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Published on: March 4, 2017
Three distinct genotypes within Candida parapsilosis from clinical sources
1Department of Microbiology, Medical College of Ohio, Toledo 43699-0008, USA.
Abstract:
Three genetically distinct groups of Candida parapsilosis were detected among clinical isolates. These were distinguishable on the basis of isoenzyme profiles and DNA sequences of internally transcribed spacer (ITS) sequences flanking the 5.8S RNA gene. In an investigation of 45 strains, including 32 clinical isolates from Texas, C. parapsilosis group I composed the majority of the common clinical isolates. The type strain of C. parapsilosis was a member of this group. The 10 group II isolates were indistinguishable from group I strains when tested with the API 20C kit. The two group III isolates differed from those in groups I and II by being D-xylitol positive by the API 20C kit; however, isolates in all groups assimilated D-xylitol from broth. Isoenzyme profiles excluded the close relationship of any of these groups to Lodderomyces elongisporus, which is a teleomorphic yeast that has a physiological profile similar to that of C. parapsilosis. Although there were insignificant differences in the ITS2 rDNA sequences, comparisons of the ITS1 sequences revealed several differences. A sequence analysis of ITS1 in which missing bases were counted as mismatches showed the following similarities: group I versus group II, 87.7%; group I versus group III, 82.1%; group II versus group III, 84.5%. Also, the activity of secreted proteinase showed differences among the three groups, with many group I isolates having moderate to high activity. The degree of susceptibility to antifungal agents, amphotericin B, ketoconazole, and 5-fluorocytosine, could not be used to determine an isolate's group.
Insights
Three distinct groups of Candida parapsilosis were identified using isoenzyme profiles and DNA sequencing. These genetic variations impact clinical isolate classification and proteinase activity, aiding in understanding this opportunistic fungal pathogen.
Area of Science:
- Medical Mycology
- Molecular Biology
- Clinical Microbiology
Background:
- Candida parapsilosis is an opportunistic fungal pathogen causing various infections.
- Accurate identification and differentiation of Candida species are crucial for effective treatment.
- Previous classifications relied on phenotypic characteristics, which can be unreliable.
Purpose of the Study:
- To genetically differentiate clinical isolates of Candida parapsilosis.
- To investigate the genetic relatedness of different C. parapsilosis groups.
- To assess the utility of isoenzyme profiles and DNA sequencing for Candida parapsilosis typing.
Main Methods:
- Isoenzyme electrophoresis was used to analyze protein profiles of isolates.
- DNA sequencing of internally transcribed spacer (ITS) regions (ITS1 and ITS2) was performed.
- Phenotypic characterization using the API 20C kit and antifungal susceptibility testing were conducted.
Main Results:
- Three distinct genetic groups (I, II, and III) of C. parapsilosis were identified.
- Group I comprised the majority of common clinical isolates, including the type strain.
- While ITS2 sequences showed minor differences, ITS1 sequences revealed significant variations between groups.
- D-xylitol assimilation differed between groups on the API 20C kit, but all assimilated it from broth.
- Secreted proteinase activity varied among the groups, with Group I showing higher activity.
- Antifungal susceptibility testing did not differentiate the groups.
Conclusions:
- Isoenzyme profiles and ITS1 DNA sequencing are effective methods for differentiating C. parapsilosis groups.
- Genetic grouping provides insights into the population structure of C. parapsilosis clinical isolates.
- Further research into the clinical significance of these genetic groups is warranted.
