Switching Partners: Piperacillin-Avibactam Is a Highly Potent Combination against Multidrug-Resistant Burkholderia cepacia Complex and Burkholderia gladioli Cystic Fibrosis Isolates

In persons with cystic fibrosis (CF), airway infection with Burkholderia cepacia complex (Bcc) species or Burkholderia gladioli presents a significant challenge due to inherent resistance to multiple antibiotics. Two chromosomally encoded inducible beta-lactamases, a Pen-like class A and AmpC are produced in Bcc and B. gladioli. Previously, ceftazidime-avibactam demonstrated significant potency against Bcc and B. gladioli isolated from the sputum of individuals with CF; however, 10% of the isolates tested resistant to ceftazidime-avibactam. Here, we describe an alternative antibiotic combination to overcome ceftazidime-avibactam resistance. Antimicrobial susceptibility testing was performed on Bcc and B. gladioli clinical and control isolates. Biochemical analysis was conducted on purified PenA1 and AmpC1 beta-lactamases from Burkholderia multivorans ATCC 17616. Analytic isoelectric focusing and immunoblotting were conducted on cellular extracts of B. multivorans induced by various beta-lactams or beta-lactam-beta-lactamase inhibitor combinations. Combinations of piperacillin-avibactam, as well as piperacillin-tazobactam plus ceftazidime-avibactam (the clinically available counterpart), were tested against a panel of ceftazidime-avibactam nonsusceptible Bcc and B. gladioli. The piperacillin-avibactam and piperacillin-tazobactam-ceftazidime-avibactam combinations restored susceptibility to 99% of the isolates tested. Avibactam is a potent inhibitor of PenA1 (apparent inhibitory constant (K-i app] = 0.5 mu M), while piperacillin was found to inhibit AmpC1 (K-i app = 2.6 mu M). Moreover, piperacillin, tazobactam, ceftazidime, and avibactam, as well as combinations thereof, did not induce expression of bla(penA1) and bla(ampC1) in the B. multivorans ATCC 17616 background. When ceftazidime-avibactam is combined with piperacillin-tazobactam, the susceptibility of Bcc and B. gladioli to ceftazidime and piperacillin is restored in vitro. Both the lack of bla(penA1) induction and potent inactivation of PenA1 by avibactam likely provide the major contributions toward susceptibility. With in vivo validation, piperacillin-tazobactamceftazidime-avibactam may represent salvage therapy for individuals with CF and highly drug-resistant Bcc and B. gladioli infections.