Heterogeneity of Highly Susceptible Isolates of Clinical and Environmental Origin: A 5-Year Survey from Iran (2011-2016).

The aim of this study was to evaluate the resistance and virulence characteristics of strains of clinical and environmental origins over a 5-year period in Iran and to determine the genetic diversity of strains using pulsed-field gel electrophoresis (PFGE) method. A total of 20 strains were collected from 850 stool samples of patients with diarrhea, and 18 e spp. including 10 were collected from water, food, and vegetable samples. The most frequently isolated strains belonged to biotype (BT) 1A (83.33%). No BT4 was detected that can be attributed to the absence of pig animal reservoir in Iranian food chain. The most frequent chromosomal virulence genes among the isolates were (100%), tA (67%), ystB (83%), (20%), and (17%). The most frequent chromosomal virulence genes among non- spp. isolates were (87.5%), (37.5%), and (37.5%). None of the isolates harbored plasmid origin virulence genes. None of the isolates was resistant to ciprofloxacin, gentamicin, tetracycline, cotrimoxazole, and chloramphenicol, whereas 90% of the and 62.5% of the spp. strains were resistant to ampicillin. PFGE genotyping showed a heterogeneous population of highly susceptible spp. in both clinical and environmental samples, putting forward a good prognosis in the treatment of patients with yersiniosis. The occurrence of biotype 1A with genotype in clinical strains implies the significance of , , and gene products in turning of naturally nonpathogenic biotype 1A strains into clinically important pathogens.