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ObjectiveIn order to find out the contamination situation and potential risk of Listeria monocytogenes in refrigerated ready-to-eat prepackaged foods. This study carried out a quantitative contamination risk survey of L. monocytogenes for ready-to-eat cooked meat products with short shelf life.MethodsWe collected 64 samples of ready-to-eat cooked meat from Chengdu， and carried out qualitative and quantitative detection of L. monocytogenes according to traditional culture method and RT-PCR molecular detection method. Additionally， the second generation of the whole genome sequencing was performed after DNA extraction of the isolated strains， and relevant epidemiological characteristics were analyzed.ResultsThe results showed that L. monocytogenes were isolated from 6 samples of cooked meat （6/64）. All 6 L. monocytogenes positive samples were produced by the same manufactory， of which 5 were three platters of marinated meat. The results of quantitative detection showed that the contamination level of L. monocytogenes in three platters of marinated meat was 30-200 CFU/g， and the contamination level of cooked pork samples with positive L. monocytogenes was lower as

The problem of food-borne illnesses due to microbial contamination of infant and young children foods is usually of international concern， and the unique character of the infant and young child population requires special and strict food safety requirements for their own foods. This article reviews the progress of contamination with Salmonella and Cronobacter （Enterobacter sakazakii） of Enterobacteriaceae family in foods for infants and young children and its diseases risk at home and abroad in recent years， and also provides technical support for the revision of national standards for infant and young children foods and its manufacturing processes in China through the comparative analysis of domestic and international microbiological limits for infant and young children foods.

ObjectiveTo determine the antimicrobial susceptibilities of 33 Listeria monocytogenes cultured from ready-to-eat (RTE) meats in China and to use whole genome sequencing (WGS) to characterize the antimicrobial resistance and virulence genotypes of these isolates.MethodsThe susceptibilities of 33 Listeria monocytogenes were determined by broth microdilution. These isolates were then sequenced using short-read high accuracy protocols. The corresponding genomes were assembled and further analysis was carried out using appropriate bioinformatics pipelines.ResultsAll isolates were found to be susceptible to ampicillin, trimethoprim-sulfamethoxazole, gentamicin, meropenem and vancomycin. One isolate was resistant to tetracycline and erythromycin at the same time. All 33 L. monocytogenes were classified into 13 STs, among them ST9, ST87, ST122 were the dominant, from which resistant isolate belonged to ST87. The genotypes of the resistant isolate correlated well with its resistant phenotype. Up and down stream analysis of the genetic context, in which these resistant genes were found, suggested that they may have been acquired from Erysipelothrix rhusiopathiae and Blautia product. All isolates harboured LIPI-1 and LIPI-2, 7 of them harbored LIPI-3, and 8 harboured LIPI-4(1 ST121 and 7 ST87).ConclusionThese data showed that acquired resistance existed in this bacterium from RTE meats origins, and can be a potential public health risk due to its high harboring rate of LIPI-3 and LIPI-4. It was suggested that the monitoring of L. monocytogenes in RTE meats should be strengthened in the future, specifically for ST87.

ObjectiveIn order to explore the contamination and drug resistance of foodborne pathogens in fresh cut fruits and vegetables, samples were collected from retail markets in five district in Beijing.MethodsThe national standard method of food microbiological examination was used to detect Staphylococcus aureus, Salmonella, Listeria monocytogenes and Escherichia coli respectively. The drug resistance of the isolates was determined, and the Diarrheagenic Escherichia coli was screened by fluorescent PCR.ResultsAmong 326 fresh cut fruits and vegetables sold in Beijing, the contamination rates of Staphylococcus aureus, Listeria monocytogenes, Salmonella, Escherichia coli and Enteroaggregative Escherichia coli were 15.34%, 1.84%, 0%, 9.51% and 1.23% respectively. 50 strains of Staphylococcus aureus isolated in this study were mainly resistant to penicillin (90.00%) and oxacillin (48.00%), 31 strains of Escherichia coli were mainly resistant to compound sulfamethoxazole (67.74%) and ampicillin (64.50%), and 4 strains of Enteroaggregative Escherichia coli showed multiple drug resistance. All 6 strains of Listeria monocytogenes were sensitive to 10 kinds of antibiotics.ConclusionThis research provided a scientific experimental basis for formulating the prevention and control strategy of foodborne diseases.

ObjectiveTo understand the contamination of pathogens and the antibiotics resistance characterization in raw milk in China.MethodsA total of 53 raw milk samples collected from 43 pastures in different regions in China from September to November in 2019 were detected the contamination of six pathogens, and isolates were tested for the antibiotic resistant ability.ResultsThe contamination rates of Escherichia coli, Staphylococcus aureus, Bacillus cereus and Listeria monocytogenes were 62.26%(33/53), 20.75%(11/53), 5.66%(3/53)and 3.77%(2/53), respectively. The detection of Cronobacter and Salmonella were negative. A total of 117 isolates were selected for antibiotics resistance test and 58 strains were resistant to antibiotics, accounted for 49.57%(58/117). 33 of 90 gram-negative strains were resistant strains, accounted for 36.67%(33/90). 25 of 27 gram-positive bacteria were resistant strains, accounted for 92.59%(25/17).ConclusionThe bacterial contamination in raw milk collected from pastures in different regions was quite different, and showed a downward trend with the decrease of temperature. Isolates from raw milk showed a high multiple antibiotics resistance rate, suggesting a cautious control of veterinary antibiotics should be adopted.

Objective Campylobacter species are the main causes of foodborne illness worldwide, posing significant threats to public health. This study aimed to investigate the antibiotic resistance and genomic characterization of C. jejuni/C.coli from retail chickens in Beijing. Methods Antimicrobial susceptibility testing was conducted on 126 C. jejuni/C. coli isolated from retail chickens in Beijing, following CLSI protocols. Whole genomes of all isolates were sequenced using the Illumina platform. Results More C. coli (83.82%) showed multi-drug resistance than C. jejuni (8.62%). Genomic analysis demonstrated 42 sequence types (STs) and 12 clonal complexes (CCs), from which CC828 and CC52 were dominant. cdtA, cdtB and cdtC encoding cytotoxic protein were present spontaneously in most C. jejuni but not found in any C. coli isolates. The abundances of antibiotic resistance genes (ARGs) and virulence genes (VGs) in C. jejuni and C. coli were significantly different, with ARGs numbered in C. coli and VGs in C. jejuni. Conclusions High prevalence of multi-drug resistance C. coli and C. jejuni isolated from Beijing chickens were challenging clinical antibiotic usages in the treatment of Campylobacter infection. The surveillance of particular C. jejuni and C. coli STs correlated with higher resistance and virulence needs to be strengthened in the future. [ABSTRACT FROM AUTHOR]

Objectives: Our aim was to determine the antimicrobial susceptibilities of 2862 Listeria monocytogenes cultured from various foods in China and to use WGS to characterize the antimicrobial resistance and virulence genotypes of those expressing a resistance phenotype.Methods: The susceptibilities of 2862 L. monocytogenes were determined by broth microdilution. Twenty-eight L. monocytogenes were found to be resistant to one to four antibiotics. All 28 resistant isolates were subsequently sequenced using short-read high accuracy protocols. The corresponding genomes were assembled and further analysis was carried out using appropriate bioinformatics pipelines.Results: All 28 resistant L. monocytogenes were classified into five STs (ST3, ST8, ST9, ST155 and ST515). Both ST9 and ST155 were dominant and their genotypes correlated with their resistance phenotypes. All ST9 isolates were MDR and could be phylogenetically classified into two clusters. One was relatively close to clinical origins and one to food. Downstream analysis of the genetic contexts in which these resistance genotypes were found suggested that these may have been acquired from other bacteria by horizontal transfer or insertion into the chromosome. All isolates harboured Listeria pathogenicity island (LIPI)-1 and LIPI-2, and only two harboured LIPI-3.Conclusions: This study reported on the antimicrobial susceptibilities of 2862 foodborne L. monocytogenes along with the genomic characterization of 28 resistant isolates, 11 of which expressed an MDR phenotype. These data showed that this bacterium can acquire resistance by horizontal gene transfer in and between species. This study may necessitate a re-evaluation of risk to public health, associated with this bacterial species. [ABSTRACT FROM AUTHOR]

Introduction: This study characterized Vibrio alginolyticus isolated from seafood and freshwater products in China (2020)., Methods and Results: In total, 122 (95.31%) V. alginolyticus isolates were resistant to at least 1 antibiotic category, and 2 (1.56%) isolates were resistant to at least 3 antibiotic categories and belong to multi-drug resistance (MDR) isolates. A high prevalence rate was observed to be blaCARB (98.04%) encoding beta-lactam resistance, followed by tet (97.06%) encoding tetracycline resistance and fos (4.90%) encoding resistance to fosfomycin. Among the 57 V. alginolyticus isolates, the commonest virulence genes were type III secretion system translocated gene vopD , vopB , and vcrH (54.4%, 31/57), type III secretion system regulated gene tyeA (54.39%), followed by vscI and vscF (50.88%) encoded type III secretion system inner rod protein and needle protein, respectively. Multilocus sequence typing (MLST) showed considerable genetic diversity, with 34 distinct sequence types (STs) identified among 55 isolates. ST421 ( n  = 5), ST166 ( n  = 4), ST523 ( n  = 3), ST516 ( n  = 3), and ST507 ( n  = 3) were dominant STs among 55 V. alginolyticus isolates., Discussion: These findings highlight the widespread occurrence of V. alginolyticus in both freshwater and seafood products, underscoring the critical need for vigilant monitoring of these bacteria. Such measures are essential for ensuring effective food safety management and safeguarding public health., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Sun, Yan, Yan, Li, Li, Yan, Yang, Peng, Yang, Sun, Xu, Dong and Bai.)

Chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) has been recognized as a major driver of amphibian declines worldwide. Central and northern Asia remain as the greatest gap in the knowledge of the global distribution of Bd. In China, Bd has recently been recorded from south and central regions, but areas in the north remain poorly surveyed. In addition, a recent increase in amphibian farming and trade has put this region at high risk for Bd introduction. To investigate this, we collected a total of 1284 non-invasive skin swabs from wild and captive anurans and caudates, including free-ranging, farmed, ornamental, and museum-preserved amphibians. Bd was detected at low prevalence (1.1%, 12 of 1073) in live wild amphibians, representing the first report of Bd infecting anurans from remote areas of northwestern China. We were unable to obtain evidence of the historical presence of Bd from museum amphibians (n = 72). Alarmingly, Bd was not detected in wild amphibians from the provinces of northeastern China (>700 individuals tested), but was widely present (15.1%, 21 of 139) in amphibians traded in this region. We suggest that urgent implementation of measures is required to reduce the possibility of further spread or inadvertent introduction of Bd to China. It is unknown whether Bd in northern China belongs to endemic and/or exotic genotypes, and this should be the focus of future research.

Objective: To survey the contamination of L. monocytogenes isolated from retail ready-to-eat meats in Beijing., Methods: Ready-to-eat meats were quantitatively detected for L. monocytogenes using MPN method. L. monocytogenes isolates were analyzed by PFGE., Results: Fourteen out of 197 ready-to-eat meat samples were positive for L. monocytogenes with the contamination rate of 7.11% and the geometry mean contamination level of 14.31 MPN/g. The contamination of L. monocytogenes isolated from free trade market (13.89%) was more severe than those from specificity store (8.57%), supermarket (5.75%) and restaurant (2.56%), while supermarket had the highest mean contamination level of 22.78 MPN/g. A total of 13 PFGE types were characterized using DICE-UPGMA analysis through BioNumerics 7.1 software. There were two isolates from the same free trade market share the same PFGE type, which suggested the same contamination source of both samples., Conclusion: Contamination of L. monocytogenes exist in retail ready-to-eat meats. The contamination level of L. monocytogenes isolated from free trade market is more severe than those from specificity store, supermarket and restaurant.

Objective: To acquire accurate and successful DNA sequencing in a cost-effective way by ABI3500xl automatic genetic analyzer., Methods: BigDye was diluted to 8, 16 and 32 times in PCR product sequencing. Three different methods including CENTRI-SEP kit, BigDye cleaning beads and ethanol-NaAc-EDTA were used to purify the sequencing PCR products., Results: The results of DNA sequencing were correct when BigDye was diluted up to 16 times. The misreading of nucleic acid bases was found as BigDye was diluted to 32 times. All three purification methods provided acceptable DNA sequencing results. In terms of method for purification of PCR products, the CENTRI-SEP Kit was the most expensive but time-saving (0.5 h), while ethanol-NaAc-EDTA method was the most economical but time-consuming (2 h). The BigDye cleaning beads method was of a suitable purification time (1 h) but not fit for high-throughput DNA sequencing., Conclusion: BigDye should be diluted up to 16 times in DNA sequencing by ABI3500xl DNA analyzer. Although all three purification methods may promise DNA sequencing results with good quality, it is necessary to choose an appropriate one to keep the balance between time and cost on the basis of the lab condition.

Objective: To evaluate the antimicrobial resistance of Vibrio parahaemolyticus isolated from shellfish and its habitat in Sichuan, Fujian and Guangxi., Methods: The susceptibility of 186 isolates of Vibrio parahaemolyticus to 8 antibiotics were determined by broth microdilution susceptibility test. The antibiotics of ampicillin, cefotaxime, ceftazidime, gentamicin, tetracycline, chloramphenicol, ciprofloxacin and trimethoprim/sulfamethoxazole were used., Results: The antibiotic resistance rate were 69.35% in which ampicillin resistance was the most prevalent. The geometric mean of ampicillin MIC value of all isolates was greater than the interpretation value of resistance. Among the 186 tested isolates, the multiple antibiotic resistance and/or intermediate resistance was 4. All strains were 100% sensitive to cefotaxime, ceftazidime, chloramphenicol and ciprofloxacin. The ampicillin susceptibility spectrum of aquaculture farm was the highest among the three sectors as 73.68% and Sichuan was the highest among the three provinces as 70.94% although there were no significant differences. There were 44 samples out of which 2 and above strains were isolated, and the susceptibility spectrum polymorphism rate of strains isolated from the same sample was 77.27% (34/44)., Conclusion: The ampicillin resistance rate is relatively high, and shellfish habitat may be the main source of antimicrobial resistance of Vibrio parahaemolyticus. There is an urgent need to strengthen the surveillance and management of Vibrio parahaemolyticus in the shellfish breeding process.