Pathogenesis Flashcards
Define microbiota
Sum of external and internal microbes in the body
Define microbiomes
sum of microbes genomes
Define gnotobiology
raising mammals under germ-free environments or under controlled environments where only certain microorganisms are present
What are the 4 purposes of gnotobiology?
1- To control the environment in which a multicellular organism develops
Scientists can create a germ-free (sterile) environment to see how an organism grows without any microbes.
This helps understand which microorganisms are necessary for proper development.
2- Researchers often use animals (like mice) that are genetically modified and germ-free to study specific genes.
This helps them see how genes and microbes interact in health and disease.
3- The immune system develops by interacting with microbes. Without microbes, it behaves differently.
Studying germ-free animals helps scientists understand how the immune system works and what role microbes play.
4- Some diseases, including infections and even cancer, are linked to microbes.
By studying organisms without microbes and adding specific ones, researchers can figure out how microbes contribute to disease.
Define disease
Dysfunction of organs, cells or metabolic pathways in the body
Define Health
Optimal state of the body
All organs and their functions are in perfect condition as they are supposed to be in accordance of genetics, physiology and biochemistry of a given organism
Define pathogenesis
Set of actual mechanisms by which etiological factor causes a disease
(pathogenesis is a broad term covering diff types of diseases not only infectious ones)
Its important for development of direct methods for curing a disease
Define epidemiology
study of occurrence, distribution and control of diseases in population
What are 3 reasons for biological dysfunctions?
1- Genetic
2- Environmental (further subdivided into:
chemical and physical factors
microorganisms
higher organisms
3- Physiological
Define parasitic association
One organism lives and benefits for the expense of another
e.g. measles, typhoid
Viral infections are always parasiti
Define Symbiotic association?
Both organisms benefit from each other
e.g. production of some vitamins (B1 and B12 by bacteria)
Define commensal association?
One organism benefits while the other is not harmed
e.g commensal flora
Parasitic and commensal microoragnisms may cause disease under certain circumstances. What are they called?
Microbial diseases
Define host and pathogen
Microorganism causing a disease is called pathogen.
An organism on which the pathogen lives and causes disease is called the host
Define true pathogens
These are pathogenic microorganisms.
These overcome host defences and cause disease easily
E.g. Bacteria = Clostridium botulinum , mycobacterium tuberculosis
Virsues: HIV, Hepatitis
Define the term opportunistic microorganisms
(usually commensal - these are not harmful unless the immunity is weakened by genetics or any other factors)
These cause disease in hosts with reduced defensive capacity (e.g. decline of immune system)
E.g Bacteria = Staphlyococcus species
What are favourtite conditions in host for opportunistic pathogens
Malnutrition
Recurrent infections
Chemotherapy, antibiotic treatment
Genetic predisposition
Chronic ilnesses (HIV) or conditions (depression)
How do viruses and bacteria cause disease in hosts
Viruses cause diseases as intracelular parasites replicating themselves for the expense of host cells.
Bacteria cause diseases usually via interactions with the surface of host cells (rarely as intracellular parasites)
Diff between parasitic, symbiositic and commensal association?
Parasitic- one organism benefits while the other is harmed
Symbiois- Both benefit from each other
Commensal- one organism benefits while the other is not harmed
Define commensal flora?
These microorganisms that naturally live in or on our bodies. There are around 2.72 times 10 to the power of 13 microbes in human cells.
Its been shown that bacteria in our body are not evenly spread. Instead they form, islands of colonies in specific areas.
Skin microbiota include:
staphylococcus, Candida albicans
Intestinal microbita include:
E. coli
How do fungi and protozoa cause diease?
Fungi are free living organisms, they do not require a host to survive and reproduce.
Their pathogenesis involves vegetative (active, grwoing form of fungus) cells and spores.
Human parasites are not virulent and often do not replicate in the host, instead they have complex life cycles.
Disease severity depends on infecting dose e.g. more parasites= worse symptoms.
These cause infections that can last months- years.
Where is archea found and what does it cause?
Methane producing achea were found in GIT, vagina and oral cavity but they were not shown to be pathogenic. However, recent research has shown the role of arcchea in endodontic diseases
Define infection
Colonisation of a host by a pathogen
Includes entry, local growth and further spread of pathogen in the host
Define incubation period
The time between exposure to a pathogen and appearance of the symptoms
