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

The ban on addition of antibiotics in animal feed in China has made the search for new antibiotics substitutes, e.g. bacteriocin, a hot topic in research. The present study successfully isolated an antibacterial substance producing strain of Bacillus sp. from alpaca feces by agar diffusion method, using Escherichia coli, Salmonella enterica, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus and Listeria monocytogenes as indicator bacteria. The isolated strain was named as B. licheniformis SXAU06 based on colony morphology, Gram staining and 16S rRNA gene sequence. The antibacterial substance was isolated and purified through a series of procedures including (NH4)2SO4 precipitation, chloroform extraction, molecular interception and SDS-PAGE analysis. Bioinformatics analysis of the LC-MS/MS data indicated that the antibacterial substance was a bacteriocin-like substance (BLIS) with an approximate molecular weight of 14 kDa, and it was designated as BLIS_SXAU06. BLIS_SXAU06 exhibited high resistance to treatment of proteinase K, high temperature, high acidity and alkalinity. BLIS_SXAU06 was heterologously expressed in E. coli and the recombinant BLIS_SXAU06 exhibited effective antibacterial activity against S. aureus, S. epidermidis, M. luteus, and L. monocytogenes, showing potential to be investigated further.
Animals ; Anti-Bacterial Agents/pharmacology* ; Bacillus licheniformis ; Bacteriocins/pharmacology* ; China ; Chromatography, Liquid ; Escherichia coli/genetics* ; Listeria monocytogenes ; RNA, Ribosomal, 16S ; Staphylococcus aureus ; Tandem Mass Spectrometry

Strain variability is one of the most important factors to influence the accuracy of foodborne pathogens risk assessment, such as Listeria monocytogenes, Salmonella spp. Strain-to-strain variation is defined as the inherent differences among identically treated strains of the same microbial species. The differences cannot be eliminated by changing test methods or improving test protocols. This review addresses presently related studies of strain variability. Based on the effect of strain variability on the outcome of risk assessment, we summarize sources of variabilities in food chain, strain phenotypic variabilities and the methods to integrate strain variability in growth and inactivation into predictive modelling, and indicate the inadequacies in the study of strain variability. We suggest further study the mechanism of strain variability, expand the comparison of variability among different sources, and integrate the variability of gene expression, protein and cell metabolism into the predictive modelling.
Food Microbiology ; Listeria monocytogenes/genetics* ; Risk Assessment ; Salmonella/genetics*

Listeria monocytogenes is an important zoonotic foodborne pathogen that can tolerate a number of environmental stresses. RsbR, an upstream regulator of the sigma B (SigB) factor, is thought to sense environmental challenges and trigger the SigB pathway. In Bacillus subtilis, two phosphorylation sites in RsbR are involved in activating the SigB pathway and a feedback mechanism, respectively. In this study, the role of RsbR in L. monocytogenes under mild and severe stresses was investigated. Strains with genetic deletion (ΔrsbR), complementation (C-ΔrsbR), and phosphorylation site mutations in the rsbR (RsbR-T175A, RsbR-T209A, and RsbR-T175A-T209A) were constructed to evaluate the roles of these RsbR sequences in listerial growth and survival. SigB was examined at the transcriptional and translational levels. Deletion of rsbR reduced listerial growxth and survival in response to acidic stress. Substitution of the phosphorylation residue RsbR-T175A disabled RsbR complementation, while RsbR-T209A significantly upregulated SigB expression and listerial survival. Our results provide clear evidence that two phosphorylation sites of RsbR are functional in L. monocytogenes under acidic conditions, similar to the situation in B. subtilis.
Alanine/genetics* ; Bacillus subtilis ; Bacterial Proteins/metabolism* ; Binding Sites ; Gene Deletion ; Gene Expression Regulation, Bacterial ; Genetic Complementation Test ; Homeostasis ; Hydrogen-Ion Concentration ; Listeria monocytogenes/metabolism* ; Listeriosis/microbiology* ; Mutation ; Phenotype ; Phosphoproteins/metabolism* ; Phosphorylation ; Sigma Factor/metabolism* ; Stress, Physiological

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

Bacterial Proteins ; chemistry ; genetics ; metabolism ; DNA, Bacterial ; chemistry ; genetics ; metabolism ; Gene Expression Regulation, Bacterial ; physiology ; Glutathione ; metabolism ; Listeria monocytogenes ; chemistry ; genetics ; metabolism ; Peptide Termination Factors ; chemistry ; genetics ; metabolism

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

OBJECTIVEThe loop-mediated isothermal amplification (LAMP) detection method was applied to detect Listeria monocytogenes in food. The specificity and sensitivity of this method were evaluated through comparing it with Real-time PCR and conventional detection method.

METHODSThe LAMP primers were designed based on hly gene of Listeria monocytogenes. The LAMP method was applied to detect 88 Listeria monocytogenes, 1 reference strain ATCC 15313 of Listeria monocytogenes and 33 non-targets bacteria strains; base-material addition test and practical food samples detection were also conducted. Both of Real-time PCR and ISO 11290-1 methods were used as parallel detection method in addition to LAMP. The three kinds of methods were compared by specificity, sensitivity, detection limit and the detection result of practical food samples.

RESULTSBoth detection results of LAMP and Real-time PCR for 89 Listeria monocytogenes were positive (100%, 89/89), 33 non-targets bacteria strains were negative (100%, 33/33). The sensitivity of LAMP was 2 × 10² CFU/ml, which was consistent with Real-time PCR method (2 × 10² CFU/ml) and better than ISO 11290-1 method (2 × 10² CFU/ml). Base-material addition test result showed that the detection limit of the three kinds of methods were 3 CFU/25 g samples. And the result of practical food samples displayed the same detection rate of 4% in the three methods (2/45).

CONCLUSIONThe LAMP method of Listeria monocytogenes established in this study has good specificity and sensitivity, which can be applied to the rapid detection of Listeria monocytogenes.

Food Contamination ; analysis ; Food Inspection ; methods ; Food Microbiology ; Listeria monocytogenes ; genetics ; isolation & purification ; Nucleic Acid Amplification Techniques ; methods

The incidence of diabetes mellitus is increasing among companion animals. This disease has similar characteristics in both humans and animals. Diabetes is frequently identified as an independent risk factor for infections associated with increased mortality. In the present study, homozygous diabetic (db/db) mice were infected with Listeria (L.) monocytogenes and then treated with the anti-diabetic drug exendin-4, a glucagon-like peptide 1 analogue. In aged db/db mice, decreased CD11b+ macrophage populations with higher lipid content and lower phagocytic activity were observed. Exendin-4 lowered high lipid levels and enhanced phagocytosis in macrophages from db/db mice infected with L. monocytogenes. Exendin-4 also ameliorated obesity and hyperglycemia, and improved ex vivo bacteria clearance by macrophages in the animals. Liver histology examined during L. monocytogenes infection indicated that abscess formation was much milder in exendin-4-treated db/db mice than in the control animals. Moreover, mechanistic studies demonstrated that expression of ATP binding cassette transporter 1, a sterol transporter, was higher in macrophages isolated from the exendin-4-treated db/db mice. Overall, our results suggest that exendin-4 decreases the risk of infection in diabetic animals by modifying the interaction between intracellular lipids and phagocytic macrophages.
ATP-Binding Cassette Transporters/metabolism ; Age Factors ; Animals ; Blood Chemical Analysis ; Cholesterol/metabolism ; Diabetes Mellitus, Type 2/*drug therapy/genetics ; Dyslipidemias/drug therapy/genetics ; Female ; Hyperglycemia/drug therapy/genetics ; Hypoglycemic Agents/*therapeutic use ; Injections, Intraperitoneal ; *Lipid Metabolism/drug effects ; Listeria monocytogenes/*drug effects/immunology ; Listeriosis/*drug therapy/immunology/microbiology ; Macrophages/drug effects/*metabolism ; Mice ; Obesity/drug therapy/genetics ; Peptides/*therapeutic use ; Phagocytosis/drug effects ; Venoms/*therapeutic use

Listeria monocytogenes (LM), a Gram-positive facultative intracellular bacterium, can be used as an effective exogenous antigen expression vector in tumor-target therapy. But for successful clinical application, it is necessary to construct attenuated LM stain that is safe yet retains the potency of LM based on the full virulent pathogen. In this study, attenuated LM and recombinants of LM expressing melanoma inhibitory activity (MIA) were constructed successfully. The median lethal dose (LD(50)) and invasion efficiency of attenuated LM strains were detected. The recombinants were utilized for immunotherapy of animal model of B16F10 melanoma. The level of MIA mRNA expression in tumor tissue was detected by using real-time polymerase chain reaction (PCR) with specific sequence, meanwhile the anti-tumor immune response was assayed by flow cytometric analysis and enzyme-linked immunosorbent spot (ELISPOT) assay. The results showed the toxicity and invasiveness of attenuated LM were decreased as compared with LM, and attenuated LM expressing MIA, especially the double-genes attenuated LM recombinant, could significantly induce anti-tumor immune response and inhibit tumor growth. This study implicates attenuated LM may be a safer and more effective vector for immunotherapy of melanoma.
Animals ; Cancer Vaccines ; genetics ; immunology ; Extracellular Matrix Proteins ; genetics ; immunology ; Listeria monocytogenes ; immunology ; Male ; Melanoma ; genetics ; immunology ; Mice ; Mice, Inbred C57BL ; Vaccines, Attenuated ; genetics ; immunology