Increasing drug resistance of Mycobacterium tuberculosis in Sinaloa, Mexico, 1997-2005

In 1997 the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) reported high proportions of drug-resistant Mycobacterium tuberculosis in three Mexican states: Sinaloa, Baja California, and Oaxaca. In 2006, we showed that resistance to anti-tuberculosis drugs remained frequent in Sinaloa.

The objectives of this study were to describe drug-resistant tuberculosis (TB) trends and to investigate the probability that patients acquire resistance to first-line anti-TB drugs on recurrence after treatment in Sinaloa.

Sputum specimens were collected from patients diagnosed with TB at all the health care institutions of Sinaloa during 1997-2005. Isolates were tested for susceptibility to first-line drugs.

Among 671 isolates tested from 1997 to 2002, the overall resistance rate was 34.9% (95% confidence interval (CI) 31.2-38.4) with a 1.2% increase per year (Chi-square=4.258, p=0.03906). The prevalence of multi-drug resistance (MDR) was 17.9% (95% CI 14.9-20.7) with a 1.2% increase per year (Chi-square=8.352, p=0.00385). Of 50 patients registered twice between 1997 and 2005, 15 were fully susceptible at first registration, of whom six (40%) acquired drug resistance. Of 35 cases with any drug resistance at first registration, 21 (60%) came to acquire resistance to at least one other drug.

The proportion of drug-resistant TB increased during 1997-2005 in Sinaloa. Major efforts are needed to prevent the further rise and spread of drug-resistant and MDR TB.