---

Background and objectives: Salmonella is one of the important food poisoning agents. The common method for its identification in foodstuffs is by using media cultures. This method is timeconsuming and does not have good precision. In the present study we compared PCR as an alternative, rapid and more precise method in identification of Salmonella Typhimurium serovar in milk purchased from the local supermarkets. Materials and methods: Six pasteurized milk sample bags were purchased and divided in 2 parts 3 were contaminated manually with different numbers of Salmonella typhimurium (10-1 –103), the other, non-contaminated, 3 being used as control. All were enriched in BPW (buffer peptone water) media and analyzed by both the PCR and common bacterial culture methods. Results: The PCR method could identify 10, 5, and 1 Salmonella typhimurium in the contaminated samples after 8, 12, and 16 hours of enrichment with BPW, respectively. Identification by the common culture media required a longer time (4-6 days) and was less precise. All the purchased milk samples were found to be free of any contamination with Salmonella typhimurium, using either both methods. Conclusion: These findings show that by using the PCR method it is possible to isolate and identify Salmonella typhimurium in milk in less than 24 hours with at least one bacterium in the sample, while with the culture media methods the time required is 4-6 days. Furthermore, in spite of good agreement between results obtained by the 2 methods, the PCR method has a higher precision and sensitivity.

---

Background and Objectives: Staphylococcus aureus as the third important factor in diseases of food origin are discussed. Milk raw material suitable for the growth of Staphylococcus aureus and dairy products, the source is documented for Staphylococcal poisoning. Materials and Methods: This study determined the prevalence Staphylococcus aureus local cheese in West Azerbaijan by culture and PCR techniques has been done. Total 85 samples randomly selected collected form West Azerbaijan. Results: Based on the culture method 7. 05% of on samples infected with Staphylococcus aureus 14. 11% of samples infected with Staphylococcus intermedius finding indicates that 21. 17% of sample infect with coaglase positive Staphylococcus 48. 23% of samples infected with coaglase negative Staphylococcus. Conclusion: This necessitates attention observation concerning hygienic conditions during production and requires the use of pasteurized milk to produce cheese. Keyword: Staphylococcus aureus, Local cheese, Culture, PCR

---

Background and Objectives: The aim of this study was to investigate prevalence of Coxiella burnetii in milk samples of dairy cow, sheep and goats using PCR method in Mazandaran Province, Iran.
 Materials & Methods: From May 2018 to December 2018, a total of 200 raw milk samples of cows, sheep and goats were randomly collected from Mazandaran Province. These samples were tested for Coxiella burnetii using polymerase chain reaction assay with two various primers.
Results: In this study, the aim was to investigate the prevalence of Coxiella burnetii using polymerase chain reaction by comparing two types of primers. Using Trans primer, a total of 19 samples [17 sheep milk samples (17.52%) and two cow milk samples (2.70%)] were positive for Coxiella burnetii while none of the goat milk samples were positive. Using the OMP primers, none of the samples were positive and the results showed that the Trans primer included a further ability to detect Coxiella burnetii. Prevalence of Coxiella burnetii was higher in autumn and winter than in other seasons (p < 0.05). The highest frequency of positive samples was linked to Joybar City with eight samples (66.67%) and the lowest frequency was linked to Mahmoud Abad with one sample (11.11%). The number of positive samples detected by Trans primers was 16 (8.60%) in the traditional unit and two (20%) in the semi-industrial unit. However, no positive samples were detected in industrial units. Moreover, the number of positive samples by Trans primers was 12 (12.90%) from the bulk tanks and seven (6.55%) from individual samples. Studying prevalence of contamination and risk factors reveals importance of the infection for health officials.
Conclusion: Results of this study showed that Trans- polymerase chain reaction method included a further ability to detect Coxiella burnetii infection. Prevalence of Coxiella burnetii varied in various seasons; hence, prevalence of Coxiella burnetii was higher in autumn and winter than in other seasons. For control and prevention, further studies on epidemiology of Coxiella burnetii from raw milks and prevalence of Q fever in the society are necessary.

---

Background and Objectives: Fermented foods have long been important due to their microbiota, which includes lactic acid bacteria and their metabolites. These beneficial bacteria can assist the food sector in generating health-oriented products by releasing bioactive peptides such as bacteriocins.
 Materials & Methods: In the present study, antagonistic characteristics of Lactobacillus isolated from Iranian Motal cheeses were assessed and growth kinetics and production of bacteriocin compounds by these isolates were studied. Furthermore, resistance of bacteriocin compounds at various pH and temperatures under effects of protease enzymes was assessed.
Results: By carrying out phenotypic and molecular assessments, 23 Lactobacillus isolates were selected and their antagonistic effects were investigated. The isolates included better antimicrobial effects on Gram-positive bacteria and three isolates (LM11, LM52 and LM56) that showed stronger effects were selected for further studies. By optimal growth of the isolates at mesophilic temperature, pH of the microbial suspension decreased while bacteriocin activity increased. Moreover, bacteriocin activity of all three selected strains decreased significantly at 100 °C, but the bacteriocin compounds were stable at 80 °C, except the LM56 strain. Moreover, pH changes did not result in a significant decrease in bacteriocin activity while bacteriocin activity significantly decreased when bacteriocin metabolites were exposed to pepsin and trypsin.
Conclusion: In this study, associations between the antagonistic effects of Lactobacillus isolates and their bacteriocin compounds, protein nature of these compounds and their high stabilities under various conditions were established.