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Quality control ranges for cefoperazone 30 μg disks for Staphylococcus aureus ATCC® 25923 and Escherichia coli ATCC®
Andrea T Feßler1, John Turnidge2, Stefan Schwarz1
1Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany.
Abstract:
The third generation cephalosporin cefoperazone is commonly used for bovine mastitis therapy. So far, the cefoperazone susceptibility testing using 30 μg disks was hampered by the lack of quality control (QC) ranges and the respective interpretive criteria. The aim of this study was to develop CLSI-approved QC ranges for Staphylococcus aureus ATCC(®) 25923 and Escherichia coli ATCC(®) 25922. An interlaboratory trial including eight laboratories was conducted. Each laboratory tested both QC reference strains ten times using two lots of cefoperazone 30 μg disks and three lots of Mueller-Hinton agar. The results were analysed by using the published statistical analysis method. Based on the data, zone diameters of 23-34 mm and 24-33 mm were established as QC ranges for the 30 μg disk and S. aureus ATCC(®) 25923 and E. coli ATCC(®) 25922, respectively. These new QC ranges have been recently approved by the Clinical and Laboratory Standards Institute and will help diagnostic laboratories to validate their cefoperazone testing results using 30 μg disks.
Insights
New quality control (QC) ranges for cefoperazone susceptibility testing in veterinary diagnostics have been established. These ranges aid laboratories in validating cefoperazone disk diffusion tests for bovine mastitis therapy.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Susceptibility Testing
- Clinical Pathology
Background:
- Cefoperazone, a third-generation cephalosporin, is vital for treating bovine mastitis.
- Current cefoperazone susceptibility testing using 30 μg disks lacks established quality control (QC) ranges and interpretive criteria.
- This deficiency hinders accurate diagnostic validation for veterinary use.
Purpose of the Study:
- To develop and establish Clinical and Laboratory Standards Institute (CLSI)-approved quality control (QC) ranges for cefoperazone 30 μg disk diffusion tests.
- To ensure reliable and reproducible antimicrobial susceptibility testing (AST) for cefoperazone in diagnostic laboratories.
- To support accurate therapeutic decisions in bovine mastitis treatment.
Main Methods:
- An interlaboratory trial involving eight laboratories was conducted to assess cefoperazone disk diffusion.
- Standardized testing procedures were used with reference strains *Staphylococcus aureus* ATCC® 25923 and *Escherichia coli* ATCC® 25922.
- Multiple lots of cefoperazone 30 μg disks and Mueller-Hinton agar were utilized, with each strain tested ten times per laboratory.
Main Results:
- The study established new QC zone diameter ranges for cefoperazone 30 μg disks against *S. aureus* ATCC® 25923 (23-34 mm) and *E. coli* ATCC® 25922 (24-33 mm).
- These ranges were derived from rigorous analysis of data collected across multiple laboratories and testing conditions.
- The developed QC ranges have received approval from the Clinical and Laboratory Standards Institute (CLSI).
Conclusions:
- The newly approved CLSI QC ranges provide essential criteria for validating cefoperazone 30 μg disk diffusion tests.
- Implementation of these QC ranges will enhance the accuracy and reliability of cefoperazone susceptibility testing in veterinary diagnostics.
- This advancement will improve the effective management of bovine mastitis through validated antimicrobial susceptibility data.
