Acta Tropica 81 (2002) 101–110
Review article
Candida commensalism and virulence: the evolution of
phenotypic plasticity
David R. Soll *
Department of Biological Sciences, Uniersity of Iowa, Iowa City, IA 52242, USA
Received 13 August 2001; received in revised form 5 October 2001; accepted 5 October 2001
Abstract
Candida albicans and related species live as benign commensals in one or more body locations in a majority of
healthy individuals. As opportunistic pathogens, they are poised to overgrow cavities and penetrate tissue in response
to an alteration in host physiology that presumably compromises the immune functions that normally suppress their
growth. There is little evidence of the emergence of successful drug-resistant or hypervirulent strains that predominate
in either the commensal or disease states. It appears more likely that all strains possess similar capabilities for rapid
adaptation to drug therapy, the immune response and changes in body location and in host physiology. It is suggested
that the mechanisms for rapid adaptation lie in the developmental programs of the bud-hypha transition and high
frequency phenotypic switching, and in the modulation of the expression of virulence genes in response to
environmental cues. © 2002 Published by Elsevier Science B.V.
Keywords: Candida albicans ; Drug therapy; Virulence genes
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1. Introduction
When we consider the emergence of new dis-
eases in human populations, we usually envision
viruses that have entered populations as a result
of abnormal interactions with animal hosts, bacte-
ria that have become resistant to antibiotics due
to the unbridled use of these drugs in our over-
medicated population, or hypervirulent strains
that have emerged due to rapid microevolution.
Because these concepts have borne true in the case
of viruses and prokaryotic pathogens, they have
been incorporated into our interpretations of fun-
gal pathogenesis, and our expectations concerning
the emergence of drug resistant and hypervirulent
strains. However, when epidemiological tools
have been used to examine species and strain
specialization in the fungi, and in Candida albi -
cans in particular, the results have not revealed
such specialization. There has been no demonstra-
Presented at the 4th Annual Conference on New and
Re-Emerging Infectious Diseases in the College of Veterinary
Medicine at the University of Illinois at Urbana-Champaign.
* Tel.: +1-319-335-1117; fax: +1-319-335-2772.
E-mail address: david-soll@uiowa.edu (D.R. Soll).
0001-706X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII:S0001-706X(01)00200-5