Seligman Renato, Seligman Beatriz Graeff Santos, Konkewicz Loriane, Dos Santos Rodrigo Pires
Hospital de Clinicas de Porto Alegre, Rua Ramiro Barcelos 2350, 90035-003 Porto Alegre, Brazil ; Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2400 - 4o Andar, 90035-003 Porto Alegre, Brazil.
Hospital de Clinicas de Porto Alegre, Rua Ramiro Barcelos 2350, 90035-003 Porto Alegre, Brazil.
BMC Anesthesiol. 2015 Jan 23;15(1):19. doi: 10.1186/1471-2253-15-19. eCollection 2015.
The Gram stain can be used to direct initial empiric antimicrobial therapy when complete culture is not available. This rapid test could prevent the initiation of inappropriate therapy and adverse outcomes. However, several studies have attempted to determine the value of the Gram stain in the diagnosis and therapy of bacterial infection in different populations of patients with ventilator-associated pneumonia (VAP) with conflicting results. The objective of this study is to evaluate the accuracy of the Gram stain in predicting the existence of Staphylococcus aureus infections from cultures of patients suspected of having VAP.
This prospective single-center open cohort study enrolled 399 patients from December 2005 to December 2010. Patients suspected of having VAP by ATS IDSA criteria were included. Respiratory secretion samples were collected by tracheal aspirate (TA) for standard bacterioscopic analysis by Gram stain and culture.
Respiratory secretion samples collected by tracheal aspirates of 392 patients were analyzed by Gram stain and culture. When Gram-positive cocci were arranged in clusters, the sensitivity was 68.4%, specificity 97.8%, positive predictive value 88.1% and negative predictive value 92.8% for predicting the presence of Staphylococcus aureus in culture (p < 0.001).
A tracheal aspirate Gram stain can be used to rule out the presence of Staphylococcus aureus in patients with a clinical diagnosis of VAP with a 92.8% Negative Predictive Value. Therefore, 7.2% of patients with Staphylococcus aureus would not be protected by an empiric treatment that limits antimicrobial coverage to Staphylococcus aureus only when Gram positive cocci in clusters are identified.
当无法获得完整培养结果时，革兰氏染色可用于指导初始经验性抗菌治疗。这种快速检测可防止不适当治疗的启动及不良后果。然而，多项研究试图确定革兰氏染色在不同人群呼吸机相关性肺炎（VAP）细菌感染诊断和治疗中的价值，结果相互矛盾。本研究的目的是评估革兰氏染色在预测疑似VAP患者培养物中金黄色葡萄球菌感染存在情况时的准确性。
这项前瞻性单中心开放队列研究在2005年12月至2010年12月期间纳入了399例患者。纳入符合美国胸科学会（ATS）和美国感染病学会（IDSA）标准疑似患有VAP的患者。通过气管抽吸（TA）收集呼吸道分泌物样本，用于革兰氏染色和培养的标准细菌学分析。
对392例患者经气管抽吸收集的呼吸道分泌物样本进行了革兰氏染色和培养分析。当革兰氏阳性球菌呈簇状排列时，预测培养物中存在金黄色葡萄球菌的敏感性为68.4%，特异性为97.8%，阳性预测值为88.1%，阴性预测值为92.8%（p < 0.001）。
气管抽吸物革兰氏染色可用于排除临床诊断为VAP患者中金黄色葡萄球菌的存在，阴性预测值为92.8%。因此，当仅在识别出簇状革兰氏阳性球菌时将经验性治疗的抗菌覆盖范围限制为金黄色葡萄球菌时，7.2%的金黄色葡萄球菌感染患者将得不到保护。
