A conserved active site PenA ?-lactamase Ambler motif specific for Burkholderia pseudomallei/B. mallei is likely responsible for intrinsic amoxicillin-clavulanic acid sensitivity and facilitates a simple diagnostic PCR assay for melioidosis

Burkholderia pseudomallei is a soil-and water-dwelling Gram-negative bacterium that causes melioidosis in humans and animals. Amoxicillin-clavulanic acid (AMC) susceptibility has been hailed as an integral part of the screening algorithm for identification of B. pseudomallei, but the molecular basis for the in-herent AMC susceptibility of this bacterium remains undefined. This study showed that B. pseudomallei (and the closely-related B. mallei) wild-type strains are the only Burkholderia spp. that contain a 70STSK73 PenA Ambler motif. This motif was present in > 99.5% of 1820 analysed B. pseudomallei strains and 100% of 83 analysed B. mallei strains, and is proposed as the likely cause for their inherent AMC sensitiv-ity. The authors developed a polymerase chain reaction (PCR) assay that specifically amplifies the penA 70ST(S/F)K73-containing region from B. pseudomallei and B. mallei, but not from the remaining B. pseudo-mallei complex species or the 70STFK73 region from the closely-related penB of B. cepacia complex species. The abundance and purity of the 193-bp PCR fragment from putative B. pseudomallei isolates from clinical and environmental samples is likely sufficient for reliable confirmation of the presence of B. pseudomallei. The PCR assay is designed to be especially suited for use in resource-constrained areas. While not further explored in this study, the assay may allow diagnosis of putative B. mallei in culture isolates from animal and human samples.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Automated summary

This study found that Burkholderia pseudomallei and Burkholderia mallei are the only Burkholderia strains that contain the 70STSK73 PenA Ambler motif, which may explain their inherent sensitivity to Amoxicillin-clavulanic acid (AMC). The authors also developed a specific PCR assay to amplify the penA gene, allowing reliable confirmation of the presence of B. pseudomallei.