PID Exam 1 Flashcards
Define Symbiont
Organisms that live with another organism
Define Obligate Symbiont and Facultative Symbiont
Obligate Symbiont: Need host to survive
Facultative Symbiont: Can live with or without a host
Define Pathogenicity
Ability of an organism to cause disease
Define Facultative Pathogenic
Can cause disease depending on the circumstances
Define Endogenic Infection
Infection resulting from organism that was already present in the body.
Define Exogenic Infection
Infection from organisms that comes from outside the body (eg from another person)
Define Obligate Pathogenic
Always causes disease
Define Balanced Pathogenicity
Damage with recovery (the majority of infections)
Define Unbalanced Pathogenicity
High damage/death
Define Infection
Invasion and multiplication of microorganisms eventually with disease (symptoms)
Define Disease
Disorder of structure and function
Define Subclinical
Eg a decrease in production, but no other symptoms. Feeling under the weather, but no symptoms.
Define Opportunistic Pathogen
The pathogen needs a specific precondition (eg a viral infection, allergy, a younger animal with less immune system)
Define Septicaemiae/Bacteraemia
Bacteria in blood stream (Blood infection)
Define Hyperacute, Acute, Subacute, Chronic.
Hyperacute: very severe, death - very fast onset
Acute: fast onset
Subacute: between acute and chronic
Chronic: long/ongoing - gradual or waves (bacteria could be hiding somewhere)
Describe the “threshold” for our bodies and microorganisms.
We can handle microorganisms to a certain extent before there is disease. However, if we become immunocompromised then there may be a problem.
Describe the differences between bacteria and eukaryotes when it comes to: Size, Membrane bound organelles, Ribosomes, Nucleic acid, Nuclear membrane, Replication
Size: Bacteria = <5um, Eukaryotes = >10um
Membrane bound organelles: Not present in bacteria, present in eukaryotes (mitochondria, chloroplasts)
Ribosomes: Bacteria: 70 Eukaryotes: 80S
Nucleic Acid: Bacteria = Single molecule (circular), Eukaryotes: Chromosomes
Nuclear Membrane: Absent in bacteria, Present in eukaryotes
Replication: Bacteria replicate by binary fission, Eukaryotes replicate via mitosis.
Describe the shapes of cocci, bacilli, coccobaccilli and fusiform bacteria.
Cocci: round
Bacilli: rod
Coccobaccilli: between cocci & bacilli (think tic tac)
Fusiform: spindle shaped
Describe the morphology of Gram Negative vs. Gram Positive bacteria
Gram Negative - thin peptidoglycan layer, outer membrane with lipid A (O antigen)
Gram Positive - thick peptidoglycan layer
Describe how to write bacterial names.
Genus: Capital and italic
Species: italic
Subspecies: italic
Serovar or other: Captial, not italic
What are the 4 things that prokaryotic and eukaryotic cells have in common
- Cell Membrane 2. Cytoplasm 3. DNA 4. Ribosomes (but different types)
What are the 3 groups of molecules that cytoplasm contains?
- Macromolecules (proteins (enzymes), mRNA, RNA)
- Small molecules (energy sources, precursors of macromolecules, metabolites or vitamins)
- Various inorganic ions (required for enzymatic activity (cofactors))
What does the cytoplasm do?
Helps facilitate chemical reactions and helps to dissolve solutes (carbs and proteins), contains nucleoids and ribosomes.
What is a Nucleoid? What does a nucleoid contain?
It is a “nucleus-like” structure that contains: DNA (~60%), proteins, RNA
Describe Bacterial Chromosomal DNA
It is a large circular macromolecule (some bacteria have more than one). It contains the complete set of DNA for the bacteria (the whole bacterial genome)
Describe how DNA is compacted by proteins in the nucleoid.
- DNA loop formation caused by Nucleoid-Associated Proteins (NAPs) bound to DNA
- DNA supercoiling is mediated by enzymes: DNA gyrase and topolsomerase I (similar to coiling of rubber band)
What proteins are located in the nucleoid?
Proteins involved in DNA compaction & Transcription factors that regulate expression of the bacterial genome
What types of RNA are located in the nucleoid?
mRNA (messenger RNA - encodes for proteins), ncRNA (non-coding RNA - involved in DNA organization and expression of bacterial genome)
What is a plasmid? Are plasmids essential?
A plasmid is a circular molecule of DNA that replicated separately from the chromosome. It is NOT part of the nucleoid.
Plasmid genes are NOT essential under normal conditions (they are not part of the genome and not all bacteria have them).
Each plasmid has a defined copy number. What is a copy number? Is this copy number low or high for small plasmids? Large plasmids?
A copy number is the average number of plasmid copies per cell.
Small plasmids = high copy number
Large plasmids = low copy number
What is the importance of plasmids?
Plasmids often contain genes associated with causing disease (virulence factors) or to survive in presence of antibiotics and other toxic compounds (resistance genes). Some plasmids (conjugative plasmids) can transfer cell-to-cell by a process called conjugation
What does the bacterial envelope contain? What is it associated with?
Cytoplasmic membrane, cell wall (peptidoglycan layer), periplasmic space, outer membrane (gram-negative bacteria), capsule (some bacteria)
Envelope associated with: pili, fimbriae, flagella, secretion systems
What are the functions of the bacterial envelope? What about envelope-associated components?
Protects cell from environment/host, packages internal components, provides structural rigidity, produces energy, facilitates uptake of nutrients and efflux (removal) of toxic substances
Some envelope associated components can also (some bacteria): enable adhesion to surfaces or motility, provide resistance to some antibiotics or detergents, enable bacterial mating (conjugation)
In the gram staining technique - what colour does gram positive bacteria stain? gram negative?
Gram positive stains purple
Gram negative stains pink
What is present in the outer membrane of gram negative bacteria?
Lipopolysaccharides (LPS) aka endotoxins
What is the cytoplasmic membrane composed of? Where is it located?
Composed of phospholipid bilayer and proteins (transport proteins, energy generation and electron transport chain components required for the synthesis of ATP by the ATP synthase protein, proteins that function as anchors or help in the assembly of external structuring)
It is the inner most membrane - next to cytoplasm
What are the functions of the cytoplasmic membrane?
Functions as a selective permeability barrier (lipid soluble molecules can diffuse across membrane, transport proteins mediate the passage of hydrophilic substances into/out of the cell), plays key role in energy generation (protein motive force) and bacterial respiration (electron transport chain), serves as anchor for external structures
What is the cell wall? What does it do? What is in composed of?
Cell wall is a mesh-like essential structure that protects cell from osmotic lysis and provides mechanical protection. Consists of polymers of disaccharides that are cross linked with short chains of amino acids (peptides) by transpeptidase enzymes called Penicillin Binding Proteins (PBPs)
What type of bacteria is the outer membrane present in? What is its job?
Present in gram negative bacteria.
Prevents passive diffusion of hydrophobic/large compounds, provides resistance to toxic compounds that are hydrophobic/large (this includes several antibiotics), provides tolerance to detergents and bile salts
Describe the structure of the outer membrane.
Asymmetrical lipid bilayer - outer leaflet is mainly composed of lipopolysaccharide (LPS) (prevents diffusion of hydrophobic compounds), porin proteins, transport proteins.
Why does Lipopolysaccharide prevent hydrophobic substances from entering the cell?
Because it has a charge
What is the importance of the capsule of a bacteria?
Helps bacteria evade immune system - can prevent engulfment by white blood cells (phagocytes), aids in attachment to some surfaces, increased tolerance to antimicrobial agents
Describe the structure/appearance of the capsule.
Polysaccharide layer outside of the cell wall (in gram positive) or outer membrane (gram negative).
If a bacterial colony has a mucoid appearance what do the bacteria likely contain?
A capsule.
List the 4 main types of surface components and briefly describe them.
- Flagella - motility, long filamentous proteins structures
- Pili/Fimbriae - adhere to surfaces or bacterial interaction (biofilm), shorter/stiffer than flagella
- Sex pilus - bacterial conjugation (transfer of plasmids)
- Secretion systems - release of proteins into environment/host, secreted proteins are typically related to virulence or bacterial communication
List and describe the 4 types of flagellar arrangements.
Monotrichous - one tail
Lophotrichous - multiple tails, all on one end
Peritrichous - multiple tails, all around the bacterium
Amphitricous - two tails, one on either end
What are endospores?
Dormant bacteria that can survive in adverse environmental conditions (harsh environments) and for long periods of time.
When endospores enter a host they can revert to “active” state, multiply and cause disease
Which type of bacteria is more likely to be a spore-forming bacteria?
Gram positive
Define obligate aerobe, obligate anaerobe, facultative anaerobe, aerotolerant anaerobes. Which is most common in clinical practice?
Obligate aerobe - need oxygen to grow
Obligate anaerobe - only grow in anaerobic environment (no oxygen)
Facultative Anaerobe - typically better growth in oxygen environment (but grows in both )
Aerotolerant Anaerobes - grows better in anaerobic environment but can grow in oxygen.
Facultative Anaerobe is most common in clinical practice.
List the gram positive, aerobic cocci
Staphylococcus, Streptococcus, Enterococcus
List the gram positive, aerobic rods
Actinomycetes, Bacillus, Coryne bacterium/Nocardia, Listeria, Mycobacterium, Rodococcus
List the gram positive, anaerobic ros
Clostridium
List the gram negative, enterobacteriaceae (rod)
Escherichia coli/Shigella, Salmonella, Klebsiella/Enterobacter, Proteus, Yersinia
List the gram negative, non-fermentative rods
Bordetella, Pseudomonas/Burkholderia, Aeromonas/Vibrio, Pasteurella/Mannheimia, Haemophilus/Histophilus, Brucella, Francisella
List the gram negative, anaerobic rods
Clostridium (pilifome), Fuscobacterium
List the miscellaneous, curved/spiral bacteria
Campylobacter/Helicobacter, Brachyspira, Lawsonia, Leptospira, Treponema/Borrelia
List the miscellaneous, obligate intracellular bacteria
Anaplasma/Ehrlichia, Chlamydia/Chlamydophila, Coxiella, Rickettsia
List the miscellaneous, bacteria without a cell wall
Mycoplasma
Describe the phases of infection.
Susceptible: Not yet infected, just at risk
Latent Period: Infected, the agent is multiplying in the body, immune system is working
Infectious Period: Infected and Shedding
Noninfectious Period: Removed (dead) or recovered (immune, carrier, susceptible)
Describe the phases of disease.
Susceptible
Incubation Period: No symptoms. Lasts longer than infectious latent period.
Symptomatic Period
Non-infectious Period: removed (dead), recovered
Why is it important that the incubation period of disease lasts longer than the latent period of infection?
Because the animal can not be showing any symptoms when they become infectious.
Define mutualism, commensalism and parasitism.
Mutualism: Both are necessary and the relationship is beneficial to both.
Commensalism: Good for one, no problem for the other
Parasitism: One takes advantage of/harms the other.
Describe the process of disease.
Adhesion: bacteria adheres to something inside/outside of the body
Invasion: replicates
Toxin Release: can make you sick
Where is the H-antigen found? What is an antigen?
H-antigen is found in flagella of motile bacteria
An antigen is a toxin that induces immune system response in body
In what type of bacteria would you more commonly find a flagella?
Gram negative.
What is the structural protein of bacterial flagella called?
Flagelin
Where is F-antigen found?
Pili, Fimbria, Fibrillae
Define extracellular invasion. What can it lead to?
Do not invade cells, proliferate in extracellular environment.
Can lead to thromboses (blood clots), local use of nutrients and oxygen (that the host needs)