Cosmetic preservative exposure promotes persistent and antibiotic resistance of staphylococci by chromosome mutations.

OBJECTIVES: Antibiotic-resistant staphylococci are common skin colonisers and an important public-health concern. The role of cosmetic preservatives in selecting resistance is unclear. We examined whether exposure to widely used preservatives promotes antibiotic resistance in Staphylococcus spp. and explored underlying mechanisms. METHODS: Methicillin-resistant and susceptible S. aureus (MRSA and MSSA) and S. epidermidis (MRSE and MSSE) were exposed to dimethylol dimethyl hydantoin (DMDMH, 15-100 µg/ml), Diazolidinyl Urea (IU, 10-300 µg/ml), Sodium methyl p-hydroxybenzoate (MP, 50-3000 µg/ml), respectively, and nutrient agar plates supplemented with 1 ×MIC of chloramphenicol, kanamycin, oxacillin or tetracycline were used to isolate mutants. Minimum inhibitory concentrations and time-killing curves of mutants were determined. Genome sequencing was applied to MSSA and MRSE, and transcriptome sequencing was applied to MSSA to clarify the mutation sites and their role in promoting antibiotic resistance of MSSA. RESULTS: Exposure to DMDMH, IU, and MP led to a 150- to 11100-fold increase in antibiotic resistance mutation frequency over the control. The mutants had 2- to 256-fold higher MICs than the wild type for chloramphenicol, cefuroxime, levofloxacin, linezolid, tetracycline, erythromycin, and kanamycin. Moreover, for MSSA, clfAD862S909del, spoVGSer94Leu(spoVGS94L) and rplDK68 were determined, and rpoBMet500Arg (rpoBM500R) were identified in MRSE. The MSSA genome mutation was triggered by downregulating the repressor LexA and upregulating the activator RecA of SOS system. MSSA clfAD862S909del/spoVGS94L mutants increased antibiotic tolerance by synthesising biofilm via inhibiting the quorum-sensing system. The antibiotic resistance of S. aureus was due to the rplDK68 mutation. CONCLUSIONS: Cosmetic preservative exposure significantly increased the frequency of antibiotic resistance mutations in vitro, and mutants showed increased resistance to multiple antibiotics. Cosmetic preservatives exposure that induced clfAD862S909del and spoVGS94L mutations, which increase the antibiotic tolerance of S. aureus by enhancing biofilm-forming ability. and providing a viable reservoir from which antibiotic-resistant mutants can emerge through rplDK68 mutations.