Acquisition of Class C beta-Lactamase PAC-1 by Sequence Type 644 Strains of Pseudomonas aeruginosa

Four sequence type 664 (ST664) (serotype O:5) strains of Pseudomonas aeruginosa that were highly resistant to antibiotics, including ceftolozane-tazobactam and ceftazidime-avibactam, but were susceptible to colistin were found to harbor the gene encoding the rare class C beta-lactamase PAC-1 on a chromosomally located Tn1721-like transposon. The bla(PAC-1) gene was associated with the 16S rRNA methylase determinant rmtF2, which confers pan-aminoglycoside resistance. These genotypically related strains were isolated in repatriated patients from Mauritius and Afghanistan and were close to a lineage reported in Nepal, Pakistan, and India.