The evolutionary success of pathogenic microorganisms is determined by their ability to deal with environmental stress and rapidly adapt to the changing conditions experienced within the host. Adaptation occurs as a result of a mutation which generates a phenotypic trait which aids the organism in surviving within it’s environment. Subsequently, natural selection ensues the small proportion of cells possessing this mutation become predominant in the population in ashort time frame in a process termed microevolution. The mutations on which selection can act arise from environmental damage or errors occurring during DNA replication. Mutations can be pre-existing in the microbe’s genome, or can be rapidly acquired in response to the host environment in a process termed adaptive evolution. Adaptive evolution is greatly enhanced by an increased mutation rate, which provides higher genetic diversity within a population on which selection can act.Strains which exhibit an elevated mutation rate, often 100-200-fold that of wildtype, are termed mutators. A mutator phenotype is advantageous in rapidly changing environmental or stressful conditions. The objective of this study was to investigate the role mutation rate plays in microevolution and the emergence of resistance to antifungal drugs.