For several reasons, bronchoscopy is especially suited for diagnosing pulmonary infections in immunocompromised patients, but it is less suited for the diagnosis in immunocompetent patients:
(1) Immunocompromised patients are more prone to develop pulmonary infections with certain pathogens, such as P carinii, mycobacteria, HSV, СМУ and Aspergillus species (henceforth, these pathogens will be referred to as specific pathogens, requiring specific therapy, as opposed to empirical therapy). In our study, these organisms were found in 9/30 (30 percent) of the immunocompromised patients and 5/32 (16 percent) of the immunocompetent patients.
(2) The clinical picture in these infections is nonspecific and not conclusive enough to indicate specific organisms, and hence, guide specific therapy.
Microscopy on Gram-stained preparations from the NSB was done in 53 of the 62 cases. Bacteria were found in 12 microscopies (14 different bacteria), of which 4 were therapeutically guiding.
Transbronchial biopsy was not a part of the standardized program, but for different reasons it was done in 18 of the 62 patients. Six of the 18 biopsy specimens were negative, and 7 showed nonspecific inflammatory changes. In five biopsy specimens, there were pathologic changes: alveolitis due to rejection of lung transplant (n = 2), fibrosing alveolitis (n=l), P carinii (n = l), and leukemic infiltrations (n = l). All findings were therapeutically guiding.
The different microbiologic analyses with numbers of positive findings and therapeutically guiding findings from the 62 bronchoscopies are listed in Table 1. Obtained microorganisms are listed in Table 2. In 15 bronchoscopies, all analyses were negative. In the other 47 bronchoscopies, at least 1 microorganism was found, of which a therapeutically guiding result was obtained from 22 bronchoscopies (Table 3). Antibiotics had been given prior to the bronchoscopy in six of these patients.
Cultures from the PSB were analyzed in 61 of the 62 cases. In one patient, a brush sample was not obtained due to a hemorrhagic diathesis. Of 14 positive cultures, 10 were therapeutically guiding.
The tube with the PSB was vortexed vigorously. One hundred microliters of fluid, undiluted and diluted 1/100, was inoculated on two blood agar plates, and 100 ц.1 of undiluted fluid was inoculated on one hematin agar plate. The blood agar plates were incubated at 37°C in air and in anaerobic atmosphere, respectively. The hematin agar plate was incubated at 37°C in a C02-enriched atmosphere. The plates were observed for growth after one and two days. Recovery of ^lO cfu/ml of a particular pathogen was considered as significant growth.
Portions from BAL fluid were used for cultivation of Legionella, Mycobacteria, fungi, and viruses. Cultivation of Legionella was performed on the first portion of BAL with sterile water: BAL fluid without pretreatment and fluid decontaminated with KCl-HCl buffer was inoculated on BCYEa medium (buffered charcoal yeast extract agar with added a-ketoglutarate) and В MPA medium (BCYEa medium containing cefamandole, polymyxin B, and ani-somycin). The cultures were incubated at 37°C for five days. Fluid for culture of Mycobacteria was decontaminated with sodium lauryl sulphate and sodium hydroxide. After centrifugation, the pellet was neutralized with sulfuric acid and inoculated onto three drug-free Lowenstein-Jensen (LJ) culture tubes and one LJ culture tube containing 0.4 mg of isoniazid per liter. The cultures were incubated at 37°C in 5 percent CO* for one week, and thereafter at 37°C in air for nine weeks. Lavage fluid for culture of fungi was centrifuged and the pellet was inoculated on brain heart infusion (BHI) and Sabouraud agar. The agar plates were incubated at 20°C, 30°C, and 37°C for 14 days.
During the period December 19, 1986 to November 24, 1989, 62 diagnostic fiberoptic bronchoscopies on 53 patients with suspected pulmonary infections were performed at the Lund Hospital. All these patients were evaluated in the study. The median age of the patients was 49 years (range, 24 to 79 years). Five of the 62 bronchoscopies were done on 4 patients who tested positive for human immunodeficiency virus (HIV) and 2 bronchoscopies were done on a patient who tested positive for hepatitis В surface antigen. Eight bronchoscopies were performed on patients receiving mechanical ventilation, and one other patient was examined during general anesthesia.
Fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) is now an established method of increasing importance in the etiologic diagnosis of pneumonia. The protected specimen brush (PSB) technique allows sampling from the lower airways, uncontaminated by the oropharyngeal bacterial flora. This technique also enables a quantitative culture. Data suggest that a quantitative culture with a level greater than 103 cfu/ml could be used as a guide for antimicrobial therapy. Bronchoalveolar lavage fluid obtained from normal subjects is frequently contaminated by bacteria from the upper airways. Nevertheless, recovery from BAL of several different pathogens such as Pneumocystis carinii, Legionella species, and Mycobacterium tuberculosis10 is conclusive. Others, such as herpes simplex virus (HSV), cytomegalovirus (CMV), nontuberculous mycobacteria, Aspergillus species, and Candida species can also be isolated from BAL fluid in patients without invasive disease. Thus, isolation in BAL of these organisms is not diagnostic of infection.