Salmonella

Question 1

Morphology

Answer 1

1. Gram negative rods
2. 1-3 micron x 0.5
3. Capsulated
   Motile with preitrichate flagella
   Non sporing but contains fimbriae

Question 2

Cultural characteristics

Answer 2

•Aerobic but facultative anaerobe
•Grow on simple media
•Ph 6-7
•Tem 15-41
•Colonies are circular mildly convex and translucent
•Mac conkey agar- non lactose fermenting colonies
•Deoxycholate citrate agar and xylose lecithin deoxycholate medium- colonies gave black head because of h2s gas production
•Wilson and blair medium - contains bismuth sulphide gives metallic colour
• selenite f and tetrathionate broth are used as enrichment medium

Question 4

Antigenic properties

Answer 4

• flagellar antigen H
• somatic antigen o
• vi antigen found in few species ( protective antigen for o )

Question 5

Ideal time to widal test

Answer 5

1 week

Question 6

H antigen

Answer 6

• heat labile
• destroyed by heat and alcohol and not formaldehyde
• when mixed with antibodies give rise to agglutination reaction in the form of fluffy cotton like balls
• induces antibody formation after infection or immunization

Question 7

O antigenic

Answer 7

• somatic antigen
• protein, phospholipid and polysaccharide complex
• not destroyed by heat or alch
• when mixed with antisera forms compact chalky disc material

Question 8

Vi antigen

Answer 8

Polysaccharide in nature
It masks the o antigen

Question 9

Pathogenicity

Answer 9

1. Enteric fever
2. Food poisoning
3. Septicaemia