Reduced Susceptibility to Antiseptics Is Conferred by Heterologous Housekeeping Genes

Abstract

Antimicrobial resistance is common in the microbial inhabitants of the human oral cavity. Antimicrobials are commonly encountered by oral microbes as they are present in our diet, both naturally and anthropogenically, and also used in oral healthcare products and amalgam fillings. We aimed to determine the presence of genes in the oral microbiome conferring reduced susceptibility to common antimicrobials. From an Escherichia coli library, 12,277 clones were screened and ten clones with reduced susceptibility to triclosan were identified. The genes responsible for this phenotype were identified as fabI, originating from a variety of different bacteria. The gene fabI encodes an enoyl-acyl carrier protein reductase (ENR), which is essential for fatty acid synthesis in bacteria. Triclosan binds to ENR, preventing fatty acid synthesis. By introducing the inserts containing fabI, ENR is likely overexpressed in E. coli, reducing the inhibitory effect of triclosan. Another clone was found to have reduced susceptibility to cetyltrimethylammonium bromide and cetylpyridinium chloride. This phenotype was conferred by a UDP-glucose 4-epimerase gene, galE, homologous to one from Veillonella parvula. The product of galE is involved in lipopolysaccharide production. Analysis of the E. coli host cell surface showed that the charge was more positive in the presence of galE, which likely reduces the binding of these positively charged antiseptics to the bacteria. This is the first time galE has been shown to confer resistance against quaternary ammonium compounds and represents a novel, epimerase-based, global cell adaptation, which confers resistance to cationic antimicrobials.

Antimicrobial Resistance on Farms: A Review Including Biosecurity and the Potential Role of Disinfectants in Resistance Selection

“…They disrupt the structure and function of bacterial membranes, and their popularity reflects their versatility and safety profile. However, it is known that use of a QAC can select for QAC-resistant bacteria, mediated by efflux pumps (plasmid-encoded or upregulated in response to exposure) and/or membrane changes, in addition to promoting biofilm formation (Buffet-Bataillon et al, 2012;Buffet-Bataillon, Tattevin, Maillard, Bonnaure-Mallet, & Jolivet-Gougeon, 2016;Tansirichaiya et al, 2017;Wales & Davies, 2015). Furthermore, allied reductions in antimicrobial sensitivity have been observed.…”

Detection of a Novel, and Likely Ancestral, Tn916-Like Element from a Human Saliva Metagenomic Library

“…The UCL Research Ethics Committee granted ethical approval to collect human saliva from volunteers (Project ID Number 5017/001) and all participants gave written consent before participating. The human saliva metagenomic library was created using the pCC1BAC vector and the tetracycline sensitive (minimum inhibitory concentration of 2 µg/mL) strain TransforMax EPI300 Electrocompetent E. coli as previously described [24,25].…”

“…As estimates indicate that only two-thirds of the bacteria from this environment have been cultured we created and functionally screened, a human saliva metagenomic library to identify antibiotic resistance genes and associated mobile genetic elements [23]. We have previously reported on the novel efflux genes tetAB(60) encoding resistance to tetracycline and tigecycline in Escherichia coli and multiple genes encoding resistance to biocides from this metagenomic library [24,25].…”

Functional screening of a human saliva metagenomic DNA reveal novel resistance genes against sodium hypochlorite and chlorhexidine

“…Antimicrobial agents have saved uncountable numbers of lives for decades since the discovery of Penicillin; however, with a worldwide increase of antimicrobial resistance, infectious diseases currently have become more challenging to be treated. All uses of antimicrobials apply selective pressure to bacteria to evolve and develop antimicrobial resistance [1][2][3][4]. Discovery of resistance genes recovered from ancient samples showed that they were significantly similar to the modern resistance variants, suggesting antimicrobial resistance as an old natural phenomenon [5][6][7], but have recently become a problem possibly due to the selective pressures that accelerated the spreading of resistance genes through horizontal gene transfer [8][9][10].…”

“…Relevant examples of antimicrobials used in dental practices and dental hygiene products are chlorhexidine used in antimicrobial mouth rinses post-operative of surgical procedures [20], and for gingivitis and periodontitis patients who are unable to maintain adequate mechanical hygiene [21], sodium hypochlorite used as an irrigation agent during root canal treatment [22], sodium benzoate used in various toothpastes, cetyltrimethylammonium bromide (CTAB) found in throat lozenges and topical gels and conventional antibiotics for patients with risk factors pre-operative of surgical procedures. Studies have shown that the oral microbiome contains resistance genes against various antimicrobials agents such as β-lactams, tetracycline, tigecycline, amoxicillin, gentamicin, CTAB, erythromycin and cetylpyridinium chloride [1,[23][24][25][26][27][28].…”