Primary drug resistance among pulmonary treatment-naïve tuberculosis patients in Amazonas State, Brazil.

BACKGROUND: Multidrug-resistant tuberculosis (MDR-TB) is the main indicator of previous treatment in tuberculosis (TB) patients. MDR-TB among treatment-naïve patients indicates infection with drug-resistant Mycobacterium tuberculosis strains, and such cases are considered primary drug-resistant cases. OBJECTIVE: To estimate the prevalence of drug resistance in pulmonary TB (PTB) treatment-naïve patients and to identify the socio-demographic and clinical characteristics of the resistant population. METHODS: A total of 205 treatment-naïve PTB patients from Manaus, Amazonas State, Brazil, were enrolled. Drug susceptibility testing (DST) was performed on all positive mycobacterial cultures using the 1% proportion method. RESULTS: Positive M. tuberculosis cultures were obtained from only 175 patients for DST. The prevalence of primary MDR-TB was 1.7% (3/175); 14.3% (25/175) of the cultures presented resistance to at least one of the drugs. Resistance to streptomycin, isoniazid, rifampicin and ethambutol was respectively 8.6%, 6.9%, 3.4% and 2.3%. An association between TB patients with resistance to more than one drug and known previous household contact with a TB patient was observed (P= 0.008, OR 6.7, 95%CI 1.2-67.3). CONCLUSIONS: Although the prevalence of primary MDR-TB currently is relatively low, it may become a major public health problem if tailored treatment is not provided, as resistance to more than one drug is significantly associated with household contact.