By Ethan Covey

A medication-use evaluation of ceftolozane-tazobactam (Zerbaxa, Merck) and ceftazidime-avibactam (Avycaz, AbbVie) in a Florida Veterans Affairs hospital found a significant reduction in susceptibility for Pseudomonas aeruginosa over time.

The findings demonstrate the importance of evaluating antibiotic use patterns in hospitals, and how such data can allow for better informed decisions regarding antibiotic stewardship programs, according to a presentation at the MAD-ID (Making a Difference in Infectious Diseases) virtual 2021 meeting (poster A17).

“This evaluation was definitely important to our specific facility in that it allowed us to have a more concrete idea of our local susceptibilities, especially regarding MDR Pseudomonas aeruginosa [MDR-PSA], which in turn has led us to make changes to our local practices using these agents,” said Melissa Lore, PharmD, a PGY-2 infectious diseases pharmacy resident at James A. Haley Veterans Hospital, in Tampa, Fla.

The study evaluated ceftolozane-tazobactam and ceftazidime-avibactam use and outcomes, as well as the frequency of susceptibility testing and rates of MDR-PSA and carbapenem-resistant Enterobacterales. Adult patients 18 years of age and older received at least one dose of ceftolozane-tazobactam or ceftazidime-avibactam from December 2014 to June 2020.

A total of 46 unique patients were included, resulting in 95 antibiotic courses. Of these, 26 antibiotic courses had ceftolozane-tazobactam and ceftazidime-avibactam susceptibilities tested; of these, only four had susceptibilities known prior to antibiotic use. Thirteen PSA isolates were tested for susceptibility to ceftazidime-avibactam and only 54% were susceptible. Of the 11 PSA isolates tested for ceftolozane-tazobactam susceptibility, 82% were susceptible. And susceptibility to PSA declined over time, with only 40% of ceftazidime-avibactam and 50% of ceftolozane-tazobactam showing susceptibility in 2020.

To improve the use of these agents, it was decided that the facility will develop and implement an MDR gram-negative treatment algorithm and criteria for use, as well as a susceptibility testing protocol.

“This project speaks to the importance of facilities knowing their own local susceptibilities,” Dr. Lore said. “It is not necessarily safe to assume that just because an antibiotic is newer and/or not used as frequently, it will be susceptible. Bacteria have proven time and time again how smart they are and will find a way to develop resistance.

“On a larger scale,” Dr. Lore added, “our project continues to show how important antimicrobial stewardship is, even with newer antimicrobial agents, in helping to combat the ever-increasing challenge of treatment-resistant bacteria.”