Isolation and rapid screening of emetic toxin producing Bacillus cereus strains in foodstuffs based on groEL, ces, and cer genes, using an improved Polymerase chain reaction assay
Isolation and rapid screening of emetic toxin producing Bacillus cereus strains in foodstuffs based on groEL, ces, and cer genes, using an improved Polymerase chain reaction assay
Esmaeil Ghorbanalinezhad,1,*Donya Jodairi Mojaveri,2
1. Faculty of Department of Microbiology, Islamic Azad University of Tonekabon branch, Tonekabon, Iran 2. Master student of Microbiology, Islamic Azad University of Tonekabon branch, Tonekabon, Iran
Introduction: Bacillus cereus is a rod shape spore forming gram positive bacterium. This bacterium known as cosmopolitan food born poisoning agent. Many of Bacillus cereus strains causes diarrhoeal and emetic form of food poisoning. Diarrhoeal diseases causes by haemolytic and nonhaemolyic enterotoxins such as Hbl and Nhe Respectively, and Cytotoxin K. Emetic type of diseases causes by emetic toxins that coded by the responsible genes such as groEL, cer, and ces. The aim of this research was isolation and rapid screening of emetic toxin producing Bacillus cereus strains in foodstuffs based on groEL, ces, and cer genes, using an improved polymerase chain reaction assay.
Methods: In this descriptive-cross sectional study, 10 samples of homemade and restaurant cooked rice was collected. Then cultural and biochemical characterestics and antibiotic resistance pattern of Bacillus cereus isolates were studied by disc diffusion(Kirb- bauer) method. In molecular survey, the DNA of Bacillus cereus was extracted and the presence of emetic toxin causing genes were studied by PCR method.
Results: Of all the cooked rice samples that were examined, isolates of Bacillus cereus was obtained and emetic toxin producing genes (groEL, ces, and cer) in isolates were proven. Of ten isolates, there were 4, 2, and 4 positive samples relative to the genes of groEL, ces, and cer, respectively, in isolated Bacillus cereus strains. Results revealed that the samples have emetic toxin producing genes (groEL, ces, and cer) but the frequency of genes in isolates were not the same.
Conclusion: Use of PCR method for rapid screening of emetic toxin producing Bacillus cereus strains in Foodstuffs is a convenient method until to ensure the health of consumable food. Increasing information about the causes of food poisoning can reduce the incidence of this complication.
The results of this study can be useful in obtaining information about the heaith of foods specially cooked rice, as well as the basis for further studies, including the pathogenesis mechanisms of Bacillus cereus.