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Background and Objective: Listeria monocytogenes is a gram-positive facultative intracellular non spore forming bacillus. The epidemiologic studies have shown that Listeria monocytogenes is the cause of abortion and abnormalities in human embryo. This study was done to determine the effect of listeria monocytogenes colonization on maternal and fetal liver and spleen in mice. Methods: In this experimental study, Inbred BALB/c dams allocated into case and control groups. Dams in interventional and control groups were received 200µL of 1.2 LogFCU/ml, Listeria monocytogenes and normal salin intraperitoneally, respectively. Few mice from each group were randomally selected and 5ml of blood collected, placenta, uterus liver and spleen were removed subsequently in 13 and 24 day of gestation and listeria monocytogenes colonization were determined. Liver and spleen of full term offsprings were stained for the histological studies. Results: L.monocytogenes strains were detected in different organs of mice damsup for 30 day of gestation. The higest and lowest of organ contamination were seen in liver and blood samples, respectively. The ratio of weight/volume of organ was higher in case than control groups. Hepatocytes degenration, hepatocyte size alteration, cell cord atrophy and sinusoid dilatation were seen in the liver. Disruption of red pulp, disorganization of lymphoid nodules and necrosis were noticed in the spleen. Conclusion: Contamination of BALB/c dams causes the histological alterations in the liver and spleen of offesprings.

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Background and Objective: Probiotc bacteria have benefical effect on consumer health. This study was done to investigate the antimicrobial effect of several probiotic in combinations with different prebiotics against food patoghenic bacteria including Staphylococcus aureus and Listeria monocytogenes.

Methods: In this descriptive - analytical study, probiotics including Lactobacillus plantarum, L. acidophilus, L. fermntum, L. casei and L. rhamnosus with prebiotics (1%) including raffinose, lactulose, inulin and trehalose were cultured in MRS broth for 24 hours at 30ºC in anaerobic conditions. Antimicrobial property of them was determined with well diffusion plate's method.

Results: Probiotics in the presence of prebiotics indicated the higher antimicrobial effect compared to probiotics alone (P<0.05). The application of prebiotics such as L. casei with raffinose showed higher antimicrobial property against Listeria monocytogenes than the free prebiotics consumption. The diameter of inhibitory growth zone in the presence of raffinose as a prebiotics was 14.66 mm and its absence reduced to 11.75 mm.

Conclusion: Antimicrobial effect of probiotics in combination with prebiotics against Staphylococcus aureus and Listeria monocytogenes was higher than probiotics consumption alone.

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Background and Objective: Listeria monocytogenes is an important food-borne intracellular pathogen which can transmit to human through contaminated foods and causing meningitis, meningoencephalitis and abortion. This study was done to determine the frequency, antimicrobial susceptibility and serotyping of Listeria monocytogenes isolated from food samples in Tehran, Iran.
Methods: This descriptive was carried on 150 food samples including vegetables, cheese and meat were collected from supermarkets, open-air markets, and delicatessens in different regions of Tehran, Iran since April to September 2018. The presumptive isolates were characterized biochemically. All L. monocytogenes isolates were further analyzed by serotyping and antimicrobial susceptibility tests.
Results: Out of 150 samples, Listeria spp. was detected in 30 (20%) samples in which 9 (6%) were positive for L. monocytogenes [vegetables (n=4, 44.44%), cheese (n=2, 22.22%) and meat (n=3, 33.33%)]. of the 9 L. monocytogenes isolates, 5 (55.55 %), 3 (33.33 %), and 1 (11.11%) belonged to serotypes 4b, 1/2b, and 1/2a, respectively. The most L. monocytogenes isolates were resistant to Trimetoprime, Sulfamethoxazole, Tetracycline, Streptomycin, Chloramphenicol, and Ciprofloxacin while were sensitive to Penicillin G, Gentamicin, Streptomycin, and Ampicillin, and were intermediately resistant to Ciprofloxacin.
Conclusion: The rate of Contamination of vegetable, cheese and meat samples with L. monocytogenes is important in Tehran, Iran. Due to the potential contamination samples to Listeria, there is necessity need for continuous monitoring and the development of a precise program for identifying this bacterium in Tehran and the whole country.

 

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Background and Objective: Listeria monocytogenes is a gram-positive and foodborne pathogen that is psychrophilic and has the ability to tolerate a high percentage of salt by more than 10%. This bacterium grows in many food products that have a long shelf life. This study was performed to evaluate the expression of genes hly and inlA of Listeria monocytogenes bacteria in the viable but non-culturable (VBNC) condition in temperatures of 4 degrees Celsius.
Methods: In this descriptive laboratory study, bacteria in 10⁶ counts in mid log phase were inoculated into BHI Agar rich medium and It was investigated and stored at refrigerated temperature (4 degrees Celsius) until the cultivate was lost. At the end of the 16S rRNA gene, the hly and inlA genes were studied as pathogenic genes of this bacterium. The expression of these genes before and after entering to VBNC state was performed to compare their expression.
Results: Listeria bacteria lost its cultivation ability after 5 months of storage at a refrigerated temperature. The results of the gene expression analysis showed that at the end of the period, the bacterium entered "Viable But non-Culturable" form; also the hly and inlA pathogenic genes were not expressed in riched medium. By adding blood to the rich culture medium of this bacterium, the hemolysin O pathogen gene was re-illuminated.
Conclusion: The results of this study show that the possibility of bacterial entry into VBNC mode occurs at the refrigerator condition, and the expression of its pathogenic genes is affected. Blood and its agents can act as an agent for the induction and clarification of the hly gene. Therefore, it is necessary to review the microbial quality control of fishery products.