Intravenous ceftazidime-avibactam successfully treated 59% of carbapenem-resistant Enterobacteriaceae (CRE) infections, and 76% of patients remained alive at 30 days, according to a retrospective cohort study published in Clinical Infectious Diseases.

Those rates resemble previous reports of treatment with in vitro active agents, while the rate of acute kidney injury was about a third lower, said Ryan K. Shields, PharmD, of the University of Pittsburgh, and his associates. But 8% of CRE infections developed ceftazidime-avibactam resistance, which accounted for about a third of microbiological failures, the researchers said. “It is incumbent upon health care providers to share their clinical experiences with ceftazidime-avibactam and other new beta-lactamase inhibitors, so these agents can be used most effectively for the longest period of time,” they added.

Ceftazidime-avibactam (Avycaz) is a novel beta-lactam/beta-lactamase inhibitor combination approved by the Food and Drug Administration in 2015 for complicated intra-abdominal and urinary tract infections. It was hoped that the newly approved combination would prove safer and more effective than previously developed agents that showed in vitro activity against CRE, such as colistin, gentamicin, and tigecycline, the researchers noted.

They described CRE-infected patients treated with ceftazidime-avibactam (median, 14 days; range, 4-71 days) between April 2015 and February 2016. The average age of the patients was 64 years (range 26-78 years), and 57% were men. Infections included ventilator or health care–associated pneumonia, primary bacteremia, intra-abdominal infection, skin and soft tissue infections, pyelonephritis, mediastinitis, subdural empyema/ventriculitis, and purulent tracheobronchitis. All the CRE isolates were susceptible to ceftazidime-avibactam at baseline. In all, 70% of patients received ceftazidime-avibactam as monotherapy, while 30% received it in combination with intravenous or inhaled gentamicin, intravenous or intrathecal colistin, or tigecycline (Clin Infect Dis. 2016 Sep 13. doi: 10.1093/cid/ciw636 ).

A total of 28 (76%) patients were alive at 30 days and 62% were alive at 90 days, the investigators said. They calculated a 59% rate of clinical success, defined as absence of recurrence within 30 days of onset, resolution of signs and symptoms, and sterilization of site-specific cultures within 7 days of treatment. Combination therapy did not improve the chances of clinical success, they noted. Among the 15 clinical failures, 9 patients died, 4 developed recurrent CRE infections, and 2 did not clinically improve. Clinical success was less likely when patients needed continuous renal replacement therapy (17% vs. 68% for other patients; P = .03) or had higher Sequential Organ Failure Assessment (SOFA) scores (average, 5.2 in clinical successes vs. 8.8 in clinical failures; P = .047). In addition, 10% of patients developed acute kidney injury within 7 days of starting treatment, which was “considerably lower than the approximately 30% rate we previously reported with carbapenem-colistin or aminoglycoside-based combinations,” the investigators said.

The sample size was too small to definitively answer questions about whether combination regimens can overcome resistance, improve outcomes, or effectively treat specific types of CRE infection, the researchers noted. “Nevertheless, we can conclude that ceftazidime-avibactam offers an important advance in the treatment of CRE infections,” they wrote. “The development of resistance after as few as 10 days of therapy is troubling, and treatment failures and deaths in a significant minority of patients highlight the need for more agents with activity against CRE.”

The University of Pittsburgh Medical Center and the National Institutes of Health provided funding. One coauthor disclosed ties to Meiji, Shionogi, Tetraphase, Achaogen, Merck, and The Medicines Company. The other authors had no disclosures.


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