Contribution of β-lactamases to β-lactam susceptibilities of susceptible and multidrug-resistant Mycobacterium tuberculosis clinical isolates

Abstract

The β-lactamases in 154 clinical Mycobacterium tuberculosis strains were studied. Susceptibilities to β-lactam antibiotics, their combination with clavulanate (2:1), and two fluoroquinolones were determined in 24 M, tuberculosis strains susceptible to antimycobacterial drugs and in nine multiresistant strains. All 154 M. tuberculosis isolates showed a single chromosomal β-lactamase pattern (pl 4.9 and 5.1). M. tuberculosis β- lactamase hydrolyzes cefotaxime with a maximum rate of 22.5 ± 2.19 IU/liter (strain 1382). Neither amoxicillin, carben. icillin, cefotaxime, ceftriaxone, nor aztreonam was active alone. Except for aztreonam, β-lactam combinations with clavulanate produced better antimycobacterial activity.