An acute gastroenteritis outbreak associated with breakfast contaminated with norovirus by asymptotic food handler at a kindergarten in Shenzhen, China.

BACKGROUND: An outbreak of acute gastroenteritis occurred in a kindergarten located Shenzhen City on March 4, 2018. We were invited to investigate to the risk factors associated with this outbreak. METHODS: We conducted retrospective cohort-studies on three different groups of subjects in order to figure out the difference of incidence of acute gastroenteritis among subjects of different activities on March 2: group one consisted of people who attended the Lantern festival activities; group two consisted of children and employees who ate breakfast and bread provided by the kindergarten; and groups three consisted of children and employees who did not eat breakfast or bread provided by the kindergarten. Fecal, anal swabs, dishware swabs and hand swabs specimens were collected in the study. Bacteria known to cause acute gastroenteritis were cultured. Viruses associated with acute gastroenteritis were tested using real-time PCR. Capsid gene fragment of 557 bp of norovirus was amplified and sequenced. The phylogenetic tree was constructed with MEGA 7.0 using neighbor-joining method based on capsid gene fragment of norovirus. RESULTS: A total of 143 suspected cases were identified in this outbreak. Diarrhea happened more often in adults than in children while emesis and bellyache were more frequently found in children than in adults. Higher AGE incidence was observed in group 2, children and employees who had breakfast in the kindergarten on March 2, as well as in group 3, and among employees who eating bread involved in breakfast provided on March 2. Five anal swab specimens were positive for norovirus. All noroviruses belongs to group II.3 and have an identity more than 99%. CONCLUSION: A chef, as an asymptomatic carrier with norovirus, was the infectious resource in this outbreak. He contaminated breakfast food provided on March 2. Although morning check is implemented in kindergartens of China, employees are often excluded in morning check. Our finding highlights the importance of morning check covering employees and periodical training for cooks.

[Multiple-locus variable number tandem repeat analysis of Staphylococcus aureus in one food poisoning case].

OBJECTIVE: To type Staphylococcus aureus strains from a food poisoning case by MLVA method, detect staphylococcal enterotoxin, and provide lab evidence for molecular epidemiological study and analysis of evolution. METHODS: The genomic DNA of 10 stains in the food poisoning case were used as PCR template. Eight pairs of primers were selected from the MLVA database. The PCR method was carried out and the PCR products were analyzed by capillary electrophoresis. The results were analyzed by BioCalculator and compared with the MLVA database. The staphylococcal enterotoxin was detected with colloidal gold method. RESULTS: The 8 VNTR PCR products have no differernce in the 10 strains, the size of VNTR09_01, VNTR61_01, VNTR61_02, VNTR67_01, VNTR21_01, VNTR24_01, VNTR63_01 and VNTR81_01 are 373, 361, 328, 279, 845, 354, 394 and 658 bp, respectively. The 10 strains belong to the same MLVA type, which is a new MLVA type differnernt from other 3892 strains in MLVA database, the MLVA profile is 15-2-2-2-35-8-2-7. Meanwhile, the 10 strains have the same kind of staphylococcal enterotoxin, the are enterotoxin A and enterotoxin B. CONCLUSION: The 10 Staphylococcus aureus strains are of one MLVA type, and have the same characters of staphylococcal enterotoxin. They have high homology.

[Genotypic and phenotypic analysis of hemolysis in foodborne Staphylococcus aureus].

OBJECTIVE: To establish a multiplex PCR method for detecting genes of (alpha-hemolysin (hla), beta-hemolysin (hlb), hemolysin and 16S rDNA, and to learn the distribution of three hemolysin genes and the characteristics of hemolytic phenotype in 148 foodborne Staphylococcus aureus strains, and to classify the strains with cluster analysis. METHODS: The multiplex PCR method was established and used to detect the genes of alpha-hemolysin, beta-hemolysin, hemolysin and 16S rDNA. The blood agar method was used to detect the characteristics of hemolytic phenotype. The experiment data was analyed with SPSS16.0. RESULTS: 131 strains were positive for hla gene (88.51%), 90 hlb gene (60.81%), 28 hemolysin gene (18.92%). 131 strains had the characteristics of hemolysis (88.51%), while the hemolysis were negative in 17 strains (11.49%). With the clustering factors of the hemolysin genotype and hemolytic phenotype, 148 strains were classified into 12 types from type A to type L with 100% similarity. Among them, type A contained 58 strains (39.19%), type B 37 (25.00%), type C 18 (12.16%). CONCLUSION: This multiplex PCR method is fast, convenient and specific, and could be used for high-throughput screening of hemolysin genes in S. aureus. Most of the foodborne Staphylococcus aureus strains carrying the hla gene mainly belong to type A and type B.

Molecular characterization of foodborne-associated Staphylococcus aureus strains isolated in Shijiazhuang, China, from 2010 to 2012.

Staphylococcus aureus is an opportunistic pathogen commonly identified from food poisoning-associated foodstuffs. From 1996 to the present, S. aureus isolates have been found to exhibit increasing resistance to antimicrobial drugs. The aim of this study was to assess the molecular epidemiology properties of various S. aureus isolates through molecular typing and to investigate their characterization based on their production of enterotoxins and hemolysins and their resistance to antibiotics. A total of 78 coagulase-positive staphylococcal strains isolated from food or clinical samples were analyzed. Eight VNTR loci were used to genotype the 78 isolates, and this analysis resulted in 39 different multilocus variable number tandem repeat analysis (MLVA) profiles. The isolates recovered from a single outbreak exhibited the same MLVA profile. According to CLSI, 97.4% of the isolates were resistant to penicillin, whereas only 3.8% were methicillin-resistant Staphylococcus aureus strains. Through multiplex PCR, 87.2% of the isolates were shown to be enterotoxigenic (SEs), and the most common genes present were sea, sem, seg, seu, and sek. In conclusion, this study demonstrates the prevalence of staphylococcal enterotoxins, the contents of virulent factors, and the characteristics of ß-lactam antibiotic resistance in 78 S. aureus isolates. These findings emphasize the need to prevent the presence of S. aureus strains and SE production in foods. Our results also demonstrate that MLVA is a useful and powerful method for epidemiological studies of S. aureus. In contrast to multilocus sequence typing, the MLVA method is a simpler and more rapid method for epidemiological typing with a higher discriminatory power.