Staph. epidermidis

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Staphylococcus
Department of pathogenic Biology
of Gannan Medical College
Biological characteristics
1. Morphology:

Gram positive cocci

arranged in irregular

grape – like clusters

Non-sporing and Nonmolite
2. 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. aureus
Staph. epidermidi
Staph saprophyticus
3. Classification:
Table. Major properties of three species of taphylococci
Main property
Pigmentation
Coagulase
Hemolysin
Leukocidins
SPA
Pathogenicity
Staph.
aureus
Golden
yellow
+
+
+
+
+++
Staph.
epidermidi
Staph
saprophyticus
White
Citrine
-/ +
-
4. Antigenic structure
(1) SPA (staphylococcal protein A)
 cell wall protein MW 13,000~42,000
 it combines nonspecifically with the Fcportion of human IgG
 antiphagocytosis
 coagglutination
 damage platelet
 activate B cell
PHAGOCYTE
Fc receptor
SPA
IgG
BACTERIUM
(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)
Pathogenicity
1.pathogenic factor
Surface structure:SPA ; Peptidoglycan;
Capsule
Enzyme :Coagulase;Fibrnolysin; Heatstable nuclease; Hyaluronidase; Lipase
Toxin;Staphylolysin;Leukocidin ;
Enterotoxin ;Toxic shock syndrome
toxin-1 (TSST-1) ;Epidermolytic toxin
Coagulase
A 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
Enterotoxin
Protein
nine types: A-H
Heat stable (boiling for 30 min)
Cause a food poisoning characterized by
severe vomiting and diarrhea
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 agar
coagulose test
Enterotoxin 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.
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