Eguchi Hiroshi, Kuwahara Tomomi, Miyamoto Tatsuro, Nakayama-Imaohji Haruyuki, Ichimura Minoru, Hayashi Tetsuya, Shiota Hiroshi
Department of Ophthalmology and Visual Neuroscience, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan.
J Clin Microbiol. 2008 Feb;46(2):527-32. doi: 10.1128/JCM.01741-07. Epub 2007 Dec 12.
The clinical importance of nondiphtherial Corynebacterium, a ubiquitous member of the normal human microflora of the skin and mucous membrane, for ocular surface infections has been recognized recently. We performed an antimicrobial susceptibility test with Etest strips for three fluoroquinolones (ciprofloxacin, norfloxacin, and levofloxacin) and a taxonomic analysis on 21 isolates of Corynebacterium from ophthalmic samples. Of these, 16 isolates were identified as C. macginleyi at the species level on the basis of 16S rRNA gene sequence comparisons. The remaining five isolates were determined to be C. mastitidis (four) or C. accolens (one). Eleven of the C. macginleyi isolates showed high levels of resistance to all of the fluoroquinolones tested, and one isolate was resistant to norfloxacin alone. An analysis of the amplified quinolone-resistance-determining regions of the gyrA genes revealed that a single amino acid substitution in position 83 of the gyrA product was sufficient to generate the norfloxacin resistance phenotype, and double mutations leading to amino acid changes in positions 83 and 87 were necessary for high-level resistance against the other fluoroquinolones. We conducted the first example of multilocus sequence typing (MLST) analysis on C. macginleyi. The MLST analysis grouped the majority of C. macginleyi isolates into a single lineage, and another molecular strain typing by random amplified polymorphic DNA fragment patterns supported the finding, indicating that a particular lineage of C. macginleyi is dominant on the human ocular surface. This type of population might be particularly adaptable to the milieu on the human ocular surface.
非白喉棒状杆菌是皮肤和黏膜正常人类微生物群中普遍存在的成员，其对眼表感染的临床重要性最近已得到认可。我们用Etest试纸条对三种氟喹诺酮类药物（环丙沙星、诺氟沙星和左氧氟沙星）进行了药敏试验，并对21株来自眼科样本的棒状杆菌进行了分类分析。其中，根据16S rRNA基因序列比较，16株分离株在种水平上被鉴定为麦氏棒状杆菌。其余5株分离株被确定为乳房棒状杆菌（4株）或簇拥棒状杆菌（1株）。11株麦氏棒状杆菌分离株对所有测试的氟喹诺酮类药物均表现出高水平耐药，1株分离株仅对诺氟沙星耐药。对gyrA基因扩增的喹诺酮耐药决定区的分析表明，gyrA产物第83位的单个氨基酸取代足以产生诺氟沙星耐药表型，而导致第83位和第87位氨基酸变化的双突变是对其他氟喹诺酮类药物产生高水平耐药所必需的。我们对麦氏棒状杆菌进行了首例多位点序列分型（MLST）分析。MLST分析将大多数麦氏棒状杆菌分离株归为一个单一谱系，通过随机扩增多态性DNA片段模式进行的另一种分子菌株分型支持了这一发现，表明麦氏棒状杆菌的一个特定谱系在人眼表占主导地位。这种类型的菌群可能特别适应人眼表的环境。
