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Spiral gradient endpoint susceptibility testing: a fresh look at a neglected technique
Rocky Pong1, Maureen V Boost, Margaret M O'Donoghue
1Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR.
The Journal of Antimicrobial Chemotherapy
|July 3, 2010
Summary
The spiral gradient endpoint (SGE) technique offers a reproducible and cost-effective method for determining minimum inhibitory concentrations (MICs) in fastidious organisms. This validated approach provides accurate results comparable to standard methods, making it suitable for various laboratory settings.
Area of Science:
- Clinical Microbiology
- Antimicrobial Susceptibility Testing
Background:
- Rising antibiotic resistance necessitates accurate MIC determination.
- Traditional methods can be costly and time-consuming.
- The spiral gradient endpoint (SGE) technique is a potentially low-cost alternative.
Purpose of the Study:
- To re-evaluate and optimize the SGE technique for MIC determination.
- To assess the SGE method's performance with fastidious bacterial organisms.
- To compare SGE results with established reference methods.
Main Methods:
- Optimized SGE for fastidious organisms using *Haemophilus influenzae*.
- Assessed intra- and inter-batch reproducibility for *H. influenzae*, *Streptococcus pneumoniae*, *Moraxella catarrhalis*, and *Neisseria gonorrhoeae*.
- Compared SGE-determined MICs against clinical isolates with reference method results.
Main Results:
- Achieved excellent reproducibility for all tested organisms (SD 0.10-0.337; CV 8.59%-18.66%).
- Demonstrated excellent correlation between SGE and reference MICs (0.908-0.930).
- Showed no significant differences in resistance category distribution compared to reference methods.
Conclusions:
- The SGE technique is a reproducible and reliable method for MIC determination in fastidious organisms.
- SGE offers a rapid, flexible, and cost-effective alternative to standard methods.
- This technique is particularly suitable for smaller laboratories and developing countries.
