Associated antimicrobial resistance in Enterococcus spp. clinical isolates

Introduction: The increasing prevalence of enterococci strains in hospitals, particularly among isolates of vancomycin-resistant enterococci (VRE), poses important problems because of the limited effect of antimicrobial therapy for enterococcal infections. Methods: This work presents a retrospective investigation of quantitative in vitro susceptibility data for the range of antimicrobials against Enterococcus spp. isolates and evaluation of the association of resistance between antimicrobial agents recommended as the treatment of choice for infections caused by VRE through calculation of the relative risk. Results: Of the 156 enterococci isolates, 40 (25.6%) were resistant to 3 or more antimicrobials, including 7.7% (n = 12/156) vancomycin resistant. The association of elevated resistance was more pronounced among VRE isolates against alternative and primary antimicrobials for the treatment of infections caused by these pathogens, including ampicillin (100%, RR = 7.2), streptomycin (90.9%, RR = 4.9), rifampin (91.7%, RR = 3.1) and linezolid (50%, RR = 11.5), despite high susceptibility to this drug (94.9%). Conclusions: The significant associated resistance to alternative and first choice antimicrobials used in the treatment of serious infections of strains with the VRE phenotype and that require a combined therapeutic regime, revealed even more limited therapeutic alternatives in the institution analyzed.