Abstract
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.
Highlights
Leptospirosis is an infectious disease of public health global importance [1]
Leptospirosis is an infectious disease caused by pathogenic Leptospira bacteria
Twenty-four (37%) rats were positive (p = 0.04) (Table 1) for renal biofilm according to colocalization of Alcian Blue (AB) staining (Fig 1A and 1B) and IHC anti-Leptospira (Fig 1C and 1D), confirming the presence of polysaccharidic matrix and Leptospira biofilms inside the proximal renal tubules of infected rats
Summary
It is estimated that more than one million cases and nearly 60 thousand deaths occur yearly in the world due to leptospirosis [2]. The incidence of this zoonotic disease is higher in developing and tropical countries, especially during rainy seasons [3,4]. Pathogenic Leptospira densely colonize the kidneys of rat reservoir hosts, where they form aggregates in the proximal renal tubules [9,10]. During infection in chronic animal models, leptospires form biofilm-like structures during renal tubular colonization [13], what may explain the antibiotic tolerance observed when the treatment occurs during the disease chronic phase [14]
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