streptococcus , it's properties, pathogenesis, lab diagnosis

1. Streptococcus
Dr. Kanwal Deep Singh Lyall
M.D. Microbiology

2. General Characteristics
• STREPTOS – twisted / coiled - Billroth (1874)
• Rosenbach – (1884) – S. pyogenes
• GPC in Chains – divide in one plane and daughter
cells remain attached
• 0.5 – 1 µm
• catalase negative,
• Normal flora and opportunistic pathogens
• Exacting nutritional demands – Blood , serum ,
sugars (only acid , no gas)

3. Structure
Carb. C Ag – Lancefield’s Grouping
M – protein – Most important,
inhib. Phagocystosis , heat & acid
stable , role in Rheumatic fever
T & R proteins - no virulence
Others – M assoc. protien , MAP
Serum opacity factor

4. Classification

5. Streptococcus
Oxygen requirement
Aerobes & facultative anaerobes
Hemolysis
Alpha HS
Beta HS NHS
Obligate anaerobes
e.g. Peptostreptococci
GREEN
Partial H’lysis
Small zone
Viridans Group
Pneumococci
Clear, Complete, 2 – 4mm
Streptolysin O
O2 labile, Seen in deep subsurface
colonies, Antigenic in nature
Streptolysin – S
O2 stable, surface h’lysis, non-antigenic
20 Lancefiled groups , based on
carbohydrate “C” antigen , A-V without I & J
Group – A ( S. pyogenes ) ,
Griffith serotypes – based on “M “ Protein, 1 – 80
Enterocococcus
Non- enterococcus
group

6. Streptococcus Pyogenes
• Beta HS, Lancefield group A
• H’lysis ↑ by 10% CO2
• Granular turbidity and powdery deposit
• Selective media – Crystal violet BA
• Non- soluble in 10 % bile salts , PYR + VE
• Delicate, stored in RCM @ 4° C

7. Toxins
1. Hemolysins O & S , ASO ( > 200 significant)
2. Pyrogenic / erythrogenic exotoxin :
– Rash in scarlet fever
– Types A, B, C
– Super-antigens
– Dick test – local injection in susceptible – local
erythema
– Schultz – Charlton Reaction – injection of
antisera in to above rash – blanching

8. Enzymes
1. Streptokinase – lysis of human fibrin clot
( Fibrinogen – fibrin )
2. DNAase – Group A, B, C & D – liquid pus
3. Nicotinamide – adenine – dinucleotidease
(NADase ) – leucotoxic
4. Hyaluronidase – breaks down hyaluronic acid
– favors spread

9. Diseases
Pyogenic
• RTI – tonsillitis , mastoiditis,
• Scarlet fever in cold
countries
• Skin infections –
lymphangitis, cellulitis,
Impetigo, erysepellas
Non – Suppurative complications
• Rheumatic fever
• Acute Glomerulonephritis

10. • Rheumatic fever :
– d/t repeated throat infections, marked immune
response, heredity tendency, penicillin prophylaxis
• Acute Glomerulonephritis :
– throat / skin infections, single infection, late
pyodermal and early throat strains, moderate
immune response , heredity tendency is not
known

11. Lab diagnosis

12. Sample
Transfer immidately or Pike’s media ( BA + C. violet + Na. azide)
Gram stain – CSF, PUS
Culture – BA @ 37 C X 18 – 24 hrs
Pin point colonies → Gram stain , GPC in chains
Catalase – ve , PYR + VE , Serum sugars (Ribose), Bacitracin , CAMP Test
AST, Lancefield Grouping

13. CAMP Test
• Christie, Atkins and Munch – Peterson
Beta HS
S. aureus streak
( Beta hemolysin
enhances hemolysis)
Enhanced zone of
Hemolysis (Butterfly
appearance )
Positive test
Negative test

14. Lancefield Grouping - Carbohydrate C Ag
extracted – Precipitation test
Growth in
Todd – Hewitt
broth
HCL- Lancefield’s
Streptomyces albus
enzyme – Maxtard’s
Formaldehyde
– Fuller’s
Autoclave –
Rantz & Randall’s

15. • Group A streptococcus
• St. pyogenes
• Hippurate hydrolysis –
ve
• CAMP – ve
• Bacitracin Sensitive
• Does not ferment
Ribose
• Group B streptococcus
• St. agalactiae
• Hippurate hydrolysis –
ve
• CAMP + ve
• Neonatal septicaemia
• Meningitis
• Bacitracin resistant
• Ribose fer. + ve

16. NHS (Gamma H’lytic)
• Non – enterococcal group
• S. Bovis
• S. equinus
• S. suis
• S. mutans
• Enterococcal Group
• E. faecalis (m/c)
• E. faecium
• E. durans
• E. avium
• Normal flora – GUT
• Heat R ( 60 °C x 30 m)
• Grow in 40 % bile,
@ 45 ° C, 6.5% NaCl,
@pH 9.6 , PYR + ve

17. Viridans Group
• S. salivarius
• S. sanguis
• S. Milleri (anginosus)
• Cause – SABE, Dental Caries

18. Pneumococcus

19. Pneumococcus
• S. pneumoniae
• Gram positive encapsulated (polysach)
flame/lancelate shaped diplococci
• Bile soluble , optochin sensitive
• Aerobes/ F. anaerobes
• Normal upper resp. tract flora
• Common cause of pneumonia & OM in
children

20. • Draughtsman colonies on prolonged incub.
• Normaly alpha HS – Beta HS under anaerobic
conditions – d/t – pneumolysin O
• Autolysis - ↑ by bile salts ( 10% in tubes, 2% on plate)
– d/t amidase – breaks bond between alainin &
muramic acid in peptidoglycan
• Hiss serum sugars – acid only
• Insulin fermentation + ve and sensitive to Optochin (5
µg)
• Capsular polysachride ( 90 types) – aka Soluble specific
substance – Vaccine m/c 23 types

21. • M – protein : Non – virulent, strain specific
• C substance – species specific – precipiated
buy abnormal protein – present in acute
infections, injury – acute phase reactant – CRP
– produced by hepatocytes
• Quellung (Neufeld reaction) :
Pneumococci + nantisera _ Meth. Blue =
capsular swelling ( d/t ↑ in refractive index)

22. Toxins and virulence factors
• Hemolysin – oxygen labile
• Leucocidin
• Capsule – most important
• Pneumolysin – cytotoxic, activates
compliment, immunopgenic

23. Pathogenicity
• M/C cause of bacterial pneumonia
• Lobar pneumonia – adults ( 1-12), children
( 6,14,19,23)
• Bronchopneumonia – almost always 2°
infection – all serotypes
• 2nd commonest cause of meningitis
• Phyranx blood stream meninges
• Empyema, pericarditis, conjunctivits etc.

24. Lab diagnosis
• Sample – CSF , Sputum , exudates
• Immediately transfer or keep at 37° C
(H. influenzae dies at 37 low t°)
• Direct microscopy or antigen fdetection by LAT or
coaglutination)
• BA @ 37 C x 18 – 24 hrs
• Colonies – alpha hs, G/S , Biochem. Rx (catalase, inulin
fermentation, bile sol, optochin)
• Animal pathogenicity – mies dies on IP injection x 48
hrs – s/c heart nlodd, peritoneal extraxt – pneumo.

25. India Ink Gram Satin
• Quellung reaction

26. • Pneumococcus
• Capsulated
• Flame shaped
• Draugtsman colonies
• Bile sol
• Granular tubidity
• Insulin ferm +
• Optochin sensitive
• Fatal to mice
• Viridans gp.
• Non- cap.
• Pairs , oval
• Dome shapped
• Non-bole sol.
• Deposit ( heavy chains)
• Rest negative