Risk factors associated with drug-resistant Mycobacterium tuberculosis in Castilla-la-Mancha (Spain)

The aim of this study was to investigate the incidence of primary and secondary resistance to antituberculosis drugs and the risk factors associated with the resistance in southeast Spain. Our research was based on the clinical histories of 276 patients, diagnosed as having tuberculosis by positive culture, who were tested for drug susceptibility between January 1988 and October 1994. The clinical histories were checked by two independent investigators. Drug-resistant strains were isolated from 24 patients (8-7%). Among the 239 patients without previous tuberculosis therapy, 7 (2.9%) were drug-resistant. Among the 37 patients with previous therapy, 17 (46%) were drug-resistant. Seventeen of the 276 patients (6.2%) had resistance to a single drug. Primary resistance to iso- niazid was 1.7%. Previous treatment for tuberculosis (odds ratio (OR) 39.2; 95% confidence interval (95% CI) 10.2-150); hepatic cirrhosis (OR 104; 95% CI 12.8-847); and age 45 yrs and older (OR 4.80; 95% CI 1.15-20.1) were considered risk factors associated with drug-resistant tuberculosis. We conclude that primary and secondary resistance is low in the southeast of Spain and we recommend that susceptibility testing be performed on initial M. tuberculosis isolated from patients with a history of previous tuberculosis therapy, hepatic cirrhosis or more than 44 yrs of age.