%0 Journal Article %A Bruns, W. %A Keppeler, H. %T Extracellular and membrane-bound β lactamase of Staphylococcus aureus: their importance for the expression of penicillin resistance %D 1987 %J Journal of Medical Microbiology, %V 23 %N 2 %P 133-139 %@ 1473-5644 %R https://doi.org/10.1099/00222615-23-2-133 %I Microbiology Society, %X Summary The synthesis and excretion of β 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 β-lactamase production was maximally induced with penicillin G or ampicillin, about 50% of the β 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 β 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 β lactamase is insufficient for full protection of the staphylococcal cells. %U https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-23-2-133