Abstract
ObjectiveMany sections of the health care system are facing a major challenge making infectious disease problematic to treat; antimicrobial resistance (AMR). Identification and surveillance of the resistome have been highlighted as one of the strategies to overcome the problem. This study aimed to screen for AMR genes in an oral microbiota, a complex microbial system continuously exposed to antimicrobial agents commonly used in dental practice.Materials and methodsAs a significant part of the oral microbiome cannot be conventionally cultured, a functional metagenomic approach was chosen. The human oral metagenomic DNA was extracted from saliva samples collected from 50 healthy volunteers in Norway. The oral metagenomic library was then constructed by ligating partially digested oral metagenome into pSMART BAC vector and introducing into Escherichia coli. The library was screened against antimicrobials in dental practices. All resistant clones were selected and analyzed.ResultsScreening of the oral metagenomic library against different antimicrobials detected multiple clones with resistance against chlorhexidine, triclosan, erythromycin, tetracycline, and sodium hypochlorite. Bioinformatic analysis revealed both already known resistance genes, including msr, mef(A), tetAB(46), and fabK, and genes that were not previously described to confer resistance, including recA and accB conferring resistance to sodium hypochlorite and chlorhexidine, respectively.ConclusionMultiple clones conferring resistance to antimicrobials commonly used in dental practices were detected, containing known and novel resistant genes by functional-based metagenomics. There is a need for more studies to increase our knowledge in the field.
Highlights
Antimicrobial agents have saved uncountable numbers of lives for decades since the discovery of Penicillin; with a worldwide increase of antimicrobial resistance, infectious diseases currently have become more challenging to be treated
Wigand et al BMC Oral Health (2021) 21:632 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
Summary
Antimicrobial agents have saved uncountable numbers of lives for decades since the discovery of Penicillin; with a worldwide increase of antimicrobial resistance, infectious diseases currently have become more challenging to be treated. The human oral cavity is a complex microbial system [14, 15], housing a selection of bacteria with more than 700 bacterial species [16,17,18] It consists of several small ecosystems with unique environments such as keratinized and non-keratinized mucosa, the tongue, saliva, tonsils, teeth, and subgingival pockets together making up the oral microbiome [16, 19]. The species in the oral microbiome vary, from facultative aerobes to strict anaerobes They are continuously exposed to antimicrobial agents from external products such as oral hygiene products as toothpaste, mouth rinse, agents used in dental treatment and food, and is likely to develop antimicrobial resistance. 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]
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