Introduction to Pathogens Flashcards
microbiota
normal flora
part of the innate immunity
do not cause disease (do some good)
commensalists or mutualists
how much does normal flora weigh?
5-10 pounds
1/3 in feces
also lots on skin
commensalism
neither harm or benefit the carrying host
mutualism
symbioitic relationship between two organisms where both benefit
benefits of flora?
produce Vit K
absorb nutrients
secrete bacteriocins
bacteriocins
released by normal flora to kill other bacteria
harm of flora
can be come pathogenic outside of normal niche
penicillinase bacteria
can interfere with therapy
breaks down penicillin
opportunistic pathogens?
normal flora outside of normal location can cause problems
streptococcus viridans
in mouth
can get to heart during dental procedures and results in infections endocarditis
three types of microbiota?
resident, transient, colonzation
resident normal flora?
costant and well defined
role in interference
-compete for binding site, nutrients, and create metabolic/toxic products and bacteriocidins
transient normal flora?
from travel
exposure to abnormal environment
colonization?
establishment of microbial population
acquisition of a new organism
flora in utero?
we are sterile
develop flora through birth canal, breast feeding, bottle feeding
facultative flora - acquired from oral exposure to feces
strict anaerobes can colonize only after sufficient facultative organisms are established enough that oxygen concentration are maintained at reduced levels
two basic mechanisms of pathogens?
invasion of tissue
production of toxins
invasiveness
ability to invade host tissues
different ways to invade host tissue?
capsule
adaptations
extracellular enzymes that degrade host tissues
virulence
combination of invasiveness and toxigenicity
LD50
percent dead vs. dose
measure of virulence
dose to kill half populationID50
communicability
transmission of infectious disease
factors involved in the communicability of a disease?
source (both dormant and latent) number of agents released by host capability of surviving the transit (host to host) percent of host susceptible to agent ID50 - infected vs. dose
ID50
infected vs. dose
dose require to infect half population
toxigenicity
production of toxins
exotoxins
secreted protieins
are heat labile
found mostly in gram-positive
what is found in gram-positive cells?
exotoxins
endotoxins
complex polysaccharides (LPS) that are part of bacterial cell wall -released when cell lysis occur
generally heat stable
in gram negative found
what is found in gram-negative cells?
endotoxins
pathogenic process?
adhere evade local immunity replicate evade systemic immunity must escape body for transmission to new host
intracellular pathogens produce?
chronic disease
extracellular pathogens produce?
acute disease
what are the stages of infection?
incubation prodrome (non-specific symptoms) specific-illness (have characteristic signs/symptoms) recovery latent
prodrome period
stage of infection
where you have non-specific illnesses
viruses
are parasites
obligate intracellular parasites
may be either DNA or RNA (single or double stranded)
surrounded by protein capsid
some viruses have envelope
-from host cell
virus replication
must attach to host cell
bunch of shit happens.
non-enveloped virus entry to cell?
pinocytosis
enveloped virus entry to cell?
fusion
abortive infections
virus infects a cell that doesn’t permit its replication
cytolytic infection
viral infection leading to cell lysis
persistent infections
viral infection that my be productive, latent, or transforming
rhinovirus
most common viral infective agent
-common cold
two modes of transmission for rhinovirus?
aerosol of respiratory droplets
contaminated surface
rhinovirus structure
single strand positive sense RNA and capsid
no envelope
viral proteins of rhinovirus?
proteins transcribed as single, long polypeptide and cleaved into structural and nonstructural viral proteins
bacteria
unicellular prokaryote microorganisms
bacterial cell wall
basis for classifaction
gram positive bacteria
thick layer of peptidoglycan on surface
also have lipotechoic acids (only gram +)
peptidoglycan
polymer of N-acetylmuramic acid and N-acetylglucosamine
gram-negative bacteria
thin peptidoglycan located between cytoplasmic and second outer membrane (periplasmic space)
have lipopolysaccharide in outer membrane
also have lipid A
gram-negative staining?
appear red
cocci
spherical bacteria
bacilli
rod-like bacteria
spirochetes
corkscrew bacteria
flagella
bacterial structure allowing for motility
-composed of flagellins that are also immunogenic
monotrichous
single polar flagella
lophotrichous
several polar flagella
amphitrichous
several flagella at each end
peritrichous
flagella cover entire surface
pili
bacterial appendage that are sort
sex pili and common pili
sex pili
involved in conjugation and transfer of genetic information from one cell to another
common pili
provides means for attachment to host cells and often play an important role in colonization
bacteria transmission
many require human to human
some can survive in environment
endospore
resistant to heat, radiation, drying
dormancy for hundreds of years WOWZA
capsules
bacterial structure with high MW polysaccharide
capsule
strongly adhered to cell wall
genetically and phenotypically controlled
slime layer
loosely associated with bacteria
aerobic bacteria
require oxygen
anaerobic bacteria
energy from fermentation
oxygen can be poisonous to these bacteria
facultative anaerobes
grow under aerobic conditions and can also ferment
clostridium difficile
gram positive, rod-shaped, spore former
obligate anaerobe
part of normal flora
has toxin A - enterotoxin - fluid accumulation
also toxin B - cytopathic agent
patient secretes large number of spores
can’t compete with normal intestinal flora
toxin A in c. dificile?
fluid accumulation - diarrhea
toxin B in c. dificile?
cytopathic agent
fungi
either yeast or mold
yeast
single cell fungi (oval or round)
mold
long filamentous fungi
forms a mat (mycelium)
thermally dimorphic fungi
change from mold to yeast depending on temperature
ambient temperature - mold
in host tissues - yeast
candida
yeast at ambient temp and mold in host tissue
**exception to most thermally dimorphic fungi
fungi metabolism?
most are aerobes
some facultative anaerobes
**no strict anaerobes
requires carbon source
cell wall of fungi?
has chitin
also ergosterol and zymosterol
ergosterol and zymosterol
in cell membrane of fungi
chitin
in cell wall of fungi
superficial mycoses
dead layers of skin/hair - mostly cosmetic
not major harm
subQ mycoses
get into deeper layers
can often remember trauma
single location
from environment
cutaueous mycoses
epidermis, hair, nails
not doing lots of harm
systemic or deep mycoses
internal organs
immunocompromised host
-not a good prognosis
no human-human transmission
dependent on geographic niche
most are sub-clinical
mycoses
fungal infection
candida albicans
part of natural flora
fungi
both yeast and mold
opportunistic in immunocompromised individuals
thrush and vaginitis?
candida albicans superficially
candidemia
aka fungemia
systemic fungal infection of candida albicans
parasite
one organism harms the other
protozoan
single cell parasite with membrane bound nucleus
metazoans
multicellular parasite
-worms
arthropods
parasite insects
ex/ lice
host
organism where parasite obtains nutrients
definitive host
where parasite reaches sexual maturity
intermediate host
where parasite passes through larval or asexual stages
accidental host
other than normal host
reservoir host
other than the normal host in which parasite is capable of living and serving as a source of infestation
get rid of reservoir, get rid of parasite
vector
carrier that transmits causative agent of disease from infected to non-infected
modes of transmission for parasites?
direct
-ingestion, skin penetration, inhalation, person-to-person
indirect
-vector, transplantation/transfusions
single-host parasites
human to human contact
oral-fecal T vaginalis and E. histolytica
multiple host parasites
require two or more hosts to complete life cycle
can be limited to geographical area
what causes more disease and misery than any other group of agents?
protozoa
according to WHO
protozoans
eukaryotic
large variation in size
true nucleus and cytoplasm
trophozoites
active form of protozoa (fragile)
cyst
dormant form of protozoa (resilient)
nematodes
round worms
tough outer cuticle (what eosinophils break down)
have separate organ systems and sexes
intestinal tract and blood
soil-transmitted helminthiasis
STH
ascaris, necator, ancylostoma, trichuris
in 5-14 year old age range
all cause nutritional impairment leading to cognitive impairment
platyheliminthes
tape worms
flatted ribbon shaped bodies
proglottids - generated by neck
proglottids
egg of platyhelminthes that is secreted in fecal matter
neck generates the proglottids
FMT
fecal matter transplant
treats c. dificile non-responsive to standard therapy (vancomycin)
