Drug resistance and molecular typing of Vibrio parahaemolyticus from diarrhea patients in Songjiang district, Shanghai, 2016–2020

  Objective  To understand the virulence genes, antibiotics resistance and molecular typing of Vibrio parahaemolyticus isolated from diarrhea patients in Songjiang district, Shanghai, and provide scientific basis for the better prevention of foodborne diseases.

  Methods  V. parahaemolyticus detection was conducted according to WS271-2007, and the isolated strains were used for antimicrobial susceptibility testing by broth microdilution method, virulence genes detection by PCR and molecular typing by pulsed-field gel electrophoresis (PFGE).

  Results  From 2016 to 2020, a total of 2 053 anal swabs from patients with diarrhea were collected, and 155 strains of V. parahaemolyticus were isolated. The average detection rate was 7.55%. The detection rate was statistically higher in summer and autumn (11.80%) than in winter and spring (0.13%) (χ²=92.725, P<0.01). The detection rate in 2019 was higher (10.55%) than those in other years, and there was a significant difference compared with 2016 and 2020 (χ²=8.890, P<0.05), but there were no significant differences in detection rate among five years (χ²=4.602, P>0.05). All the 155 V. parahaemolyticus strains carried virulence gene tlh, 87.74% carried tdh, 2.58% carried trh, and 8.39% carried no tdh and trh. The differences were significant (χ²=317.890, P<0.01). V. parahaemolyticus was sensitive to various antibiotics, and the resistance rate to cefazolin was highest (56.25%). Some strains were resistant to ampicillin and ciprofloxacin, and 3 strains were multi-drug resistant. PFGE molecular typing results showed that there were 7 clusters of V. parahaemolyticus, with 80 PFGE types. Some strains isolated from 2016 to 2020 shared 100% homology, and they were predominant strains.

  Conclusion  The detection rate of V. parahaemolyticus was high in patients with diarrhea in Songjiang district of Shanghai. Most strains detected carried virulence gene tdh, and they were highly resistant to cefazolin. The predominant strains clustered within five years, to which attention must be paid.