Mycobacterial culture results of smear-positive patients with suspected pulmonary tuberculosis in Liverpool

Abstract

The aim of this study was to assess the final mycobacterial culture results of patients with smear-positive sputum or bronchial washings and to investigate the efficiency of local tuberculosis (TB) contact-tracing. Retrospective analysis of mycobacterial cultures and contact-tracing was performed in every patient with smear-positive sputum or bronchoalveolar lavage (BAL) in two Liverpool teaching hospitals (1996-1998). Of these patients 116 with smear-positive sputum or BAL were identified. Mycobacterium tuberculosis (M. tuberculosis) was cultured in 57 (49%), environmental mycobacteria in 37 (32%) and cultures were negative in 22 (19%) of the patients. Contact-tracing information was available in 107 of the 116 (92%) patients. A total number of 1,357 contacts were screened for possible tuberculosis. Of these, 420 (31%) were contacts of patients who cultured environmental organisms or had negative cultures. In this study, 51% of smear-positive patients in Liverpool did not have tuberculosis. Inefficiencies in current contact-tracing procedures have been identified which result from screening contacts of index cases that are subsequently found not to have cultured Mycobacterium tuberculosis. The authors believe that there are clear grounds for using rapid tests to identify and type mycobacteria more quickly than current solid or liquid media methods. It is also suggested that regional variations in the frequency of infection with environmental mycobacteria should be considered when formulating tuberculosis contact-tracing procedures.