chapter 11 pt 2 Flashcards
aminoglycosides
interfere w proteins
-bind to 30s subunit so the mRNA gets misread cause frameshift
-inhibit protein synth
-useful for aerobic gram negativie robs and some gram positive bacteria
which microbes make aminoglycosides
streptomyces and micromonospora
tetracyclines
block protein synthesis by binding to 30S subunit and preventing aminoacyl trna from binding to mrna ribosome complex
chloramphenicol
blocks peptide bond formation and protein synthesis
-synthetic
-TOXIC
why is chloramphenicol toxic?
inhibits mitochondrial ribosomes
macrolides
erythromycin
erythromycin
goes to 50S subunit and prevents ribosome translocation so cant move onto mRNA
erythromycin drugs
-zithromax, azithromycin and z pack
-low toxicity and broad spectrum
fluoroquinolones
bind to DNA gyrase and topoisomerase IV so bacterial DNA cant replicate
fluoroquinolone drugs
-ciprofloxacin
-broad spectrum
why does fluoroquinolone use have to be monitored
because overuse can lead to ciprofloxacin resistant bacteria
what are most drugs that block metabolic pathways?
synthetic
what is the most important metabolic pathway blocker?
sulfonamides/ sulfa drugs
how do sulfas work
-competitive inhibition
-block enzyme needed for folic acid synthesis
-narrow spectrum
-bacteriostatic (stops growth no KILL)
golden age of antibiotics
1940 - 1980
antibiotic classes
penicillins, tetracyclines, macrolides, fluoroquinolones, carbapenems
resistance
reduced effectiveness of antimicrobial drug
how does resistance arise?
genetic versatility, an aquired mutation, intrinsic/ natural resistance mechanism that existed before it was exposed to the drug
example of intrinsic natural resistance mechanism
a gram positive drug can’t affect a gram negativie drug
where are spontaneous mutations coming from?
chromosome genes
-can transfer from species to species bc it comes from resistance factor int he plasmid that transposons
natural selection
eventually the population will be resistant bc the non resistance cells are destroyed
-this does not happen until exposure to the drug occurs
MRSE
methicillin resistant staphylococcus aureus
-resistant to many antibiotics
-most are skin infections in community
MRSA in hospital
life threatening sepsis, pneumonia or surgical site infection
steps to reduce drug resistance
-accurate diagnosis and drug
-compliance to correct dosage for the required time
-multidrug therapy
why should u take the entire dosage of the drug for the right time?
because this will diminish the selection for mutations that can lead to low drug level resistance bc not all pathogens are eliminated
goal of drug research
-short term higher dose antimicrobials that are effective and less expensive with less side effects
possible long term solution to resistance
adding antimicrobials to animal feed worldwide
assay for drugs that are commonly resistant
Kirby Bower disk diffusion test
-will test for resistance
dilution test
minimum inhibitory concentration test to show the smallest concentration of drug that will VISIBLY inhibit growth
MIC
minimum inhibitory concentration
-smallest amount to stop microbe growth
-goal: clear tube
therapeutic index
ratio of the dose of the drug that is toxic to humans compared to its minimum effective dose
what type of index is desired
high index
drug resistant strain found in eye drops
P aeruginosa
-this is NOT all around us
listeria monocytogenes
-gram positive
-doesnt form spores
-short (cocobacilli) or long filaments
-form flagella out of the body (1-4)
-no capsules
what is listeria monocytogens resistant to?
heat, cold, salt, ph, bile
where is listeria monocytogens found
in the fridge
-it is a psychotroph
