Staphyloccous Aureus, CoNs Flashcards
Diagnosis of S.areus
B-hemolytic, gram (+) cocci , catalase (+), coagulase(+)
–> gold on blood agar
Infectious Route of S.areus (Transmission)
colonizes the skin and mucosa (Nasal Carriage), foreign bodies, CA-MRSA
Pathogenesis of S.areus
Virulence factors:
1) PVL toxins –> CA-MRSA (less virulent than HA-MRSA, which is more resistant)
2) Cytolytic toxins (α,γ,β,δ)
3) superantigens (TSST-1, enterotoxins-SEs)
4) Exfoliative toxins (causes SSSS)
5) exoenzymes
6) coagulase, hyalauroindase
*TSST : (Menstruation) Toxic Shock Syndrom Toxin
*SSSS: Staphylococcal Scalded Skin Syndrom
*Enterotoxins are associated with food- poisoning
*PVL: Panton-Valentine Leucosidin
Clinical Manifestations of S.areus
–> Rapid Onset of symptoms
1) Impetigo
2) mastitis (breast abscess)
3) Cellulitis
4) HA-BSI (increases endocarditis risk)
5) folliculitis/furuncles (boils): pyogenic infection of the hair follicle
6) necrostising fascilitits
7) osteomyelitis, septic arthritis
8) prosthetic joint infection
9) pneumonia & Empyema
Most important risk factor for Staphylococcal infections?
Nasal Carriage (colonization of the skin and mucous membrane , especially after surgery)
virulence factors causing SSSS (staphylococcis scalded skin syndrom)
2 exfoliative toxins:
1) ETA
2) ETB
–> Colonize skin not mucosal membranes
–> SSSS is self-limited (7-10d)
which is the most important resistance phenotype for S.Aureus & which is the agent of choice?
> Resistant phenotype: MRSA
Agent of choice: Vancomycin
*HA-MRSA is more resistant than
CA-MRSA, however, CA-MRSA is more invasive
*MRSA is resistant to all β-Lactams except for 5th Cephalosporins (Ceftaroline, Ceftobiprole)
*MRSA: methycillin-resistant S.areus
MRSA is resistant to all β-Lactams except for 5th ——————- (——————, —————-)
*MRSA is resistant to all β-Lactams except for 5th Cephalosporins (Ceftaroline, Ceftobiprole)
Diagnosis of CoNS
gram (+) cocci, Coagulase (-), catalase (+)
*CoNS : coagulase negative staphylococcus
Transmission of CoNS
colonizes skin
1) part of the skin flora –> gain access upon device or catheter insertion
2)foreign body material –> immunosupressed patients
pathogenesis/Virulence factor of CoNS
–> much less virulent than S.areus
VF–> Biofilm
clinical manifestaions of CoNS
ALWAYS THINK WHEN FOREIGN BODY MATERIAL PRESENT
1. Catheter-related bacteraemia
2. Prosthetic valve endocarditis (rarely in native) & cardiac device infections (e.g. pacemakers)
3. Vascular graft infection (e.g. after aortic aneurysm surgery)
4. CSF shunt infections (for hydrocephalus), causing ventriculitis & meningitis
5. Peritoneal dialysis catheter infections
6. Breast & penile implant infections
Treatment of CoNs
Vancomycin
