Kurlat I, Stoll B J, McGowan J E
Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30335.
J Clin Microbiol. 1989 May;27(5):1068-71. doi: 10.1128/jcm.27.5.1068-1071.1989.
The blood culture results of all samples obtained from newborns at Grady Memorial Hospital, Atlanta, Ga., during a 6-month period were analyzed to determine the time required for a blood culture to become positive, the time at which a culture could safely be considered negative, and the spectrum of isolated organisms. During the study period, 1,248 samples were submitted from all nurseries and processed by an automated detection instrument (BACTEC NR660). Of the 1,248 samples, 98 (7.8%) were positive by the end of a 7-day processing period; 29 of the 98 were classified as definite bacterial pathogens, 52 were classified as possible bacterial pathogens, 9 were classified as yeasts, and 8 were classified as contaminants. Virtually all organisms (28 of 29) categorized as definite pathogens were identified by day 2 of processing, and all were identified by day 4. All isolates of group B streptococcus, Escherichia coli, Klebsiella species, and Staphylococcus aureus were identified by day 2. Of all positive blood cultures, 79% were identified by day 2, 88% were identified by day 3, and 94% were identified by day 4. Of the 21 isolates identified after day 2, the only definite pathogen was from a sick baby in the intensive care unit. From among the 870 term low-risk newborns cultured because of maternal risk factors, only four possible pathogens were identified after day 2. The positive and negative predictive values of blood culture at days 2 and 4 were 92 and 99%, respectively. We conclude that, in our institution, (i) a 2-day processing period is sufficient to detect positive blood cultures in the asymptomatic term infant, (ii) a 4-day processing period will detect virtually all clinically important infections, and (iii) clinical yield from continuing blood culture processing beyond 4 days does not justify the time and cost involved.
对从佐治亚州亚特兰大市格雷迪纪念医院新生儿处采集的所有样本进行了为期6个月的血培养结果分析，以确定血培养呈阳性所需的时间、可安全判定培养为阴性的时间以及分离出的微生物种类。在研究期间，从所有托儿所提交了1248份样本，并由自动检测仪器（BACTEC NR660）进行处理。在这1248份样本中，98份（7.8%）在7天的处理期结束时呈阳性；98份中的29份被归类为明确的细菌病原体，52份被归类为可能的细菌病原体，9份被归类为酵母菌，8份被归类为污染物。几乎所有被归类为明确病原体的微生物（29份中的28份）在处理的第2天就被鉴定出来，所有的在第4天被鉴定出来。B组链球菌、大肠杆菌、克雷伯菌属和金黄色葡萄球菌的所有分离株在第2天就被鉴定出来。在所有阳性血培养中，79%在第2天被鉴定出来，88%在第3天被鉴定出来，94%在第4天被鉴定出来。在第2天后鉴定出的21份分离株中，唯一的明确病原体来自重症监护病房的一名患病婴儿。在因母亲风险因素而进行培养的870名足月低风险新生儿中，第2天后仅鉴定出4种可能的病原体。第2天和第4天血培养的阳性和阴性预测值分别为92%和99%。我们得出结论，在我们的机构中，（i）2天的处理期足以检测无症状足月婴儿的阳性血培养，（ii）4天的处理期将检测到几乎所有临床上重要的感染，（iii）血培养处理超过4天的临床收益不足以证明所涉及的时间和成本是合理的。
