Antibiotic resistance patterns, characteristics of virulence and resistance genes and genotypic analysis of Salmonella serotypes recovered from different sources

The present study evaluated the Salmonella isolates obtained from various origins in Iran. Salmonella strains previously recovered and stored in the veterinary microbiology laboratory were serotyped and subjected to antibiotic susceptibility test, detection of the virulence and resistance genes by polymerase chain reaction (PCR), and genotyping by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). All Salmonella isolates showed resistance to erythromycin and the most resistance rates were detected for trimethoprim (۸۶.۶۶%), ampicillin (۷۵.۰۰%), and sulfamethoxazole-trimethoprim (۶۳.۳۳%), respectively. In total, ۸۶.۳۳% of the isolates were known as multi-drug resistant and none of the isolates showed resistance to cefepime, nalidixic acid, imipenem, ceftriaxone, and polymyxin B. The virulence genes, invA, sdiA, and hilA besides the tetA resistance gene were identified in all ۶۰ Salmonella strains. The most prevalent resistance genes were respectively tetC (۷۰.۰۰%), sul۲ (۵۸.۳۳%), and ereA (۵۵.۰۰%). Statistical analysis revealed a significant difference between Salmonella serotypes associated with the sul۱ resistance gene. In ERIC-PCR analysis, ۱۴ distinct clusters were obtained. Statistically, there were significant relationships between the source and ERIC’s genomic pattern and between the serotype of Salmonella isolates and genotypic pattern of ERIC. According to the results, Salmonella serotypes from non-human sources had considerable resistance to different antibiotics and carried significant virulence determinants and resistance genes. In addition, ERIC-PCR showed relevant results in discriminating Salmonella serotypes from other sources.

Keywords:

antibiotic susceptibility , ERIC-PCR , Salmonella serovars , virulence determinants