Agents of disease Flashcards
Infectious Disease
Invasion of body by microbes (not always contagious)
Contagious Disease
Spread between individuals (always infectious)
Process of how pathogens cause disease
Portals of entry -> Evasion of defenses -> Damage to Host cells -> Portals of Exit
Virulence factors
Ability to infect and cause disease (enzymes and toxins)
Bacteria external morphology (shapes- 3)
Cocci: round, berry-like shape
Bacilli: rod, long, branch
Coccobacillus: oval, very short bacilli
Bacteria external morphology (groups- 4)
Pairs, chains, tetrads, clusters
Bacteria cell wall (types- 2)
Gram + and Gram -
Gram +
- Allows filtration and protection
- Thick wall with several layers
- Techoic acids running parallel to peptidoglycan which anchors plasma membrane
- Protection from desiccation (drying out)
Gram -
- Thin, single layer w/outer membrane
- Vulnerable to desiccation
- Contains LPss, toxic to animals
Steps on how to perform a gram stain
- Fix bacterial sample to microscope slide using heat or methanol
- Crystal violet stain added (everything purple)
- Iodine solution added
- Decolonization by adding ethanol (extracts purple from thin cell walls of gram -)
- Gram - = colourless, Gram += purple
- Add fushin, makes gram- = pink
Strict aerobes
Needs oxygen, aerobic respiration
Strict anaerobes
Oxygen will kill them, fermentation, anaerobic respiration
Facultative anaerobes
Prefer to use oxygen, can use fermentation, facultative respiration
Microaerophilic
Needs oxygen but too high will be fatal.
Viruses key properties
- Dependent on host to synthesize new proteins
- Reproduce easily
- Contains nucleocapsid and envelope to help with cell entry and antigenic determinants
- Less control sequences for higher change of mutations
Virus shapes (3)
- Helical
- Icosahedral
- Complex
7 step virus replication
- Attachment to plasma membrane
- Penetration into cytoplasm/nucleus
- Uncoating virus particle and release nucleic acid
- Synthesis of viral proteins
- Synthesis of viral genome, nucleic acid replication
- Virus assembly
- Release from cell (budding or cell lysis)
Key properties of fungus
- Eukaryotic, chitin cell walls
- Hard to destroy due to overactive immune response and damage to host
- Yeasts and moulds
Hyphae
Basic cell unit of moulds which are pereforated by pores that allow nuclei and organelles to flow between cells
Mycelium
Many Hyphae
Yeasts
Psuedo-hyphae and reproduce by budding
Key properties of Prions
- Proteins found in nervous system (help w/ homeostasis + generation)
Infectious prions cause and result
Misfolded proteins (B-pleated sheets) causes brain death
Parasite
Organism living in another organism and deriving it’s nutrients
Ectoparasites definition
live on surface of host
Ectoparasite examples (5)
- Fleas (itching, blood loss, allergy)
- Mites (itching, inflammation, rashes, burrows into skin)
- Lice (itching, tissue damage)
- Ticks (lyme, burrows into skin, blood loss)
- Flies (myisasis and tissue damage)
Endoparasites
Parasites that live inside host
Direct life cycle
Grow and mature in single host
Indirect life cycle
Infects 1 or more intermediate hosts before transmitted to final
Helminths (class)
Large parasitic worm that can be seen with naked eye
Nematodes
- Microscopic roundworms/eelworms
- Direct lifecycle
- Free-living, feeding on environment or parasitic
- Live within host migration pathways
ex. Lungworm, Large roundworm
Trematodes
- Flatworms
- Parasitic + indirect lifecycle (usually start in snail)
- Ex. Liver fluke
Cestodes
- Tapeworms w/ segmented bodies
- Indirect lifecycle
- Meat borne disease
- Ex. Gid Cysts in Sheep
Protozoa
- Single-celled eukaryotes
- Free-living or parasitic and feed on organic matter
- ex. Coccidiosis and Babesia