The Disease

The yeast-like fungi of the genus Candida are an important cause of nosocomial infection, and rank fourth in bloodstream infections in the US. Candida albicans is the most common causative organism of these infections, but other Candida species, including Candida parapsilosis, are becoming increasingly prevalent. Candida parapsilosis is associated with approximately 25% of Candida infections in European hospitals, and in South America the incidence of this species increased from 12% to 25% between 1997 and 1999. It is now the second most commonly isolated Candida species from blood cultures in Europe, Canada and Latin America, and in some European hospitals even outranks Candida albicans.

Unlike other Candida species, C. parapsilosis has been found on the hands of health care workers, resulting subsequent nosocomial infection associated with handling central venous catheters. C. parapsilosis is a particular problem as it tends to grow as biofilms on implanted medical devices, conferrin almost total resistance to antifungal drugs. The ability to grow as a biofilm is directly related clinically significant disease, which is a unique attribute of C. parapsilosis.

The Organism

C. parapsilosis strains have historically been categorised as Group I, II or III on the basis of molecular fingerprinting. Group I strains are predominant in clinical isolates. Analysis of levels of heterozygosity and of mitochondrial genome architecture supports the hypothesis that three groups represent three different species. It has been proposed that Group II and Group III isolates are are different species and should be renamed C. orthopsilosis and C. metapsilosis respectively. Group I isolates are therefore the most authentic and clinically relevant representatives of C. parapsilosis.

The estimated diploid genome size of Candida parapsilosis is 26 Mb with a chromosome number of 14, suggesting a haploid genome of 13 Mb, with 7 chromosomes. The C. parapsilosis isolate 317 from CDC, Atlanta was selected for sequencing. This isolate came from the hands of a hospital worker, who was the source for an outbreak of infection in a Mississippi community hospital in 2001, and was characterised and described in Kuhn et al and Clark et al.

The Project

The Wellcome Trust Sanger Institute Pathogen Genomics group is sequencing the genome of Candida parapsilosis in collaboration with Dr Geraldine Butler of the Department of Biochemistry, University College Dublin, Prof. Ken Wolfe, Smurfit Institute of Genetics, Trinity College, Dublin and Prof. Neil Gow, Department of Molecular and Cell Biology, University of Aberdeen.

Progress

The genome of C. parapsilosis is published in Butler et al (2009), Evolution of pathogenicity and sexual reproduction in eight Candida genomes, Nature 459(7247):657-62.

Assembly of the C. parapsilosis shotgun reads produced 24 contigs of over 2kb in length. These contigs contain 222792 reads and have a total length of 13.1Mb. There are 8 contigs larger than 200kb and the N50 of the assembly is 2215 kb. The average genome coverage of the genome is 9.2-fold.

The sequence data are available in GenBank/EMBL/DDBJ with accession numbers CABE01000001 to CABE01000024 as well as via our ftp site. They may also be searched using our BLAST server.