Infection and Pathogenicity Flashcards
what is a host?
a larger organism that supports the survival and growth of a smaller organism
what is a parasite?
live on or within a host organism and are metabolically dependent on the host
what is it called when a microorganism is growing and multiplying within/on a host?
infection
what is a pathogen?
any parasitic organism causing an infectious disease
what does a primary pathogen do?
causes disease by direct interaction with healthy host
describe an opportunistic pathogen
may be part of normal flora and causes disease when it has gained access to other tissue sites or host is immunocompromised
what is the name for the ability of a parasite to cause disease?
pathogenicity
what are infections passes from animals to humans?
zoonoses
what is the natural environmental location in which the pathogen normally resides called?
reservoir
give 4 examples of reservoirs
- animals
- soil
- water
- humans
what are objective changes in the body that can be directly observed?
signs
what are symptoms?
subjective changes experienced by patient
what is a disease syndrome?
a set of characteristic signs and symptoms
what is virulence?
the degree or intensity of pathogenicity
what 2 things must a pathogen do to cause disease?
- contact the host
2. survive!
what 3 things does a pathogen need to survive on or within a host?
- a suitable environment
- a source of nutrients
- protection from harmful elements
what poses a an issue with the fact that a pathogen needs a source of nutrients to survive on or within a host?
the pathogen is in competition with eukaryotic host cells
what allow a pathogen to outcompete host cells and resist their defenses?
virulence factors
what are virulence factors?
encoded in microbial chromosome, can occur as pathogenicity islands
where are pathogenicity islands found?
in genetic material
what do pathogenicity islands do?
increase virulence
are pathogenicity islands found in the nonpathogenic members of a species?
nope
what is incubation period?
the period after pathogen entry but before signs and symptoms
what is the prodromal stage?
onset of signs and symptoms
“I think I’m starting to get sick”
are signs in the prodromal stage clear enough for diagnosis?
nope, just very general
describe the period of illness stage in an infectious disease
disease is most severe, distinct signs and symptoms
what happens in the convalescence period of an infectious illness?
signs and symptoms being to disappear
what are the 4 stages during the course of an infectious illness?
incubation, prodromal, illness, convalescence
what do virulence factors do?
determine the degree to which the pathogen causes damage, invasion, and infectivity
virulence is determined in part by a pathogen’s ability to do what? (5)
- survive outside the host
- adhere to and colonize the host
- disseminate through host tissues
- toxogenicity
- resist host defenses
what does evidence suggest about the link between mode of transmission of a pathogen and its degree of virulence?
- direct contact = less virulent
2. vector-borne = highly virulent in human host, relatively benign in vector
what does a greater ability to survive outside a host suggest about the virulence of a pathogen
more virulent if can survive outside host for long time
is transmission alone enough for infection to occur? if no, what else must also take place?
tropism
what is tropism?
pathogen must make direct contact with appropriate host tissue
what determines tropism?
specific cell surface receptors
what are the 5 main modes of pathogen transmission?
- airborne
- contact
- vehicle
- vector borne
- vertical
describe airborne transmission
pathogen suspended in air and travels at least 1 meter
what are droplet nuclei? (4)
- small particles (1-4 um in diameter)
- can remain airborne for a long time
- can travel long distances
- usually propelled from respiratory tract of cource organisms by sneezing, coughing, or vocalization
what is another important route of airborne transmission other than droplet nuclei? how does it work?
dust; microbes attach to the particles and go for a ride
describe contact transmission
coming together or touchng of source/reservoir and host
what are the 3 types of contact transmission
- direct contact (person to person)
- indirect contact
- droplet spread
describe direct contact transmission
physical interaction between source/reservoir and host
give 3 examples of direct contact
- kissing
- touching
- sexual contact
describe indirect contact transmission
involves an intermediate (usually inanimate)
give 3 examples of indirect contact
eating, utensil, bedding (FOMITES!)
describe droplet direct contact spread
LARGE particles (greater than 5um) that travel LESS than 1 meter
what are vehicles in transmission?
inanimate materials or objects involved in pathogen transmission
describe common vehicle transmission
single vehicle spreads pathogen to multiple hosts
give an example of common vehicle transmission
water and food
what are fomites?
common vehicles such as surgical instruments, bedding, and eating utensils
between what 2 types of tranmission is there overlap in that they both involve fomites?
indirect contact and vehicle transmission
what are the 2 types of vector borne transmission?
- external (mechanical) transmission
2. internal transmission
describe external (mechanical) vector borne transmission
passive carriage of pathogen on body of vector
is there growth of pathogen during external (mechanical) vector borne transmission?
no
describe internal vector borne transmission
pathogen carried withIN vector
what are the 2 types of internal vector borne transmission? describe
- harborage transmission: pathogen does not undergo changes within vector
- biologic transmission: pathogen undergoes changes within vector
when does vertical transmission occur?
when the unborn child acquires a pathogen from an infected mother
is vertical transmission as common as horizontal transmission?
no; it’s actually the least common mode of transmission
what is it called when babies are born with an infectious disease?
congenital disease
what are examples of congenital disease spread by vertical transmission? (4)
- gonorrhea (especially in the eyes)
- herpes
- german measles (rubella)
- toxoplasmosis
what type of transmission is most effective in causing outbreaks and why? (2 good answers, explain both)
- airborne, because it does not require direct contact but can overlap with indirect contact (by sneezing on things) or
- vector borne, because it can live for a longer time in multiple hosts, making it harder to eradicate (this one is really effective)
pathogens transmitted by which mechanism might be the most easily controlled and eliminated? why?
- direct contact; can’t live long outsdie the host
2. vehicle transmitted diseases: good cleaning helps control
describe the cycle of transmission that occurs in a pathogen with a reservoir and a separate host
pathogen is in reservoir (soil, humans, animals, food. etc.), then leaves the reservoir through a portal of exit, then utilizes its own mode of transmission to access the portal of entry into the susceptible host to cause disease
how does a pathogen initiate disease?
through adhesion and invasion factors
what does entry and adhesion do for a pathogen?
establishes colonization
describe entry of a pathogen, and what must happen next
through a portal of entry, then pathogen must attach
list 4 possible portals of entry for a pathogen
- respiratory tract
- GI tract
- urogenital
- skin
what are the 2 types of adherence by pathogens?
- non-specific, reversable binding
2. specific, permanent binding
what 2 aspects of a pathogen help it cause damage to a host?
- virulence factors
2. toxins
what are toxins?
biological poisons
give 4 structures that pathogens can have that aid in attachment
- pili
- fimbriae
- specialized proteins
- capsule materials (ex. slime layer)
what are the 3 types of toxins?
- exotoxins
- endotoxins
- mycotoxins
describe exotoxins (2)
- released into the host tissue as the bacterial pathogen metabolizes
- travel from site of infection to other tissue or target cells
what are endotoxins found on?
LPS (lipopolysaccharide Lipid S)
when are endotoxins released?
when the microorganism is lysed
what are mycotoxins produced by?
fungi
what are the 7 methods used by pathogens to accomplish host evasion/survive host defense?
- genetic changes
- biofilm formation
- capsule types (slime layers)
- degrade host immunoglobulins
- specialized proteins to hide or avoid detection
- removal of O side chain to hide or avoid detection
- fuse into host cells and hide
what type of host evasion/survival tactic does Staph a utulize heavily?
specialized proteins to hide or avoid detection
how does gonorrhea evade host detection/survive?
does not have O side chain so is harder to recognize
name 2 microorganisms whose method of evading/surving in the host is fusing into host cells to hide
- HIV
2. measles
