Rattus norvegicus (Norway rat) is the main reservoir host of pathogenic Leptospira, the causative agent of leptospirosis, in urban environments. Pathogenic Leptospira forms biofilms in the environment, possibly contributing for bacterial survival and maintenance. Nonetheless, biofilms have not yet been studied in natural animal reservoirs presenting leptospiral renal carriage. Here, we described biofilm formation by pathogenic Leptospira inside the renal tubules of R. norvegicus naturally infected and captured in an urban slum endemic for leptospirosis. From the 65 rats carrying Leptospira in their kidneys, 24 (37%) presented biofilms inside the renal tubules. The intensity of leptospiral colonization in the renal tubules (OR: 1.00; 95% CI 1.05–1.1) and the type of occlusion pattern of the colonized renal tubules (OR: 3.46; 95% CI 1.20–9.98) were independently associated with the presence of Leptospira biofilm. Our data showed that Leptospira interrogans produce biofilms during renal chronic colonization in rat reservoirs, suggesting a possible role for leptospiral biofilms in the pathogenesis of leptospirosis and bacterial carriage in host reservoirs.
We evaluated the renal colonization by Leptospira interrogans in
Rattus norvegicus (rats), as it is the major natural reservoir of
urban leptospirosis. We caught 72 R. norvegicus, out of which 32
were found to be positive for L. interrogans by immunofluorescence
assay. From these rats, we selected 17 and divided them into six groups based on the
mass-age/sex. We performed the immunohistochemistry test against L.
interrogans in the kidney sections of the rats and systematically counted
the colonized tubules (CTs) in 20 fields. The proportion of positive fields varied
from 5% to 95%. The number of CTs in 20 fields varied from 0.5 to 85.5. These
differences were not related to age or sex of the animals. The characterization of
leptospiral colonization patterns in the natural reservoirs is important to better
understand the host-pathogen interactions in leptospirosis.
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