Gram-positive, Non motile,
Non spore forming,
Catalase-negative cocci that occur
in pairs or chains
Classification and Antigenic Types
Streptococci are classified on the basis of “
• A. Colony morphology,
• B. Hemolysis,
• C. Biochemical reactions,
and most definitively by :
D. Serologic specificity.
• They are divided into three groups by the type of
hemolysis on blood agar:
• b-hemolytic (clear, complete lysis of
red cells). Lancfield group
• a hemolytic (incomplete, green hemolysis),
• g hemolytic (no hemolysis).
• Serologic grouping is based on antigenic
differences in cell wall carbohydrates (groups A
to V), in cell wall pili-associated protein, and in
the polysaccharide capsule in group B
LANCEFIELD BETA HEMOLYTIC
• Group A - S. pyogenes
• Group B - S. agalactiae
• Group C - S. equiniss zooepidemicus
• Group D - S. suis
• Group E - S. porcinus
ANTIGENIC TYPES The cell wall structure of
group A streptococci is among the most
studied of any bacteria .
• The cell wall is composed of repeating units
of N-acetylglucosamine and N-
acetylmuramic acid, the standard
Rebecca Lancefield (1895-1981)
in 1922 while working for her PhD thesis.
• Eighteen group-specific antigens were
established on basis C Carbohydrate.
Antibody to M protein gives type-specific
immunity to group A streptococci.
• Antibody to Erythrogenic toxin, prevents the
rash of scarlet fever.
• Immune mechanisms are important in the
pathogenesis of Acute Rheumatic Fever.
• Maternal IgG protects the neonate against
group B streptococci.
• Group A ß-hemolytic streptococci spread by
respiratory secretions and fomites.
• The incidence of both infections peaks in
childhood. Infection can be transmitted by
• Acute rheumatic fever was previously common
among the poor; susceptibility may be partly
• Group B streptococci are common in the normal
vaginal flora and occasionally cause invasive
• Clinical Manifestations
• Disease occur chiefly in the Respiratory tract,
Bloodstream, or as Skin infections.
• Human disease most commonly associated with
Group A streptococci.
• Acute group A streptococcal disease is most
often a respiratory infection (pharyngitis or
tonsillitis) or a skin infection (pyoderma).
• Also medically significant are the late
immunologic sequelae, (rheumatic fever following
respiratory infection and glomerulonephritis
following respiratory or skin infection) which
remain a major worldwide health concern.
Scarlet Fever and Toxic-Shock-Like-Syndrome (TSLS)
• Scarlet Fever: childhood
disease, diffuse rash, fever
• 1800s: Late outbreaks of
highly virulent form, high
• 1900 - 1950: milder form
• 1950: virtually disappeared
(use of penicillin?)
• 1980: appearance of
streptococcal toxic shock-
like disease followed
recognition of Toxic Shock
Syndrome TSS (S. aureus).
TOXIC SHOCK SYNDROME
- begin frequently as skin or wound infection
- developed into septicemia
- death rate sometimes over 30% some disabled, some
- high fatality rate due to rapid development of shock,
multiple organ failure
Etiological agent: Streptococcus pyogenes
• Clinical forms:
–a) Erysipelas. A cutaneous
infection. It results in the
formation of a raised, welt-like,
large spreading lesion, usually
on the face. It is accompanied by
a fever and a stinging sensation.
It occurs in older persons.
• Clinical forms:
A cutaneous infection. It
results in the formation
of a raised, welt-like,
large spreading lesion,
usually on the face. It is
accompanied by a fever
and a stinging
sensation. It occurs in
• b) Puerperal Fever:
- an infection of the uterine muscle tissue
which usually occurs during childbirth
when there is tearing of the tissue.
– (Also called childbed fever). Often, the
organism spreads to the blood from the
uterine muscle tissue, causing a fatal
septicemia. (Puerperal Fever was very
devastating with high fatality rate before
antibiotics, and especially before antiseptic
procedure was accepted)
• c) Streptococcal Pharyngitis:
- An infection of the throat; it is
characterized by a reddened, highly
inflamed, swollen area with a 103oF.
• In itself, S. Sore throat is not life
threatening. The most dangerous aspect
of the disease is the possibility of it
spreading and causing other sequel
clinical forms. That is why S. sore throat is
• d) Glomerulonephritis:
- A disease of the kidneys. It is called a
Type III mediated immune response or an
autoimmune disease because the
organism (Strept. pyogenes from a
previous infection) produced metabolites
which become allergenic. The humoral
immune system produces antibodies
which combine with these allergens to
form an immune complex. These immune
complexes lodge in the glomeruli to cause
inflammation of the kidneys.
– e) Rheumatic Fever:
A sequel disease to Scarlet Fever or from S. sore
throat. It is also a Type III allergic disease or
autoimmune diseases. Antigens during
streptococcal infection, combine with the IgG
antibodies, formed during sensitization.
• The IgG-allergen complex lodges in the joints
and endocardium, including the heart valves.
This is similar to Glomerulonephritis but
different tissues are involved.
• With Rheumatic Fever, the tissue damage,
especially to heart valves, can be very
pronounced; often causes severe irreversible
damage to the heart valves.
It is a very dangerous disease.
f) Scarlet Fever.
• It is characterized by a high fever (103- 104 F)
and by a red rash, usually on the roof of the
mouth and on the skin. Usually arises from
• These skin lesions (not open lesions, but a
rash) tend to feel dry (sand paperish).
• Scarlet fever is not only a severe infection in
itself, it may progress to Rheumatic Fever.
h) Necrotizing Fascilitis (flesh
Involves Gp A, strains M-1 & M-3.
Usually results when injury
occurs, with these strains
present, where the organism
secretes SPE exotoxin
Acts as a "super antigen", which
stimulates T cells to produce
large amounts of cytokines
(MAF), attracting macrophages
and leucocytes into the area,
degranulate and secrete tissue
damaging compounds .
Greatest damage done to blood
vessel endothelium, causing
fluid loss, shock, rapid tissue
necrosis since the cells cannot
get oxygen, and often death.
• Based on cultures from
clinical specimens. Serologic
methods can detect group A
or B antigen; definitive
antigen identification is by the
• Bacitracin sensitivity
group A from other b-
hemolytic streptococci (B, C,
• Group B streptococci typically
show hippurate hydrolysis;
• Group D is differentiated
from other viridans
streptococci by bile
solubility and optochin
• Acute glomerulonephritis
and acute rheumatic
fever are identified by
antibody titers ASO. In
rheumatic fever is
diagnosed by clinical
• Methods of Diagnosis of Group A
– a) Symptoms
– b) The isolation of Streptococcus
species from the infected tissue.
– c) ASO Titer (Anti-Streptolysin O
– d) Strep throat is now most often
diagnosed quickly by a serological
diagnostic test. One of the most
common types is a latex particle
agglutination test, where the latex
particles are coated with specific Ab.
against the prevailing Ag types of
Group A Streptococcus. The swab
from your throat is tested for the
presence of these Ags by swirling in
the tube of latex particles with specific
Ab clumping being positive.
• ASO TITER greater than 1 in
180 Todd units is helpful in
diagnosis of Rheumatic
• GROUP B STREPTOCOCCI
• 25% of all women have this organism as a
vaginal resident. It is an opportunistic
pathogen. It causes postpartum
endometriosis in a small percentage of
women. Also, especially in neonates, a
small percentage develops septicemia and
pneumonia with a 50% to 70% fatality rate in
the first 5 days of life. Meningitis may also
occur in babies born to mothers with Group
B, in 10th to 60th day of life. Often is fatal.
• Prevention is I.V. administration of ampicillin to
expectant mothers who have Group B in vagina.
Strept. agalactiae is positive for CAMP test
named after Christie Anderson Munch Peterson.
• GROUP D STREPTOCOCCI
• Enterococcus faecalis (GI tract/feces).
Often causes UTI's and wound infection
in fecal-contaminated wound and is
particularly resistant to antibiotics.
• Non- Lancefield Streptococci (lack the
C- carbohydrate group-specific