Abstract

‘JI he isolation and identification of a specific bacterial pathogen permits appropriate antibiotic management of patients with suspected lower respiratory tract infection. The need for a diagnostic technique which provides uncontaminated lower airway secretions was stressed in a recent editorial in Chest.1 While transtracheal aspiration and percutaneous needle aspiration of the lung fulfill this requirement, these methods are sharply invasive, occasionally cause death or life-threatening complications, and most importantly, have not gained wide acceptance even though they have been available for several decades. Fiberoptic bronchoscopy is an attractive alternative for evaluating pulmonary infections because of its widespread use and safety. Unfortunately, secretions routinely obtained by this approach are unsatisfactory due to contamination of the instrument by oropharyngeal bacteria during passage through the upper airways.2 The recent development of a plugged telescoping catheter (PTC) brush3 (BFW brush, Medi-Tech, Watertown, Mass) offers a solution to this problem. Rigorous in vitro testing showed the telescoping catheter to be superior to a single catheter with or without a distal plug, or to a nonpiugged double catheter. This protected brush was also found to be effective in sampling sterile lower respiratory secretions from normal volunteers, and in diagnosing lower respiratory tract bacterial infection in a small group of patients. More recently, the efficacy of this catheter was further demonstrated in a group of 50 patients; quantitative cultures yielded one or more potential pathogens in high colony count in 34 instances.4 In nine of these 34 patients, the same organism was isolated from blood cultures, a surgical specimen, or by transtracheal aspiration, and all 34 patients responded to antimicrobial therapy directed against the predominant pathogen(s). Fourteen of the 16 patients with insignificant growth on culture either had a final diagnosis of nonbacterial lung disease or had received effective antimicrobial therapy prior to their brush study. Legionnaires’ disease and pulmonary tuberculosis were diagnosed in the final two patients by other means; culture of the brush for the responsible organisms was not attempted, however. Methodologic details are important to insure reliable results with the PTC brush. Aerosol anesthesia with 15 ml of 2 to 4 percent lidocaine is performed because the injection of fluid through the inner channel of the bronchoscope washes large numbers of oropharyngeal bacteria into the lower airways.3 A system for quantitative bacterial cultures is mandatory since low concentrations of contaminants are frequently recovered following brushing, making qualitative bacteriology uninterpretable. Because quantitative cultures of serial dilutions are complex, time consuming, and unacceptable for most clinical laboratories, the use of a 0.01 ml calibrated loop, analogous to that employed for u me cultures, is currently being studied (Neil Wimberley and John Bass, personal communication). Other details of the PTC brush procedure deserve mention; their importance in accurately assessing lower respiratory tract bacteriology is less certain, however. Atropine is given to decrease the quantity of saliva. Upper airway secretions are not suctioned into the inner channel of the bronchoscope prior to collecting the brush specimen, and the outer and then the inner catheters are extended for a total distance of 3 to 4 cm beyond the bronchoscope prior to advancing the brush to avoid pooled secretions at the instrument tip. Following removal of the protected brush unit from the bronchoscope, the distal portion of the inner catheter is wiped clean with 70 percent ethanol, and the distal inner catheter and finally the projected brush are severed with sterile instruments. In this issue of Chest (see page 157), Teague and

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