The vitro efficacy of β-lactam and β-lactamase inhibitors against multidrug resistant clinical strains of Mycobacterium tuberculosis

Abstract

In vitro activity of β-lactam antibiotics and their β-lactamase inhibitor combinations were evaluated for their activity against clinical isolates of Mycobacterium tuberculosis and M. tuberculosis H37Ra. Agar dilution, the BACTEC 460 system and β-lactamase activity tests were used. Results using the BACTEC 460 and enzyme activity tests showed the best β-lactamase inhibitor for M. tuberculosis H37Ra to be clavulanic acid. Cefazolin–clavulanic acid gave the lowest minimal inhibitory concentration (MIC) values using dilution tests and M. tuberculosis H37Ra. β-Lactam antibiotics were combined with clavulanic acid and tested for in vitro activity against 50 selected multidrug-resistant (MDR) and 50 susceptible clinical isolates. Seventy-four percent of the isolates were inhibited by cefazolin–clavulanic acid combination. These results suggested that an appropriate combination of β-lactam and β-lactamase inhibitors might be useful in the treatment of tuberculosis due to multidrug-resistant strains.