Related Experiment Videos
Typing of Histoplasma capsulatum by restriction fragment length polymorphisms in a nuclear gene
E J Keath1, G S Kobayashi, G Medoff
1Department of Biology, Saint Louis University, Missouri 63103.
Abstract:
We previously described yps-3, a Histoplasma-specific nuclear gene probe useful in the identification of Histoplasma capsulatum. By using restriction fragment length polymorphisms (RFLPs) of DNA detected by the yps-3 gene and mitochondrial DNA, 76 clinical and soil isolates of H. capsulatum were classified. The majority of North American isolates obtained from endemic regions of the midwestern United States were members of the previously characterized class 2, although four clinical isolates from different patients with AIDS from that region were grouped in class 1 with the temperature-sensitive Downs strain. A Florida soil isolate (FLS1) was placed in class 4 on the basis of RFLP with both probes. Two American Type Culture Collection strains (G184B and G186B) from Panama were grouped into class 3 by this analysis. A group of five H. capsulatum isolates obtained from patients with AIDS in New York City were typed into a new class 5 on the basis of yps-3 polymorphisms; those organisms fell into two broad mitochondrial DNA patterns, designated 5b and 5c. Two new isolates from Panama were also members of this broad yps-3 class 5 group, but they exhibited a distinct mitochondrial DNA profile (class 5a). A sixth class was detected in DNA obtained from a patient with AIDS from Panama; that DNA had unique RFLP profiles with respect to both probes. These observations suggest that the Histoplasma-specific yps-3 gene probe is a sensitive tool for typing H. capsulatum in clinical specimens. Additionally, these studies provide molecular support for the hypothesis that AIDS-associated histoplasmosis in nonendemic areas is due to reactivation of a previously acquired infection.
Insights
The yps-3 gene probe effectively identifies and classifies Histoplasma capsulatum isolates using DNA fingerprinting. This molecular typing supports the theory that AIDS-related histoplasmosis in new areas stems from prior infections.
Area of Science:
- Mycology
- Molecular Biology
- Infectious Diseases
Background:
- Histoplasma capsulatum is a fungal pathogen causing histoplasmosis.
- Accurate identification and classification of H. capsulatum isolates are crucial for epidemiological studies and patient management.
- Previous methods for classifying H. capsulatum were limited in their discriminatory power.
Purpose of the Study:
- To classify 76 clinical and soil isolates of Histoplasma capsulatum using DNA fingerprinting techniques.
- To evaluate the utility of the Histoplasma-specific nuclear gene probe yps-3 and mitochondrial DNA in classifying isolates.
- To investigate the molecular epidemiology of H. capsulatum, particularly in relation to AIDS patients.
Main Methods:
- Restriction Fragment Length Polymorphisms (RFLPs) were employed to analyze DNA.
- Both the yps-3 nuclear gene probe and mitochondrial DNA were used for RFLP analysis.
- Seventy-six clinical and soil isolates of H. capsulatum were classified into distinct genetic groups.
Main Results:
- The yps-3 probe and RFLP analysis successfully classified 76 H. capsulatum isolates into six distinct genetic classes.
- Most North American isolates belonged to class 2, while isolates from AIDS patients in New York City formed a new class 5.
- Isolates from Panama and Florida exhibited unique RFLP profiles, indicating genetic diversity.
Conclusions:
- The Histoplasma-specific yps-3 gene probe is a sensitive and effective tool for typing H. capsulatum isolates.
- Molecular typing provides evidence supporting the hypothesis that AIDS-associated histoplasmosis in non-endemic areas results from reactivation of latent infections.
- The study highlights the genetic diversity of H. capsulatum and its implications for understanding disease transmission and pathogenesis.