Objective: Vibrio parahaemolyticus  is a major diarrhoea-inducing pathogen in coastal areas. In this study, we analysed the pathogenic characteristics of and variation in V. parahaemolyticus  isolated from acute diarrhoeal patients in seven hospitals in different areas of southeastern China from 2013 to 2017.
Methods: The fecal specimens of patients with acute diarrhoea were collected. The routine microbiological test procedure combining with MALDI Biotyper microbial identification system was carried out to identify the V. parahaemolyticus . Serum agglutination tests, PCR for the detection of virulence-related genes and the Kirby-Bauer method to test for antimicrobial sensitivity were performed.
Results: From 2013 to 2017 in southeastern China, a total of 1220 V. parahaemolyticus  strains were isolated from 16,504 stool specimens collected from acute diarrhoeal patients, and the annual isolation rate fluctuated between 6.1% and 8.7%. In total, 96.7% of the V. parahaemolyticus  isolates were isolated in summer and autumn, mainly in people aged 18– 44. Fifty-nine serotypes were identified, and the agglutination rate of the O antigen was 98.5%. From 2014 to 2016, the dominant serotype was O3:K6, while in 2013 and 2017, it was O4:KUT. The serotypes of O3:K6, O4:KUT, O4:K8, O3:KUT, O10:K60, O1:KUT and O1:K36 appeared every year from 2013 to 2017. O4:K6 and OUT:K6 began to appear after 2014 and 2015, respectively. A total of 49.5% of the strains belonged to the pandemic group, which consisted of 26 serotypes. Most isolates were sensitive to common antibiotics, excluding ampicillin.
Conclusion: V. parahaemolyticus  is still present at a high level in southeastern China. Although the pandemic O3:K6 serotype is predominant, new serotypes continue to emerge, especially the O4:KUT serotype, which exceeded O3:K6 in prevalence in some years. Long-term surveillance is necessary to prevent the outbreak or transmission of this pathogen.
Keywords: Acute diarrhoea, Vibrio parahaemolyticus , serotypes, virulence genes, antimicrobial resistance