Phenotypic and Genotypic Drug Resistance of Strains Isolated from HIV-Infected Patients from a Third-Level Public Hospital in Mexico.

Background: Drug-resistant tuberculosis (TB) is associated with higher mortality rates in patients with human immunodeficiency virus (HIV). In Mexico, the number of deaths due to TB among the HIV-positive population has tripled in recent years.

Methods: Ninety-three strains isolated from the same number of HIV-infected patients treated in a public hospital in Mexico City were studied to determine the drug resistance to first- and second-line anti-TB drugs and to identify the mutations associated with the resistance.

Results: Of the 93 patients, 82.7% were new TB cases, 86% were male, and 73% had extrapulmonary TB. Most patients (94%) with a CD4 T-lymphocyte count <350 cells/mm were associated with extrapulmonary TB ( <0.0001), whilst most patients (78%) with a CD4 T-lymphocyte count >350 cells/mm were associated with pulmonary TB ( = 0.0011). Eighty-two strains were pan-susceptible, four mono-resistant, four poly-resistant, two multidrug-resistant, and one was extensively drug-resistant. In the rifampicin-resistant strains, S531L was the mutation most frequently identified, whereas the C15T and S315T1 mutations were present in isoniazid-resistant strains. The extensively drug-resistant strain also contained the mutation D94A.

Conclusions: These data highlight the need to promptly diagnose the drug resistance of among all HIV-infected patients by systematically offering access to first- and second-line drug susceptibility testing and to tailor the treatment regimen based on the resistance patterns to reduce the number of deaths in HIV-infected patients.