Lecture 16: Infection&Pathogenicity Flashcards
What is the name of a molecule that can recognized as non-self by the immune system?
antigen
What type of bacteria often have LPS on their surface?
Gram negative
What are 3 chemical barriers pathogens must overcome?
Lysozyme (tears), lactoferrin (milk), bacteriocins (microbiota)
How can bacteria pass genes between cells?
Horizontal gene transfer
Host
larger organism that supports the survival and growth of the pathogenic organism
Infection
- microbe grows on/in host
- May not result in overt symptoms or disease
Infectious disease
- any change from state of health
- part of all the host is incapacitated due to pathogen or its products
Pathogen
- any organism that causes disease
Opportunistic pathogen
- part of the normal microbiota that only causes disease when host is immunocompromised
Pathogenicity
- ability of a pathogen to cause disease
Virulence
- degree of harm inflicted on the host
Extracellular pathogens
- remain in tissues and fluids but never enter host cells during disease
Intracellular pathogens
- grows and multiply within host cells
Facultative intracellular pathogens
- reside within the cells of the host or in the environment
Obligate intracellular pathogens
- ONLY grow inside the host cells
Infectious disease course
- incubation period
- prodromal stage
- illness period
- convalescence
Incubation period
- time between pathogen entry and development of signs and symptoms
Prodromal stage
- Mild, non specific signs and symptoms
illness period
- disease is most severe ad display signs and symptoms
Convalescence
- recovery stage
The host provides the pathogen:
- protection
- nutrients
- energy to use
Reservoir
- source of pathogens
- natural environmental location in which the pathogen normally resides
Vector
- organism that spreads disease from one host to another
- ex. mosquitos, ticks, fleas, mites, or biting flies
Direct transmission
- droplets: saliva, mucus
- horizontal contact: kissing, sex
- vertical contact: mother to child, herpes
- vector: infection passed by another animal
Indirect transmission
- Fomites: mediated by inanimate object
- fecal/oral: contaminated food and water
- Aerosols: particles that remain in air (Covid19)
Portal of entry
- skin, respiratory, gastrointestinal, urogenital system
- attachment of microbe to target cell is first
Colonization
- establish a site of microbial replication on or within host
Adherence mechanisms
- adhesions have high degree of specificity to target tissues
Adherence structures
- pili
- fimbriae
- membrane and capsular materials
- specialized adhesion molecules on microbe’s cell surface
Bacteremia
- invasion
- presence of viable bacteria in the blood
Septicemia
- bacterial or fungal toxins in the blood
Surviving host defenses
- survive and replicate inside host cells
- squeeze between host cells
- produce type VI secretion system
- make capsules to avoid phagocytosis
suppression of host immune response
- infect cells of the immune system and diminish their function while ensuring their own survival
- eliminate O-antigen of lipopolysaccharide to diminish immune recognition and clearance
Mucoid capsule
- prevents phagocytosis by host immune cells
Phase variation
- changing gene expression to hide from host immune system
- results in new, unrecognized antigens on surface
Biofilm
- protected fro nutrient deprivation, predators, antimicrobial agents and host immune cells
Virulence factors
- large segemnts of bacterial chromosomal and plasmid DNA found to encode
Pathogenicity islands
- increase bacterial virulence
- absent in nonpathogenic members of sam genus or species
- genes can spread from one bacterial cell to another
Toxin
- substance that disrupts the normal metabolism of host cells
Toxigenicity
- pathogen’s ability to produce toxins
Intoxications
- disease that result from entry of a specific pre-formed toxin into host
Damage to the host (Exotoxins)
- heat-labile proteins
- travel from site of infection to other body tissues or target cells
- encoded by genes on plasmids or prophages within bacteria
Superantigens
- stimulate abt 30% of host T cells of the immune system
- causes T cells to over-express genes that encode cytokines and release pro-inflammatory molecules
Damage to the host (Endotoxins)
- Heat stable
- Toxic
- Generally similar, despite source
- Cause general system effect: ex. fever
Damage to the host (Endotoxins- LPS)
- gram negative cell wall toxic to mammals
- endotoxin bc bounds to bacterium and released when the microorganism lyses
- toxic component is the lipid portion, lipid A
Mycotoxins
- toxins produced by fungi
- common contaminants of food crops
- contaminate water- damaged buildings
- produce hallucinogen lysergic acid (LSD)
Active immunity
- results from production of antibodies by immune system in response to antigen
Active immunity - natural
recovery from a past infection
Active immunity- artifical
- immune response stimulated by vaccination
Passive immunity
- acquired from something other than your own immune system
Passive immunity- natural
- transmission of IgA from mother to infact
Passive immunity- artifical
- direct injection of antibodies (after rabies exposure)
