朱娟　陈丽华　佘鹏飞　谭芮辰　王妍乐　伍勇

〔摘要〕 目的 研究表皮葡萄球菌icaA和icaR基因與生物被膜形成的相关性。方法 收集湘雅三医院机械通气患者分离表皮葡萄球菌26株，按生物被膜成膜能力分成生物被膜阳性菌组和生物被膜阴性菌组各13株。采用RT-PCR分别对2组细菌icaA和icaR基因灰度比进行检测；采用real-time PCR分别检测2组细菌icaA和icaR基因的表达，并通过2-△△Ct方法进行相对定量。结果 RT-PCR结果显示icaA基因在生物被膜阳性组中的灰度比为0.96～1.38，在生物被膜阴性组中为0.89～1.56，表达差异无统计学意义（T=10.65，P=0.057）；同理，icaR基因在生物被膜阳性组中的灰度比为0.79～1.24，在生物被膜阴性组中则为0.80～1.36，表达差异亦无统计学意义（T=14.62，P=0.479）。但icaA基因在生物被膜阳性组中的平均秩（16.35）明显高于生物被膜阴性菌组（10.65），而icaR基因生物被膜阳性组的平均秩（12.38）明显小于生物被膜阴性菌组（14.62）。real-time PCR检测发现表皮葡萄球菌生物被膜阳性组icaA基因的表达量（△CT=4.86）是生物被膜阴性组（△CT=13.57）的418.8倍（t=61.890，P<0.01），而icaR基因的表达量（△CT=19.03）仅为生物被膜阴性组（△CT=11.85）的1/145（t=21.330，P<0.01）。结论 icaA基因与表皮葡萄球菌生物被膜的形成呈正相关，而icaR基因与表皮葡萄球菌生物被膜的形成呈负相关。

〔关键词〕 表皮葡萄球菌；icaA；icaR；生物被膜

〔中图分类号〕R393；R378.1 〔文献标志码〕A 〔文章编号〕doi：10.3969/j.issn.1674-070X.2018.06.003

〔Abstract〕 Objective To study the correlations between icaA and icaR genes with biofilm formation of Staphylococcus epidermidis （S. epidermidis）. Methods 26 strains of S. epidermidis isolated from tracheal catheter of patients with mechanical ventilation in ICU of the Third Xiangya Hospital were collected and divided into biofilm positive group （13 strains） and biofilm negative group （13 strains） according to biofilm formation ability. The gray scale ratios of icaA and icaR genes in two groups were determined by reverse transcription PCR. The expressions of icaA and icaR genes in two groups were detected by real time PCR， the relative quantification was measured by using 2-ΔΔCt method. Results The RT-PCR showed that the gray scale ratios of icaA in positive group and negative group of biofilm-forming were 0.96～1.38 and 0.89～1.56， respectively， the difference was not statistically significant （T=10.65， P=0.057）. The gray scale ratios of icaR genes in positive group and negative group of biofilm-forming were 0.79～1.24 and 0.80～1.36， respectively， the expression between the two groups were not statistically significant （T=14.62， P=0.479）. The mean rank and sum of ranks of icaA gene in biofilm positive bacteria group （16.35） were significantly higher than those in biofilm negative group （10.65）， but the mean rank and sum of ranks of icaR gene in biofilm positive bacteria group （12.38） were significantly lower than those in biofilm negative bacteria group （14.62）. Real-time PCR showed that the expression of icaA gene in S. epidermidis in biofilm positive group （△CT=4.86） was 418.8 times of that in biofilm negative bacteria group （△CT=13.57） （t=61.890， P<0.01）， while the expression of icaR gene in biofilm positive group （△CT=19.03） was only 1/145 of that in negative group （△CT=11.85） （t=21.330， P<0.01）. Conclusion icaA gene is positively related to the formation of biofilm in S. epidermidis， while icaR gene is negatively related to the formation of biofilm in S. epidermidis.

〔Keywords〕 Staphylococcus epidermidis； icaA； icaR； biofilm

表皮葡萄球菌（staphylococcus epidermidis）是人体皮肤和黏膜正常菌群之一。近年来，随着各种体内置入设施，如气管插管、中心静脉置管和人工心脏瓣膜等的广泛使用，表皮葡萄球菌已成为医院内感染重要病原菌[1]。且随着抗生素的不合理使用，表皮葡萄球菌的耐药率有所增加[2]。此外，表皮葡萄球菌容易形成生物被膜，进而增强菌株耐药性并能使其逃避宿主免疫系统的监控，造成慢性、持续性和反复性感染特点[3]。研究发现表皮葡萄球菌生物被膜胞外基质的主要成分是胞间多糖粘附素（polysaccharide intercellular adhesion， PIA）[4]。……