Development of antiseptic adaptation and cross-adapatation in selected oral pathogens in vitro

Abstract

There is evidence that pathogenic bacteria can adapt to antiseptics upon repeated exposure. More alarming is the concomitant increase in antibiotic resistance that has been described for some pathogens. Unfortunately, effects of adaptation and cross-adaptation are hardly known for oral pathogens, which are very frequently exposed to antiseptics. Therefore, this study aimed to determine the in vitro increase in minimum inhibitory concentrations (MICs) in oral pathogens after repeated exposure to chlorhexidine or cetylpyridinium chloride, to examine if (cross-)adaptation to antiseptics/antibiotics occurs, if (cross-)adaptation is reversible and what the potential underlying mechanisms are. When the pathogens were exposed to antiseptics, their MICs significantly increased. This increase was in general at least partially conserved after regrowth without antiseptics. Some of the adapted species also showed cross-adaptation, as shown by increased MICs of antibiotics and the other antiseptic. In most antiseptic-adapted bacteria, cell-surface hydrophobicity was increased and mass-spectrometry analysis revealed changes in expression of proteins involved in a wide range of functional domains. These in vitro data shows the adaptation and cross-adaptation of oral pathogens to antiseptics and antibiotics. This was related to changes in cell surface hydrophobicity and in expression of proteins involved in membrane transport, virulence, oxidative stress protection and metabolism.

Limited antimicrobial efficacy of oral care antiseptics in microcosm biofilms and phenotypic adaptation of bacteria upon repeated exposure

“…Kitagawa et al also examined protein expression profiles of their CHX-adapted E. faecalis strain and its WT strain by SDS-PAGE and found an additional 19-kDa band in the protein expression of the adapted strain [31], which had previously been found in vancomycin-resistant enterococci [66]. Verspecht et al analyzed the proteomes of their adapted and WT strains and found that antiseptic-adapted bacteria changed their metabolic profiles by upregulation of proteins involved in energy metabolism and in amino acid, nucleotide, and inorganic ion metabolisms [32], which has analogously been described for some S. aureus and Enterococcus spp. that were resistant to various clinically relevant antibiotics [67].…”

“…Likewise, Wang et al showed a fourfold MIC-increase in E. faecalis and twofold MIC-increases in F. nucleatum, Streptococcus gordonii, and Porphyromonas gingivalis toward CHX upon 10 suchlike passages [63]. Employing a similar methodology, Verspecht et al reported 1.3-to 5.5-fold MIC increases toward CHX and CPC in Aggregatibacter actinomycetemcomitans, F. nucleatum, P. gingivalis, Prevotella intermedia, S. mutans, and Streptococcus sobrinus, depending on the bacterial strain and the tested antiseptic [32]. However, these three studies evaluated phenotypic adaptation by exerting continuous selection pressure due to constant presence of the antiseptic [31,32,63].…”

“…that were resistant to various clinically relevant antibiotics [67]. Furthermore, increases in cell surface hydrophobicity were reported in antiseptic-adapted strains [31,32]. Due to membranedisrupting mechanism of action of CHX, CPC, and BAC, it seems reasonable that expression of efflux pumps or changes in the membrane composition may be potential resistance mechanisms against those agents [21].…”

“…Since the oral cavity may be considered potential reservoir of resistance genes, antimicrobial resistance may easily be spread among oral biofilm bacteria via horizontal gene transfer [28][29][30]. Interestingly, the potential risks associated with the widespread use of antiseptics in oral care have only been highlighted very recently [21,22,31,32].…”

Phenotypic and multi-omics characterization ofEscherichia coliK-12 adapted to quaternary ammonium compounds identifies lipid A and cell envelope alterations regulated by mar-sox-rob and stress inducible pathways

“…Transcriptomic (33) and proteomic (10,11,33,34) alterations of QAC adapted strains have been reported but no insights into potential genomic alterations are available.…”