Occurrence and antimicrobial resistance of enterococci isolated from organic and conventional retail chicken

Abstract

Antibiotic-resistant bacteria existing in agricultural environments may be transferred to humans through food consumption or more multifaceted environmental paths of exposure. Notably, enterococcal infections are becoming more challenging to treat as their resistance to antibiotics intensifies. In this study, the prevalence and antibiotic resistance profiles of enterococci in organic and conventional chicken from retail stores were analyzed. Of the total 343 retail chicken samples evaluated, 282 (82.2%) were contaminated with Enterococcus spp. The prevalence was higher in organic chicken (62.5%) than conventional chicken (37.5%). Enterococcus isolates were submitted to susceptibility tests against 12 antimicrobial agents. Among the isolates tested, streptomycin had the highest frequencies of resistance (69.1 and 100%) followed by erythromycin (38.5 and 80.0%), penicillin (14.1 and 88.5%), and kanamycin (11.3 and 76.9%) for organic and conventional isolates, respectively. Chloramphenicol had the lowest frequency (0.0 and 6.6%, respectively). The predominant species in raw chicken was E. faecium (27.3%), followed by E. gallinarum (6.0%), E. casseliflavus (2.1%), and E. durans (1.4%). These species were also found to be resistant to three or more antibiotics. The data indicated that antibiotic-resistant enterococci isolates were found in chicken whether it was organic or conventional. However, enterococci isolates that were resistant to antibiotics were less common in organic chicken (31.0%) when compared with those isolated from conventional chicken (43.6%). The results of this study suggest that raw retail organic and conventional chickens could be a source of antibiotic-resistant enterococci.