CLINICALLY SIGNIFICANT STAPHYLOCOCCUS

S. saprophyticus is commonly found on

Contaminated meat products

S. saprophyticus general characteristics

Gram (+)

Non-motile

Non-spore forming

Facultative anaerobe

S. saprophyticus BCM tests

Catalase (+)

Urease (+)

Coagulase (-)

Novobiocin R

S. saprophyticus is a common cause of

Uncomplicated UTI in sexually active young women

S. saprophyticus associated diseases

Uncomplicated UTI (rectum to anus to perineum to urethra)

Formation of Urinary Stones due to Urease forming ammonia

S. saprophyticus virulence factors

Forms biofilm

Urease - Neutralizes acidic environment in urinary tract

S. saprophyticus treatment

Nitrofurantoin

SMX-TMP

Removal of indwelling medical devices w/ biofilms

S. epidermidis characteristics

Gram +

Non-motile

Non-spore forming

Facultative Anaerobe

S. epidermidis morphology

Grapes (staph)

Gram + cocci in clusters

S. epidermidis diagnosis and culture

Coagulase -

Non-mannitol fermenter (MSA remains pink/red)

BAP: White colonies

S. epidermidis BCM Tests

Catalase +

Urease +

Coagulase -

Novobiocin S

S. epidermidis associated diseases

Catheter-related infections

Prosthetic Valve Endocarditis

Prosthetic Joint Infections

S. epidermidis treatment

Vancomycin

Oxacillin or Nafcillin - for methicillin resistant

Removal of infected medical device

S. aureus

BAP distinctive morphology

MSA results

BAP: Golden-yellow colonies surrounded by beta (complete) hemolysis

MSA: Mannitol fermenter (pink/red to yellow)

S. aureus is a [blank] anaerobe

Facultative Anaerobe

S. aureus motility and sporulation

Non-motile, non-spore forming

S. aureus DX and Culture

Coagulase +

Catalase +

Recall agar plate morphology

S. aureus virulence factors

Protein A - antiphagocytic

Cell wall - peptidoglycan and murein

Fibronectin-binding protein

Clumping factor and capsular polysaccharide

Effect of H2O2 drops on cat + Staphylococci vs cat - genera

Staph colonies will foam up (cat +)

Test to differentiate S. aureus from other Staph

Coagulase test - aureus is coagulase +

Clumps will form as fibrinogen turns to fibrin

S. aureus infections by migration

CNS - meningitis, epidural abscess

Lungs - pneumonia

Heart - endocarditis, valve vegetations

Muscle - pyomyositis

Bone - Osteomyelitis

Joints - septic arthritis

Bloodstream - septic thrombophlebitis

S. aureus toxins

Toxic Shock Syndrome Toxin-1 (TSST-1)

Panton-Valentin Leukocidin Toxin

Hemolysin

Exfoliatin

Enterotoxin

S. aureus TSST-1 MOA

Produced at site of infection

Binds MHC II causing cytokine storm

Toxic shock syndrome - fever, rash, low BP, poor end-organ effusion

S. aureus Panton-Valentine Leukocidin Toxin MOA

Perforates and kills leukocytes, causing necrosis, causing inflammation

Can lead to end organ failure

S. aureus Hemolysin MOA

Destroys erythrocytes, releasing hemoglobin - bacteria needs iron

S. aureus Four hemolysins and their functions

alpha - eukaryotic cell membrane

beta - degrades sphingomyelin

delta - disrupts biologic membranes

gamma - lyses WBC

S. aureus Exfoliatin MOA

Causes Staph Scalded Skin Syndrome/Ritter’s disease

S. aureus Enterotoxin MOA

Remains on food even after bacterial death, withstands boiling

Can cause Toxic Shock Syndrome (rare)

S. aureus Resistance factor to penicillins

Beta lactamases

S. aureus Resistance to Methicillin

mecA gene encodes special PBPs

Tx of S. aureus

Antibiogram for susceptible drugs

Clindamycin

Vancomycin

Tetracyclines

SMX-TMP

Linezolid

Tigecycline

Daptomycin

Quinuristin-Dalfopristin