Antimicrobial Resistance Pattern of Enterococci Isolated from Stool Samples in a Tertiary Hospital in Nigeria

Abstract

Background: Enterococci cause infections both in and out of the hospital setting and have demonstrated resistance to almost all classes of drugs. A combination of cell wall acting agents and high‑level aminoglycosides is a commonly used regimen for serious infections, but resistance to either renders the synergism ineffective. Vancomycin is the drug of choice for life‑threatening infections, but there have been increasing reports of resistance to the drug. Vancomycin‑resistant enterococci (VRE) infection is usually preceded by gastrointestinal colonization. Aim: This study was carried out to determine the antimicrobial resistance profile of Enterococcus species isolated from stool and the prevalence of VRE. Materials and Methods: Enterococci were identified from stool samples based on characteristic growth patterns on Bile Esculin Agar and MacConkey agar and growth in 6.5% sodium chloride broth. Speciation was by conventional biochemical identification. Antibiotic susceptibility testing and screening for high‑level aminoglycoside resistance (HLAR) were done by modified Kirby–Bauer disk diffusion technique. Susceptibility of isolates to linezolid, penicillin, nitrofurantoin, high‑level gentamicin and streptomycin, tetracycline, ciprofloxacin, vancomycin, and teicoplanin was tested. VRE screening was done using a chromogenic agar. The polymerase chain reaction was used for confirmation. Results: Nine species of Enterococcus were identified from 561 isolates. The most common species were Enterococcus faecium (46.0%), Enterococcus faecalis (21.6%), Enterococcus gallinarum (18.5%), and Enterococcus casseliflavus (5.2%). Resistance was highest to ciprofloxacin, tetracycline, and nitrofurantoin. Lowest resistance was to vancomycin, teicoplanin, gentamicin, and linezolid. VRE prevalence rate was 1.1% and that of HLAR was 20.7%. All VRE had vanA gene. Conclusion: Overall, E. faecium was the predominant species. Highest resistance was to ciprofloxacin and tetracycline.