Molecular typing of Penicillium marneffei isolates from Thailand by NotI macrorestriction and pulsed-field gel electrophoresis

Penicillium marneffei is recognized as one of the most frequently detected opportunistic pathogens of AIDS patients in northern Thailand. We undertook a genomic epidemiology study of 64 P. marneffei isolates collected from im munosuppressed patients by pulsed-field gel electrophoresis (PFGE) with res triction enzyme NotI. Among the 69 isolates fingerprinted by PFGE, 17 were compared by HaeIII restriction endonuclease typing. The PFGE method demonst rated a higher degree of discriminatory power than restriction endonuclease typing with HaeII. Moreover, an impressive diversity of P. marneffei isola tes was observed, as there were 54 distinct macrorestriction profiles among the 69 isolates of P. marneffei. These profiles were grouped into two larg e clusters by computer-assisted similarity analysis: macrorestriction patte rn I (MPI) and MPII, with nine subprofiles (MPIa to MPIf and MPIIa to MPIIc ). We observed no significant correlation between the macrorestriction patt erns of the A marneffei isolates and geographical region or specimen source . It is interesting that all isolates obtained before 1995 were MPI, and we found an increase in the incidence of infections with MPII isolates after 1995. We conclude that PFGE is a highly discriminatory typing method and is well suited for computer-assisted analysis. Together, PFGE and NotI macror estriction allow reliable identification and epidemiological characterizati on of isolates as well as generate a manageable database that is convenient for expansion with information on additional A marneffei isolates.