Bacterial pathogenesis
Download
1 / 58

Bacterial Pathogenesis - PowerPoint PPT Presentation


  • 183 Views
  • Uploaded on

Bacterial Pathogenesis. The term infection describes the process that pathogenic microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body. Section 1 Normal flora and opportunistic pathogens.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Bacterial Pathogenesis' - avel


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript


Section 1 normal flora and opportunistic pathogens
Section 1 Normal flora and opportunistic pathogens microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Definition: microorganisms that live on or in human bodies, and ordinarily do not cause human diseases but under certain condition can cause disease


pathogen microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.


The distribution of normal flora microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.


Normal flora
Normal flora microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Skin

Staphylococcus epidermidis

Diphtheroids

Streptococci

Peptococcus


The significance of normal flora
The significance of normal flora microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • constitute a protective host defense mechanism: Competition of nutrients and receptors

    Metabolic substances by normal flora: e.g., bacteriocins, antibiotics, etc.

  • serve a nutritional function:several B vitamins and vitamin K

  • keep our immune systems in tune

    normal flora share many antigenic determinants with pathogenic organisms


Opportunistic pathogens
Opportunistic pathogens microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Definition: normally nonpathogenic microorganisms capable of causing infection disease in an immunosuppressed host.

  • Conditions of causing diseases by opportunistic pathogens:

  • Alteration of colonization sites

  • Declination of host immune system function


  • Dysbacteriosis microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

    Definition: the state in which the proportion of bacterial species and the number of the normal flora colonizing in certain site of a host present large-scale alteration.


Nosocomial infections
Nosocomial infections microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Infectious diseases acquired as a result of a hospital stay are known as nosocomial infections.

  • Surgical procedures and lower defenses permit resident flora

  • Indwelling devices

  • Fomites ,medical equipment,other patients


Section 2 bacterial pathogenesis

toxins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Cause disease

细菌

bacteria

bacteria

细菌

bacteria

bacteria

Section 2 Bacterial pathogenesis

bacteria

细菌

inbody

outerbody

Immune status of the host


Why do animal get infectious diseases
Why do microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.Animal get infectious diseases?

From the organism’s perspectives

The number of organisms

The virulence of these organisms

From the host’s perspective

Innate immunity

acquired immunity

Antibody-mediated

cell-mediated


Pathogenicity of bacteria
Pathogenicity of bacteria microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Pathogenicity and virulence: refer to an organism's ability to cause disease.

  • LD50 (median lethal dose) or ID50 (median infectious dose):refers to the number of bacteria or amount of bacterial products, such as toxins, that cause death or bacterial disease in 50% of animals in a defined period after the bacteria are administrated by a designated route.


Pathogenicity of bacteria1
Pathogenicity of bacteria microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • pathogenicity(determined by):

  • virulence factors of the bacterium

  • the number of infecting bacteria

  • route of entry into the body


Virulence factors
Virulence factors microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Invasiveness

  • Definition: the ability of a microorganism to invade human cells or tissues,and to multiply on or within them.


  • Capsules and slime layers: microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.e.g., pneumococci

  • Interfere with the ability of phagocytic blood cells to engulf and destroy bacteria and protect bacteria against some antimicrobial substance


2 adhesins
2.Adhesins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Bacterial infections are usually initiated by adherence of the microbe to a specific epithelial surface of the host,otherwise the organism is removed

  • Peristalsis and defecation ciliary action,coughing and sneezing or urination

  • A specific “stickiness”


(1)Finbrial adhesins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

involved in mediating attachment of some bacteria to mammalian cell surfaces


(2)Non-fimbrial adhesin microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Including the filamentous haemagglutinin of Bordetella pertussia,a mannose-resistant haemagglutinin from Salmonella serotype Typhimurium and a fibrillar haemagglutinin from helecobacte pylori

Pili: e.g., Neisseria gonorrhoeae

Other surface structures of bacteria: LTA


Other extracelluar aggressins
Other extracelluar aggressins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Invasive enzymes:

    e.g.Coagulase:working in conjunction with serum factors to coagulate plasma.contributes to the formation of fibrin walls around staphylococcal lesions.


  • Toxins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Exotoxin

  • Definition:a soluble protein toxin usually secreted from a living bacterium.


  • Origin and release: microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.produced by Gram-positive bacteria as well as Gram-negative cells

  • Physical and chemical properties:proteins and usually heat-labile.


Virulence factors1
Virulence factors microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Toxins

  • Exotoxin

  • Immunity: excellent antigens that elicit specific antibodies called antitoxins.


Antitoxin: microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Definition: a specific antibody capable of neutralizing the exotoxin that stimulates its production.

Toxoid:

Definition: a modified exotoxin that has been treated to destroy its toxicity and remains immunogenicity.


Virulence factors2
Virulence factors microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Exotoxin

  • Component characteristics: most exotoxins consist of two parts, an A (active) component and a B (binding) component.

Toxicity: high and even fatal; highly tissue specificity


  • Categories: microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

    Cytotoxins: exotoxins that destroy the target cells directly by various mechanisms.

    Neurotoxins: exotoxins that affect nerve transmission of the nerve system.

    Enterotoxins: exotoxins that stimulate hypersecretion of water and electrolytes from the intestinal epithelium and produce watery diarrhea.


Exotoxin
Exotoxin microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Neurotoxin

Tetanus toxin ,clostridium tetani

glycine spastic paralysis

Botulinum toxin, clostridium botulinum

acetylcholine flaccid paralysis

Cytotoxin diphtheria toxin inhibits

protein synthesis

Enterotoxins v. cholerae

perturb the processes that regulate ion and water exchange across the intestinal epithelium


Virulence factors3
Virulence factors microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

Endotoxins

  • Origin and release:

    produced only by Gram-negative bacteria and released only when bacteria lyze.

  • Chemical and physical properties:

    lipopolysaccharide of the outer membrane of Gram-negative bacteria; heat-stable


Endotoxins
Endotoxins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Immunity: weakly immunogenic

  • Biologic activity:

    lipid A is the primary toxic component

    all endotoxins present similar biologic effects.

    Pyrogenicity

    Leukocyte reaction

    Endotoxemia and endotoxin shock

    DIC (dissemiated intravascular coagulation)


Endotoxin microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

(especially lipid A))

Activates

Hageman fatcor

Activates

complement

Activates

macrophages

C3a

Hypotension

Edema

TNF

Fever and hypotension

C5a

Neutrophil chemotaxis

Coagulation cascade

DIC

IL-1

Fever

Nitric oxide

hypotension


Endotoxins1
Endotoxins microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Detection of endotoxin: The Limulus lysate test


The different between indotoxin and exotoxin
The different between indotoxin and exotoxin microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.


Virulence of pathogenic bacterial microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.


Portals of entry and the size of the inoculum
Ⅱ.Portals of Entry and the size of the inoculum microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • If certain pathogen enter the wrong portal,they will not be infectious.

  • Occasionally,an infective agent can enter by more than one portal.e.g.mycobacterium tuberculosis.


Portals of entry
Portals of entry microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • skin

  • respiratory system

  • ingestion system

  • genitourinary system

    C. tetani


The size of the inoculum
The size of the inoculum microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • The quantity of microbes in the inoculating dose.


The originate and progress of infection
Ⅲ.the originate and progress of infection microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • A.The source of the infection

  • B.routes of pathogen transmission

  • C.Patterns of infection


A the source of the infection
A.The source of the infection microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Living reservoirs

    Persons or animals with frank symptomatic infection are obvious sources of infection

  • Nonliving reservoirs


Sources of infectious diseases microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Exogenous infections:

  • Patients

  • Carriers: those in whom pathogens are present and may be multiplying, but who shows no clinical response to their presence.

  • Contaminated animals

  • Endogenous infections


  • Carrier state microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • Definition of carriers: those in whom pathogens are present and may be multiplying, but who shows no clinical response to their presence

  • Definition of carrier state: a type of infections causing no signs of symptoms, in which pathogens multiply and may be transmitted to other individuals


  • two major types of carrier: microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

    Convalescent carriers: those who recover from infectious disease and in whom the pathogens remain and multiply without causing overt symptoms.

    Healthy carriers: those who do not have the clinical symptoms but carry pathogens indeed.

    Typhoid Mary (Mary Mallon)


B routes of pathogen transmission
B.routes of pathogen transmission microorganisms multiply,release toxin within the body and produce a change in the normal physiology of the body.

  • 1.respiratory infections

    the tiny particles of liquid released into the air form aerosols or droplets

  • 2.wound infectons:in soil and feces of human and animal

  • 3.intestinal infections: contaminate drinking water and food or when used to fertilize crops



acute infection mucous membranes of the infected person or animal and that of healthy person

chronic infection

C.Patterns of infection

Apparent infection

1.apparent infection

When an infection causes pathological changes leading to disease,it is often accompanied by a variety of signs and symptoms

Infectons that come on rapidly,with severe but short-lived effects,are called acute infections

The infection persists several months to several years called chronic infection


  • Inapparent infection: mucous membranes of the infected person or animal and that of healthy personalso called subclinical infection that has no detectable clinical symptoms


local infection mucous membranes of the infected person or animal and that of healthy person

generalized/systemic infection

Localized infection stands for the case that the microbe enters the body and remains confined to a specific tissue


Generalized infection
Generalized infection mucous membranes of the infected person or animal and that of healthy person

  • Bacteremia

  • Definition: a transitory disease in which bacteria present in the blood are usually cleared from the vascular system with no harmful effects.

  • Septicemia

  • Definition: a disease in which the blood serves as a site of bacterial multiplication as well as a means of transfer of the infectious agent from one site to another.


  • Toxemia mucous membranes of the infected person or animal and that of healthy person

  • Definition: the presence of microbial toxins in the blood

  • Pyemia

  • Definition: the presence of pyogenic bacteria in the blood as they are being spread from one site to another in the body


Local lesion mucous membranes of the infected person or animal and that of healthy person

毒素

毒素

毒素

毒素

毒素

毒素

toxin

血液

局部病灶

局部病灶

toxin

毒素

毒素

Defense function↓↓

toxin

special toxic symptom

pathogenic bacterium can grow in blood

Organism is seriously dadamaged, toxic symptom all over the body。

Toxemia

Bacteremia

Septicemia

e.g.tetanus


毒素 mucous membranes of the infected person or animal and that of healthy person

toxin

blood

局部病灶

局部病灶

toxin

毒素

毒素

When Pyosis bacteria cause Septicemia,multiple pyosis focus of infection will happen.e.g. staphylococci aureus

New pyosis focus of infection

Pyosepticemia


Section3 antibacterial immunity of host

Section3 Antibacterial immunity of host mucous membranes of the infected person or animal and that of healthy person


Host resistance mechanisms
Host resistance mechanisms mucous membranes of the infected person or animal and that of healthy person

  • Nonspecific host defenses

  • Anatomical defenses

  • Skin and mucosal membrane

    Mechanical barriers

    Secretions

    Normal flora


  • Blood-brain barrier mucous membranes of the infected person or animal and that of healthy person

  • Placenta barrier

  • Cellular defenses:the reticuloendothelial system

  • Molecular defenses:complements, lysozymes, etc


Innate immunity
Innate immunity mucous membranes of the infected person or animal and that of healthy person

Skin & mucous membranes

Intact skin

Fatty acids sebaceous glands

Mucous membrane of respiratory tract

  • ciliary action

  • traps many microorganisms

    Lysozyme

    Normal flora


Innate immunity1
Innate immunity mucous membranes of the infected person or animal and that of healthy person

Inflammatory response & phagocytosis

(early host responses to bacteria infection)

Bacteria infection→vasoactive factors →

the increased permeability

Chemokines → Neutrophils and macrophages


Host resistance mechanisms1
Host resistance mechanisms mucous membranes of the infected person or animal and that of healthy person

  • Specific host of defenses

  • Humoral immunity: antibody-mediated immunity

  • Cellular immunity: cell-mediated immunity

Inflammatory response & phagocytosis


Host defences mucous membranes of the infected person or animal and that of healthy person


Acquired immunity
Acquired immunity mucous membranes of the infected person or animal and that of healthy person

Humoral immunity

antibody to aggressin

antibody to toxin

Cell-mediated immunity

T cells

lymphokines (IFN- γ)

macrophages


ad