listeria monocytogenes

Listeriosis, an important illness with a high mortality rate (up to 30%), is caused by Listeria monocytogenes. Nowadays, there are several reports that display the prevalence of L. monocytogenes in fisheries products. Therefore, it is important to investigate and control the expression of virulence genes and adhesion-related genes in different strains of this bacterium in foodstuffs. In this study, the expression levels of inlA, hly, lmo1634, lmo1847, sigB, and prfA genes in two isolates (food and clinical) were investigated under the influence of NaCl and lime juice in the shrimp broth. The results of the independent t-test for the prfA gene demonstrated that the expression level in the treatments of clinical strain was significantly higher than the food strain (p<0.05). Similarly, the average expression of both adhesion genes (lmo1847 and lmo1634) and stress gene (sigB) in the studied treatments for the clinical strain was significantly higher than the food strain. In both strains, the role of lime juice in increasing the expression of virulence and adhesion genes was significantly higher than in NaCl treatments (p<0.05). Overall, it can be stated that the transcription level of virulence- and adhesion-related genes upon exposure to preservatives may be different in the various L. monocytogenes isolates.

Microbiological control of food is important to prevent food poisoning in humans. Pathogenic microorganisms are gram-positive or gram-negative pathogens found in food that cause gastroenteritis. The purpose of this study is to investigate the amount of Listeria monocytogenes and Salmonella in fish, shrimp and eggs presented in Shahrekord city. In this study, 300 samples, including 100 fish samples, 100 shrimp samples, and 100 egg samples, were randomly collected from retail stores in Shahrekord city and transferred to the specialized food hygiene laboratory of Shahrekord Islamic Azad University. The samples were enriched in Listeria enrichment culture medium for 48 hours and then on the selected culture medium and the suspected Listeria isolates from Palcam agar culture medium were counted after biochemical confirmation tests and for confirmation Salmonella was used from SS agar, BS agar and then TSI and LIA culture media. Research The results showed that 2 out of 100 fish samples (2 percent), 4 out of 100 shrimp samples (4 percent), and 5 out of 100 egg samples (5 percent) were contaminated. It was Listeria monocytogenes. The amount of Salmonella contamination for fish, shrimp and eggs was 9, 11 and 18 respectively. Due to the prevalence of Listeria, it is recommended to avoid consumption of undercooked seafood by at-risk populations. Strict implementation of sanitary conditions of food contact surfaces and handling areas, and good personal hygiene practices should reduce possible contamination of seafood products by L. monocytogenes.

Anzali wetland is the most important intermediate ecosystem in the Caspian sea catchment area and plays an important role in refining the inputs of rivers in this area and acts as a natural filter. In this study, the overall microbial load and bacteria of Yersinia enterocolitica and Listeria monocytogenes and its relationship with pH and EC of water were investigated. Surface layer sampling was performed from autumn 2018 to summer 2019 using standard water sampling methods. The highest logarithmic mean of the total bacterial count was 5.513/ ml at Ali Abad station in summer and the lowest logarithmic mean of the total bacterial count was 3.914/ ml at Abknar station in autumn and above standard. The rate of contamination of different wetlands to Yersinia enterocolitica and Listeria monocytogenes using specific media was 41% and 50% respectively and in the PCR method with specific primer pairs, were 35.7% and 42.8% respectively. The highest pH in Sangachin station was 8.86 and the highest EC was 1050μs / cm in Talebabad station. Duncan test showed a significant difference at most stations with the percentage of specific cultures, pH and EC factors and the logarithmic mean of total bacterial count (p<0.05). Also, using Duncanchr('39')s test in the PCR method, Listeria monocytogenes in autumn were statistically significantly different from other seasons (p<0.05) and Yersinia enterocolitica was statistically significant in autumn and summer (p<0.05). Elevated water temperatures, urban population growth around wetlands, and sewage entry are major causes of increased the level of pollution in Anzali wetland and its transmission through the food cycle and indicates the risk of pathogenicity.

The aim of this study was to investigate the effects of temperature, pH and orange essential oil on reducing the growth rate of L. monocytogenes. The variables included 45 ° C (for 144 hours), 50 ° C (for 72 hours), 55 ° C (for 6 hours), 4 pH levels (4, 5, 6) and essential oil citrus (Citrus aurantium L.) in 0.2, 0.4 and 0.6% levels on the growth rate of L. monocytogenes in cold smoked silver carp fillet. The results showed that the number of bacteria increased with increasing pH at the studied temperatures (P<0.05), But correlation analysis showed no correlation between L. monocytogenes and pH. The increase in temperature significantly reduced the number of bacteria in cold and hot smoked silver carp fillets, so that the lowest bacterial count in both cold and hot smoked fillets was counted in a temperature of 55 ° C. The correlation between number of bacteria and temperature also confirmed this. Regarding the effect of citrus essential oil on the number of bacteria, the results showed that in the conditions of pH and constant temperature, increasing the percentage of essential oil, the number of L. monocytogenes decreased and this decrease, especially in the treatment of 0.6% of orange essential oil. Also, at the same temperature and pH, hot smoking compared to cold smoking was more effective in reducing the number of L. monocytogenes. Given that the number of bacteria counted in both methods of smoke at different temperatures and pH was not higher than the107 Log cfu/ g standard, it could be argued that smoke is a reliable way to increase the shelf-life of silver carp fillet and the best temperature and time to smoke was 55 ° C for 6 hours, at pH = 4, and essential oil level was 0.6%.

This study aimed to evaluate the antioxidative and antimicrobial effects of chitosan nanocompsites and rosemary extract coating in the inoculated fillet of Huso huso with Listeria monocytogenes during refrigerated storage (4±1ºC). Fish were filleted and divided into four groups as control (without coating), 0.5% rosemary extract treatment (RET), 1% chitosan treatment (CT) and combination of 1% chitosan and 0.5% rosemary extract as chitosan nanocomposites treatment (CS/RE). Then all samples inoculated with L. monocytogenes. Subsequently, the chemical parameters (TVB-N, PV, pH and TBA) and antilisterial properties of coatings were monitored during 16-days of refrigerating storage at 4±1ºC. According to the results, CS/RE demonstrated a significant (P0.05) compared to the other treatments. On the other hand, CS/RE coating retarded lipid oxidation by decreasing PV and TBA production in the samples compared to the control up to the end of refrigerated storage (P

Listeria monocytogenes is a foodborne pathogen which has high resistance for unfavorable conditions. This pathogen is able to entering Viable but non culturable (VBNC) state in harsh conditions. The present study was aimed to consider the possibility of entering this pathogen in to VBNC state in heavy brine which used for produce brined fish. For this purpose L. monocytogenesat 1.12×107 initial concentration as monitored in three treatments during 8 days: brine containing 30% salt (ES30), brine containing 10% salt (ES10) and starvation condition (DE). For considering alive cells method of gene expression of 16S rRNAby RT-PCR was used. The obtained results showed that this pathogen in ES30 and DE treatments after three days enter in to VBNC state. According to obtained results ES10 treatment entering in to VBNC state on 5 days after inoculation. The results showed that there is the possibility of L. monocytogenes entering in to VBNC state, during brined and smoked fish or every other brined food product and defect of Standard detection methods.

Seafood is valuable protein sources for human being and acts important role in a healthy diet. Due to probability of fish contamination, from catch time to consume time with different microorganisms, there’s different technics to prevent fish spoilage. The present study purposed to investigate the effect of encapsulated thyme (Zataria multiflora Boiss) extract and chitosan to inhibit L. monocytogenes growth in filleted rainbow trout meat during refrigerated storage.The filleted samples were inoculated by1 ×103cfu/g of L. monocytogenes. Then samples exposed to 0.8 % and 1.2% thyme extract and 0.15 % and 0.25% v/w% chitosan nano particles and control group in five tratments. All treatments were kept for 16 days at refrigerator temperature. Every 4 days amount of Total viable count (TVC), Psychro trophic count (PTC) and Listeria monocytogenes counts measured. Least TVC, PTC and EBC in final experiment day observed in 0.25% chitosan treatment (p

The purpose of study was to evaluate the anti-oxidant and anti-bacterial activities of three species of green، brown and red algae from northern coast of the Persian Gulf، The study was performed using DPPH، FRAP، PMD and RP tests for anti-oxidant capability and disk diffusion and plate methods of ethanol extraction for anti-bacterial ability. In the current investigation، The best anti-oxidant activity and inhibition potential of DPPH free radicals and RP were shown in ethanol extract of Entromorpha intestinalis green algae and lowest values was detected in Cystoseira myrica brown algae. The highest anti-oxidant activity was measured by FRAP test in green algae E. intestinalis and the lowest anti-oxidant activity was obtained in the red algaeGracilaria corticata. The highest anti-oxidant activity with PMD test was found in the red algae G. corticata. However، anti-oxidant activity of the green algae E. Intestinalis was shown high activity with DPPH، FRAP، RP tests. Hydro-alcohol extraction of sea weed did not show any anti-bacterial properties.