Leptospira licerasiae, a zoonotic pathogen isolated from water sources in Santa Maria, Rio Grande do Sul, Brazil

Leptospira spp. is the causative agent of leptospirosis, a zoonotic disease prevalent worldwide, particularly in tropical regions. The bacterium can be transmitted directly through the urine of infected animals or indirectly via contact with contaminated environments, including soil and water sources. Water samples from streams, rainwater accumulations and drinking water were collected from Santa Maria, Rio Grande do Sul state (southernmost Brazil). The samples were submitted to the Laboratório de Diagnóstico e Pesquisa em Leptospirose (LabLepto) for inoculation in modified Ellinghausen-McCullough-Johnson-Harris medium and incubation at 28 °C. The inocula were evaluated weekly for a minimum of 90 days to identify morphological characteristics that are typical of Leptospira spp. One of the eight samples exhibited growth and morphology consistent with spirochetes. This sample was purified by filtration and subsequently sent for molecular identification by PCR and typing by secY gene sequencing. Genetic analysis revealed Leptospira licerasiae, belonging to the subclade P2 (intermediate group). This species has been previously isolated from environmental water and soil samples and associated with mild human infections. Nevertheless, this is the first documented environmental isolation of L. licerasiae in central Rio Grande do Sul. Although it exhibits lower virulence than classic pathogenic species, L. licerasiae should be included in epidemiological surveillance and One Health approaches due to its zoonotic potential and environmental persistence.