Bacterial Pathogens Flashcards
prokaryotes
bacteria and archaea
spirochetes
unusual structure
chlamydia
unusual life cycle/obligate intracellular parasite
mycobacteria
unusual cell wall
mycoplasma
no cell wall
staphylococcus
gram positive
streptococcus
gram positive
enterococcus
gram positive
listeria
gram positive
bacillus
gram positive
corynebacterium
gram positive
actinomyces
gram positive
which bacteria do not stain?
mycobacterium, mycoplasma, spirochetes
spirochetes example
borrelia, treponema, leptospira
gram negative examples
salmonella, vibrio, neisseria, bordetella, e. coli, pseudomonas
ribosomes sensitive to diptheria toxin
eukaryotes only
ribosomes sensitive to cm/strep/kan
bacteria only
advantages of smallness
nutrient acquisition and waste removal rates, smaller genome is more efficient, large surface area to volume ratio to concentrate nutrients, rapid DNA rep, rapid evolutions, high population density
bacillus
rod
coccus
sphere
typical bacterial diameter
0.5 micrometers - 1 micrometer
branched filamentous
actinomyces and nocardia
diplococci
two spheres
diplobacillus
two rods
streptococci
line of spheres
streptobacillus
line of rods
staphylococci
bundle of spheres
colony morphology _ relate to shape of individual bacteria
does not
mucoid appearance indicates _
capsule
waxy appearance indicates _
high lipid content - mycobacterium
motile organisms form _
thin, spread-out colonies
pigments in bacteria
protection against light, indicates where organism normally lives
cell envelope
cell wall, membrane, capsule, pili and flagella
internal structures
nucleoid, plasmid, granules, ribosomes, endosomes
cell envelope consists of _
cell membranes, cell wall, imbedded proteins, glycocalyx or capsule
cell envelope function
barrier (osmotic, pH), solute and electron transport, gradients/ATP, motility, lipid synthesis, protein secretion
gram positive
thick layer of exterior peptidoglycan and a cell membrane with periplasmic space in between
gram negative
LPS outer membrane and then a thin internal peptidoglycan layer and then cell membrane (periplasmic spaces in between)
gram positive cell envelope acids
teichoic and lipoteichoic acids
teichoic and lipoteichoic acids
give cell wall a net negative charge (Mg, Ca), covalently attached to peptidoglycan, important for serotyping, can be shed and illicit immune response, may act as adhesins, required for viability
are teichoic and lipoteichoic acids found in gram negative bacteria?
no
gram negative cell envelope
contain outer membrane porins that restrict large molecules; contain an outer membrane and cytoplasmic membrane
periplasmic space may contain _
virulence factors such as collagenase, hyaluronidase, beta-lactamase
LPS outer membrane (gram-neg)
contains oligosaccharides, core polysaccharides, divalent calcium and magnesium, lipid A
oligosaccharide chain
loss by pathogens will reduce virulence
core polysaccharides
provide resistance to hydrophobic compounds; resistance to bile acids by enteric bacteria
divalent calcium and magnesium
strengthen LPS intermolecular interactions; can be weakened by EDTA
lipid A
toxic to humans; contains only saturated fatty acids for rigidity; essential for viability
What antibiotics target LPS?
polymyxin antibiotics
lipopolysaccharides (LPS, endotoxin)
lipids + sugar; no proteins/peptides; resistant to heat, protease, autoclaving
O-specific polysaccharide
varies among species; useful for identification of organisms
core polysaccharides
glucose, galactose, heptose, KDO, glucosamine
lipid A is inserted _
in outer membrane
core an O-specific polysaccharides are _
hydrophilic with a negative charge
LPS actions
activates B cells, stimulates macrophages/DCs to produce cytokines, causes fever, causes leukopenia, fatal at high doses, enhances glycolysis which leads to hypoglycemia
septic shock/endotoxin shock
fever, chills, malaise, increased HR and RR, extreme hypotension, multiorgan failure, coagulation pathway
extreme hypotension in septic shock is caused by
IL-1, IL-6, TNFa
activation of coagulation pathway leads to _
disseminated intravascular coagulation (DIC)
peptidoglycan layer (murein)
critical for resistance to osmotic stress, critical target for antibiotics, permits diffusion, and has pyrogenic activity
peptidoglycan layer consists of _
amino acids, sugars (NAG/NAM), other molecules
chemical structure of peptidoglycan
N-acetylmuramic acid (NAM) is never found in eukaryotes; repeating units of NAM/NAG, D-aminos + L-aminos, diaminopimelic (DAP) (DAP in - and lysine in +)
lysozyme
breaks a bond in NAM; gram positive organisms are most sensitive
when can lysozyme cross outer membrane of gram negative bacteria?
only after osmotic shocks and EDTA treatment
transpeptidation reaction is inhibited by _
beta-lactam antibiotics
gram staining
crystal violet –> gram’s iodine –> decolorizer (alcohol) –> safranin red
gram positive will stain _
purple
gram negative will stain _
red/pink
Which bacteria is susceptible to penicillin G?
gram positive
how many membranes do gram negative bacteria have?
2
how many membranes do gram positive bacteria have?
1
eukaryotic lipids
phosphatidylcholine and sterols
prokaryotic lipids
phosphatidylethanolamine (PE), phosphatidylglycerol (PG), cardiolipin, usually no cholesterol
PE is targeted by _
polymyxins
molecules that require active transport
ions, iron, magnesium, calcium (metals), amino acids, sugars, vitamins
efflux pumps allow _
resistance to antimicrobial agents
mycobacteria outer layer
mycolic acid; acid fast
mycolic acid provides _
resistance to detergents, drying, stains, common antibiotics
mycoplasma outer layer
triple-layered lipoprotein membrane with cholesterol
spirochete characteristics
endoflagella/axial filaments, corkscrew-shape, motile, outer membrane
Which spirochetes have LPS?
leptospira
chlamydia life cycle
infectious elementary body (metabolically inactive) –> reticulate body (active) –> after dividing, coverts back to EB
outer membrane vesicles
membrane “blebs” originating from OM of ALL gram-neg bacteria
OMVs contain _
adhesins, toxins, enzymes, sometimes DNA
extracellular vesicles
membrane vesicles produced by gram positives
functions of EVs/OMVs
diffuse and enter spaces too small for whole bacteria, increase toxin delivery, can contain beta-lactamase to increase resistance, transferrable DNA, might fuse with host cells
neisseria gonorrhoeae
utilizes an outer membrane protein that binds to factor H, increasing conversion of C3b to iC3b to inhibit MAC
gram positive bacteria & MAC complex
gram-pos are naturally resistant to lysis by complement due to thick peptidoglycan cell wall; can still be opsonized though
glycocalyx
layer or coating external to the cell wall; includes slime layers, capsules, S-layers
slime layers
amorphous, diffuse, thin group of EC polysaccharides, proteins, lipids
S-layer
defined layer of EC glycoprotein around the cell, just outside of PG layer; usually comprised of single protein
capsules in gram-neg
K antigen
K antigen
extend further out from cell surface and are important virulence factor
capsule virulence properties
antiphagocytic, poorly T cell immunogenic, influence adherence, partially inhibit MAC
capsules as vaccination tools
vaccination using purified capsular polysaccharides is effective against some important bacterial pathogens
major bacterial pathogens with capsule
flu type B, streptococcus pneumoniae, group A & B strep, neisseria meningitidis, salmonella, C. fetus, bacillus anthracis, pseudomonas
which encapsulated bacteria have a vaccine against them?
type B flu, streptococcus pneumoniae, and neisseria meningitidis
endospores
differentiated structures formed by gram-pos bacteria only during nutrient deprivation
what are endospores sensitive to?
steam, sporicidal agents, bleach, glutaraldehyde, peracetic acid, hydrogen peroxide, ethylene oxide
endospore core
genome with protein synthesis machinery, energy, and AA production components
endospore wall
peptidoglycan
endospore cortex
concentric layers of spore-specific peptidoglycan (thickest layer)
endospore coat
keratin-like protein coat with disulfide bonds for chemical strength
endospore exosporum
remnant of mother cell membranes
What is found in all endospores?
dipicolinic acid to protect DNA
endospore germination
activation –> germination –> outgrowth
endospore activation
stimulated by fresh medium, temp change, pH, or age; requires water and triggering nutrient (alanine)
endospore germination
cortex swells as it is rehydrated –> excretes calcium and dipicolinic acid –> loses temp resistance
endospore outgrowth
core enlarges, mRNA synthesis, spore coat ruptures, spore wall expanded to form new peptidoglycan
conjugation
transfer of plasmids between bacteria
antibiotics that target large subunit (50S)
chloramphenicol, clindamycin, macrolides
antibiotics that target small subunit
tetracycline, aminoglycosides
peptidoglycan and disease
sensitive to lysozyme, thick PG is complement resistant, can elicit cytokine response, unique structure allows targeting by antibiotics
capsules and disease
inhibit phagocytosis, poorly T cell immunogenic, partial complement resistance; vaccine target
plasmids and disease
confer antibiotic resistance
flagella and disease
motility, immunogenic, can be important for virulence
LPS and disease
endotoxin shock/sepsis; unique structure; targeted by polymyxin antibiotics
pili and disease
critical for adherence
endospores and disease
resistance to many microbicidal agents; environmental persistence, disease relapse
