infection and immunity
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4
Normal flora
Medical Significance
Antagonism Mechanism • Competition for receptors on host cells • Competition for nutrients • Metabolic or toxic products
Questions Under what conditions do opportunistic pathogens cause diseases? What factors are associated with pathogenicity of pathogens? What do the virulence factors of pathogens include? What is the difference between endotoxins and exotoxins?
13
Exotoxin
Physical and chemical properties
Polypeptide
Heat-labile: 60-80℃, 30min
14
Exotoxin
Immunity: Be neutralized by Antibodies (anti-toxins)
Antitoxin Definition: a specific antibody capable of neutralizing the exotoxin that stimulates its production. Application: treatment or urgent prevention measure
Horse serum antibody
antigen antitoxin
Exotoxin
Toxicity
High Tissue specificity
17
Exotoxin
Three types
Neurotoxin
opisthotonos
Tetanus toxin ,clostridium tetani , rigid paralysis
Chapter 6 Bacteria Infection
1
This chapter focuses on
Definitions normal flora, opportunistic pathogen, dysbacteriosis, nosocomial infection, bacteremia, septicemia, pyemia , toxemia, carrier
Lipopolysaccharide (LPS)
heat-stable: 160℃, 2-4hrs
20
Endotoxin
21
Endotoxin
Immunity
weak no toxoid available
22
Endotoxin
Biologic activity
Weak Similar biological effects
Declination of the host immunity defense
Dysbacteriosis
Definition: the state in which the proportion of bacterial species and the number of the normal flora colonizing in a certain site of a host present large-scale alteration.
Heat-resistance Sensitive
Resistance
Immunity Toxicity
High, antitoxin, toxoid High, tissue specificity
Low, no toxoid
Low, no tissue specificity
24
Virulence
Fever(IL-1, TNF) Leukocyte reaction Endotoxic shock DIC (disseminated intravascular coagulation)
23
The differences between exotoxin and endotoxin
Properties
Result: It often lead to superinfection.
6
Section 2 Bacterial Pathogenesis
Pathogenicity
The ability of an infectious agent to cause disease. A qualitative term that refer to an organism's ability to
2
Section 1 Normal flora and Opportunistic pathogen
Normal flora
Bacteria
Opportunistic pathogen
Pathogen
Normal flora
Definition
Microorganisms that live on or in human bodies, and ordinarily do not cause human diseases
cause disease
Virulence
A quantitative measurement of pathogenicity Virulence involves invasion and toxigenicity.
ID50: Infectious dose for 50% of the test population LD50: Lethal dose (of a toxin) for 50% of the test
Enterotoxin
v. cholerae
disturb the processes that regulate ion and water exchange across the intestinal epithelium
Cytotoxin
diphtheria toxin inhibits protein synthesis
Definition: The ability of a microorganism to colonize, invade and spread through the host.
Toxin
9
Invasiveness
Adherence factors
Pili Neisseria gonorrhoeae
Origin Release composition
Exotoxin
endotoxin
G+ and G-
Secreted from living cells or released upon bacterial lysis
G-
Released upon bacterial lysis
Protein
LPS
Convalescent carriers and Healthy carriers
Infected animals
Endogenous infections
caused by opportunistic pathogens among normal flora
Nosocomial infections
Other surface structures LTA
பைடு நூலகம் Capsules and slime layers
Streptococcus pneumoniae
10
Invasiveness
Invasive enzymes
Hyaluronidase: hyaluronic acid Coagulase Collagenase
Nutritional function several B vitamins and vitamin K Immunity normal flora share many antigenic
determinants with pathogenic organisms
5
Opportunistic pathogens
population
Pathogenicity of pathogens
Important factors of pathogenicity
Virulence of bacteria The amount of entry The portal of entry
Virulence
Invasiveness
Virulence factors
invasiveness toxin
Adherence factor Capsule and slime layer Invasive enzyme exotoxin
endotoxin
25
Pathogenicity
The amount of entry
species of bacteria Host defense state
11
Toxin
Exotoxin Endotoxin
12
Exotoxin
Origin
Gram-positive bacteria (most) Gram-negative bacteria
Release
Secreted by living bacteria (most) Released upon bacterial lysis
26
Pathogenicity
The routes of entry
Skin Respiratory tract Gastrointestinal tract Urogenital track Multiple routes
27
Section 3 Initiation and Course of Infection
Sources of infectious diseases Exogenous infections
Patients
Carriers
Those in whom pathogens multiply and may be transmitted to other individuals, but who shows no clinical findings to their presence.
18
A-B toxins
Active
Cell surface Binding
A
B
19
Endotoxin
Origin and release
Gram-negative bacteria Released only when bacteria lyse
Chemical and physical properties
28
Sources of infectious diseases
Nosocomial infections
Definitions: infections acquired in a hospital. Also called hospital-acquired infections.
Definition
normally nonpathogenic microorganisms capable of causing infection disease under certain conditions.
Conditions
Alteration of colonization sites
Toxoid Definition: a modified exotoxin that has been treated to destroy its toxicity and remains immunogenicity. Application: vaccine
15
toxin
toxoid
hypersensitivity
The various bacteria and fungi that are permanent residents of certain body sites, especially the skin, oral cavity, colon and vagina, usually do not cause any problems for the host body.
Normal flora
Medical Significance
Antagonism Mechanism • Competition for receptors on host cells • Competition for nutrients • Metabolic or toxic products
Questions Under what conditions do opportunistic pathogens cause diseases? What factors are associated with pathogenicity of pathogens? What do the virulence factors of pathogens include? What is the difference between endotoxins and exotoxins?
13
Exotoxin
Physical and chemical properties
Polypeptide
Heat-labile: 60-80℃, 30min
14
Exotoxin
Immunity: Be neutralized by Antibodies (anti-toxins)
Antitoxin Definition: a specific antibody capable of neutralizing the exotoxin that stimulates its production. Application: treatment or urgent prevention measure
Horse serum antibody
antigen antitoxin
Exotoxin
Toxicity
High Tissue specificity
17
Exotoxin
Three types
Neurotoxin
opisthotonos
Tetanus toxin ,clostridium tetani , rigid paralysis
Chapter 6 Bacteria Infection
1
This chapter focuses on
Definitions normal flora, opportunistic pathogen, dysbacteriosis, nosocomial infection, bacteremia, septicemia, pyemia , toxemia, carrier
Lipopolysaccharide (LPS)
heat-stable: 160℃, 2-4hrs
20
Endotoxin
21
Endotoxin
Immunity
weak no toxoid available
22
Endotoxin
Biologic activity
Weak Similar biological effects
Declination of the host immunity defense
Dysbacteriosis
Definition: the state in which the proportion of bacterial species and the number of the normal flora colonizing in a certain site of a host present large-scale alteration.
Heat-resistance Sensitive
Resistance
Immunity Toxicity
High, antitoxin, toxoid High, tissue specificity
Low, no toxoid
Low, no tissue specificity
24
Virulence
Fever(IL-1, TNF) Leukocyte reaction Endotoxic shock DIC (disseminated intravascular coagulation)
23
The differences between exotoxin and endotoxin
Properties
Result: It often lead to superinfection.
6
Section 2 Bacterial Pathogenesis
Pathogenicity
The ability of an infectious agent to cause disease. A qualitative term that refer to an organism's ability to
2
Section 1 Normal flora and Opportunistic pathogen
Normal flora
Bacteria
Opportunistic pathogen
Pathogen
Normal flora
Definition
Microorganisms that live on or in human bodies, and ordinarily do not cause human diseases
cause disease
Virulence
A quantitative measurement of pathogenicity Virulence involves invasion and toxigenicity.
ID50: Infectious dose for 50% of the test population LD50: Lethal dose (of a toxin) for 50% of the test
Enterotoxin
v. cholerae
disturb the processes that regulate ion and water exchange across the intestinal epithelium
Cytotoxin
diphtheria toxin inhibits protein synthesis
Definition: The ability of a microorganism to colonize, invade and spread through the host.
Toxin
9
Invasiveness
Adherence factors
Pili Neisseria gonorrhoeae
Origin Release composition
Exotoxin
endotoxin
G+ and G-
Secreted from living cells or released upon bacterial lysis
G-
Released upon bacterial lysis
Protein
LPS
Convalescent carriers and Healthy carriers
Infected animals
Endogenous infections
caused by opportunistic pathogens among normal flora
Nosocomial infections
Other surface structures LTA
பைடு நூலகம் Capsules and slime layers
Streptococcus pneumoniae
10
Invasiveness
Invasive enzymes
Hyaluronidase: hyaluronic acid Coagulase Collagenase
Nutritional function several B vitamins and vitamin K Immunity normal flora share many antigenic
determinants with pathogenic organisms
5
Opportunistic pathogens
population
Pathogenicity of pathogens
Important factors of pathogenicity
Virulence of bacteria The amount of entry The portal of entry
Virulence
Invasiveness
Virulence factors
invasiveness toxin
Adherence factor Capsule and slime layer Invasive enzyme exotoxin
endotoxin
25
Pathogenicity
The amount of entry
species of bacteria Host defense state
11
Toxin
Exotoxin Endotoxin
12
Exotoxin
Origin
Gram-positive bacteria (most) Gram-negative bacteria
Release
Secreted by living bacteria (most) Released upon bacterial lysis
26
Pathogenicity
The routes of entry
Skin Respiratory tract Gastrointestinal tract Urogenital track Multiple routes
27
Section 3 Initiation and Course of Infection
Sources of infectious diseases Exogenous infections
Patients
Carriers
Those in whom pathogens multiply and may be transmitted to other individuals, but who shows no clinical findings to their presence.
18
A-B toxins
Active
Cell surface Binding
A
B
19
Endotoxin
Origin and release
Gram-negative bacteria Released only when bacteria lyse
Chemical and physical properties
28
Sources of infectious diseases
Nosocomial infections
Definitions: infections acquired in a hospital. Also called hospital-acquired infections.
Definition
normally nonpathogenic microorganisms capable of causing infection disease under certain conditions.
Conditions
Alteration of colonization sites
Toxoid Definition: a modified exotoxin that has been treated to destroy its toxicity and remains immunogenicity. Application: vaccine
15
toxin
toxoid
hypersensitivity
The various bacteria and fungi that are permanent residents of certain body sites, especially the skin, oral cavity, colon and vagina, usually do not cause any problems for the host body.