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2017 OMIG Abstract 24

Phenotypic diversity and speciation of Fusarium isolates from the Mycotic Ulcer Treatment Trial (MUTT)
K Fuller¹, NV Prajna², K Ray³, L Prajna², K Dharmalingam², D Giacalone¹, N Felan¹, RA Cramer^1
, TM Lietman³, ME Zegans^1
1Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire; ²Aravind Medical Research Foundation,Tamilnadu, India; ³F.I Proctor Foundation UCSF, San Francisco, California

Purpose: To study the diversity of Fusarium isolates obtained during the MUTT study and to identify potential correlations with clinical outcomes. The MUTT study was an NEI sponsored trial comparing natamycin to voriconazole in the treatment of fungal keratitis. The majority of the patients were seen in the Aravind Eye Hospital System. Fusarium species were the most commonly isolated fungal pathogen in the study.

Methods: 100 MUTT Fusarium isolates were evaluated. Differences in growth characteristics and colony morphology were noted. The ribosomal DNA (rDNA) loci, including the internal transcribed spacer (ITS) and the intergenic spacer (IGS), were PCR amplified.  These amplicons were subject to Sanger sequencing, the results of which were used as BLAST queries (NCBI) to determine the species-level identification of the respective isolates.  The isolates were then placed into two groups (“F. solani” and “non-solani”). Statistical analysis correlating microbiologic data with MUTT clinical data was performed at UCSF.

Results: Analysis of the ITS locus was sufficient to identify the isolates as either F. solani (80%) or as some other species (“non-solani”, the remaining 20%).  The IGS was used to further resolve the “non-solani” isolates, which included F. delphinoides, F. napiforme and F. proliferatum, among other species. Isolates identified as F. solani had on average larger infiltrate size (0.74 mm2) on clinical presentation compared to the “non-solani” isolates (p=0.056).  Microbiological assessment of the F. solani isolates revealed strain heterogeneity with respect to growth rate and pigmentation patterns.

Conclusions: Conclusions: Fusarium solani was the predominant Fusarium species isolated during the MUTT study and F. solani isolates presented with larger infiltrates than non-solani isolates. However, diversity in terms of growth characteristics and colony morphology exists within this species, suggesting that there is considerable strain diversity that may impact treatment outcomes. Continued microbiologic analysis of these isolates may yield clinically relevant insights into the pathologic mechanisms of Fusarium keratitis and improved treatment strategies.

2017 Agenda and Abstracts | < Previous Next >