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Showing 2 results for Broth Microdilution
Comparative evaluation of in vitro activity of tigecycline using the disc diffusion method and the VITEK-2 COMPACT in clinical isolates at a tertiary care cancer center
Sujata Lall , Vivek Bhat, Sanjay Biswas, Navin Khattry ,
Volume 18, Issue 4 (7-2024)
Abstract
Background: Tigecycline susceptibility testing and reporting remain enigmatic due to the lack of established guidelines. Disc diffusion, as a method of performing susceptibility testing, is more widely accepted worldwide due to its ease of use. Limited published literature is available from India on the utility of this method, especially in a cancer care setting. Hence, this study was conducted to evaluate the performance characteristics of disc diffusion by comparing its results with those of the VITEK-2 COMPACT, considering the latter as the standard.
Methods: Disc diffusion was performed using Kirby-Bauer’s method on Mueller-Hinton agar with a HiMedia 15 mcg TGC disc, following FDA and EUCAST breakpoints. According to CLSI criteria, disc diffusion breakpoints can be considered acceptable when categorical agreement is ≥ 90%, the very major error is ≤ 1.5%, and the major error is ≤ 3%.
Results: Using Cohen’s kappa coefficient, the kappa value was 0.328, with a p-value of <0.05. The agreement percentage observed was 60.84%. Two strains reported as resistant by VITEK-2 COMPACT were misclassified as sensitive by disc diffusion, resulting in a very major error rate of 0.76%. A major error rate of 9.5% and a minor error rate of 27.7% were noted, as 25 strains reported as susceptible were identified as resistant.
Conclusion: Since poor agreement was observed, exceeding the acceptable performance rate, the disc diffusion method was unacceptable according to CLSI criteria. There is a gap in uniformity and a lack of streamlined, harmonized TST, which might become an alarming cause for concern.
 

Comparison of Vitek 2C antifungal susceptibility testing with broth microdilution testing for Candida species
Sukanya Sudhaharan , Naga Appala Raju Sundarapu, Umabala Pamidimukkala ,
Volume 18, Issue 5 (9-2024)
Abstract
Background: The reference method for antifungal susceptibility testing is broth microdilution according to Clinical and Laboratory Standard Institute (CLSI) guidelines. However, the fully automated system, Vitek 2C system may reduce the workload and observer bias associated with manual broth microdilution. This study aimed to compare the results of YS08 card with the results of the broth microdilution (BMD) method.
Methods: A total of 50 clinical Candida isolates were included in the study. The susceptibility testing was done by Vitek 2C using the YS08 card. Broth microdilution was done according to CLSI guidelines M27M44S-Ed3.
Results: For C. albicans, the categorical agreement was 85.8%, 71.5%, 85.8%, and 100% for fluconazole, voriconazole, caspofungin, and micafungin, respectively. The minor errors (MiE) of 14.2% for fluconazole and caspofungin, 28.5% for voriconazole, were detected in C. albicans. In C. glabrata, the categorical agreement (CA) was 100% for micafungin, voriconazole, but 63.7% for caspofungin. An MiE of 36.3% was detected for caspofungin. C. parapsilosis showed a 100% CA for fluconazole, caspofungin, and micafungin, and 85.8% for voriconazole. There were 14.2% of MiEs for voriconazole. In C. tropicalis, 100 % CA was observed for fluconazole, micafungin, and caspofungin, and 88.9% for voriconazole. Moreover, 11.1% (1/9) of MiEs was observed for voriconazole. In C. auris, there was a 100% CA for caspofungin and micafungin, 77.8% for fluconazole, and 66.7% for amphotericin B. There was a major error of 22.2% for fluconazole and 33.3% for amphotericin B.
Conclusion: The majority of Vitek 2C showed comparable results with the broth microdilution (BMD) method. Only minor errors (MiEs) were observed in the tested Candida species.

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