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ObjectiveTo trace Bacillus cereus （B. cereus） from foodborne disease outbreaks toidentify pathogens and cut off transmission.MethodsPulsed-field gel electrophoresis （PFGE） was performed. Furthermore， 12 isolates of B. cereus were subjected to PFGE. Subsequently， whole-genome sequencing （WGS） analysis was conducted on ten of these isolates. The WGS data were analyzed and assembled using BioNumerics software. Multilocus sequence typing （MLST）， virulence gene profiles， and single nucleotide polymorphisms （SNPs） were analyzed using assembled sequences.ResultsPFGE analysis classified the 12 B. cereus strains into nine pulsotypes. The three B. cereus isolates with the same PFGE pattern belonged to ST1435， and there were only three SNPs in the three ST1435 strains. The two B. cereus isolates with the same PFGE patterns were ST24 with one SNP between them， and the two ST24 isolates harbored hlbACD. These results indicate that the B. cereus isolates belonged to the same clone. The remaining three B. cereus strains also contained hlbACD.ConclusionFood-borne illness events caused by B. cereus are complex and are sources of contamination. Therefore， it will be necessary to strengthen the hygiene surveillance of food sources and workers and to pay more attention to cleaning and disinfecting environments and facilities， which will be important for preventing and controlling foodborne diseases.

ObjectiveThis study aimed to analyze the molecular characteristics and antibiotic resistance of diarrheagenic Escherichia coli （DEC） from meat and aquatic products in Shanghai City.MethodsThe DEC isolates were characterized by applying antibiotic tests and whole genome sequencing （WGS）. The BioNumerics software was used to analyze and assemble WGS data. Then， multilocus sequence typing sequencing， virulence profiles， and antibiotic-resistant genes were analyzed adopting assembled genome sequences. The antimicrobial susceptibility was investigated.ResultsIn this study， most DEC isolates were EAEC （73.2%）， and most of the EAEC isolates carried only the astA gene （90.2%）. All 56 DEC isolates have been typed as 37 STs. The resistance rate to NAL was higher （64.3%），followed by aminoglycoside， beta-lactam， and tetracycline. The multi-drug resistant DEC isolates were 48.2% resistant； furthermore， the resistance genes were detected in these DEC isolates.ConclusionEAEC isolates are dominant DEC isolates from foods in Shanghai City. Furthermore， these DEC isolates exhibited a higher resistance rate， compared with the corresponding resistance genes. These results suggest that molecular surveillance should be enhanced. Moreover， fundamental data can be obtained by employing the WGS for tracing DEC isolates and analyzing pathogenicity.

ObjectiveTo evaluate the equivalence of 5 Salmonella selective enrichment procedures in standard methods worldwide.MethodsThe growth rates（PR） and the colony characteristics of 5 selective enrichment broths（SC， TTB， RV， MKTTn， SBG） and 5 selective mediums（CAS， XLD， XLT4， HE， BS） were validated according to the GB4789.28—2013. The sensitivity（SE）， the relative trueness（RT） and the acceptable limit（AL） were estimated on highly contaminated foods through the use of 5 protocols combined with 5 selective enrichment broths and 2 selective mediums according to the method of ISO 16140—2：2016. The sensitivity（Se）， the specificity（Sp）， the positive predictive value（PPV） and the negative predictive value（NPV） were simultaneously determined through the use of 10 compound modes combined with selective enrichment broths and selective mediums according to the classical statistical methods.ResultsThe results showed that SC broth had no efficacy in enriching Salmonella enterica serotype Cholerae and Salmonella enterica serotype Cholerae var. Kunzendorf. The CAS and XLD were significantly better than XLT4， HE and BS in identifying typhoidal Salmonella and nontyphoidal Salmonella as well as the phenotype of hydrogen sulfide.Totally 84 samples（22 pieces of meat， 32 pieces of poultry and 30 pieces of aquatic products） were tested. 25 out of the 84（29.76%） were confirmed positive by 5 protocols， and 16 serotypes from 42 isolates were identified. The SE of 5 protocols were 84.00%， 100.00%， 88.00%，88.00% and 92.00%， respectively， but showed no statistically significant difference between each other. The AL of one protocol （SC+TTB） went beyond the limitation of the ISO 16140—2：2016 due to the ineffectiveness of SC broth. The compound mode of RV-CAS had the best comprehensive benefits， while the Se， the Sp， the PPV and the NPV of which were 68.00%， 95.00%， 85.00% and 88.00%， respectively.ConclusionThe ineffectiveness of SC broth reduces the sensitivity of the detection protocol for Salmonella， which could cause a negative deviation， resulting in the threshold exceeding of the Acceptability Limit （AL）. The combinational selective enrichment broth of RV-CAS is recommended to be the optimal mode， with CAS+XLD being recommended to be the optimal selective medium combination. The process of Salmonella serotyping is suggested to be improved in the standard of GB4789.4 to cope with the multi-serotype Salmonella contamination in food chain and be consistent with the international standardization for food microbiology.

ObjectiveTo study the molecular characteristics and antibiotic resistance of Bacillus cereus (B. cereus) from foods in Shanghai.MethodsThe B. cereus isolates were characterized using antibiotic susceptibility tests and whole genome sequencing (WGS). BioNumerics software was used to analyze and assemble WGS data. Then, multilocus sequence typing (MLST), virulence genes profiles and antibiotic resistant genes were analyzed using assembled genome sequences. The antimicrobial susceptibility was investigated. Furthermore, STs of B. cereus in this study were compared with those from PubMLST database.ResultsIn this study, all 37 isolates were confirmed as B. cereus isolates. The 37 B. cereus were typed into 34 STs with 7 new STs. The result of STs showed high diversity. All 37 B. cereus isolates had nheA, nheB and nheC genes. The positive rate of hblACD genes was 37.8%. However, only 16.2% of B. cereus had ces genes. Furthermore, two ST26 B. cereus isolates with ces genes from ready-to-eat food were identified. The antibiotic resistance rate to Ampicillin, Penicillin and Oxacillin was high, which was not consistent with antibiotic resistant genes.ConclusionThe STs of 37 B. cereus from food in Shanghai showed high genetic diversity, which suggested the molecular surveillance should be enhanced. Fundamental data can be obtained using whole genome sequencing for tracing B. cereus isolates and analyzing pathogenicity.

Vibrio parahaemolyticus is a major foodborne pathogen in China and other countries. In this study, a total of 578 clinical V. parahaemolyticus strains and 51 foodborne strains were isolated during the period from 2009 to 2011 in the eastern coastal city of Shanghai, China. Their serotypes, virulence genes, pandemic traits, and genotyping were investigated. A total of nine O groups and 20 K types were identified by serological analysis of all isolates. Six different O groups and 14 different K types were detected among the 578 clinical strains. Eight different O groups and five K types were detected among the 51 foodborne strains. The O3:K6 serotype was the dominant serotype. A total of 200 representative clinical strains and 51 foodborne isolates were analyzed for virulence genes, pandemic traits, and genotyping. Of the clinical strains, 92.5% had the virulence genes tdh and/or trh. Four foodborne isolates had virulence genes; one trh-positive strain was O3:K6 and three tdh-positive strains were either O4:KUT or O3:KUT. Molecular typing by pulsed-field gel electrophoresis also showed divergence among the nonpandemic strains, although the pandemic strains formed a cluster. These results suggest high serodiversity and genetic diversity of V. parahaemolyticus. Pathogenic isolates were present in food, thus representing a public health risk and warranting epidemiological and ecological monitoring to ensure safety.