Persistence of Mycobacterium bovis BCG in Soil and on Vegetables Spray-Irrigated with Sewage Effluent and Sludge.

Survival of Mycobacterium bovis BCG on garden plots spray-irrigated with sewage effluent or sludge was studied to determine persistence of mycobacteria under conditions approximating current practices. The D value (90% reduction time) in effluent-sprayed soil was 11 days, and in sludge-sprayed soil it was 8 days. On effluent-sprayed radishes, the D value was 6 days, and on sludge-sprayed radishes, 4 days; however, this difference was not significant. Isolation from lettuce was too erratic to determine a true survival rate, but the organism was isolated sporadically for up to 35 days.