3.06 Staphylococcus Species

Microbiology review for the USMLE Step 1 Exam

• Staphylococcus bacteria are gram-positive cocci that form clusters in the shape of grapes on a vine
• Three pathogenic species of staph: staph aureus, staph epidermidis, and staph saprophyticus
• Differentiation between species can be done using coagulase and novobiocin sensitivity tests
• Staph aureus is a major pathogen that causes many severe infections including toxic shock syndrome, septic arthritis, acute endocarditis, gastroenteritis, pneumonia, and staphylococcal scalded skin syndrome
• Toxic shock syndrome can be caused by tampons, soft tissue infections, post-surgical infections, and retained foreign bodies
• Staphylococcal scalded skin syndrome, or Ritter disease, is characterized by exfoliative damage to the skin and mainly affects newborns within 48 hours of birth
• Staph aureus can spread hematogenously and affect many parts of the body, particularly the heart and joints.
• Gastroenteritis caused by staph aureus is caused by consumption of exotoxins produced by the bacteria.