Prevalence and resistance trends of Gram positive cocci Staphylococcus aereus and Enterococcus spp. in a tertiary care hospital

Abstract

Purpose: Antimicrobial resistance is a silent pandemic. In this study, it was aimed to determine the distribution and resistance trends of Staphylococcus aureus (S. aureus), Enterococcus faecium (E. faecium) and Enterococcus faecalis (E. faecalis) isolates, which are among the priority pathogens of the World Health Organization in bloodstream infections. Materials and Methods: This was a retrospective study conducted between January 1, 2021 and March 31, 2023. The blood cultures (n=1261), of which microbiologically tested by using an automated system, were screened in the relevant period via laboratory information system. Results: Of the total 941 isolates, 51.9% were S. aureus (n=488), 22.9% were E. faecalis (n=216), and 25.2% were E. faecium (n=237). Of the patients, 89.1% were inpatients (n=838), and 10.9% were outpatients (n=103). The most of patients were hospitalized in internal medicine departments (53.3%) and in intensive care units (35%). Among S. aureus isolates, the resistance rate to benzylpenicillin was 93.8%, to methicillin 44.3%, to teicoplanin 3.7%, and to linezolid 0.4%. Vancomycin and tigecycline resistances were not detected. Of the E. faecalis isolates, 5.5% were resistant to ampicillin, 3.3% to vancomycin, 3.2% to linezolid, and 0.7% to tigecycline. The resistance rates for E. faecium strains were 90.9% for ampicillin, 28.7% for vancomycin, 17.7% for tigecycline, 4.3% for linezolid, and 0.8% for teicoplanin. When the susceptibilities of all three bacteria were compared, a statistically significant difference was found between teicoplanin, vancomycin, tigecycline and linezolid susceptibilities. The methicillin resistance was higher in internal medicine and intensive care units. The levofloxacin and vancomycin resistance were more prevalent in intensive care units. Conclusion: MRSA (44.3%), vancomycin (28.7%) and tigecycline (17.7%) resistant E. faecium rates are well above the national data. The epidemiology on resistance trends, which will guide clinicians in the management of bloodstream infections, should be carried out periodically.