bacterial pathogenesis Flashcards
define parasitic organism
organism that harms or lives at the expensive of another organism
define normal microbiota
organisms that colonize the body without normally causing disease
define infection
when a parasitic organism is growing and multiplying within or on a host, the host is said to have an infection
define infectious disease
infection of a host by a microbe that results in some damage to the host and/or alteration of normal function of the host
define nosocomial infection
an infection that develops within a hospital/other type of clinical care facility
define pathogen
a microbe that’s able to cause disease
define pathogenicity
the ability of a pathogen to cause disease
define opportunistic pathogen
an organism that’s part of the normal microbiota that becomes pathogenic under certain situations (ie immune system becomes compromised by disease, old age, use of antibiotics)
define virulence
refers to the degree/intensity of pathogenicity
what three factors is virulence determined by
invasiveness, infectivity, pathogenic potential
define invasiveness
the ability to spread to adjacent or other tissues
define infectivity
the ability of an organism to establish a focal point of infection
define pathogenic potential
the degree of damage the microbe can cause to the host
define toxigenicity
the ability of the microbe to produce toxins
how can the virulence of a microbe be measured experimentally
by determining the infectious dose or lethal dose of a pathogen, which is the dose required to infect or kill 50% of the hosts in a given time period
list 5 portals of entry
skin, respiratory tract, gastrointestinal tract, urogenital system, direct entry (injection sites, bites, burns, wounds, surgical processes)
describe how pathogens can enter via the skin
ducts of sweat glands, mammary glands, hair follicles, conjunctiva (membrane of eyes/eyelids) via contaminated fingers/flies/towels
describe how pathogens can enter via the respiratory tract
inhalation of air containing pathogens
describe how pathogens can enter via the gastrointestinal tract
food, water, contaminated fingers
describe how pathogens can enter via the urogenital system
during sexual intercourse, some can travel from the skin to the urethra and vagina
how do pathogens exit the body
usually via urine, feces, saliva, tears, etc
list the 3 possible outcomes of a pathogen gaining entry to the body
- may pass through as a harmless transient
- could colonize and become part of normal microbiota
- could colonize and cause disease
list 4 things that determine whether or not a microbe will cause disease to a host
number of organisms the host is exposed to, virulence (invasiveness, infectivity, pathogenicity), host’s immune status at the time of infection, whether or not the desired portal of entry was used
list 7 things a successful pathogen must be able to do
maintain a reservoir
be transmitted to the host
adhere/colonize/invade the host
evade host defense mechanisms
multiply and grow in the host
have the ability to damage the host
leave the house + enter the reservoir of another host
what is a reservoir
a site in which the organism can persist and maintain its ability to infect prior to entering another host
what can a reservoir be (3 examples)
a human (with active infection or a carrier), an animal, a nonliving reservoir (ie soil, water, food)
list 2 modes of transmission
direct or indirect
what is horizontal contact
direct contact, ie kissing, sexual contact, or shaking hands
what is vertical contact
transmission from mother to baby
at what distance can airborne droplets infect someone
less than 1 meter
what is a vector
a living organism that can transmit disease to humans
what are two types of vectors
mechanical and biological
describe a mechanical vector
transmits the pathogen to its host passively on their feet and body parts
describe a biological vector
transmits pathogen actively. The pathogen completes part of its life cycle in the vector before it can be transmitted
describe indirect modes of transmission
transmission via an inanimate object called a vehicle
list some vehicles of pathogens
doorknobs, drinking glasses, utensils, dirty towels
what is a formite
an inanimate vehicle
describe how pathogens adhere to a host
pathogen attached to host tissues at the portal of entry via factors on bacterial called adhesins
what are adhesins
factors on bacteria that allow them to attach themselves to host tissues
what are adhesins made of
glycoprotein or lipoprotein
where on bacteria are adhesins found
capsule, fimbriae, flagellum
define colonization of the bacteria in the host
occurs after they adhere. Colonization refers to the establishment of a site of microbial reproduction
T or F: colonization always causes damage
false; some bacteria can be non invasive
describe how streptococci are invasive
they produce hyaluronidase (spreading factor). it degrades hyaluronic acid that glues epithelial cells together
what does staphylokinase do
dissolves blood clots
list how pathogens can evade host defenses
production of a biofilm or capsule, or specialized surface proteins that help them evade phagocytosis. Produce toxins that destroy phagocytes, some kill macrophages after being engulfed, some prevent the fusion of a phagosome with the lysosome, some gram neg can lengthen the O side chain of the LPS, some use host-derived actin tails to propel themselves from one host to another
list 3 ways in which the pathogen can damage the host
using the host’s nutrients, causing direct damage in the area of invasion, by producing toxins
list the 2 types of toxins that pathogens can produce
exotoxin and endotoxin
what is an exotoxin
a protein produced by a bacterium
what type(s) of bacteria produce exotoxins
both gram pos and gram neg
T or F: exotoxins are soluble in body fluids
true
are exotoxins potent
yes
are exotoxins stable in heat
no; destroyed by 60-80 C
T or F: the body can generate antibodies against exotoxins
true
describe how vaccines are made using exotoxins
exotoxins are inactivated via heat or chemicals (now called a toxoid). Toxoid gets injected, body makes antibodies against it, and now the person is immune
bacterial source of endotoxins?
gram neg only
what is the endotoxin made of
the lipid A portion of the LPS in gram neg bacteria
T or F: endotoxins are protein in nature
false; are lipid in nature
are endotoxins heat stable
yes; up to 250 C
describe the potency of endotoxins
lower potency: only toxic at high doses bc they’re relatively weak
define immunogenic
host recognizes the thing as foreign
is an endotoxin weakly or strongly immunogenic
weakly
symptoms of exotoxinxs
effect is variable depending on the exotoxin
symptoms of endotoxins
fever, chills, weakness, shock, death
T or F: the portal of exit is often identical to the portal of entry
true
