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Background: Methicillin-resistant Staphylococcus aureus (MRSA) strains are one of the most important multidrug resistant microorganisms that threaten human health. Objective: The present study was conducted to evaluate genotypic and phenotypic characteristics of erythromycin resistance among MRSA isolates recovered from raw milk in Iran. Materials and Methods: A total of 50 MRSA isolates were recovered from raw milk. Tests for erythromycin and clindamycin susceptibility and inducible clindamycin resistance were done. In addition, the presence of the methicillin resistance determinant (mecA), erythromycin resistance genes (ermA, ermB, ermC and msrA) and an important virulence gene (Panton– Valentine leukocidin) were investigated using polymerase chain reaction (PCR) method. Results: Forty-eight percent (24/50) and 46% (23/50) of the isolates were resistant to erythromycin and clindamycin, respectively. Seven (14%) isolates showed inducible clindamycin resistance phenotype. The mecA gene was detected in 88% (44/50) of MRSA isolates. The incidence of the ermA, ermB, ermC and msrA genes was 14%, 64%, 12%, and 26%, respectively and the PVL gene was present in 18% (9/50) of MRSA isolates. Conclusion: According to the results of the study, the incidence of erythromycin resistance genes and inducible clindamycin-resistant MRSA strains was high in raw milk samples in Iran.

Background: One of the most important foodborne pathogen which causes enteritis is Salmonella enteritidis (SE). Human cases are mostly associated with the consumption of eggs and poultry meat. Objective: An experiment has been carried out to evaluate the impacts of a yeast product as liquid prebiotic on bacterial shedding, performance indices, and some breast meat characteristics of broiler chickens challenged with SE. Materials and Methods: A total of 90 one-day-old male broiler chicks (Ross 308) were randomly assigned to three different groups with three replicates for each treatment. The treatments were as follows: (1) CONT: birds were not challenged, (2) SE: birds were challenged with SE and fed with a control diet without prebiotic, and (3) SE+PREB: birds were challenged with SE and fed with liquid prebiotic. The challenge with SE was performed on birds in groups 2 and 3 at 28 days of age. Performance parameters and Salmonella shedding were determined on days 7 and 14 post infection. Twelve birds per treatment were sampled at the end of the trial for evaluating characteristics of breast meat. Results: The challenged birds which received prebiotic showed significantly higher body weight gain, lower feed intake, and lower SE shedding than SE group (P

Background: Tetracycline is one of the important antibacterial agents which is used against various bacterial infections. Different bacterial species and strains convey various tetracycline resistance (tetr ) genes. Objective: The present study was conducted to evaluate the occurrence of five tetr genes (tetA, tetB, tetC, tetD, and tetM) among Salmonella serovars obtained from humans and animals. Materials and Methods: A total of 60 different Salmonella strains previously recovered from humans, poultry, and animals were subjected to polymerase chain reaction (PCR) and sequence analysis of the genes. Results: In total, 6 strains were positive for the presence of tetA gene; three serotypes were also positive for the presence of tetC gene. The sequence analysis and phylogenetic tree showed similarities between the sequences of serovars in the present study and other Salmonella serovars and some other bacteria species in GenBank data. Conclusion: The results showed the great distribution of tetracycline resistance genes among Salmonella serovars with different sources which could be the effect of widespread use of the antibiotic particularly in the animals breeding farms.

Background: Prevention of foodborne pathogens is essential to control infectious diseases; Salmonella spp. is referred to as the most common causative agent of foodborne illnesses. Objectives: The current study aimed to determine the prevalence of Salmonella enterica subsp. enterica in broiler flocks in Mazandaran province, north of Iran and find the potential risk factors including: age, size of flock, strain, season, vaccination program and use of antibiotics. Materials and Methods: From March 2012 to December 2013, a total of 50 flocks were selected in slaughterhouse and 20 cloacal samples were collected from each flock. Every five samples were pooled and investigated for Salmonella spp. using polymerase chain reaction (PCR). Results: Thirteen flocks out of 50 (26%) were positive for Salmonella species. Chances of Salmonella spp. detection was higher in flocks with lower age (P = 0.41). Increasing flock population was associated with increased chance of Salmonella spp. isolation (P = 0.21). The risk of salmonellosis in broiler flocks was increased when no antibiotics were given to day-old chicks. There was no significant difference (P = 0.30) in the prevalence of salmonellosis among different broiler strains. Conclusions: In the current study, six risk factors were assessed for Salmonella spp. contamination in broiler flocks. Some of these factors contributed to the risk of salmonellosis in broiler flocks.