Molecular epidemiology of Listeria monocytogenes isolated from ready-to-eat food in 2017 in China / 中华预防医学杂志

To analyze the molecular characteristics of strains from ready-to eat food in China. A total of 239 strains isolated from ready-to-eat food in 2017, all strains underwent whole-genome sequencing (WGS) , and comparisons uncovered population structure derived from lineages, clonal complex, serogroups, antimicrobial susceptibility and virulence, which were inferred in silico from the WGS data. Core genome multilocus sequence typing was used to subtype isolates. All strains were categorized into three different lineages, lineage Ⅱ was the predominant types in food, and IIa was the main serogroups. CC8, CC101 and CC87 were the first three prevalent CCs among 23 detected CCs, accounting for 49.4%. Only 4.6% (11 isolates) of tested strains harbored antibiotic resistance genes, which were mostly trimethoprim genes (7 isolates, 2.9%). All strains were positive for LIPI-1, and only a part of strains harbored LIPI-3 and LIPI-4, accounting for 13.8% (33 isolates) and 14.2% (34 isolates), respectively. ST619 carried both LIPI-3 and LIPI-4. 51.5% (123 isolates) of strains carried SSI-1, and all CC121 strains harbored SSI-2. Different lineages, serogroups and CCs can be separated obviously through cgMLST analysis, and 24 sublineages were highly concordant with CCs. Ⅱa was the main serogroups in ready-to-eat food isolates in China; CC8, CC101 and CC87 were the prevalent CCs, and CC87 isolates was hypervirulent isolates, cgMLST method can be adopted for prospective foodborne disease surveillance and outbreaks detection.

Role of Treg in the immune pathogenesis of subacute thyroiditis / 基础医学与临床

Objective To explore the role of regulatory T-lymphocytes(Treg) in the immune pathogenesis of suba-cute thyroiditis (SAT). Methods The proportion of Treg in CD4+T cells in peripheral blood of 46 SAT patients and15 controls was detected using flow cytometry. And the concentration of interleukin-10(IL-10), transforming growth factor-beta1(TGF-β1) and prostaglandin E2(PGE2) in serum of 46 SAT patients and 15 controls was measured with ELISA. In addition, the Forkhead box protein 3 (Foxp3) positive cells in thyroid tissue of 29 SAT patients and20 controls was detected by immunohistochemistry. Results The proportion of Treg in peripheral blood of SAT pa-tients was significantly lower than that of controls (P＜0.05). And the concentration of TGF-β1 in serum of SAT patients was apparently higher than that of controls(P＜0.05). Additionally, the positive rate of Foxp3 in thyroid tissue of SAT patients was markedly higher than that of controls(P＜0.05).Conclusions The decrease of Treg may play an important role in the immune pathogenesis of SAT.

The Survey of Cronobacter spp. (formerly Enterbacter sakazakii) in Infant and Follow-up Powdered Formula in China in 2012 / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To determine Cronobacter spp. contamination in infant and follow-up powdered formula in China.</p><p><b>METHODS</b>All of 2282 samples were collected from the retail markets in China from January 2012 to December 2012, and analyzed for Cronobacter spp. by the Chinese National Food Safety Standard. Characterization of the isolates was analyzed by pulsed-field gel electrophoresis (PFGE) with XbaI and SpeI restriction enzymes.</p><p><b>RESULTS</b>Cronobacter spp. strains were isolated from 25 samples, and the positive rates in infant powdered formulas and follow-up powdered formulas were 0.90% (10/1011) and 1.18% (15/1271), respectively. Analysis of variable data regarding different purchasing store formats, seasonality, and production locations as well as comparison of infant versus follow-up formulas did not reveal statistically significant factors. During the sampling period, one of six surveillance zones did exhibit a statistically significant trend towards higher positive rate. PFGE characterization of Cronobacter spp. to elucidate genetic diversity revealed only three pairs of Cronobacter spp. out of 25 having the same PFGE patterns.</p><p><b>CONCLUSION</b>The current investigation indicated a lower positive rate of Cronobacter spp. in the powdered formula in China. This evidence suggested contamination originating from multiple different sources during the manufacturing process.</p>

Prevalence and antibiogram distribution of Salmonella isolated from broiler production and processing course in four provinces, China / 中华预防医学杂志

<p><b>OBJECTIVE</b>To determine the contamination condition of Salmonella in broiler breeding and slaughter processing in China and to investigate the distribution of antimicrobial resistance profiles.</p><p><b>METHODS</b>Five large-scale broiler holdings and fourteen slaughterhouses were chosen to detect Salmonella in Henan, Jiangsu, Sichuan and Shandong provinces in 2010. A total of 835 anal swabs and 744 chicken carcasses were sampled to compare the difference of Salmonella contamination rate.Salmonella isolates were identified by serotyping according to Kauffmann-White scheme.The antimicrobial susceptibilities of Salmonella isolates were determined by broth microdilution method and sixteen antimicrobial agents were chosen and examined.</p><p><b>RESULTS</b>In total, Salmonella isolates were recovered in 56 (6.7%) specimens among 835 collected anal swabs and 122 (16.4%) specimens among 744 broiler carcasses. Positive rate of Salmonella in broiler carcasses was higher than anal swabs (χ(2) = 36.94, P < 0.05). The dominant Salmonella serovars isolated from broiler anal swabs were S.enterica serovar Indiana and S.enterica serovar Enteritidis, accounting for 58.9% (33/56) and 32.1% (18/56) respectively. The prevalent serovars in broiler carcasses were also the two serovars and occupied 29.8% (37/124), 32.2% (40/124) respectively. Nearly 95.0% (171/180) Salmonella isolates were resistant to at least one antimicrobial, 78.3% (141/180) Salmonella strains were multi-drug resistant isolates and 20 (11.1%) Salmonella isolates were resistant to 14 antimicrobials.</p><p><b>CONCLUSION</b>Our findings indicated that Salmonella contamination was common and serious in commercial broiler production and processing course in China. Salmonella contamination rate in broiler slaughter processing performance was higher than broiler flocks. Additionally, antibiotic resistance of Salmonella was in serious situation.</p>

Virulent gene prevalence of foodborne Listeria monocytogenes in China in 2005 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the virulent gene prevalence of foodborne Listeria monocytogenes (LM) isolated from China.</p><p><b>METHODS</b>78 LM isolates derived from raw meat, cooked food, aquatic products and vegetables of 13 provinces and cities.LM isolates were investigated for prevalence of virulence genes (LIPI-1 (prfA, plcA, hly, mpl, actA, plcB); LIPI-2 (inlA, inlB), and iap) by PCR method.</p><p><b>RESULTS</b>87.2% (68/78) of the isolates were prfA positive, 98.7% (77/78) of the isolates were plcA, actA and plcB positive, 97.4% (76/78) of the isolates were hly positive, 87.2% (68/78) of the isolates were mpl positive, 92.3% (72/78) of the isolates were inlA positive, 100% (78/78) of the isolates were inlB positive, 98.7% (77/78) of the isolates were iap positive. Among 21 virulent gene negative isolates, there was 7 isolates lack of two or more virulence genes. The rate of virulence genes deletion isolates from cooked meat was 31.3% (10/32), the rate of virulence genes deletion isolates from raw meat was 16.1% (5/31), the rate of virulence genes deletion isolates from vegetables was 36.4% (4/11) and rate of virulence genes deletion isolates from seafood was 50% (2/4). No significant difference was found (χ(2) = 3.721, P > 0.05). The virulence gene array-1 strains were dominant among these isolates.</p><p><b>CONCLUSION</b>Among 78 LM isolates, prevalent of virulent genes were different except inlB, virulence genes of LIP-1 were deleted prevalently among isolates, virulence gene deletion patterns were diverse.</p>

Study on the automatic ribotyping for Enterobacter sakazakii / 中华预防医学杂志

<p><b>OBJECTIVE</b>To analyze the ribotyping fingerprint of Enterobacter sakazakii (E. sakazakii) isolated from food and its typing power.</p><p><b>METHODS</b>Two standard strains and twenty-eight isolates of E.sakazakii were analyzed by the DuPont Riboprinter(TM) microbial characterization system. The relevant database was established and the fingerprint patterns were analyzed with BioNumerics software.</p><p><b>RESULTS</b>This system grouped two standard strains and twenty-eight E.sakazakii isolates into 26 ribotypes, and four ribotypes included two strains respectively, the other twenty-two strains showed different ribotypes. The lowest similarity was 31.58%. The number of bands by ribotyping was approximately ten and the molecular weight of these bands ranged from 1 to 50 kb. By the clustering program in BioNumerics, these isolates could be grouped into four clusters.</p><p><b>CONCLUSION</b>The automatic ribotyping method is convenient and fast in E.sakazakii typing.</p>