 (34.7%) NR NR 6/678 (0.9%) 191/678 (28.3%)
Townsend et al., 2020 (70) Ireland Multi 01/03/20–31/04/20 117 NR 43/117 (36.8%) NR NR 34/117 (29.1%) 17/117 (14.5%)
Vanhomwegen et al., 2021 (71) Belgium Single 03/03/20–02/05/20 66 61/49–71* 25/66 (38%) NR NR 66/66 (100%) 20/66 (30.3%)
Vaughn et al., 2021 (72) USA Multi 01/03/20–01/06/20 1705 64.7/53.0–76.7* 820/1705 (48.1%) 13/1705 (0.8%) 116 /1705 (6.8%) NR 325/1705 (19.1%)
Wan et al., 2020 (73) China Single 23/01/20–08/02/20 135 47.0/36.0–55.0* 63/135 (46/7%) 34/135 (19.4%) 1/135 (0.7%) 40/135 (29.6%) 1/135 (0.7%)
Wan et al., 2020 (73) China Single 23/01/20–08/02/20 40 56.0/52.0–73.0* 19/40 (47.5%) 27/40 (67.5%) 1/40 (2.5%) 40/40 1/40 (2.5%)
Wang et al., 2020 (74) China Single 29/01/20–10/02/20 28 68.6/9.0 (53–82) 7/28 (25%) 11/28 (39.3%) 7/28 (25%) 14/28 (50%) 12/28 (42.9%)
Wang et al., 2020 (74) China Single 29/01/20–10/02/20 14 71.4/7.9 4/14(71.4%) 11/14 (79.6%) 7/14 (50%) 14/14 (100%) 12/14 (85.7%)
Wang et al., 2020 (75) China Single 01/01/20–06/02/20 339 69.0/65.0–76.0* 173/339(51.0%) NR NR 65/339 (19.2%) 65/339 (19.2%)
Wang et al., 2021 (76) UK Multi 01/03/20–30/04/20 1396 67.4/16.2 NR NR NR 226/1396 (16.2%) 420/1396 (30.1%)
Xu et al., 2021 (77) China Single Up to 12/03/20 62 56.5/45.3–74.8* 27/62 (44%) 24/62 (45%) 15/62 (24%) 62/62 (100%) 7/62 (11.3%)
Yang et al., 2020 (78) China Single 05/01/20–22/02/20 251 NR 128/251 (51.0%) NR NR NR 21/251 (8.4%)
Zhang et al., 2020 (79) China Single 02/01/20–10/02/20 221 55.0/39.0–66.5* 113/221 (51.1%) 26/221 (12.2%) 16/221 (7.2%) NR 12/221 (5.4%)
Zhang et al., 2020 (80) China Single 16/01/20–03/02/20 140 57.0/25.0–87.0* 69/140 (49.3%) NR NR NR NR
Zhang et al., 2020 (81) China Single 22/01/20–30/04/20 38 64.7/13.7 6/38 (15.8%) NR NR NR NR
Zhang et al., 2020 (82) China Single 10/12/19–20/02/20 134 60.8/12.9 47/134 (35.1%) 91/134 (67.9%) 79/134 (58.9%) 134/134 (100%) 101/134 (75.4%)
Zhang et al., 2021 (83) China Single 01/01/20–28/02/20 91 74.9/68–82* 52/91 (57.1%) 3/91 (3.3%) 11/91 (12.1%) NR 5/91 (55.6%)
Zhang et al., 2020 (84) China Single 01/01/20–31/03/20 365 46.8/15.5 189/365(51.8%) NR NR NR 2/365(0.5%)
Zhao et al., 2020 (85) China Single 01/01/20–28/02/20 1000 61/46–70* 534/1000 (53.4%) 147/1000 (14.7%) 43/1000 (4.3%) 63/1000 (6.3%) 119/1000 (11.9%)

N: number. NR: not reported. IQR: interquartile range. SD: standard deviation, SOCa: standard of care

NIV: Non-invasive ventilation, MV: mechanical ventilation, ITU: intensive treatment unit

Full list of references are in Additional file 1: Material S4

Bacterial co-infection prevalence

We included 70 studies that reported on the prevalence of bacterial co-infection (including critically ill patients and not critically ill patients) (Table 2). Meta-analysis of these studies showed an overall prevalence of bacterial co-infection of 12% (51 studies, 95% CI 8% to 16%; I2 99.2%) (Fig. 2A); subgroup meta-analysis of critically ill patients showed a prevalence of 23% (21 studies, 95% CI 16 to 31%; I2 94.6%) (Fig. 2B).

Table 2.

Studies reporting bacterial co-infection in patients with COVID-19

Study n N Patient group Definition of bacterial co-infection Microorganism identified
Alharty et al., 2020 (1) 25 352 Critically ill Nosocomial acquired bacterial infection by culture (15 VAP + 10 CLI) Most common: Acinetobacter baumannii, and MRSA
Allou et al., 202 1(2) 3 36 Not specific: General including critically ill Co-infections. Method: Measured by multiplex PCR, pneumococcal and Legionella urinary antigen tests, cytobacteriological examination of sputum cultures, and serology of atypical respiratory pathogens

Branhamella catarrhalis = 1

Streptococcus pneumoniae and Haemophilus influenza = 1

MSSA = 1

Amit et al., 2020 (3) 27 156 Critically ill Secondary infection. Method: NR NR
Asmarawati et al., 2021 (4) 43 218 Moderate to Critically ill

Expressed as co-infection and secondary infections

Method: Blood and sputum and urine cultures

Most common presented

Blood culture: ESBL-producing Klebsiella pneumoniae, Pseudomonas spp.

Sputum: Acinetobacter baumannii, Klebsiella pneumoniae

Ayding Bahat et al., 2020 (5) 7 25 Haemodialysis Secondary infection. Method: NR NR
Balena et al., 2020 (6) 32 128 Elderly At least one secondary infection by authors. Method: NR NR
Baraboutis et al., 2020 (7) 0 49 Overall Blood and sputum cultures, urine pneumococcal and legionella antigen NR
Bardi et al., 2021 (8) 57 140 Not specific: General

Nosocomial infection (30 LRTI, 21 VAP, 28 BSI, 24 CRBSI, 7 UTI, 2 soft tissue infections)

Method: Cultures

Most common presented:

BSI: Enterococcus faecium (43%), followed by Enterococcus faecalis (21%)

CRBSI: coagulase-negative staphylococci (54%), Enterococus faecium (17%)

VAP: Staphylococcus aureus (24%)

Barrasa et al., 2020 (9) 3 48 Critically ill NR NR
Barry et al., 2020 (10) 9 99 Not specific: General including critically ill Method: Sputum culture and blood culture

Sputum culture: Stenotrophomonas maltophilia = 1, Klebsiella pneumoniae = 1

Blood culture: Staphylococcus epidermidis = 4; Enterococcus faecalis = 1; Corynebacterium amycolatum = 1; Bacillus pumilus = 1

Basakaran et al., 2021 (11)* 14 254 Critically ill Method: Standard culture (blood, sputum, tracheal-aspirate, bronchoalveolar lavage, urine) and validated culture-independent tests such as respiratory viral PCR and urinary antigens The most common potential co-pathogens identified were Gram negative bacteria, including Klebsiella spp. (23) and Escherichia coli (20)
Bhatt et al., 2021 (12) 128 375 Not specific: General including critically ill Method: Blood culture

Most common: Staphylococcus epidermidis, MSSA

Enterococcus faecalis, Escherichia coli, MRSA

Chen et al., 2020 (14) 2 203 Elderly Method: PCR Mycoplasma pneumoniae = 2
Chen et al., 2021 (15)* 25 408 Not specific: General Method: Blood culture, respiratory culture, serology, PCR and metagenomic next-generation sequencing

Mycoplasma pneumoniae = 3

Haemophilus influenzae = 6

Klebsiella pneumoniae = 2

Streptococcus pneumoniae = 1

Staphylococcus aureus + Streptococcus pneumoniae = 1

Staphilococcus aureus + Haemophilus influenzae = 1

MRSA + Haemophilis influenzae + Streptococcus pneumoniae = 1

Cheng et al., 2020 (16)* 12 147 Not specific: General including critically ill Method: Blood culture, respiratory culture, serology, PCR MSSA + Haemophilus influenzae = 1, MSSA = 8, Pseudomonas aeruginosa = 1, Haemophilus influenza = 2
Chengy et al., 2020 (17) 43 64 Not specific: General Method: Positive culture or clinical/laboratory suspicion NR
Chong et al., 2021 (18)* 13 244 Not specific: General including critically ill Method: Respiratory tract cultures ± concurrent positive blood culture

Haemophilus influenzae = 3, Klebsiella penumoniae = 3

Pseudomona aeruginosa + MSSA = 3, Corynebacterium striatum = 2

MRSA = 2

Others = Citrobacter freundii, Moraxella catarrhalis, Enterobacter aerogenes, Klebsiella aerogenes (respiratory culture)

Choubey et al., 2021 (19) 8 209 Not specific: General Method: Mycoplasma pneumoniae serology Mycoplasma pneumoniae = 8
Contou et al., 2020 (20)* 26 92 Critically ill Method: Cultures, PCR, antigen Most common: MSSA (10/32, 31%), Haemophilus influenzae (7/32, 22%), Streptococcus pneumoniae (6/32, 19%), Enterobacteriaceae spp. (5/32, 16%)
D’Onofrio et al., 2020 (21)* 3 10 Not specific: General including critically ill Method: Cultures, PCR, antigen Staphylococus hominis = 1, Corynebacterium aurimucosum = 1, Streptococcus pyogenes = 1
Desai et al., 2020 (22) 68 536 Not specific: General Method: Streptococcus pneumoniae urinary antigen (u-Ag) Streptococcus pneumoniae = 68
Dolci et al., 2020 (23) 33 83 Not specific: General Definition/Method: positivity of blood cultures and/or of cultures of lower respiratory tract specimens (bronchoalveolar lavage fluid or bronchial aspirate) NR
Ekadashi et al., 2021 (24) 15 158 Not specific: General including critically ill Blood culture Coagulase negative Staphylococcus spp. (11, 73.3%)
Elabbadi et al., 2021 (25)* 20 101 Critically ill Method: Culture (respiratory, blood), urinary antigen Gram positive = 11, Gram negative = 13
Falcone et al., 2021 (26)* 69 315 Not specific: General including critically ill

Definition: Hospital acquired > 48 h

Method: Blood culture

Enterobacterales (44.9%), non-fermenting Gram negative bacilli (15.6%), Gram positive bacteria (15.6%)**
Garcia-Vidal., 2021 (28)* 21 989 Not specific: General including critically ill Method: Culture (respiratory, blood), urinary antigen. < 24 h

Streptococcus pneumoniae + Moraxella catarrhalis = 1

Staphylococcus aureus + Haemophilus influenzae = 1

Gayam et al., 2020 (29)* 6 350 Not specific: General Method: Mycoplasma PCR Mycoplasma pneumoniae = 6
Goncalves et al., 2021 (30)* 46 242 Not specific: General Definition/Method: Clinical features and positive blood, sputum, urine, or tissue culture results NR
Guan et al., 2020 (31) 5 61 Not specific: General Method: Blood and respiratory culture

Gram negative bacteria = 2

Gram negative + Gram positive bacteria = 3

He et al., 2020 (32) 125 192 Not specific: General Method: PCR Streptococcus pneumoniae = 14, Bordetella pertussis = 19, Streptococcus.pyogenes = 3, Staphylococcus aureus = 1, Mycobacterium tuberculosis = 7, Neisseria meningitidis = 7, Haemophilus influenzae = 17, Pseudomonas aeruginosa = 57
He et al., 2021 (33)* 86 905 Not specific: General Definition/Method: Clinical diagnosis based on clinical findings combined with laboratory and radiology findings NR
Huang et al., 2020 (34) 4 41 Not specific: General including critically ill Definition/Method: Positive culture of a new pathogen from a lower respiratory tract specimen NR
Huang et al., 2020 (34) 4 13 Critically illl Definition/Method: Positive culture of a new pathogen from a lower respiratory tract specimen NR
Huang et al., 2021 (35) 7 41 Critically illl

Method: Culture

NB: Majority of infections were considered nosocomial

NR
Hughes et al., 2020 (36) 21 643 Not specific: General Method: Blood culture, respiratory culture, pneumococcal antigen, Legionella antigen

CRBSI: Klebsiella pneumoniae = 1, VAP: Enterobacter cloacae = 1

CLI: Enterococcus spp. = 2, Pseudomonas aeruginosa = 1

Humières et al., 2021 (37) 88 197 Critically ill Definition/Method: Nosocomial infections. Clinical features and positive blood, sputum, urine, or tissue culture results NR
Karaba et al., 2021 (38)* 12 1016 Not specific: General Definition/Method: Clinical, laboratory, and radiographic criteria plus microbiologic diagnosis

Only confirmed:

Sputum culture: MSSA = 1

Karami et al., 2021 (39)* 12 925 Not specific: General Method: Respiratory cultures, pneumococcal antigen, Legionella antigen Most common: Staphylococcus.aureus, Escherichia coli, Stenotrophomonas maltophilia
Kimming et al., 2020 (40) 16 58 Critically ill. Soc

Definition: Including hospital acquired infections

Method: Cultures

NR
Kolenda et al., 2020 (41) 15 99 Critically ill Method: PCR and culture Most common: Staphylococcus.aureus,and Haemophilus influenzae
Lardaro et al., 2021 (42)* 6 542 Not specific: General including critically ill Method: Blood cultures NR
Li et al., 2020 (a) (44) 102 1495 Not specific: General Method: Cultures Acinetobacter baumannii (57/159, 35.8%), Klebsiella. pneumoniae (49/159, 30.8%,), Stenotrophomonas maltophilia (10/159, 6.3%)
Mady et al., 2020 (48) 11 61 Critically ill

Definition: Including hospital acquired infections

Method: Blood and respiratory cultures

Blood culture: Staphylococcus aureus = NR, Vancomycin resistant enterococcus (sensitive to tigecycline) = NR, Acinetobacter baumannii = NR

VAP: Pseudomonas spp. = 3, Acinetobacter baumannii = 3

Mahmoudi et al., 2020 (49) 36 340 Not specific: General Method: Endotracheal and blood cultures Klebsiella spp. (11, 25.59%), MSSA (9, 20.93%), Escherichia.coli (7, 16.28%), MRSA (6, 13.95%), Enterobacter spp. (5, 11.63%), Streptococcus pneumoniae (1, 2.32%), Pseudomonas aeruginosa (4, 9.30%)
Mason et al., 2021 (50) 40 800 Not specific: General Method: Sputum, blood, urine ag, Mycoplasma PCR NR
Nassir et al., 2021 (52) 50 100 Not specific: General including critically ill Method: Blood and respiratory cultures NR
Nebreda et al., 2020 (53)* 39* 712 Not specific: General including critically ill Method: Blood and respiratory culture Most common: Gram negative bacilli (59%), Escherichia.coli (47%) Enterococcus faecalis (21%), Streptococcus pneumoniae (33%) and Staphylococcus aureus (33%)
Quartuccio et al., 2020 (55) 0 69 SOCa Method: Respiratory and blood cultures NR
Richardson et al., 2020 (56) 3 5700 Not specific: General including critically ill Method: PCR for extensive respiratory panel including atypical bacteria

Chlamydia pneumoniae = 2

Mycoplasma pneumoniae = 1

Rippa et al., 2021 (57) 68 731 Not specific: General including critically ill Definition: Clearly stated as secondary co-infection within > 48 h of admission

BSIs: Gram positive bacteria (76/106, 71.7%), of which 53/76, 69.7% were coagulase-negative staphylococci

BSIs: Gram negative bacteria (23/106, 21.7%), of which 7/23, 30.4% Acinetobacter baumannii, and 5/23, 21.7% were Escherichia coli

LRTIs: Gram-negative bacteria (14/26, 53.8%)

Rothe et al., 2020 (58) 10 118 Not specific: General including critically ill Method: Blood cultures, Legionella pneumophila and Streptococcus pneumoniae urinary antigens Only blood cultures were positive (n = 10)
Shah et al., 2020 (60) 1 33 Overall Method: Blood and respiratory cultures

Blood culture: Enterococcus faecium = 1

Respiratory culture: Stenotrophomonas maltophilia = 1

Shao et al., 2020 (61) 56 126 Not specific: General including critically ill NR NR
Sharifipour et al., 2020 (62) 19 19 Critically ill

Definition: nosocomial infections

Method: Cultures

Acinetobacter baumannii (17, 90%)

Staphylococcus aureus (2, 10%)

Silva et al., 2021 (63) 64 212 Critically ill Method: Cultures Staphylococcus spp. (29, 45.3%), Acinetobacter spp. (21, 32.8%), Pseudomonas spp. (21, 32.8%), Stenotrophomonas spp. (9, 14.06%), Klebsiella spp. (8, 12.5%), Enterobacter spp. (6, 9.4%), Enterococcus spp. (6, 9.4%), and Escherichia coli (4, 6%)
Singh et al., 2021 (64) 1413 4259 Overall Method: Cultures, serology and PCR Heamophilus influenzae (9.27%), Staphylococcus aureus (13.17%), Streptococcus pneumoniae (1.94%)
Soogard et al., 2021 (65)* 1 162 Not specific: General including critically ill Definition/Method: Community-acquired bacterial pneumonia was defined as a microbiology-confirmed pneumonia diagnosed concurrent with SARS-CoV-2 infection or within < 48 h of hospital admission NR
Tang et al., 2021 (68) 5 78 Not specific: General including critically ill Method: Mycoplasma pneumonia PCR Mycoplasma pneumoniae = 5
Thelen et al., 2021 (69)* 7 678 Not specific: General including critically ill Method: Blood cultures Escherichia coli = 2, Klebsiella pneumoniae = 1, Pseudomonas aeruginosa = 1, Streptococcus pneumoniae = 2, Staphylococcus aureus = 1
Towsend et al., 2020 (70)* 7 117 Not specific: General including critically ill Method: Cultures and urinary antigen Pseudomonas aeruginosa, Escherichia.coli, Klebsiella pneumoniae,. Oxytoca, Klebsiella aerogenes, MSSA, Streptococcus pneumoniae
Vanhomwegen et al., 2021 (71)* 7 66 Critically ill Method: Respiratory or blood cultures NR
Vaughn et al., 2021 (72)* 59 1705 Not specific: general Method: Blood and sputum cultures, urine pneumococcal and legionella antigen, Mycoplasma pneumonia or Chlamydophila pneumonia PCR NR
Wan et al., 2020 (73) 7 135 Not specific: General including critically ill NR NR
Wan et al., 2020 (73) 7 40 Severe and critically ill NR NR
Wang et al., 2020 (75) 143 339 Elderly NR NR
Wang et al., 2021 (76)* 37 1396 Not specific: General including critically ill Method: Blood, lower respiratory tract, urine and other cultures

Blood cultures: Escherichia coli, Klebsiella pneumoniae, Klebsiella variicola, Proteus mirabilis, MRSA, MSSA and Staphylococcus epidermidis

Respiratory cultures: Escherichia coli (ESBL-producing), group A streptococcus, Haemophilus influenzae, Pseudomonas aeruginosa, MSSA

Zhang et al., 2020 (79) 17 221 Not specific: General including critically ill Definition/Method NR. Likely nosocomial

Mons common: A.baumannii, Escherichia coli = NR

Pseudomonas aeruginosa, Enterococcus = NR

Zhang et al., 2020 (80) 5 58 Not specific: general Method: IgM Mycoplasma pneumoniae = 5
Zhang et al., 2020 (81) 22 38 Critically ill

Definition: VAP

Method: Cultures

Gram negative bacteria (26, 50.00%), Gram positive bacteria (14, 26.92%), virus (6, 11.54%), fungi (4, 7.69%), and others (2, 3.85%)
Zhang et al., 2021 (83) 12 91 Elderly NR NR
Zhang et al., 2020 (84) 228 365 Not specific: general NR NR

n: number of patients with reported bacterial co-infection. N: total number of patients. NR: not reported. MRSA: methicillin resistant staphylococcus aureus. MSSA: methicillin susceptible staphylococcus aureus. VAP: ventilator associated pneumonia, CLI: central line infection. ESBL: extended spectrum beta-lactamase. LRTI: lower respiratory tract infection. BSI: bloodstream infection. CRBSI: catheter-related bloodstream infection. UTI: urinary tract infection. PCR: polymerase chain reaction. SOCa: standard of care

*Specifically reported as bacterial co-infections detected 48 h after admission

Full list of references are in Additional file 1: Material S4

Fig. 2.

Fig. 2

Meta-analysis of bacterial prevalence in patients with SARS-Cov-2: a overall population, b critically ill patients

Twenty studies (31.4%) gave a clear definition of bacterial co-infection, stating that this was diagnosed within 48 h from admission. All of them included cultures, urinary antigen and PCR for definitions of bacterial co-infection. We performed a meta-analysis of this subgroup that showed a prevalence of 4% (15 studies, 95% CI 3% to 6%; I2 94.2%) in the overall population (Fig. 3A) and a bacterial coinfection prevalence of 12% (5 studies, 95% CI 4% to 22%; I2 91.2%) in critically ill patients. (Fig. 3B).

Fig. 3.

Fig. 3

Studies clearly describing bacterial coinfection with microorganism identification in samples taken < 48 h from admission

Antibiotic use

Fifty-two (61.2%) studies were included in the analysis of antibiotic use (Table 3). Meta-analysis showed an overall prevalence of antibiotic use of 60% (38 studies, 95% CI 52% to 76%; I2 98.8%) (Fig. 4A); sub-group analysis restricted to critically ill patients identified a prevalence of antibiotic usage of 86% (19 studies, 95% CI 78% to 92%; I2 93.2%) (Fig. 4B).

Table 3.

Antibiotic use in patients with COVID-19

Author n N Patient groups Antibiotics used
Amit et al., 2020 (3) 131 156 Critically ill NR
Asmarawati et al., 2021 (4)* 164 218 Moderate to critically ill Quinolones (60.1%), cephalosporins (28.4%), carbapenem (23.8%), and aminoglycosides (5.6%)
Baraboutis et al., 2020 (7) 33 49 Not specific: General NR
Bardi et al., 2021 (8) 105 140 Critically ill Ceftriaxone (120, 86%) and/or azithromycin (118, 84%)
Barrasa et al., 2020 (9) 42 48 Critically ill Ceftriaxone, levofloxacin, beta-lactams, azithromycin, linezolid
Barry et al., 2020 (10) 53 99 Not specific: General including critically ill NR
Basakaran et al., 2021 (11) 241 254 Critically ill NR
Bhatt et al., 2021 (12) 301 375 Not specific: General including critically ill Most common: ceftriaxone, azithromycin, and piperacillin-tazobactam
Buckner et al., 2020 (13) 51 105 Not specific: General including critically ill NR
Chen et al., 2021 (15) 60 408 Not specific: General NR
Cheng et al., 2020 (16)* 52 147 Not specific: General Penicillin & cephalosporins = 46, tetracyclines = 14, quinolones = 3, macrolides = 3
Chengy et al., 2020 (17) 45 64 Not specific: General NR
Chong et al., 2021 (18) 205 244 Not specific: General including critically ill NR
D’Onofrio et al., 2020 (21)* 93 110 Not specific: General including critically ill NR
Desai et al., 2020 (22) 494 536 Not specific: General Included a combination of ceftriaxone 2 g intramuscular/intravenous twice daily for 7–10 days and azithromycin 500 mg oral once daily for 3 consecutive days. levofloxacin 750 mg oral/intravenous once daily for 5 days was administered when contraindication
Elabbadi et al., 2021 (25)* 58 101 Critically ill NR
Fan et al., 2021 (27) 29 55 Not specific: General Moxifloxacin (19/29, 65.52%), Linezolid (3/29, 10.34%)
Goncalves et al., 2021 (30)* 162 242 Not specific: General NR
Huang et al., 2020 (34) 41 41 Not specific: General including critically ill NR
Huang et al., 2020 (34) 13 13 Critically ill NR
Hunieres et al., 2021 (37) 88 197 Critically ill NR
Karaba et al., 2021 (38)* 717 1016 Not specific: General NR
Karami et al., 2021 (39)* 556 925 Not specific: General

Amoxicillin/benzylpenicillin (34, 6.1%), Ceftriaxone (95, 17.1%), Cefuroxime (350, 62.9%)

Other antibiotics (48, 8.6%)

Kolenda et al., 2020 (41) 15 99 Critically ill Mainly amoxicillin and clavulanic acid or third generation cephalosporins associated with macrolides
Li et al., 2020 (43) 148 225 Not specific: General Moxifloxacin and others
Liu et al., 2020 (45) 128 140 Not specific: General NR
Liu et al., 2021 (47) 792 1123 Not specific: General

Fluoroquinolones (59.3%)

Moxifloxacin (36.4%)

Mousav Movahed et al., 2021 (51) 243 854 Not specific: General including critically ill NR
Nassir et al., 2021 (52) 82 100 Not specific: General including critically ill NR
Nebreda et al., 2020 (53) 84 712 Not specific: General including critically ill NR
Pulia et al., 2021 (54) 27 73 Not specific: General NR
Quatuccio et al., 2020 (55) 9 69 SOC overall NR
Rothe et al., 2020 (58)* 22 56 critically ill Various mentioned: most common piperacillin-tazobactam
Rothe et al., 2020 (58)* 109 135 Not specific: General including critically ill Various mentioned: most common ampicillin/sulbactam
Seaton et al., 2020 (59)* 219 421 Not specific: General including critically ill Various antibiotics, most common including: doxycycline, amoxicillin, co-amoxiclav, piperacillin-tazobactam and vancomycin among others
Seaton et al., 2020 (59)* 71 110 Critically ill Various antibiotics, most common including: meropenem, piperacillin-tazobactam and co-amoxiclav
Shah et al., 2020 (60) 17 26 Not specific: General including critically ill Majority received vancomycin, tazocin, cefepime, or ceftriaxone
Shao et al., 2020 (61) 81 126 Not specific: General l NR
Sharifipour et al., 2020 (62) 19 19 Critically ill NR
Soogard et al., 2021 (65) 71 162 Not specific: General including critically ill Antibiotics or antifungals
Soogard et al., 2021 (65) 36 41 Critically ill Antibiotics or antifungals
Staub et al., 2021 (66) 86 131 Not specific: General NR
Stevens et al., 2021 (67) 33 346 Not specific: General including critically ill Most common: piperacillin-tazobactam, ceftriaxone and azithromycin
Tang et al., 2021 (68) 58 72 Not specific: General including critically ill Levofloxacin = 21, moxifloxacin = 22, levofloxacin swapped to moxifloxacin = 5, among others
Towsend et al., 2020 (70)* 84 117 Not specific: General including critically ill Treated as lower respiratory tract infection
Vanhomwegen et al., 2021 (71)* 54 66 Critically ill NR
Vaughn et al., 2021 (72) 965 1705 Not specific: General The most commonly prescribed empirical antibiotics were ceftriaxone (663/1705, 38.9%), vancomycin (235/1705, 13.8%), doxycycline (185/1705, 10.9%), and cefepime (177/1705, 10.4%)
Wan et al., 2020 (73) 59 135 Not specific: General including critically ill NR
Wan et al., 2020 (73) 35 40 Severe and critically ill NR
Wang et al., 2020 (74) 27 28 Not specific: General including critically ill NR
Wang et al., 2020 (74) 14 14 Critically ill NR
Yang et al., 2020 (78) 172 251 Not specific: General NR
Zhang et al., 2020 (82) 131 134 Critically ill NR
Zhang et al., 2021 (83) 21 91 Elderly NR
Zhang et al., 2020 (84) 251 365 Not specific: General NR
Zhao et al., 2020 (85) 783 1000 Not specific: General including critically ill NR
Xu et al., 2021 (77) 58 62 Critically ill NR

n: number of patients prescribed antibiotics. N: total number of patients. ITU: intensive treatment unit

**Clearly referred to as empirical use

Full list of references are in Additional file 1: Material S4

Fig. 4.

Fig. 4

Antibiotic usage in: a overall population, b critically ill patients

Eleven studies (12.9%) clearly described empirical antibiotic use. A sub-analysis of these papers found that overall empirical antibiotic use was 62% (eight studies, 95% CI 55 to 69%; I2 95.1%) (Fig. 5A) and in critically ill patients was 66% (six studies, 95% CI 58 to 73%; I2 96.6%) (Fig. 5B).

Fig. 5.

Fig. 5

Studies clearly describing empirical antibiotic use

Antibiotic stewardship

Eleven studies specifically stated that empirical antibiotics were commenced of which five described decision-making processes regarding antibiotics.

Cheng et al. [9] mentioned that 52/147 (35%) patients received empirical antibiotics and that 19 (37%) received antibiotics for more than a week despite negative cultures. The median length of course of empirical antibiotics was seven (IQR = 5 to 12) days.

Rothe et al. [10] described the implementation of an antibiotic stewardship standard operational procedure in their institution in which initiation of antibiotic therapy was recommended only in cases of clinically suspected infection (narrow spectrum aminopenicillin/beta-lactamase inhibitor combination). However, decisions regarding stewardship were at the clinician’s discretion. The most used antibiotic scheme during the observation period were ampicillin/sulbactam (41.5%) and piperacillin/ tazobactam (19.3%) with or without azithromycin. Median duration of were variable being longer in the case of piperacillin/ tazobactam 10 (range 3 to 26) days. Interestingly, azithromycin was not included in the guidelines, although it was used in 43 patients (31.9%) as combination therapy.

Townsend et al. [11] described 84 patients treated empirically for respiratory bacterial co-infection of which 78 (92.9%) received monotherapy. All treatment was initially intravenous, and an oral switch took place in only 34 (40.5%) cases. The median durations of intravenous and oral therapies were five days (range 1 to 14) and three days (range 1 to 4) respectively.

Karami et al. [12] described the adherence to local guidelines on empiric antibiotic therapy in their institution. Mean adherence was 60.3% (range 45.3% to 74.7%) on the first day of admission showing that 556 of 925 (60.1%) patients were prescribed empirical antibiotics. However, the rate of antibiotic prescribing increased after seven days of admission to 669 (72.3%). Confirmed bacterial co-infection was confirmed only in 12/925 (1.2%) patients. Regarding length of antibiotics use, 467 of 555 (84.1%) had five days of antibiotics. Intravenous antibiotics exceeded 48 h in 413 patients who started antibiotic treatment on the first day of admission and oral switched were performed in 9.9% of those.

Vaugh et al. [13] described that of the patients who received empiric antibiotic therapy (N = 965), the majority (612, 63.4%) received antibiotics targeting community-acquired microorganism. The median of duration of inpatient antibiotic was three days (IQR, 2 to 6 days) in the patients receiving antibiotics. Total days of inpatient antibiotic therapy was 4158 days/1000 patients.

The remainder of these studies (Seaton et al. [14], Baskaraban et al. [15], Goncalves et al. [16], Karaba et al. [17], Asmarawati et al. [18], D’onofrio et al. [19] and Elabbadi [20]) did not describe empirical antibiotic duration or any specific criteria for stopping treatment, although they do state that local guidelines for empirical antibiotic use in COVID-19 pneumonitis should be applied.

Discussion

In the absence of clear guidance on when to give empirical antibiotic therapy to patients admitted to hospital with COVID-19 pneumonia, clinicians face a dilemma. In the context of a global pandemic and given the potential risks of antibiotic treatment to patients and to public health, it is essential that the best available evidence is used to support clinicians on the front line to appropriately balance risks to patients and to the wider public.

We analysed bacterial co-infection in different ways in order to evaluate how estimates may vary depending on authors’ definitions. Based only on author descriptions, we found a prevalence of bacterial co-infection of 12% (95% CI 8 to 16%) in the overall population. Interestingly, we observed that bacterial co-infection was lower when including only studies with clear definitions of bacterial co-infection (overall population 4% (95% CI 3 to 6%), critically ill patients 12% (95% CI 4 to 22%)). Our results are similar to that found by other authors who have evaluated co-infections in patients with COVID-19. For example, Rawson et al. [21] conducted a meta-analysis which found a prevalence of bacterial and fungal coinfection of 8%. Langford et al. evaluated bacterial co-infection at presentation and after presentation of COVID-19, finding a prevalence of 3.5% (95% CI 0.4 to 6.7%) for primary co-infection and 14.3% (95% CI 9.6 to 18.9%) for secondary (nosocomial) co-infection [22].

It is important to acknowledge that our estimates of the prevalence of bacterial co-infection prevalence were derived from a number of different definitions, as provided by the authors of the source papers. This is relevant, as although microbiological cultures are the gold standard for diagnosis, these are neither quick nor universally available tools on which to base prescribing decisions, particularly in patients with severe disease.

Our study also finds that, as expected, the overall use of antibiotics in patients with COVID-19 is high compared to the estimated prevalence of bacterial co-infection. We identified a prevalence of empirical antibiotic use of 62% (95%CI 55 to 29%). These estimates are similar to those of Langford et al. [22], who found an overall prevalence of antibiotic use of 71.9% (95% CI 56.1 to 87.7%). Our slightly lower estimates may be explained by having retrieved studies nearly one and a half years after the start of the pandemic. This could reflect changes in empirical practice through increased experience in managing COVID-19, coupled with more data being available to inform evidence-based practice regarding antibiotic use. Furthermore, the previous study provided estimates of antibiotic use based only on patients with culture confirmed bacterial co-infections, while we included all COVID-19 patients that were considered to have an infection in our estimate, regardless of whether bacterial co-infections were ultimately confirmed. In doing so, we have sought to reflect real world practice, and we suggest that estimates of overall empirical antibiotic use that are not restricted to patients with confirmed infections are important to understanding the need for, and potential impact of, antimicrobial stewardship tools and strategies as part of the response to the COVID-19 pandemic.

The final aim of our study was to identify to what degree decisions to stop empirically prescribed antibiotics were being made according to any defined criteria. This aspect has not been addressed previously in published systematic reviews and meta-analyses. Despite terms related to stewardship being specifically included in our search strategy and despite meticulously reading all included citations in full, including discussion sections, we found very little information on stewardship measures. We found this absence of information particularly notable given that antimicrobial resistance is widely acknowledged as being one of the most serious public health challenges of our times [2325]. Whilst we acknowledge that case reports and series are generally more concerned with describing the clinical and demographic characteristics of their patients, it is nevertheless disappointing that the large observed differences between confirmed bacterial co-infection and frequency of antibiotic use does not prompt authors to consider this matter more prominently in their discussions. Despite these deficits in the current literature, we assert that it is of fundamental importance to preserve any goals and achievements relating to antibiotic stewardship established prior to the COVID-19 pandemic. Several antibiotic stewardship programs such as ARK (Antibiotic Review Kit) and TARGET (Treat Antibiotics Responsibly, Guidance, Education, Tools) have been shown to be both feasible and acceptable in supporting the safe discontinuation of antibiotics post-prescription in acute hospital settings [26, 27]. These are just two examples of efforts that must be continued, particularly in the current climate of highly prevalent empirical use of antibiotics during a viral pandemic in which the prevalence of confirmed bacterial co-infection appears to be low.

Our study has some important limitations. The most important being that the COVID-19 pandemic has given rise to an unprecedented situation in the scientific world in terms of a seemingly exponential increase in the volume of related publications over a very short time. Thus, at the time of writing there are likely to be additional studies that would have qualified for inclusion. This rapidity of publication would necessitate updating searches and analysis on as much as a weekly basis, which we suggest would be unrealistic for a piece of peer-reviewed work such as this. It is reassuring to know, however, that other groups pursuing similar research questions [21, 22, 28] have found similar results despite not having included the same studies or conducting searches that cover the same dates. To the best of our knowledge, the present systematic review is the currently most up to date systematic review of this subject, presenting data from more than 30,000 patients from studies identified through an exhaustive search strategy. Another important point to highlight is that most of the included studies in this systematic review are from high income countries, and caution should therefore be exercised when generalising from our results to other settings. Further studies should analyse how COVID-19 has affected antibiotic use in low- and middle-income countries, where the burden of drug-resistant infections is greatest [24].

Another important limitation is one that is inherent to this type of analysis. There is a consensus that the methodology for systematic reviews of prevalence data is not well developed, with a notable lack of methodological and reporting guidance for systematic reviews of prevalence data [29, 30]. Thus, in most cases authors present adapted or de novo tools to assess the quality of the prevalence data that will be included in the analysis, regardless of the study design [22, 28, 31]. In our case, we used a tool that has been developed acknowledging that prevalence data can come from different study designs, however we cannot make an overall assessment of risk of bias [8]. Prevalence metanalysis have also the risk of presenting high level of heterogeneity. We have sought to address the high level of heterogeneity by using statistical correction as well as performing subgroup analyses. Nevertheless, caution should be exercised with extrapolation to specific contexts.

Conclusion

In this study we have reported bacterial co-infection and antibiotic use during the first 18 months of the SARS-CoV-2 pandemic. This work can help clinicians to reflect on and understand the initial response to a global pandemic of a novel respiratory virus. Our results show that there is currently insufficient evidence to support the use of empirical use of antibiotics in most hospitalised patients with COVID-19, as the overall proportion of bacterial co-infection in these patients is low. Furthermore, as the use of antibiotics in COVID-19 appears to have been largely empirical, it is necessary to identify clinical and laboratory markers and to formulate guidelines to promote more targeted administration of antibiotics in patients admitted to hospital with COVID-19.

Supplementary Information

12879_2022_7942_MOESM1_ESM.docx (190.9KB, docx)

Additional file 1. Material S1. PRISMA check list. Material S2. Search Strategy. Material S3. Quality Assessment of included studies. Material S4. Reference list of included studies.

Acknowledgements

None.

Author contributions

MC, GG and EH participated in the conception and design of the study. MC, GG, AG, AM, LK, EH participated in the acquisition of data and analysis. MC, GG, BP and EH participated in the interpretation of data. MC and GG participated drafting the article. All authors read and approved the final manuscript.

Funding

BP was funded in part by the Wellcome Trust [109975/Z/15/Z]. For the purpose of open access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. All other authors—none to declare.

Availability of data and materials

All data generated or analysed during this study are included in this published article [and its supplementary information files].

Declarations

Ethics approval and consent to participate

Not applicable to the current study.

Consent for publication

Not applicable to the current study.

Competing interests

Authors declare no conflict of interest.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

12879_2022_7942_MOESM1_ESM.docx (190.9KB, docx)

Additional file 1. Material S1. PRISMA check list. Material S2. Search Strategy. Material S3. Quality Assessment of included studies. Material S4. Reference list of included studies.

Data Availability Statement

All data generated or analysed during this study are included in this published article [and its supplementary information files].


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