Introduction to Infectious Agents 4 Flashcards
bacteria that have cell wall and can’t be used with gram pos/neg stain, what stain can be used?
acid-fast stain
acid-fast will stain what color
pink
non acid-fast will stain what
violet
how do acid-fast stain work
bacteria on slide. initial stain: carbol fuchsin. if they take up the carbol fuchsin they will not be decoloriazed with decoloriser. then use counterstain.
what bacteria is acid-fast stain used for
mycobacterium
why are mycobacterium cannot do gram stain
high wax content in wall
example of acid-fast bacteria:
Mycobacterium
what is present in acid fast cell wall
Mycolic acid*
Trehalose dimycolate
Lipoarabinomannan
Arabinogalactan
example of bacteria without cell wall
mycoplasma
what do bacteria of no cell wall bacteria contain
sterols
what do no cell wall bacteria use to maintain fluiditiy
sterols
what is function of adhesins on cell wall less bacteria
adhesins - allow them to move like caterpillar
where is site of atp production in bacteria
plasma/cell memrane
what is plasma/cell membrane made out of in bacteria
phospholipid bilyaer
flagella are made of what
flagellin proteins
peritrichous
flagella all over the surface
“bad hair day”
lophotrichous
a tuft of flagella at one end
amphitrichous
one or more flagella at each end
monotrichous
one flagellum
where is axial filament found
only in perplasmic space
pilus and fimbria are made of what
pilins (pilus) and fimbrins (fimbria)
what is function of pilus and fimbria
adhesion to host cell surface
virulence factor
cell communication
genetic exchange of bacteria - what is needed for this to occur
sex pili (F pili)
describe structure of fimbriae on gram neg and gra positive
Gram +ve differs from Gram –ve fimbriae
capsule also called
glycocalyx and slime layer
what is function of capsule
anti-phagocytic (prevents phagocytocsis)
prevent dehydration
antibiotic penetration (makes it hard to treat with antibiotics)
capsules grow around
individual bacteria
what grows around colony of bacteria
biofilm
biofilm provides what advantage
protects against
phagocytosis
dehydration
antibiotic penetration
when is biofilm a huge bad thing in medical
if they grow on implanted stuff in body
what is genetic material in bacteria
hapoid DNA chromosome wound in nucleoid
pathogenicity islands
tend to find aggregation of genes that have antibiotic resistance, etc.
have G+C content
plasmids
extra chromosomal genetic elements
non-essential genetic info
what is an example of what can be contained in a plasmid
drug resistance
how many copies of plasmid
one or more ( no more than 20)
ribosomes in bacteria
70S
require N-formyl
what is significant about N-formyl on ribisomes in bacteria
chemoattractants - we have receptors that can recognize and bind to them and destroy. esp. neutrophils
in storage granules in bacteria what will be depsotied
glycogen
lipids
polyphosphates
why are storage granules used in bacteria
when ther eare unfavorable conditions
endospores
not reproductive - theya re just formed to allow bacteria to survive unfavorable conidions
not metabolically active
what does the core of endospore contain
high concentrations of calcium bound to dipicolini acid + keratin-like protein
draw a endospore
pg 50
within dehydrated core what will you find in endospores
ribosomes
what are 3 main wais bacteria uptake material
facilitated diffusion
active transport
group trnaslocation
can facilitated difussion work against concentration gradient
no
can active transpot and group translcoation work against concentration gradient
yes
group translocation
material that is translocated is modified by chemical group, usually phsphate from pyruvate. it is similar to active transport except that it is modified.
in gram neg. bacteria how many secretion systems are there
6
type III secretion apparatus in gram neg. is used to do what
used to inject toxins into host cell
what is type III secretion apparatus similar to in function
syringe
bacterial products (name 3)
exoenzymes
exotoxins
endotoxins
endotoxins
endotoxins not released but can be following bacterial cell damage
exoenzymes
degradative/hydrolytic
ex: lipases, proteases, hyaluronidase, hemolysins, DNases
certain species of bacteria secrete enzyme that forms clot, and what does clot do
surrounds bacteria
exotoxins - three main clases
A-B toxins
membrane-disrupting toxins
superantigens
exotoxins
produced by gram pos and gram neg.
never secreted through type III secretion appartus
have ot bind to receptor on surface of host cell to get into cell
A-B toxins what are subuntis
A & B
b subunit does what
binds to receptor on surface of cell
ex of b subunit
cholera toxin
A subunit does what
activates adenylyl cyclase which leads to disuprtion (in cholera)
mediates enzymatic activity resopsneible for toxcitiy
vaccines against A-B toxins
go against B subunit to prevent it from biding, it prevents toxin activity
what are two main ways that membrane disrupting toxins work
pore (channel) former
destruction of phospholipid bilayer (lipase activity)
superantigens
stimulate 20-25% of T cells
- superantigen binds to T cell receptor and APC - binds to ones that have particular V gene segments
normal way T cells recognize antigen
MHC class II presneting to receptor of T cell - T cell receptor recognizes peptide bound
what is result of superantigens
activates a lot of T cells but they are not specific
what can high levels of T cells being activated to
high levels of cyokines - toxic shock (cytokine storm)
what is result of endotoxic shock
bulk movement of fluid from circulation into tissues
endotoxic shock
collapse of blood vessels - leads to disseminated intravascular coagulation - death of cells and tissue b/c of hypoxic damage
what does DIC stand for
disseminated intravascular coagulation
bactericidal drug used if it is gram neg what happens
LPS release if it is gram negative
endotoxins are all
polysaccharides
exotoins are
protein
endotoxin and exotoxin are both
antigenic
endotoxin relationship to cell
part of outer membrane
exotoxin relationship to cell
extracellular, diffusible
can endotoxin and exotoxin form toxoid?
endotoxin - no
exotoxin - yes (vaccine)
special stains can be used to detect what
spores, capsule, falgellla
lot of method for identifying bacteria involves what
culture
selective media
allows growth of some species but not others
selective media
allows growth of some species but not others
list some common methods to diagnose bacterial infection
pg 62
what does serology tell you
if person was affected, can’t tell you if person is currently affected.
only way you can say currently is if you see increase in antibiotics over certain time
what do you use for molecular analyses for diagnosis of bacteria
PCR amplification DNA probes (in situ hybridization)
what is direct way to measure bacterial growth
microscopy
what is indirect way to measure bacteria growth
plate (CFU)
why is indirect more affective than direct (microscopy vs. plate)
on plate you are seeing live bacteria. microscopy can’t distinguish
describe growth curve of bacterial growth
lag
exponential
stationary
death
describe growth curve of bacterial growth
lag
exponential
stationary
death
under optimal conditions what is generation time of E. Coli
15-20 minutes
the bacteria that causes gangrene is what kind of bacteria
anaerobe
what do you do with deep wound with gangrene setting in and why
open wound to let oxygen in - kills the clostridia bacteria
what are rapid screening assays available now called
biotyping
how does biotyping work
substrates that some bacteria use and some can’t use
substrates chosen so if bacteria can use them there will be colored change on strip
What makes up the thick peptidoglycan layer in the cell wall of both gram pos. and gram neg. bacteria?
N-acetyl muramic acid
N-acetyl glucosamine
What does NAM stand for
N-acetyl muramic acid
What does NAG stand for
N-acetyl glucosamine
what will be found in gram pos but not in gram neg in peptidoglycan layer
Teichoic acids
Lipoteichoic acids
exoenzymes are generally:
degradative enzymes
name some example exoenzymes
lipases proteases hyaluronidase hemolysins DNases
describe how bacteria can penetrate to subepithelial layer of host
secrete exo-enzymes that break down basement membrane
describe how bacteria can secrete a clot and use it to their advantage
they secrete enzyme that secretes a clot so the body’s immune system can’t get to the bacteria. the clot surrounds bacteria. then they secrete enzyme that initiates disassembly of the clot and bacteria can go about their business
high level of LPS (in cell wall of gram neg. bacteria) what happens?
high production of cytokines → can result in endotoxic shock
causes bulk movement of fluid from circulation into tissues → hypotension → collapse of blood vessels → activation of coagulation cascade → lots of coagulation in lumen of blood vessels → occludes blood tissues → hypoxic death
What does DIC stand for
disseminated intravascular coagulation
why is there DIC in endotoxic shock?
widespread release of LPS
bactericidal vs. bacteriostatic drug
bactericidal drug and have high level infection w/ gram neg bacteria will cause widepread release of high levels of LPS
sometimes just better to use bacteriostatic drug and leg immune system kick in
what is the name of the bacteria that causes gangrene
clostridia
