Co-Infection by Leptospira montravelensis and Leptospira interrogans Serovar Pomona in Urine Samples of Donkeys and Pigs in Sardinia, Italy

Simple Summary: Leptospirosis is one of the most neglected zoonotic diseases in the world and humans can easily acquire the pathogen after exposure to water, soil, or mud contaminated with urine from infected animals. In September 2018, a leptospirosis outbreak caused by a pathogenic Leptospira genospecies interrogans was identified in one farm in North Sardinia, Italy. In addition, culture and isolation of a saprophytic Leptospira genospecies montravelensis from two urine samples (from one pig and one donkey) was reported for the first time, indicating that co-infection with more than one strain of Leptospira in the same reservoir host is possible. These results provide new information on the epidemiology of leptospirosis and on the genotypes circulating in Sardinia, emphasizing the conducting of active surveillance of leptospirosis in humans and animals. Abstract: Saprophytic leptospires are spirochetes enclosed within the non-pathogenic clade of the genus Leptospira, which in turn is subdivided into two subclades S1 and S2. To date, the microorganisms included in these subclades have been isolated from the environment in various parts of the world, and are believed to have no known animal reservoirs. After a case of Leptospira interrogans serovar Pomona was notified to the owner of a farm in Sardinia, all of the farm animals (11 pigs and 3 donkeys) were examined for the presence of Leptospira. Sera of all tested animals resulted positive for antibodies to Leptospira using a microscopic agglutination test (MAT). Moreover, nine (82%) kidney samples from pigs and three urine samples collected from donkeys (100%) tested positive for Leptospira DNA after qPCR. Results obtained after MLST analysis and sequencing of rrs, rpoB, and secY genes, performed on six Leptospira strains isolated in culture, revealed the presence of the genomo-species L. interrogans serovar Pomona in the kidney samples. Conversely, whole-genome sequencing combined with mean nucleotide identity revealed the presence of the saprophytic L. montravelensis in the urine samples. Our results report, for the first time, the isolation of a saprophytic species from mammalian urine, suggesting a new ecological specialization for these bacteria, with a possible transition from free-living to a symbiotic lifestyle. Further studies will have to be conducted to understand the evolution of virulence of these bacteria, potential infectivity, and possible public health implications.

Automated summary

Leptospirosis, a neglected zoonotic disease, can be easily acquired by humans through exposure to water, soil, or mud contaminated with urine from infected animals. An outbreak caused by a pathogenic Leptospira interrogans was identified on a farm in North Sardinia, Italy, highlighting the need for active surveillance in humans and animals. In addition, a saprophytic Leptospira montravelensis was isolated from urine samples collected from a pig and a donkey, suggesting the possibility of co-infection with multiple strains in the same reservoir host.