StaphylococcusStaphylococcus

Department of pathogenic Biology of Gannan Medical College

Biological Biological characteristicscharacteristics

Gram positive cocci

arranged in irregular

grape – like clusters

Non-sporing and Non-

molite

1. Morphology:

2. Culture2. Culture

Facultative anaerobes

temperature : 28~38 (37 ); pH : ℃ ℃

4.5~9.8 (7.4)

blood agar-----haemolysis

Colony : 1~2 mm, circular,

smooth, shiny surface, opaque,

various pigments

Staph saprophyticus Staph. epidermidi

Staph. aureus

3. Classification:

Table. Major properties of three species of taphylococci

Main property Staph. aureus

Staph. epidermidi

Staph saprophyticus

Pigmentation Golden yellow

White Citrine

Coagulase + - -

Hemolysin + - -

Leukocidins + - -

SPA + - -

Pathogenicity + + + -/ + -

4. Antigenic structure

(1) SPA (staphylococcal protein A)

cell wall protein MW 13,000~42,000 it combines nonspecifically with the Fc-

portion of human IgG antiphagocytosis coagglutination damage platelet activate B cell

SPASPAIgGIgG

Fc receptorFc receptor

PHAGOCYTEPHAGOCYTE

BACTERIUMBACTERIUM

(2) polysaccharide (lipoteichoic acid LTA)

polysaccharide A ------- Staph. Aureus

polysaccharide B ------- Staph. epidermidis

(3) Capsular Polysaccharide

5. Resistance:

resistant to dry; heat (80 ,30min); ℃

salt(10~15%)

sensitivity to: basic-dyes(crystal violet);

antibiotics and sulfonamides (antibiotic

resistance)

Pathogenicity1.pathogenic factor

Surface structure ： SPA ; Peptidoglycan;

CapsuleEnzyme ： Coagulase ； Fibrnolysin; Heat-

stable nuclease; Hyaluronidase; LipaseToxin ； Staphylolysin ； Leukocidin ；

Enterotoxin ； Toxic shock syndrome

toxin-1 (TSST-1) ； Epidermolytic toxin

CoagulaseA enzyme that convers fibrinogen in citrated human or rabbit plasma into fibrin

Extracellular coagulase an extracellular enzyme which activates a coagulase-reacting factor (CRF) normally present in plasma , causing the plasma to clot by theconversion of fibrinogen to fibrin (in tube).

Bound coagulase---------fibrinogen to inhibit the phagocytosis of macrocytes and damage of bacteriacide substances in humor by coating the organisms with fibrin

Staphylolysin

Impairment of membrane permeadility;

cytotoxic effects on phagocytic and tissue cells

Protein

five kinds: ~

Staphylolysin-: main pathogenic

substance

Leukocidin

Kill PMNs and M

Protein

nine types: A-H

Heat stable (boiling for 30 min)

Cause a food poisoning characterized by

severe vomiting and diarrhea

Enterotoxin

Toxic shock syndrome toxin-1 (TSST-1)

Induces multisystsm effects

superantigen effects

Exfoliative toxin

Causes the scalded skin syndrome in

neonates, which results in widespread

blistering and loss of the epidermis.

2.pathogensis local infection

skin infection: hair folliculitis; boil; carbuncle; impetigo

organ infection: pneumonia; meningitis. Systemic infection: Septicemia; pyemia toxin diseases

Food poisoning (enterotoxin) TSS(Toxic shock syndrome) SSSS(staphylococcal scalded skin syndrome)

Staphylococcal enteritis

Laboratory diagnosis specimen: pus ; sputum ; blood ;

food/faeces or vomit (food poisoning) ; mid-stream urine (pyelonephritis or cystisis) direct smear :gram stain isolation and identification: blood agarcoagulose testEnterotoxin test and animal test

Treatment Since strains of Staph. aureus vary in sensitivity to different antibiotics, treatment should be base on the results of sensitivity test made on a culture of the strain isolated from the patient.