Genetic characterization of resistance and virulence genes in Enterococcus species from animal isolates in Durban.

Abstract

Misuse of antimicrobials in animal agriculture has given rise to strains of bacteria that are resistant to multiple antibiotics. Enterococci bacteria have emerged among such antibiotic-resistant strains of bacteria and infections due to antibiotic-resistant bacteria is one of the world’s critical health challenge. Enterococci are gut commensal bacteria but are currently confirmed pathogenic bacteria responsible for so many hospital-acquired infections like urinary tract infections. The aim of this research was to detect the occurrence of Enterococcus species in chickens, cats, and dogs; their phenotypic and genotypic resistance to antibiotic drugs and virulence genes. Isolation of Enterococcus species was done using microbiological culture methods and confirmed using specific primers through Polymerase Chain Reaction (PCR). Presumptive Enterococcus growth on bile esculin agar was positive for 94% of all the isolates. Overall, 77.3% of the isolates were positive for Tuf gene (Enterococcus genus-specific gene). Enterococcus faecalis was detected at a higher frequency (40.4%; P <0.05) compared to Enterococcus faecium (8.5%). All the Enterococcus isolates were susceptible to High-Level Gentamicin on antimicrobial susceptibility test. Enterococcus species in chickens exhibited higher resistance to the antibiotics than the pets. Highest resistance was observed in Quinupristin/Dalfopristin (89.4%) followed by Vancomycin (87.9%), Rifampicin (85%), Ampicillin (76.6%), Erythromycin (72.3%), and Tetracycline (64.5%). Chloramphenicol (24.8%), High-Level Streptomycin Resistance (24.1%), and Ciprofloxacin (14.2%). Eighty-four percent (84%) of the Enterococcus isolates expressed multidrug resistance (MDR). Three of the four resistance genes screened were detected: 21.3%, 7.8% and 4.3% for Kanamycin, Streptomycin, and Vancomycin resistance genes respectively. Gentamicin resistance gene was absent in all the isolates. PCR detection of virulence gene showed highest prevalence in EfaA gene at 88.7% frequency followed by GelE (82.3%), ccf (81.6%), Esp (26.2%) and CylA (25.5%). All E. faecalis and E. faecium detected harbored multiple virulence genes. These findings show that chickens, cats, and dogs can be colonized by pathogenic Enterococci which harbor resistance and virulence genes and are multidrug resistant. It is therefore important that antibiotics are used prudently in animal husbandry to mitigate emergence and transfer of Enterococci pathogens to humans via food chain and direct contact of pets by their owners.