摘要：
Objective To study the relationship between genetic typing and the antibiotic susceptibility of staphylococcus aureus (SA) isolated from keratitis or conjunctivitis patients.Methods Experimental study.Thirty-four (34) strains of Staphylococcus aureus were isolated from 34 cases of keratitis or conjunctivitis.The genomic DNA was extracted and amplified with PCR.With the method of multi locus sequences typing (MLST),gene fragments from 7 house-keeping genes were amplified and the products were sequenced.The results were submitted to the MLST website (www.pubmlst.org).In comparison with the allele of the corresponding gene,the allele spectrums of the strain were obtained with 7 housekeeping genes.At last,the MLST genotypes of the isolated strains were determined.With the START software,the evolutionary tree was established with UPGMA method.With the microdilution method,the MIC90 of 13 antimicrobial agents was determined.The MIC90 value of antimicrobial agents among different genotypes of Staphylococcus aureus was comparatively analyzed.Results Ten (10) genotypes were obtained from 34 strains of Staphylococcus aureus.The dominant types were ST239,ST2592 and ST188.The clustering of genotyping was relatively concentrated,mainly in group Ⅰ (25 strains of SA,83.3％ of the total),and followed by group Ⅱ (5 strains of SA,16.7％).The conjunctival isolates were distributed in the subgroup A of group Ⅰ.The cornea isolates were concentrated in subgroup B and group Ⅱ.With the exact probability method,the R × C chi square tests were used as statistic analysis method.The difference between the bacterial genotyping of two sources was statistically significant (P=0.011).Twenty-four strains of SA in group Ⅰ was sensitive to Vancomycin,Rifampicin and Amikacin (sensitivity ratio was 24/24,20/24 and 20/24,respectively),and was generally resistant to other antibiotics.The values of MIC90 of ciprofloxacin,ofloxacin,gatifloxacin and moxifloxacin to Staphylococcus aureus in subgroup A (0.16±0.07,0.51±0.42,0.31 ±0.14,0.22±0.33) were significantly lower than the values in subgroup B(0.74±0.11,0.84±0.45,0.67±0.03,0.68± 0.26).The difference was statistically significant (P=0.004,0.026,0.034,0.001).There was no significant difference between the MIC90 values of the other 9 kinds of antibiotics in the subgroup A and in the subgroup B of Staphylococcus aureus (P value 0.047-0.561).Conclusion The genotype of Staphylococcus aureus of corneal isolations and conjunctival isolations were different.The conjunctival isolates were distributed in the subgroup A of group Ⅰ and the corneal isolates were concentrated in subgroup B and group Ⅱ.There is a significant correlation between the MLST genotypes and antibiotic sensitivity.%目的 了解来源于角膜、结膜的金黄色葡萄球菌的基因型及其与体外药物敏感性间的相互关系.方法 实验研究.由金黄色葡萄球菌性角膜、结膜炎患者病灶处分离培养出的34株金黄色葡萄球菌,提取菌株的DNA,应用多位点序列分型(MLST)的方法,扩增7个金黄色葡萄球菌看家基因片段的DNA序列,其产物测序后,提交MLST网站与相应基因的等位基因进行比较,获得该菌株针对7个看家基因的等位基因谱,最后确定分离株的MLST基因型别,应用START软件,采用非加权组平均法(UPGMA)建立进化树.同时应用微量稀释法测定13种抗菌药物的90％最低抑菌浓度(MIC90),对比分析金黄色葡萄球菌不同基因型与抗菌药物MIC90之间的关系.角、结膜分离菌的MLST基因分型比较采用R×C卡方检验;抗菌药物对不同亚群金黄色葡萄球菌的MIC90比较分析采用t检验.结果 34株金黄色葡萄球菌得到10个基因型,优势菌株基因型为ST239型,其次为ST2592型及ST188型.基因分型聚类相对集中,以Ⅰ类群为主(25株细菌,占总数的83.3％),5株细菌(16.7％)分布在Ⅱ类群中;结膜分离菌集中于Ⅰ类群的A子亚群中,角膜分离菌集中于B子亚群及Ⅱ类群中,两种来源的细菌基因分型差异有统计学意义(P=0.011).Ⅰ类群中24株金黄色葡萄球菌对万古霉素、利福平、阿米卡星较敏感(敏感菌株比例分别为24/24,20/24和20/24),对其他抗菌药物普遍耐药.子亚群A中金黄色葡萄球菌对环丙沙星、氧氟沙星、加替沙星、莫西沙星的MIC90值(0.16±0.07,0.51±0.42,0.31±0.14,0.22±0.33)明显低于子亚群B(0.74±0.11,0.84±0.45,0.67±0.03,0.68±0.26),差异有统计学意义(P=0.004,0.026,0.034,0.001);而子亚群A与子亚群B的金黄色葡萄球菌对其他9种抗菌药物的MIC90值比较差异无明显统计学意义(P值分布范围0.047～0.561).结论 来源于角膜和结膜的金黄色葡萄球菌基因型不同,结膜分离菌以Ⅰ类群的A子亚群为主,角膜分离菌以B子亚群及Ⅱ类群为主;MLST基因型与药物敏感性之间有明显相关关系.
