CLSI broth microdilution method for testing susceptibility of Malasseziapachydermatis to thiabendazole

Abstract

Thiabendazole, classified as antiparasitic and also used as an antifungal drug, can be found as otological solution indicated for treatment of parasitic and fungal external otitis in small animals. Malassezia pachydermatis is a yeast recognized as a normal inhabitant on the skin and mucous membranes of dogs and cats. However, it is considered an opportunistic agent that causes external otitis and dermatitis in these animals. The aim of this study was to evaluate the in vitro effect of thiabendazole against 51 isolates of M. pachydermatis using the CLSI Broth Microdilution method that has been adapted for this yeast species (NCCLS, 2002). Based on this test, the Minimum Inhibitory Concentrations (MIC) of thiabendazol was calculated. Subsequently, the susceptibility of each isolate against this antifungal was determined. It was observed that the MIC of thiabendazole against M. pachydermatis ranged from 0.03 to > 4 µg/mL. A total of 13.7% of the isolates were found to be resistant, 47.1% were intermediate and 39.2% were sensitive to the drug. The rate of resistance of the yeasts against thiabendazole was similar to the results previously obtained with other antifungals, while the adapted broth microdilution technique used in this study proved to be efficient.

Evaluation of the antifungal susceptibility of Malassezia pachydermatis to clotrimazole, miconazole and thiabendazole using a modified CLSI M27‐A3 microdilution method

“…In clinical practice, recurrent Malassezia otitis is commonly reported, and failure of treatments to control yeast overgrowth is often attributed to ‘resistance’ to the antifungal employed, with a consequent switch to another principle. This practice may be influenced by published studies that reported isolates of M. pachydermatis resistant to various azoles 6–8 . Resistance is defined as the reduction in effectiveness of an antimicrobial drug in curing an infectious disease 9 .…”

“…Previously published data regarding the in vitro antifungal susceptibility of M. pachydermatis using various types of assays are conflicting. Using a disk diffusion test, total resistance to TBD was reported, 18 while in another study, most isolates of the yeast were found to be susceptible to this agent 8 . Disk diffusion assays of CTZ and MCZ also yielded conflicting results, with some authors reporting resistant isolates 6,7 and other studies finding that these drugs had substantial activity 19,20 .…”

Anti-candidal effect of endophytic fungi isolated from Calotropis gigantea

“…MIC of the plant and fungal extracts along with the standard drug Fluconazole was determined by NCCLS Broth Microdilution (BM) method on sterile microtiter plate with 96 flat bottomed (Nascente et al, 2009) with slight modifications. The C. albicans isolate was suspended in saline solution with the turbidity adjusted to level 1 of the McFarland scale.…”

Trimethylchitosan-Capped Silver Nanoparticles with Positive Surface Charge: Their Catalytic Activity and Antibacterial Spectrum Including Multidrug-Resistant Strains of <em>Acinetobacter baumannii</em>

“…, and seven clinically isolated MDR strains of A. baumannii (AB293) were used for this study. We followed the Clinical and Laboratory Standards Institute (CLSI) standardized method for broth microdilution with some modifications [46]. Briefly, bacteria were subcultured on Luria-Bertani (LB) agar plates (Lab M, UK) overnight and grown in Müller-Hinton (MH) broth (Lab M, UK) for 24 h. The turbidity of the bacterial suspension was adjusted to level 0.5 of the McFarland scale.…”