Molecular Characterization of Antibiotic Resistance in Poultry Gut Origin Enterococci and Horizontal Gene Transfer of Antibiotic Resistance to Staphylococcus aureus

Enterococci, the normal inhabitant of gastrointestinal tract of humans and animals, have emerged as significant antibiotic resistant nosocomial pathogens. The current study was designed to determine the antibiotic resistance profile and genes harbored by isolated strains of Enterococci along with study of antibiotic resistance transfer potential from resistant Enterococci to susceptible pathogenic Staphylococcus aureus in vitro. The PCR based prevalence of Enterococcus faecalis and Enterococcus faecium from 118 broiler cloacal swabs was 60.46 and 30.23%, respectively, indicating that E. faecalis is the predominant species in broilers followed by E. faecium. Enterococci (n=86) were examined for the phenotypic resistance against eleven antibiotics which showed higher level of resistance to lincomycin (96.51%), erythromycin (90.69%), tetracycline (86.04%) and streptomycin (75.58%), intermediate level of resistance to ciprofloxacin (54.65%) and doxycycline (48.83%), and low resistance level to penicillin (26.74%), chloramphenicol (26.74%), amoxicillin (17.44%), augmentin (11.62%) and vancomycin (10.46%). Over 80% Enterococcal isolates were found multidrug resistant (MDR). On the basis of PCR analysis, erm (B) and tet (M) genes were identified in all phenotypically erythromycin and tetracycline resistant strains while van (B) was identified in only 4/9 (44.4%) of vancomycin resistant enterococci (VRE) with no detection of van (A) gene in any VRE. One strain E. faecalis (FME41) was able to transfer the erythromycin resistance to pathogenic Staphylococcus aureus (M-11) in broth mating assay. MDR Enterococci pose therapeutic threat to human community and control on the spread of such MDR Enterococci from poultry to human food chain is crucial.