Bacteriologic Diagnosis in Anaerobic Pleuropulmonary Infections

Abstract

Four types of specimens are viewed as having established reliability for the detection of anaerobic bacteria that cause pulmonary infections: blood, pleural fluid, transtracheal aspirates, and transthoracic aspirates. Blood cultures are obviously appropriate diagnostic methods but are positive in <2% of cases [ 1 ] in which the diagnosis is established by alternative methods. Pleural fluid also has unchallenged merit as a specimen but only for the minority of patients with empyema. For most patients with infections restricted to the pulmonary parenchyma, the only diagnostic methods with clearly established merit involve transtracheal aspiration and transthoracic needle aspiration. Transthoracic needle aspiration was done extensively in the preantibiotic era, but more recently its use has been largely restricted to a relatively few practitioners and a highly selective patient population. We are not aware of any practitioner who is doing transthoracic needle aspirations with any frequency for patients with anaerobic pulmonary infections, although the merit of this technique has been established in at least two studies of lung abscess by investigators in France [2] and Spain [3]. There has been extensive experience with transtracheal aspiration that verifies the utility of this technique in obtaining uncontaminated specimens from the lower airways of patients with anaerobic pulmonary infections [4-7] and also establishes the role of anaerobes in lung abscess and aspiration pneumonia [1, 5-7]. Transtracheal aspiration became popular in the late 1960s but almost disappeared from clinical practice after ~ 10 years of extensive use. Several factors contributed to this decline in its use: reports of severe complications, escalating interest in alternative techniques such as fiberoptic bronchoscopy, failure of hospitals to credential qualified physicians for performing this technique (as they do for bronchoscopy), and a common perception that empirical use of antibiotics has largely supplanted any need to es-