Bertrand X, Muller A, Thouverez M, Talon D
Service d'hygiène hospitalière et d'épidémiologie moléculaire, CHU Jean-Minjoz, 25030 Besançon, France.
Pathol Biol (Paris). 2004 Oct;52(8):480-5. doi: 10.1016/j.patbio.2004.03.016.
The objective of our study was to investigate the relationship between molecular epidemiology and antibiotic susceptibility of MRSA during a four-year period. In this aim, we determined the antibiotype of all MRSA identified during a yearly period of 3 months and typed 50 consecutive non-replicate MRSA isolates of each year. We also recorded antibiotic use. Susceptibility rates to gentamicin, tobramycin and ofloxacin remained stable, respectively, 95, 16 and 4%. In contrast, the proportion of MRSA susceptible to erythromycin progressively increased from 7.0% to 32.5% (P < 0.001). PFGE analysis of genomic DNA from the 200 isolates revealed 15 different clones. We identified two epidemic clones, which contained 150 (clone A) and 28 isolates (clone C), respectively. The proportion of isolates belonging to clone A decreased during the study from 86% to 66%. Conversely, clone C increased from 4% to 22%. The increase of erythromycin-susceptibility within MRSA was caused by the emergence of clone C. Non-epidemic strains were more frequently susceptible to ofloxacin (31.8% vs. 1.1%) and tobramycin (45.4% vs. 16.8%) than epidemic strains. Antimicrobial use had not significantly varied during the study. The proportion of beta-lactams, fluoroquinolones, macrolides and aminosides was 71.8, 13.9, 5.0 and 3.8% of the total antibiotic use, respectively. In our hospital, MRSA isolates became more susceptible to antimicrobial of minor use. The selection pressure exerted by beta-lactams and fluoroquinolones was in favor of the spread of strains resistant to these both major antibiotic classes.
我们研究的目的是调查四年期间耐甲氧西林金黄色葡萄球菌（MRSA）的分子流行病学与抗生素敏感性之间的关系。为此，我们确定了在每年为期3个月的时间段内鉴定出的所有MRSA的抗菌型，并对每年连续50株非重复的MRSA分离株进行分型。我们还记录了抗生素的使用情况。对庆大霉素、妥布霉素和氧氟沙星的敏感率分别保持稳定，为95%、16%和4%。相比之下，对红霉素敏感的MRSA比例从7.0%逐渐增加到32.5%（P < 0.001）。对200株分离株的基因组DNA进行脉冲场凝胶电泳（PFGE）分析，发现了15种不同的克隆。我们鉴定出两个流行克隆，分别包含150株（克隆A）和28株（克隆C）。在研究期间，属于克隆A的分离株比例从86%降至66%。相反，克隆C从4%增加到22%。MRSA中红霉素敏感性的增加是由克隆C的出现引起的。非流行菌株比流行菌株对氧氟沙星（31.8%对1.1%）和妥布霉素（45.4%对16.8%）更敏感。在研究期间，抗菌药物的使用没有显著变化。β-内酰胺类、氟喹诺酮类、大环内酯类和氨基糖苷类在总抗生素使用量中的比例分别为71.8%、13.9%、5.0%和3.8%。在我们医院，MRSA分离株对使用较少的抗菌药物变得更敏感。β-内酰胺类和氟喹诺酮类施加的选择压力有利于对这两种主要抗生素类耐药的菌株传播。
