Prevalence and Characterization of Salmonella Isolated from Chickens in Anhui, China

Salmonella is one of the most important zoonotic pathogens that can cause both acute and chronic illnesses in poultry flocks, and can also be transmitted to humans from infected poultry. The purpose of this study was to investigate the prevalence, antimicrobial resistance, and molecular characteristics of Salmonella isolated from diseased and clinically healthy chickens in Anhui, China. In total, 108 Salmonella isolates (5.66%) were successfully recovered from chicken samples (n = 1908), including pathological tissue (57/408, 13.97%) and cloacal swabs (51/1500, 3.40%), and S. Enteritidis (43.52%), S. Typhimurium (23.15%), and S. Pullorum (10.19%) were the three most prevalent isolates. Salmonella isolates showed high rates of resistance to penicillin (61.11%), tetracyclines (47.22% to tetracycline and 45.37% to doxycycline), and sulfonamides (48.89%), and all isolates were susceptible to imipenem and polymyxin B. In total, 43.52% isolates were multidrug-resistant and had complex antimicrobial resistance patterns. The majority of isolates harbored cat1 (77.78%), blaTEM (61.11%), and blaCMY-2 (63.89%) genes, and the antimicrobial resistance genes in the isolates were significantly positively correlated with their corresponding resistance phenotype. Salmonella isolates carry high rates of virulence genes, with some of these reaching 100% (invA, mgtC, and stn). Fifty-seven isolates (52.78%) were biofilm-producing. The 108 isolates were classified into 12 sequence types (STs), whereby ST11 (43.51%) was the most prevalent, followed by ST19 (20.37%) and ST92 (13.89%). In conclusion, Salmonella infection in chicken flocks is still serious in Anhui Province, and not only causes disease in chickens but might also pose a threat to public health security.