Isolation and genetic detection of pathogenic Leptospira spp. from environmental soils and water in Central Luzon, Philippines

Objective: To determine the prevalence, environmental distribution and genetic identity of Leptospira species in the provinces of Central Luzon, Philippines. Methods: A total of 135 soil and water samples were collected from all provinces in Central Luzon, Philippines. Soil samples were soaked in HEPES buffer and the aqueous phase was transferred to liquid 2× Korthof's medium supplemented with 10× STAFF to prevent the growth of microbial contaminants. Leptospires were isolated using a 0.2 μm syringe filter. 23S rRNA PCR test was used to detect the isolates belonging to genus Leptospira, flaB PCR test was used to detect pathogenic Leptospira and 16S rRNA gene sequencing was used to determine the genomospecies of isolates. Results: 23S rRNA PCR test revealed that 77 samples belonged to genus Leptospira. Three isolates showed positive results for the flaB-PCR assay. This result suggests that the isolates Ta8, Au4 and Au8 were pathogenic Leptospira. Phylogenetic analysis using the 16S rRNA gene revealed that one isolate from Aurora might belong to the pathogenic species Leptospira kmetyi. Conclusions: This study showed the presence of saprophytic and pathogenic leptospires in the environmental soils and water of Central Luzon, Philippines.