LECTURE 3 Flashcards
(22 cards)
what are endospores?
what are the characteristics?
what are they surrounded by?
where do they develop?
when bacteria runs out of nutrients, converts to stable form
dormant
resistant to damaging conditions or agents (heating, freezing, drying, radiation, disinfectants)
resistant to antibiotics
thought and highly impermeable coating
develop inside the bacteria cell
what is a selective media?
examples of selective substances?
contain variety of bacteria
have a substance that inhibits or prevents growth of SOME species but not others
salt, bile salts, dyes (crystal violet), antibiotics
what is a growth media?
what does it contain?
distinguishes one bacterial species from another
dyes, chemicals, non heated blood–> blood agar
how does beta and alpha hemolysis happen in growth media?
b: by srepotoccocus pyogenes–> forms pore toxins which punches holes thru RBC
a: pneumoniae–> peroxided productions , Hb becomes oxidized
what is an example of selective and differential medium?
contents?
what does it do?
MacConkey agar
bile & violet–> inhibit growth of gram pos, so only gram neg
lactose and red–> acid generated when lactose is fermented, so if lactose fermenting species is there, it will turn bright red
used for urine tests
what are examples of bacteria that divide by binary fission?
neisseria–> diplococcus
streptococcus–> long chains
staphylococcus–> grape cluster
how are bacterial infections identified?
gram staining
growth on media
biochemical test
immunological–> antigent test
nucleic acid base (PCR)
protein detetction (MS)
what is differences between bactericidal and bacteriostatic?
bactericidal–> kills bacteria
static—> inhibits growth of bacteria
what is broad spectrum antibiotics?
affect wide range both gram Neg and pos bacteria
important for lift threatening diseases
disrupt normal microbiota
what is narrow spectrum antibiotics ?
target small range
need specific pathogen
less disruptive
what are the major targets of antibacterial drugs?
cell wall synthesis (vancomycin and B lactams)
nucleic acid synthesis
cell membrane
metabolic pathways
protein synthesis
what is mechanism of vancomycin?
how does it become resistant?
only on gram pos
binds to end peptide on Nam–> prevents cross linking of the peptide chain to NAM neighbors
resistant: replace terminal aa of NAM with another aa, so vancomycin can no longer bind
what do anti ribosomal (protein) antibiotics do?
are these selective?
Second largest class*
affect protein synthesis–> block intitation, elongation
yes–> structural differences between ribosomes of host and bacteria cells
how does disc diffusion test work?
spread bacterial isolate on agar & place disc with antibiotics on it
incubate—> if suseptical, there will be a zone of inhibition, if not, no zone of inhibition
what mechanism does B lactams (penicillin) use?
how does it become resistant?
inhibits peptidoglycan synthesis
binds to and inhibits PBPs and peptidoglycan transpeptidases
without their function–> there is no catalyzing of peptide bonds between glycan strands
inactivate B lactamases–> which break the B lactam ring
why is inhibiting peptidoglycan cell wall styntheis good?
weakens the cell wall–> lysis
bacteria only contains this–> so specific
what are adverse affects of antibiotics?
allergy, toxicity, suppression of normal microbiota
what are common mechanics by which bacteria become resistant?
how does this happen?
synthesis enzyme that break down drug–> inactivation
efflux pumps–> rapid elimination
mod of target
decreased uptake
outermsmbrane of gram negative can block entry ( gram neg is more resistant than gram pos)
spontaneous mutation
acquisition of resistant genes
Why are some potential reasons for antibiotic resistance spreading throughout the
world, and what are the implications for medical use of antibiotics?
over and misuse of antibiotics, like in animal feed
one day there might be no proper treatment for bacterial infections
what is pasteurization?
does it destroy endospores?
brief heat under boiling to reduce microbes and kill pathogens
does not kill endospores
what are autoclaves?
pressurized steam–> sterilization
above boiling and kills microbes and endospores
how are heat sensitive liquids sterilized?
filtration, but does not remove viruses
