Trimethoprim/sulfamethoxazole resistance in clinical isolates of Burkholderia pseudomallei.
OBJECTIVE
Trimethoprim/sulfamethoxazole is commonly used to treat melioidosis. Antimicrobial susceptibility testing using the disc diffusion method is commonly used in melioidosis-endemic areas, but may overestimate resistance to trimethoprim/sulfamethoxazole.


METHODS
We performed disc diffusion and Etest on isolates from the first positive culture for all patients presenting to Sappasithiprasong Hospital, Ubon Ratchathani, Thailand, with culture-confirmed melioidosis between 1992 and 2003.


RESULTS
The estimated resistance rate for 1976 clinical Burkholderia pseudomallei isolates was 13% by Etest and 71% by disc diffusion. All isolates classed as either susceptible (n=358) or as having intermediate resistance (n=218) on disc diffusion were susceptible by Etest. Only 258 of the 1400 (18%) isolates classed as resistant on disc diffusion were resistant by Etest.


CONCLUSIONS
Disc diffusion testing of B. pseudomallei may be useful as a limited screening tool in resource poor settings. Isolates assigned as 'susceptible' or 'intermediate' by disc diffusion may be viewed as 'susceptible'; those assigned as 'resistant' require further evaluation by MIC methodology.
Wuthiekanun
Vanaporn
V
Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Cheng
Allen C
AC
Chierakul
Wirongrong
W
Amornchai
Premjit
P
Limmathurotsakul
Direk
D
Chaowagul
Wipada
W
Simpson
Andrew J H
AJ
Short
Jennifer M
JM
Wongsuvan
Gumphol
G
Maharjan
Bina
B
White
Nicholas J
NJ
Peacock
Sharon J
SJ
D000890:Anti-Infective Agents / Q000494:pharmacology*; D016957:Burkholderia pseudomallei / Q000187:drug effects*; D004058:Diffusion; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*
D000890:Anti-Infective Agents; D015662:Trimethoprim, Sulfamethoxazole Drug Combination