Staphylococcus Summary

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Morphology and Physiology:

  Nonmotile Gram-positive facultative anaerobic cocci (see WebLinked image; see WebLinked image; see WebLinked image)

  Microscopically cells occur singly and in pairs, short chains, and grape-like clusters

  Both respiratory and fermentative metabolism; Nitrate often reduced to nitrite

  Capsule or slime layer (diffuse capsule) may be present more commonly in vivo; Particularly important in Staphylococcus epidermidis colonization

  Cell wall contains teichoic acid

   Ribitol teichoic acid (Polysaccharide A) in Staphylococcus aureus

   Glycerol teichoic acid (Polysaccharide B) in S. epidermidis


   Strongly catalase positive
   Differentiates staphyloccoci from streptococci

   S. aureus is coagulase positive
    1. Both free and bound coagulase
    2. Bound coagulase = clumping factor
   All other staphyloccocci are coagulase negative

  Usually oxidase negative

  Protein A

   Uniformly coats surface of S. aureus

   Not present on coagulase-negative staphylococci

  S. aureus ferments mannitol; Most other staphyloccocci are mannitol negative  

  Halotolerant (grow in medium containing < 10% NaCl); Salt is useful as a selective constituent in isolation media

  Wide temperature range for growth (18oC - 40oC)

  Staphylococcal strains vary in pigmentation and susceptibility to antibiotics

Clinical Syndromes:

S. aureus:

  Cutaneous Infections:


  Furuncles (boils)


  Bullous impetigo
  Pustular impetigo

   Wound infections

  Toxin-Mediated Infections:

  Scalded skin syndrome: neonates and children under the age of four

  Toxic-shock syndrome

  Food poisoning

  Other infections:


  Bacteremia (hospital-acquired)


  Osteomyelitis: disease of growing bone

  Septic arthritis

  Septic embolization

  Metastatic infections

S. epidermidis and other coagulase-negative staphylococci:

  Endocarditis: infections of either native or artificial heart valves

  Catheter and shunt infections

  Prosthetic joint infections

  Other opportunistic infections

Staphylococcus saprophyticus:

  Urinary tract infections in sexually active young women




  Staphylococci are common flora: skin, nasal cavity, oropharynx, gastrointestinal tract, genitourinary tract

  Transient colonization by S. aureus

  Transmission by direct contact or by fomite

  Carrier state: short or long-term, often colonizing the anterior nares

  Endemic and epidemic disease

  Nosocomial infections


Extracellular virulence factors:



    1. bound (clumping factor)
    2. free (coagulase-reacting factor)

  Hyaluronidase: "spreading factor" of S. aureus

  Nucleases: S. aureus; Cleaves DNA (DNase) and RNA (RNase)

  Fibrinolysin: staphylokinase

  Lipases: esterases



  Cytotoxins (hemolysins): cytopathic and cytolytic for a broad range of affected cells, including erythrocytes, leukocytes, macrophages, hepatocytes, lymphocytes, lymphoblasts, fibroblasts, neutrophils and platelets
 Alpha toxin
  Beta toxin: sphingomyelinase C (phospholipase)
  Delta toxin: detergent-like activity
  Gamma toxin: hemolytic activity

  Enterotoxins (A to E)

  Exfoliative toxin (epidermolytic toxin or exfoliatin) (A and B)

  Toxic shock syndrome toxin-1 (TSST-1) (formerly pyrogenic exotoxin C)

Somatic virulence factors:

  Slime layer (capsule)

  Protein A: binds Fc receptors of IgG

  Teichoic acid: binds fibronectin

Laboratory Identification:

  Microscopy: gram reaction and morphology

  Culture and biochemical confirmation


Treatment and Prevention:

  Drain infected area

  Deep/metastatic infections: semi-synthetic penicillins; cephalosporins, erythromycin or clindamycin

  Endocarditis: semi-synthetic penicillin plus an aminoglycoside

  Carrier status prevents complete control

Proper hygiene, segregation of carriers from highly susceptible individuals

  Good aseptic techniques when handling surgical instruments

  Control of nosocomial infections


   Go to Pathogen List



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Revised: August 2000