Staph. epidermidis
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Transcript Staph. epidermidis
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.