Induction of stable L-forms of Salmonella typhi and Listeria monocytogenes

Stable L-forms of Salmonella typhi and Listeria monocytogenes were produced using penicillin (4500 units/ml) as inducer, and sucrose, normal horse serum and Mg++ as stabilizers. Stable L-forms were produced after 100 and 56 passages, then adapted to grow and multiply in a medium free of inducer and stabilizers so that they did not revert to parental forms even after 12 continuous passages.