مجله میکروب شناسی مواد غذایی
سال سوم شماره 3 (پاییز 1395)

Listeriosis is one of the most important food-borne diseases caused by Listeria species especially L. monocytogenes. The objective of this study was to determine the prevalence and antimicrobial resistance of Listeria species isolated from three types of fish filet in Isfahan and Bandaranzali. From August 2009 to April 2011, a total of 120 samples of Argyrosomus hololepidotus (n= 90), Scomberomorus commerson (n=80) and Alburnus spp (n=70). Fish were obtained from randomly selected retail stores in Isfahan and Bandaranzali cities and were evaluated for the presence of Listeria spp. using standard cultural and PCR methods. Then antibiogram test were done for determination of antimicrobial resistance. Seven (8.8%) and 6 (15%) of smoked and salted fish samples were positive for Listeria spp. respectively. L. monocytogenes, L. innocua and L. seeligari were isolated from 2.5, 6.7 and 1.6% of fish samples. Overall, 9 of 13 Listeria isolates (69.2%) were resistant to one or more antimicrobial agents. Resistance to tetracycline (53.8%) and tetracycline (30.8%) were the most common finding. All of the isolates were susceptible to gentamicin, vancomycin and chloramphenicol. The results of this study indicate the potential risk of infection with Listeria in people consuming raw or under cooked smoked and salted fish. Also, the results obtained in this study indicated the need for an appropriate strategy of surveillance and epidemiological monitoring to control the development of resistance. The results of this study indicate the potential risk of infection with Listeria in people consuming raw or under cooked smoked and salted fish. Also, the results obtained in this study indicate the need for an appropriate strategy of surveillance and epidemiological monitoring to control the development of resistance.

Totally 150 samples of cow milk were collected in Ahvaz within 6 months. The collected samples were sent to the lab in cool conditions. The amount of 25 ml of each sample was added to 225 ml of Tris-Buffered Peptone Water with pH=8 as enrichment medium and stored at 4°C for three weeks. Then in 7th, 14th and 21th days of storage, one loopful equal to 10 µL of enriched broth were streaked out in plates of Cefsulodin-Irgasan-Novobiocin agar contained supplement and incubated at 30°C for 24 hours. Then 3 to 5 colonies of typical bulls-eye appearance with 0.5-2 mm diameter with a deep red center and sharp border surrounded by a translucent zone were selected as suspect to Yersinia enterocolitica and cultured in TSA medium. After gram staining and observe gram negative rod and also implement some biochemical tests in next step due to absolute identification, specific primers for 16srRNA were used. Boiling method was used to extract DNA. The isolation of Yersinia entroclitica was confirmed from 36 samples (24%) of milks. The confirmed isolates due to antibiogram were spread out in agar culture and the antibiotic susceptibility was surveyed with utilization of antibiotic discs and CLSI tables. The results showed that the sensitivity to Ciprofloaxin, Gentamicin, Tetracycline, Ceftazidime, Nalidixic Acid, Kanamycin, Trimethoprim Sulfametaxazole, Amoxicillin and Cephalotin were 100%, 97.05%, 91.17%, 85.29%, 82.35%, 79.41%, 67,64%, 17.64% and 14.7% respectively. None of the isolates were susceptible to Erythromycin which shows that the isolates have the most resistance against this antibiotic.

In this interventional investigation, the effect of methanol extract of Eryngium Caeruleum and Mentha Spicata (5% and 10% v/w) on Staphylococcus aureus in soy cheese at 106 cfu/ml at 15˚C for a period of 15 days was studied. Methanol extract of Eryngium caeruleum and Mentha Spicata was prepared by soaking dried plants in 85% methanol. Soy cheese was made through coagulating of soy milk by calcium sulfate. Results were analyzed by one-way variance, ANOVA. In 15˚C, Staphylococcus aureus was faced with reduction in both concentrations (5% and 10% v/w) of methanol extract of E. caeruleum i.e. 1 and 2 log, and in both concentrations (5% and 10% v/w) of methanol extract of M. Spicata i.e. 2 and 4 log, respectively. The antibacterial effect of 10% extract of both of the plants on Staphylococcus aureus was more than 5% extract. Generally, results suggested that Eryngium caeruleum and Mentha Spicata have antibacterial effect, on Staphylococcus aureus.

Sarcocystis is one of the most prevalent parasitic protozoa infecting human and animal with worldwide distribution. Cattle as an intermediate host of Sarcocystis are important sources of meat production for human. The aim of this study is determine of prevalence of Sarcocystis in hamburgers in Kashan region, central Iran. This descriptive study was conducted in Kashan region, 2015. Two hundred humburgers pieces with approximately 60% meat randomly collected in different brands. About 15-20 gram of each pieces digested in digest solution overnight at 28 °Caccording Douby method. Two smear prepared from sediment and stained by gimsa solution and microcopy examined for Sarcocystis cystizoite by 400 and 1000 maginification. Totally, 52.5% of samples were positive for sarcocystis spp. in various degrees. Forty samples (38.5%) of humburgers with 60-75% meat and 66 sample (68.75%) of humburgers with 90% meat were infected. High prevalence of infection to microscopic cyst of Sarcocystis in humburgers indicated a high rate of infection in meat production animals. Properly cooked meat before consumption is recommended for prevention of infection. Monitoring of health condition and food of animal which act as intermediated host and kept them from definitive host can be effective in decrease of animal infections.

This study aimed to investigate preparation of a Zataria multiflora essential oil nanoemulsion and to evaluate its antibacterial against Salmonella Typhimurium and Listeriamonocytogenes. The average particles size of nanoemlusion prepared by inversion phase using tween 20, which measured by dynamic light scattering, was 66.5 nm. The antibacterial activity of nanoemlusion has examined through agar diffusion, vapor-phase diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time kill curves against Salmonella Typhimurium and Listeriamonocytogenes in BHI. The average diameter of the zones of inhibition of nanoemlusion through agar diffusion was 8.3 and 8.54 mm for S. typhimurium and L. monocytogene, respectively. Also, average diameter of the zones of inhibition of nanoemlusion was zero against both bacteria according to vapor-phase diffusion. The results showed that nanoemlusion exhibited MIC and MBC of 5000 µg/ml on S. typhimurium and MIC and MBC of 2500 µg/ml on L. monocytogene. The effect of 10, 100 and 1000-fold diluted nanoemlusion on both bacterial kill in BHI at 0, 15, 30, 45 and 60 minutes and the results showed that in BHI, the 10 and 100 fold-diluted nanoemlusion caused a 6 and 4 log reduction at S. Typhimuriumin 60 min and the 10-fold caused more than 4 log reduction of L. monocytogene. According to the results, it can be concluded that prepared nanoemlusion is suitable antimicrobial solution and by optimizing the process, it can be beneficial to control the bacterial microorganisms of foods.

Many bacteria possess the ability to connect to surfaces that this ability to "biofilm" is called. Biofilms attached to the food industry for the production of many problems in the production line and the final product is therefore necessary to examine methods of controlling them. In this study, the bacterial biofilm from the inner part of pasteurized milk production line from one factory in Isfahan were isolated, purified and identified (by biochemical tests). After that, bio-surfactant was extracted from Lactobacillus rhamnosus ATCC 7469. Then the anti-adhesively effect of bio-surfactant was performed by micro-titer-plate method and optical density was read with ELISA Reader. Finally, data factorial analysis of variance to test and comparison of means were analyzed method LSD at 5%. Results showed Staphylococcus was the most predominant isolated genus with 19% of the whole population. Also the average of anti-adhesively effect of bio-surfactants used in this study is 42.8%. The highest effect of bio-surfactants was on Klebsiella pneumonia with 82.3% for reducing connection and the least effect was on Staphylococcus aureus with 4.2%forreducing connection. However, due to the positive anti-adhesively effect of bio-surfactant, use it in the production line during the CIP process is recommended.

Heat-loving bacteria Bacillus Alicyclobacilluschanging flavor juices and ready to use in recent years in a wide range of large amounts of fruit juice was corrupt world, although there is no previous report indicating its pathogenesis. This research was done to study contamination of packaged juice with the bacteria. A total of 300 samples of pomegranate juice, apple juice, orange juice, mangoes juice, pineapple juice, grape juice (from different companies) at Esfahan was collected and studied for Alicyclobacillus contamination. The samples were tested using culture, biochemical tests and PCR. According to the results, 13 samples (4.33%) were contaminated with Alicyclobacillus. The highest level of contamination among samples was found in pomegranate juice and orange juice (13.3%). Contamination in cranberry juice, mixed species and other samples was 10, and 6.66 %. No contamination was found the other species. Regarding to the obtained results, prevention of bacterial growth especially during storage time and detection of bacteria after pasteurization is necessary.

Seafood has found its way into eating habits of consumers. However, it can be accompanied with some hazards such as transmission of pathogenic bacteria. The origin of disease can be either a fish pathogen or a secondary contamination. Vibrios are of the important bacteria which are naturally found in the environment and in the aquatic animal's body as microflora and results in vibriosis if ingested raw or undercooked. The most important species are Vibrio parahaemolyticus, V. Cholera, V. vulnificus and V. alginolyticus. Although vibrio species are distributed worldwide, but it seems that they are more prevalent in some areas due to nutritional habits. This article reviews important species, source of infection and the previous reports.