Population structure and geographical subdivision of the Leishmania major vector Phlebotomus papatasi as revealed by microsatellite variation

Multi-locus microsatellite typing (MLMT) has been employed to infer the population structure of Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) sandflies and assign individuals to populations. Phlebotomus papatasi sandflies were collected from 35 sites in 15 countries. A total of 188 P. papatasi individuals were typed using five microsatellite loci, resulting in 113 different genotypes. Unique microsatellite signatures were observed for some of the populations analysed. Comparable results were obtained when the data were analysed with Bayesian model and distance-based methods. Bayesian statistic-based analyses split the dataset into two distinct genetic clusters, A and B, with further substructuring within each. Population A consisted of five subpopulations representing large numbers of alleles that were correlated with the geographical origins of the sandflies. Cluster B comprised individuals collected in the Middle East and the northern Mediterranean area. The subpopulations B1 and B2 did not, however, show any further correlation to geographical origin. The genetic differentiation between subpopulations was supported by F statistics showing statistically significant (Bonferroni-corrected P < 0.005) values of 0.221 between B2 and B1 and 0.816 between A5 and A4. Identification of the genetic structure of P. papatasi populations is important for understanding the patterns of dispersal of this species and to developing strategies for sandfly control.

Genetic structure of Mediterranean populations of the sandfly Phlebotomus papatasi by mitochondrial cytochrome b haplotype analysis

Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) is the main vector of Leishmania major Yakimoff & Schokhor; which is the cause of self-limiting cutaneous leishmaniasis in the Old World. This sandfly is found in houses, animal shelters, caves and rodent burrows. It has a large geographical range, which includes the Middle East and the Mediterranean regions. A population analysis of colony and field specimens of P. papatasi was conducted on 25 populations originating from 10 countries. The distribution of haplotypes of the maternally inherited mitochondrial cytochrome b gene were analysed to assess the population differentiation of P. papatasi. Alignment of a 442-basepair region at the 3' end of the gene identified 21 haplotypes and 33 segregating sites from 131 sandflies. The pattern of sequence variations did not support the existence of a species complex. The median-joining network method was used to describe both the origin of the haplotypes and the population structure; haplotypes tended to cluster by geographical location, suggesting some level of genetic differentiation between populations. Our findings indicate the presence of significant population differentiation for populations derived from Syria, Turkey, Palestine, Israel, Jordan and Egypt. Knowledge of population differentiation among P. papatasi populations is important for understanding patterns of dispersal in this species and for planning appropriate control measures.

Clinical diagnosis of cutaneous leishmaniasis: a comparison study between standardized graded direct microscopy and ITS1-PCR of Giemsa-stained smears

Parasitological diagnosis of cutaneous leishmaniasis is absolutely necessary before treatment. Direct microscopy of scrapings taken from the margins of skin lesions is the most commonly used method for clinical diagnosis of leishmaniasis. In this study to evaluate the usage of stained smears as samples for PCR and the possible advantage of PCR, we compared the sensitivity of the diagnosis of Giemsa-stained skin scrapings by standardized graded direct microscopy with that of ITS1-PCR with the material of the same area of the slide. Three 5mm x 5mm squares were marked on each of the 20 Giemsa-stained touch smears from 20 clinically diagnosed Palestinian patients. Out of the 60 squares scanned for amastigotes under 100x oil-immersion light microscopy, 45 (75%) gave usable results and 23 of these were positive for Leishmania. Fifteen (25%) squares could not be scanned microscopically, 12 because of staining that was too thick and 3 because of inadequate staining. DNA from each scanned square was extracted separately after microscopy and run through ITS1-PCR. Of the 23 microscopy-positive squares, 20 (87%) of these were positive by PCR. Of the three that were negative, one failed to extract for DNA, the second showed only one amastigote in the entire square, and the third was normally graded as +1 but was not amplified for unknown reasons. Of the 22 squares negative for microscopy, 18 (82%) were ITS1-PCR positive. Additionally, all three improperly stained squares were ITS1-PCR positive. Of the 12 darkly stained squares, 11 were positive. A negative control group of 15 German individuals from which Giemsa-stained slides containing three squares each was prepared and these slides were also microscopically scanned and tested by ITS1-PCR. Both tests were negative with both methods. Compared to microscopy (data in parenthesis), PCR showed a sensitivity of 87% (37%) and a specificity of 100% (100%). We have concluded that Giemsa-stained smears are a readily usable sampling method for PCR and that ITS1-PCR is far more sensitive than microscopy.

Origins of microsatellite diversity in the Trichophyton rubrum-T. violaceum clade (Dermatophytes)

We analyzed the population structure of the anthropophilic dermatophyte species Trichophyton violaceum, which mainly causes tinea capitis, and T. rubrum, the most frequently isolated agent of dermatophytosis worldwide. A microsatellite marker (T1) was developed by using the enrichment technique for microsatellites. The T1 marker containing a (GT)(8-10) repeat was proven to specifically amplify both species, underlining their close kinship. Four polymorphic alleles were detected within a set of about 130 strains by using polyacrylamide gel electrophoresis with this marker. An association with geographic origin of the isolates was apparent. Given the close relatedness of both species, these data suggest an African origin of the entire T. rubrum complex, followed by the emergence of a new genotype (B) in Asia with subsequent spread of this genotype over Europe and the United States.

The recent emergence of Leishmania tropica in Jericho (A'riha) and its environs, a classical focus of L. major

Between 1997 and 2002, 49 strains of Leishmania were isolated from the cutaneous lesions of Palestinians living in and around Jericho. A polymerase chain reaction (PCR) amplifying the ribosomal internal transcribed spacer 1 (ITS1-PCR) was applied to their cultured promastigotes and to 207 individuals' skin scrapings spotted on filter-papers, 107 of which proved positive for leishmanial DNA. Species identification was performed by restricting the ITS1-PCR amplification products from the cultured promastigotes and the amastigotes in the scrapings with the endonuclease HaeIII. Of the 49 cultures, 28 (57%) were L. major and 21 (43%) were L. tropica. Of the 107 dermal samples tested directly, 53 (49.5%) were infected with L. major, 52 (48.5%) with L. tropica and two remained unidentified. This is the first time L. tropica has been exposed in the population of the Jericho area and on such a large scale. The itinerant behaviour of some of this population precludes categorically declaring that L. tropica has recently become established in this classical focus of L. major. For this and although 88.2% of the cases of L. tropica claimed not to have travelled out of the vicinity of Jericho, local infected sand fly vectors of L. tropica must be caught, identified and, if possible, shown to harbour infections, and, if one exists, an animal reservoir host should also be exposed to endorse whether the cases caused by L. tropica were imported or autochthonous.

Molecular epidemiology and population genetics in Leishmania

Polymorphic DNA sequences have been amplified using different PCR-based techniques and used for species identification, strain discrimination and population genetic studies in Leishmania. A PCR fingerprinting method that uses single non-specific primers generates species-specific banding patterns with some intraspecies variation. This approach can be used to identify Leishmania species and also to discriminate strains of different Leishmania species. Cultivation of the parasites is, however, mandatory. PCR-restriction fragment length polymorphism of the internal transcribed spacer (ITS) in the ribosomal operon differentiates all Leishmania species, except members of the L. donovani and L. brasiliensis complexes. ITS-single-strand conformation polymorphism or ITS sequencing can detect strain specific-variation (except in L. infantum); culturing is not required. Species of Leishmania exhibit different degrees of genetic variation (L. tropica > L. aethiopica > L. major > L. donovani). Population analysis using co-dominant DNA markers developed by sequence-confirmed amplified region analysis revealed a primarily clonal structure in a L. donovani population from Sudan and suggested that occasional recombination events may occur in this population.

[Genetic structure of geographically different populations of candida albicans]

Codominant single-locus markers were developed by amplifying genomic DNA of C. albicans with pairs of random primers. Monomorphic PCR products were screened for polymorphisms by the SSCP technique. Sequencing confirmed that SSCP's were mostly due to single nucleotide substitutions in the polymorphic fragments. A total of 85 polymorphic loci were observed within 13 PCR fragments. Populations from Africa displayed less genotype variation than the populations from Europe and USA. Two genetically similar African C. albicans populations exhibiting an atypical biotype were strictly clonal and perhaps represent a geographically distributed clone. Analyses of "typical" C. albicans populations of different geographical origin provided however evidence for both clonality and recombination. Evidence for clonality was supported by the absence of segregation genotypes, and by deviation of genotypic frequencies from Hardy-Weinberg expectations. Tests for nonrandom association of alleles across loci revealed less evidence for linkage disequilibrium than expected for strictly clonal populations. Although all C. albicans populations tested were primarily clonal, evidence for recombination suggests that sexual reproduction or some other form of genetic exchange occurs in this species.

Strain specificity of yeasts isolated from different locations of women suffering from vaginal candidosis, and their partners

Sexual partners often harbour identical yeast strains in the vagina, in the orointestinal tract and in semen in cases of recurrent vulvovaginal candidoses. Specimen were collected from vagina, oral cavity and faeces of the patients, and from semen, oral cavity and faeces of their male partners. Mycological cultures were grown on Sabouraud glucose-agar and, if positive, specified by Candida-ID-Agar (BioMérieux), by formation of chlamydospores on rice agar, and by biochemotyping with the System Walkaway (Dade) or the API-32C system (BioMérieux). A polymerase chain reaction finger-printing technique with the T3B oligonucleotide as single primer was used for strain typing. Candida albicans was isolated from the vagina of 18 out of 21 patients, the vagina of one patient harboured a strain of Candida glabrata. The cultures obtained from vagina, oral cavity and faeces were genetically identical in 12 patients. From the partners of 15 patients C. albicans was cultured in at least one of the clinical samples. Identical strains were observed for eight of 15 couples, whereas four of these identical strains were cultured from semen. Further prospective investigations will prove whether a consequent treatment of both partners will eradicate identical yeast strains and will be able to improve the results of treatment in such women.

Genetic heterogeneity in the species Leishmania tropica revealed by different PCR-based methods

A PCR fingerprinting approach, using single non-specific primers, as well as restriction and single-strand conformation polymorphism (SSCP) analyses of the amplified ribosomal internal transcribed spacer, were used to investigate genetic variability in the species Leishmania tropica. Twenty-nine strains of the 'L. tropica complex' from different Old World geographical areas were studied including 4 from Namibia, and 1 strain of L. killicki. All techniques revealed a high degree of genetic heterogeneity among the strains of L. tropica. The PCR fingerprinting displayed the highest discriminatory power, but can be applied only to cultured parasites. The internal transcribed spacer (ITS) region can be amplified directly from infected clinical samples and analysed subsequently. No strict correlation was discerned between the genetic variants and either the geographical origin of the strains or the clinical manifestations associated with human disease, except for the Namibian strains. Also, genetic variation did not correlate well with characterization by enzyme variant electrophoretic analysis. The strain of L. killicki always clustered together with the strains of L. tropica, suggesting it, probably, should not be considered a separate species of Leishmania. However, the 4 Namibian strains formed a distinct, statistically well-supported group closely related to but different from the other strains of L. tropica.

Application of flow cytometry and microscopical methods to characterize the effect of herbal drugs on Leishmania Spp

The World Health Organization has identified leishmania sis as a major public health problem, particularly in Africa, Asia, and Latin America. About 1.5 to 2 million people are affected annually by this parasitic infection. As there is no vaccine, there is still a strong need for sufficient drugs. In a preliminary screening, extracts of 50 different plants were evaluated for their possible leishmanicidal activity against the promastigote form of Leishmania mexicana amazonensis. Eighteen extracts showed at least 50% inhibition at 100 microg/ml. The ethanolic extract from Yucca filamentosa L. showed the strongest leishmanicidal activity (100% inhibition at 5 microg/ml). The bioactivity-guided fractionation of this extract led to the isolation of three main components (Yuccasaponins MC 1--3). In further experiments, the effect of Yuccasaponin MC 3 on the promastigote form of L. mexicana amazonensis was quantified and characterized using flow cytometry and specific fluorescent dyes [propidium iodide, Syto 9, and DiBAC(4)(3)]. The data revealed that the membrane of the promastigote is attacked. The effect of Yuccasaponin MC 3 on intracellular forms (amastigote) was also characterized; green fluorescent protein-transfected Leishmania major were used. By this method, an inhibition of intracellular growth of L. major was demonstrated. This paper shows that, together, flow cytometry and microscopy are quick, sensitive, and easily reproducible methods to describe the effects of drugs on parasites.

An epidemic of tinea corporis caused by Trichophyton tonsurans among children (wrestlers) in Germany

An outbreak of tinea corporis due to Trichophyton tonsurans among 46 children (aged 7-17 years) was investigated. Most of them were wrestlers. Thirty-one strains were identified by conventional methods, but proved to be problematic in 15 isolates due to colony variation and reduced sporulation. They were identified as Trichophyton tonsurans by the use of molecular methods, for example, sequence comparison of the ribosomal internal transcribed spacer (ITS) region and polymerase chain reaction fingerprinting. No DNA polymorphisms were detected with any of the techniques used, suggesting clonal reproduction of the populations of the species and providing evidence for spatial and temporal stability of the lineage.

Molecular taxonomy of the Trichophyton rubrum complex

The validity of taxa around Trichophyton rubrum was evaluated by a combination of phenetic and molecular methods. Morphological and physiological features were compared to results of sequencing of the internal transcribed spacer region of the ribosomal operon, PCR fingerprinting, and amplified fragment length polymorphism analysis. The 15 species and varieties investigated (Trichophyton circonvolutum, Trichophyton fischeri, Trichophyton fluviomuniense, Trichophyton glabrum, Trichophyton gourvilii, Trichophyton kanei, Trichophyton kuryangei, Trichophyton megninii, Trichophyton pedis, Trichophyton raubitschekii, Trichophyton rodhaini, Trichophyton rubrum var. nigricans, Trichophyton soudanense, Trichophyton violaceum var. indicum, and Trichophyton yaoundei) were reclassified or synonymized as T. rubrum or T. violaceum.

Genetic heterogeneity of ribosomal internal transcribed spacer in clinical samples of Leishmania donovani spotted on filter paper as revealed by single-strand conformation polymorphisms and sequencing

A polymerase chain reaction and single-strand conformation polymorphism determination (PCR-SSCP) was used to detect deoxyribonucleic acid sequence polymorphisms in the transcribed non-coding regions between the small and large sub-unit ribosomal ribonucleic acid (rRNA) genes in Leishmania donovani from 63 clinical samples collected in eastern Sudan, between April 1997 and October 1998. Specific Leishmania primers were used to amplify the internal transcribed spacer (ITS) regions of L. donovani isolates directly from clinical samples spotted on filter papers. Amplification products were subsequently analysed by SSCP. Eleven polymorphic patterns were detected in the first part of the spacer, the ITS1 region, and were sequenced. Most of the changes were due to deletions of adenine bases and AT pairs within the first 192 nucleotides of the ITS region. This is the first application of PCR-linked SSCP analysis for the detection of population variation with direct display of sequence variation in parasitologically positive clinical samples spotted on filter paper. Culturing the parasite is thus not required, which is beneficial particularly in epidemiological studies based on field work where obtaining cultures can be extremely difficult.

Molecular and conventional taxonomy of the Microsporum canis complex

The validity of taxa around Microsporum canis was evaluated by a combination of phenetic and molecular methods. Morphological and physiological features were compared with results of sequencing of the internal transcribed spacer (ITS) region of the ribosomal operon, polymerase chain reaction (PCR) fingerprinting and amplified fragment length polymorphism (AFLP) analysis. The seven species investigated seem to be infraspecific taxa and were reclassified or synonymized as M. canis (teleomorph: Arthroderma otae), M. ferrugineum, and M. audouinii.

Genetic variability within the species Leishmania aethiopica does not correlate with clinical variations of cutaneous leishmaniasis

Leishmania aethiopica infections in man result in a spectrum of diseases from LCL to DCL. These clinical manifestations have been attributed to genetic differences within the host or the parasites. In this study two different PCR-based methods were used to elucidate genetic variation within the species L. aethiopica. Inter- and intra-specific variations were detected in the ITS of the ribosomal operon in different strains and species of Leishmania, using a PCR-RFLP approach, and by a PCR fingerprinting technique that used single non-specific primers to amplify polymorphic regions of the genomic DNA. Both methods revealed genetic heterogeneity among ten L. aethiopica isolates examined. Unrooted distance trees separated the ten strains into two different genetic groups. This subdivision was correlated to the geographical origin of the isolates rather than to the clinical manifestation of the disease.

Assessment of genetic relatedness of vaginal isolates of Candida albicans from different geographical origins

PCR fingerprinting with single non-specific primers was used to type vaginal isolates of C. albicans from Portugal, Angola, Madagascar, and two regions of Germany (Berlin and Munich). In addition to analysing isolates that exhibited the normal biotype of C. albicans, the study included atypical strains that failed to assimilate glucosamine and N-acetylglucosamine, which were isolated from women in Angola and Madagascar. A total of 212 strains of C. albicans were studied, representing 87 different multi-locus genotypes. The genotypes of strains from each geographical population were highly similar but not identical. There was one exception: a strain from Portugal grouped with the typical strains from Angola. The typical and especially the atypical populations from Africa displayed less genotype variation than the populations from Europe. The Portuguese samples exhibited the greatest genotypic heterogeneity. Distance analysis (UPGMA) revealed a statistically weak correlation between genotype and geographical origin of the C. albicans isolates.

Molecular markers reveal exclusively clonal reproduction in Trichophyton rubrum

Genotypic variability among 96 Trichophyton rubrum strains which displayed different colony morphologies and were collected from four continents was investigated. Twelve markers representing 57 loci were analyzed by PCR fingerprinting, amplified fragment length polymorphism, and random amplified monomorphic DNA markers. Interestingly, none of the methods used revealed any DNA polymorphism, indicating a strictly clonal mode of reproduction and a strong adaptation to human skin.

Molecular taxonomy of Trichophyton mentagrophytes and T. tonsurans

Most members of the anamorph genus Trichophyton are anthropophilic and have evolved with the human host. Classical parameters for the identification of dermatophytes include clinical features, cultural characteristics, conidial morphology and physiological test results. Phenotypic variability and pleomorphism due to culturing on artificial media is common among this group of organisms and has led to the description of numerous species. The validity of taxa around T. mentagrophytes and T. tonsurans was verified. Morphological and physiological features were compared to results of three different molecular techniques (sequencing of the internal transcribed spacer (ITS) region of the ribosomal operon, PCR fingerprinting and amplified fragment length polymorphism (AFLP) analysis). Twenty-four species or varieties investigated could be reduced to five taxa and were reclassified or synonymized as Trichophyton tonsurans, T. interdigitale, T. mentagrophytes, T. simii and T. erinacei.

Toxoplasma gondii infection: analysis of serological response by 2-DE immunoblotting

Toxoplasma gondii is known to cause a variety of diseases ranging from asymptomatic infections to serious conditions in immunocompromised hosts such as AIDS-patients or transplant recipients. In addition they may cause abortion or fetal abnormalities during pregnancy. Despite the clinical importance, diagnosis, treatment and prevention still remain unsatisfactory. Analysis of the parasitic cell determinants, recognized by specific humoral and cellular immune responses, may have important implications for diagnosis, therapy and vaccination strategies. Two-dimensional electrophoresis (2-DE) was used to resolve and compare protein patterns from Toxoplasma gondii strains RH and BK (mouse virulent strains). Comparison of silver-stained gels showed that 35.2% to 60.3% of the spots had the same position. In a second series of experiments, the reactivity of the spots with human sera was tested. Proteins were transferred to PVDF membranes and were detected with sera from different patient groups. Depending upon the immunoglobulin class (IgG, IgM, IgA or IgE) different epitope patterns were observed. Some of the spots seemed to be recognized in different stages of infection. Sera of two patients with similar serology and comparable stage of infection were compared in order to demonstrate an individual immune response.

Development of an oligonucleotide probe specific for Trichophyton rubrum

A species-specific DNA probe was developed to detect the dermatophyte species Trichophyton rubrum. The selected oligonucleotide sequence is derived from the highly variable internal transcribed spacer 2 region of the ribosomal DNA operon. The specificity of the non-radioactive labelled oligonucleotide probe was tested against related dermatophytes, other eukaryotic microorganisms and against human DNA. No cross-hybridization was found, and hybridization signals were invariably detected in all T. rubrum strains investigated. In addition, no homologous sequences were found searching the EMBL database. Experiments to establish a method for isolating DNA directly from clinical specimens gave successful amplification and hybridization products in about 30% of the samples.

Phylogeny and taxonomy of the family Arthrodermataceae (dermatophytes) using sequence analysis of the ribosomal ITS region

The internal transcribed spacer (ITS) region, covering the ITS1, ITS2 and 5.8S ribosomal DNA was used to evaluate phylogenetic relationships within the fungal family Arthrodermataceae. Sequences of variable length, ranging between 522 and 684 base pairs were aligned. An unrooted consensus tree based on parsimony analysis showed Trichophyton to be polyphyletic, and Microsporum to be paraphyletic. Non-monophyly of these two genera is in conflict with traditional classification. But this relation is not strongly supported by bootstrap analysis. Phylogenetic analysis showed that the two known members of the genus Epidermophyton grouped widely apart from each other. Within Trichophyton, our results suggest a separation of human pathogenic species and primarily geophilic species. Bootstrap support for these two groups is fairly high and both groups are recognized by current taxonomy. Three lineages were revealed within the T. mentagrophytes species complex. Microsporum canis, M. audouinii and M. equinum were found to be closely related. The topology of the tree was robust to various methods of analysis (parsimony and distance) and a different weighting scheme. Weighting of transversions over transitions did not improve the status of poorly supported branches of the tree.

Toxoplasma infection and cell free extract of the parasites are able to reverse multidrug resistance of mouse lymphoma and human gastric cancer cells in vitro

A large number of compounds are known to reduce the ATP-dependent efflux pump activity of multidrug resistant (mdr) tumor cells. Here we report that an infection of cancer cells with T. gondii reduced the multidrug resistance of the tumour cells against cytostatic drugs. Two mouse lymphoma cell lines (Mdr L 5718 and Par 5718) were infected with Toxoplasma gondii in vitro and the reduction of efflux pump activity of the cells was measured. The drug accumulation (Rhodamin-123) was increased in the infected mdr cell lines compared with non- infected mdr-cells, and no effect was shown after infection of the parental cell line. The same effect was also achieved by incubation of Mdr-tumor cells with cell lysate of Toxoplasma gondii. Mdr-1-gene expression was reduced in the infected cell lines 48 hours after infection. Co-cultivation of Toxoplasma gondii with mdr cell lines separated by a microfilter from tumor cells was performed, but this cocultivation did not change the mdr efflux activity. The effect of Toxoplasma gondii infection on the efflux pump activity and mdr-1 gene expression was also examined in the human gastric cancer cells. A sensitization of resistant gastric cancer cells was also achieved by parasite infection. This phenomenon is an evidence that a reduction of resistance in tumor cells can be achieved by a natural parasite infection. It is as yet unclear whether an active infection or another substance of T. gondii is responsible for this phenomenon.

Mixed infection of human U-937 cells by two different species of Leishmania

Mixed infections by different Leishmania species could explain differences in the clinical course of these infections. Moreover, mixed infections of the same macrophage could be the basis for parasite recombination. We stained three strains of Leishmania (L. mexicana amazonensis, L. donovani DD8, and L. infantum D2, respectively) with different fluorescent dyes and analyzed them using a fluorescence-activated cell scanner. The simultaneous infection of one cell by Leishmania belonging to two different species was demonstrated. In additional experiments, cells with mixed infections were separated by a fluorescence-activated cell sorter and monitored for 24 hr. Preinfecting human monocytic U-937 cells with one Leishmania species did not exclude a second species added after 3 hr.

Identification of common dermatophytes (Trichophyton, Microsporum, Epidermophyton) using polymerase chain reactions

Polymerase chain reaction (PCR) fingerprinting detected DNA polymorphisms among frequently isolated species and strains of the genera Trichophyton, Microsporum and Epidermophyton. The patterns generated by this DNA-based method permitted species and strains to be identified. The conventional methods to identify dermatophytes rely on the expression of characteristic morphological features, as well as several physiological properties. Identification is often delayed or problematic because isolates may be slow to form conidia or produce atypical microscopic structures or colony appearances. Using non-specific primers such as (AC)10, (GTG)5, M13 core sequence and AP3, characteristic PCR profiles were generated for 17 species. Intraspecies variables were also observed for four of six varieties of T. mentagrophytes, whereas no detectable DNA variability was found within the three varieties of T. tonsurans. Comparing species-specific PCR fingerprints of clinical isolates with those of type strains, species could be identified by their PCR fingerprints, even if they could not be identified by the accepted phenotypic characteristics.

Occurrence of S and F1C/S-related fimbrial determinants and their expression in Escherichia coli strains isolated from extraintestinal infections

The presence of S and F1C/S-related fimbrial determinants was determined in 462 E. coli strains obtained from different extraintestinal infections and in 162 control isolates of E. coli by using two different DNA probes: an oligonucleotide probe consisting of three oligonucleotides that bind specifically to the S adhesin gene and a polynucleotide probe which is not able to distinguish between S, F1C, and S-related sequences. The expression of S and F1C phenotypes was tested by dot enzyme immunoassay with the corresponding monoclonal antibodies. S fimbriae genotypes were observed more frequently in septic (25%) and urinary (12%) isolates of E. coli than in faecal and water isolates (1%) and often occurred together with O2, O6, O18 and O83 antigens. F1C/S-related fimbrial DNA was detected with a higher frequency in UTI isolates (26%) than in septic (16%) and faecal (10%) isolates and was most frequently associated with O4, O6, and O75 serotypes. Since the production of S and F1C fimbriae was comparatively rare in all clinical and control isolates of E. coli, DNA hybridization assays which allow the sensitive and specific detection of fimbrial determinants even in the absence of their expression are preferable to phenotypic assays.

Genotypic and phenotypic determination of five virulence markers in clinical isolates of Escherichia coli

The presence of the virulence markers K1 capsule, serum resistance, aerobactin, S and P/PR fimbriae were examined in a total of 395 E. coli strains from different extraintestinal infections and in 81 faecal isolates of healthy volunteers using specific DNA probes and classical phenotypic methods. All markers were more frequently detected when genotypic assays were applied. The simultaneous occurrence of 3-4 virulence determinants was typical for isolates derived from patients with septicaemia or meningitis. Isolates from blood cultures and cerebrospinal fluid were expressing the virulence phenotypes to a greater extent than isolates from urine or faeces. The use of colony hybridization with specific oligonucleotide and polynucleotide probes for the detection of virulence determinants has been proven to be more specific and reliable than phenotypic approaches.

Molecular markers reveal that population structure of the human pathogen Candida albicans exhibits both clonality and recombination

The life history of Candida albicans presents an enigma: this species is thought to be exclusively asexual, yet strains show extensive phenotypic variation. To address the population genetics of C. albicans, we developed a genetic typing method for codominant single-locus markers by screening randomly amplified DNA for single-strand conformation polymorphisms. DNA fragments amplified by arbitrary primers were initially screened for single-strand conformation polymorphisms and later sequenced using locus-specific primers. A total of 12 single base mutations and insertions were detected from six out of eight PCR fragments. Patterns of sequence-level polymorphism observed for individual strains detected considerable heterozygosity at the DNA sequence level, supporting the view that most C. albicans strains are diploid. Population genetic analyses of 52 natural isolates from Duke University Medical Center provide evidence for both clonality and recombination in C. albicans. Evidence for clonality is supported by the presence of several overrepresented genotypes, as well as by deviation of genotypic frequencies from random (Hardy-Weinberg) expectations. However, tests for nonrandom association of alleles across loci reveal less evidence for linkage disequilibrium than expected for strictly clonal populations. Although C. albicans populations are primarily clonal, evidence for recombination suggests that sexual reproduction or some other form of genetic exchange occurs in this species.

Identification and determination of the relationships of species and strains within the genus Leishmania using single primers in the polymerase chain reaction

DNA polymorphisms were assessed in different species and strains within the genus Leishmania by amplifying genomic DNA with single non-specific primers. This polymerase chain reaction (PCR) method employed non-random primers which anneal to mini- and microsatellite DNA sequences like the M13 core sequence and the simple repeat sequences (GTG)5 and (GACA)4, and the T3B primer derived from an intergenic spacer for tRNA genes. Distinctive and reproducible sets of amplified DNA fragments were obtained for all Leishmania isolates tested. The number and size of amplification products were found to be characteristic for a given taxon. Highly similar PCR profiles were observed when genomic DNA of representatives of the L. donovani, L. mexicana or L. braziliensis complexes was amplified. By comparing PCR patterns of unidentified Leishmania isolates with those obtained from reference strains it was possible to identify these isolates at the species level. The information of the amplification patterns was used for the construction of phylogenetic trees to measure the genetic relatedness within the genus Leishmania.

Rapid identification of Candida species by DNA fingerprinting with PCR

DNA polymorphisms in different species and strains of the genus Candida were assessed by amplifying genomic DNA with single nonspecific primers. This PCR method employed an arbitrary primer (the 10-mer AP3), a primer derived from the intergenic spacer regions (T3B), and the microsatellite primers (GTG)5 and (AC)10. Distinctive and reproducible sets of amplification products were observed for 26 different Candida and 8 other fungal species. The numbers and sizes of the amplification products were characteristic for each species. All yeast species tested could be clearly distinguished by their amplification patterns. With all primers, PCR fingerprints also displayed intraspecies variability. However, PCR profiles obtained from different strains of the same species were far more similar than those derived from different Candida species. By comparing species-specific PCR fingerprints of clinical isolates with those of reference strains, clinical isolates could be identified to the species level even if they could not be identified by routine biochemical methods.

Phenotypic and genotypic characterization of unusual vaginal isolates of Candida albicans from Africa

As expected by its global prevalence, the most frequently isolated species of yeast from vaginal swabs obtained from patients in Africa was Candida albicans, which accounted for 53 of 85 (62.4%) of the isolates from women in Madagascar and 35 of 54 (64.8%) of the culture-positive women in Angola. However, 40% of the Madagascan and 23% of the isolates from Angola, as well as two isolates obtained from one German patient, were not able to utilize the amino sugars glucosamine and N-acetylglucosamine as the sole carbon source. These isolates were able to form germ tubes but did not form chlamydospores. The correct identification as C. albicans was made possible only by using a PCR-based method of DNA fingerprinting. Only minor phenotypic and genotypic variation was observed among these strains. Whether they represent a distinct clone that is found mainly in Africa is not clear. The relevance of the amino sugar catabolic pathway in C. albicans is discussed in view of these results.

Combined factor and QSAR analysis for antibacterial and pharmacokinetic data from parallel biological measurements

Antibacterial potency data for a variety of bacterial strains and pharmacokinetic parameters of naphthyridines taken from the literature were submitted to factor and QSAR analyses. Factor analysis of antibacterial potencies unraveled a distinct data structure. The information obtained about the internal relatedness of tests can be used in QSAR analyses and reflects itself in the QSAR results. Factor analysis of pharmacokinetic data also led to a clear grouping of measurements with a strong relationship of half life time and urinary recovery, respectively, with log D.

[New chemotherapeutics against malarial parasites]

New findings on the molecular biology of plasmodia have led to new approaches for the development of chemotherapeutics. Trials to circumvent the relative toxicity of individual substances by a combination of active agents have been successful in several cases, and there will be more of those combinations in the future. An additional advantage of combinations can be the improvement of activity. In some cases, antiparasitic side effects of long known drugs with low toxicity such as imipramine can be used to decrease or overcome resistance. And, last but not least, ideas or in some cases new drugs will come from the traditional medicine.

Epidemiological study of an Acinetobacter baumannii outbreak by using polymerase chain reaction fingerprinting

A polymerase chain reaction (PCR) technique was applied to the fingerprinting of different strains of Acinetobacter baumannii from a cluster of patients infected or colonized with the incriminated pathogen. The DNA was extracted by boiling and was subjected to PCR amplification by using the core sequence of the M13 phase as a single primer. The amplified products were separated by agarose gel electrophoresis and were detected by staining with ethidium bromide. In 1990, 49 multiresistant A. baumannii strains were isolated from 13 patients from the same intensive care unit of the Charité Hospital; 45 of these outbreak isolates obtained from 12 patients showed the same PCR patterns, indicating an epidemiological relatedness of these strains. Four strains isolated from the same patient belonged to another genetic group, as revealed by a distinct amplification pattern. Another single subtype of A. baumannii was identified as the causative agent in patients during a second outbreak at a different intensive care unit in the same hospital. Seventeen isolates recovered from 10 immunocompromised patients had the same amplification patterns, which were distinct from all other PCR profiles. Five strains were obtained from two other hospitals; three isolates from the hospital of Magdeburg, Germany, had identical PCR patterns which, however, could be clearly distinguished from the patterns of all other strains. The remaining two isolates displayed individual patterns of amplified fragments. PCR fingerprinting may provide a useful and particularly rapid identification technique for epidemiological investigations of nosocomial infections.

Identification of clinical strains of Candida albicans by DNA fingerprinting with the polymerase chain reaction

DNA polymorphisms generated by the polymerase chain reaction (PCR) were used to differentiate clinical isolates of Candida. This PCR method employed single primers that were originally designed as hybridization probes for DNA fingerprinting experiments to probe minisatellite and microsatellite DNA sequences. To evaluate this procedure, 35 isolates from 20 patients in several intensive care units and 12 isolates obtained from the oral cavities of healthy dental patients were fingerprinted. The PCR-fingerprint patterns of isolates of Candida albicans from the immunocompromised patients revealed fewer differences than isolates from the dental service. Multiple isolates from different body sites of the same patients revealed that patients may harbour isolates of Candida with the same or different PCR-fingerprints. Since this method is generally simpler and faster than established methods of biotyping medically important yeasts, PCR-fingerprinting may prove useful for the surveying of large numbers of pathogens for epidemiological studies.

Inhibition of the growth of Plasmodium falciparum and Plasmodium berghei in vitro by an extract of Cochlospermum angolense (Welw.)

An extract of Cochlospermum angolense (Welw.) is used in the traditional medicine of Angola for the therapy of icterus and for the prophylaxis of malaria. From the roots of this plant red crystalline substances have been isolated and tested for their effect on Plasmodium falciparum in vitro and on the DNA and protein synthesis of Plasmodium berghei. The multiplication of P. falciparum was decreased to 50% of the control in the presence of 10 micrograms/ml extracted material and there was a total inhibition at a concentration of 50 micrograms/ml. If mice erythrocytes infected by P. berghei were incubated for 6 h with 25 micrograms/ml of the extract DNA synthesis was depressed to nearly background level. And, even more important, this effect could be demonstrated immediately. On the contrary, protein synthesis continued for at least 90 min at a reduced rate and stopped then. The results obtained show the direct antiparasitic effect of the substances extracted from C. angolense. The activity seems to be directed against DNA synthesis.

Determination of S Fimbriae Among Escherichia coli Strains from Extraintestinal Infections by Colony Hybridization and Dot Enzyme Immunoassay

449 E. coli strains obtained from septic infections (124 isolates), urinary tract infections (246) and water (79) were surveyed for S/F1C fimbrial DNA by DNA hybridization and for expression of S fimbriae by enzyme immunoassay. S/F1C fimbrial DNA was detected with greater frequency in septic (35%) and urinary (43%) isolates than in water isolates and was often associated with the O2, O4, O6, O18, O83, and O156 serogroups. Most O45 strains did not possess such sequences. Only 12% and 28%, respectively, of the septic and urinary strains possessing S/F1C fimbrial DNA expressed S fimbriae.

[The effect of an extract from Cochlospermum angolense ("Burututu") on Plasmodium berghei in the mouse malaria suppression test]

Often existing cross-resistance to structure analogous antimalarials causes the need to find new active compounds against malaria parasites. For this purpose the traditional medicine of tropical countries has proved to be a treasury. A root extract of Cochlospermum angolense showed in vitro a remarkable activity against Plasmodium berghei in the DNA synthesis measurement with 3H-labelled hypoxanthine. This effect could be reproduced under in vivo conditions with the "4-day suppressive test" of rodent malaria.

[Experience and problems with biochemical differentiation of Enterobacteriaceae with microtiter plates]

A self-made miniaturized test system for the biochemical identification of enterobacteriaceae in microtitre plates has been examined. Special emphasis was laid on easy and unequivocal interpretation of the reactions. This was achieved among other things by including further sugar fermentations. Applying a corresponding reaction matrix it is possible to get clear identifications, even in the case of missing test results. The performed tests show the usefulness of our test system.

[Determination of serum- and phagocyte resistance of E. coli using bioluminescence]

Resistance to serum and phagocytosis belong to the most important virulence markers of the bacteria. These properties enable the microorganism to have some selective advantage by overcoming of host defence, thus increasing the invasiveness of the bacteria. Determination of these properties make it possible to evaluate better the virulence of the facultative-pathogenic microorganisms and can therefore be used for microbiological diagnosis. The method used until now to test these characteristics are very time consuming. For these reason we have employed bioluminescence to determine the number of viable cells. This method is very suitable for this purpose.