Atypical forms of Cryptococcus neoformans in CSF of an AIDS patient

Abstract

The microscopic recognition of typical rounded capsulated yeasts in centrifuged cerebrospinal fluid (CSF), stained with India ink, is a common, rapid and effective method for the diagnosis of cryptococcal meningitis among AIDS patients. The presence of atypical forms of Cryptococcus neoformans var. neoformans in samples of CSF of an AIDS patient with cryptococcosis treated at the University Hospital of Infectious Disease is presented. The India ink microscopy of three consecutive CSF samples revealed capsulated yeast with India ink particles in the deteriorated capsules and capsulated pseudohyophae. Clinically, the patient showed a subacute meningoencephalitis, with a clinical picture not particularly different from those commonly observed in patients with AIDS-associated cryptococcosis treated in our hospital. In all cases, the culture of the CSF showed colonies of C. neoformans with typical macro and micromorphology, and the in vitro susceptibility tests to amphotericin B, fluocitosine, itraconazole and fluconazole showed MIC values into the limits of sensitivity. The presence of atypical forms of C. neoformans, considered as an atypical finding, could be the consequence of an adaptive phenomenon of this fungal species to an impaired immunological status present in the host.

Unusual morphologies of Cryptococcus spp. in tissue specimens: report of 10 cases

“…Other reports describe the identification of variant forms having pseudohyphae 2,19 , germ-tube like structures and hyphae-forming structures 6 , all identified in an India ink preparation of CSF. In a review of prior necropsy specimens, a case was discovered in which germ tubes and hyphae were observed in brain tissues 15 .…”

“…In 1971, a murine model study demonstrated hyphae-formation in 11 strains of this yeast 21,22 . Interestingly, BAVA et al 2 concluded that the pseudohyphae should be considered a virulence factor and that great immunological deficit and further clinical evolution will better enable the fungal cells to produce atypical forms instead of the conventional yeast forms. In retrospect, reported that the hyphal forms represented attempts of Cryptococcus to produce its sexual teleomorph, F. neoformans.…”

Variability of Phenotypic Traits in Cryptococcus Varieties and Species and the Resulting Implications for Pathogenesis

“…Although C. neoformans encounters low glucose conditions in the CNS, India ink preparations of spinal fluid from infected patients usually show mostly yeast forms and no hyphal forms. However, occasional reports of abnormal forms can be found and may be under-reported [77–79]. This suggests that suppression of filamentous growth may be required for growth in the host niche similar to dimorphic fungi [80].…”

Middle cerebral artery territory infarct due to Cryptococcus infectionstitle

“…The presence of yeasts of variable sizes with a thick capsule and the presence of narrow based budding is virtually diagnostic of cryptococci on microscopic examination. However, cryptococci may present with capsule deficient forms and may have variable morphology making the diagnosis challenging in some cases. Therefore, in all the cases of suspected cryptococcal meningitis (CM) or stroke, antigen testing and CSF cultures are recommended.…”