A comparison of antibiotic susceptibility testing methods for cotrimoxazole with Burkholderia pseudomallei

Melioidosis is caused by the Gram-negative soil saprophyte, Burkholderia pseudomallei and is endemic in tropical and subtropical regions of southeast Asia and northern Australia. Cotrimoxazole has been traditionally used for the therapy of melioidosis despite results indicating resistance often produced in the disc diffusion test against B. pseudomallei. This inconsistency was addressed by comparing this method with the agar dilution, MicroScan and E-test methods. The results demonstrated that by disc diffusion, 41.3% of 80 B. pseudomallei clinical isolates tested were susceptible to cotrimoxazole, whereas the MicroScan, agar dilution and the E-test demonstrated 92.5, 90 and 97.5% of the isolates to be susceptible, respectively. These results indicate that an MIC based method is required to test the susceptibility of B. pseudomallei against cotrimoxazole.