Antimicrobial Chemotherapy Flashcards
what are antimicrobial chemotherapeutics
chemicals we put in/on our body to treat disease
MLC vs MIC
MLC - minimum lethal concentration
= minimum amount of antibacterial required to kill a pathogen
MIC - minimum inhibitory concentration
= “ required to stop growth of a pathogen
narrow vs broad spectrum antimicrobials
narrow - target specific species
broad - targets larger classes of organisms ex. all bacteria / gram -
selective toxicity
trade off
toxic enough for bacteria but not human cells
etest strips
strip infused with a gradient and antibiotic along their length and placed on bacterial lawn
MIC is where the zone of inhibition ends
antibacteria ___ harm viruses. what should you use and what do they do
don’t harm viruses
- use antivirals which target enzymes involved in viral replication
what are in fungal cells that enable antifungals to be effective
have chitin in cell wall
& ergosterols in cell membranes
what is a chemical adjuvant
substance used in combination with an antigen (vaccine) to enhance the immune response
are archaea pathogenic?
no
what are the 4 options for microbial resistance mechanisms
- prevent drug from entering cell
- excrete drug before it takes effect
- degrade/inactivate drug
- change drugs target
how can microbes stop the drug from entering the cell
- what helps microbes do this
- stop it AT the cell membrane/ cell wall
- stop it from accessing the cell membrane/ cell wall
- biofilms = thick slime layers
how can microbes excrete drugs before they take effect
efflux pumps
~need ATP
how can microbes degrade drugs
B-lactamase enzyme
- breaks open the B-lactam ring of the antibiotic structure so cannot damage bacterial cell wall now
*leaks into the enviro, gives neighbouring cells protection
what is a common antimicrobial that microbes became resistant to
Polymyxin B
- targets gram negative bacteria
~ binds to lipid A (component of LPS) and disrupts the outer membrane, making it leaky
microbes become resistant to polymyxin
2 mechanisms of microbial genetic variation
- vertical gene transfer
- horizontal gene transfer
- transformation
- conjugation
- transduction
describe vertical gene transfer in microbes (mutations)
- mutations
~from UV light/chemicals
bacteria are prone to mutations / helps them adapt quickly / have mutator genes
VGT occurs in (3)
prokaryotes, eukaryotes and viruses
what is transformation
uptake of naked DNA from the environment into its own genome
- only competent cells can do this (have special surface receptors that bind and import the DNA)
what is conjugation
bacteria sex
- direct contact between two cells
gram - attaches to recipient cell via a sex pilus
gram + forms a conjugation bridge with other cell
*plasmid is replicated via rolling circle replication
generalized transcduction
can move ANY gene from the donor bacteria
- during lytic cycle of a phage
- random piece of bacterial DNA is packaged into phage head
- infected bacteria and injects the bacterial DNA
specialized transduction
can only move genes NEXT to the insertion site
- happens during lysogenic cycle
- during excision the phage sometimes takes nearby genes with its own & creates hybrid phages = carrying adjacent genes from the original host
antibiotic (penicillin) arms race
antibiotic - resistance- countermeasure - new resistance - new countermeasure
-first antibiotic = penicillin
*B-lactamase can now break down penicillin
-countermeasure = B-lactamase inhibitor so penicillin can work again
-new resistance = some bacteria have BLI effluc pumps / able to break down penicillin again
why should you always finish your antibiotics (3)
- not all bacteria die at once
- avoid getting infection again
- prevent bacteria having the chance to adapt and become resistent to drug
