Micro Final Review$$

I. Gram$-$Positive Bacteria$$

$1.$ Identification:$$

o microscopic morphology: cocci vs$.$ chains.$$

o Key reactions: Coagulase test for Staphylococcus aureus.$$

o Examples:$$

$$ Staphylococcus aureus: Large, golden$-$yellow, beta$-$hemolytic colonies; positive$$

coagulase reaction.$$

$$ Streptococcus pyogenes: Beta$-$hemolytic colonies, bacitracin sensitivity$,$ causes$$

pharyngitis.$$

$2.$ Differentiation:$$

o Hemolysis patterns:$$

$$ Alpha: Partial hemolysis $($green zone$).$

$$ Beta: Complete hemolysis $($clear zone$).$

$$ Gamma: No hemolysis.$$

o Bacitracin susceptibility $($Group A strep$).$

$3.$ Clinical Relevance:$$

o Common infections: Impetigo, toxic shock syndrome.$$

o Diagnosis from specimens $($e$.$g$.,$ throat swabs, wound cultures$).$