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Development of EUCAST zone diameter breakpoints and quality control criteria for ceftazidime-avibactam 10-4 µg.
Koeth, L M; Matuschek, E; Kahlmeter, G; Stone, G.
Affiliation
  • Koeth LM; Laboratory Specialists, Inc, 1651 A Crossings Parkway, Westlake, OH, 44145, USA. lkoeth@labspec.org.
  • Matuschek E; EUCAST Development Laboratory, Växjö, Sweden.
  • Kahlmeter G; EUCAST Development Laboratory, Växjö, Sweden.
  • Stone G; Pfizer, Inc, Groton, CT, USA.
Eur J Clin Microbiol Infect Dis ; 37(6): 1047-1053, 2018 Jun.
Article in En | MEDLINE | ID: mdl-29603034
ABSTRACT
Ceftazidime-avibactam disk studies were performed for disk mass selection and for establishing EUCAST quality control ranges and zone diameter breakpoints. The disk mass study included disk diffusion testing with ceftazidime-avibactam 10-4 and 10-6 µg disks and broth microdilution MIC testing for challenge set of 94 Enterobacteriaceae and 45 Pseudomonas aeruginosa. EUCAST SOP 9.0-based QC and MIC-disk correlations studies were followed for development of ceftazidime-avibactam 10-4 µg ranges for Escherichia coli ATCC 25922, P. aeruginosa ATCC 27583, and Klebsiella pneumoniae ATCC 700603 and for zone diameter breakpoint determination. The ceftazidime-avibactam 10-4 and 10-6 µg disks performed similar in comparison to broth microdilution, with zones ≤ 14 mm for all resistant strains. The 10-4 µg disk was selected and used in QC and breakpoint studies. There was minimal variation of ceftazidime-avibactam 10-4 µg QC study results between disks, media, and sites. The QC ranges were within 7 mm for all strains. The zone diameter breakpoint study demonstrated good correlation of MIC and disk results. The established zone diameter breakpoints resulted in false susceptible rates of 1.6 and 4.0% for Enterobacteriaceae and P. aeruginosa. EUCAST selected the ceftazidime-avibactam 10-4 µg disk and established QC ranges for E. coli 25922 of 24-30 mm, P. aeruginosa ATCC 27853 of 21-27 mm, and K. pneumoniae ATCC 700603 of 18-24 mm. The zone diameter breakpoints that correlated best with the MIC breakpoints of susceptible ≤ 8 mg/L and resistant > 8 mg/L were Enterobacteriaceae (S ≥ 13, R < 13 mm) and P. aeruginosa (S ≥ 17, R < 17 mm).
Subject(s)

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Ceftazidime / Enterobacteriaceae / Disk Diffusion Antimicrobial Tests / Azabicyclo Compounds / Anti-Bacterial Agents Limits: Humans Language: En Journal: Eur J Clin Microbiol Infect Dis Journal subject: DOENCAS TRANSMISSIVEIS / MICROBIOLOGIA Year: 2018 Document type: Article Affiliation country: Estados Unidos

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Ceftazidime / Enterobacteriaceae / Disk Diffusion Antimicrobial Tests / Azabicyclo Compounds / Anti-Bacterial Agents Limits: Humans Language: En Journal: Eur J Clin Microbiol Infect Dis Journal subject: DOENCAS TRANSMISSIVEIS / MICROBIOLOGIA Year: 2018 Document type: Article Affiliation country: Estados Unidos