Microbiology Test 4

Staphylococcus aureus

• Gram-positive

• Cocci

• Coagulase positive

• Causes pyogenic (pus-forming) and toxin-mediated infections

• Produces TSST-1 → toxic shock syndrome

• Produces exfoliative toxin → impetigo and scalded skin syndrome

• Associated with boils, abscesses, wound infections, and food poisoning

Staphylococcus epidermidis

• Gram positive

• Cocci

• Coagulase-negative

• Iatrogenic infections (catheters, prosthetics, incision sites)

• forms biofilms on medical devices

• Normal flora of the skin

• Opportunistic pathogen, especially in hospitalized patients

Staphylococcus saprophyticus

• Gram positive

• Cocci

• Coagulase-negative

• Causes UTIs, especially in sexually active young women

• Resistant to novobiocin (key diagnostic test)

• Normal flora of genitourinary tract

• Non-hemolytic on blood agar

Staphylococcus lugdunensis

• Gram positive

• Cocci

• Coagulase-negative

• Can cause acute endocarditis

• More virulent than most CoNS (coagulase-negative staph)

• β-hemolytic

• Often associated with skin and soft tissue infections