Drug resistance trends among previously treated tuberculosis patients in a national registry in Peru, 1994-2001

National mycobacteriology reference laboratory in Peru conducting routine testing of susceptibility to isoniazid, rifampin, ethambutol, pyrazinamide, and streptomycin, in Mycobacterium tuberculosis isolates from previously treated patients.

To determine the percentage of isolates resistant to each of five anti-tuberculosis agents and to ascertain in these data the presence of trends of clinical relevance.

Retrospective study of a national registry of M. tuberculosis isolates from patients referred for drug susceptibility testing between 1994 and 2001.

Among 14,736 isolates tested, 10,837 (73.5%, 95%CI 72.8-74.3) demonstrated anti-tuberculosis resistance, and 8455 (57.4%, 95%CI 56.6-58.2) demonstrated resistance to at least both isoniazid and rifampin, by convention defined as multidrug-resistant tuberculosis (MDR-TB). A significant increasing trend could be discerned for resistance to each of the drugs tested and in isolates classified as MDR-TB (P < 0.001 for trend). Additional clinically relevant trends were found in polyresistance and multidrug resistance percentages.

Data from a national reference laboratory can be used to inform the design of retreatment regimens.