Analysis of the susceptibility to ceftazidime/avibactam in German MDR/XDR Pseudomonas aeruginosa comparing different methods.
Int J Antimicrob Agents. 2019 May 06;:
Authors: Schaumburg F, Bletz S, Mellmann A, Becker K, Idelevich EA
Ceftazidime/avibactam (CZA) is a new β-lactam/β-lactamase inhibitor combination with promising properties as avibactam can inhibit a broad range of β-lactamases (e.g. blaKPC, blaOXA-48). The objectives were: (i) to assess the CZA susceptibility rates; (ii) to compare gradient and disk diffusion tests with broth microdilution (BMD) for CZA susceptibility testing and (iii) to study the clonal structure and antimicrobial resistance genes in multidrug resistant (MDR) and extensively drug resistant (XDR) P. aeruginosa. Isolates (n=192) from routine diagnostics (Germany, 2013-2018) were tested by BMD reference method, gradient diffusion test (Etest, bioMérieux and MIC Test Strip, Liofilchem) and disk diffusion test (Mast and Oxoid). All isolates were whole genome sequenced to screen for metallo-β-lactamases and to assess the clonal structure using core genome MLST typing. In total, 64.1% of isolates (n=123) were susceptible to CZA (MIC50 8 mg/L, MIC90 >256 mg/L, range 0.5->256 mg/L). Susceptibility rates were higher in MDR (85.0%) than in XDR (49.1%) P. aeruginosa. Among commercial susceptibility testing methods, Etest showed highest accuracy in comparison to BMD (essential agreement 94.8%, categorical agreement 94.3%). CZA-resistant isolates (n=69) mainly belonged to ST235 (n=29, blaIMP-positive). In conclusion, CZA is a promising treatment option particularly for infections caused by MDR P. aeruginosa. CZA-resistant P. aeruginosa mainly belong to the pandemic ST235 high-risk clone. Etest can be considered as an alternative to BMD.
PMID: 31071465 [PubMed - as supplied by publisher]