Leptospira Is an Environmental Bacterium That Grows in Waterlogged Soil

Microbiology Spectrum

Shin-ichi Yoshida¹  Sharon Y. A. M. Villanueva²  Mitsumasa Saito³  Nina G. Gloriani⁴  Yasutake Yanagihara⁵  Hiroshi Kida⁵  Toshiki Sekiya⁵  Masashi Shingai⁵  Chimuka Handabile⁵  Naoki Nomura⁵  Marumi Ohno⁵  Hideaki Higashi⁵  Toshiyuki Masuzawa⁶ 

[1] Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan;Department of Medical Microbiology, College of Public Health, University of the Philippines–Manila, Manila, Philippines;Department of Microbiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan;Institute of Pathology, St Luke’s Medical Center, Quezon City, Philippines;International Institute for Zoonosis Control, Hokkaido University, Sapporo, Japan;Laboratory of Microbiology and Immunology, Faculty of Pharmaceutical Sciences, Chiba Institute of Science, Chiba, Japan;

关键词: Leptospira;    leptospirosis;    waterlogged soil;    survival in soil;   

DOI  :  10.1128/spectrum.02157-21

来源: DOAJ

【 摘 要 】

ABSTRACT Leptospirosis is a zoonotic disease caused by infection with pathogenic leptospires. Consistent with recent studies by other groups, leptospires were isolated from 89 out of 110 (80.9%) soil or water samples from varied locations in the Philippines in our surveillance study, indicating that leptospires might have a life cycle that does not involve animal hosts. However, despite previous work, it has not been confirmed whether leptospires multiply in the soil environment under various experimental conditions. Given the fact that the case number of leptospirosis is increased after flood, we hypothesized that waterlogged soil, which mimics the postflooding environment, could be a suitable condition for growing leptospires. To verify this hypothesis, pathogenic and saprophytic leptospires were seeded in the bottles containing 2.5 times as much water as soil, and bacterial counts in the bottles were measured over time. Pathogenic and saprophytic leptospires were found to increase their number in waterlogged soil but not in water or soil alone. In addition, leptospires were reisolated from soil in closed tubes for as long as 379 days. These results indicate that leptospires are in a resting state in the soil and are able to proliferate with increased water content in the environment. This notion is strongly supported by observations that the case number of leptospirosis is significantly higher in rainy seasons and increased after flood. Therefore, we reached the following conclusion: environmental soil is a potential reservoir of leptospires. IMPORTANCE Since research on Leptospira has focused on pathogenic leptospires, which are supposed to multiply only in animal hosts, the life cycle of saprophytic leptospires has long been a mystery. This study demonstrates that both pathogenic and saprophytic leptospires multiply in the waterlogged soil, which mimics the postflooding environment. The present results potentially explain why leptospirosis frequently occurs after floods. Therefore, environmental soil is a potential reservoir of leptospires and leptospirosis is considered an environment-borne as well as a zoonotic disease. This is a significant report to reveal that leptospires multiply under environmental conditions, and this finding leads us to reconsider the ecology of leptospires.

【 授权许可】

Unknown