382. Virulence in Candida glabrata is Not Attenuated by FKS Mutations but Associated with the Frequency of Cells With Distinct Morphology
Session: Poster Abstract Session: Fungal Disease: Management and Outcomes
Thursday, October 4, 2018
Room: S Poster Hall
Background: Echinocandins are the first-line treatment for C. glabrata, however echinocandin resistance is increasingly reported. Acquired FKS­-mediated echinocandin resistance has been associated with the upregulation of chitin synthesis and attenuated fitness and virulence in C. albicans, however conflicting data are reported in C. glabrata. Here, the influence of FKS mutations on fitness, virulence, morphology, and cell wall chitin was assessed among clinical strains of C. glabrata.

Methods: 3 sets of isogenic paired strains consisting of an index-WT and persistent-FKS mutant (S663P), two un-paired FKS mutant strains (S663F and S629P), and a WT reference strain (CBS138) were included. Growth kinetics were measured over 24 h in 96-well microplate containing liquid RPMI. After overnight growth in RPMI and staining with a chitin specific fluorescent marker, morphology and chitin were assessed at the single-cell level utilizing high-content imaging technique. Virulence was evaluated in Galleria mellonella larvae by injecting 107 cells/larvae. Mortality was assessed daily for 5 d.

Results: Significant differences in growth kinetics, frequency of morphologic phenotypes within the cell populations (non-budding, single-bud, multiple-buds), and virulence were observed between strains obtained from different patients (p<0.05 for each). However no difference was observed between paired index-WT and persistent-FKS S663P mutants. Compared to index-WT and the CBS138 reference strain, FKS mutant isolates (S663P, S629P, and S663F) had significantly elevated cell wall chitin content (p<0.05). Neither chitin content, the presence of an FKS mutation, nor in-vitro growth characteristics were found to be associated with virulence. Virulence was strongly correlated with the frequency of multi-bud cells within the population however, with 5-d post-injection survival rates of 4% vs. 28% for high-frequency (>12% multi-bud cells) and low frequency strains, respectively (p<0.001).

Conclusion: Acquired FKS-mediated echinocandin resistance induced significant alterations in cell wall chitin content but was not observed to attenuate fitness or virulence. Virulence was highly associated with the frequency of cells with distinct morphology.

Chenlin Hu, PhD1, Gary Fong, PharmD2 and Nicholas D. Beyda, PharmD, BCPS1,2, (1)Pharmacy Practice and Translational Research, University of Houston College of Pharmacy, Houston, TX, (2)CHI St. Luke's Health - Baylor St. Luke's Medical Center, Houston, TX

Disclosures:

C. Hu, None

G. Fong, None

N. D. Beyda, Astellas: Grant Investigator and Scientific Advisor , Consulting fee and Research grant .

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