Staph

• What is the Gram status of all cocci except Neisseria, Veillonella, and Branhamella?

  Gram-positive
• Which coccus is motile?

  Planococcus
• Are cocci sporeformers?

  No, they are non-sporeformers
• Which coccus is catalase negative?

  Streptococcus
• What does pyogenic mean in relation to cocci?

  Many are pus-forming
• What are the genera of the family Micrococcaceae?

  • Staphylococcus (primary medical importance)
  • Micrococcus
  • Stomatococcus (rarely isolated)
  • Planococcus
• What are the key differences between Micrococcus and Staphylococcus?

  • Micrococcus:
  • Strict aerobe
  • Modified oxidase positive
  • Bacitracin sensitive
  • Staphylococcus:
  • Facultative anaerobe
  • Modified oxidase negative
  • Bacitracin resistant
• What is the growth characteristic of Staphylococcus?

  Aerobic and facultatively anaerobic
• At what temperature does Staphylococcus grow most rapidly?

  37°C
• What is the significance of catalase in differentiating Staphylococcus from Streptococcus?

  Catalase-positive Staphylococcus separates from Streptococcus
• Where are Staphylococcus species commonly found?

  Soil, water, and human skin
• What is the Gram stain appearance of Micrococcus species?

  Gram-positive cocci in pairs and clusters
• What is the importance of Micrococcus in human health?

  Little importance, some implicated in abscesses
• What is the principle of the modified oxidase test?

  • Detects oxidase enzyme
  • Forms colored compound indophenol
  • Uses tetramethyl-p-phenylenediamine dihydrochloride in DMSO
• What indicates a positive result in the modified oxidase test?

  Blue-purple color
• What does bacitracin inhibit in bacteria?

  Synthesis of bacterial cell walls
• What is the result of bacitracin susceptibility testing for sensitive organisms?

  Zone of inhibition >10mm
• How do Staphylococci and Micrococci respond to furazolidone?

  Staphylococci are susceptible, Micrococci resistant
• What are the species of Staphylococcus?

  • Staphylococcus aureus
  • Coagulase-Negative Staphylococci (CoNS)
  • Staphylococcus epidermidis
  • Staphylococcus saprophyticus
  • Staphylococcus lugdunensis
  • Other CoNS: S. warneri, S. capitis, S. simulans, S. hominis, S. schleiferi, S. haemolyticus, S. pseudintermedius
• What are the pathogenic determinants of Staphylococcus aureus?

  1. Enzymes:

  • Catalase
  • DNAse
  • Lipase
  • Protease
  • Gelatinase
  • Hyaluronidase
  • Staphylokinase
  • Penicillinase
  • Coagulase
  • Staphylocoagulase

  
  

  1. Toxins:

  • Heat stable Enterotoxins
  • TSST-1
  • Exfoliative/Epidemolytic Toxin
  • Cytolytic toxins
  • Leukocidin
• What type of hemolysis does Staphylococcus aureus exhibit on BAP?

  β-hemolytic
• What is the clinical significance of Staphylococcus aureus?

  Causes cutaneous infections and food poisoning
• What are the types of cutaneous infections caused by Staphylococcus aureus?

  • Folliculitis
  • Furuncle/Boil
  • Carbuncle
  • Impetigo
• What is Scalded Skin Syndrome caused by?

  Exfoliative toxins of Staphylococcus aureus
• What is Toxic Shock Syndrome caused by?

  TSST-1 superantigen
• What are the laboratory diagnosis methods for Staphylococcus aureus?

  • Gram Stain
  • Culture on BAP/CAP, MSA
  • Biochemical Tests (Coagulase, Mannitol Fermentation, etc.)
• What is the growth characteristic of Staphylococcus aureus on Mannitol Salt Agar?

  Fermenter
• What does the catalase test detect?

  Presence of catalase enzyme
• What is the significance of the coagulase test?

  Differentiates Staphylococcus aureus from CoNS
• What are the treatment options for cutaneous infections caused by Staphylococcus?

  • Oral cloxacillin
  • Erythromycin (if allergic)
• What are the treatment options for systemic infections caused by Staphylococcus?

  • Nafcillin or oxacillin for resistant strains
  • Vancomycin (if allergic)
• What is the gold standard for detecting MRSA?

  Detection of MecA gene using PCR
• What is the identification process for Staphylococcus species?

  1. Gram Stain
  2. Catalase Test
  3. Coagulase Test
  4. Mannitol Fermentation Test
  5. Novobiocin Sensitivity Test
• What is the primary cause of UTI among young women?

  Staphylococcus saprophyticus
• How does Staphylococcus saprophyticus differ from Staphylococcus epidermidis?

  Novobiocin resistant, coagulase negative