Etiology analysis of an acute gastroenteritis outbreak caused by co-infection with Vibrio parahaemolyticus and non-O1/O139 Vibrio cholerae

ObjectiveTo analyze an acute gastroenteritis outbreak caused by co-infection with Vibrio parahaemolyticus （V. parahaemolyticus） and non-O1/O139 Vibrio cholerae （V. cholerae）.MethodsFour anal swabs， 12 food samples， and 8 environmental samples enriched in liquid culture media were subjected to pathogen screening with real-time PCR. V. parahaemolyticus and V. cholerae strains isolated were subjected to whole genome sequencing， and virulence and antibiotic resistance genes were screened. Cladograms were constructed based on core genome single nucleotide polymorphisms.ResultsV. parahaemolyticus strains were detected in anal swab samples with real-time PCR that were toxRVP+/tdh+/trh-， and two of them were positive for V. cholerae. The positive rate of V. parahaemolyticus in the anal swab samples was 100% （4/4）， the isolates were toxRVP+/tdh+/trh-， and their serotype was O4：KUT. The positive rate of V. cholerae culture in the anal swabs of patients was 50% （2/4）. The serogroup of the isolates was non-O1/O139， and one of them was toxRVC+/ctx/t3ss+. The positive rate of V. parahaemolyticus in the food samples was 66.67% （8/12）， and that in the environment samples was 12.50% （1/8）. The strains isolated from food and environmental samples were toxRVP+/tdh-/trh-. The positive rate of V. cholerae culture in the food samples was 25.00% （3/12） and the isolated strains were toxRVC+/ctx/t3ss-. The V. parahaemolyticus strains isolated from patient， food， and environment samples formed 10 distinct lineages. The four patient isolates were highly clonal. The V. cholerae strains isolated from two patients and three food samples formed five distinct lineages.ConclusionThe outbreak was caused by co-infection with V. parahaemolyticus and non-O1/O139 V. cholerae. Real-time PCR and whole-genome sequence analysis of strains should be performed in the detection and analysis of outbreaks caused by vibrio co-infection. Additionally， optimization of vibrio culture pathways is recommended.