Subtyping of Bacillus cereus by Total Cell Protein Patterns and Arbitrary Primer Polymerase Chain Reaction

Bacillus cereus is a ubiquitous spore-forming Gram-positive rod that is associated with foodborne outbreaks as well as several opportunistic infections. Inspite of the prevalence of B. cereus associated foodborne outbreaks, subtyping of the species using molecular typing assays was not attempted. In this study we have recovered 58 B. cereus isolates from natural and clinical sources and initially characterized them, along with a B. cereus strain (ATCC 14579) and B. thuringiensis natural isolate, by biotyping, antibiotic susceptibility testing, and SDS-PAGE of total cell proteins. Our data have shown the existence of 1 biotype, 3 anti-biograms and 22 (38%) total cell protein patterns among the 58 B. cereus isolates. B. thuringiensis had a different protein pattern. SDS-PAGE of total cell proteins data denote clonal heterogeneity within B. cereus. Protein pattern 4 (pp4) was the most predominant with 13 isolates of B. cereus showing this pattern. Eight out of the 13 isolates with pp4 and one B. cereus strain (ATCC 14579) were further subtyped by using the arbitrary primer polymerase chain reaction (AP-PCR) assay. Eight (88.8%) different PCR patterns out of the 9 B. cereus isolates were obtained. Patterns obtained by SDS-PAGE of total cell proteins and AP-PCR were reproducible. These results indicate that SDS-PAGE of total cell proteins allows the differentiation among species within Bacillus and of strains within B. cereus. The typeability of the method was 100% and the simpson's discrimination index of diversity was 98%. The utility of SDS-PAGE of total cell proteins in a pilot epidemiologic study was assessed and results obtained demonstrate its typing potential. AP-PCR allows further subtyping of the species. Both methods if used in conjunction may be useful for further clinical and epidemiologic studies of the spectrum of diseases caused by B. cereus.