Virulence and Antibiotic Resistance Patterns of Extended-Spectrum Beta-Lactamase-Producing Salmonella enterica serovar Heidelberg Isolated from Broiler Chickens and Poultry Workers: A Potential Hazard

The current study investigated the emergence of multidrug-resistance (MDR), extended-spectrum beta-lactamase (ESBL)-producing Salmonella enterica serovar Heidelberg in broiler chickens and workers in poultry farms. A total of 33 S. Heidelberg isolates were recovered; 24 from the broiler cloacal swabs and 9 from the farm workers. All the S. Heidelberg isolates were tested for susceptibility to 11 antimicrobial agents and for the presence of resistance and virulence genes. MDR strains were found in 95.8% (23/24) and 88.8% (8/9) of the broiler and human isolates, respectively. Among the MDR strains, 66.6% of the broiler isolates and 55.5% of the human isolates were ESBL producing. The majority of broiler isolates showed resistance to ampicillin (100%) and ceftriaxone (91.6%), followed by ceftazidime and imipenem, (87.5%) and (75%). The resistance rate of the human isolates to those antibiotics were lower than the broiler isolates; ampicillin (88.8%), ceftriaxone (66.6%), ceftazidime (77.7%), and imipenem (66.6%). The resistance determinant genes found among the isolated strains was bla(SHV-1), bla(TEM-1), bla(CMY-2), bla(OXA-1), bla(CMY-M2), bla(PSE-1), and ampC. The most detected ESBL genes for broiler and human isolates were ampC (63.7%) and bla(SHV-1) (56.6%), followed by bla(CMY-M2) (48.5%), bla(TEM-1) (39.4%), and bla(OXA-1) (27.3%); whereas bla(CMY-2) and bla(PSE-1) were not detected. The finding of chromosomal and plasmid virulence genes revealed that the invA (100%), stn, sipC, and rck (72.8%), spvC (66.7%), ssr (63.6%), sopB (54.6%), and hilA and sipA (3.0%), while pefA and ssaR were absent. An elevated rate of MDR Salmonella Heidelberg in chickens is of potential great health risk. This signifies the role of the food of animal origin as a reservoir of MDR Salmonella that can affect the human health.