Infection and Pathogenicity Flashcards
General Infection Terms
host
larger organism that supports the survival and growth of a smaller organism
General Infection Terms
infection
a microbe growing and multiplying on or within a host
T/F: All infections will result in an overt infectious disease.
FALSE – infection may or may not result in overt infectious disease
General Infection Terms
infectious disease
any change from a state of health
- part or all of the host is incapable of carrying on normal functions due to presence of a pathogen or its products
General Infection Terms
pathogen
any organism that causes disease
General Infection Terms
opportunistic pathogen
may be part of normal flora and causes disease when it gains access to other tissue sites or when the host is immunocompromised
General Infection Terms
pathogenicity
ability of a pathogen to cause disease
General Infection Terms
virulence
degree of harm (pathogenicity) inflicted on the host
Types of Microorganisms
extracelllular pathogens
- example?
remain in tissues and fluids and do not enter host cells during the course of disease
- yersinia pestis causes plaque (black death)
Types of Microorganisms
intracellular bacteria
grow and multiply within host cells
Types of Microorganisms
What are the two types of intracellular bacteria?
- facultative intracellular pathogens
- obligate intracellular pathogens
Types of Microorganisms
facultative intracelluar pathogens
- example?
reside within host cells but can also grow in the environment
- listeria monocytogenes
Types of Microorganisms
obligate intracellular pathogens
cannot replicate outside a host cell
T/F: All viruses are obligate intracellular pathogens.
TRUE
T/F: Bacteria such as chlamydia spp. and Rickettsia can not be cultured outside of host cells.
TRUE
T/F: Malarial parasites are protzoa that require host cells for growth.
TRUE
Course of Infectious Disease
What are the general phases in infection?
- incubation period
- prodromal stage
- illness period
- convalescence
Course of Infectious Disease
incubation period
period after pathogen entry; before signs and symptoms
Course of Infectious Disease
prodromal stage
- onset of signs and symptoms
- not clear enough for diagnosis
Course of Infectious Disease
illness period
disease is most severe; characteristic signs and symptoms
Course of Infectious Disease
convalescence
signs and symptoms begin to disappear
Course of Infectious Disease Terms
signs
- objective changes in the body that can be directly observed
- fever, rash, vomitting
Course of Infectious Disease Terms
symptoms
- subjective changes experienced by patient
- pain, loss of appetite
Course of Infectious Disease Terms
disease syndrome
set of characteristic signs and symptoms for a disease
Events in Infection and Disease
First step?
transmission from previous host or resevour to new host
What 3 factors affect the success of transmission?
- virulence of organism
- number of invading organisms
- presence of adhesion and invasion factors
Events in Infection and Disease
Second step?
organism outcompetes the resident microbiota for resources and survives host defense mechanisms
Course of Infectious Disease
Third step?
disease occurs when organism produces molecules that directly damage host cells OR stimulates host immune cells to destroy infected tissue OR alters the host cell genome affecting normal function
Sources of Pathogens
What are examples of animate sources of pathogens?
humans or other animals
Sources of Pathogens
What are examples of inanimate sources of pathogens?
water or food
Sources of Pathogens
reservoir
natural environmental location in which the pathogen normally resides
Sources of Pathogens
zoonoses
when an infectious agent is transmitted from an animal to a human
Sources of Pathogens
vector
organism that spread disease from one host to another
- mosquitoes, ticks, fleas, mites, or biting flies
Pathogen Transmission
T/F: Pathogen transmission occurs either directly or indirectly.
TRUE
Pathogen Transmission
What are the 4 main routes of pathogen transmission?
- airborne
- contact
- vehicle
- vector-borne
Pathogen Transmission
What type of transmission only pregnant women are capable of?
vertical transmission
Transmission and Virulence
T/F: Pathogen’s virulence may be strongly influenced by its mode of transmission and ability to live outside its host.
TRUE
Transmission and Virulence
T/F: Transmission alone is not enough for infection to occur.
TRUE – tropism
Transmission and Virulence
tropism
pathogen must make contact with appropriate host tissue; determined by specific cell surface receptors
Airborne Transmission
What are the 3 kinds of airborne transmission?
- droplets
- droplet nuclei
- dust particles
Airborne Transmission: Droplets
Indirect or direct?
direct transmission
Airborne Transmission: Droplets
Diameter size?
up to 2 mm in diameter
Airborne Transmission: Droplets
How are droplets produced?
when liquids are placed under force
- sneezing, coughing
Airborne Transmission: Droplets
Travel distance?
can travel < 1 m
Airborne Transmission: Droplet Nuclei
Diameter size?
1 to 5 micrometers
Airborne Transmission: Droplet Nuclei
How are droplet nuclei produced?
result from evaporation of the larger droplets
Airborne Transmission: Droplet Nuclei
How long do they stay airborne?
may remain airborne for hours or days and travel long distances
Airborne Transmission: Dust Particles
Indirect or direct?
indirect
Airborne Transmission: Dust Particles
Describe transmitting dust particles.
microorganisms adhere to dust particles
Airborne Transmission: Dust Particles
T/F: If microorganisms can survive long periods outside host, it can lead to infection.
TRUE
Contact Transmission
contact transmission
coming together or touching of source/reservoir and host
Contact Transmission
Direct contact
- “person to person”
- physical interaction between source/reservoir and host
- kissing, touching, and sexual contact
Contact Transmission
indirect contact
- involves an inanimate object (fomite)
- eating utensils, bedding
Vehicle Transmission
vehicles
inanimate materials that transmit pathogens
- food, water, biological materials, air
Vehicle Transmission
How effective is vehicle transmission?
single vehicle spreads a pathogen to multiple hosts
Vector-Borne Transmission
vector
direct living transmitter of a pathogen
- most are arthropods (insects, ticks, mites, fleas) or vertebrates (dogs, cats, skunks, bats)
Vector-Borne Transmission
Pathogens transmitted by arthropods are often ?? ??.
highly virulent
Vector-Borne Transmission
T/F: Pathogens harm their vectors.
FALSE – it is highly important that pathgoens do not harm their vectors
Vertical Transmission
vertical transmission
occurs when the unborn chold acquires a pathogen from an infected mother
Vertical Transmission
T/F: Vertical transmission and horizontal transmission are equally as common.
FALSE – vertical transmission is not as common as horizontal transmission
Vertical Transmission
Babies born with an infectious disease are said to have a ?? ??.
congenital infection
- gonorrhea, syphilis, herpes, german measles, toxoplasmosis
The rate at which an infection proceeds and severity directly correlate with the “??”, “??”, and “??”.
- inital inoculum of microorgansisms
- their virulence
- the host’s ability to combat infection
What are things contribute to a host susceptibilty?
- poor nutrition
- stress
- genetics
- immunocompromised
LD50 vs. ID50
Infectious dose 50 (ID50)
the number of microorganisms required to cause disease in 50% of the inoculated hosts
LD50 vs. ID50
The lower the infectious dose …
the higher the risk of infection
LD50 vs. ID50
Lethal Dose 50 (LD50)
the number of microorganisms required to be lethal to 50% of the inoculated hosts
LD50 vs. ID50
Highly virulent pathogens kill at a ?? than less viruleent organisms.
lower dose
Adherence and Colonization
What are the first steps of any disease?
entry and attachment
Adherence and Colonization
Examples of portal of entry.
- skin
- respiratory
- GI
- urogenital systems
- conjuctiva of the eye
Adherence and Colonization
adherence
mediated by special molecules called adhesions
- pili, capsules
Adherence and Colonization
colonization
- site of microbial replication on or within a host
- does not necessarily result in tissue invasion or damage
Invasion DIsseminates Pathogens
infectivity
ability to create a discrete point of infection
Invasion DIsseminates Pathogens
Invasiveness
ability to spread to adjacent tissues
Invasion DIsseminates Pathogens
Active Penetration
occurs through lytic substances that alter host tissue:
- attacking the ECM and basement membranes of integuments and intestinal linings
- degrading carbohydrate-protein complexes between cells or on the cell surface
- disrupting the host cell surface
Invasion DIsseminates Pathogens
Passive penetration
not related to the pathogen itself
- skin lesions, insect bites, wounds
Pathogen Dissemination
bacteremia
presence of viable bacteria in the bloodstream
Pathogens Dissemination
septicemia
presence of bacterial or fungal toxins in the bloodstream
Overcoming Host Defenses
T/F: Most microbes eliminated before they can cause disease due to immune system.
TRUE
Overcoming Host Defenses
How do pathogens overcome host defenses?
- produce Type III and IV secretion system
- find shelter to avoid recognition by defense cells
- survive and replicate inside host cells
- squeeze between host cells
- make capsules to avoid phagocytosis
- burrow under mucus
- secrete exopolysaccharides to form communal shelters within biofilms
- produce enzymes that inactivate innate resistance mechanisms
- excrete specialized proteins to selectively kill host cells
Biofilms
What are biofilm bacteria protected from?
- nutrient deprivation
- predators
- environmental shifts
- antimicrobial agents
- host immune cells
Biofilms
Some pathogenic bacteria within biofilms exchange ??, ??, and ??, altering their behavior.
- plasmids
- nutrients
- quorum-sensing
Biofilms
How do these bacteria information exchange interactions affect the bacteria when it comes to survival?
- less sensitive to antibiotics
- more resistant to host defense mechanisms
Pathogenicity Islands
Large segments of bacterial chromosomal and plasmid DNA was found to encode what?
virulence factors
Pathogenicity Islands
The large encoding segments ?? bacterial virulence.
increase
Pathogenicity Islands
The large encoding segments are ?? in nonpathgenic members of same genus or species.
absent
Pathogenicity Islands
Large encoding segments can be spread through ?? transfer of ?? to bacteria.
- horizontal
- virulence genes
Toxigenicity
What does it mean when microbes possess toxigenicity?
ability to produce toxins
Toxigenicity
toxin
specific substance that damages host
Toxigenicity
intoxications
diseases that result from entry of a specific preformed toxin into host
Exotoxins
exotoxins
soluble, heat-liable proteins
Exotoxins
Exotoxins are ?? into surroundings as pathogen metabolizes.
secreted
Exotoxins
T/F: Exotoxins often travel from site of infection to other tissues or cells where they exert their effects.
TRUE
Exotoxins
T/F: All exotoxins are made by any bacteria.
FALSE - exotoxins are usually synthesized by specific bacteria that have toxin genes in their plasmids or prophage DNA
Exotoxins
T/F: Exotoxins among the most lethal substances known.
TRUE
Types of Exotoxins
AB Toxins
composed of two subunits:
- A subunit: responsible for toxic effect
- B subunit: binds to specific target cell
(cholera toxin, diphtheria toxin)
Types of Exotoxins
Membrane-disrupting exotoxins
hemolysins
Superantigens
Stimulate about ?? of T cells of the immune system.
30%
Superantigens
What do superantigens causes T cells to do?
overexpress and release pro-inflammatory cytokines
Superantigens
T cell stimulation by superantigens typically results in?
failure of multiple host organs allowing time for the microbe to disseminate
Endotoxin-Lipopolysaccharide
What can LPS in gram-negative cell walls be to specific hosts?
toxic
Endotoxin-Lipopolysaccharide
Why are LPSs considered endotoxins?
they are bound to the bacterium and released when the microorganism lyses; some is also released during multiplication
Endotoxin-Lipopolysaccharide
What portion of of the LPS is the toxic component?
the lipid portion; lipid A
Endotoxins-General Feature
General features of endotoxins.
- heat stable
- toxic (nanogram amounts)
- weakly immunogenic
- generally similar, despite source
Endotoxins-General Feature
What are general system effects of endotoxins?
- fever
- shock
- damage to the lining of blood vessels
- weakness
- diarrhea
- inflammation
- intestinal hemorrhage
- fibrinolysis
