The oral microbial community is widely regarded as a latent reservoir of antibiotic resistance genes. This study assessed the molecular epidemiology, susceptibility profile, and resistance mechanisms of 35 methicillin-resistant Staphylococcus epidermidis (MRSE) strains isolated from the dental plaque of a healthy human population. Broth microdilution minimum inhibitory concentrations (MICs) revealed that all the isolates were nonsusceptible to oxacillin and penicillin G. Most of them were also resistant to trimethoprim (65.7%) and erythromycin (54.3%). The resistance to multiple antibiotics was found to be largely due to the acquisition of plasmid-borne genes. The mecA and dfrA genes were found in all the isolates, mostly dfrG (80%), aacA-aphD (20%), aadD (28.6%), aphA3 (22.9%), msrA (5.7%), and the ermC gene (14.3%). Classical mutational mechanisms found in these isolates were mainly efflux pumps such as qacA (31.4%), qacC (25.7%), tetK (17.1%), and norA (8.6%). Multilocus sequence type analysis revealed that sequence type 59 (ST59) strains comprised 71.43% of the typed isolates, and the eBURST algorithm clustered STs into the clonal complex 2-II(CC2-II). The staphyloccoccal cassette chromosome mec (SCCmec) type results showed that 25 (71.43%) were assigned to type IV. Moreover, 88.66% of the isolates were found to harbor six or more biofilm-associated genes. The aap, atlE, embp, sdrF, and IS256 genes were detected in all 35 isolates. This research demonstrates that biofilm-positive multiple-antibiotic-resistant ST59-SCCmec IV S. epidermidis strains exist in the dental plaque of healthy people and may be a potential risk for the transmission of antibiotic resistance.

中文翻译：

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从牙菌斑中分离出的耐甲氧西林的表皮葡萄球菌的特征。

口腔微生物群落被广泛认为是抗生素抗性基因的潜在库。这项研究评估了从健康人群的牙菌斑中分离出的35种耐甲氧西林表皮葡萄球菌（MRSE）菌株的分子流行病学，药敏谱和耐药机制。肉汤微量稀释最低抑菌浓度（MICs）显示，所有分离株对奥沙西林和青霉素G不敏感。它们中的大多数还对甲氧苄啶（65.7％）和红霉素（54.3％）耐药。发现对多种抗生素的抗性在很大程度上归因于质粒载体基因的获得。在所有分离物中都发现了mecA和dfrA基因，主要是dfrG（80％），aacA-aphD（20％），aadD（28.6％），aphA3（22.9％），msrA（5.7％）和ermC基因（ 14.3％）。在这些分离物中发现的经典突变机制主要是外排泵，例如qacA（31.4％），qacC（25.7％），tetK（17.1％）和norA（8.6％）。多基因座序列类型分析表明，序列类型59（ST59）菌株占类型分离株的71.43％，eBURST算法将ST聚类为克隆复合物2-II（CC2-II）。结果显示，葡萄球菌盒式染色体mec（SCCmec）类型为25，占71.43％。此外，发现88.86％的分离物具有六个或更多与生物膜相关的基因。在所有35个分离株中均检测到aap，atlE，emp，sdrF和IS256基因。这项研究表明生物膜阳性多重耐药ST59-SCCmec IVS。