Drug resistance and genomic characteristics of Salmonella enterica serovar London from clinical and food sources in Hangzhou City from 2017 to 2021 / 中华预防医学杂志

Objective: To analyze the drug resistance and genomic characteristics of Salmonella enterica serovar London isolated from clinical and food sources in Hangzhou City from 2017 to 2021. Methods: A total of 91 Salmonella enterica serovar London strains isolated from Hangzhou City from 2017 to 2021 were analyzed for drug susceptibility, pulsed field gel electrophoresis (PFGE) typing and whole genome sequencing. Multilocus sequence typing (MLST), core genome multilocus sequence typing (cgMLST) and detection of drug resistance genes were performed by using the sequencing data. Phylogenetic analysis was conducted to compare the 91 genomes from Hangzhou City with 347 genomes from public databases. Results: No significant difference in the drug resistance rate was observed between clinical strains and food strains to 18 drugs in Hangzhou City(all P>0.05), and the multidrug resistance (MDR) rate was 75.8% (69/91). Most strains were resistant to 7 drug classes simultaneously. One strain was resistant to Polymyxin E as well as positive for mcr-1.1, and 50.5% (46/91) of the strains were resistant to Azithromycin and were positive for mph(A). All 91 Salmonella enterica serovar London strains were ST155, which were subdivided into 44 molecular types by PFGE and 82 types by cgMLST. Phylogenetic analysis showed that most strains from Hangzhou City (83/91) were clustered together, and a small number of human isolates from Europe, North America and pork isolates from Hubei and Shenzhen were mixed in the cluster. Other strains from Hangzhou City (8/91) were closely related to strains from Europe, America and Southeast Asia. Strains isolated from pork were the most closely related to clinical strains. Conclusion: The epidemic of Salmonella enterica serovar London in Hangzhou City is mainly caused by the spread of ST155 strains, which is mainly transmitted locally. At the same time, cross-region transmission to Europe, North America, Southeast Asia, and other provinces and cities in China may also occur. There is no significant difference in the drug resistance rate between clinical strains and food strains, and a high level of MDR is found in the strains. Clinical infection of Salmonella enterica serovar London may be closely related to pork consumption in Hangzhou City.

Molecular characteristics and antibiotic resistances of Vibrio cholerae O1 isolates in Hangzhou in 2009 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the molecular characteristics and antibiotic resistances of Vibrio cholerae (V. cholerae) O1 isolates in Hangzhou in 2009.</p><p><b>METHODS</b>The virulence genes ctxA and tcpA of the thirty V. cholerae O1 isolates from 7 counties and districts of Hangzhou were detected by PCR. Pulsed-field gel electrophoresis (PFGE) was performed for molecular typing and similarity analysis. Antibiotic resistances of these isolates were measured by the Kirby-Bauer method.</p><p><b>RESULTS</b>Virulence gene analysis showed that 80.00% (24/30) of the genotype in V. cholerae isolates was ctxA- and tcpA+, 13.33% (4/30) was ctxA- and tcpA-, and 6.67% (2/30) was ctxA+ and tcpA+. Twenty-seven isolates tested were typed into 11 PFGE patterns (P1-P11). Twenty-three isolates with genotype ctxA- and tcpA+ were clustered into 7 PFGE patterns (P1-P7, termed P1-like cluster) with the similarity to be equal or greater than 91.4%, and 56.52%(13/23) of them belong to P1. 7 isolates with very high similarity (97.6%), belonging to P1 (6 isolates), and P2 (1 isolate), respectively, were collected from one foodborne disease outbreak. The resistant rates of the 24 isolates with genotype ctxA- and tcpA+ to ampicillin, tobramycin and amikacin were 20.83% (5/24), 4.17% (1/24) and 4.17% (1/24), respectively.</p><p><b>CONCLUSION</b>The genotype of the epidemic strains of V. cholerae O1 isolates in Hangzhou in 2009 with high similarity was ctxA- and tcpA+; The level of drug resistances of this kind of V. cholerae O1 isolates were not high.</p>

Establishing a single-tube fluorescent bidirectional PCR method to detect the 609C/T polymorphism of NQO1 gene / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To develop a single-tube fluorescent bidirectional PCR method to detect the 609C/T polymorphism of NAD(P)H: quinone oxidoreductase 1 (NQO1) gene.</p><p><b>METHODS</b>Two primers of NQO1 gene C609T locus were designed. Using these primers, a SYBR Green I fluorescent bidirectional PCR, combined with melting curve analysis of the PCR products, were optimized to differentiate the 609C/T polymorphisms in 191 samples of human genomic DNA. The accuracy of the fluorescent bidirectional PCR was validated by the classical method of PCR-restriction fragment length polymorphism(RFLP) in 62 of these 191 samples.</p><p><b>RESULTS</b>In the 62 samples, the genotypes determined by the fluorescent bidirectional PCR were 100% consistent with the ones by the PCR-RFLP. The frequencies of genotypes of homozygous wild-type (CC), heterozygous (CT), and homozygous mutant (TT) were 28%, 50%, and 22%, respectively, in the 191 samples.</p><p><b>CONCLUSION</b>The single-tube fluorescent bidirectional PCR method established here provides a simple, rapid, accurate and inexpensive assay to determine the 609C/T polymorphism of NQO1 gene. The assay is suitable to detect the single nucleotide polymorphism in large-scale samples.</p>

Preparation of armored RNA containing M gene of influenza H3N2 / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To prepare the armored RNA containing M gene of influenza H3N2.</p><p><b>METHODS</b>The vector pAR-1 was constructed from expression vector pET30b in which the bacteriophage MS2 DNA fragment, containing the genes for maturase and coat protein and the pac site, was inserted. The M gene fragment of influenza A was inserted into the HindIII site downstream of the pac site on the pAR-1, which formed a new recombinant plasmid pAR-2. After the prokaryotic expression was carried out, armored RNA AR-2 containing M gene was obtained. AR-2 was purified, and then was quantified by real time RT-PCR. Moreover, the stability of AR-2 was checked.</p><p><b>RESULTS</b>AR-2 was expressed successfully. AR-2 remained stable under various storage environments. Approximately 8.9 x 10(11) copies of AR-2 particles can be purified from one milliliter of culture.</p><p><b>CONCLUSION</b>It showed that AR-2 was stable and RNase-resistant, which, as a virus surrogate, would be used as RT-PCR standards, controls and training or proficiency samples.</p>

Characteristics of virulence gene in Vibrio parahaemolyticus strains isolated from clinical patients and environment in Hangzhou, China / 中华预防医学杂志

<p><b>OBJECTIVES</b>To investigate the characteristics of virulence gene in Vibrio parahaemolyticus strains isolated from clinical patients and environment in Hangzhou, China.</p><p><b>METHODS</b>Thermostable direct hemolysin gene (tdh) and thermostable direct hemolysin-related hemolysin gene (trh) were determined in a total of 174 strains of V. parahaemolyticus isolated from patients and environment (seafood) in Hangzhou area by PCR.</p><p><b>RESULTS</b>The tdh was found in 92 out of 94 V. parahaemolyticus strains from food poisoning patients and in 33 out of 34 strains from sporadic diarrhea patients, and trh was not detected in all above clinical strains. Meanwhile the tdh was negative in all V. parahaemolyticus strains from environment, and the trh was also negative except one strain with urease activity. All strains with trh negative had no the activity of urease.</p><p><b>CONCLUSIONS</b>The V. parahaemolyticus strains from food poisoning patients and sporadic diarrhea patients are tdh positive and trh negative. The V. parahaemolyticus strains with tdh negative and almost trh positive in environment might be a potential pathogen in Hangzhou.</p>