Conditions for the diagnosis of anaerobic lower respiratory tract infections.

The main problem in diagnosing anaerobic lower respiratory tract infections is the differentiation between infection and contamination. The main sourc es of samples are at risk of contamination. The principal sample sources ar e from the bronchial tree; blood cultures are seldom positive and serology is of no use. Fusobacterium, Prevotella and Streptococcus are all commensal with buccopharyngeal flora and the main organisms in anaerobic pleuropulmo nary infections. These bacteria are all very sensitive to dessication and t he toxic action of oxygen. The overgrowth of a bacteria can avoid the devel opment of the real pathogens. For all these reasons we recognize four steps to optimizing the microbiological diagnosis: to achieve a good timing betw een the clinical ward and the laboratory in order to provide specific trans port means; to assure the best sampling possible, either thoracocentesis fo r empyema, abscess and necrotizing pneumonia or protected distal sampling ( brush, lavage), and transtracheal or transthoracic aspiration for pneumonia with quantitative cultures; to assure the transportation to the laboratory in the best conditions and to avoid the loss of time; and to be critical a bout the results with regard for the risk of contamination of the sample. ( C) 2000 Editions scientifiques et medicales Elsevier SAS.