Medical students at risk of nosocomial transmission of Mycobacterium tuberculosis

SETTING: University and teaching hospital in Rio de Janeiro, Brazil, a city with a high prevalence of tuberculosis (TB). OBJECTIVE: To determine whether medical students are at increased risk of nosocomial transmission of Mycobacterium tuberculosis relative to other university students. DESIGN: A cross-sectional study of medical and chemical engineering students in different levels of their training programmes. Information about socio- demographic characteristics, BCG vaccination history, and potential exposures to TB were obtained using a standardised questionnaire. Tuberculin skin testing (TST) was used to determine the prevalence of infection with TB. RESULTS: Medical students have an increasing prevalence of TST positivity as they advance in their training programme to increasing levels of study (4.6%, 7.8%, 16.2%, respectively, P < 0.001), but chemical engineering students do not (4.2%, 4.3%, 4.4%, respectively, P = 0.913). The risks are greatest during the years of clinical training, when medical students have increased contact with patients. CONCLUSIONS: Medical students in this setting may be at increased risk of M. tuberculosis infection, relative to chemical engineering students. A programme of routine tuberculin skin testing is needed, combined with interventions to reduce the risk of nosocomial transmission in the workplace.