Microbial Pathogenisity

Question 1

Pathogenisity and virulence

Answer 1

*ability of microbial species to produce disease
*ability of strains of microbes to produce disease

Question 2

Factors affecting determinants of virulence

Answer 2

Adhesion
Invasiveness
Antiphagocytic factors survival within the phagocytes
Bacterial toxins
Enzymes
Sidaro force and iron accucision
Genetic factors
Infecting doss
Communicability

Question 3

Adhesion

Answer 3

-attachement of bacteria
-bw receptors of epithelial cells and adhesive structures (adhesin)
-adhesin as fimbrae/ fibrillae/ pili as colonisation factors

Question 4

Advantages of adherence

Answer 4

-prevent microbe from flushing away from mucus, peristalisis in gut, urine
-toxins at high conc to host cells
-if bacteria is invasive, then helps in penetrating the host cells
-structures play role in adherence
*Outer membrane proteins
*flagella
*lipopolysaccharide
*glycocalyx

Question 5

Invasiveness

Answer 5

Ability to spread within the host
-highly invasive pathogen, spreading or generalised lesions
Eg,streptococcal infections
-less invasive pathogen, cause localised lesions
Eg,staphylococcus abscess
-some produce fatal disease, remain confined to a site and produce that elaborate toxin
Eg,tetanus bacillus

Question 6

Antiphagocytic factors

Answer 6

-macrophage and polymorphs
-certain factors opposing phagocytes
*capsule
*streptococcal M.protein
*cytotoxin
*bacterial surface antigen

Question 7

Antiphagocytic factors
Capsule

Answer 7

Capsule-gelatinous layer
Mostly polysaccharides, polypeptide in bacillus
With capsule-high virulence,prevent phagocytosis
Noncapsulated-low virulence

Question 8

Anti phagacytic
*Streptococcal Mprotein
*cytotoxin
*bacterial surface antigen

Answer 8

M.protein in groupA streptoccoci +fibrinogen and fibrin in bacterial cell wall

Cytotoxin
By certain bacteria interfere with chemotaxis or kill the phagocyte
Eg haemolysin and leukocidin by staph.aureaus

Bacterial surface antigen
Eg Vi antigen of s.typhi and k antigen of E.coli resist phagocytosis

Question 9

Survival of bacteria within phagocytes

Answer 9

As phagolysosome-phagosome +lysosome
By interfering the formation of phagolysosome can survive intracellularly or prevent phagocytosis

1,interfering with oxidative host
2,prevention of fusion and degranulation
3,resistance to lysosomal enzyme
4,escape from phagosome

Question 10

To interfere phagolysosome with oxidative burst

Answer 10

2 products ,super oxide and hydrogen peroxide

*catalyse enzyme by staphylococcus aureus breaks h202
*enzyme superoxide dismutase by lysteria monocytogenus which neutralise oxygen radicle

Question 11

Fusion and degranulation to prevent phagocytosis

Answer 11

-Preventing fusion by phagosomal membrane modification
-enzyme which Inhibit degranulation

Question 12

3,resistance to lysosomal enzyme
4,escape from phagosome

For the survival of bacteria

Answer 12

3,presence of capsular coat
4,escape into cytoplasm of host cells before fusion

Question 13

Bacterial toxins as pathogenisity

Answer 13

Entotoxin
-lycopolysaccharide of gram-ve bacteria
-released from bacterial surface by natural lysis of bacteria/ disintegration of bacterial cellwall
-Heat stable

Exotoxin
-Heat labile
-secreated by certain bacteria
-diffuse into surrounding medium

Question 14

Enzymes as pathogenisity

Answer 14

1,protease
2,kinase
3,hyrylonudase
4,coagulate
5,collagenase

Question 15

Functions of enzymes

Question 16

Function of enzymes

Answer 16

Protease-cleaves IgA
Kinase-enhance bacteria by dissolving fibrin
Hyrylonudase-breaks hyrylonic acid which helps in spreading of infection
Coagulate-deposition of fibrin around bacteria that prevents phagocytosis
Collagenase-break collagen in connective tissue and helps in spreading of infection

Question 17

Sidero force and iron accusision as pathogenisity

Answer 17

-Acquire iron from iron binding proteins from host cells by sidero force(low molecular weight)
-Iron required for their metabolism
-enhance bacterial virulence

Question 18

Genetic factors as pathogenisity

Answer 18

Plasmids-extra chromosomal DNA segments that carry genes for antibiotic resistance

Question 19

Infecting doss

Answer 19

-adequate no of bacteria required for infection
-depends on virulence of bacteria
-2 types
MID-min no of bacteria to produce clinical infection
MLD-min no of bacteria to produce death in the animal

Question 20

Communicability
Root of infection

Answer 20

*Ability of microbe to spread from one host to another
*when introduced through optimal route, bacteria are infective