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Title:	Detection and characterization of Bacillus cereus isolated from fried rice
Authors:	Nisreen Jawad Kadhim (P69741)
Supervisor:	Sahilah Abd Mutalib, Assoc. Prof. Dr.
Keywords:	Bacillus cereus Food poisoning Fried rice Food safety Dissertations, Academic -- Malaysia
Issue Date:	22-Jan-2016
Description:	Bacillus cereus can cause two types of food poisoning as emetic or diarrheal syndrome. Fried rice is recognized as one of potential risk food especially in tropical countries. This study was conducted to detect and characterize B. cereus isolated from fried rice. A total of 70 fried rice samples were purchased from restaurants at Bangi (20), Kajang (20) and UKM's (30) cafeteria from August 2013 to July 2014. The isolation of B. cereus was done onto Mannitol egg yolk polymyxin medium and the presence of B. cereus ranged from 1.2 × 104 to 1.6 × 106 cfu/g of fried rice samples. Of more than 110 colonies of presumptive B. cereus tested onto chromogenic B. cereus agar, 35 colonies were identified as B. cereus using biochemical and partial sequence of 16S rDNA sequences analysis. All B. cereus isolates named BC1 to BC35, were characterized for haemolytic enterotoxin (HBL) complex encoding genes (hblA, hblB, hblC and hblD), non-haemolytic enterotoxin encoding gene (NheA), enterotoxin/cytotoxin K (ctyK) gene and emetic toxin or cereulide (ces) peptide gene. Of 35 B. cereus isolates, 15 isolates were positive towards hblA gene, 4 isolates positive towards hblB, 6 isolates positive towards hblC, 12 isolates positive towards hblD and 12 isolates positive towards NheA. None of the B. cereus isolates were positive towards cytotoxin K (ctyK) and emetic toxin or cereulide (ces) peptide gene. Antibiotic resistance analysis showed the B. cereus isolates were highly resistant to streptomycin (88%, 31/35), ampicillin (88%, 31/35) and tetracyclin (86%, 30/35) followed by resistance towards vancomycin (63%, 22/35), gentamcin (57 %, 20/35), penicillin G (54 %, 19/35), nalidixic acid (51%, 18/35), nitrofurantoin (48%,17/35), kanamycin (45%, 16/35), erythromycin (42%, 15/35), ciprofloxacin (42%, 15/35), ceftriaxone (37%, 13/35) chloramphenicol (34%, 12/35) and bactriacin (31%, 11/35). Plasmid analysis showed two plasmid patterns (23 kb; 23 and 2.9 kb) among 35 B. cereus isolates. Antibiogram and plasmid patterns exhibited 35 and 2 patterns respectively. Plasmid pattern phenotypically less heterogenous when compared to antibiotic and RAPD -PCR analysis. Genetic fingerprinting of 35 B. cereus isolates was examined by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) using three different primers (RAPD1, RAPD2 and RAPD13). The results of the RAPD-PCR were analyzed using GelCompare software. RAPD-PCR with primer RAPD1 discriminated the B. cereus isolates into 5 clusters and 4 single isolates, RAPD2 primers into 3 clusters and 3 single isolates and RAPD13 primers into 5 clusters and 3 single isolates at 70% similarity level. Results of the presence study demonstrated the combination of phenotypically and genotypically methods show a wide heterogeneity among fried rice isolates of B. cereus. Hence, it is important to educate food handlers about their responsibilities for food safety and train them on personal hygiene policies and basic practices for safe food handlings.,Certification of Master's/Doctoral Thesis" is not available
Pages:	111
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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