IMMUNOASSAY AND POLYMERASE CHAIN REACTION TECHNIQUES FOR DETECTION OF ENTEROTOXIGENIC BACILLUS CEREUS

Abstract

Objectives: To compare the Reverse Passive Latex Agglutination (RPLA) and Enzyme Linked Immunosorbent Assay (ELISA) techniques with a Polymerase Chain Reaction (PCR) for detection of enterotoxigenic Bacillus cereus.
Design: A cross-sectional study.
Setting: The Department of Public Health, Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Nairobi.

Subjects: Forty seven Bacillus cereus strains previously isolated from foods.

Main outcome measures: Detection of hemolysin BL, non-hemolytic enterotoxin, binding protein gene (hblA) of the hemolysin BL, and binding protein gene (nheA) of nonhemolytic enterotoxin.

Results: Twenty five (53.2%) of the isolates produced hemolysin BL, while 81% of them produced non-hemolytic enterotoxin. Thirty eight (38.3%) produced both hemolysin BL and non-hemolytic enterotoxin. A polymerase chain reaction amplification assay detected the presence of hblA gene in all hemolysin BL positive isolates and nheA gene in 91.5% of non-hemolytic enterotoxin positive isolates. There was a strong association between PCRtest and RPLA test (Pearson's X2 = 12.65; p< 0.001) as well as between PCR test and visual immunoassay test(Pearson's chi-square X2 =18.46: p< 0.01).
Conclusion: Polymerase chain reaction amplification assay technique for detection of enterotoxigenicity of B. cereus compare well with the immunoassay tests. The technique is sensitive detecting even strains with silent genes, and is rapid with the test complete within 24 hours.