Biotyping of Penicillium marneffei reveals concentration-dependent growth inhibition by galactose

Thirty-two isolates of the dimorphic fungus Penicillium marneffei were stud ied for their biochemical properties. All isolates possessed the enzyme ure ase and were inhibited by 500 mg of cycloheximide per liter, No strain ferm ented glucose, and thus no strain fermented any of the other five sugars te sted. All assimilated glucose, maltose, and cellobiose; only one of the iso lates did not assimilate salicin, Totals of 65.6, 84.4, and 71.9% of the is olates assimilated trehalose, xylose, and nitrate, respectively. Twelve str ains possessed the enzyme beta -galactosidase, Overall, 17 different biotyp es were recognized, but no association,vas found between the human immunode ficiency virus status of the patients and the biotype. A novel finding of c oncentration-dependent growth inhibition of P, marneffei by galactose is de scribed. Inhibition of growth occurred at a low concentration of galactose (0.015 to 0.25%) when galactose was the sole carbon source in the medium. M orphological changes of the fungal cells were observed in the presence of g alactose.