Parasitic genotypes appear to differ in leishmaniasis patients compared with asymptomatic related carriers

For numerous infectious diseases affecting humans, clinical manifestations range from asymptomatic forms to severe pathologies. The originality of this study was its focus on asymptomatic carriers of Leishmania infantum in southern France. The fundamental interest in these asymptomatic carriers is that they can be a reservoir of potentially pathogenic microorganisms. It remains to be established whether the parasitic genomes from asymptomatic carriers differ from those of patients. Multilocus microsatellite typing was used to investigate the genetic variation among 36 French strains of L. infantum. Nine Leishmania strains isolated from blood donors (asymptomatic carriers) were compared with 27 strains of L. infantum belonging to zymodemes, MON-1, -33 and -183. These strains were isolated from HIV positive or negative patients with visceral leishmaniasis, cutaneous leishmaniasis, from canine leishmaniasis or from phlebotomine sandflies. Multilocus microsatellite typing data generated using 33 loci were analyzed by a Bayesian model-based clustering algorithm and construction of a phylogenetic tree based on genetic distances. Both analyses structured the MON-1 sample into two main clusters. Furthermore, genetic analysis demonstrated that these nine asymptomatic carrier strains are divided into two clusters grouped with the MON-1 strains. One cluster with seven strains is related to, but different from, human symptomatic strains from the Alpes-Maritimes region whereas the other cluster has the two remaining strains together with canine leishmaniasis strains as well as one strain from a visceral leishmaniasis patient. Genetic diversity among asymptomatic carrier was very weak since the nine Leishmania strains belong to only two genotypes. Genetic differentiations were evidenced between asymptomatic carrier strains and non-asymptomatic carrier strains and especially between asymptomatic carrier and HIV+ populations, although these findings require confirmation with a larger sample size. We believe that our data explore for the first time, the genetic diversity among L. infantum from asymptomatic human carriers and reveal a weak polymorphism compared with Leishmania parasites isolated from human patients.

Genetic diversity, population structure and drug resistance of Mycobacterium tuberculosis in Peru

This paper presents the first evaluation of the molecular epidemiology of Mycobacterium tuberculosis in Peru. We characterised 323 isolates using spoligotyping and mycobacterial interspersed repetitive units variable number tandem repeats (MIRU-VNTR) typing. We aimed to determine the levels of genetic diversity and genetic differentiation among and within Peruvian isolates and the epidemiological factors which may be driving patterns of population structure and evolution of M. tuberculosis in Peru. Our results compared to the fourth international spoligotyping database (SpolDB4) and MIRU-VNTRplus, show that the main M. tuberculosis families present are Latin American-Mediterranean, Haarlem, T, and Beijing. Bayesian clustering recovered 15 groups in the Peruvian M. tuberculosis isolates, among which two were composed mainly of orphans, implying the presence of native "Peruvian" strains not previously reported. Variable levels of association with drug resistance were observed, with Beijing genotypes not showing any association with multidrug resistance, while in other groups MIRU-VNTR loci 2, 23, 31, and 40 were found to be associated with the multidrug-resistant tuberculosis (MDR-TB) phenotype, suggesting that a linkage disequibrium between these MIRU and drug resistance loci may be present. Genetic differentiation was present among drug resistant and sensitive strains. Ethambutol appeared to be the main driver of differentiation, suggesting that strong selection pressure could have been exerted by drug treatment in Peru over recent years.

Clinical pleiomorphism in human leishmaniases, with special mention of asymptomatic infection

This review gives an update of current knowledge on the clinical pleiomorphism of Leishmania, with a special emphasis on the case of asymptomatic carriage. The first part describes the numerous unusual expressions of the disease that occur besides the classic (visceral, cutaneous, and mucocutaneous) forms of leishmaniases. The second part deals with progress in the understanding of disease outcome in humans, and the possible future approaches to improve our knowledge in the field. The third part highlights the role of the too often neglected asymptomatic carrier compartment. This group could be key to understanding infraspecific differences in virulence and pathogenicity of the parasite, as well as identifying the genetic determinants involved in the expression of the disease.

Pulmonary tuberculosis due to Mycobacterium microti: a study of six recent cases in France

Human tuberculosis caused by Mycobacterium microti is rare, but its prevalence and clinical significance may have been underestimated. To the best of our knowledge, 21 cases have been reported in the literature in the last decade. We report six recent pulmonary cases caused by M. microti over a period of 5 years detected in French clinical mycobacteriology laboratories of the hospital network. Our data confirm the potential of M. microti to cause clinical illness in immunocompetent patients. M. microti grew slowly from specimens, delaying the final microbiological diagnosis. Therefore, patients with tuberculosis caused by M. microti could benefit from the use of rapid diagnostic molecular techniques directly on clinical samples. From a review of the literature and this study, a classical antituberculous therapy seems effective in treating patients with M. microti disease.

Highly structured genetic diversity of the Mycobacterium tuberculosis population in Djibouti

Djibouti is an East African country with a high tuberculosis incidence. This study was conducted over a 2-month period in Djibouti, during which 62 consecutive patients with pulmonary tuberculosis (TB) were included. Genetic characterization of Mycobacterium tuberculosis, using mycobacterial interspersed repetitive-unit variable-number tandem-repeat typing and spoligotyping, was performed. The genetic and phylogenetic analysis revealed only three major families (Central Asian, East African Indian and T). The high diversity and linkage disequilibrium within each family suggest a long period of clonal evolution. A Bayesian approach shows that the phylogenetic structure observed in our sample of 62 isolates is very likely to be representative of the phylogenetic structure of the M. tuberculosis population in the total number of TB cases.

A microculture technique for isolating live Leishmania parasites from peripheral blood of visceral leishmaniasis patients

Current procedures for diagnosing Leishmania parasites from patients involve invasive and dangerous tissue aspiration. We have developed a non-invasive and highly sensitive microculture method that can isolate parasites from the buffy coat of the patient's peripheral blood. The parasites were cultured in 96-well culture plates. Nineteen parasitologically proven visceral leishmaniasis (VL) patients were included in the study. Using this technique, we were able to isolate parasites from 16 (84%) samples. However, all 19 (100%) samples were positive on culture of splenic aspirates. We conclude that this technique is useful for the isolation and cryoconservation of parasites from patients' blood. This simple method could be tried as a first-instance alternative before other more sensitive procedures such as splenic aspirate; however, negative results should be confirmed by tests with higher sensitivity.

First molecular epidemiology study of Mycobacterium tuberculosis in Burkina Faso

We conducted a molecular epidemiology study on 120 Mycobacterium tuberculosis isolates from patients presenting pulmonary tuberculosis (TB) in Burkina Faso. Classical antibiogram studies and genetic characterization, using mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing and spoligotyping, were applied after culture. Molecular analysis of specific signatures showed that all TB cases reported in this study were caused by M. tuberculosis and identified no Mycobacterium bovis or Mycobacterium africanum isolates. This result is unexpected, as M. africanum strains were reportedly the etiologic agent in 20% of TB cases 2 decades ago. The comparison of spoligotypes from Burkina Faso with an international spoligotype database (SpolDB4) showed that the majority of isolates belong to major clades of M. tuberculosis (Haarlem, 9%; Latin American-Mediterranean, 30%; and T, 20%). The predominant group of isolates (30%) corresponds to spoligotype 61, described in Cameroon as the "Cameroon family." In Burkina Faso, as in Cameroon, this family could be associated with recent transmission of TB, suggesting a recent expansion in West Africa. Our data suggest a low level of primary drug resistance that may be a positive result of the Directly Observed Therapy Shortcourse program. Besides, based on spoligotyping plus MIRU-VNTR, data showed a high number of clusters in our sample, suggesting a high level of recent TB transmission in Burkina Faso. Nevertheless, an important genetic polymorphism was observed in this country, reflecting an endemicity situation where the control of TB would have less impact in the main towns.

Specific cpb copies within the Leishmania donovani complex: evolutionary interpretations and potential clinical implications in humans

Leishmania infantum and Leishmania donovani both pertain to the L. (L.) donovani complex and are responsible for visceral leishmaniasis. To explore the L. donovani complex, we focused our study on cysteine protease B (cpb) and especially on 2 cpb copies: cpbE and cpbF. We selected cpb genes because of their phylogenetic interest and host-parasite interaction involvement. Sequencing these 2 copies revealed (i) that cpbE is specific to L. infantum and cpbF is specific to L. donovani and (ii) that these 2 copies are different in length and sequence. Phylogenetic analysis and protein predictions were carried out in order to compare these copies (i) with other trypanosomatid cpb, especially L. mexicana, and (ii) within the L. donovani complex. Our results revealed patterns specific to the L. donovani complex such as the COOH-terminal extension, potential epitopes and N-glycosylation sites. Moreover, phylogenetic analysis revealed different levels of polymorphism between L. infantum and L. donovani and confirmed the ancestral status of the latter. L. infantum has a shorter sequence and a deleted sequence responsible for modifications in protein conformation and catalytic triad. Considering the clinical aspect, L. infantum dermotropic strains appeared more polymorphic than L. infantum viscerotropic strains.

American tegumentary leishmaniasis: antigen-gene polymorphism, taxonomy and clinical pleomorphism

Multi-locus enzyme electrophoresis is the current gold standard for the genetic characterisation of Leishmania. However, this method is time-consuming and, more importantly, cannot be directly applied to parasites present in host tissue. PCR-based methods represent an ideal alternative but, to date, a multi-locus analysis has not been applied to the same sample. This has now been achieved with a sample of 55 neotropical isolates (Leishmania (Viannia) braziliensis, L. (V.) peruviana, L. (V.) guyanensis, L. (V.) lainsoni and L. (L.) amazonensis), using five different genes as targets, four of which encoded major Leishmania antigens (gp63, Hsp70, H2B and Cpb). Our multi-locus approach strongly supports the current taxonomy and demonstrates a highly robust method of distinguishing different strains. Within L. (V.) braziliensis, we did not encounter so far specific genetic differences between parasites isolated from cutaneous and mucosal lesions. Interestingly, results provided by each of the different antigen-genes in the species considered, were different, suggesting different selective pressures. Our work emphasises the need for a multi-disciplinary approach to study the clinical pleomorphism of leishmaniasis.

Genetic diversity, clonality and sexuality in Toxoplasma gondii

The majority of Toxoplasma gondii strains from a variety of human and animal sources have been grouped into three highly clonal but closely related lineages. The low occurrence of nucleotide differences among the three predominant lineages and their unusual dimorphic allelic composition suggest that they have arisen from a recent common ancestry. Less than 1% of the previously studied strains contain unique genotypes and high divergence of DNA sequence, and therefore are considered 'exotic' or 'atypical' strains. The seemingly low genetic diversity in T. gondii may have been underestimated because most parasite strains in previous studies were collected from human patients and domestic animals in North America and Europe. To investigate the genetic diversity of T. gondii, we analysed parasite strains isolated from remote geographical regions by multilocus microsatellite sequencing and phylogenetic analysis. The genetic diversity indices, the molecular analysis of microsatellite genotypes and the constructed phylogram considered together suggest that the global T. gondii population is highly diversified and not characteristic of a clonal organism. The most parsimonious hypothesis is that T. gondii presents a complex population structure with a mix of clonal and sexual propagation as a function of the environmental conditions. The comparison between domestic strains data on one hand and wild strains data on the other hand is in favour of more frequent sexual recombinations in wild environment even though Toxoplasma subpopulation in human and domestic animals is largely clonal.

Co-infection by Leishmania amazonensis and L. infantum/L. chagasi in a case of diffuse cutaneous leishmaniasis in Bolivia

We present the first report of a co-infection by Leishmania amazonensis and L. infantum/L. chagasi isolated in 1993 from a patient with diffuse cutaneous leishmaniasis (DCL), living in the sub-Andean region of Bolivia. This is the third reported case of DCL in Bolivia, but the first one with isoenzymatic identification of the aetiological agents involved and the first one giving evidence for a mixed infection by 2 Leishmania parasites in the same lesion.

Genetic heterogeneity and phylogenetic status of Leishmania (Leishmania) infantum zymodeme MON-1: epidemiological implications

Leishinania (Leishmania) infantum zymodeme MON-1 is responsible for the majority of visceral leishmaniasis cases around the Mediterranean basin, albeit that it causes also cutaneous forms. The MON classification is based on starch gel multilocus enzyme electrophoresis (MLEE) typing. The aim of this work was to explore further the genetic diversity and phytogenetic status of this zymodeme by alternative typing techniques. Fourteen L. (L.) infantum/L. (L.) chagasi stocks identified as MON-1 by MLEE in reference laboratories, 3 L. infantum stocks attributed to other zymodemes (MON-24, MON-29, MON-33) and reference standard stocks belonging to other species (L. (L.) major, L. (L.) tropica and L. (L.) donovani) were characterized by 2 different markers: MLEE on cellulose acetate plates and Random Amplified Polymorphic DNA (RAPD). We have obtained 10 different genotypes with RAPD and 6 different genotypes with MLEE on cellulose acetate plates for the 14 L. infantum/L. chagasi MON-1 stocks studied. MLEE and RAPD data gave quite congruent phylogenetic results: L. infantum zymodeme MON-1 was shown to be polyphyletic and genetically heterogeneous. This work confirms the necessity of using different markers to build up a robust phylogeny. Finally the epidemiological and clinical implications of these results are discussed.

Methicillin-resistant Staphylococcus aureus: phylogenetic relatedness between European epidemic clones and Swiss sporadic strains

We have compared the phylogenetic diversity of methicillin-resistant Staphylococcus aureus (MRSA) strains from Switzerland and their phylogenetic relationships with European epidemic clones, using multiprimer random amplification polymorphic DNA (RAPD). Strains included 24 European epidemic clones (59 strains), 66 sporadic strains isolated in Switzerland in 1996-1997, and 15 reference strains of five other Staphylococcus species. Similarity and clustering analysis with the Jaccard's coefficient showed that the maximum genetic distance between MRSA strains was 0.43, whereas the minimum genetic distance between the six Staphylococcus species was 0.97, indicating that the method permits phylogenetic hierarchization. The 24 MRSA clones reported to be epidemic in European countries during the 1990s were distributed into seven different genetic clusters with a maximum distance of 0.29 among them. This clustering pattern was confirmed by the analysis of a subset of MRSA strains by multilocus enzyme electrophoresis at 12 loci. Most of the sporadic Swiss strains were distributed into these seven different genetic clusters, together with the epidemic MRSA clones. This suggests that there is no phylogenetic cluster specific to epidemic clones of MRSA.

Visceral leishmaniasis in a German child who had never entered a known endemic area: case report and review of the literature

We describe a case of visceral leishmaniasis in a 15-month-old German child. Diagnosis was significantly delayed because the patient had no history of travel to known endemic areas. Congenital or blood transfusion-associated leishmaniasis was ruled out. Possible modes of transmission (including a potential new autochthonous focus of the disease in central Europe) are discussed.

Is Leishmania (Viannia) peruviana a distinct species? A MLEE/RAPD evolutionary genetics answer

A set of 38 Leishmania stocks from the Andean valleys of Peru was characterized by both Multilocus Enzyme Electrophoresis (MLEE) and Random Amplified Polymorphic DNA (RAPD). Data were analyzed in terms of taxonomy and evolutionary genetics. Synapomorphic MLEE and RAPD characters, clear-cut clustering, and strong agreement between the phylogenies inferred from either MLEE or RAPD supported the view that Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis correspond to two closely related, but distinct monophyletic lines (clades) and can therefore be considered as "discrete typing units" (DTUs). The question whether the L. (V.) peruxviana DTU deserves species status is dependent upon the desirability of it, in terms of epidemiological and medical relevance. A previous Orthogonal Field Alternating Gel Electrophoresis (OFAGE) analysis of the same L. (V.) peruviana isolates was published by Dujardin et al. (1995b). The data from the different markers (i.e. MLEE, RAPD and OFAGE) were compared by population genetics analysis. RAPD and OFAGE provided divergent results, since RAPD showed a strong linkage disequilibrium whereas OFAGE revealed no apparent departure from panmictic expectation. MLEE showed no linkage disequilibrium. Nevertheless, contrary to OFAGE, this is most probably explainable by the limited variability revealed by this marker in L. (V.) peruviana (statistical type II error). RAPD data were consistent with the hypothesis that the present L. (V.) peruviana sample displays a basically clonal population structure with limited or no genetic exchange. Disagreement between RAPD and OFAGE can be explained either by accumulation of chromosomal rearrangements due to amplification/deletion of repeated sequences, or by pseudo-recombinational events.

Unusual cutaneous lesions in two patients with visceral leishmaniasis and HIV infection

Two HIV infected patients with visceral leishmaniasis and unusual cutaneous lesions are described. The first patient developed linear brown macules containing Leishmania parasites on the fingers and palms of the hands. This patient never received highly active antiretroviral treatment and the visceral leishmaniasis could not be cured even with liposomal amphotericin. In the second patient, Leishmania parasites were present in a skin biopsy of a fibrous histiocytoma. After completing visceral leishmaniasis treatment, a discrete elevation of one of his tattoos was seen. A biopsy specimen of this tattoo revealed Leishmania amastigotes. In this patient the visceral leishmaniasis was finally cured with meglumine antimoniate, followed by pentacarinat isothianate as maintenance therapy in conjunction with highly active antiretroviral treatment.

Genetic analysis of leishmania parasites in Ecuador: are Leishmania (Viannia) panamensis and Leishmania (V.) Guyanensis distinct taxa?

In the course of an epidemiologic survey in Ecuador, the following collection of Leishmania stocks was isolated: 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either Leishmania (V.) panamensis or L. (V.) guyanensis, 2 stocks were identified as L. (V.) braziliensis, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between L. (V.) braziliensis and L. (V.) guyanensis. These data show that genetic diversity of Leishmania in Ecuador is high and that L. (V.) panamensis/guyanensis is the dominant group in this country. The genetic analysis questioned the distinctness between the two species L.(V.) panamensis and L. (V.) guyanensis, since MLEE and RAPD data did not indicate that L. (V.) panamensis and L. (V.) guyanensis correspond to distinct monophyletic lines. Population genetic analysis performed on the L. (V.) panamensis/guyanensis group favors the hypothesis of a basically clonal population structure.

A phylogenetic analysis by multilocus enzyme electrophoresis and multiprimer random amplified polymorphic DNA fingerprinting of the Leishmania genome project Friedlin reference strain

We have assessed the phylogenetic status of the Leishmania genome project Friedlin reference strain by MLEE and multiprimer RAPD including a set of 9 stocks representative of the main Leishmania species and of the whole genetic diversity of the Leishmania genus. To our knowledge, the detailed genetic characterization of the Friedlin strain has never been published before. As previously recorded (Tibayrenc et al. 1993), MLEE and RAPD data gave congruent phylogenetic results. The Friedlin reference strain was definitely attributed to Leishmania (Leishmania) major Yakimoff et Schokhor, 1914. Five specific RAPD patterns made it possible to distinguish between the Friedlin strain and the 2 other L. (L.) major stocks included in the study. Various specific MLEE and RAPD characters permitted to distinguish between the Leishmania species included in the study. All these characters are usable to detect accidental laboratory mix-ups involving the Friedlin reference strain. In confirmation with previous studies involving a more limited set of genetic markers, the general genetic diversity of the Leishmania genus proved to be considerable. It must be made clear that only one strain cannot be considered as representative of the whole genetic variability of the genus Leishmania. In the future, it is therefore advisable to complement the results obtained in the framework of the Leishmania genome project with data from other strains that should be selected on a criterion of important genetic differences with the Friedlin strain.

Comparison of chromosome and isoenzyme polymorphism in geographical populations of Leishmania (Viannia) peruviana

Five chromosomes and 17 isoenzyme loci were analysed in 4 allopatric populations of Leishmania (Viannia) peruviana, and molecular distances calculated with 2 estimators, Chromosomal Size Difference Index and Jaccard Distance. Chromosome and isoenzyme data were in overall concordance: 13/30 isolates clustered similarly on the dendrograms constructed from the different estimators, and a significant correlation (P < 0.001) was observed between the molecular distances calculated from the two sets of characters. This indicates an evolutionary association between chromosomal size polymorphism and isoenzymes. Chromosomes have a faster molecular clock than isoenzymes; twice as many genotypes were identified by chromosome analysis and significant size differences (for a total of up to 500 kb for 5 chromosomes together) were observed within a given zymodeme. Chromosomes most likely represent better indicators of genetic drift than isoenzymes, as suggested by the higher correlation between both estimators of chromosomal size-polymorphism and eco-geography. Some chromosomes might present an adaptive response to environmental variation.

The gp63 gene locus, a target for genetic characterization of Leishmania belonging to subgenus Viannia

In the present study the gp63 gene locus was used as a target for genetic characterization of Leishmania parasites by 2 methods: (i) RFLP analysis with several restriction enzymes (gp63-RFLP), and (ii) intra-genic PCR amplification coupled with restriction analysis (PCR-RFLP). Both methods were applied to a large number of natural isolates belonging to 4 species of the subgenus Viannia, namely L. (V.) braziliensis, L. (V.) peruviana, L. (V.) guyanensis and L. (V.) lainsoni; reference stocks of subgenus Leishmania were included as outgroups. Multilocus isoenzyme typing (MLEE) was used as a reference. On the one hand gp63-RFLP evidenced an extensive polymorphism and revealed specific markers for subgenus, species and geographical populations: congruence with MLEE was demonstrated statistically. The particular interest of gp63-RFLP was illustrated by infra-specific polymorphism, because of the possible relationship with phenotype diversity. On the other hand intra-genic amplification was less resolutive than gp63-RFLP, but also allowed discrimination of the 2 subgenera (PCR alone) and all the species tested in the subgenus Viannia (PCR-RFLP). PCR-RFLP presents an important operational advantage as it allows genetic characterization of minute amounts of parasites, using Leishmania specific primers. The polymorphism revealed by gp63-RFLP and PCR-RFLP illustrates the very high genomic and genetic plasticity of gp63 genes.

A phylogenetic analysis of the Trypanosoma cruzi genome project CL Brener reference strain by multilocus enzyme electrophoresis and multiprimer random amplified polymorphic DNA fingerprinting

We have assessed the phylogenetic status of the Trypanosoma cruzi Genome Project CL Brener reference strain by multilocus enzyme electrophoresis (MLEE) and multiprimer random amplified polymorphic DNA (RAPD) including a set of cloned stocks representative of the whole genetic diversity of T. cruzi. MLEE and RAPD data gave congruent phylogenetic results. The CL Brener reference strain fell into the second major phylogenetic subdivision of T. cruzi, and was genetically very close to the Tulahuen reference strain. No reliable RAPD character and only one MLEE character permitted us to distinguish between the CL Brener and Tulahuen reference strains. In contrast, many RAPD and MLEE characters were able to distinguish between the CL Brener reference strain and the other T. cruzi genotypes analyzed here, in particular the formerly described principal zymodemes I, II and III. It is suspected that both CL Brener and Tulahuen are hybrid genotypes, a fact that should be taken into account when interpreting sequence data. Moreover, our study confirms that the species T. cruzi is genetically very heterogeneous. We recommend future comparison of sequencing data from the CL Brener reference strain with those of at least one radically distinct T. cruzi genotype, belonging to the other major phylogenetic subdivision of this species.

Evidence for hybridization by multilocus enzyme electrophoresis and random amplified polymorphic DNA between Leishmania braziliensis and Leishmania panamensis/guyanensis in Ecuador

The taxonomic attribution of four Leishmania stocks isolated from humans in Ecuador has been explored by both multilocus enzyme electrophoresis and random amplified polymorphic DNA. For three loci, MLEE results showed patterns suggesting a heterozygous state for a diploid organism, while the corresponding homozygous states are characteristic of the Leishmania panamensis/guyanensis complex and Leishmania braziliensis, respectively. Other enzyme loci showed characters attributable to either the L. panamensis/ guyanensis complex or L. braziliensis. RAPD profiles exhibited for several primers a combination of the Leishmania panamensis/ guyanensis complex and L. braziliensis characters. These data hence suggest that the four stocks are the result of hybridization between L. panamensis/guyanensis and L. braziliensis. MLEE data show that the results cannot be attributed to either mixture of stocks, or an F1 in the framework of a simple Mendelian inheritance.

Population structure of Trypanosoma brucei S. L. in Cote d'Ivoire assayed by multilocus enzyme electrophoresis: epidemiological and taxonomical considerations

Fifty-two Trypanosoma brucei stocks isolated in Côte d'Ivoire from sympatric locations were analyzed by cellulose acetate electrophoresis of isoenzymes. Of 13 genetic loci surveyed, 5 appeared as variable, which made it possible to delimit 12 different zymodemes. The most abundant zymodeme involved stocks isolated from both humans and pigs, which is consistent with the hypothesis that pig is a reservoir of human African trypanosomiasis in Côte d'Ivoire, as already proposed by other authors. Population genetic analysis of the isozyme data indicated a strong linkage disequilibrium, which suggests that genetic recombination is severely restricted in this sample and favors the hypothesis that the trypanosome populations surveyed are basically clonal. Nevertheless, additional studies are required to better estimate the long-term stability of these clones and the possible interference of gene exchange at an evolutionary scale. The results corroborate the hypothesis that a majority of human T. brucei stocks from West Africa correspond to a fairly homogeneous cluster of genotypes (T. brucei gambiense 'Group I', Gibson, 1986).

From population to genome: ecogenetics of Leishmania (Viannia) braziliensis and L. (V.) peruviana

The size polymorphism of nine chromosomes, recognized by specific probes, was analysed in populations of Leishmania (Viannia) braziliensis and L. (V.) peruviana from various Peruvian biogeographical units. Interpretation of the polymorphism, by statistical and phenetic methods, led to the identification of five consensus (alpha- and beta-tubulin) and four variable chromosomes. The dynamics of the variable chromosomes were studied. The promoter role of the environment on their polymorphism was indicated by: (1) the discrimination of L. braziliensis (forest) and L. peruviana (Andes) by the size of the chromosome containing the gp63 genes; and (2) the fact that, within L. peruviana, the polymorphism of the variable chromosomes revealed a strong eco-geographical structuring of parasite populations, accompanied by increasing chromosomal dissimilarity along a cline from north to south. The adaptative significance of the polymorphism of the variable chromosomes was suggested by: (1) a correlation between chromosomal polymorphism and phenotype variability (lesion type in patients and virulence in vitro); and (2) the association between the decrease in size of the gp63-containing chromosome from L. braziliensis to L. peruviana, and a rearrangement of the gp63 genes, probably accompanied by a decrease in their copy number. As chromosomal variation was shown to be more dependant on eco-geographical differences than isoenzymatic variation, chromosome variation and enzyme variation probably differ in adaptative significance.

Putative Leishmania hybrids in the Eastern Andean valley of Huanuco, Peru

During an outbreak of tegumentary leishmaniasis that developed in the 1990s in the Eastern Andean valley of Huanuco, Peru, the coexistence of Andean (uta) and sylvatic leishmaniases was suspected for ecological and geographical reasons, and sympatric sampling was carried out. Seven human isolates of Leishmania were characterized by multilocus enzyme electrophoresis, random amplification of polymorphic DNA and molecular karyotyping. The three methods identified 3 isolates as L. braziliensis, and 4 isolates as putative hybrids with characters of L. braziliensis and L. peruviana. Data from Huanuco are compared to previous results from other areas endemic for uta. Biological and epidemiological implications are discussed.