| Research Abstract |
Paecilomyces lilacinus(Thom)Samson occurs worldwide as a saprophytes in soils and has been reported to cause opportunistic fungal infections in humans as well as animals. Recently infections due to the species have been reported with increasing frequency in conpromized hosts. We have reported on relatively lower molecular weight peptide toxins, called paecilotoxins from P. lilacinus. Although, there had been no available study providing evidence that low molecular weight toxic substances contribute to fungal infections, we confirmed and reported the active role of paecilotoxins as etiological agents in a fungal infections. Furthermore, our present survey on the toxin productivity of P. lilacinus collected from various culture collections revealed that more than 95 % of P. lilacinus strains were toxin producers regardless of their origins. These data suggested that all P. lilacinus strains are potentially hazardous to humans as well as animals.
Paecilotoxins showed antifungal as well as
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antibacterial activity. Most of fungi tested were inhibited at concentrations of 3 to 25 ug/mi. As expected, all strains of P. lilacinus were more resistant and thier MIC values were above 500 ug/ml. These results supported our hypothesis that susceptibility of Paecilomyces species to the toxins is correlated with toxin production. To determine whether these susceptibility profiles of P. lilacinus are species-specific phenomena, we tested ten species of Paecilomyces, Among them, P. isarioides, P. inflatus and P. variotii were sensitive. Although the MIC values of P. fumoso-roseus, P. farinosus, P. elepans and P. carneus varied depending on the strain, these species were generally considered to belong to a senstive group. On the other hand, all strains of P. lilacinus werc resistant. Four strains of P. marguandii and one strain of P. javanicus were also resistant to the toxins. As for the high resistance of P. margunadii species, it may be explained by the fact both species are closely related. Profiles of fragmentation pattems of mitochondrial DNA with EcoRl or Hind III arealso compared and characteristic patterns in each species are observed. However, our preliminary studies could not confirm the production of paecilotoxin with the present four strains. Now further detail studies on optimization of incubation conditions for toxin production are progress. We also check the paccilotoxin production by P. javanicus strain, since it was also resistant to the toxins. However, our studies could not confirm the production of the toxins in this strain, but production of other active substance(s)is suggested. Detail characterization studies on the active principles(s)in P. javanicus strain are of interest, since P. javanicus is also reported repeatedly as a pathogen to humans. In the searching for new antibiotics, an enrichment method based on the mechanisms of self-resistance of antibiotic producing microorganisms, has been employed for the selecctive isolation of similar antibiotic producers. Furthermore, our studies suggested that P. litacinus has an alkalophilic or alkaline resistant nature in toxin production as well as in growth. Based on this species-specific resistant character of P. lilacinus to the toxins, a new selective isolation method of P. lilacinus was considered. By using this system, 25 strains of Paecilomyces species were selectively isolated. Although all strains were considered to belong to P. lilacinus species, it was found that they are divided into two groups on the basis of the formation of a yellowish diffusible pigment on potato dextrose agar. Of interest was that only the non-pigmented group, one third of the isolates, were paecilotoxin producers, and no paecilotoxin activity was observed in the pigmented group. Since the chemical nature of the yellowish pigment was interested from the viewpoint of chemotaxonomy, purification of the pigment was conducted and the yellow pigment was fina Less
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