In vitro susceptibility of Burkholderia pseudomallei isolates from Thai patients to ceftolozane/tazobactam and ceftazidime/avibactam.

OBJECTIVES

Treatment options are limited for melioidosis patients who develop nosocomial infections due to extensively drug-resistant (XDR) Gram-negative bacilli. Ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA), which have activity against XDR Gram-negative bacteria, are two potential options. Data regarding the susceptibility of Burkholderia pseudomallei to these agents are limited, especially from Thailand, which is an endemic area for melioidosis.

METHODS

A total of 28 B. pseudomallei isolates from melioidosis patients in northeast Thailand were tested for susceptibility to C/T and CZA by Etest and the disk diffusion method. Minimum inhibitory concentrations (MICs) for other antibiotics commonly used in melioidosis, including trimethoprim/sulfamethoxazole (SXT), ceftazidime (CAZ), imipenem (IPM) and meropenem, were also determined.

RESULTS

The MIC of C/T was very low for all isolates, ranging from 0.75 μg/mL to 1.0 μg/mL. For CZA, wide inhibitory zones ranging from 34-35 mm and MICs at 0.5 μg/mL were found. All isolates were also susceptible to SXT, CAZ and IPM based on Clinical and Laboratory Standards Institute (CLSI) breakpoints.

CONCLUSION

C/T and CZA exhibited excellent in vitro activity against B. pseudomallei. Further studies are required to prove efficacy in human subjects.