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

OBJECTIVE

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

STUDY DESIGN

Epidemiological surveillance.

PATIENTS

Tuberculosis confirmed cases.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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