Enterobacter gergoviae membrane modifications are involved in the adaptive response to preservatives used in cosmetic industry

AIM: The objective of this study was to understand the adaptive mechanisms in Enterobacter gergoviae which are involved in recurrent contaminations in cosmetic products that are incorporated with preservatives. METHODS AND RESULTS: Bacterial strains from two backgrounds were examined for a profound understanding of the mechanisms of adaptation against preservatives. It included a series of Ent. gergoviae strain—ATCC 33028 derivatives, isolated using increasing methylisothiazolinone–chloromethylisothiazolinone (MIT‐CMIT) and triclosan concentrations. The other series was of Ent. gergoviae isolates from cosmetic products exhibiting MIT‐CMIT and triclosan resistance. We evaluated the outer membrane protein modifications and efflux mechanisms activities responsible for the resistant trait via immunoblotting assays. Additionally, for understanding the efflux activity real‐time efflux, experiments were performed. A cross‐insusceptibility between preservatives and some disinfectants was observed in MIT‐CMIT‐resistant derivative isolates, but antibiotics susceptibility was not altered. Resistance to EDTA was significant in all preservatives insusceptible derivative strains, indicating modifications in the LPS layer. Furthermore, an array of real‐time efflux assays indicated different activity levels while no variations were detected in porins and AcrAB‐TolC pumps production. Overexpression of a specific flagellin‐type protein was observed in one of the MIT‐CMIT‐ and triclosan‐resistant strains. Another candidate, a 25‐kDa peroxiredoxin enzyme involved in oxidative detoxification, was identified to be overexpressed in MIT‐CMIT derivative. A similar profile was also observed among strains isolated from cosmetic products. CONCLUSIONS: Our study highlights the existence of adaptive mechanisms such as overexpression of detoxifying enzymes, flagellin, modification of membrane structure/function in Ent. gergoviae. They might be involved in recurrent episodes of contaminations occurring in the cosmetic production lines. SIGNIFICANCE AND IMPACT OF THE STUDY: No cross‐resistance could be observed with antibiotics when MICs to preservatives were increased; however, a decrease in the disinfectants bactericidal effects was confirmed in preservative‐tolerant strains. This will impact industry disinfection strategies treatment against bacteria.