Characterization of Coccidioides immitis isolates by restriction fragment length polymorphisms

Abstract

The marked increase in the number of cases of coccidioidomycosis in California in 1992 led to a study of isolates from various patients and environmental sources by restriction fragment length polymorphism (RFLP) analysis. Of 15 different isolates, most of the isolates (13 of 15) from California and 1 from Venezuela yielded one main RFLP pattern with evidence of two subgroups. The other two isolates (both from patients in the San Joaquin Valley of California) yielded a different RFLP pattern. Coccidioides immitis is a biphasic, terricolous fungus found in the southwestern United States, Mexico, and Central and South America (14). In the soil, the fungus grows in a hyphalarthroconidial form. The arthroconidia produce infection in a susceptible human or other animal host, usually via the respiratory route. During the years 1991 through 1993, there was a marked increase in the incidence of coccidioidomycosis in California. This has occurred both in the usual high-risk areas and in areas where the disease is less prevalent (15). In the past, it has been possible to distinguish isolates of C. immitis from various patients and geographic locations by phenotypic characteristics (4, 5, 7-9, 16). However, little is known of the extent of genetic variation within C. immitis at the DNA sequence level (13). The ability to distinguish genotypes of isolates would be useful in investigating the source(s) of outbreaks of infection and in defining the relatedness of isolates recovered from different patients. As a first step, we used restriction fragment length polymorphisms (RFLPs) to compare different C. immitis isolates.

The Evolutionary Biology and Population Genetics Underlying Fungal Strain Typing

“…The Silveira isolate, collected in California in 1951, fell in the non-California group. This isolate was different from most California isolates in the RFLP study (122). It is possible that the patient acquired coccidioidomycosis outside California, in a manner similar to that of a Texas patient who had acquired C. immitis in California (24).…”

“…Strain typing. C. immitis recently entered the molecular age with an RFLP study of repeated DNA (probably mtDNA and rDNA) from 1 Venezuelan and 14 Californian isolates (122). The technique sorted the isolates into two groups, one with two Californian clinical isolates, including the often studied Silveira isolate, and the other with the rest.…”

Investigating Clinical Issues by Genotyping of Medically Important Fungi: Why and How?

“…The first typing approaches to explore the intraspecific relationships of C. immitis were performed in the 1990s using RFLP (347,348) and genealogies of five nuclear genes (349). The authors thus distinguished Californian isolates from non-California isolates (349).…”

The Population Biology of Coccidioides

“…One of the first molecular analyses of genetic variation in Coccidioides was a restriction fragment length polymorphism (RFLP) study (see TABLE 1 for a list of all molecular-based studies discussed in this section). 42 This RFLPbased study looked at fifteen strains and found one RFLP pattern among 13 of 15 isolates, and 2 isolates with a second pattern. These patterns could be consistent with a predominately clonal species; all of the strains were obtained from patients in California.…”