Utility of CSP typing to sub-type clinical Aspergillus fumigatus isolates and proposal for a new CSP type nomenclature.

CSP typing is a newly developed sub-typing strategy that employs comparative DNA sequence analysis of the 12-mer tandem repeat region of the AFUA_3G08890 gene. In order to allow standardization of analysis and exchange of results between laboratories, we propose a new nomenclature for individual CSP repeats as well as for CSP types. A collection of 209 clinical isolates of Aspergillus fumigatus recovered from various hospitals throughout The Netherlands was analyzed by using CSP typing and this newly proposed nomenclature. Eighteen different CSP types were recognized, positioning the CSP gene as a typing target between the relatively low discriminatory MLST loci and the highly discriminatory microsatellite markers. CSP typing may be a welcome addition to the existing molecular methods to study the diversity of A. fumigatus at the sub-population level. The results also show the presence of lineages of closely related CSP types within the A. fumigatus population, adding unique and valuable information about the population structure of A. fumigatus.