Biological consequences of petite mutations in Candida glabrata.
OBJECTIVE
To define the pathogenicity of respiration-deficient mutants of Candida glabrata, which present a reduced susceptibility to azoles, that are easily induced in vitro by exposure to these drugs or to ethidium bromide and that may be selected in vivo in patients receiving fluconazole.


METHODS
Two wild-type isolates of C. glabrata were compared with their respective fluconazole- or ethidium bromide-induced petite mutants, regarding the carbohydrate and protein composition of the cell wall, as well as their surface physical properties, and also their adherence abilities and virulence in mice.


RESULTS
Flow cytometric analysis of cell wall carbohydrates using several fluorescent lectins showed an increased binding of mutant cells to concanavalin A compared with their parent isolates, suggesting a greater availability or an increased amount of glucose-mannose residues at the cell surface in petite mutants. Likewise, some quantitative differences between parent and mutant isolates were shown by SDS-PAGE in protein extracts from blastoconidia. Regarding the surface physical properties, no significant differences were seen in the electrophoretic mobility determined by microelectrophoresis, but the two-phase partitioning method revealed a lower cell surface hydrophobicity for petite mutants. Moreover, mutant cells exhibited significant overexpression of CgEPA1 as revealed by real-time reverse transcription-PCR, but the adherence capacities to Caco-2 cells, a human enterocyte line, were not significantly different. Finally, in agreement with their slower growth, petite mutants were less virulent than parent isolates in a murine model of systemic infection.


CONCLUSIONS
This low virulence in mice suggests that petite mutants could be disregarded clinically although they may arise during fluconazole therapy.
Brun
Sophie
S
Groupe d'Etude des Interactions Hôte-Parasite, UPRES-EA 3142, Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, 4 rue Larrey, 49033 Angers Cedex, France.
Dalle
Frédéric
F
Saulnier
Patrick
P
Renier
Gilles
G
Bonnin
Alain
A
Chabasse
Dominique
D
Bouchara
Jean-Philippe
JP
D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D001921:Brain / Q000382:microbiology; D018938:Caco-2 Cells; D041221:Candida glabrata / Q000235:genetics* / Q000472:pathogenicity; D002177:Candidiasis / Q000382:microbiology*; D002473:Cell Wall / Q000378:metabolism*; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000382:microbiology; D037102:Lectins / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000382:microbiology; D051379:Mice; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014774:Virulence
D005656:Fungal Proteins; D037102:Lectins; C120505:epithelial adhesin 1, Candida glabrata