C. Topic 3 (Staphylococcus infections)

How to recognize staph bacteria?

• Gram-positive cocci

• grow in clusters

• Staph =

• Strep =

• Staph = clusters

• Strep = chains

What are the main things we talk about in staph bacteria?

• types

• virulence factor

• toxin

• diseases it causes

The main types of staph you need to know

• Staphylococcus aureus → BIG ONE (causes most disease)

• Staphylococcus epidermidis → opportunistic

• Staphylococcus saprophyticus → UTIs in young women

Staphylococcus aureus

• Coagulase POSITIVE ⭐⭐⭐

• primary pathogen

• golden pigment

• beta-hemolytic

Staphylococcus epidermidis

• coagulase NEGATIVE

• skin flora

• opportunistic

 Staphylococcus saprophyticus

• coagulase NEGATIVE

• UTI in young women (18–30)

KEY VIRULENCE FACTORS

• Coagulase

  • clots blood

  • forms abscess
    👉 signature of S. aureus

• Protein A

  • binds IgG

  • blocks immune response
    👉 immune evasion

• Hyaluronidase

  • helps spread through tissue

MAIN DISEASES

SKIN (MOST COMMON)

• abscess

• boils

• cellulitis

• wound infections

👉 pus-forming

 

🦠 IMPETIGO ⭐⭐

• superficial

• crusting lesions

• kids

 

💀 INVASIVE ⭐⭐⭐

• bacteremia

• endocarditis

• pneumonia

• osteomyelitis ⭐⭐⭐ (MOST COMMON CAUSE)

TOXINS - overview

Exfoliative toxin

TSST (Toxic Shock Syndrome Toxin)

Enterotoxin

Exfoliative toxin

Staphylococcal scalded skin syndrome

• skin peels

TSST (Toxic Shock Syndrome Toxin)

superantigen

• fever

• hypotension

• rash

• tampon association

Enterotoxin

food poisoning

• vomiting

• diarrhea

• heat-stable toxin

MRSA - topics overview

• what

• how

• where

MRSA

WHAT

• Methicillin-resistant Staphylococcus aureus

MRSA

HOW

• Altered penicillin-binding protein (PBP)

👉 drug target changed

MRSA

WHERE

• hospital

• community

👉 looks like spider bite

 MUST-KNOW ASSOCIATIONS

Coagulase positive →

👉 Clusters →

👉 UTI (young woman) →

👉 Osteomyelitis →

👉 Scalded skin →

👉 Shock + tampon →

👉 Food poisoning →=

👉 MRSA → Altered PBP

 

 Coagulase positive → S. aureus

👉 Clusters → Staph

👉 UTI (young woman) → S. saprophyticus

👉 Osteomyelitis → S. aureus

👉 Scalded skin → Exfoliative toxin

👉 Shock + tampon → TSST

👉 Food poisoning → Enterotoxin

👉 MRSA → Altered PBP