Evaluation of a colorimetric method for detecting amphotericin B-resistant Candida isolates

Area of Science:

• Mycology
• Antimicrobial Resistance
• Clinical Microbiology

Background:

• Detecting amphotericin B resistance in Candida is crucial for effective antifungal treatment.
• Antibiotic Medium 3 (AM3) aids in detecting resistant isolates compared to RPMI 1640.
• A simpler method for detecting resistance is desirable.

Purpose of the Study:

• To evaluate the utility of alamarBlue as a colorimetric indicator to simplify the detection of amphotericin B resistance in Candida.
• To assess if alamarBlue improves resistance detection when used with RPMI 1640 or AM3.

Main Methods:

• Microdilution method (M27-A) was employed for antifungal susceptibility testing.
• Tests were performed using RPMI 1640 and Antibiotic Medium 3 as growth media.
• AlamarBlue was used as a colorimetric indicator in combination with both media.

Main Results:

• AlamarBlue did not enhance the detection of resistant Candida isolates when combined with RPMI 1640.
• When used with AM3, alamarBlue increased the Minimum Inhibitory Concentration (MIC) of susceptible isolates, reducing discrimination.
• The overall ability to detect amphotericin B resistance was not improved by alamarBlue.

Conclusions:

• AlamarBlue is not a suitable indicator for improving the detection of amphotericin B resistance in Candida using standard microdilution methods.
• Current methods using AM3 remain more effective for identifying resistant isolates than those incorporating alamarBlue.
• Further research may be needed to explore alternative methods for simplified resistance detection.