Among the selected strains, only L. murinus CRL 1695 showed a high autoaggregative pattern. Low or medium autoaggregation index strains, but able to settle down after long periods of incubation, were further studied. They were subjected to a second autoaggregation test, where 10% (vol./vol.) of their depleted culture supernatants were added to PBS. L. johnsonii CRL 1693, L.johnsonii CRL 1701 and L. johnsonii CRL 1706 showed an increased aggregative index by this technique.