مجله میکروب شناسی مواد غذایی
سال پنجم شماره 3 (پاییز 1397)

In the past two decades, Enterococci resistant to some antibiotics has gained widespread that it would cause complications in the treatment of infections caused by these bacteria. Since meat as a foodstuff consumed in Iran is common and easily contaminated with bacteria therefore, we decided to detect frequency of antibiotic resistance genes in Enterococcus faecalis isolated from meat in Shahrekord. This cross sectional study was conducted on 104 samples of meat in 2016 in Shahrekord. Isolation of bacteria using by biochemical methods and confirmed with detection of 16srDNA gene, and antibiotic resistance genes isolates using by Kirby-Bauer method and molecular method for detection of tetM, ant (2'')-I, erm B and aac (6')/aph (2') genes. Most bacterial resistance to streptomycin (2/95%) and sensitivity to vancomycin (100%) were estimated. Prevalence of ermB gene reported 76.9% and prevalence of aac (6')/aph (2') gene reported 40% in E. faecalis isolated. The results indicate that is not resistance to vancomycin in E. faecalis isolated from meat in Shahrekord, but high resistance to Streptomycin, Cefotaxime, Meropenem, Erythromycin, Tetracycline were found also found that ermB gene in E. faecalis high prevalence of antibiotic-resistant gene is the most abundant strength.

The high consumption of mayonnaise and its improper maintenance procedures cause that the use of natural essence in mayonnaise becomes important. In this research, the effects of different concentrations of essential oils of marjoram on physicochemical, microbiological and sensitive characterization of mayonnaise were investigated. The influence of three different concentrations of Marjoram essential oil (100,150, 200 and 250 ppm), two different temperatures (4 and 15 °C) and storage times (0, 1, 2, 3 and 4) months were examined. The obtained results from microbial experiments (Total count of microorganisms, mold and yeast, Salmonella, Coliform, Staphylococcus aureus and Lactic acid bacteria), chemical experiments (Peroxide, Thiobarbituric index, pH and acidity) and sensitivity analysis were evaluated based on fully factorial experiment design and the Duncan test. The results indicated that by increasing the concentration of Marjoram essential oil, the index changes of chemical tests decreased in all of times storage. The maximum effect of Marjoram essential oil on mayonnaise for preventing deterioration of mayonnaise was at the storage temperature of 4 oC. The Marjoram essential oil having 200 ppm at the temperature of 4 oC had the maximum effect for the preventing mayonnaise deterioration. Also, the experimental results that, the chemical and microbiological characteristics of mayonnaise were kept suitably. Therefore, the best optimal strategy of mayonnaise production is in these conditions.

Vibrio parahaemolyticus, a member of family Vibrionaceae, is a non-spore-forming, rod-shaped, gram-negative and halophilic bacterium with a single polarflagellum known as seafood-borne gastroenteritis throughout the world. These bacteria are characterized by three major clinical manifestations, including wound infection, primary septicemia and gastroenteritis. Accordingly, the present cross-sectional study aimed to detect V. parahaemolyticus using PCR method in 80 fresh shrimp samples collected from different seafood centers in Ardabil, Iran. The samples after immediately homogenization were cultured in TCBS agar. The resulting isolates were identified by biochemical tests, and then typical colonies were selected for DNA extraction. Next, the PCR technique was employed to detect the presence or absence of vp-toxR gene as a marker of these bacteria. Based on the findings, 11 (13.75 %) out of 80 fresh shrimp samples were positive for V. parahaemolyticus. According to the results, shrimp could be the major sources of V. parahaemolyticus thathave a potential risk to the public health inasmuch as might be viable and infectious.

The purpose of this study was to investigate the effect of oligofructose and type of microbial culture on conjugated linoleic acid (CLA) and viability of probiotic bacteria in probiotic yogurt. The amounts of 3 and 5 percent of oligofructose were used in probiotic yogurt containing Lactobacillus acidophilus or Bifidobacterium lactis. (The control sample was considered without adding the prebiotic compound). The viability of probiotic bacteria, CLA content, pH, acidity and sensory properties of probiotic yogurt were investigated at intervals of 1, 11 and 21 days. During storage, the number of probiotics and pH of the samples decreased but acidity increased significantly (P<0.05). The amount of CLA increased significantly in the majority of samples during storage (P<0.05). However, the score of overall acceptance of the majority of the samples did not change significantly during storage. The highest population of probiotic bacteria was belonged to sample containing Lactobacillus acidophilus + 5% oligophroctase. After control 1 sample (sample containing L. acidophilus), sample containing L. acidophilus + 3% oligofructose had the highest concentration of CLA. After control 1 sample, sample containing L. acidophilus + 3% oligophroctase had the highest sensory score (overall acceptance) which also had a high population of probiotic bacteria (4.6 × 106 CFU/ml) at the end of the maintenance period. Therefore, it can be said that prebiotics have a positive effect on survival of probiotics and CLA content in probiotic yogurt so can improve health properties of probiotic products.

This study aims at investigating the outbreak of Salmonella and Disease-Agent Genes Pf Salmonella interitidis and Salmonella typhimurium separted from bison milk and its products and bison meat in Khuzestan province- Mollasani town. On the Whole, 210 samples of meat, milk and its products in Esfand 94 and Farvardin 95 have been collected from Mollasani town. Samples have been analyzed for the presence of S. interitidis and S. typhimurium and Disease- Agent Genes. The outbreak of Salmonella in the studied sample was 2.8%. Highest out breaks of contamination were respectively in cheese sample 10%, cream 7.14% and 2.5%. No Salmonella was detected in meat, yogurt, butter and rice pudding. The separated Salmonella in the sample were S. interitidis 5% and S. typhimurium 2.5%.

Staphylococcus aureus is one of the main causative agents of food poisoning in human. Occurrence of severe antibiotic resistances has increased the importance of this bacterium. The present study was carried out to assess the prevalence rate and antibiotic resistance pattern of S. aureus strains isolated from vegetable and salad samples in Chaharmahal Va Bakhtiari Province. In this study, 485 samples of vegetable and salad were collected and immediately transferred to the laboratory. Samples were evaluated by microbial culture and the isolated S. aureus strains were analyzed for the antibiotic resistance pattern using the disk diffusion method. The prevalence rate of S. aureus in vegetable and salad samples were 16% and 11.91%, respectively. The highest (26.50%) and the lowest (6.72%) contamination rates were observed in Lordegan and Shahrekord cities. A Significant statistical difference was observed for the prevalence of S. aureus between vegetable and salad samples (P<0.05). S. aureus strains isolated from vegetable and salad samples had the highest prevalence of resistance against penicillin (95.58%), tetracycline (88.23%), ampicillin (79.41%), erythromycin (72.05%) and methicillin (70.58%) antibiotics. The lowest prevalence of antibiotic resistance was reported against imipenem (7.35%), chloramphenicol (22.05%), cotrimoxazol (26.47%) and co-amxiclave (29.41%). Judicious prescription of antibiotics according to the results of the disk diffusion method can reduce the risk of resistant S. aureus in vegetable and salad.

The aim of this study was to investigate the prebiotic potential of Roman nettle seed mucilage in the growth and survival of Lactobacillus rhamnosus (LGG) as well as changes in different physicochemical, reological and sensory properties of fermented milk compared with inulin (commercial prebiotic) during the storage time. For this purpose, values of 0.025, 0.05, 0.1 and 0.2% (w/w) of nettle seed mucilage and 0.5 and 1% (w/w) inulin has been added to the recombined milk and after inoculation of bacteria, changes in acidity, syneresis, viscosity, the number of probiotic bacteria and sensory properties were studied during 21 days. The results showed that the addition of mucilage to fermented milk improved the growth and survival of L. rhamnosus and subsequently increase the acidity of the samples. Furthermore, the addition of mucilage compared with inulin, led to reduction in syneresis of the samples and higher counts of probiotics during storage. Finally, according to physico-chemical, microbiological and organoleptic results, samples containing 0.1% (w/w) of mucilage were considered as the best sample in this study.

Curdlan is water-insoluble and expensive polysaccharide that is made up of D-glucan monomers with b- (1→3) bonds. The properties of the gel created by the heat make Curdlan very important in the food industry. One of the main limiting factors for using Curdlan is its production cost. Agricultural waste can be used as a cheap substrate for its production. In this research, Curdlan production of was evaluated by Agrobacterium radiobacter PTCC 1654 in a culture medium different concentrations (5, 7.5 and 10%) of grape syrup and neat sucrose as carbon source. Based on the yield of Curdlan production, the optimum carbon source was determined. Moreover, the amount of produced Curdlan and biomass was measured. The polysaccharide sugar composition was evaluated by thin-layer chromatography technique. The pH change of the medium was also evaluated during the fermentation process. The results showed that the highest amount of polysaccharide was obtained in fermentation medium containing grape syrup with 7.5 Brix and after 144 hours. The pH of the fermentation medium decreased from about 7 to about 5.5 during the fermentation process. The results of thin-layer chromatography of polysaccharide showed that the glucose was the only monomer in the polymer's structure. In grape syrup medium Curdlan production in grape syrup was significantly higher than sucrose medium (p<0.05). Grape syrup is a cheap substrate widely available in Iran and has potential for Curdlan production.