Bacteriology 2 Flashcards
How can one write a bacterial name?
Italics (most common) or underline
How are bacteria classified?
Genotype, phenotype, staining properties, metabolism, biochemical characteristics, fatty acid profile, gene sequencing.
What is phylogeny?
Science dealing with evolutionary relationship between
living organisms.
T/F: Most bacteria are pathogenic.
False, most are not.
What is a microbiome?
A microorganism in its particular environment. Ex bacteria living inside the human body.
What is the development of disease called?
Pathogenesis
How do bacteria cause disease?
Infectious diseases represent complex interactions b/w host, pathogen, and environment.
Accompanied with disease, what are the three facets of “the triangle of tragedy”?
Host, Environment and Pathogen
What are the different factors present in the host section of the triangle?
Breed, age, sex, genotype, immunity, physiology, damage.
What are the different factors present in the pathogen section of the triangle?
Type, genotype, survival, virulence, route, tropism, dose, resistance, vector.
What are the different factors present in the environment section of the triangle?
Housing, space, ventilation, hygiene, nutrition, disease control, survival.
What is a microorganism that has the potential to cause disease?
Pathogen
What is an infection?
The invasion & multiplication of pathogenic microbes in an individual or population.
T/F: Disease is the same thing as an infection.
False, a disease is when the infection causes damage to the individual’s vital functions or systems.
Does an infection always result in disease?
Not always
What is the portal of entry?
The site where microbes enter our bodies in order to cause infection.
What are 4 portals of entry where a microbe may enter?
- Skin
- Mucous membranes of Respiratory tract
- Gastrointestinal tract
- Urogenital tract
What are exotoxins?
Proteins produced by bacteria that are released into the surroundings (outside). Heat unstable.
What is an endotoxin?
A heat-stable lipopolysaccharide toxin produced in the cell wall of a gram-negative bacteria.
T/F: Endotoxins can induce inflammation by stimulating the immune system.
True.
Where is the location of endotoxins and exotoxins?
Endotoxins: part of the cell
Exotoxins: released from the cell
What is the source of endotoxins and exotoxins?
Endotoxins: lysed gram-negative bacteria
Exotoxins: living gram-positive and gram-negative bacteria
What is the chemical composition of endotoxins and exotoxins?
Endotoxins: LPS
Exotoxins: Protein
What is the antigenicity of endotoxins and exotoxins?
Endotoxins: poor
Exotoxins: high
What are some examples of exotoxins?
S. aureus, B. cereus, S. pyogenes, V. cholera, B. anthrcis.
What are some examples of endotoxins?
E. coli, Salmonella typhi, Shigella.
Do both endotoxins and exotoxins cause fever?
No, just endotoxins.
What are superantigens produced by, and what are they used for?
Pathogenic microbes (viruses, mycoplasma, bacteria) used as a defense mechanism against the immune system.
What do superantigens bind to?
MHC class II molecule on the antigen presenting cells and T helper cell receptor.
After T-cells are activated, what is the result?
Polyclonal T-cell activation and massive cytokine
release.
Describe the biofilm formation.
Microbes join in masses, cling to surfaces, produce extracellular substances, take in nutrients and form a biofilm. Ex dental plaque
When a bacterial population reaches a certain level, where can change occur?
Behavior, Appearance, Metabolism
What are two ways virulence factors can be transferred between bacteria?
Plasmids and bacteriophages
What are plasmids?
Small circular DNA in bacteria
What are virus particles which attack bacteria?
Bacteriophages
T/F: Plasmids and bacteriophages may carry genes for antibiotic resistance.
True
What are 2 examples that use plasmids to transfer virulence factors to the bacteria?
Tetanus neurotoxin and superantigens
What are 2 examples that use bacteriophages to transfer virulence factors to the bacteria?
Diphtheria toxin and Botulinum toxin
What are 3 processes involved in the transfer of virulence factors between bacteria?
Conjugation, transformation and transduction.
What is the process by which one bacterium transfers genetic material to another through direct contact?
Conjugation
Conjugation = Contact
Briefly discuss how conjugation works.
- Donor and recipient cells come together & attach at the pilus with contact
- One strand of plasmid DNA is transferred to the recipient that doesn’t have a plasmid
- The recipient synthesizes a complementary strand
- The donor synthesizes a complementary strand to restore its complete plasmid
What is transformation?
The genetic alteration of a cell resulting from the
direct uptake and incorporation of exogenous genetic material from its surroundings and taken up through the cell membrane(s) .
Briefly discuss how transformation works.
- A DNA fragment containing the gene of interest binds to a surface receptor on the bacteria
- The DNA is cut into smaller pieces
- One strand is degraded and the other is taken up inside the cell
- The DNA is then incorporated into the bacterial chromosome
What is the process by which DNA is transferred from one bacterium to another by a virus?
Transduction
Briefly discuss how transduction works.
- Phage inserts its DNA into the bacterium
- Phage enzymes degrade host DNA
- Cell synthesizes new phages that incorporate phage DNA and host DNA
- Transducing phage injects donor DNA
- Donor DNA is incorporated into recipient’s chromosome by recombination
T/F: Lysogenic conversion with bacteriophages can result in bacteria with virulence factors, such as toxins or capsules.
True
T/F: In the lysogenic cycle, the cell lyses and releases many phage virions.
False, that’s the lytic cycle
What is a pathogen?
A microbe that can cause disease
What is virulence?
Degree of pathogenicity, includes severity
What are virulence factors?
Properties or traits found in isolates that cause disease, but which are not found in isolates of the same species that lack the ability to cause disease.
What is predisposition?
What predisposes an animal to infectious disease.
T/F: the majority of bacteria are extracellular pathogens.
True
What is the sequence of events in bacterial or fungal pathogenesis?
Entry into the host, evade host defenses, colonize the host systems, multiply, exert damage in the host, transmit other hosts = infectious
How can bacteria cause disease?
Depleting the host’s nutrients by using them.
Direct damage to the host cell (Toxins).
As a result of immune response to the microbe.
Or a combination of all these.
What are some consequences of pathogen-host interaction?
No colonization, colonization, chronic infection.
Infection, Disease followed by recovery.
Infection, Disease, Death or disability.
Infection, disease, followed by persistence.
