Skin and Systemic Infections Overview

Skin Infections

• Boils and abscesses are characterized by red, swollen, and painful lumps filled with pus
• Impetigo is characterized by fluid-filled blisters that rupture and form a yellow crust

Systemic Infections

• Bacteremia presents with high fever, chills, and fatigue
• Pneumonia presents with difficulty breathing and chest pain
• Osteomyelitis presents with bone pain and swelling

Toxigenic Syndromes

• Ingesting contaminated food can lead to vomiting and diarrhea
• Toxic shock syndrome symptoms include low blood pressure, fever, and rash

Healthcare-Associated Infections (HAIs)

• Staphylococci are a common cause of infections in hospitals, especially in patients with surgical wounds or medical devices

Diagnosis

• Staphylococci can be easily cultured on nutrient agar or blood agar
• Culture: Staphylococci colonies appear golden (S.aureus) or white (S.epidermidis)
  • Blood agar: is a rich, non-selective medium used to grow a wide variety of bacteria, including Staphylococcus species.
    • It helps in the identification of hemolytic activity, which is crucial for differentiating species.
    • Composition:
      • Nutrient-rich agar: Provides essential nutrients for bacterial growth.
      • Sheep blood (5-10%): Supports the growth of fastidious organisms and allows for the observation of hemolysis.
    • Hemolysis Differences:
      • Alpha (α) Hemolysis: Partial lysis of red blood cells, resulting in a greenish discoloration around colonies. This is typical for Streptococcus pneumoniae and some Staphylococcus species.