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What is another name for the human micro biome?

Normal Flora


What is the human micro biome? Functions?

-Normal population of organisms that populate our body, mostly bacteria, some yeast and fungi

-educates immune system, local and systemic

-helps digestion of food and synthesis of vitamins

-protects against harmful microbes

-inhibit establishment of pathogens (colonization of resistance)


Where do bacteria accumulate on our bodies? What part of our bodies is sterile? What happens if normal body b bacteria gain access to sterile sites?

-nasopharynx (nasal, oral)- S aureus

-skin- S aureus

-gastrointestinal tract- E coli

-urogenital tract

-vagina- strep, fragillis

-inner organs are sterile

-can become pathogens if gain access to sterile sites, or become immunocompromised


Definition of infection? Example?

-a microbe colonizes and grows in or on a host where it isn't normally found

-ex. streptococcus pneumonia colonizes the nasopharynx or from another infected individual can gain access to the lung


What is an infectious disease? characteristics?

-an illness caused by the presence of a pathogenic microorganism growing in or on an infected host


-can cause mortality, morbidity


How is a particular disease defined?






-objective evidence

-something that can be detected or measured by someone else, what the doctor sees

-fever, heart rate, respiratory rate



-subjective evidence

-something that must be described be the one suffering with the disease

-what the patient experiences



the complete signs and symptoms associated with a specific disease


Signs and symptoms of pneumonia?

-chest pain with difficulty breathing

-high fever, shaking, chills

-excessive sweating


-cough with phlegm that persists or gets worse



an organism that has the capacity to cause disease



the cause of a disease or condition (virus, prion, bacteria, fungi, parasite)


T/F Viruses and prions are not cells. Why?


-cannot grow on their own, have to infect a cell

-prions-infectious proteins


What type of cells are fungi and parasites (protozoa and helminths)?

eukaryotic cells- have membrane bound organelles


Why are fungi and parasites harder to treat?

they are eukaryotic cells, so they are similar to human cells


What type of cells are bacteria?



Why are bacteria easier to treat?

they are different from human cells, they do not have membrane organelles, so antibiotics can destroy them and not hurt our cells


Points about microbes and disease?

-a single microbe may cause many diseases (MRSA)

-multiple microbes may cause the same disease (pneumonia)

-many microbes cause a range of illness, asymptomatic to severe disease, host factors play a role in determining severity

-infections can be endogenous or exogenous


Infections can be endogenous or exogenous. What is the difference?

-endogenous- already found in person, inside source

-exogenous- caused by another person or thing, outside source


What is the host objective when a pathogen invades? The pathogen causing a disease depends in part on what?

-clear the pathogen

-prevent dissemination- deeper level

-prevent future infections

- adaptive, innate immunity

-how rapidly the immune response can eliminate the microbe


What is the goal of the immune response to a pathogen?

-create a defense against pathogens

-preserve a symbiotic relationship with resident microbes (microbiota)


What is the pathogen objective when it invades a host? How does the pathogen avoid the immune response?

-avoid the host immune response long enough to be transmitted to a new host

-pathogens constantly evolve to escape immune response

-ganarea- keeps evolving, body can't attack


How do pathogens enter and leave a host?

-exposure to environment


-respiratory tract

-gastrointestinal tract

-urogenital tract


How does a host protect innately at sites where bacteria can enter?

-physical barrier

-mucus/mucociliary transport

-acid, mucus, enzymes, peristalsis -voiding


What are the modes of transmission of a disease? How are they controlled?

-respiratory or salivary spread- not readily controlled

-fecal oral spread- controllable by public health measures

-venereal spread- difficult to control due to social factors

-vector- bite(malaria, sandfly fever, typhus)

-vertebrate reservoir- brucellosis, rabies, Q fever, salmonellosis

-vector vertebrate reservoir- plague, trypanosomiasis, yellow fever


How do pathogens cause disease?

-direct damage at site of microbial replication(induce cell death)

-express toxins with local or systemic effects

-indirect damage due to activation of the immune response (immune mediated pathology-sepsis)

-induce autoimmune response (disrupt host tolerance to self)

-immunosuppress host-susceptible to opportunistic pathogens -trigger oncogenesis


How does the host combat pathogens?

-innate immunity

- physical barrier, complement pathway, inflammation

-adaptive immunity

- humoral, cell mediated


How do pathogens get around host defense mechanism?


-avoid the immune response

-hide from it

-escape it

-neutralize it

-manipulate it

-microbes have evolved many ways


Factors that influence the manifestation of disease?

-transmission determines site of entry

-inoculum size influences severity

-tissue tropism determines site of pathology

-microbial virulence factors influence the severity of the illness, pathology, ability of immune response to limit infection

-age, susceptibility


Host factors influencing disease?

-immune status- prior immunity, compromised or non compromised immune system

-general health of person

- nutrition status, comorbidities




Kochs postulates (4)?

1. microorganism is present in all cases of the disease, but not in healthy organisms

2. microorganism must be isolated from a diseased organism and grown in pure culture

3. cultured microorganism should cause disease when introduced to naive host

4. same microorganism must be re-isolated from inoculated, diseased experimental host


Exceptions to Kochs postulates?

-asymptomatic carriers

-some organisms can't be isolated and grown in pure culture

-can be identified by molecular methods, immunohistochemistry, serology

-not all infected hosts will develop disease


Revised postulates (7)?

1. a nucleic acid sequence belonging to a putative pathogen should be present in most cases of an infectious disease

2. fewer or no copies of pathogen associated nucleic acid sequences should occur in hosts or tissues without disease

3. with resolution of disease, the copy number of pathogen associated nucleic acid sequences should decrease or become undetectable- clinical relapse the opposite should occur

4. when sequence copy number correlates with severity of disease, the sequence disease association is stronger

5. the nature of the microorganism inferred from the available sequence should be consistent with the known biological characteristics of that group of organisms

6. microbial sequences should be demonstrated, at a cellular level, in areas of tissue pathology and where microorganisms are known or presumed to be located

7. sequence based evidence for microbial causation should be reproducible


How many new diseases have been recognized since 1940? How many are from zoonotic origin? Most have been recognized since when?

-400 new infectious diseases

-60% zoo

-most since 1980


What is the driving forces behind new discoveries in pathology?

-the need to look beyond genetics and other environmental factors (stress, diet, smoking)

-development of polymerase chain reaction (amplify small genes, identify disease)

-revolutionary findings of warren and marshall in 1983 (helicobacter pylori associated with gastric ulcers)

-inflammation and its triggers as key components to pathogenesis


What causes chronic neurological conditions? How long does it take?

-caused by viruses, virus like agents, intracellular bacteria, fungi, protozoa

-long incubation period followed by slow development of symptoms and a progressive fatal course


Why is the central nervous system more susceptible with aging?

1. diminished functioning of the blood brain barrier and cellular immune mechanisms - infectious agents enter and hide from detection

2. transfer can occur from peripheral nerves into CNS (HSV1)

3. neurons become damaged by oxidative stress and impaired energy production

4. pathways by which neurotrophic factors protect nerve cells may function less efficiently -innate immune- strong whole life -adaptive immune- diminishes over time


What are the possible outcomes of disease?

see picture


Explain how the delayed immune response could affect disease outcomes?

explain picture


explain the different courses of infection?

see picture