Senger Suheyla Serin, Saccozza Mine Erdenizmenli, Yuce Ayse
Department of Infectious Diseases and Clinical Microbiology, Baskent University, Ankara, Turkey.
Infect Control Hosp Epidemiol. 2007 Aug;28(8):992-6. doi: 10.1086/518753. Epub 2007 Jun 19.
To evaluate the specificity and sensitivity of the clinical criteria widely used to differentiate true coagulase-negative staphylococcal (CoNS) bacteremia from contamination, using pulsed-field gel electrophoresis (PFGE) as the reference test.
The study sample consisted of 79 CoNS isolates recovered from cultures of blood from 38 patients. Medical charts of the patients were reviewed for demographic and clinical information. The relatedness of CoNS strains recovered from 2 or more successive blood cultures was analyzed by PFGE. Patients from whom similar strains were recovered were assumed to have true bacteremia, whereas patients from whom different strains were recovered were considered to have contaminated blood cultures. The clinical criteria comprised Centers for Disease Control and Prevention (CDC) surveillance definitions for bloodstream infection (BSI), as well as an alternative criterion based on the presence of fever, the presence of leukocytosis, the absence of another recognized infection, and the recovery of CoNS from 2 or more successive blood cultures.
Nineteen (50%) of the 38 patients had bacteremia due to similar strains; the remaining patients had bacteremia due to different strains. Criterion 2a of the CDC definition for BSI had a sensitivity of 100% and a specificity of 31.6% for distinguishing between true bacteremia and contamination. CDC criterion 2b had a sensitivity of 78.9% and a specificity of 52.6%.
Molecular typing correlated poorly with the clinical criteria for true bacteremia. In view of the limited applicability of clinical criteria, more studies are needed to improve them. Periodic cross-sectional studies based on PFGE findings might be useful to estimate local contamination rates in an institution, which in turn can be used to improve the accuracy of the clinical diagnosis of bacteremia.
以脉冲场凝胶电泳（PFGE）作为参考检测方法，评估广泛用于区分真正的凝固酶阴性葡萄球菌（CoNS）菌血症与污染的临床标准的特异性和敏感性。
研究样本包括从38例患者的血培养物中分离出的79株CoNS。查阅患者的病历以获取人口统计学和临床信息。通过PFGE分析从2次或更多次连续血培养中分离出的CoNS菌株的相关性。从其体内分离出相似菌株的患者被认为患有真正的菌血症，而从其体内分离出不同菌株的患者则被认为血培养受到污染。临床标准包括疾病控制和预防中心（CDC）对血流感染（BSI）的监测定义，以及基于发热、白细胞增多、无其他公认感染以及从2次或更多次连续血培养中分离出CoNS的替代标准。
38例患者中有19例（50%）因相似菌株导致菌血症；其余患者因不同菌株导致菌血症。CDC对BSI定义的标准2a区分真正菌血症和污染的敏感性为100%，特异性为31.6%。CDC标准2b的敏感性为78.9%，特异性为52.6%。
分子分型与真正菌血症的临床标准相关性较差。鉴于临床标准的适用性有限，需要更多研究来改进它们。基于PFGE结果的定期横断面研究可能有助于估计机构内的局部污染率，进而可用于提高菌血症临床诊断的准确性。
