Disease, Transmission & S. aureus Flashcards
define infection
pathogens overcome body’s natural resistance, multiply and become established in the body
when do we see signs and symptoms?
when the body mounts a response to an infection
define infectious
able to be transmitted from one host to another
define pathogenesis
the harm that the pathogen is doing to the host
what is the pathogenesis of Vibrio cholera and HIV?
V. cholera: destroys epithelium of sm. intestine
HIV: destroys helper T-cells
define pathogenicity
pathogen’s ability to cause disease in the host
define virulence
measure of pathogenicity
define virulence factor
what the pathogen uses to cause harm in the host
what can virulence factors be?
enzyme, molecule, toxin, particular structure
define infectious dose
number of microbes needed to establish an infection in the host
a lower infectious dose for a microbe is (easier/harder) to transmit
easier
infectious dose for enterohemorrhagic type of E. coli
infectious dose for V. cholera
10 cells
1000 to 1 million cells
6 modes of transmission
direct contact
indirect contact
droplet
airborne
contaminated food & water
vectorborne
fecal-oral is a type of _______ transmission
direct contact
what is a fomite and what type of transmission is it involved with?
inanimate object that could harbor microbes
indirect contact
what is direct transmission?
skin & mucous membrane contact between hosts
touching, kissing, sex
what is indirect contact transmission?
transfer of microbes via inanimate objects
what is droplet transmission?
droplets (coughing, sneezing) settle onto a surface, or could be inhaled while in midair
what is airborne transmission?
very small droplets dry out in the air and become suspended there
what is cross-contamination?
pathogens from one food source transferred to another
raw poultry meat contains which bacteria?
Salmonella sp.
what is vectorborne transmission?
what usually serves as a vector?
Living organism carries pathogen & transmits it to host
arthropod - mosquito, fly, tick, flea
what is a biological vector?
arthropod plays vital role in pathogen’s life cycle
What is S. aureus’ Gram and shape?
Gram +
coccus
what can a staph infection cause? (6)
food poisoning
wound infections
toxic shock syndrome
impetigo
scalded skin syndrome
folliculitis
how can staph be transmitted?
direct
indirect
droplet
2 main varieties of MRSA
community associated
healthcare/hospital associated
staph favors the ______ mucosa
nasal
__% of people are colonized with staph, and ______% with MRSA
40%
10-15%
what are bacteremia and septicemia
bacteremia - bacteria grow in blood
septicemia - bacteria and/or their toxins reach blood
staph’s 7 virulence factors
capsule
coagulase
clumping factor
enterotoxin
ALPHA toxin
leukocidin
exfoliatin
what does a capsule do for staph?
helps in evading phagocytosis
what is the function of coagulase?
activates prothrombin
causes blood to clot
protects bacteria from immune cells
evading phagocytosis
what is the function of clumping factor?
allows bacteria to attach to surfaces and clots
which virulence factors make it easy for staph to infect humans?
coagulase
clumping factor
what does enterotoxin cause?
if ingested - food poisoning
in blood - toxic shock syndrome
what are signs and symptoms of TSS
Diarrhea, ill feeling, headache, fever, nausea, vomiting, organ failure, death
Hallmark: very red eyes, mouth, throat, skin
TSS used to be caused by…
but is now mainly caused by…
tampons left in too long
packed wounds that aren’t changed
what is the function of ALPHA toxin?
pokes holes in plasma membranes
which virulence factor of staph causes necrosis?
what is necrosis?
ALPHA toxin
tissue death
what is the function of leukocidin?
kills WBCs, especially neutrophils
what is the function of exfoliatin?
what does it cause?
separates layers of epidermis
scalded skin syndrome
