The Journal of Medical Microbiology, Vol 23, Issue 2 133-139, Copyright © 1987 by Society for General Microbiology
Extracellular and membrane-bound beta lactamase of Staphylococcus aureus: their importance for the expression of penicillin resistance
W. Bruns and H. Keppeler
The synthesis and excretion of beta lactamase by several strains of
Staphylococcus aureus from different clinical sources and the ability of
both the extracellular and membrane-bound enzyme to mediate penicillin
resistance was studied. When beta-lactamase production was maximally
induced with penicillin G or ampicillin, about 50% of the beta lactamase
was excreted from the cells, the amount of extracellular enzyme correlating
well with the degree of resistance established by an in-vitro test model.
From penicillin-binding experiments it became apparent, however, that the
membrane-bound beta lactamase can also constitute a barrier, strong enough
on its own to prevent penicillins from reaching their target. This could be
of clinical relevance if, under certain conditions in vivo, the
extracellular beta lactamase is insufficient for full protection of the
staphylococcal cells.
