Infection and Disease II Pathogenicity and Infection.

Infection and Disease IIInfection and Disease II

Pathogenicity and InfectionPathogenicity and Infection

ELISAELISA -- Enzyme-Linked Immunosorbent -- Enzyme-Linked Immunosorbent

AssayAssay

Direct ELISADirect ELISA -- detects __________ (i.e. virus, -- detects __________ (i.e. virus,

bacterium)bacterium)

Indirect ELISAIndirect ELISA -- detects ______________ to -- detects ______________ to

the antigen. HIV ELISA is an example.the antigen. HIV ELISA is an example.

Antibody-based detection methodsAntibody-based detection methods

HIV Indirect ELISA animationHIV Indirect ELISA animation

http://www.biology.http://www.biology.arizonaarizona..eduedu/immunology/activities//immunology/activities/elisaelisa/technique.html?/technique.html?

Pathogenicity and InfectionPathogenicity and Infection

• Non-specific host defensesNon-specific host defenses

• Entry of the pathogen into the hostEntry of the pathogen into the host

• Colonization and growthColonization and growth

• VirulenceVirulence

• ToxinsToxins

Some termsSome terms

PathogenPathogen (or ‘true pathogen’) -- can cause infection and (or ‘true pathogen’) -- can cause infection and

disease in a _____________ hostdisease in a _____________ host

Opportunistic pathogenOpportunistic pathogen -- only pathogenic to non- -- only pathogenic to non-

______________ individuals or when introduced into a ______________ individuals or when introduced into a

normally ___________ part of the bodynormally ___________ part of the body

VirulenceVirulence -- degree of __________________ of a parasite -- degree of __________________ of a parasite

Virulence factorsVirulence factors -- _________________ of the pathogen -- _________________ of the pathogen

which allow it to successfully invade and colonize a hostwhich allow it to successfully invade and colonize a host

Non-specific host defensesNon-specific host defenses

• Anatomical defensesAnatomical defenses

• Effect of age, stress, and diet on Effect of age, stress, and diet on susceptibilitysusceptibility

Physical Barriers and Anatomical DefensesPhysical Barriers and Anatomical Defenses

Compound in Saliva Protects Against Compound in Saliva Protects Against E. coliE. coli

Scientists from the University of Calgary have identified aScientists from the University of Calgary have identified a protein produced by protein produced by salivary glands that, when administered orally, can significantly reduce salivary glands that, when administered orally, can significantly reduce diarrhea and weight loss associated with diarrhea and weight loss associated with Escherichia coliEscherichia coli infection infection. They . They report their findings in the October 1998 issue of the journal report their findings in the October 1998 issue of the journal Infection and Infection and ImmunityImmunity..

In the study, the researchers investigated the ability of the protein, known as In the study, the researchers investigated the ability of the protein, known as epidermal growth factor (EGF), to protect rabbits from the effects of an epidermal growth factor (EGF), to protect rabbits from the effects of an experimental experimental E. coliE. coli infection. The researchers found that daily treatment with infection. The researchers found that daily treatment with EGF prevented the occurrence of diarrhea and weight loss. They also found EGF prevented the occurrence of diarrhea and weight loss. They also found lower colonization rates in the intestines of treated rabbits.lower colonization rates in the intestines of treated rabbits.

"The findings demonstrate that oral EGF administration inhibits the production of "The findings demonstrate that oral EGF administration inhibits the production of diarrhea and reduction in weight gain seen in weanling rabbits infected with diarrhea and reduction in weight gain seen in weanling rabbits infected with attaching-effacing attaching-effacing E. coliE. coli, " say the researchers. "These observations suggest a , " say the researchers. "These observations suggest a role for EGF in protecting the gastrointestinal tract from colonization from role for EGF in protecting the gastrointestinal tract from colonization from bacterial pathogens.”bacterial pathogens.”

(A. Buret, M.E. Olson, D. Grant Gall, and J.A. Hardin. 1998. Effects of orally administered epidermal growth factor on (A. Buret, M.E. Olson, D. Grant Gall, and J.A. Hardin. 1998. Effects of orally administered epidermal growth factor on enteropathogenic Escherichia coli infection in rabbits. Infection and Immunity. 66:4917-4923.)enteropathogenic Escherichia coli infection in rabbits. Infection and Immunity. 66:4917-4923.)

Susceptibility to Infectious DiseaseSusceptibility to Infectious Disease

AgeAge -- ___________ and ____________ more susceptible. Why? -- ___________ and ____________ more susceptible. Why? infants -- undeveloped normal flora,undeveloped immune systeminfants -- undeveloped normal flora,undeveloped immune system elderly -- immune response declines, anatomical changeselderly -- immune response declines, anatomical changes

StressStress -- in rats: fatigue, exertion, poor diet, dehydration, drastic -- in rats: fatigue, exertion, poor diet, dehydration, drastic climatic changes increase_________________ climatic changes increase_________________ and___________________ of infections. and___________________ of infections. Hormone imbalance plays important role.Hormone imbalance plays important role.

DietDiet -- famine and infectious disease correlated (e.g. cholera). -- famine and infectious disease correlated (e.g. cholera). OvereatingOvereating may have also an effect. may have also an effect. Key may be disruption of __________________ ______________Key may be disruption of __________________ ______________ Not eating a particular substance needed by normal flora can have effect Not eating a particular substance needed by normal flora can have effect

(e.g. a vitamin)(e.g. a vitamin)

How they get inHow they get in

Tissue specificity (of the pathogen) is a serious barrier to the Tissue specificity (of the pathogen) is a serious barrier to the entry of most microorganisms (more on this later)entry of most microorganisms (more on this later)

Discussed in viruses, also true of other pathogenic Discussed in viruses, also true of other pathogenic microorganisms: often (usually) only infect specific tissues and microorganisms: often (usually) only infect specific tissues and cell types.cell types.

Notable (mainly bacterial) exceptions exist, e.g. Notable (mainly bacterial) exceptions exist, e.g. Streptococcus Streptococcus pyogenespyogenes and and Staphylococcus aureus.Staphylococcus aureus.

So, how So, how dodo microorganisms “get into” (colonize and establish microorganisms “get into” (colonize and establish in) the host??in) the host?? In the first place some of them don’t have to “get in” to be In the first place some of them don’t have to “get in” to be

pathogenic… How can this be?pathogenic… How can this be?

They might already be there (in the normal flora or as They might already be there (in the normal flora or as latent latent infectionsinfections) Called infection from an ) Called infection from an ““endogenousendogenous” ” sourcesource

Exogenous infectionsExogenous infections

SkinSkin: portals are bites, digestive : portals are bites, digestive enzymes, needles, surgery, enzymes, needles, surgery, wounds, and catheters. wounds, and catheters.

High speed photo of unstifled sneezeHigh speed photo of unstifled sneeze

Respiratory tractRespiratory tract: location (upper or : location (upper or lower) somewhat dependent on size, lower) somewhat dependent on size, attachment. attachment. Portal of entry to the Portal of entry to the greatest ________________ of greatest ________________ of pathogenspathogens..

GI tractGI tract: : ________ production ________ production (e.g. (e.g. Staph. aureus, Clostridium Staph. aureus, Clostridium perfringensperfringens) or directly through ) or directly through intestinal (and stomach, in the case intestinal (and stomach, in the case of of HelicobacterHelicobacter) epithelium) epithelium

Exogenous Infectious AgentsExogenous Infectious Agents

• Entering via the Entering via the skinskin:: Staph. aureusStaph. aureus; ; Strep. pyogenesStrep. pyogenes; herpes ; herpes

simplex type I, HIV, and various viruses; assorted fungi; simplex type I, HIV, and various viruses; assorted fungi; ClostridiumClostridium tetanitetani and and C. perfringensC. perfringens; ; Haemophilus aegyptumHaemophilus aegyptum, , Acanthamoeba Acanthamoeba and assorted protozoa, etc.and assorted protozoa, etc.

• Entering through the Entering through the GI tractGI tract:: various Gram-negative rods various Gram-negative rods

((Salmonella, Campylobacter, E. coli, Shigella dysenterae, Vibrio Salmonella, Campylobacter, E. coli, Shigella dysenterae, Vibrio choleraecholerae, etc.); assorted viruses (poliovirus, hepatitis A, rotaviruses), etc.); assorted viruses (poliovirus, hepatitis A, rotaviruses)

• Entering via the Entering via the respiratory tractrespiratory tract:: Group A Group A Strep. pyogenesStrep. pyogenes; ;

meningitis-causing bacteria such as meningitis-causing bacteria such as Neisseria meningitidisNeisseria meningitidis, and , and Haemophilus influenzaeHaemophilus influenzae; ; Corynebacterium diphtheriaeCorynebacterium diphtheriae; ; Bordetella Bordetella pertussispertussis; pneumonia-causing agents like ; pneumonia-causing agents like Strep. pneumoniaeStrep. pneumoniae and and various viruses and fungi; various viruses and fungi; Mycobacterium tuberculosisMycobacterium tuberculosis; viruses of ; viruses of chickenpox, measles, mumps, rubella, influenza, and common cold.chickenpox, measles, mumps, rubella, influenza, and common cold.

Exogenous infections (cont.)Exogenous infections (cont.)

UrogenitalUrogenital: Enter through skin or mucosa of penis, : Enter through skin or mucosa of penis,

vagina, urethra, etc. Syphilis vagina, urethra, etc. Syphilis (Treponema (Treponema

pallidum),pallidum), gonorrhea gonorrhea (Neisseria gonorrhoeae),(Neisseria gonorrhoeae),

genital warts, chlamydia, herpes simplex Type II, genital warts, chlamydia, herpes simplex Type II,

HIV, etc.HIV, etc.

Birth-related infectionsBirth-related infections: Placental (e.g. syphilis) or : Placental (e.g. syphilis) or

during birth: STORCH (syphilis, toxoplasmosis, during birth: STORCH (syphilis, toxoplasmosis,

other [HIV, hepatitis B, chlamydia], rubella, other [HIV, hepatitis B, chlamydia], rubella,

cytomegalovirus, herpes simplex II virus)cytomegalovirus, herpes simplex II virus)

Adherence, colonization, invasion, growth, diseaseAdherence, colonization, invasion, growth, disease

AdherenceAdherence

Fimbriae (non-sex pili) of Fimbriae (non-sex pili) of enteropathogenicenteropathogenic E. coliE. coli

http://www.bc.ic.ac.uk/mcbap.htmlhttp://www.bc.ic.ac.uk/mcbap.html

Enteropathogenic strains are able to colonize the ___________ Enteropathogenic strains are able to colonize the ___________

intestine and cause ________________ by expressing specific intestine and cause ________________ by expressing specific

colonization factor antigenscolonization factor antigens (proteins) on their fimbriae (proteins) on their fimbriae

Intestinal Infection by Enteropathogenic bacteria

Intestinal Infection by Enteropathogenic bacteria

Enteropathogenic Enteropathogenic E. coli infection animationE. coli infection animation

Salmonella invasion animationSalmonella invasion animation

(Howard Hughes Institute web site:(Howard Hughes Institute web site:

http://www.hhmi.org/grants/lectures/biointeractive/animations.html)http://www.hhmi.org/grants/lectures/biointeractive/animations.html)

Pathogens must first become established at site of infection. _____________ must be Pathogens must first become established at site of infection. _____________ must be compatible with the microorganism.compatible with the microorganism.

An infecting microorganism can’t adhere to _______ cells or hosts. An infecting microorganism can’t adhere to _______ cells or hosts.

Tissue and host specificity as factors in infection

Tissue and host specificity as factors in infection

Disease Tissue infected OrganismDiphtheria Throat epithelium Corynebacterium

diphtheriaeGonorrhea Urogenital

epitheliumNeisseriagonorrhoeae

Cholera Small intestineepithelium

Vibrio cholerae

Dental caries Oral epithelium Strpetococcusmutans, S.sobrinus, S.sanguis, S. mitis

Spontaneous abortion(cattle)

Placenta Brucella abortus

AIDS T helperlymphocytes

HIV

Malaria Blood (erythrocytes) Plasmodium sp.

Some cells are pathogenic due to the toxins Some cells are pathogenic due to the toxins

they produce (e.g. they produce (e.g. ClostridiaClostridia) but most ) but most

need to actually ___________ and need to actually ___________ and

______________ in host tissues in order ______________ in host tissues in order

to cause disease.to cause disease.

Colonization, Growth, and VirulenceColonization, Growth, and VirulenceColonizationColonization -- ____________________ of a -- ____________________ of a

microorganism after it has attached to host tissues microorganism after it has attached to host tissues or other surfacesor other surfacesThe initial inoculum of cells is rarely sufficient to cause The initial inoculum of cells is rarely sufficient to cause

disease; needs to ____________.disease; needs to ____________.

Must therefore find appropriate nutrients and Must therefore find appropriate nutrients and environment. This not always as easy as it appears (e.g. environment. This not always as easy as it appears (e.g. iron)iron)

Virulence factorVirulence factor -- any characteristic of a pathogen -- any characteristic of a pathogen that enables it to establish itself and cause disease. that enables it to establish itself and cause disease. These are often extracellular enzymes such as These are often extracellular enzymes such as hemolysinhemolysin, ,

hyaluronidasehyaluronidase, , collegenasecollegenase,, and and coagulasecoagulase. The first 3 . The first 3 of these allow for spread (and nutrition, to some of these allow for spread (and nutrition, to some extent), the 4th promotes localization and, probably, extent), the 4th promotes localization and, probably, protection.protection.

Summary of virulence factors important in Salmonella pathogenesis

Summary of virulence factors important in Salmonella pathogenesis

Some pathogens are much more virulent than others

Some pathogens are much more virulent than others

Infectious Dose -- minimum number of agents (cells, viruses) needed to cause disease

Infectious Dose -- minimum number of agents (cells, viruses) needed to cause disease

Varies from 1 Varies from 1 RickettsiaRickettsia cell in Q fever to 10 cells in cell in Q fever to 10 cells in tuberculosis to 10tuberculosis to 1033 cells in gonorrhea, 10 cells in gonorrhea, 104 4 cells in cells in typhoid, and 10typhoid, and 1099 cells in cholera. cells in cholera.

Smaller infectious dose = more _________ pathogenSmaller infectious dose = more _________ pathogen

If number of cells < infectious dose no infectionIf number of cells < infectious dose no infection

If number of cells >> inf. dose more rapid __________If number of cells >> inf. dose more rapid __________

ToxinsToxins

Exotoxin Exotoxin -- toxin ___________ into tissue-- toxin ___________ into tissue

Diphtheria toxinDiphtheria toxin -- extremely potent (one molecule will kill a -- extremely potent (one molecule will kill a

cell). Disrupts _____________ synthesis. Caused by cell). Disrupts _____________ synthesis. Caused by

lysogenic phage in lysogenic phage in Corynebacterium diphtheriae.Corynebacterium diphtheriae.

Tetanus and botulism toxinsTetanus and botulism toxins -- Causal organisms ( -- Causal organisms (Clostridium Clostridium

tetanitetani and and C. botulinumC. botulinum) don’t generally ______________ ) don’t generally ______________

very much in infected tissues but instead release potent very much in infected tissues but instead release potent

neurotoxins. neurotoxins.

Action of Tetanus NeurotoxinAction of Tetanus Neurotoxin

Tetanus causes irreversible muscle _________________ (‘spastic paralysis’ or ‘lockjaw’)Tetanus causes irreversible muscle _________________ (‘spastic paralysis’ or ‘lockjaw’)

Action of Botulinum NeurotoxinAction of Botulinum Neurotoxin

Botulinum toxin, the most poisonous substance known, causes Botulinum toxin, the most poisonous substance known, causes irreversible muscle _________________ (‘flaccid paralysis’).irreversible muscle _________________ (‘flaccid paralysis’).

Toxins (cont.)Toxins (cont.)EndotoxinEndotoxin -- toxin released only upon cell ________ and lysis -- toxin released only upon cell ________ and lysis

These are These are lipopolysaccharideslipopolysaccharides and thus are found only in Gram-negative and thus are found only in Gram-negative

organisms. Most studied in organisms. Most studied in Salmonella, E. coli, Salmonella, E. coli, and and Shigella.Shigella.

Toxins (cont.)Toxins (cont.)

EnterotoxinEnterotoxin -- toxin that acts specifically on -- toxin that acts specifically on the ______________. the ______________.

Enterotoxins are found in Enterotoxins are found in S. aureus, S. aureus,

enteropathogenic enteropathogenic E. coli, Clostridium E. coli, Clostridium

perfringens, Salmonella spp., etc.perfringens, Salmonella spp., etc.

Most studied: cholera toxin from Most studied: cholera toxin from Vibrio Vibrio choleraecholerae

Action of cholera enterotoxinAction of cholera enterotoxin

Action of cholera enterotoxin (cont.)Action of cholera enterotoxin (cont.)

Patterns of InfectionPatterns of Infection