Antimicrobial resistance and genomic characteristics of Salmonella enterica serovar Derby isolates from clinical patients and food sources in Hangzhou / 中华微生物学和免疫学杂志

Objective:To analyze the antimicrobial resistance and genomic characteristics of Salmonella enterica serovar Derby strains isolated from human and food sources in Hangzhou. Methods:A total of 60 Salmonella enterica serovar Derby strains isolated in Hangzhou during the period from 2015 to 2020 were subjected to antimicrobial susceptibility testing, pulsed field gel electrophoresis (PFGE) typing and whole-genome sequencing. Multilocus sequence typing (MLST), core genome multilocus sequence typing (cgMLST) and the identification of antimicrobial resistance genes were performed using the sequencing data. Phylogenetic tree based on the single nucleotide polymorphism (SNP) sites in the 60 genomes from Hangzhou and 379 genomes from public databases was constructed. Results:No significant difference was observed in the drug resistance rates between the clinical strains and food strains in Hangzhou. The multidrug resistance (MDR) rate was 76.7% (46/60). All of the 60 Salmonella Derby strains were positive for the antimicrobial resistance genes aac(6′)- Iaa and fosA7. The 60 strains were subtyped into 46 molecular types by PFGE and 53 molecular types by cgMLST(HC2). Except for one strain belonging to ST3220, the other Salmonella Derby strains were ST40. The phylogenetic analysis showed that some strains isolated in Hangzhou were close to the strains in Southeast Asia, suggesting the possibility of cross-border transmission of ST40 strains, with the main food sources being pork and fish; other strains were close to those circulating in Beijing, Guangzhou, Hubei, Chongqing and other provinces, suggesting the possibility of cross-province transmission of the strains, with the main food sources being pork, beef and chicken. Conclusions:The epidemic of Salmonella Derby in Hangzhou was mainly caused by the spread of ST40 strains and MDR was common. Clinical infections might be closely related to the consumption of pork, beef, chicken and fish. There was the possibility of cross-border transmission of Salmonella Derby between Hangzhou and Southeast Asia and cross-province transmission in China.

In vitro inhibitory effects of emodin on Staphylococcus aureus biofilm formation / 中华微生物学和免疫学杂志

Objective:To investigate the effects of emodin on Staphylococcus aureus ( S. aureus) biofilm formation and disruption. Methods:ATCC6538 and S. aureus 16-22 were used in this study. The minimum inhibitory concentrations (MICs) of emodin against the two strains were detected by the standardized agar dilution method. After an in vitro biofilm model was established, silver staining method was used to observe the bacterial cell morphology; crystal violet staining and double dilution method were performed to measure the viable count of bacteria in biofilms. Results:The MICs of emodin against ATCC6538 and 16-22 were 32 μg/ml and 16 μg/ml, respectively. The bacterial cell morphology showed that ≥4 μg/ml emodin effectively reduced the adherence of S. aureus to the plate and destroyed mature biofilms. The results of crystal violet staining and double dilution method showed that when the concentration of emodin reached to 8 μg/ml, 75% of ATCC6538 and 70% of 16-22 failed to form biofilms and 56% of the mature biofilms on the plate were broken. Conclusions:Emodin could effectively inhibit the biofilm formation and destroy the mature biofilms of S. aureus in vitro.

Analysis of genomic characteristics and virulence factors of emetic-type Bacillus cereus strains isola-ted in Hangzhou / 中华微生物学和免疫学杂志

Objective To investigate the genomic characteristics and virulence factors of emetic-type Bacillus cereus strains isolated from food in Hangzhou for better understanding their pathogenic potential. Methods Real-time PCR was performed to detect the ces gene cluster ( cereulide) in 132 Bacillus cereus strains isolated from food from 2015 to 2017. Genomes of cereulide-positive strains were sequenced using Illumina MiSeq sequencing platform. Genome annotation, virulence factor detection, comparative and evolu-tionary analysis were performed after the sequences of genomes were assembled. Results Twelve strains (9. 09％) carried the ces gene. Their genome sizes ranged from 5. 35 to 5. 75 Mb and GC contents from 35. 25 to 35. 43 mol％. All of them harbored the full cereulide biosynthesis gene cluster, nonhemolytic ente-rotoxin ( NHE)-encoding gene cluster ( nheA, nheB and nheC) and hemolysinⅢ( hlyⅢ) . The average nu-cleotide identity ( ANI ) between the 12 isolates and the reference strain NC7401 ( Accession number:AP007209) was over 99. 35％. Phylogenetic analysis demonstrated these strains were clustered into the same branch with local clinical isolates and the emetic-type Bacillus cereus strains of NC7401 and AH187. Con-clusions The genomic sequences of the emetic-type Bacillus cereus strains isolated from food in Hangzhou area were highly similar to that of the reference strain NC7401. Results of the genomic analysis suggested that these isolates carried many virulence factors that were related to pathogenicity.

Preliminary application of next generation sequencing technique in pathogen identification of foodborne disease / 中华预防医学杂志

Objective@#To analyze genomic features of pathogens based on next generation sequencing technique in a food-borne disease event.@*Methods@#A total of 11 blood samples, stomach contents before gastric lavage from the death and patients' foods were collected. S. aureus, B. cereus and toxic substances were detected. B. cereus detected in foods were counted. The conserved region of 16 S rDNA gene and ces gene(cereulide) of B. cereus isolates were detected by real-time PCR. Next Generation Sequencing (NGS) technology was applied to acquire genome sequences of isolates. Different plasmids distribution and comparative genomics analysis with reference sequences in public databases were analyzed.@*Results@#Only B. cereus tested positive in all samples. The counts of B. cereus in Egg fried rice, one food samples, were 1.9×107 CFU/g, and the counts of B. cereus in dried and fried fish and brine pork head meat samples were 3.0×103 CFU/g both. Ten isolates were carrying hlyⅢ, nheA, nheB, inlA and inhA genes, and nine isolates carried the plcR gene and nine isolates carried the nheC gene. The PCR result of 16 S rDNA gene and ces gene of all isolates were positive. All carried the complete ces genes cluster sequence which were identical to the sequence of plasmid pCER270 (NC_01 0924.1) from strain AH187 in United Kingdom and pNCcld (NC_016792.1) from NC7401 in Japan. The alignment of plasmids turned out the sequence of the isolate differed from the pXO1 and pXO2 plasmids of B. anthracis, but carried the pNCcld plasmid containing the ces genes cluster. The phylogenetic tree based on genomic sequences of ten isolates showed high similarity (distances in phylogenetic tree from 2.0×10-6-9.0×10-6) to each other and to the B. cereus strains AH187 and NC7401 (MLST ST26 type, distances in phylogenetic tree from 3.8×10-5-4.5×10-5).@*Conclusion@#The foodborne disease event was caused by vomiting type Bacillus cereus without plasmid pXO1 and pXO2 contaminated egg fried rice. The vomiting-type food poisoning caused by B. Cereus globally is probably associated with ST26, ST164 and other strains harboring ces gene.

Molecular characteristics of Listeria monocytogenes foodborne isolates in Hangzhou, China / 中国人兽共患病学报

We determined molecular characteristics of Listeria monocytogenes foodborne isolates in Hangzhou and investigated the characterization of local strains.Multi-locus sequence typing(MLST) and pulsed-field gel electrophoresis(PFGE) were applied to identify molecular types of Listeria monocytogenes isolates.Results showed that a total of 133 strains of 6 serotypes were divided into 19 MLST types including a new type ST767.ST9 and ST121 were the major ST types.There were 33 and 45 PFGE patterns characterized by AscⅠ and ApaⅠ.The molecular types of Listeria monocytogenes strains were widely distributed in Hangzhou.It is indicated that the major clusters were Lineage Ⅰ and Lineage Ⅱ which will cause listeriosis.The contamination of Listeria monocytogenes in food is serious in Hangzhou and the surveillance and management should be strengthened to prevent the food borne diseases.

Trojan Peptides Based Nucleic Acids Delivery / 医学研究杂志

Trojan peptides,also named cell-penetrating peptides or protein transduction domains,are a class of small cationic peptides that often contains less than 30 amino acids.They can deliver a wide range of "cargos" such as peptides,proteins and nucleic acids efficiently through the cellular membrane.This review mainly focuses on the recent progress on utilizing Trojan peptides to deliver plasmid DNA and siRNA into cells in vitro and in vivo,and also highlights the implications of this technology in both gene function study and therapeutic potential.