Survival of Leptospira interrogans serovar pomona in an acidic soil under simulated New Zealand field conditions

Abstract

Leptospira interrogans serovar pomona was found to survive for at least 42 days in a typical New Zealand soil under simulated winter field conditions. The soil was markedly acidic with a pH of 5.5 and survival times were not reduced even when its water content was only 23%. The values of both these parameters are considerably less than previously recorded for the survival of leptospires in soil. Two methods were used to recover leptospires from the soil microflora. One was the culture of a membrane filtrate in EMJH media with or without contaminant-suppressing additives and the other was the direct inoculation of soil-washings into hamsters. Both techniques proved to equally sensitive. It was estimated that following the addition of 5 X 10(8) leptospires to the soil samples less than 2 X 10(4) were present after six weeks.