Assessment of 30/20-Microgram Disk Content versus MIC Results for Ceftazidime-Avibactam Tested against Enterobacteriaceae and Pseudomonas aeruginosa.

We evaluated the correlation between MIC and disk diffusion inhibition zones when testing ceftazidime-avibactam, using the 30/20-μg disk and the disk diffusion and MIC breakpoints established by the U.S. FDA and the Clinical and Laboratory Standards Institute (CLSI). Organisms used included 2 groups of Enterobacteriaceae isolates and 2 groups of Pseudomonas aeruginosa isolates; 1 group of each consisted of randomly selected isolates and the second group consisted of a challenge group from thousands of surveillance isolates with an increased proportion of organisms displaying ceftazidime-avibactam MIC values close to the breakpoints. Broth microdilution, disk diffusion tests, and data analysis were performed according to reference standardized methods. Ceftazidime-avibactam breakpoints of ≤8/4 (susceptible) and ≥16/4 μg/ml (resistant) for MIC and ≥21/≤20 mm for disk diffusion, as established by the U.S. FDA and the CLSI, were applied for Enterobacteriaceae and P. aeruginosa Ceftazidime-avibactam MIC and disk zone (30/20-μg disk) correlation were acceptable when testing Enterobacteriaceae (overall, very major [VM] and major [Ma] error rates of 0.4% and 0.0%, respectively) and nearly so when testing P. aeruginosa (2.3% VM and 2.9% Ma errors). In summary, disk diffusion and broth microdilution testing results demonstrated good categorical agreement for ceftazidime-avibactam against Enterobacteriaceae and P. aeruginosa, using 30/20-μg disks.

Sader HS ，Rhomberg PR ，Huband MD ，Critchley IA ，Stone GG ，Flamm RK ，Jones RN ... -  《-》

Development of EUCAST zone diameter breakpoints and quality control criteria for ceftazidime-avibactam 10-4 μg.

Koeth LM ，Matuschek E ，Kahlmeter G ，Stone G ... -  《-》

Assessment of Ceftazidime-Avibactam 30/20-μg Disk, Etest versus Broth Microdilution Results When Tested against Enterobacterales Clinical Isolates.

Han R ，Yang X ，Yang Y ，Guo Y ，Yin D ，Ding L ，Wu S ，Zhu D ，Hu F ... -  《Microbiology Spectrum》

Evaluation of the Etest and disk diffusion method for detection of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China.

Wang Q ，Zhang F ，Wang Z ，Chen H ，Wang X ，Zhang Y ，Li S ，Wang H ... -  《BMC MICROBIOLOGY》

In Vitro Activity of Ceftazidime-Avibactam against Clinical Isolates of Enterobacteriaceae and Pseudomonas aeruginosa Collected in Asia-Pacific Countries: Results from the INFORM Global Surveillance Program, 2012 to 2015.

The in vitro activities of ceftazidime-avibactam and comparators against 9,149 isolates of Enterobacteriaceae and 2,038 isolates of Pseudomonas aeruginosa collected by 42 medical centers in nine countries in the Asia-Pacific region from 2012 to 2015 were determined as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance program. Antimicrobial susceptibility testing was conducted by Clinical and Laboratory Standards Institute (CLSI) broth microdilution, and isolate subset analysis was performed on the basis of the resistant phenotypes and β-lactamase content. Ceftazidime-avibactam demonstrated potent in vitro activity (MIC, ≤8 μg/ml) against all Enterobacteriaceae tested (99.0% susceptible) and was the most active against isolates that were metallo-β-lactamase (MBL) negative (99.8% susceptible). Against P. aeruginosa, 92.6% of all isolates and 96.1% of MBL-negative isolates were susceptible to ceftazidime-avibactam (MIC, ≤8 μg/ml). The rates of susceptibility to ceftazidime-avibactam ranged from 97.0% (Philippines) to 100% (Hong Kong, South Korea) for Enterobacteriaceae and from 83.1% (Thailand) to 100% (Hong Kong) among P. aeruginosa isolates, with lower susceptibilities being observed in countries where MBLs were more frequently encountered (Philippines, Thailand). Ceftazidime-avibactam inhibited 97.2 to 100% of Enterobacteriaceae isolates, per country, that carried serine β-lactamases, including extended-spectrum β-lactamases, AmpC cephalosporinases, and carbapenemases (KPC, GES, OXA-48-like). It also inhibited 91.3% of P. aeruginosa isolates that were carbapenem nonsusceptible in which no acquired β-lactamase was detected. Among MBL-negative Enterobacteriaceae isolates that were ceftazidime nonsusceptible, meropenem nonsusceptible, colistin resistant, and multidrug resistant, ceftazidime-avibactam inhibited 96.1, 87.7, 100, and 98.8% of isolates, respectively, and among MBL-negative P. aeruginosa isolates that were ceftazidime nonsusceptible, meropenem nonsusceptible, colistin resistant, and multidrug resistant, ceftazidime-avibactam inhibited 79.6, 83.6, 83.3, and 68.2% of isolates, respectively. Overall, clinical isolates of Enterobacteriaceae and P. aeruginosa collected in nine Asia-Pacific countries from 2012 to 2015 were highly susceptible to ceftazidime-avibactam.

Karlowsky JA ，Kazmierczak KM ，Bouchillon SK ，de Jonge BLM ，Stone GG ，Sahm DF ... -  《-》