Identification of Leptospira Species in Environmental Soil of Urban Settlements in Cambodia

Background: Leptospirosis represents a major public health threat in Cambodia. To help establish preventive strategies for leptospirosis, we isolated and identified Leptospira from soil collected in Phnom Penh and its neighboring province during the dry and rainy seasons. Materials and Methods: Soil samples were collected from 15 sites in the Phnom Penh metropolitan area and Kandal Province in 2019 and 2020. A total of 120 soil samples were collected and analyzed after culturing. Cultured isolates were identified at the species level using 16S rRNA and gyrB gene sequencing analysis. Results: The positive culture rate for Leptospira was significantly higher for samples collected during the rainy season (31 out of 60 samples, 51.7%) than during the dry season (19 out of 60 samples; p < 0.05, chi-squared test). In terms of sampling area, 10 (35.7%) and 13 (46.9%) soil samples from Phnom Penh and 9 (28.1%) and 18 (56.3%) soil samples from Kandal Province were culture-positive when collected during the dry and rainy seasons, respectively. Three isolates from the Kandal samples collected during the dry season were categorized as pathogenic clade type P1 according to 16S rRNA and gyrB sequence analyses. In addition, samples collected during the rainy season from Phnom Penh and Kandal Province (three each) were categorized as clade type P1. The samples with isolates in clade type P1 were collected from riverbanks during both the dry and rainy seasons and from a hospital garden during the rainy season. Conclusions: This is the first report on the isolation of clade P1 Leptospira species in environmental soil samples from Cambodia. Environmental soil appears to be a reservoir for Leptospira in the capital city and surrounding areas of Cambodia. This study contributes to the understanding of Leptospira species distribution in Asian countries.