Drug resistance profiles of Mycobacterium tuberculosis isolates: five years' experience and insight into treatment strategies for MDR-TB in Lima, Peru.

SETTING Lima, Peru. OBJECTIVE To describe drug resistance profiles of TB isolates from patients at risk for multidrug-resistant tuberculosis (MDR-TB), and to consider the implications of these findings for treatment. DESIGN Descriptive study of drug susceptibility testing (DST) results for TB isolates from 1680 patients referred for suspicion of MDR-TB between 1996 and 2001. RESULTS Of 1680 isolates tested, 1144 (68%) were resistant to at least one anti-tuberculosis drug and 926 (55%) were MDR-TB strains. Of 926 MDR isolates, 50 (5%) were resistant to INH and RMP alone, while 367 (40%) were resistant to at least five first-line drugs. We identified 146 unique drug resistance profiles, the most common of which accounted for 11% of drug-resistant isolates. The annual prevalence of isolates with resistance to at least five first-line drugs rose significantly during the study period, from 29% to 37% (P = 0.00086). CONCLUSIONS This is a group of patients with TB disease among whom the prevalence of a broad spectrum of often highly drug-resistant strains appears to be increasing over time. A single standardized retreatment regimen may be inadequate to cure most patients. Capacity for drug sensitivity testing is essential for development of multiple standardized retreatment or individualized treatment regimens and epidemiological surveillance for planning.