Occurrence and Multidrug Resistance of in Chicken Meat from Different Production Systems.

is the leading bacterial cause of diarrheal disease worldwide and poultry remains the primary vehicle of its transmission to humans. Due to the rapid increase in antibiotic resistance among strains, the World Health Organization (WHO) added fluoroquinolone resistance to the WHO list of antibiotic-resistant "priority pathogens". This study aimed to investigate the occurrence and antibiotic resistance of spp. in meat samples from chickens reared in different production systems: (a) conventional, (b) free-range and (c) backyard farming. spp. was detected in all samples from conventionally reared and free-range broilers and in 72.7% of backyard chicken samples. Levels of contamination were on average 2.7 × 10 colony forming units (CFU)/g, 4.4 × 10 CFU/g and 4.2 × 10 CFU/g in conventionally reared, free-range and backyard chickens, respectively. and were the only species isolated. Distribution of these species does not seem to be affected by the production system. The overall prevalence of isolates exhibiting resistance to at least one antimicrobial was 98.4%. All the isolates showed resistance to ciprofloxacin and to nalidixic acid, and 79.5 and 97.4% to ampicillin and tetracycline, respectively. In total, 96.2% of isolates displayed a resistant phenotype to ciprofloxacin and to nalidixic acid, and 92.3% to ampicillin and tetracycline. Of the 130 isolates tested, 97.7% were classified as multidrug resistant (MDR).