Lyme borreliosis incidence in two French departments: correlation with infection of Ixodes ricinus ticks by Borrelia burgdorferi sensu lato.

We conducted a prospective study to estimate the Lyme borreliosis incidence in two rural French departments, Meuse and Puy-de-Dôme. Concurrently, we investigated the prevalence of ticks infected with Borrelia burgdorferi sensu lato (sl) and Anaplasma phagocytophilum. The incidence of Lyme borreliosis decreased from 156 to 109/100,000 inhabitants in Meuse and from 117 to 76/100,000 inhabitants in Puy-de-Dôme in 2004 and 2005, respectively, corresponding to a decrease in the density of Ixodes ricinus nymphs infected with B. burgdorferi sl. During the same period, the density of adult ticks increased. Interestingly, B. valaisiana, a nonpathogenic species, infected adult ticks more often than nymphs. These results confirmed the correlation between the Lyme borreliosis incidence and the density of infected nymphs, a stage preferentially infected with B. afzelii. In contrast, we found a low rate of infection by A. phagocytophilum, ranging from 0% to 0.4% in Puy-de-Dôme and from 0.8% to 1.4% in Meuse, suggesting a low risk for humans.

[Laboratory based human leptospirosis surveillance in New Caledonia (2001-2005)]. / Bilan de cinq années de surveillance biologique de la leptospirose humaine en Nouvelle-Calédonie (2001-2005).

The Pasteur Institute in New Caledonia performs for this territory the biological diagnosis of human leptospirosis; therefore its activity locally gives a rather exhaustive description of this pathology. The results presented here cover the 2001-2005 period and describe the principal epidemiological and biological features of human leptospirosis in New Caledonia. The investigated patients were recruited by the main medical structures: territorial and provincial hospitals, public dispensaries, clinics and general practitioners. The laboratory used the microagglutination test for serological investigations and PCR methods for the early detection of Leptospira genome in clinical samples. 239 cases of leptospirosis were biologically confirmed among 6690 tested patients, giving an average incidence of 21 cases per 100000/year, and a lethality rate of 5.4%. The sex-ratio was 1.8 male/female, patients were predominantly belonging to the 20-50 year age group and were inhabitants from the Northern Province. The circulating serogroups were mainly Icterohaemorrhagiae (69%), Australis (8%) and Pyrogenes (6%). The annual incidence peak occurred in April at the end of the warm season, and the importance of annual outbreaks could be linked with El Ninõ, the main regional climatic phenomenon.

The implications of a low rate of horizontal transfer in Borrelia.

The nature and rate of recombination can be studied by comparing the sequences of multiple genes across a set of strains. When this approach is applied to Borrelia burgdorferi, four results emerge: (1) chromosomal genes are clonal; (2) there is little or no plasmid exchange; (3) the major mode of horizontal transfer of genetic material inserts a small fragment of DNA, typically <1 kb, during recombination; and (4) the level of horizontal transfer in Borrelia is so low that there is evidence for horizontal transfer only in genes where there is positive selection for diversity, that is, positive selection for the recombinant. Thus, Borrelia can serve as a model of a low recombination taxon. The implications of these results lead us to postulate that an unknown agent that is part of the Borrelia genome mediates the horizontal transfer of small fragments of DNA; the rare transfer of small fragments of DNA excludes both DNA parasites and virulence factors from the genome.

Diversity of ribosomal DNA fingerprints of Leptospira serovars provides a database for subtyping and species assignation.

Ribosomal DNA fingerprints from 103 pathogenic Leptospira strains were examined using EcoRI restriction and fragment length polymorphisms of rRNA genes. Sixty-nine new leptospiral ribotypes were described, in addition to 49 previously observed. Except for 5 strains, a good correlation between DNA homology data and ribotyping was observed. The genospecies of 31 reference strains could be presumed, since they shared 13 ribotypes with strain(s) previously studied by DNA homology. Furthermore, the definition of common rRNA hybridization fragments in each recognized DNA hybridization group provides information about the status of Leptospira reference strains yet to be classified. With 118 ribotypes now defined among the validated serovar reference strains, rRNA fingerprints constitute a database for subtyping Leptospira species.

First isolation of bacteriophages for a spirochaete: potential genetic tools for Leptospira.

Three bacteriophages of the saprophytic aquicole bacterium Leptospira biflexa were isolated from sewage waters from the outskirts of Paris, France. These phages do not infect representative strains of the pathogenic species Leptospira interrogans, and their host range is restricted to serovar patoc of the saprophytic species. The phages were found to be lytic and no lysogenic state could be demonstrated. Electron micrographs showed that the phages were morphologically identical and had polyhedral heads and contractile tails. Their genomes were sensitive to restriction enzymes and consisted of double-stranded DNA. Pulsed-field agarose gel electrophoresis indicated that their genomes were linear: 60 kb for LE1 and 50 kb for LE3 and LE4.

Linear chromosome of Borrelia burgdorferi.

The DNA organization of several European and American isolates of Borrelia burgdorferi, the aetiological agent of Lyme disease, was analysed in pulse-field agarose gel electrophoresis. The results of in situ cell lysis in agarose plugs demonstrated a unique arrangement for the DNA of this spirochete. The chromosome of Borrelia behaved as a eukaryotic linear chromosome with a size of around 1,000 kb. The genome also comprised several circular and linear plasmids which varied in size from 15 to 60 kb.

Distinct levels of genetic diversity of Borrelia burgdorferi are associated with different aspects of pathogenicity.

Different species of pathogenic Borrelia show different symptoms and tick vector specificity. Even within regions where only one species is found, Lyme disease progresses very differently from one patient to another. Since Borrelia shows very little recombination either within or between species, alleles of a gene can be used to mark clones. The ospC gene is highly variable within each species and can be used to define groups of related clones. It has been previously shown that only four out of seventeen ospC groups of Borrelia burgdorferi sensu stricto cause invasive forms of the disease. Other groups cause erythema migrans, a skin rash at the site of the tick bite, but not invasive disease, while still other groups seem to be nonpathogenic to humans. In this study we extend the analysis of the ospC gene to the other pathogenic species, Borrelia garinii and Borrelia afzelii. Only two groups in B. afzelii and four groups in B. garinii cause invasive disease. Thus, only ten out of the 58 defined ospC groups cause invasive and presumably chronic Lyme disease.

Interest of partial 16S rDNA gene sequences to resolve heterogeneities between Leptospira collections: application to L. meyeri.

This paper describes the advantage of using the first 330 bp (positions 46 to 375, Escherichia coli numbering) of the 16S rDNA gene for comparison of Leptospira isolates. Phylogenetic analysis conducted from the whole 16S rDNA sequences available in databanks as well as that conducted from the partial sequences yielded quite similar results, in accordance with data inferred from previous DNA-DNA relatedness studies. This tool was used for the comparison of Leptospira strains from different reference collections. Consistent results were obtained from the analysis of the polymorphism generated by pulsed-field gel electrophoresis. The study focused on different serovars of L. meyeri species, the classification of which has been controversial. The results revealed large collection heterogeneities, and suggest that the classification of the L. meyeri species should be revised.

Polymerase chain reaction with the 30-kb circular plasmid of Borrelia burgdorferi B31 as a target for detection of the Lyme borreliosis agents in cerebrospinal fluid.

The polymerase chain reaction (PCR) was developed for use in the detection of Borrelia burgdorferi sensu lato, the Lyme disease agent. A 333-bp fragment of the 30-kbp circular plasmid from Borrelia burgdorferi B31 was amplified and PCR products were analysed by DNA-DNA hybridization. Sensitivity was enhanced by addition of a carrier to the samples before treatment and enabled detection of as few as 1 to 10 bacteria. Specific products were obtained only with the Lyme disease agents, but not with other spirochetes or unrelated bacteria. B. burgdorferi sensu lato was detected in cerebrospinal fluid (CSF) from 11 out of 45 patients with confirmed Lyme neuroborreliosis. In a prospective study, 20 out of 315 CSF samples from potential patients were PCR-positive. Forty uninfected patients were PCR-negative.

Antigenic variation of Borrelia turicatae Vsp surface lipoproteins occurs in vitro and generates novel serotypes.

As a means of avoiding the host immune response, the tick-borne relapsing fever spirochete Borrelia turicatae undergoes antigenic variation in its abundant surface lipoproteins. In this study, B. turicatae strain Oz1, serotype B, was subcultured in vitro and cloned by limited dilutions after 50 passages. Four different serotypes (serotypes A, B, E, and F) differing by their expressed Vsp lipoproteins were isolated. Using pulsed-field gel electrophoresis, we showed that the variability in surface-exposed proteins is correlated with rearrangement between different linear plasmids, defining serotype-specific plasmid profiles. Moreover, we determined the nucleotide sequence of genes encoding the VspE and VspF lipoproteins, corresponding to the two novel serotypes E and F, respectively. Our results showed that antigenic variation in B. turicatae occurs spontaneously in vitro, in the absence of immune selection.

rRNA gene restriction patterns of Leptospira: a molecular typing system.

A total of 67 serovar reference strains and 7 isolates belonging to the genus Leptospira were characterized by ribosomal ribonucleic acid (rRNA) gene restriction patterns. Fifty patterns were observed. Strains belonging to different genomic species always gave different patterns. However, genomic species were subdivided into several patterns. Forty-three serovars gave a specific pattern. Some serovars could not be separated by rRNA gene restriction patterns: strains of serovars icterohaemorrhagiae, copenhageni, lai, pyrogenes and jalna gave pattern 1; serovars birkini, mankarso and wolffi gave pattern 4; serovars canicola, gem, hebdomadis, pomona and hardjo (strain hardjoprajitno) gave pattern 12; serovars valbuzzi and zanoni gave pattern 14; serovars jonsis, malaya and sumneri gave pattern 16; serovars arborea, ballum, castellonis and kenya gave pattern 35; and serovars borincana and shermani gave pattern 43. These data provide the bases for a molecular typing system for the genus Leptospira.

A new genomic species in Borrelia burgdorferi sensu lato isolated from Japanese ticks.

Five Borrelia strains (Ika2, HO14, Cow611C, 0612 and F63B) isolated from Ixodes ovatus ticks in Japan were analysed by DNA-DNA hybridization experiments, ribotyping, pulsed-field gel electrophoresis and protein electrophoresis. DNA relatedness set these strains in a new genomic species within the Borrelia burgdorferi complex; this species appears to be restricted to Japan and could be non-pathogenic for humans. The ribotype and pulsotype of strain Ika2 were atypical of the new genomic species.

Borrelia burgdorferi sensu lato in Russia and neighbouring countries: high incidence of mixed isolates.

A total of 365 isolates of Borrelia burgdorferi sensu lato from 12 major administrative territories of Russia (from St. Petersburg in the west to South Sakhalin in the east) and from the Czech Republic, Estonia, Lithuania, Byelorussia, Moldavia, Ukraine and Kirghizia were identified by analysis of restriction polymorphism of ribosomal rrf-rrl spacer amplicons. The isolates were obtained mainly from ixodes persulcatus and I. ricinus ticks. Other sources included small mammals, human patients and I. trianguliceps ticks. The results showed that B. garinii (two variants) together with B. afzelii circulated throughout the territories studied. The distribution of the variant NT29 of the species B. garinii, the most frequently isolated, was associated with that of I. persulcatus ticks. B. burgdorferi sensu stricto, and the species B. valaisiana and B. lusitaniae (formerly the genomospecies VS116 and PotiB2, respectively) were isolated only from I. ricinus ticks in the western part of the studied territories. None of these three species were found in 327 isolates from Russia where I. persulcatus is the most frequently distributed vector. This work also provides evidence for a high incidence of mixed Borrelia infections within vectors and hosts (9.3% of isolates were mixtures of Borrelia species). A detailed analysis of Borrelia species distribution over the territories studied is presented.

Two genomic species in Borrelia burgdorferi.

A total of 13 Borrelia burgdorferi strains (responsible for Lyme borreliosis) and representatives of 3 other Borrelia species (B. hermsii, B. parkeri, B. turicatae) associated with relapsing fever were studied by DNA/DNA hybridization and rRNA gene-restriction patterns. Two genomic DNA hybridization groups were observed which could be differentiated by rRNA gene-restriction patterns. Moreover, the number and size of restriction fragments suggest the existence of a single set of 16 and 23 S rRNA genes in Borrelia.

Occurrence of severe leptospirosis in a breeding colony of squirrel monkeys.

Although experimental leptospirosis has been studied in various species of monkeys, the occurrence of acute leptospirosis in a population of nonhuman primates is uncommon. We report on a number of severe cases of icterohemorrhagic leptospirosis that appeared in the squirrel monkey (Saimiri sciureus) colony of 109 animals at the Institute Pasteur in French Guiana. Initially, 11 animals had acute illness, with jaundice and a hemorrhagic syndrome, leading to 10 deaths. Two Leptospira interrogans strains were isolated from blood cultures of sick monkeys, and one was isolated from the urine of a rat trapped in the breeding park. All three belonged to serovar copenhageni, and tests using monoclonal antibodies showed that these three strains were extremely similar. In the following weeks, five pregnant female monkeys had miscarriages; two of them had antibodies against the Icterohaemorrhagiae serogroup. An epidemiologic study conducted on the 93 remaining animals demonstrated a seropositivity rate of 26% (microagglutination test [MAT] titer greater than or equal to 100) primarily for the Icterohaemorrhagiae serogroup, but also for the Ballum, Grippotyphosa, Sejroe, and Panama serogroups. In addition, 12% showed lower MAT titers (50) for the same serogroups. Lastly, recently trapped feral squirrel monkeys were shown to have agglutinins against the Grippotyphosa and Sejroe serogroups. A vaccine, which was prepared from one of the strains isolated, was used in addition to antibiotic prophylaxis to control the enzootic disease. This confirms that the squirrel monkey is highly susceptible to icterohemorrhagic leptospirosis and is probably receptive to other serogroups, and that this animal may be useful in studying experimental leptospirosis and for testing new human vaccines.

Oligonucleotides specific for pathogenic and saprophytic leptospira occurring in water.

Sets of primers specific for both pathogenic (SPL) and saprophytic (SSL) Leptospira were designed from ribosomal 16S genes (rrs) available in databases. They were used as two sets of primer pairs for the PCR amplification of known pathogenic and saprophytic strains. It was possible to identify pathogenic strains by the use of SPL primers and saprophytic ones by SSL primers. Serovars from L. meyeri, of controversial pathogenicity status, confirmed the heterogeneity of the species representatives in this respect. Serovars ranarum, sofia and perameles were amplified by SPL and not SSL. Conversely, serovar semaranga was amplified by SSL and not SPL. In order to use SPL primers for the detection of pathogenic leptospires from a natural water environment, we set up an additional semi-nested PCR by employing a second internal primer which succeeded in detecting as few as 5 pathogenic leptospires per ml of water.

Identification of a 36-kDa fibronectin-binding protein expressed by a virulent variant of Leptospira interrogans serovar icterohaemorrhagiae.

We investigated the ability of a virulent strain of Leptospira interrogans serovar icterohaemorrhagiae, its isogenic avirulent variant and a saprophytic strain to bind fibronectin using alkaline phosphatase-labelled fibronectin. A single 36-kDa fibronectin-binding protein was expressed only by the virulent strain and was located in the outer sheath according to proteinase K treatment results. The interaction of this protein with fibronectin was specific and the region of fibronectin bound to this potential adhesin overlapped the gelatin-binding domain. The inability of a RGDS synthetic peptide to inhibit the binding of fibronectin indicated that the cell-binding domain was not involved in this interaction. Considering the wide distribution of fibronectin within a host and the diversity of mammals involved in the epidemiology of leptospirosis, its implication in the cell attachment process of virulent leptospires is coherent with the multiplicity of target cells.

Species of Borrelia distinguished by restriction site polymorphisms in 16S rRNA genes.

Three phyletic groups of Borrelia associated with Lyme disease, B. burgdorferi, B. garinii and group VS461 can be distinguished from each other and other species of Borrelia by BfaI restriction site polymorphisms in PCR amplified 16S rRNA genes. One strain isolated from an Ixodes pacificus tick in California that was previously unclassifiable was distinguishable from B. burgdorferi by an Mn/I restriction site polymorphism.

Individualisation of two new genomic groups among American Borrelia burgdorferi sensu lato strains.

We developed a quick typing method for Borrelia burgdorferi sensu lato strains using a fla gene-based PCR assay, followed by dot blot hybridization with non-radioactive species-specific probes. Thirty-six out of 46 strains belonged to one of the four described species (B. burgdorferi sensu stricto n = 11, B. garinii n = 11, B. afzelii n = 9 and B. japonica n = 5) and hybridized with its own species-specific probe. Among the 10 remaining American strains, two new additional genomic groups were identified. This finding was confirmed by direct sequencing of the fla gene-derived amplicons and whole DNA hybridization.

In vivo apoptosis of hepatocytes in guinea pigs infected with Leptospira interrogans serovar icterohaemorrhagiae.

To investigate the contribution of the previously demonstrated in vitro apoptosis to the pathogenesis of leptospirosis, guinea pigs were infected with Leptospira interrogans serovar icterohaemorrhagiae strain Verdun and sequentially killed to collect target organs involved in the natural history of the disease (liver, kidneys, lungs, spleen and heart). The combination of histopathological procedures and a specific TUNEL assay showed a significant Leptospira-induced programmed cell death of hepatocytes with a peak at 48 h post inoculation. Hepatocyte nuclei showed morphological changes including fragmented and condensed nuclei. This phenomenon occurred early in the course of the disease at a time where infecting leptospires were present at a low density between the liver parenchyma cells.