Lectin typing of Haemophilus ducreyi

Molecular characterization of Haemophilus ducreyi isolates from different geographical locations

The technique of random amplified polymorphic DNA (RAPD) was adapted and optimized to study Haemophilus ducreyi isolates. A panel of 43 strains isolated from chancroid patients from different countries in Africa, Europe, North America, and Asia were characterized. The strains were also studied with respect to lipooligosaccharide (LOS) migration and immunoblotting patterns and the presence of cytolethal distending toxin genes. The RAPD method with the OPJ20 primer generated nine banding patterns (1 to 9). The majority of the isolates were clustered into two major profiles, 14 and 13 strains into profiles 1 and 2, respectively, and just a few strains revealed patterns 3 and 4. The isolates from Thailand were exceptional in that they showed greater diversity and were represented by six different RAPD patterns, i.e., patterns 3 and 5 to 9. The LOS migration and immunoblotting analyses revealed two different patterns, which indicated long and short forms of LOS; the former was found in 20/23 tested strains. Two strains that expressed the short form of LOS were grouped into RAPD pattern 4. The absence of cdtABC genes was observed in only 4/23 strains, and three of these isolates were assigned to RAPD pattern 4. Our results showed limited genotypic and phenotypic variations among H. ducreyi strains, as supported by the conserved RAPD and LOS profiles shared by the majority of the studied strains. However, the RAPD method identified differences between strains, including those from different geographic areas, which indicate the potential of RAPD as an epidemiological tool for the typing of H. ducreyi isolates in countries where chancroid is endemic.

Lectin typing of five medically important Candida species

This study reports the patterns of agglutination of 93 clinical Candida isolates by 14 commercial lectins. The isolates were of the species Candida albicans (55), C. tropicalis (12), C. guilliermondii (10). C. glabrata (eight) and C. parapsilosis (eight). Hundred percent of isolates were agglutinated, at least, by a panel of three lectins: Canavalia ensiformis (ConA), Lens culinaris (LCA) and Pisum sativum (PSA), all of them with alpha-D-mannose specificity. In addition, another panel of three lectins could distinguish between C. glabrata, C. tropicalis and C. albicans. Lectin typing may be of potential value for taxonomic and epidemiological studies of yeasts in clinical laboratories.

Chancroid: from clinical practice to basic science

Chancroid is a sexually transmitted disease caused by the bacterium Haemophilus ducreyi. It usually presents as a genital ulcer and may be associated with regional lymphadenopathy and bubo formation. H. ducreyi infection is predominantly seen in tropical resource-poor regions of the world where it is frequently the most common etiological cause of genital ulceration. Genital ulcer disease has been shown to be an extremely important co-factor in HIV transmission. With the advent of the AIDS epidemic, there has been increased research effort to elucidate those factors involved in the pathogenesis of chancroid. Several putative virulence factors have now been identified and isogenic H. ducreyi mutants constructed by mutagenesis of their encoding genes. This approach has facilitated investigations into the role each of these putative virulence factors may play in H. ducreyi pathogenesis through the use of in vitro and in vivo model systems. One major goal of current chancroid research is to identify antigens which are immunogenic and could form the basis of a vaccine against H. ducreyi infection. Such a vaccine, if shown to be effective in decreasing the prevalence of chancroid, could have the added benefit of slowing down the HIV incidence rates in those populations where chancroid is a major co-factor for HIV transmission.

Ribosomal DNA typing of Haemophilus ducreyi strains: proposal for a novel typing scheme

Local strains of Haemophilus ducreyi were characterized by ribosomal DNA fingerprinting in order to develop a typing scheme for this organism. Chromosomal DNAs from 30 strains were extracted, and restriction fragments were separated by agarose gel electrophoresis after cleavage with BglII, HindIII, HindII, and BstEII. Of the 30 local strains studied, nine BglII, eight HindIII, six HindII, and five BstEII ribotype patterns were observed. In order to develop a typing scheme, we correlated the ribotype patterns obtained with each of the four enzymes for each strain. By this scheme, 13 ribotypes designated b to n were defined among the local strains. This study demonstrates that there is a diversity of ribotypes among H. ducreyi strains in our area, which emphasizes that there are many strains responsible for chancroid. This novel typing scheme provides a useful tool for further epidemiological studies of chancroid.

Chancroid and Haemophilus ducreyi: an update

Haemophilus ducreyi is a fastidious gram-negative bacillus that causes the sexually transmitted infection chancroid. Chancroid is a major genital ulcerative disease in Africa, Southeast Asia, the Caribbean, and Latin America and is of increasing concern in the United States. Genital ulcerative disease and chancroid in particular have been associated with facilitating the transmission of human immunodeficiency virus. The diagnosis of chancroid based on the clinical appearance of the genital lesion or on the isolation of H. ducreyi on selective medium is relatively insensitive. However, recent advances in nonculture diagnostic tests have enhanced our ability to diagnose chancroid. There has been renewed interest in understanding the pathogenesis of H. ducreyi. In vitro and in vivo models have been developed to help identify important virulence determinants. Through the use of biochemical and molecular techniques, macromolecular components that may be important in virulence have been identified.

Typing of Shigella dysenteriae strains of different serogroups by lectins

Ten different serogroups of Shigella dysenteriae were typed with the aid of lectins of known sugar specificity resulting from their interactions with the carbohydrates on lipopolysaccharides in the outer membrane of bacteria as evidenced by the agglutination-inhibition assay with simple carbohydrates. Lipopolysaccharides of two serogroups of Shigella were precipitated with different lectins and the results were corroborated by those derived from the agglutination assay suggesting that Shigella dysenteriae can be characterized on the species level with the aid of lectins.

Relapsing severe Trichophyton rubrum infections in an immunocompromised host: evidence of onychomycosis as a source of reinfection based on lectin typing

A 64-year-old patient developed recurrent (about 3-6 times a year) generalized skin lesions due to Trichophyton rubrum during long-term steroid treatment of lung fibrosis. Additionally, he suffered for years from onychomycosis of all toes. In the past, short-term internal treatment with griseofulvin and ketoconazole resulted in fast clearing of skin symptoms. Since 1991 relapses have been treated with itraconazole orally. In 1992 material was collected from diseased nails and toe and other skin lesions during three severe attacks of fungal infections and in addition once from toenails during a period without skin manifestations. Trichophyton rubrum was isolated from each sample. Lectin typing of the isolates using five lectins of plant origin resulted in identical lectin patterns for all isolates, thus localizing the toenails as the source of reinfection. The results indicate that lectin typing may play an important role in clinical and epidemiological analysis of dermatophytes.

Non-radioactive ribotyping of Haemophilus ducreyi using a digoxigenin labelled cDNA probe

Haemophilus ducreyi, the causal organism of chancroid, has increased in significance recently due to its association with HIV transmission. Most previous typing systems have exploited phenotypic characteristics. Detection of ribosomal RNA cistrons, ribotyping, was successfully developed to examine H. ducreyi, but required the use of 32P. We have used digoxigenin to define ribotypes from 30 strains of H. ducreyi from diverse geographical locations. This was achieved by agarose gel electrophoresis of restriction enzyme (RE) digested DNA extracts. These extracts were vacublotted onto nylon membrane and probed using digoxigenin labelled complementary DNA probe, prepared from Escherichia coli 16S and 23S ribosomal RNA. From 19 REs tested, Ava II, Hinc II, Bgl II and BstE II gave clear ribotypes. The ribotypes of BstE II and Bgl II used together gave the highest index of discrimination (D = 0.95), 16 types, and showed good reproducibility. This non-radioactive method demonstrates the three important features of a typing system; discrimination, typability and reproducibility.

The lectin type of Candida albicans--an epidemiological marker relevant to pathogenesis

Fifty Candida albicans strains isolated from the oral cavities of HIV-infected patients were typed with 14 different lectins by means of agglutination reactions. Sixteen different lectin types could be distinguished, the most frequent type representing 22% of strains. A change in the lectin type was found in about half of the Candida albicans strains representing control cultures from identical individuals. A simplified typing scheme based on three lectins seems to be almost as efficacious for epidemiological application.

Novel plasmid combinations in Haemophilus ducreyi isolates from Thailand

Thirty isolates of Haemophilus ducreyi collected in Thailand in 1984 were characterized by plasmid content. Three novel plasmids with estimated molecular masses of 1.8, 2.6, and 2.8 MDa were observed in 29 isolates, in addition to the 3.2-, 5.7-, and 7.0-MDa beta-lactamase and 4.4-MDa sulfonamide resistance plasmids. At least three of the seven plasmids were observed in each of the 29 isolates. The number and diversity of plasmids observed in these isolates of H. ducreyi distinguish them from strains previously described.

Molecular characterization of Haemophilus ducreyi by ribosomal DNA fingerprinting

Intraspecies genotypic heterogeneity among Haemophilus ducreyi isolates was examined by using genomic fingerprints with rRNA from Escherichia coli as a probe. DNA from 44 isolates of H. ducreyi was digested by restriction endonuclease HincII or HindIII, separated by agarose gel electrophoresis, transferred to nylon membranes, and hybridized with 32P-labeled 16S and 23S rRNA. HincII digests yielded four hybridization patterns (ribotypes), whereas HindIII digests yielded eight ribotypes. Four HincII and five HindIII ribotypes were observed among 14 H. ducreyi isolates collected within a period of 1 month in Kenya, where chancroid is endemic. In contrast, one HincII and two HindIII ribotypes were observed among 28 isolates collected during the Orange County, Calif., chancroid epidemic that occurred in 1981 and 1982. The plasmid content, in conjunction with ribotyping, provided additional differentiation among some isolates of H. ducreyi. This study demonstrates that ribotyping of H. ducreyi may be used to study the epidemiology of chancroid.

Biology of Haemophilus ducreyi

The etiological agent of the sexually transmitted genital ulcer disease chancroid was first described in 1889 by Auguste Ducrey following repeated autoinoculation of purulent ulcer material from a series of patients. The organism was isolated on artificial media a decade later but has remained difficult to isolate consistently, resulting in controversy over its characteristics and role as the causative agent of chancroid. Because of its fastidious growth requirements, including unknown components in blood, the organism was included in the original description of the genus Haemophilus. Requirement for exogenous hemin and limited phenotypic characteristics, including structural and antigenic properties, suggested that Haemophilus ducreyi was a valid member of the genus Haemophilus. Recent studies of respiratory quinones, deoxyribonucleic acid hybridization, and competition for homologous transformation of the type species, H. influenzae, suggest that H. ducreyi is unrelated to any of the present species of the family Pasteurellaceae, which includes members of the genera Haemophilus, Actinobacillus, and Pasteurella. This review summarizes the early studies with H. ducreyi and our current knowledge of the microbiology of this important human pathogen.