Drug resistant tuberculosis in a large southern California hospital.

Rates of in vitro resistance to antituberculous drugs were examined for all patients hospitalized with active tuberculosis between January 1969 and December 1972, and between March 1975 and September 1976. During the former period, in 31.5 per cent of patients, tuberculosis was resistant to one or more drugs, and in 12.3 per cent of patients was resistant to 2 or more drugs. During the latter period, 35.5 per cent of patients had tuberculosis that was resistant to one or more drugs, and 19.6 per cent had tuberculosis resistant to 2 or more drugs. Resistance to isoniazid and ethambutol increased significantly, whereas resistance to para-aminosalicytic acid decreased. Age, national origin, and length of residence in the United States were not good predictors for the presence of in vitro resistance.