Background and importance In the absence of evidence about the incidence of bacterial co-infection, antibiotic treatment was widely prescribed to prevent this potential complication. Increasing antibiotic consumption could have exerted an ecological pressure on microorganisms with potential clinical implications that need to be examined.

Aim and objectives The aim of this study was to analyse antibiotic consumption and antimicrobial resistant microorganism isolates during the peak incidence of the COVID-19 first wave at our hospital.

Material and methods An observational, descriptive, cross sectional study was carried out. Antibiotic consumption data for March and April 2020 and 2019 were analysed. Defined daily dose (DDD) per 100 bed days was used as the consumption indicator and changes were expressed in absolute and percentage terms. Isolates of Enterobacteriaceae (Escherichia coli and Klebsiella pneumoniae) were examined for March and April 2020 and compared with the average over 2019. Extended spectrum beta-lactamase (ESBL) producing Enterobacteriaceae were expressed in relative terms over their total isolates.

Results For the period under study, antibiotic consumption increased from 79.94 to 141.10 DDD/100 bed days in 2020, which was an increase of 77%. Macrolides and cephalosporins were among the groups of antibiotics with the highest consumption, representing 37% (52.79 DDD/100 bed days) and 32% (45.41 DDD/100 bed days) of total consumption, respectively, and almost 70% jointly. Additionally, ceftriaxone and azithromycin showed an increase in DDD/100 bed days of 4.5× (8.91 vs 39.97) and 27.4× (1.89 vs 51.90) with respect to the same period in 2019.

The share of ESBL producing Escherichia coli was 12% (13/111 isolates) and 23% (20/87 isolates) in March and April 2020 compared with an average of 11% (273/2494 isolates) in 2019. ESBL producing Klebsiella pneumoniae was 23% (8/35 isolates) and 57% (25/44 isolates) in March and April 2020 versus 24% (153/642 isolates) on average in 2019.

Conclusion and relevance During the study period, antibiotic consumption increased markedly. The increasing use of third generation cephalosporins, which have no effect on ESBL producing Enterobacteriaceae, may have contributed to the observed changes in the bacterial ecology in our hospital. As the incidence of bacterial co-infection on admission was reported to be lower than 5% and the increase in antibiotic consumption translated into selection of antibiotic resistant bacteria, it is important to properly assess antibiotic treatment for each particular case in future outbreaks of SARS-CoV-2 infections.

Conflict of interest No conflict of interest