Pathogenic characteristics and virulence genes of  Shigella flexneri  4c in Jiangsu province

Objective　The study was conducted to identify the biochemical characteristics, antibiotic resistance and virulence genes of Shigella flexneri 4c isolates in Jiangsu province.Methods　Biochemical identification of the strains wasperformed using API 20E, serotyping using slide agglutination, antimicrobial susceptibility testing using the Kirby Bauermethod and detection of ipaH, set1, sen, ial virulence genes using PCR. Results　The S. flexneri 4c isolates, fermenting glucose and mannitol with 41.0% strains fermenting arabinose, were found 100% resistant to amoxicillin/clavulanate and nalidixic acid, 89.7% resistant to ampicillin, tetracycline and sulfamethoxazole; 79.5% isolates possessed resistance to more than a half of antibiotic species. Presence of ipaH, set1, sen, ial virulence genes was identified among 100.0%, 100.0%, 92.3% and 92.3% of tested isolates, respectively, while 92.3% strains (36/39) carried all four genes. Conclusion　Strong multidrug resistance of S. flexneri 4c isolates was found in the present study. Susceptibility to gentamicin, cephalosporin and norfloxacin was identified. Presence of virulence genes associated with strong pathogenicity was found in a high proportion of isolates.