Comparision Between the Antimicrobial Susceptibility of Burkholderia pseudomallei to Trimethoprim-Sulfa- methoxazole by Standard Disk Diffusion Method and by Minimal Inhibitory Concentration Determination

PAGAKRONG LUMBIGANON, M.D.*, UNCHALEE TATTA WASATRA, Ph.D.**, PLOENCHAN CHETCHOTISAKD, M.D.***, SURASAKDI WONGRATANACHEEWIN,Ph.D.**, BANDIT THINKHAMROP, M.P.H.****

Affiliation : * Department of Pediatrics, ** Department of Microbiology, *** Department of Medicine, Faculty of Medicine, **** Department of Biostatistics and Demography, Faculty of Public Health, Khon Kaen University. Khon Kaen 40002. Thailand.

AbstractMelioidosis, an infection caused by Burkholderia pseudomallei, usually occurs in immunocompromised patients and requires prolonged antibiotic therapy. Previously, oral trime- thoprim-sulfamethoxazole (TM/SM), an inexpensive and effective drug has been used as a main- tenance therapy. The susceptibility of B. pseudomallei to TM/SM by the standard disk diffusion method is very low. However, some patients who were treated with TM/SM as a maintenance therapy despite the in vitro resistance showed good clinical responses. There were no data com- paring the susceptibility of B. pseudomallei by the standard disk diffusion method with other quantitative susceptibility tests. The objective of this study was to determine the agreement between the antimicrobial susceptibility of B. pseudomallei to TM/SM by standard disk diffusion and minimal inhibitory concentration determination (MIC).
We performed the susceptibility test of 144 strains of B. pseudomallei to TM/SM by both the standard disk diffusion and microbroth dilution MIC. The sensitivity results were 53.5 per cent and 84.0 per cent respectively. The agreement between the 2 tests was very poor (Kappa= 0.14 ; 95% CI = -0.01 to 0.29). The false resistant rate by the standard disk diffusion test was 67.9 per cent. Further in vitro susceptibility and clinical study are needed to define the interpretive criteria that correlate with clinical response.

Keywords : Susceptibility, B. pseudomallei, TM/SM, Disk Diffusion, MIC

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