Journal
JOURNAL OF COSMETIC DERMATOLOGY
Volume 18, Issue 2, Pages 652-658Publisher
WILEY
DOI: 10.1111/jocd.12822
Keywords
cosmetic preservatives; microbial isolation; microbiology; minimum inhibitory concentration; safety testing
Categories
Funding
- Promotional Project for Postgraduate Research Capabilities
- National Natural Science Foundation of China [31401390]
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Background/AimsHealthy skin harbors numerous microbes known to maintain its health and prevent attacks from external pathogens. The influence of chemical preservatives commonly used in cosmetic products on facial resident flora remains poorly characterized. In this study, we aimed to investigate the antibacterial activity of five such preservatives on in vitro cultivated skin-resident bacteria. MethodsBoth Gram-positive and Gram-negative bacteria were isolated on blood agar, tryptic soy agar, and nutrient agar; Gram-negative bacteria were then selected on Hank's balanced salt solution containing antibiotics and Reasoner's 2A. The minimum inhibitory concentrations (MICs) of methylisothiazolinone (MTI), iodopropynyl butylcarbamate (IPBC), ethylhexylglycerin (EHG), methylparaben (MP), and phenoxyethanol (PE) were estimated for nine facial resident bacteria, Escherichia coli, and Staphylococcus aureus using serial broth dilution in vitro. ResultsThe maximum test concentrations coincided with the upper limits set by the Cosmetic Safety and Technical Specification (2015 edition, China). Nine facial resident bacteria were isolated from 14 healthy adults: Staphylococcus epidermidis, Staphylococcus capitis, Kocuria, Micrococcus luteus, Bacillus, Acinetobacter, Pseudomonas parafulva, Pseudomonas oleovorans, and Roseomonas cervicalis. MTI and IPBC displayed the strongest effect on all tested strains (MICs 0.01%), followed by EHG and MP (MICs 0.3%), and finally PE with the weakest effect (MIC 1%). ConclusionThe five chemical preservatives assayed inhibited survival of the nine facial resident bacteria isolates, when tested at the maximum allowed limit. The corresponding MICs will provide a reference for the effective utilization of these compounds in product formulations.
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