In vivo emergence of resistance to novel cephalosporin–β-lactamase inhibitor combinations through the duplication of amino acid D149 from OXA-2 β-lactamase (OXA-539) in sequence type 235 pseudomonas aeruginosa

Abstract

Resistance development to novel cephalosporin–β-lactamase inhibitor combinations during ceftazidime treatment of a surgical infection by Pseudomonas aeruginosa was investigated. Both initial (97C2) and final (98G1) isolates belonged to the high-risk clone sequence type (ST) 235 and were resistant to carbapenems (oprD), fluoroquinolones (GyrA-T83I, ParC-S87L), and aminoglycosides (aacA7/aacA8/aadA6). 98G1 also showed resistance to ceftazidime, ceftazidime-avibactam, and ceftolozane-tazobactam. Sequencing identified blaOXA-2 in 97C2, but 98G1 contained a 3-bp insertion leading to the duplication of the key residue D149 (designated OXA-539). Evaluation of PAO1 transformants producing cloned OXA-2 or OXA-539 confirmed that D149 duplication was the cause of resistance. Active surveillance of the emergence of resistance to these new valuable agents is warranted.