Abstract
Although eye area cosmetics contain preservatives, contamination can still occur during or after manufacture or through use. Understanding the likelihood of bacterial survival in eye creams begins with sensitive and accurate methods for the detection of bacterial contamination; therefore, we investigated optimal culture conditions, including neutralizers, dilution broths, and selective media for the detection of Bacillus in eye cream. Samples of three different brands of eye creams were first mixed with Tween 80, Tween 20, or a blend of Tween 60 and Span 80, then neutralized and non-neutralized samples were individually inoculated with B. cereus strains, B. mycoides, a mislabeled B. megaterium, B. subtilis or B. thuringiensis at a final concentration of 5 log CFU/g. The inoculated samples, with and without neutralizers, were spiral-plated and incubated at 30 °C for 24 h to 48 h. Presumptive colonies of Bacillus were enumerated on U. S. Food and Drug Administration Bacteriological Analytical Manual (FDA-BAM) referenced agars Bacillus cereus rapid agar (BACARA) and mannitol-egg yolk-polymixin agar (MYP). Our results show significant differences among the neutralizers, plates, and products. The combination of Tryptone- Azolectin-Tween and Tween 80 (TAT and T80) produced higher levels of Bacillus, estimated at 4.18 log CFU/g compared to growth on Modified letheen broth and Tween 80, which produced 3.97 log CFU/g (P < 0.05). Colony counts of B. cereus cells on MYP agar were significantly higher, than those on BACARA agar, showing an average of 4.25 log CFU/g versus 3.84 log CFU/g, respectively (P < 0.05). The growth of the strain mislabeled B. megaterium ATCC 6458 on B. cereus selective agars BACARA and MYP agar led us to further investigations. We identified bi-pyramidal crystals among colonies of the strain, and subsequent PCR identified the cry 1 gene, indicating that strain was actually B. thuringiensis subps. kurstaki.
Highlights
Eye area cosmetics contain preservatives, contamination can still occur during or after manufacture or through use
Spores are resistant to extreme environments and may have been unaffected by the product formulation, vegetative cells were preferred in this study: We explored the optimum culture conditions for the detection and isolation of B cereus F 4227A, B. cereus F 6006, B. cereus ATCC 14579, B. megaterium ATCC 6458, B. mycoides ATCC 6462, B. subtilis ATCC 15563, and B. thuringiensis ATCC
Growth of bacteria inoculated into Product B resulted in an estimated 2.48 log CFU/g, which was significantly greater (P < 0.05) than the cell growth found in Product D (1.55 log CFU/g) or Product C (0.02 log Most probable number (MPN)/g) (Figure 1)
Summary
Eye area cosmetics contain preservatives, contamination can still occur during or after manufacture or through use. The presence of antimicrobial preservatives in cosmetics makes it difficult to detect and isolate microorganisms. Understanding the effects of preservatives on the growth of target organisms. Cosmetics 2017, 4, 56 in enrichment media and on selective/differential plating agars is essential for the detection of pathogenic organisms in cosmetics. Microorganisms indigenous to the normal eye, significant isolates, and products isolates are recommended by the Personal Care Products Council for challenging eye cosmetics; these include Gram-positive spore former bacteria [3]. This research focusses on the detection and isolation of Bacillus spp. in eye area cosmetics. Bacillus species are Gram-positive rod-shaped bacteria that are widely found in the environment, such as soil, dust, water, and sediments
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