Resistance to Ceftazidime-Avibactam Is Due to Transposition of KPC in a Porin-Deficient Strain of Klebsiella pneumoniae with Increased Efflux Activity

Abstract

Ceftazidime-avibactam is an antibiotic with activity against serine beta-lactamases, including carbapenemase (KPC). Recently, reports have emerged of KPC-producing isolates resistant to this antibiotic, including a report of a wild-type KPC-3 producing sequence type 258 that was resistant to ceftazidime-avibactam. We describe a detailed analysis of this isolate, in the context of two other closely related KPC-3 producing isolates, recovered from the same patient. Both isolates encoded a nonfunctional OmpK35, whereas we demonstrate that a novel T333N mutation in OmpK36, present in the ceftazidime-avibactam resistant isolate, reduced the activity of this porin and impacted ceftazidime-avibactam susceptibility. In addition, we demonstrate that the increased expression of and observed in the ceftazidime-avibactam-resistant isolate was due to transposition of the Tn transposon harboring into a second plasmid, pIncX3, which also harbored, ultimately resulting in a higher copy number of in the resistant isolate. pIncX3 plasmid from the ceftazidime-avibactam resistant isolate, conjugated into a OmpK35/36-deficient background that harbored a mutation to the regulator of the efflux operon recreated the ceftazidime-avibactam-resistant MIC of 32 μg/ml, confirming that this constellation of mutations is responsible for the resistance phenotype.

In Vitro Activity of Ceftazidime-Avibactam against Clinical Isolates of Enterobacteriaceae and Pseudomonas aeruginosa Collected in Latin American Countries: Results from the INFORM Global Surveillance Program, 2012 to 2015

“…Of these, two isolates were resistant to carbapenems, all were nonsusceptible or resistant to aztreonam, ceftazidime, and cefepime, and all displayed elevated MICs to another tested avibactam-cephalosporin combination. The mechanism(s) of reduced susceptibility remain to be determined for these isolates but may reflect the presence of an avibactam-insensitive ␤-lactamase that was not detected using the current molecular algorithm (20,21) or a combination of mechanisms, such as increased KPC production with porin deficiency and altered efflux (22)(23)(24). Sequence insertions in penicillinbinding protein 3 have also been reported to result in reduced susceptibility to avibactam-cephalosporin combinations, although ceftazidime-avibactam remained active (MIC Յ8 g/ml) against the isolates reported to date (25,26).…”

Resistance Trends and Treatment Options in Gram-Negative Ventilator-Associated Pneumonia

“…A phase III non-inferiority nosocomial pneumonia trial [60] found ceftazidime-avibactam was non-inferior to meropenem with respect to 28-day mortality [risk difference (RD): 1.5%; 95% CI: −2.4–5.3] and cure [RD: 1.9%; 95% CI: −8.1–4.3] without resistance emerging [60]. Of concern, though, are numerous reports of resistance to this agent are already appearing [61–63] including treatment-emergent resistance [64]. …”

Beware of broad-spectrum generalizations: ceftazidime-avibactam compared to meropenem for the treatment of gram-negative pneumonia

“…Because CA use will largely be used in infections from CRE as opposed to MERO-susceptible isolates, this paper provides important and relevant data when considering its use in a real life manner. Lastly, de novo resistance (11) and evolution of resistance during CA treatment (including for pneumonia) have also been reported from other centers (3,12). This raises the possibility of a relatively low barrier to resistance for CA and has important implications for antibiotic stewardship programs.…”