Medical Microbiology

Staphylococcus 231

Extracellulartoxinsandenzymes.S.aureussecretesnumerousenzymesand

toxinsthatdetermine,togetherwiththefinestructuresdescribedabove,the

pathogenesisoftheattendantinfections.Themostimportantare:

&Plasmacoagulaseisanenzymethatfunctionslikethrombintoconvert

fibrinogenintofibrin.Tissuemicrocoloniessurroundedbyfibrinwallsare

difficulttophagocytose.

&a-toxincanhavelethalCNSeffects,damagesmembranes(resultingin,

amongotherthings,hemolysis),andisresponsibleforaformofdermone-

crosis.

Staphylococcusaureus

Fig.4. 1 a Gramstaining

of a pus preparation:

Gram-positivecocci,some

ingrapelikeclusters.Clini-

caldiagnosis:furunculosis.

bCultureonbloodagar:

convexcolonieswithyel-

lowishpigmentandporce-

lainlikesurface.

4

Kayser, Medical Microbiology © 2005 Thieme