مجله میکروب شناسی مواد غذایی
سال یکم شماره 3 (زمستان 1393)

Listeria monocytogenesis an important psychotropic foodborne pathogen which may exist in fresh vegetables. Vegetables and their derivatives show a potential role in the transmission of Listeria to humans and epidemy of listeriosis. The objective of this study was to assess the prevalence of L. monocytogenesand to find out the frequency of hlyAgene in raw vegetables in Shahrekord، Iran. This cross-sectional study was carried out on 145 samples collected from vegetables market outlets in Shahrekord. Isolation of L. monocytogeneswas performed using specific medium. PCR was performed using hlyAgene specific primers. Also، all of the 145 samples were tested directly using PCR Totally، 56% of the samples were positive for Listeria in culture method. However، based on PCR، 56% out of 145 samples were infected to Listeria. Furthermore، hlyAgene was found in 67% of Listeria. The results indicate that the frequency of L. monocytogenesin the vegetablessamples of this region is relatively high.

Use of raw milk and dairy products containing aflatoxin M1 has led to concern in consumers. The aim of this study was to determine the aflatoxin M1 in raw cow milk in Qazvin Province. In this research، 170 raw cow milk were collected from dairy farm، dairy factories، milk collection centers and milk supply centers in Qazvin Province during winter 2013. The samples were analyzed with a commercial competitive enzyme-linked immune-sorbent assay (ELISA) kit and high-performance liquid chromatography (HPLC) for the samples with aflatoxin higher than 0. 5 ng/ml. Statistical tests including ANOVA and Tukey were used to analyze the data. Aflatoxin M1 contamination was observed in 100% of the milk samples. Among the milk samples (33. 52%) had a contamination of aflatoxin M1، higher than threshold level of The Institute of Standards & Industrial Research of Iran (0. 5 ppb)، while in 66. 48%، concentration of aflatoxin M1 was less than the limits permitted. The mean concentration of aflatoxin in dairy farm was 0. 215 ng/ml، in dairy factories was 0. 268 ng/ml، in milk collection centers was 0. 734 ng/ml and in milk supply centers was 0. 409 ng/ml. Due to high level of contamination observed in samples، regular monitoring of production and distribution of milk and dairy products is necessary.

Alicyclobacillusacidoterrestris is the main bacterial agent of fruit juice spoilage and the methods for its elimination are much paid attention to. Recently، using this phage for controlling bacteria in food products has received special attention. The aim of this study was to isolate the specific bacteriophages of A. acidoterrestris from soil. In this study، the samples collected from the soil around the Cedruslibani (Cedar) trees were investigated after being centrifuged and filtered to seek the understudied phage. Bacterial culture equal to0. 5 McFarland turbidity، isolated from fruit juice and confirmed by molecular and biochemical techniques، was prepared in AAB. Adding a certain amount of environmental samples allowed the phage to be replicated in the environmentcontainingbacteria. Then، the environment was centrifuged and the supernatant، which is the source of the phage، was filtered. The pure phage suspension was assessed in double agar method for studying the formation، shape and size of plaques. Plaque formation confirmed the presence of bacteriophages in the filtrate. Consequently، the heat and acid resistant bacteriophage was isolated from the soilaround the Cedruslibani (Cedar) trees. The results revealed the presence of specific bacteriophage of A. acidoterrestris. This phage can be used for eliminating of this bacterium in fruit juice. Stability of these bacteriophages in fruit juices its specific. Preserving the fruit quality side is of advantages of using this bacteriophage comparing to other methods.

This study was conducted in villages of Maragheh city to determine the contamination of Escherichia coli O157: H7 in traditional cheeses. A total of 100 cheese samples were cultured in Tryptic soy broth containing cefixime and then they were transferred to Mac conkey sorbitol agar containing cefixime and potassium tellurite. Suspicious colonies were stained (Gram staining) and identified by IMVC and other tests. Isolated Escherichia coli were tested for detection of O and H serotypes by direct agglutination method. Cheese samples were also tested for pH and NaCl content. Antibiogram test was done on Escherichia coli isolates by Kirby-bauer’s method. No Escherichia coli O157: H7was detected in the studied samples. In this study، other serotypes of Escherichia coli were isolated containing 32 non O157 serotypes. These serotypes including، Enteropathogenic (O55، O127، O86، O114، O44، O126، O125)، Enterotoxigenic (O20، O128) and Verotoxigenic (O26، O111). All of the isolated strains were resistant to Ampicillin and Polymyxin B. The effect of prevalence ratio of Escherichia coli serotypes from pH and NaCl content was not significant statistically (p>0. 05). From the results of this study it seems that traditional cheese could be a potent carrier to transmit the various serotype of Escherichia coli and cause disease in human.

Regarding that، the production of unpasteurized ice cream entitled to traditional ice cream is very common in our country and، on the other hand، the consumption of this product among different age groups especially children in warm seasons is high، Thus، the pollution of this product to pathogenic microorganisms could be the reason for food poisoning and infections in consumer. In this research، samples of traditional ice cream were collected from four regions of Urmia City (10 samples from each region) and transferred with in compliance with the standard condition for microbial testing to laboratory. The examination was conducted based on standard laboratory methods and the results were analyzed. The results showed that، in the mesophilic bacteria count 80% of samples in the entrobacteria count 92. 5% of samples were more than the standard rate. And in this case، the Escherichia coli bacteria 47. 5%، Staphylococcus 45% and Salmonella 40% was isolated from others. According to the results، using healthy and pasteurized milk in making ice cream، creating good condition for transit، and keeping milk، training for producers of ice cream to observance of personal hygiene in all steps of manufacturing and distribution of ice cream is essential and recommended

This research was done with the aim of study of the antimicrobial effects of Satureja khuzestanica on Lactococcus garvieae and on some spoilage characteristics of rainbow trout fillet in 4°C during 18 days of storage. To do so، 0. 06، 0. 12، 0. 25 and 0. 5 µg g-1concentration of the essential oil were added to the fillets. According to the results، the highest microbial load was observed in the control group and the lowest was observed in the fillets contained 0. 5 µg g-1 of the essential oil (P≤0. 05). The results also showed an increase in spoilage characteristics of the fillets at the end of the experiment showing a statistical difference for protein content (P≤0. 05). The results of this study revealed that S. khuzestanica results in the reduction of L. garvieaein fish fillets as the concentration of 0. 5 µg g-1 was the most effective.

Staphylococcus aureus as the second or third important food-borne pathogen all around the world. Ability of development and production of heat-stable enterotoxin in a wide range of the food made Staphylococcus has one of the most important factors causing the food poisoning. This study was done to investigate the prevalence of Staphylococcus in meat and meat products in Esfahan. From summer to winter 2012، 450 samples including raw beef (n=80)، minced meat (n=80)، lamb (n=80)، goat (n=80)، camel (n=50)، hamburger (n=40)، kebab (n=40) were randomly collected from butcheries and supermarkets in Isfahan، and analyzed for the presence of S. aureus. Totally، 234 (55/6 %) S. aureus were detected in meat and meat products. The mean count of S. aureus in positive samples was 8/3×102. The results indicated that although the percentage of contaminated samples was high، the number of bacteria presented in the samples is low with no potential risk for public health. To effectively manage the food production for decreasing diseases more epidemiologic investigations about S. aureustoxication are needed.

In this study، effect of different concentrations of nisin (0، 0. 25، 0. 5 and 0. 75 µg/ ml) were conducted against zoonotic bacteria Streptococcus iniae and Lactococcusgarvieae in fish fillet of rainbow trout (Oncorhynchusmykiss) in refrigerator storage. Lyophilized cultured of S. iniae (GQ850377) and L. garvieae (Ir-170A856bp) were obtained from Department of Aquatic Health and Diseases، Faculty of Veterinary Medicine، University of Tehran، Tehran، Iran، and were used in this study. After determination of incubation dose of two bacteria (1. 4×108 and 9. 2×107 CFU/ ml) and preparation of nisin solution، incubation of bacterial was done in fish fillets. The results revealed that different concentrations of nisin were statistically different in reduction of bacteria comparing with control group (P<0. 05). The highest inhibitory effect was observed in 0. 75 µg/ ml 65. 77% on L. garvieae and 60. 88 % on S. iniae. Thatresults showed that nisin، as a preservative، can be effective in control of food-borne bacteria in foodstuff.