A-304 Changes in the Antimicrobial Resistance Profile of the Staphylococcus aureus after the COVID-19 Pandemic

Background Staphylococcus aureus is an important human pathogen causing a wide range of clinical infections in both healthcare and community settings. During the SARS-COV-2 period, the rate of methicillin-resistant Staphylococcus aureus (MRSA) in nosocomial cases increased in several countries, and treatment remains challenging due to the emergence of multidrug-resistant strains. The aim of this study was to describe the antimicrobial resistance profile of Staphylococcus aureus based on the analysis of clinical specimens processed by a Brazilian clinical laboratory, comparing three different epidemiological periods: pre-Covid-19 (2018-2019), Covid-19 (2020-2021) and post-Covid-19 (2022-2023). Methods A retrospective analysis of 36,998 S. aureus strains isolated from community and hospital patients attending a clinical diagnostic laboratory. Bacterial identification was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS), and minimal inhibitory concentrations of antibiotics were determined using the Vitek®2 system according to the manufacturer*s recommendations. Results A total of 36,998 S. aureus from hospitalized and non-hospitalized patients were included. The frequency of S. aureus detected during the period was: 34.4% (12,731/36,998) in pre-Covid-19, 26.3% (9,744/36,998) in Covid-19 and 39,2% (14,523/36,998) in post-Covid-19 period. Between the isolating sites from S. aureus, blood (45.7%) was the most frequent, followed by secretions (14.9%), urine (10.1%), skin and soft tissue (10.0%), catheter tip (4.0%) and others. The main age group was over 60 years old with 39.8%, followed by 41-59 years old with 27.4% of cases considering the entire period analyzed. Of the 36,998 isolates, 40.6% were categorized as MRSA and 59.4% as methicillin susceptible S. aureus (MSSA). The antimicrobial resistance profile for MRSA group in pre-Covid-19, Covid-19 and post-Covid-19 periods were as follow: methicillin (38.2%, 40.3% and 42.8%), gentamicin (5.8%, 4.5% and 11.9%), levofloxacin (64.3%, 69.4% and 60.9%), erythromycin (81.1%, 84.7% and 81.5%), clindamycin (70.8%, 70.6% and 60.5%), linezolid (0,2%, 0% and 0,1%), daptomycin (0.3%, 0.1% and 0.1%), teicoplanin (0.2%, 0.1% and 0.3%), rifampicin (5.8%, 11.8% and 7.9%), trimethoprim-sulfamethoxazole (7.9%, 8.8% and 10.8%). The MSSA group showed 55.6%, 64.6% and 64.2% of resistance rate to erythromycin and 49.0%, 58.8% and 56.7% to clindamycin of the three periods analyzed, respectively. In addition, none of the S. aureus isolates exhibited resistance to vancomycin. Conclusion Our findings showed a large variation between MRSA and MSSA, with the majority of MSSA isolates being susceptible to all antibiotics, except for clindamycin and erythromycin. During and after the pandemic period, an increase in the incidence of MRSA was observed, which was associated with an increase in resistance rates to gentamicin and trimethoprim-sulfamethoxazole. This MRSA pattern may have been intensified by the Covid-19 pandemic. Infection prevention and control strategies should be strengthened to address the increasing rate of multidrug-resistant bacteria in both healthcare and community settings.