Am. Brothers et Rd. Wyatt, The antifungal activity of natamycin toward molds isolated from commercially manufactured poultry feed, AVIAN DIS, 44(3), 2000, pp. 490-497
The antifungal activity of natamycin, a polyene antifungal compound, was ev
aluated on molds isolated from commercial poultry feed. The antifungal acti
vity was measured by determination of the minimal inhibitory concentration
(MIC) for natamycin on molds growing on semisolid microbiological medium (p
otato dextrose agar) containing pure natamycin at concentrations ranging fr
om 0 to 200 mg/liter. Natamycin exhibited a high degree of antifungal activ
ity against the 191 isolates of aspergilli used in this study, with average
MIC values ranging from 5.08 to 40.1 mg/liter for Aspergillus fumigatus an
d Aspergillus parasiticus, respectively. Natamycin was also equally effecti
ve in inhibiting the growth of nonaflatoxigenic compared with aflatoxigenic
isolates of Aspergillus flavus and A. parasiticus. Natamycin was also effi
cacious against molds other than aspergilli, with MIC values ranging from 2
.15 to 5.80 mg/liter for Paecilomyces and Rhizopus spp., respectively. Nata
mycin exhibited apparent sporicidal activity against spores of toxigenic st
rains of Fusarium moniliforme and A. parasiticus but not Penicillium rubrum
. This sporicidal activity was evident only when spores were exposed to an
in vitro concentration of natamycin of 25 mg/liter or higher for a period o
f time of at least 12 hr. The growth inhibiting activity of natamycin was m
ore pronounced compared with the sporicidal activity.