ABSTRACT
PREVALENCE OF BACILLUS CEREUS CONTAMINATION IN RICE
IN KLANG VALLEY BY MOLECULAR DETECTION
AND IDENTIFICATION
Nareshwaran A/L Gnanasegaran
Bacillus cereus has been the topic of discussion when it comes to food poisoning since decades ago. However, this pathogen is very interesting to study due to its capability in forming spores thus protecting it from harsh and extreme environments. In addition, the ability of this microorganism to produce toxin, especially enterotoxins, has made the pathogenicity of B. cereus to shoot up as well. Generally, the more toxins they carry, the more severe its pathogenicity is. Therefore, the objective of this research was to determine the prevalence of B. cereus contamination, the toxins gene they carry and their antibiotic resistance patterns, in collected samples of raw and cooked rice. The Most Probable Number (MPN) method was conducted on all isolates to quantify the amount of microorganisms in undiluted samples before checking the type of emetic toxin or enterotoxin genes they carry. For this purpose, nine toxin genes, namely HBlC , HD , HBlA , 2NheA , 2NHeB , NheC , CytK , EntFM , and EM1 were screened from all the isolates. Kirby-Bauer assay was also performed using ten selected antimicrobial agents to compare the antibiotic resistance pattern of isolates. In this study, the prevalence of B. cereus from raw rice and cooked rice were found to be 65% and 54%, respectively. The most common toxin gene found in cooked rice was NheC gene while in raw rice, 2NheB . The Multiple
Antibiotic Resistance (MAR) index for both cooked and raw rice were 0.685 and 0.879,

respectively. The isolates obtained from raw rice were found to be more resistant to the antimicrobial agents as compared to isolates from cooked rice.
T he prevalence of B. cereus in cooked rice was significantly lower as compared to that of raw rice. It was suggested that crosscontamination from soil as the main source of infection. Thus, it is recommended that washing the rice seeds a couple more times than usual would decrease the incidence of B. cereus contamination.