The Effect of Water Extract of Rhus Coriaria L. on the Pathogenic Bacteria at Different Temperatures

BACKGROUND AND OBJECTIVE: Nowadays, natural preservatives are used in food industries rather than synthetic ones. Sumac fruit (Rhus coriaria L.) is widely used as an additive in meat products due to its antimicrobial effects. This study was conducted to examine antimicrobial properties of sumac at various temperatures. METHODS: In this experimental study, the extract of sumac was prepared using soaking method. Different concentrations (3.12-50 mg/ml) of the extract were used against S. aureus, L. monocytogenes, S. typhimurium, and E. coli O157:H7 bacteria. Growth assessment curve, minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC) were evaluated using microplate method. FINDINGS: The results of this study demonstrated that MIC (6.25 mg/ml) and MBC (12.5 mg/ml) belonged to S. aureus and L. monocytogenes bacteria, respectively. The extract could significantly attenuate growth of the four bacteria at 4°C and 25°C (p<0.05). The effect of the extract on Gram-positive bacteria was significantly more than Gram-negative ones (p<0.05). Temperature reduction also affected the growth of the bacteria; at 4°C bacterial growth was less than 25°C, that is, at 6.25 concentration, S. typhimurium, and E. coli populations reduced from 3.55 log and 3.31 log to 2.14 log and 1.06 log, respectively. CONCLUSION: According to our findings, water extract of sumac is a viable alternative to chemical food preservatives, particularly at 4°C

Detection of toxic shock toxin (tst) gene in Staphylococcus aureus isolated from bovine milk samples

Staphylococcus aureus is a major causative pathogen of clinical and subclinical mastitis in dairy cattle all over the world. This agent produces a variety of extracellular toxins and virulence factors in-cluding toxic shock syndrome toxin-1 (TSST-1) which is the major cause of toxic shock syndrome (TSS). In the present study, 76 S. aureus isolates have been obtained from milk samples collected from 7 dairy herds in Hamedan province of Iran. The isolates were identified based on the biochemical and molecular methods using PCR amplification of the femA gene. The staphylococcal isolates were also examined for the presence of TSST-1 (tst) encoding gene. This gene was detected in only one S. aureus isolate (1.3%). The results revealed that S. aureus strains causing bovine mastitis may potentially produce staphylococcal toxic shock syndrome toxin-1, indicating that it is very important to follow the presence of TSST-1 producing S. aureus isolates in foodstuffs to protect consumers against the risk of toxic shock syndrom