Amphotericin B and caspofungin resistance in Candida glabrata isolates recovered from a critically ill patient.
BACKGROUND
Consecutive Candida glabrata isolates recovered from a patient in an intensive care unit were resistant to amphotericin B (minimum inhibitory concentration, up to 32 mu g/mL; determined by Etest [AB Biodisk]). Analyses at the national reference laboratory showed that some isolates were also resistant to azoles and caspofungin. In this study, 4 isolates were studied thoroughly using susceptibility assays and a mouse model and to determine clonality.


METHODS
Different broth microdilution tests, Etests, and time-kill studies for antifungals were performed in different media. Three of the 4 isolates were examined in an in vivo experiment, in which mice were challenged intravenously with 1 of 3 isolates and treated daily with amphotericin B, caspofungin, or saline. For the clonality studies, arbitrarily primed polymerase chain reaction (PCR) was performed with the 4 isolates, 8 isolates obtained from nonrelated patients, and a reference strain.


RESULTS
The murine model indicated that 1 isolate was resistant to amphotericin B, 1 had intermediate susceptibility, and 1 was fully susceptible. Two of the 3 isolates were resistant to caspofungin. Microdilution methods did not reliably differentiate between amphotericin B-susceptible and -resistant isolates. All assays identified caspofungin-susceptible and -resistant isolates. Arbitrarily primed PCR showed that the 4 isolates probably were of clonal origin.


CONCLUSIONS
We have documented the emergence of amphotericin B-resistant and caspofungin-resistant C. glabrata isolates during treatment of a critically ill liver transplant recipient. Only the Etest predicted amphotericin B resistance in the isolates. We recommend that important fungal strains recovered from patients who are receiving antifungal therapy should be tested for susceptibility to the antifungal drug used, because resistance can be present initially or may occur during treatment.
Krogh-Madsen
Mikkel
M
Department of Clinical Microbiology, H:S Hvidovre Hospital, Hvidovre, Denmark.
Arendrup
Maiken Cavling
MC
Heslet
Lars
L
Knudsen
Jenny Dahl
JD
D000368:Aged; D000666:Amphotericin B / Q000494:pharmacology*; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D041221:Candida glabrata / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D002177:Candidiasis / Q000188:drug therapy; D000077336:Caspofungin; D016638:Critical Illness; D054714:Echinocandins; D005260:Female; D006801:Humans; D055666:Lipopeptides; D051379:Mice; D008826:Microbial Sensitivity Tests; D010456:Peptides, Cyclic / Q000494:pharmacology*; D016133:Polymerase Chain Reaction
D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D010456:Peptides, Cyclic; D000666:Amphotericin B; D000077336:Caspofungin