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Antimicrobial Characterization of Advanced Materials for Bioengineering Applications
Published on: August 4, 2018
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Direct susceptibility testing by disk diffusion on clinical samples: a rapid and accurate tool for antibiotic
L Coorevits1, J Boelens, G Claeys
1Ghent University, Ghent, Belgium, liselotte.coorevits@icloud.com.
Summary
Direct susceptibility testing (DST) offers a 24-hour faster alternative to conventional antimicrobial susceptibility testing (AST) for clinical samples. While DST shows high agreement, especially for staphylococci, careful interpretation is advised due to potential discordances with beta-lactam antibiotics.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Accurate antimicrobial susceptibility testing (AST) is crucial for guiding patient treatment.
- Conventional AST requires overnight culture, delaying results.
- Direct susceptibility testing (DST) offers a potentially faster method.
Purpose of the Study:
- To compare the accuracy of direct susceptibility testing (DST) with conventional antimicrobial susceptibility testing (AST).
- To evaluate DST's utility on various clinical samples.
- To assess the time-saving potential of DST in patient management.
Main Methods:
- Disk diffusion method was used for both DST and conventional AST.
- 123 clinical samples were analyzed, including respiratory, urine, and abscess discharges.
- Isolates were identified, and both DST and AST results were interpreted.
Main Results:
- 93.4% total agreement for Gram-negative rods with 11 antibiotics; 100% agreement for staphylococci with 9 antibiotics.
- DST tended to identify more resistant isolates, often due to resistant mutants or additional species.
- Highest discordances were observed for beta-lactam antibiotics like amoxicillin-clavulanate and cefuroxime.
Conclusions:
- DST can shorten time to results by approximately 24 hours, aiding critically ill patients.
- DST is potentially useful when selectively applied and interpreted carefully.
- Communication of DST results should be cautious, with confirmation by conventional AST recommended.
