Abstract
Infections caused by Histoplasma capsulatum are found most often in endemic regions of North, Central, and South America. H. capsulatum has been divided into eight geographic clades by multi-locus sequence typing (MLST). Recently, one isolate and five formalin-fixed paraffin-embedded (FFPE) tissue samples were received from six of 15 suspected cases of histoplasmosis in cats residing in areas not known to be endemic for H. capsulatum. Polymerase chain reaction (PCR) amplification and sequence analysis of the rDNA ITS-2 region confirmed the diagnosis of H. capsulatum. Since these cases were not, as noted, from the accepted endemic areas, it was of interest to understand the molecular epidemiology of these isolates. Results of molecular analysis indicated that the H. capsulatum recovered from the cats were most closely related to the North American-1 clade, but clustered separately outside this clade, suggesting that the H. capsulatum infecting the animals may represent a separate clade or phylogenetic species. This study also demonstrated the utility of obtaining valuable molecular subtype data directly from archived FFPE tissue blocks, particularly when a fungus culture was not performed or is otherwise unavailable.
Acknowledgments
We acknowledge Drs Ronald A. Oyster, Eric Kufuor- Mensah, Barbara E. Powers, Bruce H. Williams, and Clifton Drew for providing the FFPE tissue blocks from the cat cases. We also acknowledge the CDC Genomics Unit for their support in performing the sequencing analysis.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and the writing of the paper.
This paper was first published online on Early Online on 22 October 2012.