Clinical consequences and transmissibility of drug-resistant tuberculosis in southern Mexico

Arch Intern Med. 2000 Mar 13;160(5):630-6. doi: 10.1001/archinte.160.5.630.


Background: Consequences of drug-resistant tuberculosis (TB) in developing countries using directly observed treatment, short-course (DOTS), are not well defined.

Objective: To determine the impact of drug resistance on clinical outcome and transmission of TB under programmatic conditions.

Patients and methods: A prospective cohort and molecular epidemiologic study was conducted in southern Mexico. Between March 1995 and February 1998 all patients with persistent cough whose sputa had acid-fast bacilli (AFB) underwent clinical and mycobacteriologic evaluation (species identification, drug susceptibility testing, and IS6110-based genotyping). Treatment was provided in accordance with Mexico's National Tuberculosis Program. Clinical and microbiologic outcomes and molecular epidemiologically defined transmission were measured.

Results: Mycobacterium tuberculosis was isolated from 238 of the 284 AFB smear-positive persons. The overall rate of resistance was 28.4% (new, 20.7%; retreated, 54.7%), and 10.8% (new, 3.3%; retreated, 35.8%) had multi-drug-resistant TB (ie, resistance to isoniazid and rifampin). After treatment, 75% (new, 81.0%; retreated, 52.8%) were cured, 8% (new, 7.8%; retreated, 7.5%) abandoned therapy, 9% (new, 3.9%; retreated, 28.3%) had treatment failure, and 4% (new, 3.3%; retreated, 7.5%) died. Another 2% of patients relapsed, and 9% died during a median of 24.4 months of follow-up. Drug-resistance was a strong independent risk factor for treatment failure. Being infected with multi-drug-resistant TB was the only factor associated with a decreased likelihood of being in a restriction fragment length polymorphism cluster.

Conclusions: Despite the use of DOTS, patients with drug-resistant TB had a dramatically increased probability of treatment failure and death. Although multi-drug-resistant TB may have a decreased propensity to spread and cause disease, it has a profoundly negative impact on TB control.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Antitubercular Agents / pharmacology*
  • Antitubercular Agents / therapeutic use
  • Cluster Analysis
  • Drug Resistance, Microbial
  • Female
  • Humans
  • Male
  • Mexico / epidemiology
  • Middle Aged
  • Multivariate Analysis
  • Mycobacterium tuberculosis / drug effects*
  • Prospective Studies
  • Retreatment
  • Risk Factors
  • Treatment Failure
  • Tuberculosis, Pulmonary / drug therapy*
  • Tuberculosis, Pulmonary / epidemiology
  • Tuberculosis, Pulmonary / transmission*


  • Antitubercular Agents