A Novel Virulent Clinical Isolate of Burkholderia pseudomallei Imported from Thailand Exhibiting Resistance to Trimethoprim-Sulfamethoxazole

ABSTRACT. We present the investigation of a Burkholderia pseudomallei strain isolated from the urine of a 56-year-old male returning from a recreational trip to Thailand. The patient initially presented with fever and chills, and lobar as well as bladder and prostate involvement was demonstrated on imaging. Treatment first involved trimethoprim-sulfamethoxazole, the backbone of melioidosis therapy, but was discontinued upon the discovery of resistance to the drug through antimicrobial sensitivity testing via broth microdilution. Further analysis included genomic sequencing, immunotyping, and phenotypic assessment, including virulence testing in an animal model. Results indicated that this strain is a distinct, novel variant with antigenic similarity to other Thai strains displaying high virulence, with a significantly low murine intranasal lethal dose 50% inoculum. The emergence of such a strain, particularly if prevalent in tourist destinations in Thailand, could pose a substantial public health risk, highlighting the need for ongoing vigilance among infectious disease specialists and clinical microbiologists.