The best type of inoculum for testing the antifungal drug susceptibility of Microsporum canis: In vivo and in vitro results.
Hyphae, arthroconidia
antifungal susceptibility
arthroconidia
clinical resistance
conidia
dermatophytes
Journal
Mycoses
ISSN: 1439-0507
Titre abrégé: Mycoses
Pays: Germany
ID NLM: 8805008
Informations de publication
Date de publication:
Jul 2020
Jul 2020
Historique:
received:
17
01
2020
revised:
03
04
2020
accepted:
09
04
2020
pubmed:
17
4
2020
medline:
7
2
2021
entrez:
17
4
2020
Statut:
ppublish
Résumé
Data correlating in vitro drug susceptibility of Microsporum canis with clinical outcomes of its infections are lacking as well as the most suitable inoculum and incubation time in broth microdilution assays. Microsporum canis strains were collected from animal hosts that tested positive (Group I; n = 13) and negative (Group II; n = 14) to this pathogen following itraconazole (ITC) therapy. In vitro ITC susceptibility was assessed according to the Clinical Laboratory Standards Institute (CLSI M38-A2) methodology using conidia, hypha-conidia and arthroconidia at 3 and 7 days of incubation in order to assess the most suitable inoculum and incubation time. Successively, ketoconazole (KTC), voriconazole (VRC), terbinafine (TRB), posaconazole (PSZ), fluconazole (FLC) and griseofulvin (GRI) susceptibilities were assessed using the chosen inoculum. The MIC values of ITC after three-day incubation were equal than those recorded after 7-day incubation. Itraconazole MICs were ≤1 μg/mL for strains from Group II and >1 μg/mL for those of Group II only when conidia were used. All strains showed high susceptibility to VRC, POS, TEB and low susceptibility to ITC, KTC, GRI and FLC regardless of the source and incubation time. Results suggest that correlation between the in vitro results and clinical outcome was observed only by incubating conidia for 3 days at 30 ± 2°C. These conditions might be most suitable to assess in vitro susceptibility of M. canis and assist in determining the occurrence of drug resistance and cross-resistance phenomena.
Sections du résumé
BACKGROUND
BACKGROUND
Data correlating in vitro drug susceptibility of Microsporum canis with clinical outcomes of its infections are lacking as well as the most suitable inoculum and incubation time in broth microdilution assays.
OBJECTIVES AND METHODS
OBJECTIVE
Microsporum canis strains were collected from animal hosts that tested positive (Group I; n = 13) and negative (Group II; n = 14) to this pathogen following itraconazole (ITC) therapy. In vitro ITC susceptibility was assessed according to the Clinical Laboratory Standards Institute (CLSI M38-A2) methodology using conidia, hypha-conidia and arthroconidia at 3 and 7 days of incubation in order to assess the most suitable inoculum and incubation time. Successively, ketoconazole (KTC), voriconazole (VRC), terbinafine (TRB), posaconazole (PSZ), fluconazole (FLC) and griseofulvin (GRI) susceptibilities were assessed using the chosen inoculum.
RESULTS
RESULTS
The MIC values of ITC after three-day incubation were equal than those recorded after 7-day incubation. Itraconazole MICs were ≤1 μg/mL for strains from Group II and >1 μg/mL for those of Group II only when conidia were used. All strains showed high susceptibility to VRC, POS, TEB and low susceptibility to ITC, KTC, GRI and FLC regardless of the source and incubation time.
CONCLUSIONS AND CLINICAL IMPORTANCE
CONCLUSIONS
Results suggest that correlation between the in vitro results and clinical outcome was observed only by incubating conidia for 3 days at 30 ± 2°C. These conditions might be most suitable to assess in vitro susceptibility of M. canis and assist in determining the occurrence of drug resistance and cross-resistance phenomena.
Substances chimiques
Antifungal Agents
0
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
711-716Informations de copyright
© 2020 Blackwell Verlag GmbH.
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