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Transmission of Tuberculosis to Household Contacts of Pulmonary Tuberculosis Patients in Southern Mexico
Summary: Dr. Garcia-Garcia studiesthe molecular epidemiology of community transmission of Mycobacterium tuberculosis.
The objective of our work is to determine factors associated with initial tuberculin reactivity and tuberculin conversion among household contacts of pulmonary tuberculosis patients. To this end, we identified, by sputum smear light microscopy and culture, patients in the Orizaba Health Jurisdiction in southeastern Mexico and enrolled them in a prospective molecular epidemiological study. Patients underwent clinical study (interview, physical exam, chest X-ray, anti-HIV antibodies) and mycobacteriologic evaluation (identification, drug-susceptibility testing, and IS6110-based genotyping). Contacts were evaluated for epidemiological and clinical characteristics and tuberculin reactivity. Every three months for up to two years, contacts with negative reactivity were monitored for conversion. Participants were referred for appropriate medical treatment to the national program of tuberculosis.
Between March 2001 and August 2003, we followed 1254 contacts of 353 patients. Tuberculin reactivity was 34 percent (426/1254); conversion was 12 percent (74/615). Paucibacillary tuberculosis (smear negative, culture positive), resistance to isoniazid and rifampin, sharing the bed with the patient, and patient noncompliance to treatment were significantly associated with tuberculin reactivity, after controlling for socioeconomic and household characteristics, age and sex of contact, and age of patient. The proportion of other contacts with tuberculin reactivity in the same household, more than one tuberculosis episode, severity of symptoms, and crowding were significantly associated with conversion. We found that the presence of drug-resistant Mycobacterium tuberculosis and smear positivity were associated with initial tuberculin reactivity but not with tuberculin conversion during follow-up. Inclusion of sociodemographic, clinical, and therapeutic variables did not modify the models.
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