Call Girls Service Pune Vaishnavi 9907093804 Short 1500 Night 6000 Best call ...
The Streptococci.pptx
1.
2. The Streptococci
Gram positive cocci which typically form pairs /
chains (divide only in one plane)
Some species cause important diseases
Many are part of the normal flora
3. Classification
A heterogeneous group which no single system
suffices to classify.
Classification is based on multiple criteria ->
1. Their Oxygen requirement
2. Hemolytic pattern on Sheep blood agar
3. Antigenic characteristics
4. Biochemical properties
8. 2. Beta hemolytic Streptococci
Lancefield Grouping
Based on group specific “C” carbohydrate antigen
Lancefield Groups -> A – H & K – V
Group A Streptococcus
Serotyping,
Based on specific “M” Protein (80 types)
Griffith’s typing
Griffith’s types
9. S.PYOGENES
Morphology:
GPC in chains.( divides in only one plane)
Non motile,non sporing
Opt temp : 37 0 C
Some strains of Gp A & C posses hyaluronic acid
capsules.Gp B & D : poly saccharide capsules
10. Culture:
BA : small ,circular , semi transparent convex colonies,
with beta haemolysis
5 – 10 % CO2 promotes growth & haemolysis
Liquid media : granular turbidity
11. Biochemical Rxns:
Ferments several sugars with acid only.
Catalase : negative
Not soluble in 10 % bile.
PYR test : positive
Ribose fermentation : negative
12. Resistance :
Delicate organism ,destroyed at 54 0 C for 30 minutes.
Storage of cocci is at 4 0 C in RCM.
13. Group A Streptococcus
(Streptococcus pyogenes)
Pathophysiology ->
Bacterial virulence factors:-
Virulence factors of Streptococcus pyogenes
may be divided into two categories –
Cellular virulence factors
Extracellular virulence factors
14. Cellular virulence factors
1. Capsule ->
Most strains are capsulated
Capsule made up of Hyaluronic acid
Potent antiphagocytic factor
Helps in adherence to host tissue
15. Cellular virulence factors
2. ‘M’ Protein ->
Major virulence factor
Strains without M protein are avirulent
Present on surface as hair like projections (pilli)
Approx. 80 serotypes exist
Acts as ‘adherence factor’
Potent ‘antiphagocytic action’
Highly antigenic, specific Abs are protective
Abs to M protein cross react with cardiac tissue
16. T protein : acid labile ,trypsin resistant .
May be specific but many diff M types posses same T
protein.
Demonstration : slide agglutination test using trypsin
treated whole streptococci.
17. R protein : some types of S.pyogenes (2 , 3, 28, 48)&
some strains of B,C & G
No relation to virulence
MAP : non type specific M associated protein.
18. 3. Group specific cell wall ‘C’ carbohydrate Ag
->
Component of the cell wall
Forms basis of serologic grouping by Lancefield
Lancefield groups – (A – H and K – V)
Antigenic specificity lies in the amino sugar
present
Grouping may be done by ‘Co-agglutination’
tests
19. Ag is the integral part of cellwall.
Strep grown in Todd Hewitt broth & extracted with
HCl ( Lancefield’s acid extraction )
formamide ( Fuller’s method)
An enzyme produced by S.albus ( Maxted’s
method)
Autoclaving(Rantz& Randall’s method)
20. The extract & specific antisera allow to react in a
capillary tube .
Precipitation occurs in minutes at the interface.
Gel electrophoresis also used for grouping
21. Cross reacting Antigens
Various streptococcal Ags have similarity to different
host tissues ->
Capsular hyaluronic acid <–> human synovial fluid
Cell wall M protein <–> myocardium
Cytoplasmic membrane antigen <–> vascular intima
These antigenic cross reactions may be responsible
for the non-suppurative complications of group A
Streptococcal infections.
22. Extracellular Virulence Factors
A. Toxins ->
1. Pyrogenic exotoxins (erythrogenic toxins) A, B,
C ->
Toxins produced by only strains which carry a
lysogenic phage
Pyrogenic – induce fever
Responsible for skin rashes in scarlet fever
Superantigens, responsible for streptococcal SSS
Highly antigenic, Abs are protective
Have ability to alter lymphocytic activity
24. Streptolysin ‘O’
‘O’ -> means oxygen labile, hemolytic activity
observed only under anaerobic conditions
MW -> 60,000 Daltons
Active against both RBC & WBC
Antigenic -> Abs raised are called
Antistreptolysin O Abs (ASO)
Estimation of this antibody (ASO) titre helps in
the diagnosis of streptococcal disease
25. Streptolysin ‘S’
Produced in presence of serum
It is oxygen stable
Active against RBC, WBC, Platelets
Responsible for the Beta hemolysis seen around
the colonies on the surface of blood agar
Has nephrotoxic activity
26. B. Enzymes of Str.pyogenes
1. Streptokinase ->
Transforms plaminogen in plasma to plasmin
which can digest fibrin clots
Helps in Streptococcal infections by breaking
down the fibrin barrier around the lesions and
facilitating the spread of infection
Practical use – given IV for treatment of
pulmonary emboli; coronary artery/venous
thromboses
27. 2. Streptodornase (Streptococcal DNAse) ->
De-polymerises DNA & nucleoprotein released by dead
host cells
Responsible for the decrease in viscosity of purulent pus
Responsible for the serous nature of exudate in
streptococcal infection
Help in spread of lesion
Mixture of streptokinase/streptodornase is used in
enzymatic debridement of necrotized tissues & empyemas
– facilitates early recovery of infected tissue
28. 3. Hyaluronidase ->
Degrades hyaluronic acid , which is the ground
substance of subcutaneous tissue. Also known as
‘Spreading factor’ – it facilitates the rapid spread of
Str. pyogenes in skin infection
Other organisms ->
Staphylococcus aureus
Clostridium perfringens
29. Streptococcus pyogenes infections
Pathogenesis ->
1. Source:-
a) Patients with skin lesions; respiratory
secretions of sore throat cases
b) Carriers
2. Mode of infection:-
Direct/Indirect contact or inhalation
30. A. Diseases attributable to local infection
1. Streptococcal sore throat ->
Most common infection of small children
a sub acute nasopharyngitis with thin serous
discharge,
little fever
tendency to spread to middle ear (otitis); the
mastoid (mastoiditis) & meninges (meningitis)
32. Complications seen with sore throat ->
1. Peritonsillar abscesses (Quinsy)
2. Ludwig’s angina (massive swelling of floor of
mouth, blocking air passage)
3. Scarlet fever, if infecting strain produces
erythrogenic toxin
4. Rarely, pneumonia, usually secondary to
viral infections
33. 2. Streptococcal pyoderma
Local infection of superficial layers of skin –
impetigo
Highly communicable disease of children
Characterized by superficial blisters which
breakdown to form eroded areas covered with
pus/crusts
34. Streptococcal pyoderma contd….
Extensive infection may occur in burn cases /
wounded skin and may progress to –> cellulitis
M types -> 49, 57, 59 – 61 (Nephritogenic strains)
Most often precede Glomerulonephritis
35. B. Diseases attributable to invasion
1. Erysipelas ->
Rapidly spreading infection of the superficial
lymphatics
Characterized by massive edema with induration
and red discoloration & a rapidly advancing
margin
36. 2. Cellulitis ->
Rapidly spreading infection of skin &
subcutaneous tissues
Usually follows infection of mild trauma,
burns, wounds
Characterized by pain, tenderness,
swelling, erythema
37. 3. Necrotizing fasciitis (Streptococcal gangrene) ->(
m types 1 & 3 forming pyrogenic exotoxin A)
Infection of subcutaneous tissue & fascia
Extensive & rapidly spreading necrosis of skin
/subcutaneous tissues
Strains causing this condition – “ flesh eating
bacteria”
38.
39. 4. Puerperal fever ->
Infection of uterus just after delivery
A septicemia originating in the uterus
(endometritis)
5. Sepsis ->
Infection of traumatic / surgical wounds
Has also been called ‘surgical scarlet fever’
40. 6. Streptococcal toxic shock syndrome ->
Invasive infection may also be accompanied by
– streptococcal TSS
caused by M types 1, 3, 12, 28
Characterized by –>
• Shock,
• Bacteremia
• Respiratory & multi-organ failure
41. 7. Scarlet fever ->
May follow severe throat / skin infection
Rashes appearing on trunk within 24 hrs of
illness, spreading to extremities
Streptococcal TSS & scarlet fever are overlapping
diseases
42. 8. Infective endocarditis ->
Following sepsis
Streptococci settle on healthy / previously
deformed heart valves
Cause rapid destruction of heart valves
Resulting in acute bacterial endocarditis
Fatal cardiac failure within days / weeks
43. D. Post-streptococcal diseases
(Non-suppurative complications of Group A
Streptococcal infection)
Complications occur 1 – 4 weeks after an episode of
acute infection
Latent period suggests an hypersensitive / auto-
immune basis for development of complication
Streptococci or its toxins cannot be detected from
affected tissues
Acute Glomerulonephritis
Rheumatic Fever
44. 1. Acute Glomerulonephritis
Develops about 3 weeks after a skin infection
Caused by nephritogenic strains (M types -> 49, 55,
59 – 61)
Probable mechanism involved ->
1. Deposition of Ag-Ab complexes on glomerular
basement membrane
2. Initiation of Complement mediated damage to
basement membrane (Type III Hypersensitivity)
3. Resulting in glomerulonephritis
45. Acute Glomerulonephritis contd….
Condition is characterized by ->
Blood & protein in urine (hematuria
/proteinuria)
High blood pressure
Edema of neck & ankles
Low serum complement levels
Self limiting and prognosis is good
46. 2. Acute Rheumatic fever
Occurs 1-4 weeks following Group A Streptococcal
pharyngitis (any strain)
Probable mechanism involved ->
1. Abs formed against cell wall Ags of Streptococcus
pyogenes cross-react with cardiac tissue (due to
antigenic similarity between streptococcal cell wall
Ag & cardiac tissue)
2. Cause damage to all parts of the heart (endo, myo
& pericardium) – Type II - cytotoxic
Hypersensitivity / auto-immune disorder
47. Acute Rheumatic fever contd ….
Condition is characterized by ->
Fever
Malaise
Poly-arthritis
Inflammation of cardiac tissue - including
connective tissue degeneration of the heart
valves and inflammatory myocardial lesions
48. Acute Rheumatic fever contd ….
Condition has marked tendency for
reactivation due to recurrent Group A
streptococcal infection
Damage increases with each subsequent attack
Requires long term prophylactic Penicillin
administration for protection against repeated
attacks
Has variable prognosis
49. Comparison of Acute Rheumatic Fever and Acute
Glomerulonephritis
Features ARF AGN
1o site of infection Throat Skin or throat
Prior sensitization Essential Not required
Serotypes
responsible
Any Nephritogenic M types
49, 55, 59 – 61
Immune response Marked Moderate
Complement level Unaffected Lowered
Repeated attack Common Absent
Course Progressive or
static
Spontaneous
resolution
Prognosis Variable Good
Penicillin
prophylaxis
Essential Not indicated
50.
51. Lab diagnosis
1. Specimen -> collection depends on type
of disease
Throat swab,
pus,
exudates, fluids
necrotic tissue –> for culture
Serum -> for serology
52. Methods:-
2. Microscopy ->
Gram’s stained smear:-
Gram positive cocci in long chains along with
pus cells
(May not be useful in case of throat swabs)
Immunofluorescent staining:-
Direct immunofluorescent staining using
specific monoclonal Abs – highly sensitive &
specific
53. 3. Culture ->
Specimen should be immediately processed
Transport media – Pike’s / Stuart’s media used
if delay in processing
Routine media used – Sheep Blood agar;
Thioglycollate medium
Incubated for 24 – 48 hrs at 37o C in 5 -10% CO2
54. Culture contd….
Identification of Isolate ->
Beta hemolytic colonies
Gram positive cocci in chains
Catalase test negative
Isolate is susceptible to bacitracin
Grouping (Lancefield) is done by Co-
agglutination test to detect ‘Group A Streptococci’
55. 4. Serology ->
Rise in titre of Abs to many Group A
Streptococcal Ags may be demonstrated.
1. Antistreptolysin O (ASO) test:-
A serological test used to detect ASO Abs
present in patient’s serum
A passive latex agglutination test
ASO titre of more than 200 units is indicative
of recent streptococcal infection
56. May also indicate an exaggerated immune
response to an earlier exposure (ARF)
Useful in the diagnosis of ARF but not in AGN
as titre is low (usually occurs as a result of skin
infection and being oxygen labile toxin, Ab will
not be produced in high titre)
57. Other serological tests ->
2. Antistreptodornase (AntiDNAse) test
3. Antihyaluronidase test
4. Antistreptokinase test
58. Treatment
Group A Streptococci are susceptible to
penicillin. Thus Penicillin G is the drug of choice
In patients allergic to penicillin, erythromycin /
cephalexin may be used
All acute infections should be treated, as
antimicrobials have no effect on already
established ARF & AGN
Long term Penicillin therapy for ARF patients to
prevent recurrence of infection
59.
60. Streptococcus agalactiae
It is part of the normal flora of the female genital
tract (5 – 20% of women)
Human pathogenecity ->
1. Neonatal infections
2. Infections in adults
61. 1. Neonatal infections ->
A. Early onset disease->
Seen at birth or within 7 days of birth
Source of infection -> mothers birth canal
Predisposing factors ->
Prolonged labor
Premature child
Low birth weight
Manifestations –> Septicemia, meningitis,
pneumonia
62. B. Late onset disease ->
Occurs after first week of life
Source -> hospital staff, environment
Manifestation ->
o Sepsis with /without meningitis
o Respiratory tract infection
63. B. Adult infections ->
1. In women ->
Abortion
Chorioamnionitis
Post partum sepsis
2. In debilitated individuals ->
Septicemia
Meningitis
Endocarditis
64. Lab diagnosis ->
1. Specimen -> CSF, Blood, Exudates
2. Cultured onto -> Sheep Blood Agar
3. Incubated at -> 37o C for up to 48 hrs
4. Isolate identified by ->
a) Beta hemolysis on blood agar
b) Gram stained smear – Gram positive cocci in
chains
c) Ability to hydrolyze Hippurate
d) CAMP test positive
65. Christie Atkins Munch Petersen Test
(CAMP Test)
Definition ->Test used to identify Group B
Streptococci
Principle ->Enhancement of β hemolysis of S.aureus
by a soluble protein (CAMP factor) produced by
Strep. agalactiae
Observation -> Arrow head
hemolysis is seen in-between
the two streaks of growth
68. Classification
This group is divided into two groups ->
1. Enterococci ->
o Have Group ‘D’ specific Ag
o Differ from streptococci in biochemical
characteristics:-
Ability to survive in 40% bile
Grow in medium with 6.5% NaCl
Bile-Esculin hydrolysis test – Positive
Heat resistant (tolerate heat of 60oC for 30 min)
69. o May be non-hemolytic or alpha hemolytic
o Important species include:-
Enterococcus faecalis
Enterococcus faecium
Enterococcus durans
o Part of the normal flora of the gut
o Pathogenicity -> - Urinary tract infection
- Wound infection
- Intra-abdominal abscess
- Sub-acute bacterial endocarditis
70. 2. Nonenterococci (Group D Streptococci) ->
o Also contain Group ‘D’ Ag
o Important species:-
Streptococcus bovis
Streptococcus equinus
o May be non-hemolytic or alpha hemolytic
o Streptococcus bovis -> has been isolated from
blood (septicemia) in patients with colon
carcinoma
71. Lab diagnosis
Specimens –> Urine, pus, blood
Microscopy -> Gram stain:
Gram positive oval cocci arranged
in pairs at an angle to each other
Culture –>
Blood agar - non-hemolytic / α hemolytic
MacConkey’s agar - magenta pink
coloured colonies
72. Growth on Bile Esculin agar – Positive
Treatment
Multi-drug resistance is common with
enterococci
Enterococci are intrinsically resistant to
Cephalosporins and Aminoglycosides
Vancomycin is drug of choice
73.
74. The Viridans Streptococci
A heterogeneous group of streptococci which
cannot be grouped under Lancefield's
classification
Part of the normal flora of the oral cavity and
upper respiratory tract
Mostly alpha hemolytic (greenish color
‘viridans’)
Important species ->
Streptococcus mitis
Streptococcus mutans
Streptococcus sanguis
Streptococcus salivarius
75. Characteristics of viridans group ->
1. Difficulty in grouping
2. Alpha hemolytic
3. Insoluble in bile
4. Resistant to ‘Optochin’
5. Not pathogenic to mice on intraperitoneal
inoculation
6. Antibiotic susceptibility -> susceptible to
penicillin
76. Human pathogenicity
1. Dental caries ->
Str. mutans produces large amounts of slime which
adheres to teeth to form ‘plaques’
Bacteria within plaques ferment dietary starch into
acids which damage dentine resulting in caries
2. Sub-acute bacterial endocarditis ->
After dental extraction/manipulations, bacteria
enter blood stream, settle on damaged heart valves,
form vegetation and cause sub-acute endocarditis
77.
78. Streptococcus pneumoniae
o The pneumococci are capsulated, gram positive,
lanceolate shaped diplococci which are an
important cause of sinusitis, otitis,
bronchitis, pneumonia,
bacteremia & meningitis
o They are part of the normal flora of the upper
respiratory tract in approximately 5 – 40% of
humans
80. Quellung (capsular swelling) reaction
Mixing of capsulated pneumococci present in
sputum/suspension with type specific or polyvalent
antisera (Abs) on a glass slide results in apparent
swelling of capsules around the pneumococci
Observed under light microscope
Swelling is due to Ag-Ab reaction
and a change in the refractive index
of the capsular material
Use – in direct demonstration, identification & in
typing
81. 2. Lipoteichoic acid – activates complement
and induces inflammatory cytokine
production
3. Pneumolysin – a hemolysin causes α
hemolysis & contributes to pathogenesis
4. Ig A1 Protease – enhances ability of the
organism to colonize the mucosa of URT by
destroying secretory IgA present on the
respiratory epithelia
82. Pathogenesis ->
1. Source of infection:-
Exogenous – Patients / carriers -> shed
organisms in their respiratory secretions
(40 – 70% of a population harbor pneumococci
at some time during their lifetime)
Endogenous – Part of the normal flora of URT
2. Mode of infection – Inhalation of droplet
nuclei or by direct / indirect contact
83. 3. Host predisposing factors ->
Infection & carriage is common but disease
occurs only under certain predisposing
conditions
A. Abnormalities of the Respiratory tract ->
a) Viral infections damaging surface cells
b) Abnormal accumulation of mucus – allergy
c) Bronchial obstruction – atelectasis
d) Respiratory tract injury due to irritants
disturbing its muco-ciliary function
84. Predisposing factors contd….
B. Alcohol / Drug intoxication -> results in,
i. Decreased phagocytic activity
ii. Decreased cough reflex, &
iii. Facilitates aspiration
C. Abnormal circulatory dynamics ->
i. Pulmonary congestion
ii. Heart failure
85. Predisposing factors contd….
D. Other factors ->
i. Malnutrition
ii. General debility
iii. Old age
iv. Sickle cell anemia
v. Hyposplenism
vi. Nephrosis
vii. Complement deficiency
viii.convulsions
86. 4. Sequence of events ->
a. Colonization of the upper respiratory tract
b. Whenever patient is predisposed, spread of
infection to the lower respiratory tract
c. Pneumococci produce disease through their
ability to multiply in tissues
d. Multiplication in the lungs results in
outpouring of edema fluid, WBC, RBC into
the alveoli, resulting in consolidation of
portions of the lungs
87. e. Later, mononuclear cells actively phagocytose the
bacteria and cell debris and digest them
intracellularly
f. Recovery begins between 5 – 10 days, with the
development of type specific Abs.
5. Clinical findings & complications ->
Lobar Pneumonia - Sudden onset of fever, chills &
sharp pleural pain, with expectoration of bloody or
rusty colored sputum
Mortality rate in pneumonia is high (30%) if cases
are untreated
88. Clinical findings & complications contd….
Contiguous spread may result in middle ear
infection (otitis); the mastoid (mastoiditis); the
paranasal sinuses (sinusitis)
Pus in pleural space (empyema) may require
aspiration / drainage
In 10 – 20% of patients, bacteremia occurs with
metastatic involvement of meninges (meningitis);
joints (septic arthritis) and rarely, the
endocardium (acute endocarditis)
89. Lab diagnosis
1. Specimen ->
Sputum,
Blood,
CSF,
Pus from suppurative lesions,
Synovial fluid,
Laryngeal swab (in the place of sputum in
children)
90. Lab diagnosis contd ….
2. Microscopy ->
a. Gram’s stained smear :-
Pneumococci are seen as Gram positive lancet or
flame shaped cocci in pairs along with pus cells
91. Lab diagnosis contd ….
b. Capsule demonstration:-
i. By negative staining – India Ink or Nigrosin –
capsule may be demonstrated as clear halo
ii. Quellung reaction (Capsule swelling reaction)
92. 3. Culture ->
Media used - Blood agar; Chocolate agar
Specimens are inoculated onto media and
incubated at 37o C under 5-10% CO2
Colony characteristics ->
Alpha hemolytic colonies dome shaped initially
which on further incubation acquires ‘Draughtsman’
appearance
This is due to the production of autolysins by the
streptococci which cause lysis of the older cells in
the centre
93.
94. 4. Identification of isolate ->
a) alpha hemolytic colonies
b) Gram positive Lancet shaped cocci in pairs
c) Capsule demonstration
d) Bile solubility test –> positive
e) Optochin sensitivity test –> sensitive
f) Animal pathogenicity test –> Virulent to
mouse
95. 5. Serology ->
Rapid diagnostic method ->
Detection of capsular polysaccharide Ag in blood,
CSF by ->
Latex agglutination ,
Co-agglutination
ELISA
6. Antibiotic susceptibility testing ->
Should be done to determine susceptibility pattern
96. Differences between
Str. pneumoniae & Viridans Streptococci
Property Pneumococci Viridans
Streptococci
Morphology Lanceolate,
diplococci
Spherical / oval
cocci In long
chains
Capsule Present Absent / Slime
Colony Draughtsman Dome
Bile solubility Soluble Insoluble
Optochin
sensitivity
Sensitive Resistant
Animal
pathogenicity
(mouse)
Virulent Avirulent
97. Treatment
Penicillin – drug of choice
Tetracycline/ Erythromycin – also effective
Penicillin resistant strains – 3rd generation
Cephalosporin are used
98. Prevention
Immunity against Pneumococci is type specific
and associated with Antibody to capsular
polysaccharide
A polyvalent polysaccharide vaccine containing
prevalent 23 serotypes is available and
administered by single dose injection
Not for general use
Only in persons at enhanced risk of
pneumococcal infection – children and elderly
99.
100. C Reactive Protein (CRP)
Acute phase protein (Beta globulin) produced by
the liver and is found in serum
Precipitates with somatic ‘C’ antigen of
Pneumococci Therefore known as ‘C Reactive
Protein’
Not an Antibody produced as a result of
Pneumococcal infection
Its production is stimulated by bacterial
infections, inflammations, malignancies and
101. It disappears when the inflammatory reactions
subside
CRP can be detected by passive latex
agglutination and it is a routine diagnostic
procedure
CRP is used as an index of response to treatment
in Rheumatic fever and certain other conditions