مجله میکروب شناسی مواد غذایی
سال دوم شماره 4 (زمستان 1394)

The aim of this study was evaluatiing the amount of aflatoxin B1 and growth of Aspergillus flavus under effect of Lactobacillus plantarum and Lactobacillus sakei isolated from sourdough of whole wheat flour. After confirmation of mentioned isolated LAB with specific PCR, effects of these isolates on growth of Aspergillus flavus and their ability to reduction of aflatoxin B1 based on direct competitive ELISA, were examined. The effects of incubation time (37 °C in 0, 24 and 48 h) and heat treatment (autoclave for 15 min) on residue of aflatoxin B1 in present of mentioned isolated LAB were also determined. After six days period of investigation the effect of isolated LAB on growth of Aspergillus flavus, the diameter of fungi colonies in present of Lactobacillus plantarum, Lactobacillus sakei and control sample were 1.87, 6.5 and 9 cm, respectively. The amount of aflatoxin B1 residue, after 0, 24 and 48 h incubation in present of Lactobacillus plantarum were 63.6, 50.28, 45.34% and in present of Lactobacillus sakei were also 73.55, 71.7 and 63.17%, respectively. Furthermore, non-viable (autoclaved) cells of mentioned LAB reduced the amount of aflatoxin B1, more effective (P

Control of food borne diseases is a major concern and due undesirable side effects of chemical preservatives, there is more tendencies to natural preservatives such as spices for this purpose. Saffron is the most expensive spice that is is used as coloring and flavoring agent in foods. The aim of the present study was investigate antibacterial effects of hydro alcoholic extracts of saffron against pathogenic bacteria especially food poisoning species. For this purpose, one gram of finely powdered saffron was mixed with 10 ml of 2:8 (v/v) water- alcohol (ethanol or methanol) solution and mixed gently. Following incubation at room temperature, the suspension was centrifuged and the extract of saffron was harvested and dried. Sterile blank discs were saturated with extracts and their effects were evaluated in standard disc diffusion assay against six gram positive and six gram negative bacterial species. Simultaneously, the effect of standard antibiotics was evaluated against tested bacteria. The results revealed that Staphylococcus aureus, Bacillus anthracis, Bacillus cereus, Listeria monocytogenes and Brucella melitensis were the most susceptible species to ethanolic and methanolic extracts of saffron while Proteus mirabilis and Salmonella Typhi were resistant. The antibacterial effects of extracts were noticeable with regard to the standard antibiotics. All of the susceptible species in this study are important food borne pathogens and it is possible to use saffron as a natural preservative in food industry in order to control food borne pathogens.

Salmonella infections in many domesticated animals, wildlife and humans cause disease all of the world. The ability to enter and survive in host cells is a prerequisite for pathogenicity species of Salmonella. Salmonella invasion protein is an important virulence factors into host cells by bacteria transmitted. In this study we showed cloning the 5 'and 3' gene SipA Salmonella and was performed in E. coli.
In this study, by PCR and specific primers sequences of 5' and 3' SipA gene was amplified correctly. DNA fragment was cloned by T/A cloning technique in pGEM T-easy vector and transformed into E. coli.
Cloning of SipA gene was confirmed by PCR. The results of next step showed that the SipA gene was successfully cloned in E. coli. Final confirmation of construct was done by XbaI, BglII, SacI, XhoI restriction enzymes.
According to the results that, insertion of antibiotic-resistant genes between 5' and 3' regions of the SipA gene of Salmonella entritidis due to gene deletion in the bacteria. The construct's gene can be used as a target for gene vaccines against Salmonella entritidis in the future.

For evaluation and comparing effect of thyme and cinnamon on carcass contamination, 135 broiler chicks divided to 3 groups by 3 replicates. All chickens reared under same condition and received 0.5 percent thyme and 0.5 percent cinnamon on basic diet, continuously. Control chickens received no supplement in basic diet. In 42 days old, chickens were slaughtered and breast muscle was sampled for Escherichia coli (E.coli) detection. Cecal content were sampled for E.Coli colony counting, by conventional bacteriologic methods. Results showed that administration of 0.5 percent thyme can reduce carcass contamination and E.coli population in cecal content, significantly. There was no significant difference between control chickens and chickens received cinnamon for percentage of E.coli detection on carcass and cecal Ecoli population. all studied indices. According to results of this study, continuous consumption of 0.5 percent of thyme can improve hygienic quality in broiler chickens while this effect not expected for cinnamon.

Bacillus cereus is a food-born pathogen that 20% of total outbreaks of food intoxication in the world are caused by Bacillus cereus. Nowadays there is an increasing interest in the use of plant-derived antimicrobial compounds as natural preservatives for foods. Cuminum cyminum L. is a plant native to Iran that is used in traditional medicine and food products. The aim of this survey is providing of predictive mathematically models for evaluation of antibacterial effect of Cuminum cyminum L. essential oil on Bacillus cereus in a multi-factorial system. The essential oil of Cuminum cyminum L. plant was obtained by steam-distillation and analyzed by GC/MS. Then, effects of different concentrations of Cuminum cyminum L. essential oil (0, 0.005, 0.015, 0.030 and 0.045%) and storage temperature (10, 25 and 35°C) were evaluated on growth of Bacillus cereus in BHI broth during at certain intervals (1, 2, 3, 4, 5, 6, 9, 12, 15, 18, 21 24, 27, 30, 36 and 42 days). The growth of Bacillus cereus was significantly decreased by 0.015% EO concentration incubated at 10°C storage temperature and 0.030% EO concentration incubated at 25 and 35°C storage temperature (p

Hydrogen peroxide is commonly used as disinfectant for sterilization of food contact materials. In dairy industry, contamination of milk with H2O2 residue is likely due to its leakage from the disinfected surfaces resulting in development of oxidative spoilage of milk. Since no report has been documented on the prevalence of such contamination in food stuff in Iran, this study aimed to measure the prevalence of H2O2 in sterilized milk samples, collected from Isfahan market in 2013.
A total of 20 tetra-pack sterilized milk samples from 7 different brand were randomly collected from the market. All the samples were 250ml in volume. In order to measure the H2O2 concentration a colometric method was adapted based on catalase reaction and measurement of light absorption at 400nm.
H2O2 residue was detected in all tested samples ranging from 0.14-1.62 ppm. Fifteen samples (75%) contained H2O2 levels greater than its regulated level by international organization (0.5 ppm). Accordingly, the results of one-sample t-test showed that the average amount of detected H2O2 concentration in the tested sample is higher than the standard value.
Regarding the H2O2 contamination of the tested milk samples revealed in this study and due to lack of any regulation limit for H2O2 in sterilized milk in Iran, presentation and documentation of standards introducing reliable method for detection and monitoring of H2O2 in the sterilized milk along with its limits is highly recommended.

Staphylococcus aureus is one of important food poising bacteria. The bacterium cause this poising by produce of the different toxin. The aim of this study was determine the presence of toxic shock syndrome gene (tst) of S. aureus isolated from milk and traditional cheese. For this purpose 51 isolates included isolates of bovine milk (23), buffaloes milk (5) and traditional cheese (23) collected and were studies in tst gene by PCR. Among mentioned isolates 2(3.9%) isolates were positive for the tst genes belong to bacteria were isolated from cheese. Results of this study showed low prevalence of tsst-1 producing gene on Dairy products in mentioned area in comparison with similar study. It maybe this isolates harbored the mentioned gene in their genome transmit by worker on food industry