Morphological variation in pathogenic strains of Penicillium marneffei.

ABSTRACT

Penicillium marneffei is a dimorphic fungus known to be pathogenic to animals and man. The natural reservoir of this organism was known to be bamboo rats found in South Vietnam, Thailand and China. The first two human infections were reported in 1959 and 1973 from the United States. Up to 1984, five new cases of human penicillosis were reported from Thailand. Since then several more cases have been reported from different parts of the world mainly from the southern part of China. However, there are very limited mycological descriptions of this fungi. In this report, five Thai strains were studied for colonial morphology in comparison with Reference strain PLM 689. Variation in mycelial pigment was observed ranging from yellowish-green to orange with water soluble red pigment produced in every strain which can be seen early from the reverse side. Ultrastructural study by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was compared with that of the reference strain PLM 689. PLM 689 strain had only biverticillate penicilli, but all five strains from Thailand had both monoverticillate and biverticillate penicilli which occasionally appeared on the same branch. The conidia of the Thai isolates were oval in shape and 1.3-2 x 0.7-1.6 microns in size smaller than those of PLM 689 which were 2.5-4 x 2-3 microns. Phialides were also smaller and a little shorter but the number of phialides was similar to those of PLM 689 ranging 4-10 except for one strain which had 3-16 phialides. All Thai strains have stipes smaller and somewhat longer than those of PLM 689.(ABSTRACT TRUNCATED AT 250 WORDS)