Delineation of Clavispora lusitaniae clinical isolates by polymerase chain reaction-single strand conformation polymorphism analysis of the ITS1 region: a retrospective study comparing five typing methods

Abstract

Strain delineation of the emerging opportunistic pathogen Clavispora lusitaniae was studied using 12 strains, including two strains of known opposite mating type, CBS 6936 (h+) and CBS 5094 (h-), and 10 strains isolated between 1998 and 2001 from immunocompromized patients. This retrospective study assessed the occurrence of C. lusitaniae subtypes within and among hospitals, and in outpatients who were regularly screened for fungal infections in the course of radio-chemotherapy. Strain typing was accomplished for the first time using single strand conformation polymorphism (SSCP) analysis of amplicons of the ribosomal DNA internal transcribed spacer (ITS) 1 and 2 regions. The results were compared with those produced by three pulsed-field gel electrophoresis (PFGE) methods and PCR fingerprinting with the minisatellite-specific primer M13. Karyotyping separated 7-9 chromosomes, not 6-8 as previously reported. Pulsotyping of SfiI and NotI digested chromosomes grouped isolates in five and four distinct clusters, respectively. All methods revealed strain heterogeneity, though not as extensive as previously recorded. SSCP analysis of the ITS1 region generated five subtypes, based on a sequencing-confirmed nucleotide polymorphism. The discriminatory power of this method was high. All strains displayed a homogeneous SSCP pattern for the ITS2 region. ITS1 PCR-SSCP appears to allow rapid and reliable delineation of C. lusitaniae strains. Pending examination of a larger sample size and interlaboratory study, this protocol can be recommended for rapid prospective identification of hospital outbreaks.