The inhibitory effect of Lactobacillus rhamnosus LGG 23527on growth and enterotoxin A gene expression of S. aureus ATCC 29213

Document Type : Research Paper

Authors

1 Assistant Professor, Department Food Hygiene, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran

2 Assistant Professor, Department Food Hygiene, Faculty of Veterinary Medicine, Amol University of Special Modern Technologies, Amol, Iran

Abstract

    Increase shelf life, food safety and human health improvement by using the natural microflora are the dominant issues in public health. In this research, the effect of Lactobacillus rhamnosus (LGG) isolate with intestinal origin was studied on growth and enterotoxin production by Staphylococcus aureus and then, Staphylococcus aureus enterotoxin A gene expression was evaluated in a laboratory media. Therefore, this strain (1*107 cfu / ml) and Staphylococcus aureus (1*105  cfu / ml) were inoculated in TSB and  incubated in two temperatures at 25 and 35°C, at the time of zero, 24, 48 and 72 hours, the mixed cultures were counted in specific media. Staphylococcus aureus without lactobacillus was incubated as control and then enterotoxin production evaluated by using ELISA kit and the gene expression of the SEA of S. aureus in mixed and control cultures was also evaluated by RT Real Time PCR technique. The lactobacillus isolates decreased Staphylococcus aureus growth compared to control samples 3 log at 25°C and 2 log at 35°C. The enterotoxin production of A, C and E at 25° and enterotoxin type E and A at 35°C was inhibited by Lactobacillus rhamnosus. Comparison of gene expression SEA between treated and control cultures showed the gene expression of the SEA was significantly suppressed 6.82 fold in S. aureus co cultured with studied lactobacillus isolate at 25°C  while it was not significant to 35 °C (P<0.05). Because of the reduced effects of the isolates seen in this study, proposed it for natural prevention of bacterial growth/toxin production in foods to improve the quality and safety of the foods.

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