Quantitative culture of bronchoalveolar lavage fluid in community-acquiredlower respiratory tract infections

To evaluate the diagnostic value of quantitative bacterial culture of bronc hoalveolar lavage (BAL) fluid obtained by fibreoptic bronchoscopy, 67 conse cutive immunocompetent adult patients admitted to hospital with community-a cquired lower respiratory tract infections from September 1997 to May 1998 were investigated. Results were compared to the findings in eight healthy c ontrol persons investigated in February 1998. There was no difference betwe en study patients and control persons when quantitative culture of total cu mulative bacterial findings or bacteria categorized as members of the oroph aryngeal normal flora were compared. The culture of normal flora in bronchi al washings probably reflects contamination of the lower airways with secre tions from upper airways by the fibreoptic procedure itself, as fractionate d sampling showed a 10-fold reduction in quantitative culture results when a primary bronchial washing was compared to a secondary sampling from the s ame bronchus in the control group. Twenty-four (36%) of 67 patients were cu ltured as positive in the study group while all control persons were cultur ed as negative for bacteria categorized as potential pathogens. With a thre shold value for positive culture of 10(4) cfu ml(-1) the specificity of lav age culture of potential pathogenic bacteria in relation to actual lower ai rway infection was 100%. Therefore, quantitative bacterial culture of poten tial pathogenic bacteria in BAL fluid is very specific but only positive in about one-third of unselected immunocompetent adult patients with a lower respiratory tract infection. (C) 2001 Harcourt Publishers Ltd.