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Continuous Excretion of Leptospira borgpetersenii Ballum in Mice Assessed by Viability Quantitative Polymerase Chain
Marie-Estelle Soupé-Gilbert1, Emilie Bierque1, Sophie Geroult1
1Institut Pasteur International Network, Institut Pasteur in New Caledonia, Leptospirosis Research and Expertise Unit, Nouméa Cedex, New Caledonia.
Abstract:
Rodents are the main reservoir animals of leptospirosis. In this study, we characterized and quantified the urinary excretion dynamics of Leptospira by Mus musculus infected with 2 × 108 virulent Leptospira borgpetersenii serogroup Ballum. Each micturition was collected separately in metabolic cages, at 12 time points from 7 to 117 days post-infection (dpi). We detected Leptospira in all urine samples collected (up to 8 per time point per mouse) proving that Leptospira excretion is continuous with ca. 90% live L. borgpetersenii Ballum, revealed by viability quantitative polymerase chain reaction. Microscopic visualization by Live/Dead fluorescence confirmed this high proportion of live bacteria and demonstrated that L. borgpetersenii Ballum are excreted, at least partly, as bacterial aggregates. We observed two distinct phases in the excretion dynamics, first an increase in Leptospira concentration shed in the urine between 7 and 63 dpi followed by a plateau phase from 63 dpi onward, with up to 3 × 107Leptospira per mL of urine. These two phases seem to correspond to progressive colonization of renal tubules first, then to stable cell survival and maintenance in kidneys. Therefore, chronically infected adult mice are able to contaminate the environment via urine at each micturition event throughout their lifetime. Because Leptospira excretion reached its maximum 2 months after infection, older rodents have a greater risk of contaminating their surrounding environment.
Insights
Mice infected with Leptospira borgpetersenii continuously shed live bacteria in their urine for their lifetime. Urinary Leptospira concentration increases for two months, then plateaus, highlighting chronic rodent infection risks.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Zoonotic Pathogens
Background:
- Rodents are primary reservoirs for leptospirosis, a significant zoonotic disease.
- Understanding pathogen shedding dynamics is crucial for disease control.
Purpose of the Study:
- To characterize and quantify urinary excretion dynamics of Leptospira in infected mice.
- To determine the viability and patterns of Leptospira shedding over time.
Main Methods:
- Infection of Mus musculus with virulent Leptospira borgpetersenii serogroup Ballum.
- Separate collection of urine via micturition at 12 time points post-infection (7-117 dpi).
- Detection and quantification of Leptospira using qPCR, viability assays, and fluorescence microscopy.
Main Results:
- Leptospira was detected in all urine samples, indicating continuous excretion.
- Approximately 90% of excreted Leptospira borgpetersenii were viable, often in aggregates.
- Excretion increased from 7 to 63 dpi, followed by a plateau phase up to 3 × 10^7 bacteria/mL.
Conclusions:
- Chronically infected mice continuously contaminate the environment through urine throughout their lives.
- Higher bacterial concentrations are shed later in the infection course.
- Older infected rodents pose an increased risk of environmental contamination.
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