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ST Kane, DC Cochran, D Stroman, C McLean, MC Callegan; Genotypic and Phenotypic Analysis of Putative Virulence Factors Associated With Bacillus Ocular Infection Isolates . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1598.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To analyze the genotypic and phenotypic profiles of Bacillus isolates from cases of endophthalmitis, blepharitis, and keratitis. Methods: Bacillus thuringiensis, Bacillus cereus, and Bacillus subtilis were isolated from clinical ocular infection cases and analyzed for the presence of putative virulence factors. PCR was used to identify genes for a number of virulence factors, including phosphatidylinositol-phospholipase C (PI-PLC), phosphatidylcholine-specific phospholipase C (PC-PLC), sphingomyelinase (SPH), hemolysin BL (HBL), and crystal toxin (CRY, B. thuringiensis specific). For phenotypic analyses, ocular isolates were cultured in vitro and tested for PI-PLC, PC-PLC, SPH, and protease activities, and motility. Results: Toxin genes were identified in most B. thuringiensis and B. cereus isolates, but not in B. subtilis isolates. Phenotypic analysis indicated that B. cereus strains produced higher in vitro concentrations of SPH and protease than did B. thuringiensis isolates. Protease activity was enriched among B. cereus keratitis isolates, while protease activity was enriched among B. cereus keratitis and blepharitis isolates. In vitro PC-PLC and PI-PLC production among B. cereus and B. thuringiensis isolates was similar, regardless of infection type. B. subtilis did not produce PI-PLC, PC-PLC or SPH. Agar surface motility of B. cereus was greater than that of B. thuringiensis. Agar surface motility among B. cereus endophthalmitis isolates was greater than that among isolates from other infection types. B. subtilis was not motile. Conclusions: B. cereus and B. thuringiensis isolates possessed similar genotypic profiles. B. subtilis lacked these toxin genes and therefore did not produce the toxins analyzed. The majority of B. cereus and B. thuringiensis isolates produced toxins in vitro, with some phenotypes prevailing among isolates from specific infection types. Whether these in vitro findings relate to variabilities in the pathogenesis of Bacillus endophthalmitis and ocular surface infections is presently under investigation.
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