OBJECTIVETo study the virulent gene prevalence of foodborne Listeria monocytogenes (LM) isolated from China.

METHODS78 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.

RESULTS87.2% (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.

CONCLUSIONAmong 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.

China ; epidemiology ; Food Contamination ; analysis ; Food Microbiology ; Foodborne Diseases ; epidemiology ; microbiology ; Listeria monocytogenes ; genetics ; isolation & purification ; pathogenicity ; Listeriosis ; epidemiology ; microbiology ; Virulence Factors ; genetics

We aimed to investigate the potential pathogenic profile and antibiotic resistance of Listeria monocytogenes isolated from ready-to-eat food in China. Antimicrobial resistance was determined by broth microdilution following the Clinical and Laboratory Standards Institute protocol. Molecular serotyping, virulence, and resistance genes were identified using PCR. Multi-locus sequence typing was performed on resistant strains. A total of 11.53% (113/980) isolates were resistant, from which 82.3% (93/113) harbored all the virulence genes tested. The resistant strains were subtyped into 18 sequence types (STs), from which ST2, ST5, ST8, and ST9 were involved in listeriosis. This study indicated that several L. monocytogenes isolates from ready-to-eat foods in China have pathogenic potential and are resistant to antibiotics, including antibiotics used as medicines by humans for listeriosis treatment.
Anti-Bacterial Agents ; pharmacology ; China ; epidemiology ; Drug Resistance, Multiple, Bacterial ; Fast Foods ; microbiology ; Food Microbiology ; Listeria monocytogenes ; genetics ; isolation & purification ; pathogenicity ; Listeriosis ; epidemiology ; microbiology ; Multilocus Sequence Typing ; Virulence

This study aimed to investigate the prevalence and molecular characteristics of Listeria monocytogenes in cooked products in Zigong City, China. The overall occurrence of the L. monocytogenes in the ready-to-eat (RTE) shops and mutton restaurants surveyed was 16.2% (141/873). An occurrence of 13.5% was observed in RTE pork, 6.5% in RTE vegetables, and more than 24.0% in either cooked mutton or cooked haggis. Serotype 1/2b (45.4%), 1/2a (33.3%), and 1/2c (14.2%) were the predominant types. By comparing the clonal complexes (CCs) based on multilocus sequence typing (MLST) of the L. monocytogenes from cooked foods in Zigong City and 33 listeriosis cases from different districts of China, CC87, CC9, CC8, and CC3 were showed to be prevalent in cooked products and CC87 and CC3 were the first two frequent types in the 33 clinic-source strains. All CC87 stains harbored the newly reported Listeria pathogenicity island 4 (LIPI-4) gene fragment ptsA, and all CC3 strains possessed the Listeria pathogenicity island 3 (LIPI-3) gene fragment llsX. These may increase the occurrence of the strains belonging to CC87 and CC3 in listeriosis cases in China and also underline the risk of infection owing to the consumption of the cooked products from Zigong. ST619 (serotype 1/2b) harbored both llsX and ptsA, indicating a potential hypervirulent sequence type in Zigong.
China ; epidemiology ; Cooking ; Fast Foods ; microbiology ; Food Contamination ; Food Microbiology ; Humans ; Listeria monocytogenes ; genetics ; pathogenicity ; Listeriosis ; epidemiology ; microbiology ; Meat ; microbiology ; Multilocus Sequence Typing ; Prevalence ; Seasons

Objective To investigate the effect of long intergenic non-coding RNA COX2 (lincRNA-COX2) on apoptosis and polarization of Listeria monocytogenes (Lm)-infected RAW264.7 cells. Methods RAW264.7 cells were cultured and divided into control group (uninfected cells), Lm infection group, negative control of small interfering RNA (si-NC) group, si-NC and Lm infection group, small interfering RNA of lincRNA-COX2 (si-lincRNA-COX2) group, si-lincRNA-COX2 and Lm infection group. RAW264.7 cells were infected with MOI=10 Lm for 6 hours, and then the inhibition efficiency of siRNA transfection was detected by fluorescence microscope and quantitative real-time PCR (qRT-PCR). The expression levels of cleaved-caspase-3(c-caspase-3), caspase-3, B-cell lymphoma-2 (Bcl2), Bcl2 associated X protein (BAX), arginase 1 (Arg1), inducible nitric oxide synthase (iNOS) were detected by Western blot analysis. Results c-caspase-3/caspase-3, BAX/Bcl2 and iNOS were significantly up-regulated, while the level of Arg1 was down-regulated in Lm-infected RAW264.7 cells compared with control group. LincRNA-COX2 knockdown inhibited the increase of protein levels for BAX/Bcl2, c-caspase-3/caspase-3 and iNOS in Lm-infected RAW264.7 cells, while the level of Arg1 in Lm-infected RAW264.7 cells was up-regulated. Conclusion Knockdown of lincRNA-COX2 can inhibit cell apoptosis and suppress the macrophage polarization into M1 type in Lm-infected RAW264.7 cells.
Apoptosis/genetics* ; bcl-2-Associated X Protein/metabolism* ; Caspase 3/metabolism* ; Cyclooxygenase 2/metabolism* ; Listeria monocytogenes/pathogenicity* ; Macrophages/microbiology* ; RNA, Long Noncoding/metabolism* ; RNA, Small Interfering/genetics* ; Animals ; Mice

In order to study the pathogenesis of Listeria monocytogenes (LM), we cloned listeriolysin gene into prokaryotic expression vector PET21a. The expression vector was transformed into Escherichia coli BL21 for expression of listeriolysin O (LLO). LLO-His tag fusion protein was purified with a Ni-NTA affinity column and was used as an immunogen to vaccinate BALB/C mice. Hybridomas were developed by fusing mouse myeloma cells Sp2/0 and splenocytes from the immunized mice and screened with purified LLO. Three hybridomas secreting antibodies against listeriolysin O were obtained and named anti-LLO1, anti-LLO2 and anti-LLO3, respectively. Western blotting analysis showed that all of them could specifically bind to the LLO secreted by the LM. The titers of anti-LLO monoclonal antibodies in the supernatants of three hybridomas cultures were 1:3.6 x 10(4), 1:6.4 x 10(4) and 1:1.6 x 10(4), respectively, and the titers of ascites from the hybridoma-injected mice were 1:2 x 10(7), 1:2 x 10(7) and 1:1 x 10(7), respectively, based on ELISA test. The isotypes of the monoclonal antibodies were determined to be IgG1. The dissociation constants (Kd) of these three monoclonal antibodies were determined to be 6.18 x 10(-11), 7.50 x 10(-11) and 6.27 x 10(-11) respectively. These data and reagents will be of great assistance to elucidate the pathogenesis of Listeriosis.
Animals ; Antibodies, Monoclonal ; biosynthesis ; immunology ; Bacterial Toxins ; biosynthesis ; genetics ; immunology ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Heat-Shock Proteins ; biosynthesis ; genetics ; immunology ; Hemolysin Proteins ; biosynthesis ; genetics ; immunology ; Listeria monocytogenes ; genetics ; pathogenicity ; Mice ; Mice, Inbred BALB C ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; immunology