Resistance of Mycobacterium tuberculosis in Zaragoza, Spain (1993-1997) and related factors

BACKGROUND: TO know the frequency of resistance of Mycobacterium tuberculosis in a general hospital and the related factors. PATIENTS AND METHOD: Transversal study of the sensitivity of Mycobacterium tuberculosis in the Hospital Miguel Servet (Zaragoza, Spain) between 1993-1997; the proportions method was used to study the susceptibility. Statistical analysis of conventional tests and significance level at p < 0.05 were performed. RESULTS: Four hundred and twenty height patients with culture-positive to Mycobacterium tuberculosis were studied; 136 (31.8%) were HIV+, 121 (28.3%) were HIV- and in 171 (39.9%) this situation was unknown. In 47 patients (10.9%) the strains isolated were resistant at least to one drug. Primary resistance was 5.9% (22 patients) and acquired resistance was 42.4% (25 patients). Primary resistance in HIV+ patients was 9.2% and in HIV- patients was 7.5%; acquired resistance in HIV+ patients was greater than in HIV- patients (51.8% vs 42.8%). When we compared the resistances between both HIV+ and HIV- patients we did not find significant differences. Twenty isolates (4.7%) were resistant to more than one drug and 10 (2.3%) were resistant to at least isoniazid and rifampin. The risk factors for acquired resistance were alcohol (odds ratio [OR] = 2.65; 95% CI, 1.24-5.65), drugs users (OR = 2.33; 95% CI, 1.05-5.17), previous episodes of tuberculosis (OR = 109.40; 95% CI, 15.02-796.43) and homeless (OR = 3.75; 95% CI, 1.26-11.17); we did not find significant differences between the different risk factors according to primary resistance. CONCLUSIONS: On one study, the resistance of M. tuberculosis is similar to other described in Spain. We haven't found significant differences between both seropositive and seronegative patients. The risk factors for acquired resistance were alcoholism, drug users, previous episodes of tuberculosis and homeless.