新生儿血培养中凝固酶阴性葡萄球菌细胞间粘附基因A和D的检测及临床意义

Presence of ica A and ica D genes in a collection of coagulase-negative staphylococcal strains in neonatal blood cultures.

目的探讨细胞间粘附基因(ica)A和icaD在新生儿凝固酶阴性葡萄球菌(CNS)败血症中的诊断意义。方法收集北京儿童医院新生儿病房2001年11月至2003年3月间血培养为CNS的患儿为研究入选病例。通过应用聚合酶链反应(PCR)方法检测icaA及icaD的存在。结果在80例入选患儿中,血培养均分离出CNS。根据新生儿败血症的诊断标准,临床诊断败血症27例(33.8%),其中早产儿7例,足月小样儿2例。在菌种的分布上,表皮葡萄球菌18例(66.7%),溶血葡萄球菌7例(25.9%),人葡萄球菌2例(7.4%)。对90株CNS菌株应用PCR方法检测icaA及icaD,共有8株阳性,均为表皮葡萄球菌,并且icaA和icaD同时阳性。在经PCR扩增后所产生的图谱中,icaA在814bp,icaD在282bp。在ica阳性的8例病例中,临床诊断为败血症7例,一致率为87.5%,在临床排除败血症的53例患儿中,仅有1例ica阳性(1.8%)。ica的阳性预测值为25.9%,阴性预测值为98.1%。结论ica基因PCR检测是临床诊断CNS败血症或导管相关感染的一种潜在的实验室方法。

Objective The purpose of this study was to assess whether the person making the clinical decision may benefit from the detection of icaA and icaD genes encoding putative virulent factors.Methods From Nov.2001 to Mar.2003,we detected the icaA and icaD genes in 80 neonates with a collection of clinical isolates from blood cultures by using a simple,rapid,and reliable PCR method.Results An overall total of 80 neonates with CNS strains from blood cultures were identified.There were 27 cases(33.8%)diagnosed neonatal sepsis clinically according to the standard,of which 7 were premature,2 were small for gestational age of full term infants.The distribution of species among the clinical CNS strains,18(66.7%)cases were Staphylococcus epidermidis,which was the leading cause,and then S.hemolyticus ( n =7),S.hominis ( n =2).There was a statistical difference in them.Of the 90 strains,eight were positive to icaA and icaD genes,with PCR products being obtained for the icaA and icaD genes in all of these strains,a 814-bp band for the icaA gene and a 282-bp band for the icaD gene.All of them were Staphylococcus epidermidis.Among 8 cases with positive ica genes,7 were diagnosed as sepsis clinically.The coincidence rate was 87.5%.Positive predictive value of the ica genes were 25.9%,and negative predictive value were 98.1%.Conclusion Ica genes may potentiate the clinical criteria used for the diagnosis of neonatal sepsis,and may discriminate between contamination and infections.