Molecular Typing of the Cryptococcus neoformans/Cryptococcus gattii Species Complex

Abstract

A large number of molecular typing techniques have been applied over the years to discriminate between individual isolates that had been indistinguishable using conventional techniques and to obtain further insights into the epidemiology and population structure of this species complex. This chapter aims to summarize the diverse typing techniques applied to the Cryptococcus neoformans/C. gattii species complex, to correlate the obtained results, and to describe the global distribution of the major genotypes. The enzymes malate dehydrogenase, alcohol dehydrogenase, phosphoglyceromutase, and glutamate dehydrogenase could separate C. gattii from C. neoformans. Electrophoretic karyotyping was for the first time applied to the C. neoformans/C. gattii species complex to study the genetic diversity between seven cryptococcal strains representing all four serotypes. PCR fingerprinting using the primer (GACA)4 was applied to 110 cryptococcal isolates obtained mainly from Germany and Africa as well as additional globally collected reference strains. The restriction fragment length polymorphism (RFLP) patterns result from the presence of a restriction enzyme cleavage site at one place in the genome in one individual and the absence of that specific site in another individual. Intergenic spacer (IGS) sequence analysis is a powerful tool to delineate the two varieties of C. neoformans and separate the four major molecular types of C. gattii.