Medical Microbiology

一 concept of microoranism : 二 type of microorganism: 1 non-cell type 2 prokaryotes 3 eukaryotes 三 general properties of M: 1 tiny in size 2 simple in structure 3 active in metabolism 4 fast rate in multiplication 5 easy in variation 6 widely distributed

四 relationship to human ( 一 )  C .N circulation in nature

( 二 )  in industry 、 agricuture 、 medicine ( 三 )  make up of normal flora of human being 1 anti-pathogen 2 provide nutrition ( 四 )  some M are pathogens 1 pathogens 2 opportunistic pathogens

五 history : leeuwenhoek . 1676 .microscopy (>200 times )

Pasteur (1822-1895 ) :

1 yeast cells cause wines sour 2 pebrine caused by protozoan 3 spontaneous generation controversy

4 chickens: 42 , do not acquire anthrax℃ 37 ,do ℃5 vaccine for rabies

koch : (1843—1910)

1 cultivation techniques 2 staining 3 isolated TB 4 Koch’s postulates :

①microbes are observed in tissue specimens from dead animals ; ②isolated and grown in pure culture ; ③inoculated to a health animal ; ④the disease is produced in the animal ; ⑤then 1 ⑥then 2

六 object of medical microbiology pathogens 七 why we study medical microbiology 八 how to study ---:

Chapter 1 . Bacterial

Morphology and Structure

§1 . size and shape of bacteria

size :tiny um (1um=1/1000 mm) shape : coccus : diplo~ , strepto~ tetrad ,sarcina , staphylo ~ bacillus : spiral bacterium :vibrio spirillum

§2 . structure of bacterium Structure of Bacteria: Essential structure: cell wall cell membrane cytoplasm nuclear material (nucloid) Special Structure capsule flagella pilus spore

一 Essential structure of bacteria ( 一 )  cell wall : 1 peptidoglycan : (1) a backbone (2) tetrapeptide side chains (3) cross bridges

2 teichoic acid (G+) (1) membrane ~ (LTA) (2) wall ~

functions : a. major surface Ag of G+ b. Regulating passage of ions into and out of G+ c. binding B onto host cell surface 3 G- (1) outer membrane . (2) LPS a. lipid A b. core polysaccharide c. O-specific polysaccharide

表 1 － 1 革兰阳性菌与阴性菌细胞壁结构比较

 

 

 

 

 

 

 

 

 

 

强度 较坚韧 较疏松

厚度 20 ～ 80nm 10 ～ 15nm

肽聚糖层数 可多达 50 层 1 ～ 2 层

肽聚糖含量 占细胞壁干重 50% ～ 80% 占细胞壁干重 5% ～20%

糖类含量 约 45% 15% ～ 20%

脂类含量 1% ～ 4% 11% ～ 22%

磷壁酸 ＋ －

外膜 － ＋

细胞壁 革兰阳性菌 革兰阴性菌

4 Functions of CW . (1) to form the external shape of B . (2) to protect B from bursting due to high osmolarity :G- 5~6 G+ 20~25 (3) A barrier to certain substances into and out of B . (4) Take part in B multiplication . (5) Associated with B antigenicity .

5 B with deficiency in CW (L Forms ) : Bacterium L-forms : (B with deficiency in CW ):

1 pleomorphic 2 grow in 5% NaCl , 12-15% sucrose . 3 grow slowly ( 2-7d ) 4 antibiotics resistant cells . 5 “fried egg” colony PC , 6 G+ , G- ----------- L – form lysozyme G+ protoplast G-       spheroplast 7 Clinic significant

( 二 )  cell membrane . Functions (1)  Transportation (2)  Respiration (3)  Biosynthesis (4)  Secretion Mesosome : (1)  Respiration (chondroid) (2) Take part in dividing of B

( 三 )  cytoplasm 1 Ribosome : 50S + 30S = 70S | | Erythromycin streptomycin 2 plasmid 3 cytoplasmic granules ( 四 ) Nuclear material (nucleoid )

二 special structure of Bacteria ( 一 )Capsule :

1 chemical component : polysaccharide polypeptide 2 Functions of capsule : (1)against phagocytosis (2)adhesion (3)protect B from damage. (against dry) Glycocalyx

（二） Flagellum :

1 structure 2 chemical composition : pro 3 Function : (1) Motility (2) Antigenicity (H – Ag) (3) Associated with pathogenicity (4) Differentiation for B

（三） Pilus :

1 common pilus : pathogenicity 2 sexpilus :conjugation F+ →F-

（四） spore :

1 Formation and Germination 2 Functions of spore high resistance to kill spore ： 121.3 , 15-20min℃ 1.05kg / cm2

To kill spore is an important index of

autoclaving .

§3 Methods for Identification and Detection of B 一 microscope magnification 1 light microscope 2 electron microscope 二 staining : （一） Gram stain Step1 step2 step3 1min 1min Crystal ------ Iodine ----- 95% Alcohol Violet wash 30Sec step4 30Sec -------- Safranin -------- microscope . （二） Acid – fast stain .