Download S. aureus

S. aureus Biofilms
Staphylococcus aureus
•ALL STAPHYLOCOCCI are:
• 1. Gram-positive
• 2. Cocci
• 3. Clusters (Grape clusters)
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Levels of Infection
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Colonization
Skin infections
Metastatic Infections
Toxinoses
Colonization
• Asymptomatic
• The nares and throat of 3050% of normal healthy
adults are colonized
• Adhesins involved in
colonization
• This can result in spread of
the infection to others
• Autoinoculation
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S. aureus infections
• Skin infection. Can be caused by autoinoculation
or spread from person-to-person (sometimes
animal-to-person)
• S. aureus is the most common cause of pyogenic
skin infections
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Folliculitis
Furuncle
Carbuncle
Impetigo
Cellulitis
Necrotizing Fasciitis
Folliculitis
• Superficial
infection of the
hair follicle
• Self-limiting
Furuncle
• Deeper-seated than
folliculitis
• Pyogenic - abscess
Carbuncle
• Furuncles
fused together
Impetigo
• Contagious
• Usually on face
• Bullous impetigo larger bullae, may be
on body
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Cellulitis
• Cellulitis is usually
associated with
Streptococcus
• Can accompany foot
ulcers in diabetic
patients
• Deep tissue infection
• Subcutaneous or
submucosal
Necrotizing Fasciitis
Infection of the
superficial muscle
fascia and adjacent
subcutaneous tissue.
More often caused by
Group A Strep
Metastatic S. aureus infections
• Endocarditis
• Pneumonia (nosocomial, CF-related,
post-influenza)
• Pyomyositis
• Epidural abscess
• Brain abscess
• Osteomyelitis
OSTEOMYELITIS
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• Collagen
binding
protein
S. aureus Toxinoses
• Toxic shock syndrome
• Scalded skin syndrome
• Food poisoning
Toxic Shock Syndrome
• Associated with tampon use
in early 80’s - ignored for a
while but is re-emerging
• Soccer shoes in England
• Must be colonized with a
TSST-producing strain and
must lack antibodies
• High fever, flushing,
sloughing of skin on
extremeties
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Staphylococcal superantigens
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Scalded Skin Syndrome
• Usually in children
and neonates
• Erythema &
sunburn-like rash
• Desquamation due
to exfoliatin toxin
Food Poisoning
• Food poisoning vs. food infection:
staphylococcal enterotoxins (SEA, SEB
etc.)
• 2-6 hours between ingestion and
symptoms
• The toxin mainly induces vomiting
• Staph is salt tolerant & can grow in foods
that other bacteria can’t like ham
Antibiotic resistance in
S. aureus
1944
-lactamase
1940
Penicillin
1960
Methicillin/
Oxacillin
1970’s
mecA
1996-VISA
2002
VanA
Vancomycin
2000’s
Daptomycin
S. aureus: The “Superbug”
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S. aureus Biofilms
Diabetic foot ulcer
Catheter
Endocarditis
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Jefferson et al. AAC 49(6); 2467
55 yo wm with Type II DM had severe osteoarthritis of the rt knee for
years. 03/07 underwent rt total knee replacement. PostOp course
uncomplicated. Did well until 5/07 when he developed increasing pain,
swelling, and erythema of rt knee joint. Aspiration of knee joint
revealed frank pus. Culture grew MSSA. Patient admitted and treated
with IV vancomycin (penicillin allergy). ID consulted and
recommended removal of joint hardware followed by prolonged IV
vanc. Patient and family decided against joint removal and opted for
debridment and prolonged antibiotics. The joint was irrigated and
debrided. Patient received 6 wks IV vanc with rifampin followed by 2
mos PO bactrim. Joint improved without significant pain and patient
was able to ambulate. 8-07 patients PC stopped bactrim. 5 days later,
patient presented with increasing erythema, pain and swelling of the
knee joint w/ fevers. Aspiration of the joint revealed frank pus and
cultures grew MSSA. He was taken to the OR and all joint hardware
was removed, an antibiotic spacer was placed, and he will receive an
additional 6 wks vanc and rifampin before consideration of joint
replacement.
Inserted synthetic devices
Polysaccharide
intercellular adhesin
PIA/PNAG
What controls biofilm formation in
S. aureus?
O2
• External,
environmental
factors
– Ethanol, NaCl,
glucose
• Internal
regulators
– IcaR,
B,
SarA
NaCl
EtOH
Glucose
B
S
SarA
?
-
icaR
-
icaA icaD icaB
icaC
icaR
• Phase variation
– IS elements
IcaB
Bioinformatics Approach
• Different strains have different
biofilm-forming capacities.
• Can we predict biofilm formation
based on sequence analysis?