Molecular epiderniologic study on prevalence of penicillin-resistant enterococci in Japan

近年来肠球菌已成为医院感染的重要病原菌。本研究采用分子流行病学方法，对近年临床分离的肠球菌进行了耐药性研究，重点分析了其对青霉素、氨基糖苷类和四环素类抗生素的耐药性。研究对象为札幌医科大学医院1997 ~ 1998年和2001 ~ 2004年分离的748株临床肠球菌。青霉素耐药性在Efaecium和E.rafnosus中非常普遍，而在其他肠球菌中的频率较低。在40.5%的粪肠球菌和3.5%的粪肠球菌中检测到高水平的庆大霉素耐药基因aac（6 '）-aph（2''）。ant（9）Ia是一种仅在金黄色葡萄球菌中报道的壮观霉素抗性基因，在Efaecalis、Efaecium和Eavium各一株中检测到。四环素耐药基因tetM在粪霉属（75.2%）和屎霉属（71.7%）中高度流行。在5株粪肠球菌中检测到仅在化脓性链球菌中报道的tetT，其序列除4个核苷酸（4个氨基酸）外与化脓性链球菌完全相同。tetS和tetO也存在于一些菌株中。tetS的核苷酸序列与单核细胞增生李斯特菌完全相同，而tetO存在一定的遗传变异。这些结果表明，一些新的耐药基因已经在肠球菌中普遍存在，提示需要对肠球菌的耐药性进行持续监测。

Enterococcus has been become an important pathogen of nosocomial infections recently. In this research project, we studied prevalence of drug resistance of recent clinical isolates of enterococci by using molecular epiderniologic methods, focusing on resistance to penicillin, aminoglycoside, and tetracycline. Study subject was 748 clinical strains of enterococci isolated from 1997 to 1998, and from 2001 to 2004 in Sapporo Medical University Hospital. Penicillin resistance was highly prevalent in Efaecium and E.rafnosus in contrast to low frequencies in other enterococcal species. A high-level gentamicin resistance gene aac(6')-aph(2'') was detected in 40.5% of Efaecalis and 3.5% of Efaecium. The ant(9)Ia, a spectinomycin resistance gene which had been reported only in Staphylococcus aureus was detected in one strain each of Efaecalis, Efaecium, and Eavium. A tetracycline resistance gene tetM was highly prevalent in Efaecalis (75.2%) and Efaecium (71.7%). The tetT which had been reported only in S.pyogenes was detected in 5 strains of Efaecalis and its sequence was identical to that of S.pyogenes except for 4 nucleotides (4 amino acids). The tetS and tetO were also found in some strains. Nucleotide sequence of tetS was identical to that of Listeria monocytogenes, while some genetic variations were found in tetO. These results indicated that some novel resistance genes have been prevalent in enterococci, suggesting a need for continuous surveillance of drug resistance in enterococci.