Quality control limits for ampicillin, carbenicillin, mezlocillin, and piperacillin disk diffusion susceptibility tests: a collaborative study

Self Cite

For in vitro susceptibility tests with cefoperazone and sulbactam (a I-lactamase inhibitor), 75/30-,ig disks may be used with the interpretive zone size breakpoints that are currently used for 75-,ug cefoperazone disks. For dilution tests, a 2:1 ratio of cefoperazone to sulbactam is recommended. For quality control purposes, MIC limits that are used to monitor cefoperazone tests were also applied to tests with the combination of drugs. For gram-negative control strains, zone size limits were calculated to be 1 mm smaller than those used for cefoperazone disks. To monitor the sulbactam portion of the combination, Acinetobacter calkoaceticus subsp. anitratus ATCC 43498 was selected; zones with 75/30-,ig disks were 26 to 32 mm in diameter, and broth microdilution MICs ranged from 1.0/0.5 to 8.0/4.0 ,ug/ml. With cefoperazone alone, MICs for Acinetobacter calcoaceticus subsp. anitratus were 16 to 64 ,ug/ml and zones ranged from 14 to 18 mm in diameter. For anaerobic dilution tests, only Bacteroides thetaiotaomicron ATCC 29741 is recommended for cefoperazonesulbactam; MICs ranged from 8.0/4.0 to 32/16 ,ig/ml. Although cefoperazone is relatively stable to staphylococcal 1-lactamases and to most chromosomally mediated

Section: Methodsmentioning

confidence: 99%

Criteria for disk susceptibility tests and quality control guidelines for the cefoperazone-sulbactam combination

Barry¹,

Jones²

1988

Self Cite

“…SB). From this curve, the mean zone diameter value of the S. faecalis population, 19 4. Histograms of zone diameter values obtained from routine antibiotic susceptibility tests of 140 strains of E. coli (A) and 46 strains of P. aeruginosa (B) with 30-,ug gentamicin disks.…”

Section: Resultsmentioning

confidence: 99%

“…The underlying regression analysis is based on studies of a large number of strains and is therefore usually performed only by reference laboratories (1,14). From the known variation in disk diffusion results among different laboratories, it is apparent that the zone limits set might not represent correct MICs in individual laboratories (4,19,23). To minimize the resulting errors in interpretations, the I group of susceptibility has been transformed into an indeterminate group and considered a buffer zone (27,32).…”

mentioning

confidence: 99%

Analysis of a single reference strain for determination of gentamicin regression line constants and inhibition zone diameter breakpoints in quality control of disk diffusion antibiotic susceptibility testing

Kronvall¹

1982

“…Analysis of QC reference ranges. Inhibition zone diameter ranges for each QC reference strain were determined using the Gavan statistic (30) and RangeFinder (28) statistical program. RangeFinder also determines if the central tendencies (mean, median, and mode) of data sets obtained from individual laboratories are statistical outliers (28) and should be excluded from analysis.…”

mentioning

confidence: 99%

Development of Broth Microdilution MIC and Disk Diffusion Antimicrobial Susceptibility Test Quality Control Ranges for the Combination of Cefepime and the Novel β-Lactamase Inhibitor Enmetazobactam

Belley¹,

Huband

Fedler

et al. 2019

Third-generation cephalosporin resistance among Enterobacteriaceae, mediated by the spread of extended-spectrum ␤-lactamases (ESBLs), is a very serious medical concern with limited therapeutic options. Enmetazobactam (formerly AAI101) is a novel penicillanic sulfone ␤-lactamase inhibitor active against a wide range of ESBLs. The combination of enmetazobactam and cefepime has entered phase 3 development in patients with complicated urinary tract infections. Using the Clinical and Laboratory Standards Institute (CLSI) M23 tier 2 study design, broth microdilution MIC and disk diffusion quality control (QC) ranges were determined for cefepime-enmetazobactam. Enmetazobactam was tested at a fixed concentration of 8 g/ml in the MIC assay, and a cefepime-enmetazobactam disk mass of 30/20 g was used in the disk diffusion assay. Escherichia coli ATCC 25922, E. coli ATCC 35218, E. coli NCTC 13353, Klebsiella pneumoniae ATCC 700603, and Pseudomonas aeruginosa ATCC 27853 were chosen as reference strains. The CTX-M-15-producing E. coli NCTC 13353 isolate is recommended for routine testing to control for inhibition of ESBL activity by enmetazobactam. Broth microdilution MIC QC ranges spanned 3 to 4 doubling dilutions and contained 99.6% to 100.0% of obtained MIC values for the five reference strains. Disk diffusion yielded inhibition zone diameter QC ranges that spanned 7 mm and encompassed 97.1% to 100.0% of the obtained values. Quality control ranges were approved by the CLSI in 2017 (broth microdilution MIC) and 2019 (disk diffusion). The established QC ranges will ensure that appropriate assay performance criteria are attained using CLSI reference methodology when determining the susceptibility of clinical isolates to cefepime-enmetazobactam.