Biomedical subjects

Claude Pujol

Publications and source records attributed to Claude Pujol.

23 records · Page 2Linked to original sources

PubMed2002

Microevolutionary changes and chromosomal translocations are more frequent at RPS loci in Candida dubliniensis than in Candida albicans.

The Cd1 fingerprinting probe of Candida dubliniensis, which is extremely effective in identifying microevolutionary changes in infecting populations, generates hybridization patterns that are similar to those generated by the Candida albicans fingerprinting probe Ca3. Since Ca3 recognizes microevolutionary changes through the repeat sequence RPS, it was suggested that Cd1 also contains a RPS-like element. To test this possibility, the C. albicans RPS unit was used as a probe, and an RPS-like element, RPSd1, was cloned from C. dubliniensis. The sequence of RPSd1 was 76% homologous to that of the C. albicans RPS unit RPS620 and the organization, including the non-RPS 3' and 5' bordering sequences, was highly similar. This analysis revealed additional copies of the repeat extraalt element and short additional repeat (SAR) sequences in both RPSd1 and RPS620 not previously identified in the latter. This analysis has allowed us to develop a model of RPSd1 organization and to revise the model for RPS620 organization. An estimate of the average frequency of reorganization (duplication and deletion) per RPS unit in C. dubliniensis was similar to that for C. albicans, but the estimate of frequency of reorganization per C. dubliniensis genome was higher, most probably as a result of the higher estimated average number of RPS clusters in C. dubliniensis. These results demonstrate that the microevolutionary changes identified by the Cd1 fingerprinting probe are based on the reorganization of RPS-like elements and are, therefore, similar to the microevolutionary changes identified by the Ca3 probe of C. albicans. Linkage analysis of pairs of markers situated on either side of an RPS cluster on chromosome 7 further revealed frequent recombination between non-homologous chromosomes at the RPS cluster in C. dubliniensis strains, but not in C. albicans strains, suggesting that RPS clusters may function as recombination hot spots in C. dubliniensis.

Base Sequence↗

PubMed2002

In Candida albicans, white-opaque switchers are homozygous for mating type.

The relationship between the configuration of the mating type locus (MTL) and white-opaque switching in Candida albicans has been examined. Seven genetically unrelated clinical isolates selected for their capacity to undergo the white-opaque transition all proved to be homozygous at the MTL locus, either MTLa or MTLalpha. In an analysis of the allelism of 220 clinical isolates representing the five major clades of C. albicans, 3.2% were homozygous and 96.8% were heterozygous at the MTL locus. Of the seven identified MTL homozygotes, five underwent the white-opaque transition. Of 20 randomly selected MTL heterozygotes, 18 did not undergo the white-opaque transition. The two that did were found to become MTL homozygous at very high frequency before undergoing white-opaque switching. Our results demonstrate that only MTL homozygotes undergo the white-opaque transition, that MTL heterozygotes that become homozygous at high frequency exist, and that the generation of MTL homozygotes and the white-opaque transition occur in isolates in different genetic clades of C. albicans. Our results demonstrate that mating-competent strains of C. albicans exist naturally in patient populations and suggest that mating may play a role in the genesis of diversity in this pernicious fungal pathogen.

Candida albicans↗

PubMed2002

Ca3 fingerprinting of Candida albicans isolates from human immunodeficiency virus-positive and healthy individuals reveals a new clade in South Africa.

To examine the question of strain specificity in oropharyngeal candidiasis associated with human immunodeficiency virus (HIV) infection, oral samples were collected from 1,196 HIV-positive black South Africans visiting three clinics and 249 Candida albicans isolates were selected for DNA fingerprinting with the complex DNA fingerprinting probe Ca3. A total of 66 C. albicans isolates from healthy black South Africans and 46 from healthy white South Africans were also DNA fingerprinted as controls. Using DENDRON software, a cluster analysis was performed and the identified groups were compared to a test set of isolates from the United States in which three genetic groups (I, II, and III) were previously identified by a variety of genetic fingerprinting methods. All of the characterized South African collections (three from HIV-positive black persons, two from healthy black persons, and one from healthy white persons) included group I, II, and III isolates. In addition, all South African collections included a fourth group (group SA) completely absent in the U.S. collection. The proportion of group SA isolates in HIV-positive and healthy black South Africans was 53% in both cases. The proportion in healthy white South Africans was 33%. In a comparison of HIV-positive patients with and without oropharyngeal symptoms of infection, the same proportions of group I, II, III, and SA isolates were obtained, indicating no shift to a particular group on infection. However, by virtue of its predominance as a commensal and in infections, group SA must be considered the most successful in South Africa. Why group SA isolates represent 53 and 33% of colonizing strains in black and white South Africans and are absent in the U.S. collection represents an interesting epidemiological question.

Candida albicans↗

PubMed2002

Ca3 fingerprinting of Candida albicans bloodstream isolates from the United States, Canada, South America, and Europe reveals a European clade.

It was previously demonstrated by a cluster analysis that 26 unrelated U.S. isolates of Candida albicans separated into three distinct groups (groups I, II, and III) while South African isolates separated into four distinct groups (groups I, II, III, and SA). To verify the absence or underrepresentation of SA isolates in North America, and to identify which groups are represented in Europe and South America, collections of bloodstream isolates from each geographical locale were analyzed by cluster analyses based on genetic fingerprinting with the Ca3 probe. The results verify that North America is almost devoid of SA isolates (2%). However, the results reveal a new clade, designated group E, relatively specific to Europe. While 26% of a European collection of 46 isolates was composed of group E isolates, only 2% of the 164 North American isolates, 5% of 22 South American isolates, and 1% of 361 South African isolates were composed of group E isolates. The North American collection proved to be the least-diverse collection in regard to group representation. In a comparison of collections from the Northeast, Midwest, and Southwest regions of the United States, Canada, and South America, it was demonstrated that both the U.S. Southwest and the South American collections were devoid of group II isolates. Together these results identify for the first time a European-specific clade and demonstrate clear distinctions in the representations of the five demonstrated clades (groups I, II, III, SA, and E) in different geographical locales.

Blood↗

PubMed1997

Development and verification of fingerprinting probes for Candida glabrata.

Since Candida glabrata has emerged as one of the most common Candida pathogens, DNA probes have been developed which fulfil the requirements for effective fingerprinting. Using a screen for complex genomic fragments containing moderately repetitive sequences, seven DNA probes were cloned which generate complex Southern blot hybridization patterns with EcoRI-digested C. glabrata DNA. All of the probes are species-specific and the majority cross-hybridize to varying degrees. The capacity of two of the probes, Cg6 and Cg12, to measure genetic distance between independent isolates is verified by comparing clustering in dendrograms based on similarity coefficients computed between all pairs of 39 independent isolates fingerprinted with Cg6, Cg12 and randomly amplified polymorphic DNA. The capacity of the probes Cg6 and Cg12 to assess microevolution in clonal populations of infecting C. glabrata over time is also demonstrated. These probes can now be used in large computer-assisted epidemiological studies.

AIDS-Related Opportunistic Infections↗