Incidence of bloodstream infections due to multidrug-resistant pathogens in ordinary wards and intensive care units before and during the COVID-19 pandemic: a real-life, retrospective observational study

Abstract

Purpose: SARS-COV-2 pandemic led to antibiotic overprescription and unprecedented stress on healthcare systems worldwide. Knowing the comparative incident risk of bloodstream infection due to multidrug-resistant pathogens in COVID ordinary wards and intensive care-units may give insights into the impact of COVID-19 on antimicrobial resistance.

Methods: Single-center observational data extracted from a computerized dataset were used to identify all patients who underwent blood cultures from January 1, 2018 to May 15, 2021. Pathogen-specific incidence rates were compared according to the time of admission, patient's COVID status and ward type.

Results: Among 14,884 patients for whom at least one blood culture was obtained, a total of 2534 were diagnosed with HA-BSI. Compared to both pre-pandemic and COVID-negative wards, HA-BSI due to S. aureus and Acinetobacter spp. (respectively 0.3 [95% CI 0.21-0.32] and 0.11 [0.08-0.16] new infections per 100 patient-days) showed significantly higher incidence rates, peaking in the COVID-ICU setting. Conversely, E. coli incident risk was 48% lower in COVID-positive vs COVID-negative settings (IRR 0.53 [0.34-0.77]). Among COVID + patients, 48% (n = 38/79) of S. aureus isolates were resistant to methicillin and 40% (n = 10/25) of K. pneumoniae isolates were resistant to carbapenems.

Conclusions: The data presented here indicate that the spectrum of pathogens causing BSI in ordinary wards and intensive care units varied during the pandemic, with the greatest shift experienced by COVID-ICUs. Antimicrobial resistance of selected high-priority bacteria was high in COVID positive settings.

Keywords: Acinetobacter; Antimicrobial resistance; COVID; Intensive care unit; MRSA.

Fig. 1

Flow-chart of the study. CA_BSI community-acquired bloodstream infection, HAI_BSI hospital-acquired bloodstream infection

Fig. 2

Resistance patterns per study cohort and ward type. The diagrams show the frequencies of selected resistance phenotypes stratified forward type (in brackets the total number of isolates per specie per period). Vertical lines indicate overall and pairwise comparisons according to the studysubgroups (dotted line: p < 0.05; continuous line: p < 0.001). CRAB carbapenem-resistant A. baumannii, CR carbapenem resistant, CRPA carbapenem-resistant P. aeruginosa; MRSA methicillin-resistant S. aureus, MSSA methicillin-sensitive S. aureus, Other: resistant to at least one antimicrobial class, PDR pandrug resistant (limited to tested antimicrobials), VRE vancomycin-resistant E. faecium; Further information is reported on Supplementary Tables S1 and S2 (web-only)

Fig. 3

Pathogen-specific incidence rates per ward type. Incidence Rates per 100 persons-days of hospitalization, stratified for study subgroup, i.e. pre-COVID (green, n = 7382), COVID negative (orange/yellow, n = 6299) and COVID positive (red, n = 1203), both overall (upper panel) and layered as ordinary wards (left panel) and ICU (right panel). ICU Intensive Care Unit

Fig. 4

Forest Plot showing pairwise incidence rate comparisons in the overall population, ordinary wards and intensive care units. Overall population is represented in panel A–C, ordinary wards in panel D–F, and intensive care units in panels G–I. Pairwise comparisons between pre-COVID and COVID-negative cohorts are reported in panels A, D and G, while between pre-COVID and COVID-positive cohorts in panels B, E and H and between COVID-negative and COVID-positive cohorts in panels C, F and I. IRR incidence rate ratio, 95% CI 95% confidence interval