exam 1 Flashcards
what shape is bacillus
rod
what shape is coccus
spheres/ round
what shape is spirochete
flexible, thin, spiral-shaped rod
what shape is spirillum
rigid, spiral-shaped rod
what are pleomorphic bacteria
no defined shape, variety of shapes in one species
what is diplo
pair
what is strepto
chain
what is staphylo
grape-like cluster
what is tetrads
packets of 4 cells
what is sarcina
packet of 8 cells
what are the three main types of cell walls that bacteria have
gram-negative
gram positive
acid-fast
what are the main components common to all three cell wall types of bacteria
peptidoglycan
lipoprotein
(provide structure support)
what is the peptidoglycan layer made up of?
backbone
tetra peptide side chains
peptide cross-bridge
what are the antimicrobial enzymes found in secretions and granules of peripheral mononuclear cells? and what is their function?
lysozymes
-weakens the cell integrity
do gram positive bacteria have a thick or thin peptidoglycan layer
thick
do gram negative bacteria have a thick or thin peptidoglycan layer?
thin
what is the primary stain
crystal violet
what is the counterstain
safranin
what color are gram negative cells
they retain the counter stain so they are red
what color are the gram positive cells
they retain the primary stain and stain purple
what is the periplasmic space
space between the inner and outer membrane
what is a distinct component of the outer layer of gram negative cells
lipopolysaccharides (LPS)
LPS is also known as
endotoxin
what structures is the LPS composed of
O antigen
core polysaccharide
lipid A
what does the O antigen serve a purpose for in the LPS
serves as attachment sites
what does the lipid A serve a purpose for in the LPS
virulence factor of LPS
-this is the part responsible for the endotoxic activity
what are the two key components unique to gram positive bacteria
teichoic acid (WTA)
lipoteichoic acid (LTA)
what is the function of WTA/LTA in gram positive cells
allow for adherence of bacterial cells to host cells
what does teichoic acid adhere to
peptidogylcan
what does lipoteichoic acid adhere to
anchors to cell membrane
when an host is infected with a gram negative bacteria cell what can WTA/LTA initiate
WTA/LTA along with peptidoglycan can initiate endotoxin-like activities when released upon bacterial lysis
-but not truly an endotoxic reaction
what are structures that are unique to the acid-fast bacteria cell wall
mycotic acid layer (outer)
tetrameric porins
what is the function of mycolic acid layer of acid-fast bacteria
waxy coat
-provide resistance to desiccation, some antibiotics and inhibits phagocytosis
what are the two clinically relevant genera that are acid fast
mycobacterium
nocardia
what is the primary stain for acid-fast bacteria
carbolfuchsin
(acid-fast=red)
what is the counterstain for acid-fast bacteria
methylene blue (nonacid-fast=blue)
what is the point of the hot plate for an acid fast stain
to open that waxy coat to allow the stain to penetrate the cell to color
a foal was diagnosed with endotoxemia caused by endotoxins released into the bloodstream. the bacterial cell wall structure causing the patient’s symptom is what?
lipid A
a stained tracheal mucus specimen was collected from a cattle shows acid-fast bacilli. what genera should be included in your differential diagnosis?
mycobacterium
what are two forms of glycocalyx
slime layer
capsule
what is the function of glycocalyx
-promotes adherence of bacteria to surfaces to biofilm formation
-protects against desiccation
-acts as barrier to toxic hydrophobic molecules- antibiotics
-inhibits phagocytosis
function of slime layer of glycocalyx
protects bacteria cells from environmental dangers such as antibiotics and desiccation
what is the test quelling reaction used for
to determine whether bacteria have a capsule or not
describe how the quelling reaction works
antigen-antibody reaction causes a change in the refractive index of the capsule so that it appears “swollen” and more visible
what are the three major components of flagellum
filament
hook
basal body (anchor flagellum in cell membrane)
what protofilaments are each flagellum made up of?
composed of flagellin (H antigens)
-highly antigenic
what are the two main classes of pili
-ordinary/common pili
-sex pilus/conjugated pilus/F pilus
what does ribosome consist of
mRNA
protein
what are bacterial ribosomes made up of
50S and 30S subunits
ribosomes are important and are good for antimicrobial activity
:)
importance of inclusion bodies (internal structure)
various granules, vesicles and vacuole within cytoplasm
-can aid in identification of some bacteria
properties if endospores
core
spore wall
cortex
coat
exosporium
sporulation vs vegetative growth
-vegetative growth: a single endospore will create two daughter cells
-sporulation: go through process to make a spore coat and then a spore and the spore then gets activated from resting stage once there is lack of nutrients or something
two clinically relevant genera that produce endospores
bacillus
clostridium
what pH are transport media and culture media buffered at
~7.0
explain oxygen requirement for facultative anaerobes
no oxygen requires but will used if there is any available
do aerotolerant anaerobes require oxygen
no oxygen required and can tolerate some oxygen because it has reactive oxygen species (ROS), which knock out other reactive oxygen
what type of bacteria are capnophiles and where do they commonly reside
microaerophiles
-cheek/mouth is favorable area bc requires some CO2
what is an example of species that resist desiccation
staphylococcus spp
what is an example of species that can desiccation and needs transport media
haemophilus
what bacteria do not require NaCl but can grow under saline conditions (increase osmotic pressure)
halotolerant bacteria
what are chemohetertrophs
using organic compounds as sources of energy and carbon
what are fastidious bacteria
requiring additional organic compounds in their culture media (vitamins, aa)
what are solid media used for
isolation of pure cultures (agars)
-estimate the number of viable bacteria in a sample
-colony characterization can be used for microbial ID
what is a colony
population of cells arising from a single cell or spore, or from a group of cells of the same species or strain
what are liquid media (broths) used for
ideal for growing large numbers of bacteria (can’t actually visually determine number of species present)
what are semi-solid agars used for
determining motility, growing microaerophiles, some transport media
*agar is a solidifying agent, NOT a nutrient
man said its gonna be on exam
what is basal media and what are some types
sustain growth of less fastidious bacteria
-nutrient agar, nutrient broth, tryptic soy agar
what is enriched media and what are some types
basal media + additional nutrients (eg blood, egg yolk) used to cultivate fastidious organisms
-blood agar, chocolate agar
what is selective media and what are some types
reagents (dyes, NaCl) added that inhibit the growth of unwanted bacteria while allowing the growth of others
-MacConkey agar, mannitol salt agar
-so like selecting for gram + over gram - (give a favorable environment for the thing you are looking for)
what is a differential (indicator) media and what are some types
contain component (dyes, pH indicators) that allow the differentiation of closely related taxa based on apprearance (color) of the colony or surrounding media
-MacConkey agar, mannitol salt agar, blood agar
why would you not want nutrients in a transport media
some bacteria will overgrow and outcompete the other microbes and that will distort the ratio of microbes that are in there or prevent you from isolating the microbe that may be the causative agent of the problem being dealt with
how would you grow rickettsia spp an obligate intracellular bacteria
-grown in animal cells
how would you grow an extracellular bacterial pathogen such as mycobacterium leprae
best grown in a host organism
what is a pure culture
contains only 1 species (or strain) of microbe
what are the goals of preservation of maintaining a pure culture
viability
purity
genetic stability
preservation techniques if bacterial cultures
-subculture of growing cells
-snap-freeze in broth w cry-preservative
-freezr-dry cells suspended in lyophilization medium
generation time
time required for population to double
after the decline phase of bacteria growth, what can some bacteria enter
a longterm stationary phase that can last for years
when growth on a solid media is occurring what phase are the cells in center at
-cells at center are at stationary phase (zero population growth, near death)
-where as the cells on the edge are going through exponential growth
pathogenicity
the ability of microbe to damage a host
virulence
the relative capacity of a microbe to cause damage in a shot
infectivity
the capacity of a microbe to become established in a host
virulence factors
traits that confer pathogenicity (e.g. toxins)
genes coding for virulence factors
-generally expressed facultatively
-unevenly distributed among strains of a species
-often spread by horizontal gene transfer
-often clustered into pathogenicity island
what do adhesions bind to
complementary receptor molecules found on target host cells/tissues
-highly specific
-receptor-ligand interaction
what does adhesion attachment specificity help bring about
-tissue tropism
-host specificity
what does lipid A stimulate
systemic inflammatory response
what are the 3 main portals of entry
GI
respiratory
urogenital
what does the chemical siderophore that bacteria has on board do?
used to steal iron from iron-binding proteins
biolfilms facilitate quorum sensing which allows what
allows biofilm inhabitants to coordinate their cellular activities (e.g. exotoxin production)
what do the enzymes invasins do
local damage to host cell and ECM
-spread beyond colonization sites
how can invasion of epithelia barriers be breached?
-parcellular route (between epithelial cells)
-trancellualr route (through the epithelial cells)
4 ways pathogens damage hosts
-use host nutrients
-cause direct damage near colonization site
-produce toxins tha damdge sites distant from invasion site
-pathogens cause collateral dandle due to host inflammation or immune reactions
subclinical (inapparent) infection
does not cause any noticeable illness
what are the 4 types of carriers
passive
incubatory
convalescent
active
what is a mutant
-offspring of a “normal” member of a species
-genetically distinct from “wild type” in some way
isogenic strains
two lineages of the same bacterium that have a single change
does the use of antibiotics create mutations that lead to resistance?
-mutations occur naturally
-adding antibiotics select for mutations that already exist in the body
selection mutation
a growth condition that allows for growth of only a specific kind of mutant
spontaneous mutations
occurring by inserting of incorrect base during replication
induced mutation
addition of external factors (mutagens) that later chemical bonds in DNA and need repair
what are the three types of mutations
-silent or synonymous mutations
-missense or non synonymous mutations (change of aa)
-null mutation (loss of function)
does a nonsynomymous mutation always lead to a change in phenotype?
it depends on what is being mutated, where the amino acid is, and other factors
what is prokaryotic polycistronic
multiple genes (protein coding sequences) on one mRNA
what is eukaryotic monocistronic
one gene (one protein coding sequence) on a mRNA
transcription termination in bacteria
-use factor dependent (Rho) and that binds to rut sites on mRNA molecules and it follows and treads the mRNA through a pore/loop until its bumps into mRNA polymerase and bumps it off the DNA
what are nonsense mutations
mutations that change from coding an amino acid to coding for a stop codon
what is frameshift mutations
base deletions or additions that alter the reading frame of the mRNA
horizontal gene transfer
moving large chunks of DNA, not from mother to daughter cells, but from amoungst species ( e.g. e coli to salmonella)
what is vertical gene transfer
DNA replication provides daughter cell with copy of parental cell DNA
natural competence
to take up DNA from the environment
-strephococcus pneumoniae
-neisseria gonorrhoeae
-haemophilus influenzae
how does natural transformation/ competence occur in gram negative and positive cells
DNA uptake occurs by the translocation of ssDNA molecule into the cell
what is quorum sensing
bacteria communication
relays number of cells in an environment based on a secreted protein or product
what does the build up competence stimulating peptide CSP cause
quorum sensing leads to the induction of competence
fratricide
killing of neighboring non-competence cells as source for DNA
process of horizontal gene transfer
transformation
transduction
transposition
conjugation or mating
what does transduction of bacteria used bacteriophage for
-bacteria viruses, injecting DNA into host cell
-specialized transduction, small amount of DNA into adjacent cell
-generalized transduction, transfusing phage
spcialized transduction vs generalized transduction
-specilaized transduction is when bacteriophages transfer specific bacteria genes located near page DNA in bacterial chromosome
-generzalized transduction is when phages randomly package bacterial DNA and transfer it to another DNA cell
lytic growth
phage replicates
lysogenic growth
phage silently inserts into bacterial chromosome and be replicated by cell division
-prophage (or lysogen): lytic genes repressed viral DNA remains silent in host
what is transposases
the enzyme that cuts DNA and allows transposons to insert
copy and paste
composite vs noncomposite transposons
-composite are large transposable elements that a typically carry antibiotic resistance markers
-noncomposite have inverted repeats and resistance markers
bacterial mating or conjugation
transfer of DNA from donor to recipient cell
F plasmid is a self-transmissivle plasmid and encode tra genes
idk man
tra two main functions of F plasmid
Dtr- DNA transfer and conjugal replication
Mpf- mating pair formation
conjugal F plasmid transfer process
-mating pair established
-single strand of DNA transferred
-DNA replication occurs in both donor and recipient cell
pathogenicity islands
horizontally acquired sections of bacterial chromosome that encode genes primarily associated with virulence
germ theory of disease
proposing that microorganisms cause disease
what was the first effective treatment for syphilis
arsphenamine (salvarsan)
narrow spectrum antibiotics
effective against a limited number of bacteria
broad spectrum antibiotics
effective against wider array of bacteria
cons of broad spectrum agents
increased development of resistance, disruption of microbiome
-it clears out and makes room for more bacteria to form and the ones left over are the resistant ones will flourish in that environment
bactericidal antibiotics do what
kills
bacteriostatic antibiotics
inhibits growth and allows for the immune system to get rid of the bacteria
-this also allows the body to develop antibodies against the bacteria
if you have an immunocomprosmied patient would you want to use a bactericidal or a bacteriostatic antibiotic
you would want to use a bactericidal because the patients wouldn’t have an functioning immune system to fight off the bacteria for bacteriostatic
selective toxicity
antibiotic specific for bacteria and not host cells
-should not be toxic to host cells (make sure its not toxic to certain species)
what properties are important for an effective antibiotic
-selectie toxicity
-soluble in body fluids
-toxicity not easily altered
-nonallergenic
-stability
-bacterial resistance not acquired
-resonable cost
five classes of antibiotics
-inhibition of cell wall synthesis
-disruption of cell membrane function
-inhibition of protein synthesis
-inhibtioin of nucleic acid synthesis
-action as antimetabolites
what does the antibiotic beta lactams target on the bacteria
they target enzyme responsible for making cross-link (block transcriptase enzyme)
what does the antibiotic vancomycin target on bacteria
they target side chains which normally aid in cross-linking
what does the antibiotic bacitracin target on bacteria
they target flipase enzyme
cephalosporins and penecillin is what type of antibiotic
B-lactam
the antibiotics that are inhibitors of cell wall synthesis, B-lactams, vancomycin, bacitracin are what type of antibiotics
bactericidal
-these are most effective
mode of action for vancomycin antibiotic
glycopeptide antibiotic
-binds to end of the pentapeptide chains on NAM blocking the transglycosylation and transpeptidation steps of peptidoglycan
mode of action for bacitracin
-topical for toxicity
-prevetns dephosphorylation of bactoprenol (lipid carrier), preventing assembly and transport of NAG-NAM
-carrier molecule
mode of action for polymyxin antibiotic
-topical or ophthalmic use
-distrupts cell membrane
-acts as cationic detergent, disrupting membrane structure
what type of antibiotic is amino glycoside and what is the mechanism of action
-30S ribosome subunit inhibitor
-irreversibly bind to to 30S subunit and block the initiation complex, causing misreading and premature release of mRNA from the ribosome, halts protein synthesis
toxicity of ahminoglycosides
ototoxic and nephrotoxic to cats and dogs
what type of antibiotic is tetracyclines and what is the mode of action
-30S ribosome subunit inhibitor
-binds to the 30S subunit to prevent attachment of the aminoacyl-tRNA to the RNA-ribosome complex
what type of bacteria is amphenicol and what is the mode of action
-50S ribosome subunit inhibitor
-binds to the 50S subunit, inhibiting peptide transferase
what is the chloramphenicol toxicity
-type of amphenicol
-toxic to human mitochondria, associated with aplastic anemia in humans and may cause reversible bone marrow suppression in animals, cannot use *chloramphenicol in food animals
what type of antibiotic is macroliodes and what is the mode of action
-50S ribosome subunit inhibitors
-binds to the 50S subunit, blocking formation of the initiation complex and translocation
what type of antibiotic is lincosamides and what is the mode of action
-50S ribosome subunit inhibitor
-binds to the 50S subunit, disrupts protein synthesis
what are cautions of using lincosamides
-toxic to rabbits, guineas, and hamsters
-contrainidicated in horses and neonatal animals, oral administration is hazardous in animals
what is the mode of action for streptogramins
bind to different sites on the 50S ribosomal subunit, inhibition of protein synthesis at different steps
what is the mechanism of action of quinolones/ fluoroquinolones
-inhibitors of nuclei acid synthesis
-bind to inhibits DNA gyrase (topoisomerase II) and topoisomerase IV, preventing bacterial DNA from unwinding and duplicating
what is the mechanism of action of rifamycins
-inhibtiors of nucleic acid synthesis
-inhibtis DNA-depenent RNA polymerase
-prevents transcription of messenger RNA (mRNA)
what is the mechanism of action for metronidazole
covalently binds to DNA and chops it off, causing breaks
mode of action for sulfonamides and diaminopyrimidines
interferes with folic acid synthesis (needed for DNA synthesis)
-action as antimetabolite
sulfonamides are competitive inhibtiors what what
dihydropteroate synthetase
trimethoprim inhibtis what enzyme
dihydrofolate reductase
what is antibacterial resistance
the ability of bacterium to survive and multiple in the presence of an antibiotic
innate (intrinsic) resistance
innate ability if a bacterial species to resist the acidity if an antibiotic through its inherent structural or functional characteristics
acquired (extrinsic) resistance
organism obtains the ability to resist the activity if an antibiotic to which it was previously susceptible
what are the mechanisms of action to prevent actions of antibiotics
-preventing the antibiotic from reaching its target (1-3)
–modifying or bypassing the antibiotic target (4-5)
how is bacteria able to reduce the ability of the antibiotic to enter the cell
antibiotics that are unable to gain access into the bacterial cell will not be able to reach their intended target so they do ti by altering porins in the cell wall
how is bacteria able to expel the antibiotic out of the cell via efflux pumps
some bacteria possess membrane proteins that can export or pump out antibiotics as fast as they enter the cell which decreases antibiotic concentration inside the cell
how is bacteria able to inactivate by modifying or degradation
some bacteria have enzymes that can degrade or modify an antibiotic structure
ex B-lactamases
B-lactamase inhibitors
-used in combo with B-lactam antibiotic to extend the activity spectrum of the antibiotic
-function to inhibit the activity of B-lactamase
how is bacteria able to modify antimicrobial target
bacteria have acquired mutations or modified structures that no longer are recognized
how is bacteria able to bypass the antibiotic target
some bacteria have acquired a “new” enzyme that allows bypass of a metabolic pathway
wise use of antibiotics
-prescribe antibiotics only for bacterial infection
-educate clients to compete course bc if not you didn’t eliminate all the bacteria and give those left a chance to flourish in that environment
-try to determine most appropriate antibiotic for the infection
