Legionella pneumophila has emerged in recent years as a frequent pulmonary pathogen in normal and immunosuppressed patients. Direct fluorescent antibody (DFA) examination of respiratory tract secretions and pleural fluid is the most rapid means to establish a laboratory diagnosis. The DFA examination of the sputum for L pneumophila is reported to be very specific (99 percent) and moderately sensitive (70 percent). The DFA staining of the BAL effluent was studied by Kohorst et al in a group of 37 immunosuppressed patients, nine of whom had proven Legionnaires disease (eight had positive culture, one had positive DFA on lung tissue). buy cheap antibiotics
Sputum stains were either negative or inadequate in seven of these patients. The DFA stains of BAL smear were positive in five, suspicious in one, and negative in three (two of them receiving prolonged antibiotic therapy at time of bronchoscopy). Previous antibiotic therapy is known to affect DFA results with the test becoming negative an average of four to six days into treatment. Bronchoalveolar lavage was performed with sterile saline solution, and Legionella grew in seven of nine cultures after an average of 3.5 days. Excessive saline solution, however, may inhibit growth of Legionella and avoidance of this physiologic solution for lavage or transport has been suggested. Transbronchial biopsy specimen may also give positive results, further improving the diagnostic yield of bronchoscopy.
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