Starcrossed

Burkholderia pseudomallei

Now, in a paper published in the Proceedings of the National Academies of Science, researchers from the Wellcome Trust-Mahidol University-Oxford Tropical Medicine Research Programme in Bangkok, Thailand, and the University of Cambridge, in collaboration with Colorado State University and Genome Institute of Singapore, have identified how the bacteria develop this resistance.

By comparing the genetic make-up of isolates taken from six patients that had become resistant to ceftazidime against their original infecting ceftazidime-susceptible strain, the researchers found a common, large-scale genomic loss involving at least 49 genes that is thought to arise spontaneously as the bacteria replicate and mutate. The researchers were able to demonstrate that a specific gene within this region was the cause of the drug resistance. This gene provides the genetic ‘code’ to create a protein that is important to bacterial cell division and that is normally the target for ceftazidime.

The researchers , who were funded by the Wellcome Trust, also found that these mutated forms of B. pseudomallei would not grow in common laboratory cultures, including bottles that are normally used to culture blood from people with bacterial infections, as well as the routine culture media used in the diagnostic laboratory. This makes the detection of the drug-resistant forms very difficult. Consequently, patients carrying this strain could continue to be treated with drugs that have become ineffective.