Phenotypic and genotypic differentiation of several human and avian isolates of Cryptococcus neoformans.

The Cryptococcus neoformans strains isolated from two human cases could be diagnosed as Cr. neoformans var. neoformans by differentiation on the basis of their characteristics determined by proline, canavanine and EDTA urease tests. The results of the serovar assignment were: for the isolate from the meningoencephalitis patient with lethal outcome, serovar A; for the strain isolated from the osteomyelitis patient with benign course, serovar D. Also, the PCR fingerprinting using primers (GACA)4, (CAC)5 and FM 1 resulted in a clear and reproducible assignment of the Cr. neoformans strains to the varieties neoformans and gattii, respectively, and, in addition, it confirmed the serovar assignment. No statistically confirmed differences in virulence between the osteomyelitis and the meningoencephalitis strain could be established by i.v. testing in mice, nor did the PCR with several primers provide any clues to a genetically determined higher virulence of the meningoencephalitis strain. The different classification as serovars A and D does not allow any conclusions concerning different virulence. It was not possible to retrospectively establish the sources of infection of the two Cr. neoformans infections, but pigeon faeces may well have played a role as a reservoir for one of the illnesses.