2. streptococcus

MICROORGANISM

1. STREPTOCOCCUS RATHEESH R L

2. The medically important species is streptococcus pyogens

3. MORPHOLOGY

4. 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

5. 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

6. Serum Broth The organism In serum broth shows granular growth with powdery de­posits (no pellicle) after 24 hours of incubation at 37 degree C

7. Blood agar medium On BAM, circular, transparent, pin point colonies (0.5 to 1mm) are formed showing alpha hemolysis.

8. PATHOGENECITY The organism is more invasive producing septicemia & may spread along lymphatic & blood stream causing different manifestations:

9. 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 ).

10. Tonsillitis is more common in older children & adults. The organism may spread to surrounding tissue causing otitis media, mastoiditis , meningitis, peritonitis, pneumonia.

11. Scarlet fever: This condition is produced by erythrogenic toxin of the organisrn . The disease consists of combination of sore throat & generalized erythematous rashes

12. 2. Skin infections : 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.

13. 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

14. 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.

15. 2. Acute Glomerulonephritis ( AGN): It usually occurs after 1-3 weeks of onset of Strepto­coccal sore throat, characterized by haemattuia , albuminuria & edema.

16. LABORATORY DIAGNOSIS A. Hematological Investigation: TLC : Shows increase in leucocyte count DLC : Shows increase in neutrophil count. ESR: Raised .

17. 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.

18. Microscopy : Smears made from the above specimen after Gram staining show Gram-positive cocci arranged in chains associated with pus cells.

19. 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.

20. 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.

21. Serological tests Include-ELISA & Agglutination test.

22. 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.

23. Observation: A bright red rash appears within 6 hours & becomes maximum in 24 hours & thereafter fades away. No reaction occurs in control forearm.

24. Interpretation : Positive reaction means no Immunity & negative reaction means immunity to scarlet fever.

25. TREATMENT Penicillin , sulfonamide & several other antibiotics