Pharyngitis (or sore throat) - most common upper respiratory tract infections (URTI). Viral pharyngitis - vast majority of cases – self-limited. Bacteria - important etiologic agents of pharyngitis, require specific antibiotic treatment - can lead to serious complications and sequelae Streptococcus pyogenes Corynebacterium diphtheriae Rare causes Other β-hemolytic streptococci (group C and G) Arcanobacterium hemolyticum Fusobacterium necrophorum Mycoplasma pneumoniae Neisseria gonorrhoeae Size – 0.5-1 m. Shape – oval /elliptical. Arrangement – in chains esp. in liquid culture media. (upto 50 cocci in a chain). Divide in one plane. Daughter cells do not seperate. Gram positive Cultures older than log phase may lose gram reaction. Capsule – Hyaluronic acid (group A, C). Nonimmunogenic. Polysaccharide (group B, D ). Nonmotile. Nonsporing. L-forms – cell-wall deficient, require thiol & pyridoxal for growth. Found in blood (due to antibiotics). Aerobes & facultative anaerobes. 22-42°C; opt.37. pH for growth –opt. 7.4. Capnophilic – 10% CO2. Fastidious; need blood / serum / sugar. Liquid medium (e.g. Todd-Hewitt broth) – granular turbidity + powdery deposits. Blood agar – 0.5-1mm, circular, low convex, -hemolytic. Matt colonies – pathogenic Glossy colonies – nonpathogenic. Selective medium – Crystal violet (1:500,000) in B.A. Catalase – ve Sugar fermentation – Glucose, lactose, maltose, trehalose - . (constitutive enzymes). Other sugars & alcohols - ,(inducible enz.). *Ribose sugars – not fermented. *Pyrolidonyl naphthalamide hydrolysis (PYR) - +ve (differentiates gr. A from other groups). Delicate organism Survives in dust in dark for many weeks. Susceptible to heat , 54°C x 30 min. Susceptible to common antiseptics. Resistant to – Crystal violet (1mg/litre) – for isolation of gr A. Nalidixic acid (15mg/litre) for isolation of & Colistin (10mg/litre) gr. B Bacitracin sensitive – differentiates gr. A from other hemolytic Hyaluronic acid capsule-nonantigenic, antiphagocytic, thrombolytic. Innermost cell wall layer peptidoglycan (NAG-NAM) Cell-wall CHO – Group sp. Ag. Todd-Hewit growth → Extraction by – HCl (Lancefield) Formamide (Fuller) Enzyme of Streptomyces albus (Maxted) Autoclave (Rantz & Randall). Capillary pptn /ring pptn M protein – Acid extraction & Serotyping. 100 M-types. T protein – Typing by slide agglutination with trypsinised RBCs. R protein – Present in gr. B, C, G & some serotypes of gr. A (23, 28, 48). . Antigenic cross-reactions Capsular hyaluronic acid  synovial fluid. Cellwall CHO  cardiac valves. Cellwall peptidoglycan  skin. Cyto. membrane  vascular intima & cardiac muscle. M protein* - reqd. for invasive infection. Receptor for fibrinogen, factor H, IgG. Capsule - antiphagocytic Group CHO Ag’-invasive properties. Protein F- binds fibronectin on epi. Surface Lipoteichoic acid loosely binds strepto’ to epi surface. F prtn, M prtn secur

1. Introduction
▰ Pharyngitis (or sore throat) - most common upper
respiratory tract infections (URTI).
▰ Viral pharyngitis - vast majority of cases – self-limited.
▰ Bacteria - important etiologic agents of pharyngitis, require
specific antibiotic treatment - can lead to serious
complications and sequelae

2. Bacterial Pharyngitis
DR MAYURI BHISE

3. Etiological agents
 Streptococcus pyogenes
 Corynebacterium diphtheriae
▰ Rare causes
 Other β-hemolytic streptococci (group C and
G)
 Arcanobacterium hemolyticum
 Fusobacterium necrophorum
 Mycoplasma pneumoniae
 Neisseria gonorrhoeae.

4. S T R E P T O
C O C C U S

5. History
 Billroth, 1874
 Ogston, 1881
 Rosenbach – 1884.
5

6. CLASSIFICATION

7. O2 requirement
Aerobes & facultative
anaerobes
Anaerobes
Hemolysis on 5% horse B.A.
- hemolytic
(viridans)
- hemolytic
(pathogens)
- or non-hemolytic
(fecal streptococci)
Serogrouping by Rebecca Lancefield (1933) -
based on cell wall cabohydrate, A-W (except I & J)
Group A – Strepto. pyogenes
Serotyping based on M, T, R proteins. >100 Griffith types
7

8. Streptococcus pyogenes
8

9. Morphology
 Size – 0.5-1 m.
 Shape – oval /elliptical.
 Arrangement – in chains esp. in liquid culture media.
(upto 50 cocci in a chain).
 Divide in one plane.
 Daughter cells do not seperate.
 Gram positive
 Cultures older than log phase may lose gram reaction.
9

11. Capsule –
• Hyaluronic acid
(group A, C).
Nonimmunogenic.
• Polysaccharide
(group B, D ).
Nonmotile.
Nonsporing.
L-forms – cell-wall deficient, require thiol &
pyridoxal for growth. Found in blood (due to
antibiotics).
11

12. Cultural characters
 Aerobes & facultative anaerobes.
 22-42°C; opt.37.
 pH for growth –opt. 7.4.
 Capnophilic – 10% CO2.
 Fastidious; need blood / serum / sugar.
 Liquid medium (e.g. Todd-Hewitt broth) – granular
turbidity + powdery deposits.
12

13. Blood agar –
• 0.5-1mm, circular, low
convex, -hemolytic.
• Matt colonies –
pathogenic
•Glossy colonies – nonpathogenic.
Selective medium –
•Crystal violet (1:500,000) in B.A.
13

14. Biochemical reactions
 Catalase – ve
 Sugar fermentation –
 Glucose, lactose, maltose, trehalose - . (constitutive
enzymes).
 Other sugars & alcohols - ,(inducible enz.).
 *Ribose sugars – not fermented.
 *Pyrolidonyl naphthalamide hydrolysis (PYR) - +ve
(differentiates gr. A from other groups).
14

15. Resistance / viability
 Delicate organism
 Survives in dust in dark for many
weeks.
 Susceptible to heat , 54°C x 30 min.
 Susceptible to common antiseptics.
 Resistant to –
 Crystal violet (1mg/litre) – for isolation of gr A.
 Nalidixic acid (15mg/litre) for isolation of & Colistin
(10mg/litre) gr. B
 Bacitracin sensitive – differentiates gr. A
from other hemolytic streptococci. 15

16. Antigenic structure
Hyaluronic acid capsule-
nonantigenic,
antiphagocytic,
thrombolytic.
•Innermost cell wall layer
peptidoglycan
(NAG-NAM).
•Middle layer of cellwall carbohydrate.
•Outer layer of proteins, lipoteichoic acid.
16

17.  Cell-wall CHO – Group sp. Ag. Todd-Hewit growth →
 Extraction by –
 HCl (Lancefield)
 Formamide (Fuller)
 Enzyme of Streptomyces albus (Maxted)
 Autoclave (Rantz & Randall).
 Capillary pptn /ring pptn
17

18.  M protein –
 Acid extraction & Serotyping.
 100 M-types.
 T protein –
 Typing by slide agglutination with trypsinised RBCs.
 R protein –
 Present in gr. B, C, G & some serotypes of gr. A (23, 28, 48).
18

19.  Antigenic cross-reactions
 Capsular hyaluronic acid  synovial fluid.
 Cellwall CHO  cardiac valves.
 Cellwall peptidoglycan  skin.
 Cyto. membrane  vascular intima & cardiac muscle.
19

20. Virulence factors
A) cellular
 M protein* - reqd. for invasive infection.
 Receptor for fibrinogen, factor H, IgG.
 Capsule - antiphagocytic
 Group CHO Ag’-invasive properties.
 Protein F- binds fibronectin on epi. Surface
 Lipoteichoic acid loosely binds strepto’ to epi
surface. F prtn, M prtn secures adhesion.
20

21. Virulence factors
B) Exotoxins
 Streptococcal pyrogenic exotoxins (SPE) / erythrogenic
toxins / Dick toxins – A, B, C.
 Act as superantigens.
 Excessive release of cytokines & interleukins from T-cells
→ inflammatory shock (TSS).
 Hemolysins – Streptolysin O & S.
21

22. Streptolysin O
 Oxygen labile
 Broth culture + sod.
hydrogen sulphite
 Cardiotoxic
 Freely secreted
 Antigenic
 ASO titer imp. in
rheumatic fever
Streptolysin S
 Oxygen stable
 Broth culture + RNA
 Nephrotoxic
 Cell bound
 Nonantigenic
 Stimulates release of
lysosomal enzymes. But
exact pathogenic role
unknown
22

23. Virulence factors
C) Enzymes
 Streptokinase –
 dissolves fibrin wall around site of
inflammation → spread of streptococci.
 Hyaluronidase –
 Helps in spread. (spreading factor).
 Nuclease /DNAse /Streptodornase
 Dissolve thick pus & help in spread.
 Neuraminidase – helps in mucosal
colonisation.
23

24. Host defenses
 First line defense / nonspecific defense –
 Barrier of skin
 Mucociliary defense in resp. tract.
 Cough & sneeze reflex.
 Second line defense –
 Complement activation.
 Antistrepto. antibodies in serum.
 Opsonization & phagocytosis.
 Autophagy of phagocyte if killing impossible.
24

25. Epidemiology
 Reservoirs – widely distributed in
nature. + Part of normal flora.
 Sources – patients & carriers.
 Transmission –
 a) droplets / contaminated dust
→ URTI;
 b) Milk → bovine mastitis;
 c) fomites, insects (eye gnats) →
skin infn.
 Age – two peaks; a) 5-8 yrs. b) at
12-14 yrs.
25

26.  Sex – males > females.
 Season –
 winter in temperate climates; all seasons in tropics.
 Predisposing factors –
 Crowding
 Medical problems
 Immunity – associated with antibody to M-protein.
26

27. Diseases
A) Suppurative
 Pharyngitis , tonsillitis,
URTI.
 By earlier serotypes.
 Swollen, red post.
pharyngeal wall.
 Complications –
peritonsillar & retro-
pharyngeal abscess,
sinusitis, otitis media,
mastoiditis etc.
27
Streptococcal sore throat, with enlarged tonsils
covered with white fibrinous exudate

28.  Skin & soft tissue infections
 By later serotypes. Common in small children.
 Impetigo –
 Small papules, vesicles, pustules → thick crusts
 Ecthyma –
 Ulcerated lesion
(staphylococcal lesions produce larger vesicles & bullous ulcers.)
28

29.  Erysipelas
 In older children.
 Red, swollen, edematous, indurated skin with sharply demarcated
lesions.
 Repeated attacks.
 Due to SPE- B & C.
29

30.  Cellulitis –
 In skin with breach in continuity.
 Lesion –
 Red, swollen, painful
 Not raised or demarcated.
 Lymphangitis, bacteremia common.
30

31.  Necrotizing fascitis / streptococcal gangrene –
 Skin with breach in continuity.
 1-2 days – erythema & purple bullae.
 7-10 days –
 Demarkated lesion.
 Skin breaks open.
 Underlying necrosed tissue seen.
31

32.  Streptococcal toxic shock syndrome –
 Wound infections of skin due to type M1, M3.
 Due to SPE- A, B, C.
 Super antigens. → inflammatory shock, renal failure & ARDS.
 Extensive necrosis of skin & s/c muscles.
32

33.  Other invasive infections –
 Puerperal sepsis.
 Anaerobic infections cause sepsis.
 Abscess formation in kidney, brain & other organs.
33

34. Diseases
B) Nonsuppurative
 Acute rheumatic fever & glomerulonephritis.
 Both seen 1-3 weeks after ac. strepto. infn.
 RF seen after pharyngitis but not after cut. Inf.
 GN seen after dermal infections
 No virulence factor of streptococcus is solely responsible
for both the diseases.
34

35. Rheumatic fever
 Pathogenesis
 Molecular mimicry & autoimmunity –
M protein Heart
Membrane antigen Skin & joints
Group sp. CHO Brain
 Genetic predisposition of some B-alloantigens
 Pathology
 Thick mitral, aortic & tricuspid valves.
 Thick chordae tendinae.
 Thick myocardium.
35

36. Thick mitral valve.
Thick chordae tendinae.
Thick myocardium.
Thickened &
calcified Aortic
valves due to RHD.
36

37.  Histopathology
 Aschoff nodule
 In interstitium
around vessels
 Rosette of
giant cells
around central
necrosis.
37

38.  Diagnosis – Jone’s criteria
Major criteria –
• Arthritis
• Carditis
• Chorea
• Erythema
marginatum
• Subcutaneous.
nodules
Minor criteria –
• Arthralgia
• Fever
• Raised ESR
• Raised CRP
• Increased P-R
interval in ECG.
Antecedent streptococcal infection – positive culture,
ag’ detection, rising ab’ titre (ASO).
38

39. Glomerulonephritis
 Pathogenesis –
 Molecular mimicry & autoimmunity
Protein antigens of nephritogenic streptococci  endostreptosin under
glomerular B.M.
 Immune complex disease with deposition of IgG + complement under
glomerular basement memb.
 Features –
 Pallor, edema, hypertension, hypoalbuminemia, rusty/ smoky urine with
↑proteins, RBCs & WBCs.
 Self-limiting. Resolves without any permanent damage.
39

40. Bowman’s
capsule

41. Differences ACUTE RHEUMATIC
FEVER
ACUTE
GLOMERULONEPHRITIS
Site of infection Throat Throat / skin
Prior sensitization Essential Not necessary
Serotypes Any Pyodermal types
Immune response Marked Moderate
Complement level Unaffected Lowered
Genetic susceptibility Present Not known
Repeated attacks Common Absent
Penicillin prophylaxis Essential Not indicated
Course Progressive / static Spontaneous resolution
Prognosis variable good

42. Differential diagnosis
▰ Diphtheria and Viral pharyngitis
▰ Scarlet fever: Mediated by streptococcal
pyrogenic exotoxins (e.g. SPE-A, B, and C)
▰ Characterized by pharyngitis and rashes (with
sandpaper feel), strawberry tongue (enlarged
papillae on a coated tongue). Rashes in the skin
folds - Pastia’s lines

43. Laboratory diagnosis
 Specimens –
 Throat swabs, pus, blood, CSF/body fluids, infected
tissues from cellulitis/ erysepelas.
 Collection –
 Under vision with aseptic precautions in a sterile
container.
 Transport –
 Immediate / immediate plating on B. A.
 Transport medium – Pike’s medium (B.A.+ C.V. +Na-
azide).
43

44.  Smears (Gram stain) –
 Pus & body fluids. No value for throat & genital specimens.
 Culture –
 Sheep B. A. without NAD (H. influenzae can’t grow). Incubation in 5-10%
CO2.
 Colony morphology & hemolysis.
 Selective medium – sheep blood agar + cotrimoxazole or crystal violet
(1:500000).
 Biochemical reactions –
 Catalase –ve, 10% bile insoluble, sugar fermentation except ribose, PYR
+ve.
44

45.  Grouping & typing
 Bacitracin sensitivity
 6 mm disc, 0.1unit of bacitracin.
 Zone of inhibition, ≥ 11 mm
diameter.
 Lancefield grouping
 Griffith typing
 Phage typing
45

46.  Antigen detection in samples –
 Antigen extraction by pronase / nitrous acid.
 Techniques –
 Latex agglutination test (LAT).
 Enzyme immunoassay (EIA).
 Liposome immunoassay (LIA).
 Fluorescent antibody staining.
 Rapid detection of Strepto. pyo.
 DNA hybridization
46

47.  Serological diagnosis (retrospective diagnosis in RF & GN) –
 Antistreptolysin O- inhibit streptolysin O mediated RBC lysis.
Titers high in RF; low in GN.
Titers >200 Todd units significant.
 AntiDNAse B – inhibits DNAse B from hydrolyzing DNA-methyl green
conjugate.
47

48.  Other antibodies –
 Anti NADse
 Anti hyaluronidase
 Anti A-carbohydrate
 Rapid screening tests –
 Streptozyme test
 Passive hemagglutination (RBCs coated with streptococcal antigen)
48

49. OTHER TESTS FOR STR.
PYOGENES
1) Fluorescent antibody technique
2) Typing by precipitation or
agglutination
3) Rapid diagnostic test kits
available
4) ASO titre estimation
5) AntiDNAseB estimation
RAPID DIAGNOSTIC
TEST KIT

50. Prophylaxis
 Life long prophylaxis for Rheumatic fever –
 Prevents reinfection & further damage to heart.
 Long acting penicillins, erythromycins, sulfadiazine (to
prevent recurrent attacks).
 Not useful in c/o glomerulonephritis as it occurs after
single infn and there is no reinfection.
50

51. Treatment
 Cellwall active agents used.
 Penicillins, macrolides (erythro’, azithro’), clindamycin,
vancomycin, cephalexin.
 Surgical debridement in c/o myositis, necrotizing
fascitis etc.
 For pharyngitis: Benzathine penicillin G, IM single dose or
oral penicillin V for 10 days.
 For recurrent pharyngitis: Clindamycin or amoxicillin-
clavulanate.
 For concomitant pneumonia and empyema: Penicillin G +
drainage of empyema.
51

52. Other hemolytic streptococci
 45% of total strepto. Isolates = Gr. A.
 15%
,, ,, ,, ,, = Gr. B.
 15%
,, ,, ,, ,, = Gr. C.
 25%
,, ,, ,, ,, = Gr. G.
 5 %
,, ,, ,, ,, = Gr. F.
52

53.  Group B streptococci –
 Identified by hippurate hydrolysis, CAMP test.
 Hippurate benzene ring + serine
Overnight growth in broth
culture → Centrifuge →
Deposit → Red ppt. on
addition of FeCl3.
Colony suspension in
broth → Incubate for 4
hrs. → Purple colour on
addition of ninhydrin.
HIPPURICASE
53

54. CAMP test
Staph. aur
Gr. B
Gr. A
54

55.  Infections
 Bovine mastitis.
 Colonizes female genital tract → septic abortion & puerperal
sepsis.
 Neonatal septicemia & meningitis.
 Early onset (within 1wk.) - vertical transmission from vagina.
 Late onset (2-12 wk.) – horizontal transmission from environment.
 Adult infection
 Skin & soft tissue infections, bone infections.
 Pneumonitis & septicemia.
55

56.  Group C streptococci
 Animal pathogens.
 Strepo. equisimilis – human pathogen.
 Infections of deep tissues, bones, brain & heart.
 Important source of streptokinase (used in thrombolytic therapy).
 Group F streptococci
 Minute streptococci.
 Streptococcus MG - -h streptococci in PAP. Used in diagnosis of
serological test of mycoplasma pneumonia.
56

57.  Group D streptococci –
 Two types –
 Enterococcal group – Enterococcus fecalis, E. fecium.
 Nonenterococcal group – Strepto. bovis, Strepto. equinus.
 Pairs of oval cocci arranged at angles.
 Dark magenta colored coloured colonies on MacConkey’s agar; black
colonies on BPT.
 Grow at 45°C, at pH 9.6, in 6.5% NaCl, in 40% bile; and hydrolyse esculin.
57

58. Bile Esculin Agar Bile Esculin Agar
NEG POS
58

59. Viridans streptococci
 Oral streptococci.
 Grow at acidic pH.
 Produce dental plaques & caries.
 Tooth extraction → bacteremia → endocarditis
affecting heart valves.
59