Antibiotic resistance of an endodotitis-associated bacterium, Porphyromonas endodontalis.

牙髓卟啉单胞菌是一种革兰氏阴性、黑色素、厌氧菌，被认为与牙髓炎有关。从临床分离的牙髓病变分离株KSEW01中分离到一株非色素变异体KSEW01，它可能是KSEW01的亲本菌株。KSEW01对糖肽类抗生素试剂或糖肽类抗生素试剂万古霉素耐药，其最小抑菌浓度大于200ug/ml。为了进一步了解厌氧菌耐药的机制，用双向聚丙烯酰胺凝胶电泳法比较了KSEW01在有或无万古霉素存在下培养的细胞蛋白，以检测可能使该菌株产生耐药性的成分(S)。在加入VCM的细胞中有一个清晰的斑点，而在没有VCM的细胞中则没有。遗憾的是，结果是不可重现的。在此基础上，从KSE105菌株中获得了34株VCM抗性突变体，其中5株来自牙髓假单胞菌模式菌株ATCC35406。用琼脂稀释法测定突变株的最低抑菌浓度。获得的突变体均为黑色素。部分突变体对VCM的抗性达到与KSEW01相同的程度(MIC为200mug/ml)。KSEW01的三个黑色素自发回复菌株均被分离到，它们对VCM也具有抗性(MIC为100µg/ml)。从这些结果来看，色素沉着和VCM抵抗并没有联系在一起。KSE105的细胞成分与耐VCM突变株的细胞成分之间的差异正在调查中。这一结果将应用于成人牙周炎的一种强有力的病原体--牙龈卟啉单胞菌。

Porphyromonas endodontalis, a Gram-negative, black-pigmented, anaerobic rod, is considered to be associated with endodontitis. A nonpigmentd variant, KSEW01, from KSE105 which is a clinical isolate from an endodontic lesion and is possibly a parent strain of KSEW01, was found to be resistant against a glycopeptide antibiotic reagent, or a dalbaheptide, vancomycin (VCM), of which the minimal inhibitory concentration (MIC) was greater than 200 mug/ml. To help understand the mechanism of the antibiotic resistance in anaerobes, the cellular proteins of KSEW01 which was cultured in the presence of and those in the absence of vancomycin were compared by the two dimensonal polyacrylamide gel electrophoresis to detect the component(s) that might give the antibiotic resistance to this strain. A clear spot which was present in the cell cultured with VCM and absent without VCM was found. Regretfully the result was not reproducible. Then, thirty-four VCM-resistant mutants from KSE105, five from P.endodontalis type strain, ATCC35406, were obtained in vitro. MICs of these mutants were measured by agar dilution method. The mutants obtained were all black-pigmented. Some of the mutants had the resistance against VCM to the same degree (MIC, 200 mug/ml) as that of KSEW01. All the three black-pigmented, spontaneous revertants of KSEW01 were isolated and they were also resistant against VCM (MIC, 100 mug/ml). From these results, pigmentation and VCM resistance were not linked together. The detection of the difference between the cellar components of KSE105 and those of the VCM-resistant mutants are under investigation. The results will be applied to a potent pathogen of adult periodontitis, Porphyromonas gingivalis.