Microbiology Notes

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Staphylococcus and Micrococcus

Microbiology Notes Staphylococcus and Micrococcus
  • Gram (+) cocci 
  • Facultatively anaerobes (except for S. saccharolyticus – OBLIGATE ANAEROBE) 
  • In tetrads or in clusters 
  • Catalase (+) 
  • Oxidase (+) 
  • Non-motile 
  • Grows in 7.5 – 10% NaCl

Characteristics

  • COLONY
    • Produced after 18-24 hrs.
    • Medium-sized (4-8 um)
    • COLORS:
      • Cream-colored
      • White
      • Rarely light gold
      • “buttery-looking”

HUMAN NARIS (NOSTRILS) – PRIMARY RESERVOIR FOR STAPHYLOCOCCI

S. aureus Disease Association 

  • Folliculitis 
  • Furuncles (Boil) 
  • Carbuncles 
  • Bullous impetigo 
  • Scalded skin syndrome / Ritter’s Disease / Pemphigus neonatorum 
  • Toxic Shock Syndrome 
  • Toxic Epidermal Necrolysis 
  • Food poisoning 
  • Staphylococcal pneumonia 
  • Osteomyelitis
  • Septic arthritis (children)

S. aureus Virulence Factors:

  • STAPHYLOCOCCAL ENTEROTOXINS
    • Stable @ 100°C
Enterotoxin Disease Association
B (10%), A (78%), D (38%) FOOD POISONING
B, C, G, I, F TOXIC SHOCK SYNDROME
  • Enterotoxin B – assoc. w/ staphylococcal pseudomembranous colitis
  • Enterotoxin F – former name for TSST-1 (assoc. w/ using of tampons)
 Other Virulence Factors

Alpha-hemolysin

1. Lyses: RBCs, platelets, Macrophages
2. Causes: Severe Tissue Damage

Beta-hemolysin (Sphingolmeylinase C)

  • “hot-cold lysin”
  • Enhance hemolysis @ 37°C & 4°C
  • Exhibited in CAMP test
  • Acts on sphingomyelinase of RBC

Staphylococcal enzymes

  • Enzymes:
    • Protease
    • Lipase
    • Hyaluronidase (Duran-Reynal Factor)
    • Staphylocoagulase
  • Facilitates spread of infection (protease, lipase, hyaluronidase)

Panton-Valentine Leukocidin (PVL)

  • Exotoxin lethal to PMNs
  • Assoc. w/ gamma-hemolysin
  • Causes
    • severe cutaneous infection
    • necrotizing pneumonia
  • Assoc. w/
    • community-acquired staph infection

Protein A

  • antiphagocytic
OTHER STAPHYLOCOCCI

S. epidermidis

  • Virulence factor
    • Biofilm
    • Delta toxin
    • Poly-γ-glutamic acid
  • Disease association
    • Prosthetic valve endocarditis (most common)
    • Nosocomial infection.

S. saprophyticus

  • Virulence factor
    • Adheres to epithelial lining
  • Disease association
    • UTI; (>10,000 CFU/ml) – significant

S. lugdunensis

  • Virulence factor
    • mecA gene for oxacillin resistance
  • Disease association
    • UTI 
    • endocarditis
    • Catheter-related bacteremia

S. haemolyticus

  • Virulence factor
    • Vancomycin resistance
  • Disease association
    • UTI 
    • endocarditis
Test to differentiate
Staphylococcus and Micrococcus
TestStaphylococcus Micrococcus
Furoxone-Tween 80-
ORO Agar (growth)		– +
Lysosome (50-mg disk) Resistant Susceptible
Anaerobic acid prod.
From glycerol in
presence of
erythromycin		+ –
O/F Test Fermenter Oxidizer
Modified oxidase – +
Bacitracin (0.04 U) Resistant <10mm Susceptible >10mm
Furazolidone (100 ug) Susceptible Resistant
Lysostaphin (200ug/ml) Susceptible Resistant
Organism PYR VP Test
S. aureus – +
S. lugdunensis + +
S. intermedius + –
S. schleiferi + +

COAGULASE TEST: differentiates S. aureus from CoNS; uses rabbit or pig plasma  

  • Slide method – for clumping factor (cell-bound coagulase) 
  • Tube method – for staphylocoagulase (free coagulase)

Coagulase (+) Staphylococci: 

  • S. delphini 
  • S. aureus 
  • S. hyicus 
  • S. intermedius 
  • S. luteus

Contains CLUMPING FACTOR 

  • S. lugdunensis – confused w/ S. aureus in slide method 
  • S. schleiferi

SMALL COLONY VARIANTS STAPHYLOCOCCI 

  • Fastidious 
  • Requires: CO2, Hemin, Menadione 
  • Grows on media containing blood.
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