Factors of detection of Bacillus cereus strains in eye cream.

Bacillus cereus has been associated with clinical infections and is also the cause of post-traumatic endophthalmitis as well as endogenous eye infections, which can result in blindness. Cosmetics, although preserved, can be contaminated during manufacture or use and thus cause serious health issues.

OBJECTIVE: We investigated the detection factors of Bacillus in eye cream preserved with parabens, including the non-ionic surfactants used as neutralizers such as Tween 80, a blend of Tween 60 and Span 80, Tween 20 and selective media.

METHODS: Eye-cream samples were first mixed with neutralizers and individually inoculated with B. cereus strains, B. mycoides, B. subtilis or B. thuringiensis at a final concentration of 5 log CFU per g. The inoculated samples with and without neutralizers were analysed after 30 min and during 84-day storage at room temperature. Presumptive colonies of Bacillus were enumerated on the varieties of Bacillus agar by spiral-plating techniques and most probable number (MPN) method.

RESULTS: The recovery counts of all Bacillus strains were between 4.10 and 4.58 log CFU per g in samples with Tween 80 and from 3.62 to 4.53 CFU per g in samples with TS after 30 min. Tween 20 was the least effective neutralizer. The challenged organisms, in samples without neutralizer, B. subtilis ATCC 15563 and B. cereus 4227A were detected at 1.83 and 1.49 log CFU per g after 30 min, respectively.

CONCLUSION: This study showed that Tween 80 was the best neutralizer for reducing the antimicrobial effect of parabens. BACARA® and R&F plating media showed typical reaction of Bacillus cereus strains.