Antibiotic Sensitivity and Antibiotic Resistance Genes in Enterococcus Species Isolated from Chicken Feces

Abstract

Enterococci are Gram positive, catalase negative, facultative anaerobic cocci (single, paired or chained), and are found in intestinal tract of many animals including chicken. The present work was aimed at studying the prevalence of Enterococcus species E. faecalis and E. faecium in feces of commercial poultry. A total of 254 fecal samples were collected from apparently healthy broiler chicken sold in the market from random slaughter shops of different cities of Pakistan. From those 254 samples, 160 Enterococcus isolates were recovered. Further testing showed 53 (33%) of the isolates were E. faecalis and 107 (67%) were E. faecium. After isolation and confirmation, AST was done for 160 Enterococcal isolates. All Enterococcus isolates showed multidrug resistance. Among 53 E. faecalis, the drugs for which the sensitivity values were high were ampicillin (77%), nitrofurantoin (77%), fosfomycin (75%) and teicoplanin (60%) while the drugs to which the resistance values were greater than 50% were erythromycin (98%), chloramphenicol (96%), tetracycline (94%), levofloxacin (92%), minocycline (79%), doxycycline (79%), ciprofloxacin (77%), quinupristin (77%) and norfloxacin (64%). Among the 107 E. faecium isolates, the drugs which were highly effective towards E. faecium were fosfomycin (61%), teicoplanin (61%), and ampicillin (60%) while the antibiotics against which high resistance was observed were tetracycline (97%), erythromycin (94%), norfloxacin (90%), ciprofloxacin (86%), chloramphenicol (82%) and levofloxacin (82%), quinupristin (82%), doxycycline (80%), and minocycline (69%). Thus, both Enterococcus species showed highest resistance towards, erythromycin levofloxacin, tetracycline, and chloramphenicol. After AST, the most resistant 31 isolates were selected for detection of some selected antibiotic resistance genes. PCRs were done for antibiotic resistance genes against tetracyclines and quinolones. Among the six tetracycline resistance genes of Enterococci, two genes were detected from almost all the isolates. tetM was found in 57% and 42% of E. faecalis and E. faecium isolates respectively and tetL was noted in 40% and 60% of the E. faecalis and E. faecium respectively, while tetO was detected in only one isolate of E. faecium. While the quinolones resistance genes oqxA qnrA, qnrB, and qnrS were not observed in any of the isolate.