Lecture 2 Flashcards
what is a saprophyte
an organism that lives on dead or decaying matter can be plant, fungus, or microorganism.
Types of symbiosis (3)
Mutualism: both benefit Commensalism: they are neutral to eachother, neither damaging the other Parasitism: Only benefits the parasite/microorganism.
Whats the approx ratio of human body cells to the number of microbes it hosts?
1:10 located on skin, mucous membranes, gut, vagina
What are the benefits of commensual bacteria for humans and for the bacteria
Bacteria: Get shelter and food and a stable environment Do not penetrate or colonise into human tissues except for rarely through a wound or disease For the human: 1) Commensual bacteria prevent colonisation by harmful microbes, in a couple of ways: - occupy the surface and cover cell receptors the harmful bacteria would like to reach - Produce antimicrobial compounds, such as lactic acid in the vagina 2) Aid in digestion: Vitamin K and B12
Classes of parasitism (3)
Obligate : Are always found in defined host or hosts, are always pathogenic and never in normal flora Facultative : An organism which is often or usuallu parasitic but is not completely dependent on the host for completion of its life cycle, and may survive outside of it. May be a normal member of the flora, and may be pathogenic depending on the state of the host and microbe. examples: fungi or plant species parasitising other plants if the conditions are right. Opportunistic: An organism that is normally not parasitic and grows/lives in the environment of the host, but can take advantage and parasitize the host in certain conditions (ie immunosuppressed patients)
Predisposing factors for facultative or opportunistic infections
Stress. (physical or mental –> immune suppression) Wounds, burns Chronic debilitating conditions: Diabetes, alchol or drug abuse, malnutrition, tumors and immune suppression or chemotherapy Urinary tract obstructions
Medical related risk factors for generating opportunistic/facultative infecitons
Medical interventions: (Iatrogenic diseases) Antibiotics depleting normal GI flora Surgery wounds Prosthetics, catheters and Biofilm buildup.
Risk factors for opportunistic microbes What types of infections does a T-cel ldeficiency increase? B-cell deficiency?
Immune deficiencies of many different kinds. Weakened populations: Newborns, pregnant women, elderly T-cell deficiency -> increased intracellular pathogens, protozoa, helmiths B-cell deficiency -> increased bacterial, fungi, protozoa Acquired immune deficiencies: Immunosuppressive drugs, Radiation depletion of immune cells Tumors/Leukemia Viruses/infections of immune cells
Define Pathogenicity
The ability of the whole population of a microbe species to elecit disease in a given host or range of hosts
Is a genetically defined, qulaitative trait, ie. Is this microorganism capable of infecting this host species? yes/no
Define Virulence
A quantitative trait, defining the extent of disease or pathology caused by the microorganism in the host.
It is usually correlated with the ability of the microorganism to multiply within the host
Define the terms ID50 DL50 TCID50
What are these terms used for?
These terms are used to measure virulence.
ID50 Infective Dose: The number of microbes required under standard circumstances to induce disease in 50% of hosts.
DL50 Dosis Lethalis: Number that causes death in 50% of hosts
TCID50 Tissue Culture Infecting Dose: Quantity that damages 50% of tissue cultures.
Lower values indicate higher virulence
What is the structure of LPS?
Lipid A: A disaccharide diphosphate, each separate glucose, O- and N-acetylated with a different pair of fatty acids. 6 total FA chains.
the Core polysaccharide
and the repeated O-antigen, a 4-monosaccharide unit that is repeated 40 times.
What is Horizontal Transmission of infection and its categories?
What is Vertical transmission?
Horizontal from within one genration, as opposed to vertical, which is down the generation line, mother to child. Transplacental
Means of spread:
Direct contact
Indirect contact: by contaminated objects
Vehicles:
- Air, aerosolized pathogen in sneezes, coughs, breath
- Water or food sources
- Vectors: blood sucking insects
- Vertebrate reservoirs: other humans or animals which are constantly harboring the disease, ex. rats or dogs/cats.
Iatrogenic infections
direct transcutaneous (also called percutaenous) transmission by contaminated hospital/medical equipment.
What does the Incubation Time of a pathogen indicate?
The period of time from the moment of infection to the onset of symptoms.
What can be one affect of symptomless childhood infections on the patient as an adult (according to our lectures very important…)?
They may obtain lifelong immunity or cross-immunity.
examples: toxoplasmosis and HSV-1/HSV-2
What is the antigen profile of Cytotoxic vs. Helper T-cells?
What MHC classes do each of them interact with?
T-helper cells: CD4+ interact with MHC-II
-Helper cells bind MHC-II-bound antigen complexes, MHC-II is only expressed by APCs, and presents exogenous antigens, things that have been eaten by the macrophages and are bound by the MHC-2 receptor from within endosomes, and are being presented to ativate the immune system by the T-helpers.
Cytotoxic T cells: CD8+ with MHC-I
-Cytotoxic T cells bind MHC-1 bound antigen complexes. MHC-1 is expressed by every nucleated cell in the body. MHC-1 presents antigens from intracellularly derived proteins that have been degraded by the proteasome. They are presented by MHC-1 to recruit CD8+ cells signalling that “I’m infected, or I’m cancerous,” and needing Cytotoxic cells to kill them.
