In vitro activity of conventional antifungal drugs and natural essences against the yeast-like alga Prototheca

R eceiv ed 13 No vember 2007; returned 29 December 2007; revised 8 F ebruary 2008; accepted 20 F ebruary 2008Ba ckgr ound : T wo outbr eaks of mas titis due to the y eas t-lik e alga Pr ototheca zopÞi recently occurr edin dairy herds in Lombardia (Italy) inv olving 180 and 150 lacta ting co ws, respectiv ely .Objectiv es : T o determine the in vitr o susceptibility of Pr ototheca isola tes to conv entional antifungalagents and to essential oils.Methods : T w enty P . zopÞi isola ted from milk during these outbr eaks, six P . zopÞi isola ted from freshw a ter and two Pr ototheca sp. refer ence s trains w e re submitted to antifungal susceptibility tes ting bybr oth micr odilution assa y follo wing the CLSI guidelines for y eas ts.R esults : The tes ted isola tes w e re sho wn to be resis tant to suconazole and caspofungin. A wide rangeof v oriconazole MICs w a s observ ed. In contr as t, amphotericin B, itra conazole and posa conazoleappear ed a ctiv e with MICs ! 1 mg/L. Bergamot and tea tree oils seemed to e xert an inter es ting a ctivityagains t this y eas t-lik e alga.C onclusions : DifÞculties in trea ting animals with conv entional drugs and the potent in vitr o a ctivity ofessential oils demons tra ted her e raise the inter es t in further inv es tiga tions on the ther apeutic use ofthese non-conv entional na tur al pr oducts.Ke ywords: bo vine mas titis, tea tree oil, bergamot oil