Staphylococci | MIDTERMS

• S. lugdunensis can be found on human skin but also causes serious invasive disease such as endocarditis, septicemia, and osteomyelitis.
• S. saprophyticus causes UTIs, especially in young women.
• Staphylococcus epidermidis is the most common cause of catheter-associated urinary tract infection.
• Staphylococcus epidermidis is the most common cause of nosocomial infection due to its ability to form biofilms.
• The pathogenesis of staphylococcal diseases involves adherence to host tissues through MSCRAMMs (microbial surface components recognizing adhesive matrix molecules).
• Staphylococcus epidermidis is the most common coagulase-negative staphylococcus (CNS) and is part of normal flora on human skin.
• Coagulase negative staphylococci are associated with nosocomial infections like prosthetic joint infections, surgical site infections, and intravascular device related infections.
• S. aureus produces coagulase enzyme that converts fibrinogen into fibrin, leading to clot formation around the bacteria.
• Staphylococci produce coagulase, which converts fibrinogen into insoluble fibrin clots.
• Staphylococcus are catalase producing, gram-positive bacteria that appear in singly, in pairs, or in clusters
• The genus name staphylococci comes from the Greek word "staphle" which means branches of grapes
• Staphylococci are members of the newly formed family Staphylococcaceae
• Micrococci are catalase producing, coagulase-negative, gram-positive cocci found in the environment and as members of the indigenous skin microbiota
• Micrococci are recovered with staphylococci and can be differentiated easily from coagulase-negative staphylococci (CoNS)
• Micrococci also produce yellow pigment
• Gram-positive cocci that are recovered with staphylococci include: Rothia mucilaginosa, Aerococci, Alloiococcus otitis
• Staphylococci are nonmotile, nonspore-forming, and aerobic or facultatively anaerobic, except for S. saccharolyticus which is an obligate anaerobe
• Colonies produced after 18-24 hrs of incubation are medium-sized 4-8mm and appear cream-colored, white, or rarely light-gold, and buttery-looking
• Rare strains of staphylococci are fastidious and require carbon dioxide, hemins, and menadione for growth
• Small colony variants of staphylococci grow on media that contains blood and after 48hrs of incubation, some species show beta hemolysis
• Staphylococcus are normal inhabitants of the skin and mucous membranes of humans and some animals
• Staphylococcus are differentiated by the coagulase test, where a positive test indicates clotting due to staphylocoagulase
• Staphylocoagulase-forming staphylococci include: S. aureus, S. intermedius, S. delphini, S. lutrae, and some strains of S. hyicus
• S. lugdunensis and S. schleiferi can be occasionally mistaken for coagulase-positive staphylococci (CoPS) due to the presence of clumping factor causing bacterial cells to agglutinate in plasma
• Coagulase-positive isolates from humans are considered to be S. aureus
• S. aureus causes cutaneous infections, purulent abscesses, bacteremia, septicemia, food poisoning, SSS, and TSS
• Commonly recovered CoNS include: S. epidermidis and S. saprophyticus
• Staph epidermidis causes healthcare-acquired or nosocomial infections
• Staph saprophyticus causes UTI in adolescent girls and young women
• Staph haemolyticus are also CoNS, commonly confused with staph aureus if performing only traditional coagulase test with plasma
• Historically, staphylococcus was included in the family micrococcaceae, genus micrococcus
• Staph spp. are now combined with bacillaceae, planococcus, and literiaceae into the order of bacillales
• There are approximately 45 species and 21 subspecies within the genus staphylococcus
• Micrococcus are now classified into the genera Kocuria, Nesterekonia, Kytococcus, and Dermacoccus
• Kocuria, Nesterekonia, Kytococcus, and Dermacoccus are recognized into 2 families: Micrococcus and Dermacoccus
• CoNS are divided into two groups: novobiocin-susceptible and novobiocin-resistant
• Novobiocin-susceptible CoNS include:

  • Staph epidermidis
  • Staph capitis
  • Staph haemolyticus
  • Staph hominis
  • Staph lugdunensis
  • Staph saccharolyticus
  • Staph warneri
• Novobiocin-resistant CoNS include:

  • Staph cohnii
  • Staph kloosi
  • Staph saprophyticus
  • Staph xylosus
• Enterotoxins produced by S. aureus can lead to food poisoning when ingested.
• 3 genera of skin-colonizing organisms:

  • Micrococcus
  • Kocuria
  • Kytococcus