What is another name for the human micro biome?
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
-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?
-something that can be detected or measured by someone else, what the doctor sees
-fever, heart rate, respiratory rate
-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
-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
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
How does a host protect innately at sites where bacteria can enter?
-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?
- physical barrier, complement pathway, inflammation
- humoral, cell mediated
How do pathogens get around host defense mechanism?
-avoid the immune response
-hide from 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
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?
-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
-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?
Explain how the delayed immune response could affect disease outcomes?
explain the different courses of infection?