microbio Exam 3

mutualism

both host and microbe coexist and benefit

amensalism

both host and microbe co exist; one is harmed the other unchanged

commensalism

both host and microbe co exist; one benefits the other unchanged

parasitism

microbe in host environment at expense of host

In parasitism microbes may become?

pathogens

Infection

Colonization by microbes that can damage cells or tissues of the body

Symptoms

effects of infection that are apparent to the host, but hard to quantify

Signs

effects of infection that can be measured by physical methods

Disease

infection that produces damage to the body, with or without symptoms

Pathogen

Any microbe that causes disease

Opportunistic pathogens

commensals that can cause disease under certain conditions, where normal barriers of the host are breached or where the host's defenses are compromised

Commensals

start as pathogens but once the host's immune system controls them, they no longer cause disease

Virulence (pathogenicity)

the ability of a pathogen to cause infection and disease

Virulence factors

microbial products are strategies that are used by the pathogen that contribute to virulence

The stages of disease progression

establishment of infection, incubation period, acute period, decline period, convalescence period

During establishment of infection, what is attachment?

adherence to the host's cells

What occurs during establishment of infection?

Colonization and growth of microbe

when does the incubation period occur?

before symptoms manifest

What occurs during the incubation period?

evasion of host immune system, the invasion and/or production of toxic substances

evasion of host immune system

innate immune response

the invasion and or production of toxic substances

damage to the host that manifests in disease (often with symptoms and signs of disease)

how fast is the acute period?

can be rapid and dramatic onset

at what stage of disease progression does morbidity or damage occur?

acute period

What occurs during the acute period?

dissemination in the body, disease signs and symptoms, and transmission

Dissemination in the body

disease spreads to other body parts

Disease signs and symptoms

evident to the host

Prodromal period

mild, nonspecific, and followed by overt illness

Transmission

spread to external environment and or other hosts

What stage of disease progression do chronic infections often not or slowly get to?

decline period

if there is no decline stage…

there is mortality

what occurs during the decline period?

immunity, disease signs and symptoms subside

Immunity

when the hosts adaptive immune system responds

what occurs during the convalescence period?

the host's immune system is fully functional and protective, the host regained strength and returns to normal

What conditions affect host susceptibility?

age, other diseases, nutritional status, stress/lifestyle, antibiotic use, surgery/injury, exposure, vaccination status, and genetic differences

host susceptibility: age

Usually very young and very old people are more susceptible due to lower immune status

Host susceptibility: other diseases

Co infection or prior infection with other pathogens or diseases that affect the defenses of the human body (like HIV and cancer)

host susceptibility: nutritional status

malnutrition affects defenses of the body

Host susceptibility: stress/lifestyle

Emotional or physical stress affects the defenses of the body

Host susceptibility: antibiotic use

affects the normal protective microbiota of the body causing a shift in microbial growth patterns

Host susceptibility: surgery/injury

breach of natural protective barriers

host susceptibility: exposure

increase transmission rate (crowded conditions, poor sanitation, etcetera)

host susceptibility: vaccination status

prior immunization provides more rapid protective immune response upon exposure

Host susceptibility: genetic differences

Host genetic background can make host more or less susceptible to infection (some mutations can make people have HIV resistants)

Koch’s Postulates

A set of four rules that must be satisfied to link a potential pathogen to a particular disease

What are the four postulates (Koch’s) to establish that a particular microbe is the cause of disease?

association, isolation, inoculation, and re isolation

Koch’s Postulates: association

microbe must be found in all cases where symptoms or signs of the disease are evident, while absent in healthy individuals

Koch’s Postulates: isolation

microbe must be isolated from the site of infection and maintained in a pure culture

Koch’s Postulates: inoculation

Microbe must be capable of reproducing the disease when the cultured isolate is inoculated into susceptible hosts

Koch’s Postulates: reisolation

the same microbe must be retrievable from an experimentally inoculated host and cultured again from the experimental infected host

What factors make it difficult to satisfy Koch’s Postulates?

unculturable pathogens, Asymptomatic or subclinical carriers, lack of animal models and host specificity, Poly microbial infections and dysbiosis, and post immunity and variable pathogenicity

Unculturable pathogens make it difficult to satisfy which postulate?

postulate 2

Asymptomatic or subclinical carriers make it difficult to satisfy which postulate?

postulate 1

Lack of animal models and host specificity makes it difficult to satisfy which postulate?

Postulate 3

Polymicrobial infections and dysbiosis make it difficult to satisfy which postulate?

postulates 1, 2, and 3

Host immunity and variable pathogenicity make it difficult to satisfy which postulate?

postulate 3

What are unculturable pathogens?

viruses and prions, and fastidious bacteria

What is an asymptomatic or subclinical carrier?

someone with latent or silent infection

Viruses and prions

cannot grow outside host’s cell or on culture plates

Fastidious bacteria

Have nutrient requirements that are difficult to replicate

Latent or silent infections

not all colonization’s are associated with or lead to disease

Poly microbial diseases

caused by many microbes working together leading to the failure of pinpointing and isolating a single microbe

immune status

Affects severity of infection, enabling opportunistic pathogens

what are modern methods to help satisfy Koch’s Postulates?

specific prevention and treatment, detection, and molecular focus and exposure reduction

What does it mean by specific prevention and treatment?

Vaccinations and antimicrobials/antibiotics

what is the purpose of Vaccinations?

immunization with vaccine targeting disease causing microbe or one or more components of it (liver ruins factors)

what do vaccinations prevent?

disease signs/symptoms

what is the purpose of Antimicrobials/antibiotics?

Antimicrobials target disease causing microbes leading to disease eradication

what does antimicrobial therapy do?

eliminates microbe and symptoms/signs of disease

what is detection?

Use of molecular biology techniques to detect presence of pathogen and tissue of blood samples by a multitude of methods

what are the methods of detection?

immunohistochemistry/immuno-fluorescence microscopy, enzyme-linked immunosorbent assay, and PCR

immunohistochemistry//immuno-fluorescence microscopy

directly detects microbe

Enzyme linked immunosorbent assay (ELISA)

indirectly detects antibodies the host has generated

PCR

indirectly detects pathogen DNA using primers for specific genes encoded by a specific pathogen

what happens when 16 S rRNA gene is used with PCR?

you need to sequence PCR product to confirm microbe identity

Colonization

occupational, growth, and multiplication of microorganisms in the host

What is molecular focus and exposure reduction?

attenuation/mutagenesis, and reduce the exposure to prevent disease and transmission

attenuation/mutagenesis

disrupting or deleting a gene that encodes a putative virulence factor in a virulence train of pathogen (significantly lowers or attenuates its virulence in either eliminates or lowers disease sign/symptoms)

By introducing a gene into a virulent strain with no disease signs or symptoms, what happens to the virulence?

virulence is enhanced and causes disease signs/symptoms

Reduce exposure to prevent disease and transmission means to:

prevention or reduction of exposure to putative pathogen (prevents or lowers disease incident and transmission)

how can we prevent or lower disease incident and transmission?

Improve hygiene, control the microbe carrying vectors via insecticides, reduce exposure to pathogen carriers or natural reservoirs by quarantining infected individuals or carriers

infection

When one organism evades external and some internal defenses, multiplies, and becomes established

Epidemiology

The study of disease transmission within populations

what does epidemiology usually study and address?

Public health problems

what are the sources of human pathogens?

Animals, humans, and non living organisms

What are the routes of entry?

Skin, mucus membranes, placenta, and parenteral

What are virulence factors?

Attachment, colonization, host defense evasion

What are modes of transmission?

Contact vehicle, and vector

What nonliving things can be used as reservoirs?

soil, water, and food can be reservoirs of infection

Why do non living things have microorganisms?

Due to contamination by feces or urine (very common during storms and natural disasters)

Zoonoses (zoonotic disease)

Disease that naturally spread between animal and human hosts

Humans are often the what for zoonotic pathogens?

A dead end host

How does a human acquire zoonoses?

direct contact with animal or its wastes, by eating animals, and by blood sucking arthopod bites (mosquitoes or ticks)

Why are zoonoses difficult to eradicate?

It costs a lot of money and it is hard to remove or contain all animals carrying the pathogens

epizootic Disease

Spread among animal populations

transmission

How a pathogen gets from a reservoir or infected hosts portal of exit to another host portal of entry

What are the two modes of transmission?

direct transmission, indirect transmission

Direct transmission

Transfer immediately from person to person or animal soil to person, requires close or physical proximity

direct transmission: vertical transmission

mother to child across the placenta, during childbirth,h or via breast milk

Direct transmission: aerosol droplets spread

direct contact with airborne droplets of mucus or bodily fluids through close proximity

Indirect transmission

reservoir to host via an intermediate vehicle, surface, particle, or living character