文档介绍：Chapter 10 Enteric bacilli
Outline
General properties of enteric bacilli
Escherichia(埃希菌属)
Shigella(志贺菌属)
Salmonella(沙门菌属)
Morphology
Gram-negative
Rod shaped (bacilli)
Most form pili and peritrichous flagella (周鞭毛)
Do not form spores
Culture characteristics
Facultative anaerobes (兼性厌氧) or aerobes (需氧)
Grow readily on simple media.
Colonies: circular, convex, smooth
Blood agar plate: some can form hemolytic zones.
Liquid media: turbid.
Biochemical reactions
Catalase(触酶)test: +
Reduce nitrate (硝酸盐) to nitrite (亚硝酸盐)
Oxidase (氧化酶) test: -
Lactose fermentation test (乳糖发酵试验)
乳糖发酵试验可用于初步鉴别肠道致病菌和非致病菌
肠道致病菌多数不发酵乳糖(沙门菌、志贺菌)
肠道非致病菌多数发酵乳糖(埃希菌)
Antigens
O antigens: LPS, IgM
H antigens: flagellin, IgG
Capsular antigens: type specific, Vi antigen and K antigen.
Resistance: relatively weak
Variation
Gram-negative rod-shaped bacilli
onkey agar
A culture medium designed to grow Gram-negative bacteria and stain them for lactose fermentation.
It contains bile salts (to inhibit most Gram-positive bacteria, except us and some species of us), crystal violet dye (which also inhibits certain Gram-positive bacteria), neutral red dye (which stains microbes fermenting lactose), lactose (乳糖) and peptone (蛋白胨).
onkey agar with lactose(left) and non-lactose(right) fermenters.
Smooth
Rough