Survival and detection of Bacillus cereus in the presence of Escherichia coli, Salmonella enteriditis, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans after rechallenge in makeup removers

Abstract

Objective

Pathogenic contamination of cosmetics intended to be applied on or around the eye area, including make-up removers, may lead to severe eye infections. To assess the efficacy of antimicrobial preservatives in these products we investigated the survival and detection of Bacillus cereus F 4227A spiked into make-up removers, alone and in the presence of other relevant microorganisms.

Methods

Four brands of make-up removers, A, B, C and D, were challenged three times (day 0, day 7, and day 14) using B. cereus, in pure and mixed cultures, at a final concentration of 5 log CFU/ml of Bacillus cereus or 6 log CFU/ml for other microorganisms. Inoculated samples were diluted and spiral-plated after 30 min and 24 hr of each challenge onto selective media for recovery of surviving microorganisms: BACARA (B. cereus), MacConkey (E. coli), ChromID (P. aeruginosa), XLT4 (S. enteritidis), Baird Parker agar (Staph aureus), and PDA+chlortetracycline HCL (C. albicans).

Results

The population of B. cereus spiked as a pure culture increased significantly from the first to the third challenge after 30 min exposure-time, going from 0.73 to 2.59 in A, from 0.80 to 2.69 in B, and from 0.80 to 1.67 log CFU/ml in C (P < 0.05). Likewise, the B. cereus population from the mixed cultures had a significantly higher survival count at the third challenge: from 0.12 log MPN/ml to 2.16 log CFU/ml in A, 0.57 to 2.27 log CFU/ml in B, and from undetected (LOD = 0.48 log MPN) to 0.98 log CFU/ml in C, respectively. After challenges, Staph aureus, C. albicans, and P. aeruginosa increased in B; Staph aureus and C. albicans in C; and E. coli and Staph aureus in D. The growth of other bacteria types were unaffected by the number of challenges, but B. cereus population was detected with the third challenge.

Conclusion

It is appropriate to assess the antimicrobial efficacy of preservatives using at least three challenges, especially for cosmetics that are subjected to repetitive contamination by users.

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