Susceptibility of dermatophytic fungi to commonly used disinfectants

Abstract

This study aimed evaluate the antidermatophytic activity of three commercial disinfectants commonly used for environmental control of microorganisms in veterinary medicine. Sodium hypochlorite at 40 μL/mL, chloro-phenol derived at 30 μL/mL and chlorhexidine digluconate at 66.7 μL/mL were tested against 14 strains of dermatophytes, identified as Microsporum canis (n: 3) and Microsporum gypseum (n: 11). The tests was performed in accordance with guidelines of the Clinical and Laboratory Standards Institute (CLSI), documents M38-A2 and M51-A, adapted to disinfectants. In the microdilution broth test, chlorhexidine digluconate had MIC values (Minimum Inhibitory Concentration) of 4.16 μL/mL and MCF (Minimum Fungicidal Concentration) from 4.16 to 8.33 μL/mL, while chloro-phenol derived obtained MIC and MCF of 1.87 μL/mL, and both disinfectants had fungicidal activity at concentrations below the recommended. Sodium hypochlorite obtained MIC from 10 to 80 μL/mL and MFC of 40 to 80 μL/mL, requiring at most isolates twice the recommended concentration to achieve same activity. In the disc diffusion test, the mean inhibition zones for chlorhexidine digluconate was 10.53 mm, for chloro-phenol of 9.9 mm and for sodium hypochlorite was 6.2 mm. Chlorhexidine digluconate and chloro-phenol presented a significant reduction in the growth of dermatophytes, while sodium hypochlorite in concentration recommended showed a low antifungal activity against tested isolates. ResumoO objetivo do estudo foi avaliar a atividade antidermatofítica de três desinfetantes comerciais frequentemente utilizados no controle ambiental de micro-organismos em medicina veterinária. Hipoclorito de sódio a 40 μL/mL, derivado de clorofenol a 30 μL/mL e digluconato de clorexidine a 66.7 μL/mL foram testados contra 14 cepas de dermatófitos, identificados como Microsporum canis (n:3) e Microsporum gypseum (n: 11). Foram utilizadas as diretrizes do Clinical and Laboratory Standard Institute (CLSI), documentos M38-A2 e M51-A, com adaptações para desinfetantes. Na microdiluição em caldo, digluconato de clorexidine apresentou valores de CIM (Concentração Inibitória Mínima) de 4.16 μL/mL e CFM (Concentração Fungicida Mínima) entre 4.16 a 8.33 μL/mL; derivado de clorofenol obteve CIM e CFM de 1.87 μL/mL, demonstrando que ambos os desinfetantes apresentaram atividade fungicida em concentrações inferiores às recomendadas. O hipoclorito de sódio demonstrou CIM entre 10 a 80 μL/mL e CFM de 40 a 80 μL/mL, requerendo duas vezes a concentração recomendada pelo fabricante para obter atividade fungicida frente a maioria dos isolados fúngicos testados. No teste de disco-difusão, a média das zonas de inibição do digluconato de clorexidine foi de 10.53 mm; do derivado clorofenol 9.9 mm e do hipoclorito de sódio 6.2 mm. O digluconato de clorexidine e o derivado cloro-fenol apresentaram redução significante no crescimento dos dermatófitos testados, enquanto o hipoclorito de sódio, na concentração recomendada, demonstrou baixa atividade antifúngica contra os dermatófitos testados.P...

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