Penicillium marneffei (ATCC 24100) was first isolated from a naturally acquired human infection in the U.S.A. by DiSalvo et al. in 1973. In 1979, this isolate was studied by Pitt who reidentified it ...as Penicillium primulinum. This prompted us to examine the antigenic relationship between P. marneffei and P. primulinum by comparing their exoantigens. The antigenic relationships of 11 isolates, including the type strains of P. marneffei and P. primulinum, were examined. Each exoantigen extract was tested simultaneously against rabbit anti-P. marneffei and P. primulinum antisera in the presence of the appropriate reference antigens. All eight isolates of P. marneffei, including ATCC 24100, produced two to four specific precipitin lines against their homologous antiserum. However, four of the eight extracts cross-reacted with unabsorbed antiserum to P. primulinum. The P. primulinum extracts contained specific exoantigens which only reacted with the anti-P. primulinum antiserum. Non-specific cross-reactions were eliminated by absorption procedures. On the basis of the specific exoantigens produced by both species, P. marneffei and P. primulinum were found to be antigenically distinct. Isolate ATCC 24100 was shown to be closely related to the other P. marneffei isolates and distinct from P. primulinum. Our results confirm the original identification of ATCC 24100 as P. marneffei and not P. primulinum as Pitt had concluded.
