Investigation Of Cross-resistance Between Rifampin And Rifabutin In Multidrug Resistant Mycobacterium Tuberculosis Complex Strains

Objective To study the cross-resistance between rifampin and rifabutin in multidrug resistant Mycobacterium tuberculosis complex strains, and therefore to provide laboratory data for using rifabutin in the treatment of multidrug resistant tuberculosis.Methods Analysis was conducted on drug susceptibility tests to isoniazid, rifampin, ofloxacin, streptomycin, ethambutol, amikacin and capreomycin of the pulmonary tuberculosis patients with sputum culture positive in Shanghai Pulmonary Hospital Affiliated Tongji Uniersity from June2009to January2011. The MIC90of rifabutin and rifampin against99multidrug resistant Mycobacterium tuberculosis clinical strains were determined by microplate assays.Results The cross-resistance rate between rifampin and rifabutin was85.9%, but the MIC90of rifabutin (<16mg/L, median2mg/L) was significantly lower than those of rifampin(>2mg/L, median>32mg/L).The MIC90of rifabutin were8to32times lower than those of rifampin. The cross-resistance strains in the lower and the median groups were0/9and5/9respectively, the strains of the higher rifampin-resistant group were almost all cross-resistant (98.8%,80/81)(χ2=9.14, P<0.01). The cross-resistance rate between rifampin and rifabutin increased with the resistance level of rifampin. It was confirmed that different drug resistance spectrum (P=0.799) was not significantly associated with the cross-resistance rate between rifampin and rifabutin.Conclusions Rifabutin had activities against multidrug resistant Mycobacterium tuberculosis complex strains in vitro, and therefore may be used as an alternative for the treatment of multidrug resistant tuberculosis.