Leptospira interrogans Retains Direct Virulence After Long Starvation in Water

Area of Science:

• Environmental microbiology
• Infectious diseases
• Zoonosis research

Background:

• Leptospirosis is primarily known as a zoonotic disease, but it can also be environment-borne through contaminated soil or water.
• Few studies have investigated the survival and virulence of pathogenic Leptospira in freshwater environments.
• Understanding Leptospira survival in water is crucial for assessing environmental risks and implementing control strategies.

Purpose of the Study:

• To evaluate the survival and virulence of pathogenic Leptospira spp. in water microcosms over a two-year period.
• To investigate the direct infectious potential of Leptospira after prolonged survival in nutrient-deprived conditions.
• To explore the physiological adaptations of Leptospira in harsh freshwater environments.

Main Methods:

• Inoculation of Leptospira strains (L. interrogans, L. borgpetersenii, L. biflexa) into sterile bottled and non-ionized water microcosms.
• Assessment of bacterial survival using molecular, microscopic, and cultural methods over 24 months.
• Evaluation of direct virulence through animal challenge experiments without re-culturing.

Main Results:

• Pathogenic Leptospira demonstrated survival for over one year in water under nutrient-deprived conditions.
• L. interrogans successfully caused systemic infection in susceptible animals directly after the prolonged survival period.
• Evidence suggests Leptospira enters a physiological "survival" state in challenging freshwater conditions.

Conclusions:

• Pathogenic Leptospira can persist and remain virulent in freshwater for extended periods, posing a direct infection risk.
• This study is the first to report direct host infection by Leptospira following long-term survival in nutrient-deprived water.
• Findings underscore the critical importance of environmental surveillance and prevention strategies for leptospirosis, particularly concerning freshwater sources.