Probe Ca3 Research Articles

Most frequent scenario for recurrent Candida vaginitis is strain maintenance with "substrain shuffling": demonstration by sequential DNA fingerprinting with probes Ca3, C1, and CARE2.

The following three basic scenarios have emerged for the genetic relatedness of strains in recurrent vaginal candidiasis: strain maintenance without genetic variation, strain maintenance with minor genetic variation, and strain replacement. To test the frequency of each of the three scenarios, the genetic relatedness of Candida albicans isolates from each of 18 patients with recurrent infections was assessed by sequential DNA fingerprinting with the following three probes: the Ca3 probe; the C1 probe, a subfragment of the Ca3 probe which hybridizes to hypervariable genomic fragments; and the unrelated CARE2 probe. In each of the 18 patients with recurrent infections, the same strain was responsible for sequential infections, suggesting that the predominant scenario is strain maintenance. However, in 56% of these patients, the strain exhibited minor genetic variations in sequential infections. These changes were not found to be progressive. Rather, the changes suggest that substrains of an established infecting strain are shuffled in sequential infections. Results are also presented that in 45% of patients with recurrent infections, oral and vulvovaginal isolates were identical, in 35% they were highly related but not identical, and in 20% they were unrelated. These results differ markedly from those for commensal isolates simultaneously cultured from the oral cavity and vulvovaginal region of healthy individuals. Finally, it is demonstrated that in all eight cases in which C. albicans was isolated from both the male sexual partner of the patient with a recurrent infection and the patient, an isolate from the male partner was identical or highly related to the vulvovaginal strain. These results demonstrate that in patients with recurrent vulvovaginitis, a single strain usually dominates both in the different body locations of the patient and in the male partner and that it is maintained through sequential infections. However, in patients with recurrent infections, different substrains of the established clone dominate in an apparently random fashion, a process that we refer to as "substrain shuffling".

Colonizing populations of Candida albicans are clonal in origin but undergo microevolution through C1 fragment reorganization as demonstrated by DNA fingerprinting and C1 sequencing.

The genetic homogeneity of nine commensal and infecting populations of Candida albicans has been assessed by fingerprinting multiple isolates from each population by Southern blot hybridization first with the Ca3 probe and then with the 0.98-kb C1 fragment of the Ca3 probe. The isolates from each population were highly related, demonstrating the clonal origin of each population, but each population contained minor variants, demonstrating microevolution. Variation in each case was limited to bands of the Ca3 fingerprint pattern which hybridized with the 0.98-kb C1 fragment. The C1 fragment was therefore sequenced and demonstrated to contain an RPS repetitive element. The C1 fragment also contained part or all of a true end of the RPS element. These results, therefore, demonstrate that most colonizing C. albicans populations in nonimmuno-suppressed patients are clonal, that microevolution can be detected in every colonizing population by C1 hybridization, and that C1 contains the repeat RPS element.

Cluster of oral atypical Candida albicans isolates in a group of human immunodeficiency virus-positive drug users

Twenty-one chlamydospore-forming and germ tube-positive Candida albicans clinical isolates from 15 human immunodeficiency virus (HIV)-positive and 3 HIV-negative patients were examined by two different genetic methods. Multilocus enzyme electrophoresis and hybridization with the C. albicans-specific Ca3 probe showed that such isolates can be split into two genetically distinct groups that can be clearly distinguished. One group mainly contained strains with atypical sugar assimilation patterns and could be distinguished from the other group by the absence of intracellular beta-glucosidase activity. All 13 strains belonging to this group were isolated from the oral cavities of asymptomatic HIV-positive drug users and may be less pathogenic than the eight strains from the other group isolated either from HIV-positive patients with oropharyngeal candidiasis or from HIV-negative patients with invasive candidiasis.

Evolution and replacement of Candida albicans strains during recurrent vaginitis demonstrated by DNA fingerprinting.

Southern blot hybridization with the Ca3 probe and the C fragment of the Ca3 probe was used to assess the genetic relatedness of Candida albicans strains from one patient with recurrent C. albicans infection in whom the same strain was maintained, one patient in whom the infecting strain was replaced, and their male sexual partners. In the patient in whom the infecting strain was maintained, the infecting strain exhibited a minor genetic change in each successive episode of Candida vaginitis. These genetic changes occurred in the C-fragment bands of the Ca3 hybridization pattern. In the patient in whom the infecting strain was replaced by another infecting strain, a transition infection involved a genetically mixed infecting population, and the replacement strain appeared to have originated from the oral cavity of the male partner. The results demonstrate that the infecting strains of recurrent Candida vaginitis are not genetically stable, that drug treatment can result in the selection of variants of the previously infecting strain or replacement by a genetically unrelated strain, and that the male partner can be the source of a replacement strain.

Genetic similarity and phenotypic diversity of commensal and pathogenic strains of Candida albicans isolated from the oral cavity

Colony phenotype and genetic similarity were assessed within and between groups of commensal and pathogenic strains of Candida albicans collected from the oral cavities of individuals in a single geographical locale. Thirty-eight percent of pathogenic isolates contained predominant or minor variant colony morphologies (other than smooth) when samples from the sites of infection were cultured on plates, while 16% of commensal isolates contained minor variant colony morphologies when samples from the sites of carriage were cultured. The genetic similarities of isolates within and between groups were assessed by DNA fingerprinting by using Southern blot hybridization with the fingerprinting probe Ca3 and analysis with the computer-assisted, automated Dendron system. Both the commensal and the pathogenic groups contained a major cluster of genetically similar C. albicans isolates representing 31 and 33% of the strains in the respective groups. When a combined dendrogram of both commensal and pathogenic isolates was generated, the major clusters of genetically similar isolates in each group mixed into one large cluster. Minor clusters in the individual dendrograms also mixed. These results suggest common clonal origins for commensal and pathogenic strains in the same geographical locale.

Characterization and partial nucleotide sequence of the DNA fingerprinting probe Ca3 of Candida albicans

The moderately repetitive Ca3 fragment of Candida albicans has been used as an effective DNA fingerprinting probe in epidemiological studies. EcoRI digestion of Ca3 DNA results in seven fragments of 4.2 kb (A), 2.98 kb (B), 2.85 kb (C), 0.77 kb (D1), 0.77 kb (D2), 0.38 kb (E), and 0.30 kb (F). Five of these EcoRI fragments have been mapped in the 5'-3' order C B D1 A D2. The intact Ca3 probe and the three largest EcoRI fragments, A, B, and C, were individually used to probe Southern blots of EcoRI-digested DNA of a set of test strains, transverse alternating field electrophoresis-separated chromosomes of strain 3153A, and Northern (RNA) blots of test strain 3153A. Fragments, A, B, and C each generate a different Southern blot hybridization pattern with EcoRI-digested whole-cell DNA; Ca3 sequences are present in at least five of seven separable chromosomes and a minichromosome of strain 3153A; fragments A, B, and C are distributed differently on chromosomes; and fragments A, B, and C do not cross-hybridize. Ca3 hybridizes to three major transcripts of 2.8, 2.3, and 1.5 kb. Fragment A hybridizes intensely to the 1.5-kb transcript, while fragments B and C both hybridize intensely to the 2.8- and 2.3-kb transcripts. The B fragment, which contains 2,980 bp and contributes to the major portion of the Ca3 pattern, was sequenced. Both direct and inverted repeat sequence motifs were identified. These results provide us with initial insights into the evolution of the Ca3 pattern and the nature of the probe.