The differences in activity among new β-lactam/β-lactamase inhibitor combinations creates challenges for many clinicians and it will become increasingly important for microbiology laboratories to be able to produce meaningful results that will aid in the appropriate choice of these new agents. However, microbiology laboratories have few options available to determine the susceptibility of organisms to these novel antimicrobial agents as few of them are yet available on commercial AST platforms.1 Disk diffusion is the only option for testing some of these new drugs, but disks are often difficult to get. Clinical microbiology laboratories face a dilemma when it comes to providing information about the susceptibility or resistance of bacterial isolates to ceftazidime/avibactam and ceftolozane/tazobactam.
1. Humphries RM, Hindler JA. Emerging Resistance, New Antimicrobial Agents... but No Tests! The Challenge of Antimicrobial Susceptibility Testing in the Current US Regulatory Landscape. Clin Infect Dis. 2016 Jul 1;63(1):83-8.