staphylococcus aureus, staphylococcus epidermidis, streptococcus pneumoniae and streptococcus...
TRANSCRIPT
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Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae and Streptococcus pyogenes on mannitol salt agar plates (containing 7.5% NaCl, mannitol and phenol red).
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staphylococcal food poisoning
toxic shock syndrome
staphylococcal scalded skin syndrome
exfoliatin enterotoxin
TSST-1
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StreptococciStreptococci
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oral cavity
intestinal tract
female genital tract
anaerobes
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Rebecca Craighill Lancefield (1895 –1981)
She is most famous for her serological classification of beta-hemolytic streptococcal bacteria, which is based on the carbohydrate composition of bacterial antigens found on their cell walls.
Lancefield classification: A serologic classification of hemolytic streptococci, dividing them into groups A to V, 20 groups.
Most human pathogens are from Group A, eg. Streptococcus pyogenes.
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•pyogenic inflammation•scarlet fever•streptococcal toxic shock syndrome•rheumatic heart disease •glomerulonephritis
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M proteinM protein
rrr
peptidoglycanpeptidoglycan
Complement Complement fibrinogenfibrinogen
M protein
It is a component of group A streptococci pili that can inhibits phagocytosis. M protein binds
fibrinogen in plasma which blocks complement to bind to the underlying peptidoglycan layer.
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M protein may have cross antigenecity with
some of human tissue such as endocardium
and glomerular basement membrane.
the bigger problem is…
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type III hypersensitivity (most)
M protein-Ab immune complex
deposition on glomerular basement membrane
activation of complement
tissue destruction
type II hypersensitivity
common Ag
cross reacts with glomerular basement
membrane
tissue destruction
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Acute glomerulonephritis happens !
a disease of kidney caused by the immune
complex during the infection of Group A
streptococci (S. pyogenes). In this disease type
III hypersensitivity and type II hypersensitivity
are involved.
Then…
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Rheumatic fever happens !
An autoimmune disease caused by the
infection of Group A streptococci (S.pyogenes).
It affects primarily the heart (rheumatic heart
disease) and joints (rheumatic arthritis).
Then…
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1. Hemolysins: cytolytic.
2. Hyaluronidase (spreading factor): digest
hyaluronic acid in connective tissue.
3. Streptokinases: lyse fibrin.
4. Streptodornases: degrade DNA.
5. Pyrogenic exotoxins (Erythrogenic Toxins):
encoded by a bacteriophage gene, has
protease activity to cause soft tissue necrosis
or toxic shock syndrome.
What’s more, …
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•pyogenic inflammation•scarlet fever•streptococcal toxic shock syndrome•rheumatic heart disease •glomerulonephritis
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•Local infection: Group A streptococci (S. pyogenes)
causes many inflammatory pyogenic inflammation such as
impetigo ( 脓泡疹 ), pharyngitis ( 咽喉炎 ), tonsillitis ( 扁桃体
炎 ), cellulitis ( 蜂窝织炎 ), and erysipelas (an infection of the
skin in legs characterized by massive edema, 丹 毒 ),
tympanitis ( 中耳炎 ), sinusitis ( 鼻窦炎 ).
•Systemic infection: Group A streptococci (S. pyogenes)
causes pneumonia, osteomyelitis ( 骨 髓 炎 ), arthritis and
meningitis.
Pyogenic infections
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treat early
penicillin G
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Streptococcus Streptococcus
pneumoniaepneumoniae
(the pneumococcus)(the pneumococcus)
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colonize respiratory tract
The diseases it causes:
pneumonia
tympanitis (otitis media)
meningitis
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- +
Streptococcus pneumoniae
produces autolytic enzymes called
as autolysin.
Bile salts such as sodium
deoxycholate can activate
autolysin.
Bile Solubility Test: Add bile-salt
solution into an established broth
culture. Streptococcus
pneumoniae positive culture is
clear with no turbidity.
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Optochin Test: is an assay which is used to identify strains
of S. pneumoniae. Optochin disks are placed on inoculated
blood agar plates. Because S. pneumoniae is not resistant
to optochin, a zone of inhibition will develop around the
disk where the bacteria have been lysed.
- +
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MMost strains of ost strains of S. pneumoniaeS. pneumoniae are sensitive are sensitive
to penicillinto penicillin but but the resistance is frequent. the resistance is frequent.
A vaccine with a mixture of A vaccine with a mixture of capsule from 14 capsule from 14
serotypes serotypes is available.is available.
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NeisseriaNeisseria
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Chocolate blood agar, an enriched, non-selective
medium. Contains red blood cells that have been
lysed by heating very slowly to 56 °C. Lysed red blood
cells provide growth factors, and is the cause for the
brown color.
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Neisseria meningitidis (the meningococcus)
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Colonize upper respiratory tract in human. It can invade bloodstream and finally the brain.
The diseases:meningitisepidemic cerebrospinal meningitis
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Virulence factors Pilus:
adhesion
Capsuleinhibits phagocytosis
Endotoxinthe main pathogenic substance
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Neisseria gonorrhoeae (the gonococcus)
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pyogenic effusionfrom a patient (acute urethritis)
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pyogenic effusion from a newborn’s right eye
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Diseases
Acute urethritis (male) Pelvic inflammation (female) Ophthalmia neonatorum
(infected from the vagina of gonorrhea parturient)
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Virulence factors Pilus
The gonococci with no pili are avirulent
IgA1 proteasedestroy secretary IgA (S-IgA)
EndotoxinOuter membrane protein (OMP)
Porin proteins (PI) suppress phagosome-lysosome fusionOpacity proteins (Opa, PII) help the bacterium bind to the epitheliumReduction-modifiable proteins (Rmp, PIII) inhibit activity of the specific antibody
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Sample collection: the two pathogens are very fragile. They are extremely sensitive to dryness, heat and coldness.
A smear from spinal fluid for cerebrospinal meningitis or pyogenic effusion for gonorrhea may show the presence of Gram-negative diplococci present in polymorphonuclear cells.
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Penicillin therapy: Still used for cerebrospinal meningitis and gonorrhea. Resistant strains of gonococcus producing beta-lactamase are very common.
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For prevention of ophthalmia neonatorum, 0.1 % silver nitrate solution (AgNO3) is dropped into the eyes after the baby is born.
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There are two vaccines of the meningococcus, which are mixture of groups A and C capsule or a mixture of groups A, C, Y and W135 capsule. No gonorrhea vaccine is available.
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Summary
1. Diseases and molecular mechanisms of Streptococci2. Identification of the pneumococcus (diagnosis)
3. Diseases and diagnosis of two species of Neisseria