infections and defects in defence Flashcards
factors influencing infection
- communicability
- infectivity
- virulence
- toxigenicity
- portal of entry
communicability
ability to spread from one individual to others and cause disease
virulence
severity or harmfulness of a disease or poison
toxigenicity
ability to produce toxins (this is turn has a great influence on pathogen’s virulence)
portal of entry
the route by which a pathogen infects a host
- direct contact
- inhalation
- ingestion
- vectors (bites of an animal or insect)
bacterial diseases characteristics
- prokaryotes (lack a discrete nucleus - nothing encapsulating DNA)
- can be aerobic or anaerobic
- have a cell wall that encloses them
- can be gram positive or negative
2 main factors that make gram negative more difficult to defeat than gram positive
- outer membrane (peptidoglycan 2 layers)
- porin channels (protein gates to keep things out)
Staphylococcus aureus
- life threatening
- a major cause of nosocomial infections
- is common on normal skin and nasal passages
- has virulent (harmful) abilities:
1. produces a protein that blocks the complement attack of the body
2. avoids innate immunity by producing inhibitors that avoid recognition
3. when engulfed by phagocyte, they resist lysosome by changin chemistry of their cell walls
4. resists the actions of many antibiotics
toxin production
- exotoxin:
- released from inside of the pathogen
- it release enzymes that damage host cell plasma membranes or inactivate enzymes critical to protein synthesis - endotoxin
- release from the outer capsule
- activate the inflammatory response and produce a fever
bacteremia (presence of) and septicemia (growth)
- result in the defense of mechanism failure
- endotoxins: activate inflammatory response
- activate complement and clotting systems with results like: increased capillary permeability, large volumes of plasma into surrounding tissues, hypotension
viral disease characteristics
- most common affliction of humans
- replication requires entry into host cell
- simple organism: DNA/RNA surrounded by capsid and perhaps an envelope
- they are self-limiting
- transmission: aerosol, infected blood, sexual contact, vector (tick, mosquito, etc)
cytopathic effects of viruses
cytopathic: causing damage to living cells
- inhibits host cell DNA or RNA synthesis
- cause the release of lysosomes into host cell, killing cell
- fusion of host cells into multicellular giant cell
- alteration of host cells antigen properties = immune system attacks own cells
- transforming host cells into cancerous cells = uninhibited growth
- utilization of host cell resources
influenza
highly contagious viral infection of the respiratory passages
- antigenic variation: the ability to change viral antigen (protein spikes) yearly
- antigens are utilized to activate adaptive immune response
- have the ability to change the adaptive immune response (change the T cells/B cells)
- ex. SARS-CoV-2 virus (COVID)
fungal infections characteristics
- large eukaryotes with thick, rigid cell walls
- resist penicillin (bc penicillin comes from a natural form of fungi)
- exists as single cells called yeasts or multicellular molds
- reproduction is simple division or budding
mycoses
diseases caused by fungi
dermatophytes
fungi that invade skin, hair, or nails
- diseases they produce are called “tineas” (tinea capitis - scalp)
pathogenicity of fungal infection
- adapt to host environment (vide variations)
- suppress immune defenses
- low WBC count promotes fungal infection
candidas albicans
- most common cause of fungal infections
- found in normal skin microbiome, Gi tract, and vagina of many individuals (don’t want it to get past mucus layer)
- most common fungal infections in cancer patients and transplantations
- disseminated (spreading) infection in immunocompromised may involve deep infection and has high mortality rates
- death rate of disseminated candidiasis is 30-40%
parasitic infection
from unicellular protozoa to large worms (helminths - flukes, nematodes, tapeworms)
- spread human-human by vectors (ticks, mosquitoes, etc) or by ingestion (contaminated food or water)
- cause tissue damage due to toxin or inflammatory/immune response
Plasmodium (malaria)
parasite
- effects RBC
- causes anemia (in 28-72 hrs)
- RBC release cytokines (TNF-a and IL-1) which results in fever, chills, and vomiting
countermeasures
- antibiotics
- antimicrobials
- vaccines
- toxoids
- passive immunotherapy
- safeguards
problems of antibiotics and antimicrobials
antibiotic resistance
what caused a rise in antibiotic resistance
- lack of compliance with therapeutic regiment (not using antibiotics for the prescribed duration it leaves some microbes alive and then causing a repopulation of the resistant pathogens)
- overuse of antibiotics (destruction of the normal microbiome = opens space for more infections and resistant pathogens)
antibiotics
antibiotics: natural products of fungi, bacteria, or other microorganisms that affect the growth of specific organisms
