Staphylococcus

genus Staphylococcus

gram positive spherical cells about 1um in diameter, arranged in grapelike irregular clusters

nonmotile, nonsporeforming

aerobic/microaerophilic

produces round, smooth, shiny, raised colonies

45+ species

S. aureus colonies

gray to deep golden yellow 3-4 mm in diameter surrounded by beta hemolysis

coagulase negative staphylococci

normal flora that can cause opportunistic infections, typically with implanted devices

• S. epidermidis

• S. lugdunensis

• S. warneri

• S. hominis

pathogenic staphylococci

hemolyze blood, coagulate plasma, produce enzymes and toxins

coagulase positive staphylococci

S. aureus is the only species

S. aureus pathogenic capacity

combined effect of extracellular factors and toxins as well as invasive properties of the strain

S. aureus food poisoning

caused by a heat-stable staphylococcal enterotoxin

protein A

surface protein of S. aureus

a type of MSCRAMM

mediates bacterial attachment to host cells

virulence factor

S. aureus polysaccharide capsule

inhibits phagocytosis

S. aureus produces:

catalase

coagulase

hyaluronidase

staphylokinase

4 hemolysins:

• alpha hemolysin

• beta toxin

• delta toxin

• gamma hemolysin

epidermolytic toxins

toxic shock syndrome toxin 1

15 enterotoxins

S. aureus beta hemolysin

acts on a broad spectrum of eukaryotic cell membranes

S. aureus beta toxin

degrades sphingomyelin and is toxic for many kinds of cells

S. aureus delta toxin

disrupts biologic membranes and may have a role in diarrheal diseases

S. aureus gamma hemolysin

leukocidin that lyses white blood cells and leads to massive release of inflammatory mediators responsible for necrosis and severe inflammation

S. aureus exfoliative toxin A

epidermolytic toxin encoded on a phage

heat stable

S. aureus exfoliative toxin B

epidermolytic toxin encoded on a plasmid

heat labile