[Resistance of Mycobacterium tuberculosis in Mexican patients. I. Clinical features and risk factors]

To determine the clinical manifestations associated with resistant M. tuberculosis infection and the antimicrobial resistance in isolates from Mexican patients.

Epidemiological surveillance.

Tuberculosis confirmed cases.

Primary resistance: no history of treatment prior to diagnosis. The following critical concentrations (micrograms/mL) were used for susceptibility: isoniazid 0.2 and 1; rifampin 1 and 5; ethambutol 5 and 10; streptomycin 2 and 10; ethionamide 5; kanamycin 6; and para-aminosalicylic acid (PAS) 2 and 10.

Eighty-four patients with a mean age of 44.7 years were included; 54 men (64%) and 30 women (36%); most patients were from the Mexico City metropolitan area. In 34 patients there was clinical information available, 26 presented fever and weight loss and 8 respiratory symptoms. Fifty-nine patients (70%) were infected by pan-susceptible M. tuberculosis, and 25 (30%) by a resistant isolate; 17 (68%) of them were resistant to at least two drugs, 16 (64%) to isoniazid and rifampin. The proportion of resistance was: isoniazid 24%, rifampin 19%, streptomycin 12%, ethambutol 10%, PAS 9%, etionamide 7%, and kanamycin 6%. Of 47 patients without previous treatment, eight had a resistant microorganism (17%): 9% resistant to isoniazid, 6% to rifampin, 2% to streptomycin, 6% to PAS and 6% multiresistant. Of 37 patients with history of previous treatment for tuberculosis, 17 (46%) had a resistant isolate; 44% were resistant to isoniazid, 35% to rifampin, 24% to streptomycin, 19% to ethambutol, 12% to PAS and 35% multiresistant. Of the 84 patients, four were physicians infected by a resistant isolate, and seven HIV-infected patients, one with a multiresistant isolate, and another with isoniazid resistance.

Antimicrobial resistance among M. tuberculosis is alarmingly high in Mexico City; these results emphasize the importance of case detection and early isolation of patients.