[Bacteriology of bronchial secretions. Proposals for a practical attitude in bacterial respiratory tract infections].

Abstract

The inadequacy of the standard bacteriological method in the study of expectorations is unanimously accepted. Oropharyngeal contamination of specimens largely explains why this examination is a poor index of the causative organisms in bacterial respiratory infections. In a mixed clinical situation with few or non-specific signs of bacterial infection and of variable severity, the physician should answer two questions: 1) Is it a bacterial infection? 2) What is the causative organism? and their corollary: 1) Should one prescribe an antibiotic? 2) Which one? Only culture of blood or pleural fluid allow an accurate reply to these questions in about 50% of cases and they are the indispensable investigations of reference. Initial efforts undertaken to improve the standard examination of expectorations never overcome the stumbling block of oro-pharyngeal contaminations. The bacterial count of expectorated bacteria, a non traumatic method, represents some real progress. In 50% of cases it enables a predominant pathogen to be identified before any antibiotics are given. Bronchoscopy diminishes contamination, allows direct sampling and the inspection and biopsying of bronchial mucosal lesions and aids drainage in very suppurative disorders. Trans-tracheal puncture avoids oropharyngeal contamination in the majority of cases and appears to provide reliable results much more often. A pragmatic approach is recommended according to the clinical picture. Bronchial and limited alveolar infections which are well tolerated, heal without exception on blind antibiotic therapy. In suppurating infections (bronchiectasis, cavitating pneumonias), the yield and the reliability of the examinations are increased. Serious bacterial infections, by their extent or by their site, justify a more aggressive diagnostic and therapeutic attitude. It should be stressed, however, that death caused by inadequate antibiotic therapy remains the exception when one or two successive courses of antibiotics have been prescribed for the pathogens presumed responsible according to the clinical picture or found after one or more bacterial examinations.