Acquisition of resistance to ceftazidime-avibactam during infection treatment in Pseudomonas aeruginosa through D179Y mutation in one of two bla KPC-2 gene copies without losing carbapenem resistance.

Ceftazidime/Avibactam (CAZ/AVI) is frequently used to treat KPC-producing Pseudomonas aeruginosa (KPC-PA) and Enterobacterales . CAZ/AVI resistance is driven by several mechanisms. In P. aeruginosa this mainly occurs through alteration of AmpC, porins, and/or efflux pump overexpression, whereas in Enterobacterales it frequently occurs through D179Y substitution in the active site of KPC enzyme. This aminoacid change abolishes AVI binding to the KPC active site, hence inhibition is impaired. However, this substitution also decreases KPC-mediated resistance to carbapenems ("see-saw" effect). The goal of this work was to characterize the in vivo acquisition of CAZ/AVI resistance through D179Y substitution in a KPC-PA isolated from a hospitalized patient after CAZ/AVI treatment. Two KPC-PA isolates were obtained. The first isolate, PA-1, was obtained before CAZ/AVI treatment and was susceptible to CAZ/AVI. The second isolate, PA-2, was obtained after CAZ/AVI treatment and exhibited high-level CAZ/AVI resistance. Characterization of isolates PA-1 and PA-2 was performed through short and long-read whole genome sequencing analysis. The hybrid assembly showed that PA-1 and PA-2A had a single plasmid of 54,030 bp, named pPA-1 and pPA-2 respectively. Each plasmid harbored two copies of the bla _KPC -containing Tn 4401b transposon. However, while pPA-1 carried two copies of bla _KPC-2 , pPA-2 had one copy of bla _KPC-2 and one copy of bla _KPC-33 , the allele with the D179Y substitution. Interestingly, isolate PA-2 did not exhibit the "see-saw" effect. The bla _KPC-33 allele was detected only through hybrid assembly using a long-read-first approach. The present work describes a KPC-PA isolate harboring a plasmid-borne CAZ/AVI resistance mechanism based on two copies of bla _KPC-2 -Tn 4401b and D179Y mutation in one of them, that is not associated with loss of resistance to carbapenems. These findings highlight the usefulness of a fine-tuned combined analysis of short and long-read data to detect similar emerging resistance mechanisms.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor AO-C declared a past collaboration with the authors AW, PG, MA-R, JM, JO-P.
(Copyright © 2022 García, Brito, Alcalde-Rico, Munita, Martínez, Olivares-Pacheco, Quiroz and Wozniak.)