Loss of virulence of revertants from Staphylococcus aureus L-phase variants in comparison with the parent strain.

The L-forms of the Klecha 155 strain were induced in vitro by methicillin. After reversion, the strains were tested for 19 biochemical features and for susceptibility to penicillin, ampicillin and methicillin. Two reverted strains were less virulent for mice than the parent strain. It is concluded that the decrease in virulence of reverted Staph. aureus strains is correlated with changes in the chemical structure and composition of the cell wall after reversion from the L-phase variants.