Volume 97, Issue 1
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



is the causative agent of melioidosis, a serious infection associated with high mortality and relapse. Current antimicrobial therapy using ceftazidime (CAZ) is often ineffective. Inhibitors of LpxC, the enzyme responsible for lipid A biosynthesis, have potential antimicrobial activity against several Gram-negative bacteria in vivo, but their activity against is unclear. Herein, we investigated the susceptibility of clinical isolates to LpxC-4, an LpxC inhibitor, and LpxC-4 in combination with CAZ. Time-kill assays for bactericidal activity were conducted for K96243, revealing growth inhibition and bactericidal effect at LpxC-4 concentrations of 2 μg/mL and 4 μg/mL, respectively. No significant synergistic effect was observed with the combination of LpxC-4 and CAZ. LpxC-4 susceptibility was tested on three groups of clinical isolates:1) CAZ- and trimethoprim–sulfamethoxazole (SXT)–susceptible ( = 71), 2) CAZ-resistant ( = 14), and 3) SXT-resistant ( = 23) isolates, by broth microdilution. The minimum concentration of LpxC-4 required to inhibit the growth of 90% of organisms was 2 μg/mL for all isolates. The median minimum inhibitory concentration of both the CAZ/SXT-susceptible and CAZ-resistant groups was 1 μg/mL (interquartile range [IQR] = 1–2 μg/mL), compared with 2 μg/mL (IQR = 2–4 μg/mL) for the SXT-resistant group. Cell morphology was observed after drug exposure by immunofluorescent staining, and a change from rod-shaped to cell wall–defective spherical cells was observed in surviving bacteria. LpxC-4 is a potent bactericidal agent against and warrants further testing as a new antibiotic to treat melioidosis.

[open-access] This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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Supplemental Table

  • Received : 31 Oct 2016
  • Accepted : 27 Feb 2017
  • Published online : 24 Apr 2017

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