Serovar diversity of pathogenic Leptospira circulating in the French West Indies

Abstract

Background: Leptospirosis is one of the most important neglected tropical bacterial diseases in Latin America and the Caribbean. However, very little is known about the circulating etiological agents of leptospirosis in this region. In this study, we describe the serological and molecular features of leptospires isolated from 104 leptospirosis patients in Guadeloupe (n = 85) and Martinique (n = 19) and six rats captured in Guadeloupe, between 2004 and 2012.

Methods and findings: Strains were studied by serogrouping, PFGE, MLVA, and sequencing 16SrRNA and secY. DNA extracts from blood samples collected from 36 patients in Martinique were also used for molecular typing of leptospires via PCR. Phylogenetic analyses revealed thirteen different genotypes clustered into five main clades that corresponded to the species: L. interrogans, L. kirschneri, L. borgpetersenii, L. noguchi, and L. santarosai. We also identified L. kmetyi in at least two patients with acute leptospirosis. This is the first time, to our knowledge, that this species has been identified in humans. The most prevalent genotypes were associated with L. interrogans serovars Icterohaemorrhagiae and Copenhageni, L. kirschneri serovar Bogvere, and L. borgpetersenii serovar Arborea. We were unable to identify nine strains at the serovar level and comparison of genotyping results to the MLST database revealed new secY alleles.

Conclusions: The overall serovar distribution in the French West Indies was unique compared to the neighboring islands. Typing of leptospiral isolates also suggested the existence of previously undescribed serovars.

Figure 1. Phylogenetic tree of leptospiral 16S rRNA gene sequences of reference strains (L. kirschneri serovar Grippotyphosa strain MoskvaV, L. interrogans serovar Icterohaemorrhagiae strain Verdun, L. santarosai serovar Shermani strain 1342K, L. borgpetersenii serovar Ballum strain Mus27, and L. noguchi serovar Panama strain CZ214K) and a set of clinical isolates from Guadeloupe (G) and Martinique (M).

The tree was drawn using the UPGMA (unweighted pair group method with arithmetic average) algorithm.

Figure 2. Representative PFGE patterns of NotI-digested genomic DNA from isolates from Martinique and Guadeloupe.

The genotype is indicated for each clinical isolate, and reference strains for serovars Panama, Icterohaemorragiae, Tbaquite, Bogvere, Beye, Szwajizak, Trinidad, Gorgas, Caribe, Ballum, Castellonis, Arborea, Sulzeae, Navet, Atchafalaya, Rama, Darien, Chagres, Bravo, Nicaragua, Bajan, Peruviana, and Atlantae. The molecular weight size marker is bacteriophage lambda DNA concatemers of 50 kb.

Figure 3. Phylogenetic relationships of leptospirosis isolates based on secY sequences.

The tree was drawn using the UPGMA (unweighted pair group method with arithmetic average) algorithm. The species and genotype are indicated. Circle sizes correspond to the numbers of strains of each genotype. Isolates from Martinique are highlighted by a red background.