A) CRYPTOCOCCUS NEOFORMANS:
Cryptococcus neoformans is a yeast that has become a frequent invader of patients with impaired cell mediated immunity, whereas clinical disease is rare in healthy people. In such patients the yeast often
invades the central nervous system and is particularly frequent in causing meningitis, although
pneumonia is not uncommon. The organism can be recovered from soil throughout the world, thus
differing from the primary pathogens described above which have a restricted geographical location.
Cryptococci will favour nitrogen-rich soil, typically achieved through bird droppings. There are approximately twenty species of cryptococci but onlyC. neoformanscauses disease in humans.
Unusual amongst fungal pathogens is the production of a polysaccharide capsule by C. neoformans. All
cryptococci can produce polysaccharide capsules but, when growing in soil, the capsule is usually not
evident. However, when nitrogen or moisture levels drop, ca…