Burkholderia pseudomallei Clinical Isolates Are Highly Susceptible In Vitro to Cefiderocol, a Siderophore Cephalosporin.

Cefiderocol is a cephalosporin designed to treat multidrug-resistant Gram-negative infections. By forming a chelated complex with ferric iron, cefiderocol is transported into the periplasmic space via bacterial iron transport systems and primarily binds to penicillin-binding protein 3 (PBP3) to inhibit peptidoglycan synthesis. This mode of action results in cefiderocol having greater in vitro activity against many Gram-negative bacilli than currently used carbapenems, β-lactam/β-lactamase inhibitor combinations, and cephalosporins. Thus, we investigated the in vitro activity of cefiderocol against a total of 246 clinical isolates of Burkholderia pseudomallei from Queensland, Australia. The collection was composed primarily of bloodstream (56.1%), skin and soft tissue (16.3%), and respiratory (15.9%) isolates. MICs of cefiderocol ranged from ≤0.03 to 16 mg/liter, whereas the MIC90 was 0.125 mg/liter. Based upon CLSI clinical breakpoints for cefiderocol against Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia, three isolates (1.2%) would be classified as nonsusceptible (MIC > 4 mg/liter). Using EUCAST non-species-specific (pharmacokinetic/pharmacodynamic [PK/PD]) clinical breakpoints or those set for Pseudomonas aeruginosa, four isolates (1.6%) would be resistant (MIC > 2 mg/liter). Further testing for coresistance to meropenem, ceftazidime, trimethoprim-sulfamethoxazole, amoxicillin-clavulanate, and doxycycline was performed on the four isolates with elevated cefiderocol MICs (>2 mg/liter); all isolates exhibited resistance to amoxicillin-clavulanic acid, while three isolates also displayed resistance to at least one other antimicrobial. Cefiderocol was found to be highly active in vitro against B. pseudomallei primary clinical isolates. This compound shows great potential for the treatment of melioidosis in countries of endemicity and should be explored further.