Oral antimicrobial options for vancomycin-resistant Enterococcus isolates in urine culture

Objectives: The present study aimed to investigate the susceptibility profiles of vancomycin-resistant Enterococcus isolates in urine culture to create an antibiogram to guide selection of oral antimicrobials in British Columbia (BC), Canada.

Methods: An audit was conducted on all urine cultures reported from January 1, 2021, to December 31, 2023, in LifeLabs BC microbiology laboratories. Enterococcus species in urine were routinely tested with ampicillin, ciprofloxacin, nitrofurantoin, tetracycline, and vancomycin. Linezolid and fosfomycin were tested in selected cases.

Results: Three hundred and thirty-five vancomycin-resistant Enterococcus faecium, 47 vancomycin-resistant Enterococcus faecalis, 48 Enterococcus gallinarum, 25 Enterococcus casseliflavus, and no Enterococcus flavescens isolates were reported in urine culture. Vancomycin-resistant E. faecium isolates were >90% susceptible to linezolid, but <15% susceptible to ampicillin, ciprofloxacin, nitrofurantoin, and tetracycline. Vancomycin-resistant E. faecalis isolates were >90% susceptible to ampicillin, linezolid, and nitrofurantoin, but <10% susceptible to ciprofloxacin and tetracycline. E. casseliflavus isolates were >90% susceptible to ampicillin, nitrofurantoin, and tetracycline. E. gallinarum isolates were >90% susceptible to ampicillin and nitrofurantoin. In the seven and 263 selected cases of vancomycin-resistant E. faecium and E. faecalis, respectively, fosfomycin susceptibility rates were 57% and 86%, respectively.

Conclusions: Ampicillin and nitrofurantoin may be considered for urinary tract infections secondary to vancomycin-resistant E. faecalis, E. casseliflavus, and E. gallinarum. Tetracycline may also be considered for E. casseliflavus. Linezolid remained to be the only reliable oral antimicrobial for vancomycin-resistant E. faecium.