[Antimicrobial effects of some traditional plant essential oils on Clostridium perfringence]

Clostridium perfringence is one of the most important pathogens in animals and cause a lot of death in sheeps and goats every year. In human C. perfringence cause food intoxication and gastroentritis. This study was conducted to determine the antimicrobial effects of essential oils of Thymus daenensis, Hypericum Scabrum, pimpinella anisum on clostridium perfringens in the laboratory culture media. After extracting the essential oils by Steam Distilation method, antimicrobial activity were examined by two methods. At first in the plate method after culturing bacteria on the plate containing Nutrient Agar, 5 mm diameter hole was made by the sterile pastuer pipte and 0.1 ml of each essential oils was added to each whole separetely. In the second step tube dilation method containing Tyoglycolate broth was used to determining the MIC and MBC of the essential oils. The results showed that the pimpinella anisum oils had not any effect on growth of C. perfringence, but the mean value of inhibitory zones for thymus daenensis and Hypericum Scabrum oils were 8.1 +/- 0.2 and 6.03 +/- 0.15 respectevely. The MIC for thymus daenensis and Hypericum Scabrum oils were 5% and 15% respectively. The results showed that the MBC of Thymus daenensis and Hypericum Scabrum oils for C. perfringence were 20% and 40% respectively. Regarding to the results of this study it is posible to use these essential oils as a natural preservative in foods also as a disinfectant on infected tissues

[Virulence genes of verotoxigenic E. coli isolated from raw milk and unpasturized cheese]

Verotoxigenic strains of E. coli mostly contain one or both of stx1 and stx2 genes. Both of these genes play a role in pathogenicity of the bacteria. These strains cause bloody diarrhea, uremic haemolytic syndrome and purpura thrombocytopenia. Because of a high probability of the presence of verotoxigenic strains of E. coli in various foods, especially milk and cheese, and due to the importance of these strains to human health, we aimed to determine the presence of verotoxigenic strains of E. coli in unpasteurized milk and cheese by PCR. In this study, 200 samples of raw milk and 80 samples of unpasteurized cheese were collected, and verotoxigenic E. coli were isolated using selective media. PCR was used to determine some virulence genes including stx1, stx2, eaeA and hlyA. Thirty-eight and 14 E. coli samples were isolated from raw milk and unpasteurized cheese, respectively. The isolates were examined by PCR in order to find the O157:H7 specific DNA and stx1, stx2, eae and hlyA genes. Two out of 38 isolates originating from raw milk were typed as O157:H7, both of them containing stx2, eaeA and hlyA genes. Another isolate, which was not O157:H7, also contained the stx2 gene. No isolates possessed the stx1 gene. None of the isolates originating from unpasteurized cheese samples contained any of the virulence genes

Isolation of enterotoxigenic and enteroaggregative straines of Escherichia coli from chicken carcasses by PCR

The aim of this study was to determine the frequency of enterotoxigenic and enteroaggregative strains of Escherichia coli in chicken carcasses by polymerase chain reaction [PCR]. In this study 63 strains of E. coli were isolated from 110 samples of chicken carcasses during processing after chilling in the poultry slaughter house of Shahrekord. Polymerase chain reaction assays were used to detect the presence of the genes encoding heat-stable enterotoxin a [STa], heat-stable enterotoxin b [STb], heat labile toxin [LT] and Enteroaggregative heat-stable toxin 1 [EAST1]. Sixty three out of 110 [57.27%] carcasses were contaminated with E. coli. Six out of 63 [9.52%] harbored the gene for LT, 1 [1.58%] STb, 21 [33.3%] EAST1 and 8 [12.69%] contain both LT and EAST1 genes. None of the strains contain the STa gene. The results indicated that contamination of the chicken carcasses with E. coli in such a level could be a potential hazard for consumers

effects of some herb's essential oils on S. aureus in feta cheese

This study was conducted to examine the effectiveness of some plant essential oils for control of growth and survival of S. aureus in pasteurized cheese. Essential oils from Thyme [Thymus vulgaris], Tarragon [Artemisia dracunculus], caraway seed [Carum carvi], Penney royal [Mentha pulgium] and Peppermint [Mentha piperita] were extracted by Steam Distillation Method. Two concentration close to the level of MIC for each essential oils [Thyme 0.1 and 0.2%, and the others 0.3 and 0.4%] were induced in samples and 10[6] CFU/g bacteria [S. aureus] was inoculated into the samples and controls. All the samples and controls were kept at 12°C [The optimum temperature for ripening of cheese] for 168 h. Samples and controls were checked for the number of inoculated bacteria on 0,24,48,72 and 168 h. The results of this study showed that the essential oils of these plants have antimicrobial activity on S. aureus, essential oils of the Thyme showed the most and for Tarragon the least antimicrobial activity on tested bacterium. The Thyme oils caused 2 and 4 Log reduction of 5. aureus to control at 0.1 and 0.2% in cheese after 168 h. The essential oils of the Caraway seed, Penney royal and Peppermint had moderate effect on S. aureus and caused 1.5 and 2 Log reduction in the number of bacteria in the samples to controls. The Tarragon oils caused 0.8 and 1.2 Log reduction to control at 0.3 and 0.4% after 168 h. From the results of this study it is concluded that essential oils of some plants may use as a natural preservative in some foods