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Vibrio parahaemolyticusis an important foodborne pathogen with diverse serotypes. In May 2021, we investigated a gastroenteritis outbreak that occurred in China, caused by V. parahaemolyticusO10:K4 infection. Based on the epidemiological curve, this outbreak was identified as a homologous exposure event. A case-control study demonstrated that emperor crab with mashed garlic (odds ratio [OR] = 4.60, p= 0.030; 95% confidence interval [95% CI]: 1.11–19.14), goose liver geoduck (OR = 4.50, p= 0.029; 95% CI: 1.12–18.13), shrimp (OR = 4.89, p= 0.021; 95% CI: 1.22–19.65), and sea cucumber (OR = 7.36, p= 0.005; 95% CI: 1.68–32.26) were the potential sources of the food poisoning. V. parahaemolyticusisolates from 18 laboratory-confirmed cases were all serotyped O10:K4, and determined to be sequence type ST3 via multilocus sequence typing. Pulsed field gel electrophoresis and whole-genome sequencing analysis revealed the identical pattern and 0–2 single nucleotide variation among these isolates. tdhwas positive in all isolates, while trhand Orf8 were absent. Seven essential base positions in toxRSfor pandemic clone identification were identical between the O10:K4 and O3:K6 pandemic clones. Phylogenetic analysis with 45 additional genomes of 13 different serotypes showed the closest genetic relationship between O10:K4 and O1: KUT. O10:K4 was thought to evolve from the O3:K6 pandemic clone. The new serovariant of O3:K6 poses a challenge for the prevention and control of V. parahaemolyticusdisease outbreaks, or even epidemics, in the future.

Objectives:The previous researches revealed that Vibrio parahaemolyticushas been detected in freshwater fish samples. However, the molecular characteristics of V. parahaemolyticusisolated from freshwater fish, including pathogenic and pandemic strains, are still unknown. This study aims to characterize and identify molecular properties of the bacterium. In addition, it identifies the source of V. parahaemolyticusfrom freshwater fish samples in Zhejiang Province, China.Methods:Four hundred and twenty-one freshwater fish samples (from fishing farms, retail markets, and restaurants) and 212 seafood samples (from retail markets) were collected in 10 cities of Zhejiang Province. V. parahaemolyticusstrains were isolated from these samples and comparatively analyzed by multilocus sequence typing, serotyping, antimicrobial susceptibility test, and polymerase chain reaction, targeting common toxin genes (tdh, trh) and markers for pandemic strains (orf8, toxRS/new).Results:Sixty-eight V. parahaemolyticusstrains were isolated from the 421 freshwater fish samples, and 89 V. parahaemolyticusisolates were identified out of 212 seafood samples. The detection rate of V. parahaemolyticuswas significantly different (p< 0.05) between the fishing farms, the retail markets, and the restaurants. The isolates from freshwater fish samples were divided into eight O serotypes with three O3:K6 isolates, which contain three pandemic complexes (tdh+, orf8+, toxRS/new+). A total of 53 different sequence types (STs) were identified among the 68 isolates, including 28 novel STs. Antimicrobial susceptibility results indicated that 76.5% of the strains were resistant to ampicillin. A third (3/9) of the isolates from fishing farm sources shared the same STs with their counterparts from retail markets. Compared with the isolates from the seafood samples collected in the same sampling sites, 13.2% (9/68) freshwater fish isolates overlapped with seafood isolates.Conclusions:Our study showed that V. parahaemolyticuspopulation in freshwater fish is genetically diverse. The V. parahaemolyticuscontaminates might have come from both fishing farm sources and cross-contamination from seafood in the closed area at the markets. Freshwater fish may work as a reservoir of pathogenic and pandemic V. parahaemolyticusisolates, indicating potential public health and food safety risks associated with the consumption of freshwater fish.

Campylobacteris well recognized as the leading cause of bacterial foodborne diarrheal disease worldwide with a very low outbreak reported in China. In May 2019, we investigated an outbreak of Campylobacter jejuniinfections among students in a junior high school in Eastern China. Cases were interviewed to identify a common source of contamination. As cases were identified in the same school during a period of time, menus were reviewed and food items included in the questionnaire. Rectal swabs from school kitchen staff and suspected food items (raw chicken) from a local market from where the school food came were examined for C. jejuni. Pulsed-field gel electrophoresis and whole genome sequencing were performed to determine the relatedness of the isolates. To identify the source of the contamination, a case–control study was conducted. Forty-five cases were reported with diarrhea among 1696 students and staff. Stool samples for 10 of the 45 and 5 tested positive for C. jejuni. WGS analysis revealed a 0–4 single nucleotide variation in case-patient isolates. Although we were unable to identify the specific food item, a specific menu was identified as the potential source of the contamination (odds ratios = 20.82; 95% confidence interval = 6.472–66.957). In this menu, chicken was served. A food isolate collected from chicken in Zhejiang province in 2018 was positive for the same identical strain (5–7 single nucleotide polymorphisms). This is one of the few reports in China about outbreak caused by C. jejuni. This investigation illustrates the potential risk of outbreaks caused by Chinese cold dishes of chicken.

AbstractBacillus cereusis an important foodborne pathogen, which can cause severe food poisoning. The aim of this study was (i) to evaluate the quantitative prevalence of B. cereusin retail prepackaged infant formula and ready-to-eat rice flour in China and (ii) to gain the basic information on pheno- and genotypic characteristics of B. cereusisolates. We found that 40 out of the 587 samples were positive for B. cereus. B. cereusin 3.5% of infant formula samples and 1.0% of rice flour samples outnumbered 100 Colony-Forming Units (CFU)/g. B. cereuslevel even attained 103–104CFU/g in four infant formula samples and one rice flour sample. Furthermore, we identified the distribution patterns of toxin genes in B. cereusisolates. The results showed that 97.5% of B. cereusisolates harbored at least one enterotoxin gene. Antibiotic susceptibility tests revealed that all isolated B. cereusstrains were resistant to penicillin and 50% of them were multidrug resistant. Thirteen new sequence types (STs) and four new alleles were identified via multilocus sequence typing. Clonal Complex (CC) ST-205 and CC ST-142 were predominant clonal complexes. Interestingly, we revealed the special relationship between STs of B. cereusisolates and the geographical distributions of infant food manufacturers for the first time. The data implied that B. cereusof different STs might have a distinct ecological niche in China. In view of relatively high contamination level of enterotoxin- producing B. cereusin a proportion of infant foods, especially in those suitable for the ≤6-month-old infant group, appropriate safety criteria and hygienic control measures for infant foods should be drafted in China to prevent B. cereusinfection.