Diagnostic Fiberoptic Bronchoscopy and Protected Brush Culture: DISCUSSION part 2
In two of the remaining 11 patients, the result of FOB was considered as possibly false negative. One patient (No. 2) recovered only after a change of treatment from oral penicillin to cefuroxime and from another (No. 10), pneumococcal antigen was detected in sputum after bronchoscopy had been performed. It is possible that an increased sensitivity could have been obtained by the use of bronchoalveolar lavage. However, culture results from BAL fluid may be difficult to interpret since strict quantitation is impossible to perform because the amount of bronchial secretion sampled with the lavage is unknown.
Although, during the main study, patients with probable atypical pneumonia received erythromycin or tetracycline as initial therapy (30 patients, 11 percent) mycoplasmal pneumonia was the most common cause of both early and late therapy failure, with eight of 18 and five of 19 cases, respectively. Of these 13 patients, ten were preliminarily identified clinically and only three underwent bronchoscopy (No. 1, 6, 14). However, a sensitive and rapid diagnostic method for Mycoplasma would clearly facilitate the handling of these patients.
A slow response to adequate antibiotic treatment was also an important reason for therapy failure. This was seen in four patients (No. 8, 11, 17, 18) with pneumococcal pneumonia, and the same mechanism may have applied to the three patients (No. 4, 9, and 12), in whom no etiologic diagnosis was obtained and who initially did not seem to respond to benzylpeni- cillin, but eventually recovered without a change of therapy.
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The CAP with a more unusual etiology formed the third important reason for therapy failure. A Legionella infection was established in two patients and it is important to keep in mind the possibility of obtaining a Legionella diagnosis by culture and indirect immunofluorescence from bronchial secretion, obtained by FOB. In the PB culture of two patients (No. 14 and 15), we found significant growth of a-hemolytic streptococci. One patient had a concomitant M pneumoniae infection (a ciliotoxic effect may predispose to a secondary infection), and the other patient had a preceding aspiration episode. The a-streptococci are considered to cause pneumonia only rarely, being possible to establish as an etiologic agent by invasive methods only. However, in the study of Davidson et al, a-streptococci were demonstrated with percutaneous lung aspiration in two of 25 patients with CAE These authors considered their findings as of unknown significance, but later studies, both with lung aspiration and PB cultures, have confirmed that a-strepto- cocci may be a not uncommon pathogen, especially in patients with necrotizing pneumonia.
Bronchoscopy, with the use of quantitative culture obtained with a PB, is safe and specific and one of the most sensitive diagnostic procedures available. Altogether, we considered nearly 80 percent of the bronchoscopies to be of value for the management of the patients by establishing or verifying an etiologic diagnosis, or by preventing a severe bacterial pneumonia from being inadequately treated. Bronchoscopy also saved time by providing a rapid diagnosis in several patients and the need for broad spectrum antibiotic treatment was reduced. The costs of the bronchoscopy procedure and the PB catheter have recently been discussed. Although these costs are substantial, the use of FOB in selected patients should lead to a rational management of patients with pneumonia, including a reduced need for expensive and ecologically dangerous broad-spectrum antibiotics.
Earlier reports indicate that FOB should not be routinely employed in the diagnosis of uncomplicated bacterial pneumonia, and the importance of basic noninvasive investigations has recently been stressed. This is in agreement with our opinion. One third of our patients had pneumococcal pneumonia, and in all but one, the diagnosis was established by noninvasive diagnostic methods. On the other hand, among untreated patients, we believe that bronchoscopy should, if possible, be performed in those who are immunocompromised or severely ill, especially if intensive care treatment is required. We also think FOB may be considered in the moderately ill patient who cannot produce a sputum specimen and in whom a mycoplasmal infection is improbable.
In patients receiving antibiotics, bronchoscopy is indicated in those who fail to respond to therapy with beta-lactam antibiotics if the probable cause is not M pneumoniae.
Naturally, patients with therapy failure and a suspicion of an anatomic obstruction or of a noninfectious inflammatory disease should undergo bronchoscopy.