[Incidence of resistance and risk factors for resistance in Mycobacterium tuberculosis. A retrospective study of 1,055 patients of a specialty hospital 1984 to 1993].

For the past decade, there have been no data on the time course of drug-resistant tuberculosis and on risk factors for drug resistance in former West Germany. We reviewed the medical records of all patients with positive cultures for Mycobacterium tuberculosis from 1984 until 1993 in a hospital near Hamburg. Drug-susceptibility testing was performed for isoniazid, rifampicin, ethambutol, and streptomycin, using the modified proportion method. Of 1,055 patient, 9.6% had isolates resistant to one or more drugs. Of the isolates, 5.8% showed resistance to isoniazid or rifampicin and 1.8% to both isoniazid and rifampicin. There was no significant change of the resistance rate during the study period. Twenty six percent of 89 patients from South America, Africa or Asia had isolates resistant to one or more drugs, compared with 7.6% of 799 patients born in Germany (odds ratio (OR) 4.2; 95% confidence interval (95% CI) 2.5-7.3). Among patients born in Germany, 32% of 101 patients with a history of prior antituberculosis drug therapy had resistant organisms, versus 4.2% of 698 patients without prior therapy (OR 10.7; 95% CI 6.1-18.7). Resistance orates for 35 patients, who had been treated within the last 5 yrs, and for 65 patients, who had been treated more than 5 yrs ago, were 57 and 17%, respectively (OR 6.6; 95% CI 2.9-16.6). Our results suggest that there is no increase in the proportion of drug-resistant tuberculosis in our hospital, and that patients with a recent history of antituberculosis drug therapy and patients from South America, Africa, or Asia are at high risk for drug resistance.