Microbe-host interactions: Microbiota and pathogens Flashcards
1
Q
Chemical agents
A
- Disinfection on inanimate objects and antiseptic for human tissue
- Only few chemicalsagen achieve sterility
2
Q
Factors that influence efficacy
A
- Kind of organism
- Degree of contamination
- Time of exposure
- Nature of the material treated
- Concentration of disinfectant
3
Q
Antimicrobial chemotherapy
A
- Administration of specific drugs to treat disease selective toxicity againt pathogen
4
Q
Antibiotics
A
Bacterial infection
5
Q
Selectivity
A
- Take advantage of difference between the structure of bacterial cell
- Concider gram positive and negativ e
- Diffrent spectrum activity
6
Q
Symbiosis
A
Close interaction between two organisms of different species
7
Q
Three symbiotic relationships:
A
- Mutualism
- Commensalism
- Parasitism
8
Q
Mutualism
A
- Benefit to the bacteria - place to eat, survive and multiply
- Benefits to the human - Bacteria aid digestion, breaking down food that the host cannot normally digest and producing vitamins
9
Q
Commensalism
A
- Benefit to the bacteria - Acquire nutrients consuming dead skin and a place to live and grow
- Commensal bacteria may become pathogenic and cause disease
10
Q
Parasitism
A
- One partner, the pathogen, harms the host, causing infectious disease
- Benefit to the virus Virus takes advantage of the translational machinery of the cell to replicate
- Harm for the human cells - Viral infections lead to the death of the cells and tissue damage
11
Q
Microbiota
A
- All the microorganisms that live in and on an organism
- 1-3% total body mass
- Generally non-pathogenic
- Symbiotic with host
12
Q
Early Colonization
A
- Developing at birth
- Exposure to microbes from the mother’s birth canal
- Fementate the sugars in breast milk provide calories for baby
- Caesarean delivery provides microbe exposure from
initial caretakers
13
Q
Bifidobacteria
A
Can ferment sugars found in human breast milk provides the infant with calories and lowers the gut pH, limiting growth of pathogens
14
Q
Composition of microbiota
A
- Not static
- It reach a adult-like composition by age
3 - Stable in adult ages without any major physical or lifestyle changes
- Variable from person to person and at different sites within a person
15
Q
Microbiota body sites
A
- Nutrients
- Physical and chemical factors
- Host defenses
- Mechanical factors
16
Q
Microbiota functions
A
- Microbiota functions - short fatty acid chains
- Synthesise and excrete vitamins
- Prevent colonisation by pathogens - competitive exclusion and production and stimulationof antimicrobial molecules
- Stimulate the development of certain tissues
- Immune system stimulation/maturation
- Regulate inflammation
- Modulate and affect the central nervous system
17
Q
Dysbiosis
A
Refers to an imbalance of microbial species and a reduction in microbial diversity within certain bodily
microbiomes
18
Q
Causes of Dysbiosis
A
- Dietary changes
- Antibiotic use
- Psychological
- Physical stress
19
Q
What can Dysbiosis lead to
A
- Can lead to infammation
20
Q
Opportunistic infections
A
- Infection caused by commensals do not cause generally disease in a healthy host but in some circumstances can become opportunistic pathogen
21
Q
How is Dysbiosis opportunistic
A
Altered microbiota can outgrow
22
Q
Probiotics
A
- Live microoganisms that restore the normal balance of microbiota
- Beneficial functions, conferring a health benefit
to the host
23
Q
Prebiotics
A
- Compound(s) added to enhance the colonization and positive health benefits of probiotic microbes
24
Q
Synbiotics
A
- Foods or supplements that include both a prebiotic and a probiotic
25
Pathogen
Any organism that causes disease
26
Opportunistic pathogen
- May be part of normal microbiota and causes disease when the host is immunocompromised or when they have chance to outgrowth
27
Pathogenicity
Ability of a pathogen to cause disease
28
Virulence
- Degree of harm (pathogenicity) inflicted on its host
29
Steps in pathogenesis of bacterial infections
- Entry of pathogens into the body via transmission routes
- Attachment of the pathogen to some tissues
- Multiplication
- Invasion/spread of the pathogen
- Evasion if the host defences/immunity
- Damage to the host tissue
30
Portal of entry
- Skin, respiratory, gastrointestinal, urogenital
systems, or conjunctiva of eye
31
Attachment of microbe to specific target cells
Adhereance structure
- Pili
- Fimbriae
- Glycocalyx
32
Colonisation
Establish a site of microbial replication
on or within host
33
Invasiveness
Ability to spread to adjacent tissues
34
Active invasion
- Ability to spread to adjacent tissues - distruption of intestinal lining
35
Passive Invasion
- Host tissue alteration was already present and it was not caused by the pathogen
- Skin lesions, insect bites, wounds
36
Bacteremia
Presence of viable bacteria in the blood
37
Septicemia
Bacterial or fungal toxins in the blood.
38
Clostridium tetani
- noninvasive because it does not spread from one tissue to another, but toxins become blood borne
39
Bacillus anthracis
- Yersinia pestis (plague) also
produce toxins and are highly invasive
40
Streptococcus
span invasiveness
41
Overcoming Host Defences
- Pathogens overcome competition adaptive
immune system
- Shelter to avoid recognition by defence cells.
- Survive and replicate inside host cells
- Squeeze between host cells.
- Avoid phagocytosis (capsule)
- Burrow under mucus.
- Find shelters within biofilms.
- Produce enzymes that inactivate innate resistance mechanisms.
- Excrete specialized proteins to selectively kill host cells
- Mutate and/or reduce cell surface proteins detected by immune cells
42
Meningitis and influenza
- Production of slippery mucoid capsule that prevents phagocytosis by host immune cells
43
Lipopolysaccharide overcoming host defence
- Eliminate O-antigen diminish immune recognition and clearance
44
Biofilm bacteria overcoming host defence
Protected from antimicrobial agents,
antibody and host immune cell
45
Damage to the host tissue
- Secreting enzymes that degrade host cell for nutrients
- Replicating inside the cells and inducing apoptosis
- Toxins disrupt the normal metabolism Exotoxins & Endotoxins
46
Hypersensitivity reactions
Inducing an excessive release of cytokines by immune cells and exacerbating inflammatory responses,
destroying tissues
47
Exotoxins
- In mostly gram positive bacteria part of growth and metabolism
- Released to surrounding medium
48
Endotoxins
- Part of outer portion of cell wall on gram negative bacteria
- Liberated when bacteria dies the cell wall then braks appart
