staphylococcus aureus, staphylococcus epidermidis, streptococcus pneumoniae and streptococcus...
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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).
staphylococcal food poisoning
toxic shock syndrome
staphylococcal scalded skin syndrome
exfoliatin enterotoxin
TSST-1
StreptococciStreptococci
oral cavity
intestinal tract
female genital tract
anaerobes
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.
•pyogenic inflammation•scarlet fever•streptococcal toxic shock syndrome•rheumatic heart disease •glomerulonephritis
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.
M protein may have cross antigenecity with
some of human tissue such as endocardium
and glomerular basement membrane.
the bigger problem is…
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
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…
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…
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, …
•pyogenic inflammation•scarlet fever•streptococcal toxic shock syndrome•rheumatic heart disease •glomerulonephritis
•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
treat early
penicillin G
Streptococcus Streptococcus
pneumoniaepneumoniae
(the pneumococcus)(the pneumococcus)
colonize respiratory tract
The diseases it causes:
pneumonia
tympanitis (otitis media)
meningitis
- +
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.
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.
- +
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.
NeisseriaNeisseria
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.
Neisseria meningitidis (the meningococcus)
Colonize upper respiratory tract in human. It can invade bloodstream and finally the brain.
The diseases:meningitisepidemic cerebrospinal meningitis
Virulence factors Pilus:
adhesion
Capsuleinhibits phagocytosis
Endotoxinthe main pathogenic substance
Neisseria gonorrhoeae (the gonococcus)
pyogenic effusionfrom a patient (acute urethritis)
pyogenic effusion from a newborn’s right eye
Diseases
Acute urethritis (male) Pelvic inflammation (female) Ophthalmia neonatorum
(infected from the vagina of gonorrhea parturient)
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
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.
Penicillin therapy: Still used for cerebrospinal meningitis and gonorrhea. Resistant strains of gonococcus producing beta-lactamase are very common.
For prevention of ophthalmia neonatorum, 0.1 % silver nitrate solution (AgNO3) is dropped into the eyes after the baby is born.
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.
Summary
1. Diseases and molecular mechanisms of Streptococci2. Identification of the pneumococcus (diagnosis)
3. Diseases and diagnosis of two species of Neisseria