Molecular Characterization of Virulence Genes and Quinolone Resistance Determinants in Salmonella Strains from Retail...

Background/Objectives:Salmonella is a major foodborne pathogen commonly associated with poultry products and poses a significant public health concern worldwide. This study aimed to determine the distribution of Salmonella serotypes isolated from retail chicken meat and to evaluate their quinolone resistance profiles, along with selected virulence and antimicrobial resistance genes. Methods: A total of 53 Salmonella isolates recovered from retail chicken meat were serotyped and subjected to quinolone susceptibility testing and PCR-based detection of class 1 integrons, antimicrobial resistance genes, and virulence-associated genes. Results: Of these, 41 (77.35%) were identified as Salmonella Infantis (S. Infantis) and 12 (22.65%) as Salmonella Enteritidis (S. Enteritidis). Antimicrobial susceptibility testing revealed that 47 (88.67%) isolates were resistant to enrofloxacin, 32 (60.37%) to ciprofloxacin, 26 (49.05%) to moxifloxacin, and 24 (45.28%) to norfloxacin. All S. Enteritidis isolates were susceptible to ciprofloxacin, moxifloxacin, and norfloxacin. Broth microdilution results showed that 20.75% of isolates were susceptible and 77.35% were intermediate to ciprofloxacin, with minimum inhibitory concentration values ranging between 0.02 and 1 µg/mL. The class 1 integron gene (int1) was detected in 83.01% of isolates. The mcr1, mcr2, mcr3, mcr4, mcr5, qnrA, and qnrC genes were not detected in any isolates. Among S. Infantis isolates, 2 (4.88%) and 9 (21.95%) were positive for qnrB and qnrSm genes, respectively, while all S. Enteritidis isolates were negative for these genes. Virulence gene analysis showed that sitC was detected in 100% of isolates and sopE in 98.11%. The spvC and pefA genes were detected in 13.2% of isolates. Conclusions: The findings suggest that S. Infantis was the predominant serotype and that quinolone resistance was common among Salmonella isolates from retail chicken meat. The virulence gene profiles indicated that these isolates harbored a wide range of markers associated with host invasion, intracellular survival, and adaptation within the host environment. Moreover, the high prevalence of the int1 gene highlights the need for further investigation of integron-associated resistance determinants and their potential role in the dissemination of antimicrobial resistance through chicken products and the associated risk of transmission to humans.