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
Streptococci
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 protein
Complement
fibrinogen
M protein
r
r
r
peptidoglycan
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.
the bigger problem is…
M protein may have cross antigenecity with some of
human tissue such as endocardium and glomerular
basement membrane.
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
Then…
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).
What’s more, …
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.
•pyogenic inflammation
•scarlet fever
•streptococcal toxic shock syndrome
•rheumatic heart disease
•glomerulonephritis
Pyogenic infections
•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.
treat early
penicillin G
Streptococcus pneumoniae
(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
+
an
Add
solution
into
culture.
Streptococcus
positive
culture
turbidity.
-
Test:
bile-salt
established
is
broth
pneumoniae
clear
with
no
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.
-
+
Most strains of S. pneumoniae are sensitive to
penicillin but the resistance is frequent.
A vaccine with a mixture of capsule from 14
serotypes is available.
Neisseria
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:
meningitis
epidemic cerebrospinal meningitis
Virulence factors
Pilus:
adhesion
Capsule
inhibits phagocytosis
Endotoxin
the main pathogenic substance
Neisseria gonorrhoeae
(the gonococcus)
pyogenic effusion
from 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 protease
destroy secretary IgA (S-IgA)
Endotoxin
Outer membrane protein (OMP)
Porin proteins (PI) suppress phagosome-lysosome fusion
Opacity proteins (Opa, PII) help the bacterium bind to the
epithelium
Reduction-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.