Genus Streptococcus

Genus Streptococcus
Dr Ravi Kant Agrawal, MVSc, PhD
Senior Scientist (Veterinary Microbiology)
Food Microbiology Laboratory
Division of Livestock Products Technology
ICAR-Indian Veterinary Research Institute
Izatnagar 243122 (UP) India

Morphology
 Streptococcus is a genus of Gram-positive cocci or
spherical bacteria, that belongs to the
family Streptococcaceae, within the order Lactobacillales
(lactic acid bacteria), in the phylum Firmicutes.
 Gram positive spherical or oval cocci arranged in chains
or pairs.
 Chain formation is due to the cocci dividing in one plane
only and the daughter cells failing to separate
completely
 The name streptococci was given in 1877 by Viennese
surgeon Albert Theodor Billroth (1829–1894).
 Streptos: easily twisted or coiled; coccus: berry)
 Individual coccus is 0.5-1.0 μm in diameter.
 They are non-motile and non-spore forming.
 Nutritionally fastidious
 Streptococci are catalase negative
 Facultative anaerobes but don’t use oxygen
metabolically (create lactic acid)
 Longest chain is produced by Streptococcus salivarius
(Commensal)
 Chains are longer in liquid than in solid media
 Some strains have capsule composed of hyaluronic acid
(non-immunogenic).

Habitat
Normal flora of upper
respiratory tract in animals
and human – Commensals and
Saprophytes of decaying
matter
Some of them may be
pathogens e.g. Streptococcus
pyogenes causing pyogenic
infections with a tendency to
spread unlike staphylococcal
infections
It produces non-suppurative
lesions, acute rheumatic fever
and glomerulonephritis which
occur as sequelae to infection

Classification
 Initial classification based on hemolysis on
sheep blood agar plates: α (partial, reduction), β
(complete), and γ (none).
 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 peptidoglycan.
 Rebecca Lancefield (1895-1981) : in 1922 while
working for her PhD thesis, Eighteen group-
specific antigens were established on basis C
Carbohydrate.
 1930’s: Lancefield defines cell wall antigen
groups
 Concentrated on virulent, β-hemolytic species
 Sherman: pyogenic, viridans, enterococci, lactic
 1980’s: Enterococci get own genus
 Lactic acid Streptococci (Lancefield N): New
genus Lactococcus
 Nutritionally variant Streptococci (require
pyridoxal): Abiotrophia and Granulicatella
Rebecca Craighill
Lancefield (1895-1981)

Classification of Streptococci
• Brown`s classification
• Lancefield grouping
• Griffith typing
Brown`s classification Lancefield grouping
V

Hemolysis
Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae
Example – enterococcus group

CLASSIFICATION:
StreptococciAerobes & facultative
anaerobes
Obligate anaerobes
Eg: PeptostreptococciBeta haemolytic
Gamma haemolytic
Eg: Enterococcus group
Alpha haemolytic
Eg: Viridans streptococci
20 Lancefield groups
(ABCDEFGHKLMNOPQRSTUV)80 Griffith types
(1,2,3,etc. up to 80)
02 requirement
Haemolysis
Serological Grouping (C carbohydrate antigen)
Group A- Streptococcus pyogens
Serological typing (M Protein)

Serology: Lancefield Classification
• Streptococci classified into many groups from A-K & H-V
• One or more species per group
• Classification based on C- carbohydrate antigen of cell wall
– Groupable streptococci
• A, B and D (more frequent)
• C, G and F (Less frequent)
– Non-groupable streptococci
• S. pneumoniae (pneumonia)
• viridans streptococci
– e.g. S. mutans
– Causing dental carries
Streptococci
Group A
S. pyogenes
Group B
S. agalactiae
Group C
S. equisimitis
Group D
Enterococcus
Lanciefield classification
Other groups
(E-U)

Group A Streptococci (GAS)
S. pyogenes: Cultural characteristics
• Aerobes and facultative anaerobes
• Optimum temperature: 37C
• Needs enrichment with blood or serum - Growth
occurs only in media containing fermentable
carbohydrates or enriched with blood or serum
i. Blood agar:
Small (0.5-1.0 mm), circular, semi-transparent
colonies
Produce wide zone of β- hemolysis
Growth and hemolysis are promoted by 5-10% CO2
Virulent strains, on fresh isolation form lesions,
produce a ‘matt’ (finely granular) colony while
avirulent strains form ‘glossy’ colonies
Mucoid colonies are formed by strains that produce
large capsules
ii. Liquid media:
Glucose or serum broth
Growth occurs as a granular turbidity with a
powdery deposit
No pellicle is formed

CULTURE:
Media used:
1. Non selective media:- Sheep blood agar
2. Selective media:- Crystal violet blood agar
PNF medium
(Horse blood agar containing polymyxin B
sulphate, neomycin sulphate, and fusidic
acid inhibited the growth of Staph. aureus, Ps.
pyocyanea, Proteus mirabilis, E. coli, and
Klebsiella pneumoniae but allowed good
growth of, and haemolysis by, Str. pyogenes)

Biochemical reactions
 Catalase negative
 Bile insoluble
 Ferments sugars producing acid but no gas,
faliure to ferment ribose
 PYR test positive: Hydrolyse pyrrolidonyl-beta-
napthylamide (PYR) due to presence of peptidase,
the resulting napthylamide produces a red colour
upon the addition of 0.01% cinnamaldehyde
reagent
Bile insoluble
Positive Negative PYR test Catalase

Resistance
 S. pyogenes is a delicate organism,
easily destroyed by heat (54C for 30 min)
 Sensitive to bacitracin
 Has developed less resistance to drugs
 Dies in a few days in culture, unless stored at a
low temperature (4C) preferably in
Robertson’s cooked meat medium
 Rapidly inactivated by antiseptics and many
antibiotics
Fig. Zone of inhibition
shown by S. pyogenes

Antigenic structure
Capsular hyaluronic acid:
• Non antigenic as hyaluronic acid is identical to that found in
human connective tissue and hence bacteria can disguise
themselves with an immunological self substance
• Has weak anti-phagocytic activity but protects streptococci
against immunological attacks

Antigenic structure
A. Cell wall:
1. Outer layer: Protein and
lipoteichoic acid
2. Middle layer: Group specific
carbohydrate
3. Inner layer: Peptidoglycan
(mucoprotein)
Responsible for cell wall
rigidity
Enhances non-specific
resistance (pyrogenic and
thrombolytic activity)
B. Group specific C-carbohydrates
Serological grouping of
streptococci is done on its
basis
Divided into 20 Lancefield
groups (A to V) except I and J
on the basis of group specific
carbohydrates.
All streptococci except viridans
(α-hemolytic) group have a
layer of carbohydrate

C. Proteins
Present in outermost
layer
Produces surface
protein antigens (F, M, T
and R)
Useful in serological
typing of S. pyogenes
M protein: Most virulent;
heat and acid stable, but
susceptible to tryptic
digestion. 80 types
identified. Griffith
typing.
T protein: Not virulent,
acid labile, trypsin
resistant.
R protein: Not virulent
Antigenic structure

Antigenic structure
F-protein
 Recognizes host fibronectin, a matrix protein that is present in
eukaryotic cells. Hence helps in attachment together with
lipoteichoic acid and M protein
M protein
 Most antigenic
 Covered with lipoteichoic acid that enable the organism to attach to
epithelial cell
 M protein is heat and acid stable but susceptible to tryptic digestion
 On the basis of antigenic difference in M protein, S. pyogenes can be
divided into about 100 types
 The most distal part of M protein shows extensive variability among
strains hence individual may suffer from recurrent S. pyogenes
infections with strains expressing different versions of M protein.
 Acts as a virulence factor by inhibiting phagocytosis
T-Protein
• Common to many M- types
• Not associated with virulence and is not a protective antigen
• It is strongly antigenic
R protein
• Non-type-specific and is associated with M- proteins of types 2,3 28
and 48 known as M-associated protein (MAP)
• Not associated to virulence and not a protective antigen
• Strongly antigenic

Antigenic Structure
D. Pili (Fimbriae)
Hair like and project from capsule
Consist partly of M-protein
Covered with lipoteichoic acid
Important in the attachment of streptococci to epithelial cells

Virulence Factors: Toxins and enzymes
Toxins
1. Hemolysins
(Streptolysin O and S)
2. Erythrogenic toxin
(Pyrogenic Exotoxin)
Enzymes:
1. Streptokinase
(Fibrinolysin)
2. Deoxyribonucleases
(Streptodornase,
DNAase)
3. Hyaluronidase
4.NADase
5.Serum opacity factor

Cytolytic toxins and other exo-enzymes produced by
Streptococcus pyogenes

Hemolysins (Streptolysins)
 Produce complete disruption of RBC
Contribute to tissue invasion and destruction
There are two types of Streptolysins
Streptolysin O: sensitive to oxygensensitive to oxygen
Streptolysin S: insensitive to oxygeninsensitive to oxygen

Erythrogenic toxin
• Also known as pyrogenic exotoxin/ Dick/
Scarlatinal toxin
• Primary effect of the toxin is production
of fever hence also called Streptococcal
pyrogenic exotoxin (SPE)
• Known as erythrogenic because its
intradermal injection into susceptible
individuals produced an erythematous
reaction (Dick test)
• DICK TEST- Used to identify
susceptibility to scarlet fever
• Three types of SPE (A,B,C)
• Mediate production of rash e.g. (scarlet
fever)
• SUPERANTIGENS hence massive release
of cytokines occur that leads to variety
of clinical signs including inflammation,
shock and organ failure
Fig. Rash in scarlet fever

Streptokinase (Fibrinolysin)
Two types of streptokinase (A and B)
Antigenic protein
Fibrinolysin facilitates spread of infection by breaking down the
fibrin barrier around the lesions also known as spreading factor
Promotes the lysis of human blood clot by converting
plasminogen to plasmin
It is given intravenously for the treatment of early myocardial
infarction and other thromboembolic disorders

Deoxyribonucleases (Streptodornase, DNAase)
• Degrades DNA
• Four antigenically distinct DNAases: A,B,C,D; B most antigenic
• Capable of liquefying DNA accumulated in thick pus derived
from nuclei of necrotic cells, hence the exudate is thin in
streptococcal infections
• Important therapeutically in liquefying localised collections of
thick exudates (Empyema)
• Demonstration of anti-DNAase B antibody in the diagnosis of S.
pyogenes infections when ASO titres is low

Hyaluronidase
• Breaks down hyaluronic acid of connective tissue and favors
spread of infection
• Antigenic and specific antibodies are formed
• Degrades capsule
• Others are proteinase, phosphatase, amylase, esterases,
NADase, C5a peptidase, lipase, Serum opacity factor (SOP) etc.

Pathogenicity
Produces pyrogenic
infection with a tendency
to spread locally, along
lymphatics and through
blood stream
Disease caused can be:
1. Suppurative diseases:
a. Respiratory infections
b.Skin and soft tissue
infections
c. Genital infections
2. Non suppurative sequelae:
a. Acute rheumatic fever
b.Acute glomerulonephritis

Structural components of S. pyogenes that cross react
with human tissues
Structural components of
S. pyogenes
Human tissue with which it
cross reacts
Capsular hyaluronic acid Synovial fluid
Cell wall protein Myocardium
Cell wall carbohydrtes Cardiac valves
Cytoplasmic membrane antigens Vascular intima
Peptidoglycans Skin antigens

Streptococcal Diseases
Suppurative Complications
1. Respiratory infections
Primary site of invasion is throat causing SORE THROAT
May be localized as tonsillitis or pharyngitis
Lipoteichoic acid covering surface pili binds to the glycoprotein
fibronectin on epithelial cells of pharynx
From the throat, spreads to surrounding tissues leading to suppurative
complications like
Otitis media
Mastoiditis
Quinsy
Suppurative adenitis
Meningitis (rare)
(it is an inflammation of the mucosal lining of the mastoid antrum and mastoid air cell system
inside[1]
the mastoid process. The mastoid process is the portion of the temporal bone of the skull
that is behind the ear which contains open, air-containing spaces.
(Peritonsillar abscess (PTA), also known as a quinsy, is pus due to an infection behind the
tonsil).
Adenitis is a general term for an inflammation of a gland
tonsillitis pharyngitispharyngitis

2. Skin and soft tissue infection
• S. pyogenes causes
subcutaneous infections
ranging cellutitis to
necrotising fascilitis
• Include infections of
wounds or burns, with a
predilection to produce
lymphangitis and cellulitis
• Infection of minor
abrasions may lead to
fatal septicemia
• S. pyogenes is also known
as ‘FLESH EATING
BACTERIA’ - extensive
necrosis of subcutaneous
and muscular tissue and
adjacent fascia – causes
Toxic shock like
syndrome
Quinsy
Mastoiditis
Pharyngitis
Otitis media

a) Impetigo (Pyoderma)
 Pyo-purulent and derma-skin
 Caused by higher numbered M
types S. pyrogen
 Superficial discrete crushed
spot of less than one inch in
diameter seen in children
 Lasts for 1-2 weeks and heals
spontaneously without any
scars
b) Erysipelas
 Erythros: red and pella: skin
 Hypersensitivity reaction to
Streptococcal antigen
 Causes acute spreading lesions
involving superficial lymphatics
 Affected skin is red, swollen,
indurated and sharply
demarcated from surrounding
healthy skin
 Rare and seen only in older
patients
Erysipelas
Impetigo

c) Cellulitis and
Necrotising fascilitis
Involves deeper
subcutaneous tissues
Local inflammation and
systemic
signs like erysipelas are
observed
Necrotising faciitis :
• M types 1 and 3 forming
pyrogenic exotoxin A
• High fatality
• Flesh eating bacteria
• Shock, DIC
• Treatment with
penicillin – not effective
• Vancomycin – DOC in life
threatening infections
Effect of flesh eating
bacteria 
Cellulitis
Necrotising fascitis

3. Genital infection
• Both aerobic and anaerobic Streptococci are normal habitat of
female genitalia
• Causes puerperal sepsis with exogenous infection
• Puerperal fever is caused due to endogenous infection with
anaerobic Streptococci
 Other suppurative infections: Abscesses in brain, lungs, kidney
and liver causing septicemia and pyemia

Non suppurative complications
• After a latent period of 1-4 weeks
• Followed by rheumatic fever and acute glomerulonephritis

a) Rheumatic fever
• Complication of S. pyogenes pharyngitis due to specific M
protein types
• Characterized by aschoff nodules (sub cutaneous nodule)
• Causes inflammatory myocardial lesion of connective tissue
degeneration of heart valves
• Results in chronic and progressive damage to heart valves,
arthralgias to frank arthritis
• Mimics epidemiologic character of streptococcal pharyngitis
Aschoff bodies are nodules found in the hearts of individuals with
rheumatic fever. They result from inflammation in the heart
muscle and are characteristic of rheumatic heart disease.

b) Glomerulonephritis
Caused by specific nephritogenic strains of group A
streptococcus
Characterized by acute inflammation of renal glomeruli with
edema, hypertension, hematuria and proteinuria
In contrast with rheumatic fever it is sequela of both pharyngeal
and pyodermal streptococcal infection differing in nephrogenic
M serotypes
Mimics epidemiologic character of streptococcal infection
Progressive, irreversible loss of renal function in young is
common

Epidemiology
 Group A Streptococci causes transient asymptomatic colonization of
oropharynx and skin
 Regulated by ability to mount specific immunity to M protein of
colonizing strain and presence of competitive organism in oropharynx
 Pharyngitis is primarily disease of children (5-15 yrs.), infants and
adults are also susceptible
 Pathogen spreads from respiratory droplets and direct contact
especially in winter season
 Soft tissue infections are proceeded by initial skin colonization to
superficial or deep tissue through a break in the skin
 Re-infection occur due to multiplicity of M protein serotypes

A) In acute suppurative infectionA) In acute suppurative infection
Specimens to be collected:
• Throat swab,
• Pus, Pus swab
• Tissue material,
• Blood,
• Swab from nose for detection of carriers.
Transport media: Pike’s medium
2. Direct Microscopy:
Gram-staining of pus can be examined
Presence of Gram-positive cocci in chains can be indication.
Direct microscopy with Gram stained smear is useful in case of
pus & CSF, where cocci in chains are seen.
This is of no value for specimen like sputum & genital swabs
where mixed flora are normally present.
LABORATORY DIAGNOSIS

Laboratory Diagnosis
a. Throat swab culture: Detection of group A antigen
b.Specific nucleic acid based test
c. Elevation of anti-hyaluronidase antibodies (strong evidence)
Culture:
Swab from the affected area is collected and are either plated
immediately or sent to laboratory in Pike’s medium.
The specimen should be plated on blood agar and incubated at
37˚C anaerobically or under 5-10% CO2, as hemolysis develops
better.

Bacitracin sensitivity
Bacitracin sensitivity:
Based on Maxted’s observation that they are
more sensitive to bacitracin than other
streptococci
A filter paper disc of 0.04U is applied on the
surface of an inoculated blood agar
After incubation, a wide zone of inhibition is seen
with S. pyrogenes but not with other streptococci
Principle:
– Bacitracin test is used for presumptive
identification of group A
– To distinguish between S. pyogenes (susceptible to
B) & non group A such as S. agalactiae (Resistant to
B)
– Bacitracin will inhibit the growth of group A Strep.
pyogenes giving zone of inhibition around the disk
Procedure:
– Inoculate BAP with heavy suspension of tested
organism
– Bacitracin disk (0.04 U) is applied to inoculated BAP
– After incubation, any zone of inhibition around the
disk is considered as susceptible

4. Identification:
Rapid diagnostic test kits are
available for the detection of
streptococcal group A antigen
from throat swab
f) Lancefield serogrouping: Based
on ‘C’ carbohydrate antigen
g) Serotyping: serotyping of S.
pyogens is required only for
epidemiological purposes.
III) Antigen detection:
ELISA & Agglutination tests are
used for detection of S.
pyogenes antigen from throat
swabs

• Serological tests are useful
• The tests are –
1. Anti Streptolysin O (ASO) test
2. Anti Deoxyribonuclease B (anti-DNAase B) test
3. Anti Hyaluronidase test
4. Streptozyme test
B) In Non-suppurative complicationsB) In Non-suppurative complications

5. Serology:
Antistreptolysin O titration
Standard test ASO titres higher than 200
are indicative of prior streptococcal
infection.
High levels are usually found in acute
rheumatic fever but in
glomerulonephritis, times are often low.
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 fever.

5. Serology:
Antideoxyribonuclease B (anti-DNAase
B)
Commonly used
Titres higher than 300 are taken
Streptozyme test:
A passive slide hemagglutination test
using erthyrocytes sensitised with a
crude preparation of streptococci
It is a convenient, sensitive and
specific screening test.

Treatment, prevention and control
DRUGS USED:
• For streptococcal pharyngitis: Oral penicillin V or amoxicillin
• Oral cephalosporin or macrolides can be used for penicillin
sensitive patients
• For severe, systemic infection: Combined use of intravenous
penicillin with protein synthesis inhibiting antibiotics
(clindamycin) is recommended
• Streptococcal pyogenes have developed resistance over
tetracyclines and sulfonamides, newer macrolides
• Antimicrobial drugs has no effect on glomerulonephritis and
rheumatic fever

Prophylaxis
• Rheumatic fever requires long term antibiotic prophylaxis to
prevent recurrence of disease
• Penicillin is used in patients who have developed early signs of
rheumatic fever
• For acute glomerulonephritis no need of antibiotic therapy and
prophylactic therapy (no re-infection)
• For patients with serious soft tissue infection, drainage and
aggressive surgical debridement must be initiated

Group B beta hemolytic Streptococci
Streptococcus agalactiae
• Infect newborns - Neonatal infection
• Source – Infection acquired through maternal vagina during
birth
• Group B Streptococci (GBS) – puerperal sepsis, pneumonia
• Presents as meningitis, pneumonia or septicemia
• Most common cause of neonatal meningitis
• Diagnostic markers – Hippurate hydrolysis, CAMP test

CAMP test
• Christie, Atkins and Munch-Peterson
• When S. agalactiae is inoculated perpendicular to a streak of S.
aureus grown on blood agar  an accentuated zone of
hemolysis occurs

CAMP test
Principle:
Group B streptococci produce extracellular protein (CAMP
factor)
CAMP act synergistically with Staphylococcus aureus β-lysin to
cause lysis of RBCs
Procedure:
Single streak of Streptococcus to be tested and a Staph. aureus
are made perpendicular to each other
3-5 mm distance was left between two streaks
After incubation, a positive result appear as an arrowhead
shaped zone of complete hemolysis
S. agalactiae is CAMP test positive while non group B
streptococci are negative

CAMP TEST
S. aureus
(Spingomyelinase C)
Group B
Streptococcus
(CAMP Factor)
Group A
Streptococcus
Enhanced
Zone of
Hemolysis

Hippurate Test
Hippurase NEG
Streptococcus agalactiae not added
Hippurase POS
Grp B Streptococci added

Streptococcal Mastitis
 S. agalactiae (B), S, dysgalactiae (C) and S. uberis are main causes.
 S. pyogenes (A) and S. zooepidemicus (C) are less commonly isolated.
 S. agalactiae colonizes in milk ducts and produces persistent infection
with intermittent bouts of acute mastitis.
 S. dysgalactiae found in buccal cavity and genitalia and on the skin of
the mammary gland causes acute mastitis.
 S. uberis a normal inhabitant of skin, tonsils and vaginal mucosa is a
major cause of clinical mastitis, usually without systemic signs.
Hemolysis CAMP test Aesculin
hydrolysis
(Edwards
Medium)
Growth on
MacConkey
agar
Lancefield
Group
S. agalactiae β (α, γ) + - - B
S. dysgalactiae α - - - C
S. uberis α - + - Not
assigned
E. faecalis α - + + D

Group C beta hemolytic Streptococci
Streptococcus equi
• S. equi ssp equi causes Stangles in Horses.
• Highly contagious disease of horses.
• Febrile disease (>1010
C) involving the upper
respiratory tract with abscessation of regional
lymph nodes.
• Horses of all ages are susceptible however, most
common in young horses.
• Assembling horses at sales, shows and races
increases risk of infection.
• Transmission is via purulent exudates from the
upper respiratory tract or from discharging
abscesses.
• A chronic convalescent carrier state can develop
with bacteria present in the guttural pouch.
• An atypical mild form where S. equi are present
in small purulent foci has been described.
• Infected animals may shed S. equi for at least 04
weeks after development of clinical signs.

Strangles
• Incubation Period: 3-6 days
• There is high fever, depression and anorexia
followed by an occulo-nasal discharge that
becomes purulent.
• The lymph nodes of head and neck are
swollen and painful.
• Characteristically sub-mandibular lymph
nodes are affected and they eventually
rupture discharging purulent highly infectious
pus.
• Guttural pouch empyema is a common finding
• Morbidity up to 100% and mortality less than
5%
• Death occurs due to complications like
pneumonia, neurological involvement,
asphyxia due to pressure on pharynx from
enlarges lymph nodes or purpura
hemorrhagica (caused by bleeding
from capillaries which results in red spots on
the skin and mucous membranes together
with oedema (swelling) of the limbs and the
head).
• Bastard Strangles: in which abscessation
develops in many organs, is a serious
complication in about 1% of affected animals.

Diagnosis
Clinical signs and history of recent exposure to suspected
animals
Colonies are mucoid, up to 4.0 mm in diameter, surrounded by a
wide zone of beta-hemolysis
S. equisimillis and S. zooepidemicus, which causes mild upper
respiratory tract infections, must be differentiated from S. equi
by sugar fermentation tests in peptone water containing serum.
Trehalose Sorbitol Lactose Maltose
S. equi - - - +
S. equisimilis + - V +
S. zooepidemicus - + + +(-)

Treatment
Treatment
Penicillin to in-contact and infected horses is recommended
Antibiotics are of limited use when abscesses have developed.
Control:
Clinically suspected animals should be isolated.
Horses should be isolated for 10 days when first introduced or
returning to herd
Predisposing factors liking overcrowding and mixing of different
age groups should be avoided.
After outbreak, building and equipment should be disinfected.
Prophylaxis:
Inactivated vaccine is available in some countries

Group C beta hemolytic Streptococci
Streptococci equisimilis
• Upper respiratory infections
• Endocarditis, osteomyelitis, brain abscess
• Treat with penicillin and gentamicin
• Penicillin tolerance
• Source of streptokinase used for thrombolytic therapy in
patients

Classified into 2 groups:
1. Non enterococcal group: containing S. suis, S. bovis and S.
equinus.
2.The enterococcus group: which have been reclassified as a
separate genus called Enterococcus, containing- E. faecalis, E.
faecium and E. durans.
Group D Streptococci:

 S. suis is recognized as cause of significant losses in pig industry.
 Causes meningitis, arthritis, septicemia and bronchopneumonia in pigs of
all ages with sporadic cases of endocarditis, neonatal deaths and abortion.
 Belong to Lancefield group D.
 Symptomatic carrier pigs harbour S. suis in tonsillar tissue.
 Disease outbreaks most common in intensively reared pigs due to
overcrowding, poor ventilation and other stress factors.
 Sows carrying organisms may infect their litters leading to neonatal deaths
or carrier state animals
 Respiratory disease may occur in conjunction with Mycoplasma and
Pasteurella spp.
 S. suis may infect cattle, small ruminants, horses and cats.
 Infections occurs in human directly involved in pig husbandry or processing.
Control:
 These bacteria tend to become endemic in herd and eradication not
feasible.
 Improved husbandry practices
 Prophylactic Penicillins may be given to sows 01 week prior to farrowing
and to piglets during first 02 weeks of life- in herds experiencing neonatal
deaths and meningitis at weaning
S. suis

Formerly Streptococcus - GROUP D STREPTOCOCCI
Enterococcus faecalis
Enterococcus faecium
Enterococcus durans
Most commonMost common species in faecalisspecies in faecalis
Group D carbohydrate cell wall antigen
Present in intestine, genital tract and saliva - Normal inhabitant
Normal gut floraNormal gut flora
Enterococcus

Special features
• Grow in the presence of 40% bile
• 6.5% sodium chloride
• Resist pH of 9.6
• Growth at 45 deg C
• Heat resistant – survives 60 deg C for
30 minutes
• They grow in 0.1% methylene blue milk.
• Tiny magenta coloured colonies in Mac
Conkey agar
• Enterococci typically appear as pairs of
oval Gram positive cocci.
• The cells in a pair arranged at an angle
to each other.
• Non hemolytic

Source & mode of infection:
1. Endogenous: from colonized site.
2. Exogenous: through direct or indirect contact.
Common infections:
1. Urinary tract infection
2. Wound infection
3. Bacteremia
4. Intra-abdominal abscesses
5. Biliary tract infection
6. Sub acute bacterial endocarditis
Clinical significance

Laboratory diagnosis
Specimens collected: Urine, blood, pus &
exudates.
Methods of examination:
1. Direct microscopy- by doing Gram’s smear.
2. Culture- Blood agar and MacConkey’s agar is
used.
Identification:
• Gram’s stain
• Catalase Negative
• Mannitol, sucrose, sorbitol fermentation
• Bile Esculin hydrolysis
• Non-hemolytic on blood agar
• Intrinsically resistant to cephalosporins
Treatment:
• Strains resistant to penicillin & other
antibiotics occur frequently.
• Penicillin + Aminoglycosides
• Vancomycin is the alternative drug to
penicillin: Vancomycin resistant is also seen-
VRE - terminal D-ala replaced by D-lactateterminal D-ala replaced by D-lactate

Viridans group
• Streptococci normally resident in the mouth and upper
respiratory tract
• Alpha hemolysis on blood agar
• Cannot be categorized under Lancefield antigenic groups
Types:
1. S. mitis
2. S. mutans
3. S. salivarius
4.S. sanguis
• Causes dental caries
• Tooth extraction – seeding into blood stream - endocarditis –
hence give prophylactic antibiotics

(pneumococcus)
Morphology:
• Lancet shaped (one end broad,
other pointed)
• Capsulated
• Diplococci
S. pneumoniae: lancet-shaped diplococcus

Growth characteristics
• Alpha hemolysis on blood
agar
• On further incubation, the
colonies become flat with
raised edges and central
elevation resembling
carrom coins
Example –
Streptococcus viridans (Viridans = green)

Biochemical reactions
• Hiss serum water – fermentation of inulin
• Bile solubility

Resistance
• Pneumococcus is
sensitive to optochin –
used for typing
• Resistance to penicillin
• May be resistant to third
gen ceph also – third
generation cephalosporin
like ceftriaxone

Pathogenicity and virulence
• Capsule
• Toxins – pneumolysin
• C reactive protein

Pneumolysin
• Membrane damaging toxin
• Cytotoxic activity

C reactive protein
• Abnormal immunoglobulin against C protein of S. pneumoniae
appears in serum of patients
• Also seen in acute phase of infections and inflammations
• CRP titre is tested in acute infections

Epidemiology
• Source – respiratory tract of humans
• Spread – droplets
• Carriers – pharynx
• Low immunity is responsible for fulminant infections
– RSV infection, pulmonary congestion, stress, malnutrition,
alcoholism
– Splenectomy
– Sickle cell disease

76
Diseases caused
• Middle ear – otitis media
• Para nasal sinuses – sinusitis
• Respiratory tract – pneumonia, bronchitis, empyema
• Meningitis is secondary to otitis media, penumonia, sinusitis and
conjunctivitis

Laboratory diagnosis
Sample
Pneumonia - Sputum
Septicemia - blood culture
Otitis media - fluid from middle ear
Meningitis - CSF
Method
– Gram stain, microscopy
– Culture
Latex agglutination for pneumococcal antigen in serum of patients

Differentiation between α-hemolytic streptococci
• The following definitive tests used to differentiate
between S. pneumoniae & viridans streptococci
Optochin Test
Bile Solubility Test
Inulin Fermentation

Optochin Susceptibility Test
Principle:
– Optochin (OP) test is presumptive
test that is used to identify S.
pneumoniae
– S. pneumoniae is inhibited by
Optochin reagent (<5 µg/ml) giving
a inhibition zone ≥14 mm in
diameter.
Procedure:
– BAP inoculated with organism to
be tested
– OP disk is placed on the center of
inoculated BAP
– After incubation at 37oC for 18 hrs,
accurately measure the diameter of
the inhibition zone by the ruler
– ≥14 mm zone of inhibition around
the disk is considered as positive
and ≤13 mm is considered negative
• S. pneumoniae is positive (S) while
S. viridans is negative (R)
Optochin
susceptible
S. pneumoniae
Optochin
resistant
S. viridans

Bile Solubility test
Principle:
– S. pneumoniae produce a self-
lysing enzyme to inhibit the
growth
– The presence of bile salt
accelerate this process
Procedure:
– Add ten parts (10 ml) of the
broth culture of the organism
to be tested to one part (1 ml)
of 2% Na deoxycholate (bile)
into the test tube
– Negative control is made by
adding saline instead of bile to
the culture
– Incubate at 37oC for 15 min
– Record the result after 15 min
Results:
– Positive test appears as
clearing in the presence of
bile while negative test
appears as turbid
– S. pneumoniae soluble in bile
whereas S. viridans insoluble

Differentiation between β-hemolytic streptococci
Hemolysis Bacitracin
sensitivity
CAMP test
S. pyogenes β Susceptible Negative
S. agalactiae β Resistant Positive
Hemolysis Optochin
sensitivit
y
Bile
solubility
Inulin
Fermentation
S. pneumoniae α Sensitive
(≥ 14 mm)
Soluble Not ferment
Viridans strep α Resistant
(≤13 mm)
Insoluble Ferment
Differentiation between α-hemolytic streptococci

Outline of differentiation between Gram-Positive cocci
e.g. S. epidermidis

Treatment
• Penicillin
• Amoxycillin
• ceftriaxone/ceftazidime
• Vancomycin

Prophylaxis
• Pneumococcal conjugate vaccine is available
• Given to splenectomy patients, sickle cell anemia patients and
susceptible individuals

Classification of Streptococci from Humans
Species Lancefield Hemolytic Comments
S. pyogenes A β Scarlet Fever, Septic Sore
throat, Rheumatic fever,
Glomerulonephritis
S. agalactiae B β (α, γ) Chronic Mastitis
S. dysgalactiae C α (β, γ) Acute mastitis
S. equisimilis C α (β, γ) Abscesses, Endometritis,
Mastitis
S. equi C β Strangles, suppurative
conditions, purpura
haemorrhagica
S. equi subsp
zooepidemicus
C β Bovine mastitis
S. suis D α, β septicaemia; meningitis,
arthritis, bronchopneumonia &
infrequent human meningitis

Zoonotic Streptococcus Species
Species Lancefield Hemol
ysis
Comments
S. bovis species
group
D α, γ Viridans; associated with colon
cancer; IE
S. mutans group not useful α, γ,
rarely β
Viridans; dental caries and IE
S. salivarius
group
not useful α, γ Viridans; opportunistic
S. mitis group not useful α Viridans; IE, opportunistic
S. anginosus
group
A, C, F, G, or
no
detectable
α, β, γ Viridans; formerly known as S.
milleri; 3 species S. anginosus, S.
constellatus, and S. intermedius;
purulent infections
S. canis G β Dogs; infrequent human pathogen
S. iniae None
detectable
β Fish; SSTI, sepsis

Group F beta hemolytic Streptococci
Streptococcus MG
• Grow poorly on blood agar
• Minute streptococci
• Streptococcus MG – alphalytic strain – isolated from Primary
atypical pneumonia

Minute colony streptococciMinute colony streptococci
Various groups/ hemolysis (e.g. group A)Various groups/ hemolysis (e.g. group A)
– genetically distinct from large colony (e.g. S. pyogenes)genetically distinct from large colony (e.g. S. pyogenes)
– no rheumatic feverno rheumatic fever
Large colonyLarge colony Minute colonyMinute colony

Thanks
Acknowledgement: All the material/presentations available online on the subject
are duly acknowledged.
Disclaimer: The author bear no responsibility with regard to the source and
authenticity of the content.
Questions???

Thanks
Acknowledgement: All the presentations available online on the
subject are duly acknowledged.
Disclaimer: The author bear no responsibility with regard to the
source and authenticity of the content.

Genus Streptococcus

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