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Evaluation of the moving intermediate zone concept for determing susceptibility of pseudomonads to gentamicin by the
Abstract:
The usefulness of the moving intermediate zone concept for improving the performance of the standardized disk agar-diffusion test in measuring susceptibility of the fluorescent group of pseudomonads to gentamicin was studied. For this purpose, a 3-mm moving intermediate zone lying --3 mm and --6 mm below that measured for the quality control microorganism Pseudomonas aeruginosa, ATCC 27853, and a wider moving intermediate zone lying --2 mm and --7 mm below that for the quality control microorganism were investigated. Data from the authors' previous study of the usefulness of using fixed breakpoints and fixed zones for assessing susceptibility of the fluorescent pseudomonads to gentamicin were used for this analysis. The results indicate that both the 3-mm moving intermediate zone and the wider 5-mm moving intermediate zone produced unacceptably high rates of error for testing the susceptibility of the fluorescent group of pseudomonads to gentamicin by the standardized disk agar-diffusion test.
Insights
The moving intermediate zone concept did not improve the disk agar-diffusion test for gentamicin susceptibility in fluorescent pseudomonads. Both tested zone sizes resulted in unacceptable error rates, failing to enhance diagnostic accuracy.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Susceptibility Testing
Background:
- The standardized disk agar-diffusion test is crucial for determining bacterial susceptibility to antibiotics.
- Accurate susceptibility testing is vital for effective antibiotic treatment, especially for challenging pathogens like fluorescent pseudomonads.
- Previous methods using fixed breakpoints and zones showed limitations in assessing gentamicin susceptibility.
Purpose of the Study:
- To evaluate the efficacy of the moving intermediate zone concept in enhancing the standardized disk agar-diffusion test.
- To determine if a 3-mm or a 5-mm moving intermediate zone improves gentamicin susceptibility testing for fluorescent pseudomonads.
- To compare the performance of moving intermediate zones against fixed breakpoints and zones.
Main Methods:
- Investigated a 3-mm moving intermediate zone set at specific distances below the quality control microorganism's zone.
- Examined a wider 5-mm moving intermediate zone using similar reference points.
- Analyzed data from a prior study comparing fixed breakpoints and zones for gentamicin susceptibility.
Main Results:
- Both the 3-mm and the 5-mm moving intermediate zones yielded unacceptably high error rates.
- The moving intermediate zone concept did not improve the accuracy of the disk agar-diffusion test for this specific application.
- The tested modifications failed to provide reliable gentamicin susceptibility data for fluorescent pseudomonads.
Conclusions:
- The moving intermediate zone concept is not suitable for improving gentamicin susceptibility testing of fluorescent pseudomonads using the standardized disk agar-diffusion method.
- Current findings suggest that this approach does not overcome the limitations of previous methods.
- Further research is needed to develop more reliable methods for assessing the susceptibility of these bacteria to gentamicin.