The selection of penicillin-resistant staphylococci on murine skin.

The survival of staphylococci on mouse skin and on glass has been studied using paired isolates, isogenic but for a penicillinase plasmid. In general, there is a slight tendency for the penicillin-resistant isolates to survive better than the sensitive variants. In one staphylococcus it was possible to compare the effect of two different penicillinase plasmids. One gave a slightly enhanced survival but the other was detrimental to the host cell's survival. The effect seems not to be related to desiccation or to the effect of lipid.