5. • These are gram positive, spherical, 0.5 to 1 mu
meter in diameter and are arranged in chains.
• They are non motile and non sporing
6. CULTURAL CHARACTERISTICS
• They are aerobic facultative anaerobic
growing best at 22-40 degree C with optimum
temperature of 32 degree C & pH of 7.5.
• They grow well in media containing blood &
sugars
7. Serum Broth
• The organism In serum broth shows granular
growth with powdery deposits (no pellicle)
after 24 hours of incubation at 37 degree C
8. Blood agar medium
• On BAM, circular, transparent, pin point
colonies (0.5 to 1mm) are formed showing
alpha hemolysis.
9. PATHOGENECITY
• The organism is more invasive producing
septicemia & may spread along lymphatic &
blood stream causing different manifestations:
10. A. Suppurative infection
1. Acute infection of respiratory tract (Sore
throat)
Throat is the primary site of invasion
by Strep. pyogenes causing sore throat (acute
tonsillitis &/or pharyngitis).
11. • Tonsillitis is more common in older children &
adults. The organism may spread to
surrounding tissue causing otitis media,
mastoiditis, meningitis, peritonitis,
pneumonia.
12. • Scarlet fever:
This condition is produced by
erythrogenic toxin of the organisrn.
The disease consists of combination of sore
throat & generalized erythematous rashes
13.
14. 2. Skin infections:
a) Impetigo:
This skin infection is common among
young children, particularly Living in crowded
conditions.
Impetigo is a superficial discrete
crushed spot (< 1 inch in diameter).
It lasts for 1-2 weeks & heals
spontaneously without leaving any scar.
15.
16. b) Erysipelas:
It is an acute spreading lesion
involving superficial lymphatics. The affected
skin becomes red, swollen & indurated.
It is mostly found in elderly individuals
17.
18. B. NON-SUPPURATIVE COMPLICATIONS
These include:
1. Acute rheumatic fever (ARF):
It develops in small percentage (3%) of
individuals, 2-3 weeks after the onset of sore
throat characterized by fever, migratory
polyarthritis & Aschoff's nodules (subcutaneous
nodules).
Recovery occurs without residual injury to
the joints but permanent damage to the heart may
occur.
19. 2. Acute Glomerulonephritis (AGN):
It usually occurs after 1-3 weeks
of onset of Streptococcal sore throat,
characterized by haemattuia, albuminuria &
edema.
21. B. Bacteriological investigation:
• Specimen: Specimen is collected depending
upon nature of infection. Most important
specimen are throat swab, nasopharyngeal
swab, pus, sputum, CSF, blood etc.
22. • Microscopy:
Smears made from the above
specimen after Gram staining show Gram-
positive cocci arranged in chains associated with
pus cells.
23. • Culture:
Specimen should be inoculated
Immediately or transported to lab In Spike's
transport medium.
Specimen is inoculated in BAM &
incubated at 37'C for 24-48 hours.
Plates are incubated under 5-10%
carbon dioxide atmosphere for better hemolysis.
The colonies are small (pin point),
raised, typically matt or dry surrounded by beta-
hemolysis.
24. Biochemical tests
• -Sugar (lactose. glucose, maltose and dextrin)
fermentation test Is positive with production
of acid only.
• -Catalase test - negative.
• -Gelatin liquefaction test - negative.
-Bile solubility test - negative.
26. • Skin lest (Dick test).
The test is done to check the
susceptibility of a person to scarlet fever.
0,2ml erythrogenic toxin is injected
intradermally on the fore arm & same amount
(0.2 ml) of heat inactivated toxin Is injected on
other forearm.
27. • Observation:
A bright red rash appears within
6 hours & becomes maximum in 24 hours &
thereafter fades away. No reaction occurs in
control forearm.
