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Alpha haemolytic

streptococciStreptococcus pneumoniae and

Viridans streptococci

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Alpha haemolytic

General properties:

G +ve cocci in short chain (Viridans) or Lancetshape diplococci (S. pneumoniae), catalase ve, nonspore forming, non motile some are capsulated.

Dose not possess C carbohydrate so Not included in

Lance field grouping.

Produce partial zone of haemolysis with greenpigmentation on blood and chocolate agar.

Could not grow on MacConkey or CLED.

Normal habitat:

S. viridans found in large number in the mouth andG.I.T.

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Viridans streptococci

Species: S. sanguis.

S. mitior.

S. mutans.

S. salivarius.

S. milleri.

Disease caused by Viridans streptococci: Dental caries with other anaerobic bacteria.

Sub-acute bacterial endocarditis.

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Dental caries

Caused by formation of Dental Plaque

(accumulation of bacteria on tooth) with

fermentation of carbohydrate producing a lot of

lactic acid which cause demineralization to

tooth.

The most common cause is S. mutans and S.

salivarius, with anaerobic actinomyces,bacteroides, fusobacterium and spirochetes.

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S. pneumoniae

G+ve lancet shape diplococci that possess

polysacharide capsule. They are capnophilic

(require 5-10% CO2).

Antigenic Serotyping:

About 83 different serotypes distinguished by

Quellung reaction due to differences in capsular

polysaccharide antigen. Types 1,2,3,5,7,8,9,12,14,18and 19 cause severe infection.

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Diseases caused by S. pneumoniae

Cause a disease after influenza virus infection.

Pneumonia (Bronchial and lobar pneumonia).

Sinusitis.

Otitis media.

Meningitis.

Septicaemia.

Conjuctivitis.

Perotinitis.

Arthritis.

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Laboratory diagnosis

Specimens:

Direct Gram stain:

Culture: on Chocolate agar incubated on candle jar. Biochemical reaction:

Optochin sensitivity (disk with 5g Ethyl hydrocurpurin

dihydrochloride)

Inulin fermentation

Bile sensitivity (Na taucholate or Na deoxycholate)

Animal pathogenicity.

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Characters S. viridans S. pneumoniae

Gram stain G +ve cocci in

short chain

G +ve lancet

shape diplococciCultural characters

after 48 hours

Small low convex Draughtmann

appearance

Growth on broth Granular turbidity Uniform turbidityOptochin sensitivity Resist Sensitive

Inulin fermentation No Yes

Bile sensitivity Resist Sensitive

Animal pathogenicity Non pathogenic Pathogenic

Capsule Non capsulated Capsulated