Characterization of vancomycin resistance mechanisms in Enterococcus faecium isolates from a Brazilian tertiary hospital

Background and Objectives: Vancomycin-resistant Enterococcus faecium (VREf) is an opportunistic pathogen responsible for hospital infections, characterized by increasing prevalence and a lack of comprehensive epidemiological studies. We aimed to assess the occurrence of VREf and vancomycin resistance genetic elements vanA and vanB in strains isolated from clinical samples of patients treated at a tertiary hospital in Brazil. Methods: The isolates were obtained from convenience sampling according to routine medical requests for nine months. Enterococcus faecium strains were identified by routine biochemical tests, BD Phoenix (R) Automated Microbiology System and confirmed by MALDI-TOF Mass Spectrometry. The antimicrobial sensitivity profile was determined by disk-diffusion method and BD Phoenix (R) Automated Microbiology System. Vancomycin resistance was specially assessed and confirmed by the conventional microdilution technique. Molecular detection of vanA and vanB resistance genes was investigated by polymerase chain reaction (PCR) and confirmed by Sanger DNA sequencing. Results: A total of 8,376 cultures was performed, of which 19 (0.22%) were identified as Enterococcus sp. and nine (47%) as vancomycin-resistant E. faecium. The antimicrobial susceptibility testing analysis of E. faecium showed high resistance to antimicrobial agents. The analysis to determine the genetic profile of E. faecium isolates by PCR showed that all of them carried the vanA gene associated with vancomycin resistance. Conclusion: During the study period, there was low occurrence of Enterococcus species observed. However, all VREf isolates carried the vanA gene associated with vancomycin resistance and showed resistance to commonly used antimicrobial agents, highlighting concerns about the effectiveness of available antimicrobial treatments for infections caused by these isolates.