Intro to Infectious Disease Flashcards
What is the importance of the taxonomy of infectious agents?
Taxonomy is important because it can give an indication of the qualities of a given pathogen/microbe even if it has ever been encountered before. Ie/ All Clostridium species are:
- Gram positive
- Rod shaped
- Anaerobic
- Spore producing
How are infectious agents are constantly evolving, with new types and diseases emerging?
Microbes are able to replicate very quickly and their genomes are highly prone to mutations. Bacteria are also able to share plasmids with extra virulence components and survival traits that allow new variations of pathogen and disease to emerge constantly in response to the immune response and also modern medicine.
What is: Taxonomy?
Living things are classified in various ways. Infectious agents have a taxonomy to show the relation of one species with another. These taxonomies may be organized based on genetic makeup and rRNA or another inherent trait.
Summarise: bacteria?
Prokaryotic bacterial cells are far simpler than eukaryotic animal cells. They contain no organelles or membrane bound nucleus, instead having a single circle of DNA. They are usually at least 5 times smaller than an animal cell. Unlike animal cells, bacteria reproduce via Binary Fission.
What are some key components of all bacterium?
- Cytoplasmic membrane
- cytoplasmic matrix
- Ribosomes
- Genome (and perhaps plasmids)
- Cell wall
Explain the process of Gram staining?
The most well used of stains is the Gram Stain, during which Crystal Violet and Jenson’s iodine are washed over the bacterial specimen and then washed with ethanol to remove any dye that has not stained the organisms. A second stain of Carbol Fuchsin/Safranin is used to dye any remaining unstained organisms.
What is the difference between Gram Positive and Gram negative bacteria?
GRAM POSITIVE
- relatively simple structure, quite porous (sensitive to antibiotics)
- thick layer of peptidoglycan (15-80 nm)
- lipoteichoic/teichoic acids embedded in peptidoglycan layer
- stain blue/purple under Gram stain (retain Crystal Violet)
GRAM NEGATIVE
- more complex structure, with the major feature being an outer membrane. Thin peptidoglycan (10nm)
- prevents entry of bile salts and some antibiotics however small molecules such as glucose can pass through protein channels in the outer membrane. Larger molecules require specific carriers / secretion pathways
- outer membrane is stabilized by Lipopolysaccharide (LPS) which also acts as an endotoxin (PAMP) (LPS is made up of repeating units of O-antigen)
Explain: Cytoplasmic membrane?
It is a phospholipid bilayer which contains some proteins which are embedded in the bilayer; essential for survival as it allows selective interaction with the environment (entering nutrients and exiting waste); it has many invaginations that serve as the location of many metabolic processes such as respiration.
Explain: Cytoplasmic matrix?
CPM consists of mostly water making it relatively hypertonic; this matrix is packed with ribosomes
Explain: ribosomes
Ribosomes exist in hundreds per cell; made of rRNA & protein; used in the process of protein synthesis. Prokaryotic ribosomes are constructed to be 70S once assembled, compared to eukaryotic ribsomes which are 80S
Explain: the bacterial genome?
The nucleiod comprised of mostly DNA (+ some RNA & Protein) which no nuclear membrane; instead, the chromosome is a closed circle of dsDNA, looped and supercoiled with no introns or exons. No nuclear membrane allows the translation and transcription of the same RNA simultaneously allowing for quick evolutionary development. Bacteria may or may not also carry one or more plasmids which are small circles of dsDNA, supercoiled that replicate independent of the chromosome. Plasmids may have been inherited horizontally or vertically.
Explain: Bacterial cell wall?
The cell wall of a bacteria is a rigid layer outside the plasma membrane that gives a cell shape. It protects against osmotic lysis and harmful substances. The rigidity of the cell wall is due to peptidoglycan. It is the site of action of some antibiotics as cell wall components contain pathogen associated molecular patterns (PAMPs) that are recognized as being associated with disease. The cell wall of a bacteria is important in identifying it in the laboratory as different classes of bacteria have different cells all properties that react differently when stained.
