RAPID DETECTION OF MULTIDRUG-RESISTANT TUBERCULOSIS

Transmission of multidrug-resistant strains of Mycobacterium tuberculo sis (MDR-TB) presents a serious problem for infection control in hospi tals, particularly in the context of co-infection with the human immun odeficiency virus (HIV). We report on the use of molecular genetic too ls to allow rapid assessment of samples from patients potentially infe cted with MDR-TB. Sputum and bronchoalveolar lavage samples were obtai ned from two HIV-positive patients with suspected tuberculosis, who ha d previous contact with a known MDR-TB index case, Polymerase chain re action (PCR) was used directly on clinical samples to amplify genetic loci associated with rifampicin resistance (rpoB), and strain-specific polymorphisms (the direct repeat (DR) region), Drug resistance was de termined using a commercially available kit for detection of point mut ations in the rpoB gene (Inno-Lipa RifTB; Innogenetics, Belgium), and confirmed by nucleotide sequencing, Strain variation was determined us ing the spoligotyping method, based on the presence or absence of vari able linker sequences within the DR region. In one patient, infection with a MDR strain identical to that of a known index case was demonstr ated, A second patient, although positive for M. tuberculosis, was fou nd to be infected with a rifampicin-sensitive strain. Results were obt ained within 48 h, allowing appropriate treatment to be initiated and infection control measures to be implemented. PCR-based tests for stra in-typing and for identification of rifampicin resistance provide impo rtant tools for identifying patients with h MDR-TB and for rapid monit oring of potential nosocomial spread of MDR-TB, Prompt confirmation or exclusion of possible transmission allows early clinical intervention to prevent future outbreaks of multidrug-resistant M. tuberculosis.