Analysis of the phenotypic and genotypic antimicrobial resistance profiles of clinically significant enterococci isolated in the Provincial Specialist Hospital in Lublin, Poland

The increasing significance of enterococci as healthcare-associated pathogens can be linked to their limited susceptibility to antibiotics.

In this study, phenotypic and genotypic resistance profiles of 35 [n=18 E. faecium (Efm); n=17 E. faecalis (Efs)] invasive isolates cultured from hospitalized patients were analysed. Phenotypic identification was verified by the multiplex PCR targeting the 16S rDNA and the ddl genes encoding for the Efs and Efm – specific ligases. Antimicrobial susceptibility was determined using the disc diffusion method and E-tests. The high-level streptomycin resistance (HLSR), high-level gentamicin resistance (HLGR) and glycopeptide resistance was verified by amplification of the ant(6)-Ia, aac(6’)-Ie-aph(2’’)-Ia, as well as vanA and vanB genes, respectively.

More than 70% of all isolates were cultured from patients in the Intensive Care and Internal Medicine Units. Blood was the predominant (77%) site of isolation. All Efm isolates were resistant to ampicillin, imipenem, and norfloxacin; 17 isolates demonstrated high-level aminoglycoside resistance (HLAR), including 27.7% with HLSR, 38.8% with HLGR and 27.7% with both phenotypes. HLAR was also common in Efs (HLSR>70%, HLGR>50%), followed by norfloxacin (64.7%) and ampicillin (11.7%) resistance. The ant(6)-Ia and aac(6’)-Ie-aph(2’’)-Ia genes were detected in >90% of the HLSR and HLGR isolates, respectively. Glycopeptide resistance was detected in 4 (22.2%) Efm isolates and mediated by the vanA gene. 19 (54.3%) isolates were multidrug resistant, including 17 (89.5%) Efm. All isolates were susceptible to linezolid.

The study constitutes a contribution to the analysis of enterococcal antimicrobial resistance in Polish hospitals. The monitoring of enterococcal prevalence and antimicrobial resistance is crucial to control and prevent infections.