[Surveillance on the etiology and molecular epidemiology of Shigella sonnei isolated in Henan province from 2011 to 2014].

OBJECTIVE: To detect and analyze the distribution of virulence factors, antimicrobial resistance and pulsed field gel electrophoresis (PFGE) patterns of Shigella sonnei, isolated in Henan province from 2011 to 2014.

METHODS: Samples of diarrhea patients were collected and isolated with SS selective culture medium in 37 ℃ for 18-24 hours. All strains were identified under the Kligler iron agar/motility-indol-urea biochemical action and API20E biochemical system. Serological typing and prepared DNA template were carried out with thermal cracking method and multiplex PCR, to detect the virulence genes of Shigella sonnei. According to the molecular typing method and K-B drug susceptibility testing method published by the international PulseNet bacterial infectious disease monitoring network and USA clinical and Laboratory Standards Institute, antimicrobial susceptibility tests and PFGE molecular characteristics of these positive strains isolated from sentinel hospitals patients stool samples were analyzed.

RESULTS: Among the 98 strains of Sonnei type Ⅰ and 118 strains of Sonnei type Ⅱ, all the strains carried carry different virulence genes including SHET-1B, SHET-2, ial, ipaH genes, with 4 kinds of virulence gene combination types. All the 216 strains of Shigella sonnei belonged to the multi-drug resistant strains, including 34 isolates resistant to 2-4 kinds of antibiotics(15.7%), 147 isolates to 5-8 kinds of antibiotics (68.1%), 24 to 9-10 kinds of antibiotics (11.1%), 7 to 11 kinds of antibiotics (3.2%), and 4 to 13 kinds of antibiotics (1.9%). A total of 100 strains of Shigella sonnei were divided into 31 molecular patterns, digested by XbaⅠ and PFGE. Each pattern contained 1-13 strains with similarities ranged from 68.6%-100.0%.

CONCLUSIONS: All the Shigella sonnei strains carried virulence pathogenic factors, presenting serious status on drug resistance. PFGE fingerprinting patterns showed high polymorphism and dominant characteristics. PFGE patterns of partial strains and corresponding antidrug spectrum presented certain relevance and with same aggregation relationship.