Bacterial gene loss as a mechanism for gain of antimicrobial resistance

► We describe a novel ceftazidime resistance mechanism in Burkholderia pseudomallei. ► We analysed paired ceftazidime-susceptible and ceftazidime-resistant isolates from 6 patients. ► We found a large genomic deletion of 49 genes in the ceftazidime-resistant strains. ► We found that ceftazidime resistance was due to deletion of a PBP3 gene. ► This provides a possible explanation for ceftazidime treatment failure.