Leptospirosis: toward a better understanding of the environmental lifestyle of Leptospira

Abstract

Leptospira is a complex bacterial genus which biodiversity has long been overlooked. In the recent years however, environmental studies have contributed to shed light on its original and current environmental habitat. Although very fragile bacteria in laboratories, Leptospira have been shown to successfully occupy a range of soil and freshwater habitats. Recent work has strongly suggested that biofilm formation, a multicellular lifestyle regulated by the second messenger c-di-GMP, might be one strategy developed to overcome the multiple challenges of environmental survival. Within the genus, a minority of pathogenic species have developed the ability to infect mammals and be responsible for leptospirosis. However, most of them have retained their environmental survival capacity, which is required to fulfill their epidemiological cycle. Indeed, susceptible hosts, such as human, suffer from various symptoms, while reservoir hosts stay asymptomatic and release bacteria in the environment. In this review, we discuss how c-di-GMP might be a central regulator allowing pathogenic Leptospira to fulfill this complex life cycle. We conclude by identifying knowledge gaps and propose some hypotheses that should be researched to gain a holistic vision of Leptospira biology.

Evolutionary insights into the emergence of virulentLeptospiraspirochetes

“…Pathogenic Leptospira (P1+) evolved from environmental bacteria in progressive trajectory of host-adaptation to animals through deep-time, likely beginning with the appearance of the first mammals [3]. Other Leptospira species are mostly environmental isolates but some P2 and P1- species may be responsible for asymptomatic to mild infections in both humans and animals [12–16, 21, 22].…”

Host population structure and rare dispersal events drive leptospirosis transmission patterns amongRattus norvegicusin Boston, Massachusetts, US

“…However, laboratory analysis of R. norvegicus infected with L. interrogans serovar Copenhageni revealed they shed leptospires continuously (10 5 −10 7 leptospires per mL) in their urine for the duration of the experiment (159 days) (22), suggesting that in this laboratory setting there was no such dormant state. Alternatively, Leptospira biofilm formation could take place in the environment (55, 56). It is important to note that because we are only analyzing the shared genomic space among all the rat derived L. interrogans genomes (core genome >2.1 million nts) there could be mutations or acquired/lost pan genomic content outside of the core genome that we did not detect.…”

Current treatment options for leptospirosis: a mini-review

“…In 50% of the suspected cases, laboratory testing and confirmation procedures are not performed; due to this knowledge, this feature can be recognized as a significant challenge regarding the dissemination of leptospirosis and a possible ineffective treatment in this regard ( Costa et al, 2015 ). As mentioned above, leptospirosis is a climate-sensitive, poverty-dependent and environment-borne infection ( Costa et al, 2015 ; Davignon et al, 2023 ).…”