For residents of long-term care facilities (LTCFs), antimicrobial-resistant bacteria (ARB) are a risk factor, yet their oral colonisation, potentially leading to aspiration pneumonia, remains unclear. This study was undertaken to survey the prevalence, phenotypic characteristics, and molecular epidemiology of antimicrobial-resistant Gram-negative bacteria in the oral cavity of LTCF residents, and to analyse the risk factors for such carriers. This study involved 98 residents of a LTCF in Hiroshima City, Japan, aged between 55 and 101 years. Oropharyngeal swabs were collected and plated on screening media for ESBL-producing and carbapenem-resistant bacteria; isolates were identified and tested for antibiotic susceptibility; biofilm formation was tested in vitro; identification of epidemic clones were pre-determined by PCR; resistance genes, sequence types, and whole-genome comparison of strains were conducted using draft genome sequences. Demographic data and clinical characterisations were collected and risk factors analysed. Fifty-four strains from 38% of the residents grew on screening media and comprised predominantly of Acinetobacter spp. (35%), Enterobacteriaceae spp. (22%), and Pseudomonas spp. (19%). All Escherichia coli isolates carried CTX-M-9 group and belonged to the phylogroup B2, O25:H4 ST131 fimH30 lineage. Six Acinetobacter baumannii isolates presented identical molecular characteristics and revealed more biofilm production than the others, strongly suggesting their clonal lineage. One Acinetobacter ursingii isolate displayed extensive resistance to various ß-lactams due to multiple acquired resistance genes. One Pseudomonas aeruginosa isolate showed exceptional resistance to all ß-lactams including carbapenems, aminoglycosides, and a new quinolone, showing a multidrug-resistant Pseudomonas aeruginosa (MDRP) phenotype and remarkable biofilm formation. Genome sequence analysis revealed this isolate was the blaIMP-1-positive clone ST235 in Japan. Strokes (cerebral infarction or cerebral haemorrhage) and percutaneous endoscopic gastrostomy tubes were recognised as risk factors for oral colonisation by ARB in the LTCF residents. ARB, as defined by growth on screening agar plates, which carried mobile resistance genes or elements or conferred high biofilm formation, were already prevalent in the oral cavity of LTCF residents. Health-care workers involved in oral care should be aware of antimicrobial resistance and pay special attention to transmission prevention and infection control measures to diminish ARB or mobile resistance elements dissemination in LTCFs.

中文翻译：

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在长期护理机构居民中，由耐药性革兰氏阴性细菌引起的口腔定植：患病率，危险因素和分子流行病学。

对于长期护理机构（LTCF）的居民，耐药菌（ARB）是一个危险因素，但是它们的口腔定植可能导致吸入性肺炎，目前尚不清楚。这项研究旨在调查LTCF居民口腔中抗药性革兰氏阴性细菌的患病率，表型特征和分子流行病学，并分析此类携带者的危险因素。这项研究涉及日本广岛市LTCF的98名居民，年龄在55至101岁之间。收集口咽拭子，并将其铺在用于产生ESBL和碳青霉烯抗性细菌的筛选培养基上。鉴定出分离物并测试其抗生素敏感性；在体外测试了生物膜的形成；流行病克隆的鉴定通过PCR预先确定；抗性基因 序列类型和菌株的全基因组比较使用草拟的基因组序列进行。收集人口统计学数据和临床特征并分析危险因素。来自38％居民的54种菌株在筛选培养基上生长，并且主要由不动杆菌属组成。（35％），肠杆菌科。（22％）和假单胞菌属。（19％）。所有分离的大肠杆菌均带有CTX-M-9基团，属于B2系，O25：H4 ST131 fimH30谱系。六个鲍曼不动杆菌分离株表现出相同的分子特征，并显示出比其他菌株更多的生物膜产生，强烈表明了它们的克隆谱系。由于多种获得性抗性基因，一种乌氏不动杆菌分离株显示出对各种ß-内酰胺的广泛抗性。铜绿假单胞菌的一种分离物对包括碳青霉烯类，氨基糖苷和新喹诺酮在内的所有ß-内酰胺类均表现出优异的抗性，显示出多药耐药性的铜绿假单胞菌（MDRP）表型和明显的生物膜形成。基因组序列分析表明，该分离株是日本的blaIMP-1阳性克隆ST235。在LTCF居民中，卒中（脑梗塞或脑出血）和经皮内窥镜胃造口术被认为是ARB口腔定植的危险因素。LTCF居民的口腔中已经普遍存在ARB（由筛选琼脂平板上的生长所定义的），这些琼脂带有可移动的抗性基因或元件或具有较高的生物膜形成能力。