Antimicrobials: Protein Synthesis Inhibitors and DNA Distruptors Flashcards by Emma J

List 5 types of antimicrobials that are proteins synthesis inhibitors

phenicols

macrolides

lincosamides

aminoglycosides

tetracyclines

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What is the mechanism of action of tetracycline

uptake by bacteria via an energy dependent mechanism that animal cells don’t do

they bind ribosome (30S) and interfere with tRNA binding

reversible binding to ribosome

Preferential for bacterial ribosomes

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What are the general characteristics of tetracycline drugs

bacteriostatic

time dependent

named after the number of carbon rings

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What are 3 mechanisms bacteria have developed to build resistance to teracycline drugs

efflux pumps

alter targets (30S structure)

develop enzymes to degrade the antibiotic

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How are tetracycline drugs administered

IM
IV
PO

depends on the drug

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What are the pharmacokinetics for tetracycline drugs

varied absorption
- lipophilic

doxycycline is more lipophilic vs oxytetracycline

varied protein binding and excretion

doxycycline = GI excrete
oxytetracycline = renal excretion

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What bacteria are tetracyclines effective against

gram (+) aerobes

gram (-) aerobes (not pseudomonas)
- more effective against resp than enteric

good against (+) and (-) anaerobes

= broad spectrum

also ricketts/mycoplasma/erlichia

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What are the adverse effects of tetracyclines

teeth discolouration
reduced bone growth in young

fever = cat

hepatotoxic = rare

Nephrotoxic at high doses

will cross placenta and enter milk
- can alter neonate development

hypotension and collapse if you give it IV too fast
- give slowly
- reduced Ca in heart

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What is oxytetracycline used for mainly

large animals

pneumonia
metritis
footrot
potomac horse fever
tendon contracture in neonates
keratoconjunctivitis (moraxella bovis)
chlamydia abortus (sheep)

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What causes potomac horse fever? What are the clinical signs

ingestion of snails infected with neorickettsia risticii

causes diarrhea, fever, laminitis

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How is potomac horse fever treated

IV oxytetracycline diluted in saline

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What causes tendon contracture in neonates and how is it rectified?

shortening of the check ligament

treat with a splint and oxytetracycline (give slowly and diluted SID for 1-3d)
- makes tendon more pliable

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What are 4 adverse effects of oxytetracycline when treating tendon conracture

nephrotoxicity - ensure well hydrated

rhabdomyolyisis - can impact mitochondria

tooth discolouration

impact growth and healing

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What class drug is oxytetracycline

class 3
- resistance is common

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How does ocytetracycline compare to macrolides

macrolides: long lasting but higher risk of multidrug resistance
- class 1 drug

oxytetracycline: shorter acting but can repeat treatment if needed
- lots of resistance exists

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How is doxycycline administered? What is it mainly used for?

PO or IV in small animals
- NEVER IV to horse

tx
vector borne diseases
- erlichia canis
- borrelia burgdorferi
- rickettsia
- mycoplasma haemofelis

myoplasma

chlamydia

kill heartworm

anti-inflammatory
- chronic rhinitis in cats

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What are the pharmacokinetic sof doxycyline

feces excretion
- cannot treat UTI but also doesn’t impact renal failure

more lipophilic vs ocytetracycline

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What is an adverse effect of doxycycline given PO

can cause esophageal strictures in cats

ensure you are giving with lots of water or food

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How does doxycycline treat heartworm

Heartworm has a symbiotic bacteria (wolbachia)

kills wolbachia = kill heartworm

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How does doxycycline have anti-inflammatory effects

inhibits
- matrix metalloproteinase
- neutrophil activation
- t cell proliferation

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What is the mechanism of aminoglycosides

premature termination of proteins chains via irreversible binding to 30S ribosome

enters gram (-) via porins and are actively transported through the inner membrane (need O2)

displaces Ca and Mg in biofilm and disrupts polysaccharide crosslinks

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What are the general characteristics of aminoglycoside drugs

bactericidal

concentration dependent

oxygen dependent

inactivated by
- low pH
- organic debris
- combination with other drugs

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What bacteria are aminoglycosides effective against

good against gram (-) aerobes

good in combination with penicillin

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What are the pharmacokinetic properties of aminoglycosides

not absorbed in GI and dont cross tissue barriers
- do not enter BBB or prostate
- large and ionized

not protein bound

accumulate in the renal cortex
- excreted via glomerulus
- resorbed in the proximal tubule
- can cause violative residues 1 year post administration

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What animicrobials can you not give to production animals

aminoglycosides - long renal residues chloramphenicols - aplastic anemia metronidazole - carcinogenic and teratogenic

What are the adverse effects of aminoglycosides

nephrogenic (accumulate in cortex and destroy proximal tubules) otogenic - accumulate in inner ear - dogs = auditory dysfxn - cats = vistibular - may be irreversible

List 3 types of aminoglycosides

tobramycin gentamycin amikacin

Compare gentamycin and amikacin

similar amikacin has a wider spectrum of action (more gram (+) efficacy) and less resistance gentamycin has less ability to cross cell membranes = lower volume of distribution - not good intrauterine or PO - can cause ciliary ablation in the eye = glaucoma tx

What is gentamycin and amikacin used for? How are they administered

IV IM SC regional imb perfusion interarticular

What is the mechanism of action of macrolides and lincosamides

bock polypeptide exiting 50S and prevent selongation macrolides and lincosamides have the same mechanism of action and will compete against each other

What are the general characteristics of macrolides and lincosamides

bacteriostatic time dependent

What bacteria are macrolides and lincosamides effective against

gram (+) and respiratory gram (-) better efficacy at higher pH accumulate in immune cells and at the site of infection

What adverse effects are associated with macrolides and lincosamides

few dont bind mammal ribosomes

List 4 types of macrolides

tulathromycin tilmicosin azithromycin clarithromycin

What species is tulathromycin and tilmicosin used for? What bacteria is it effective against

production animal gram (-) and enteric/resp pathogens some cytochrome P450 metabolism prokinetic

What is one consideration to have in mind when working with tilmicosin

cardiotoxic to horses, sheep, goats, humans - death

What is the relative efficacy of azithromycin and clarithromycin compared to tulathromycin and tilmicosin

they have more gram (+) than gram (-) activity

List 2 types of lincosamides

lincomycin clindamycin

What animals are lincomycin and clindamycin used in? What bacteria is ti effective against?

SA and pigs good against all EXCEPT gram (-) aerobe

What are 2 considerations to have when giving lincomycin and/or clindamycin

NOT for horses, ruminant, hamster, guinea pig - fatal colitis clindamycin tablets can cause esophageal injury

What is the mechanism of action of phenicols

bind 50S subunit chloramphenic also inhibits mammal protein synthesis - impacts the bone marrow

What are the general characteristics of phenicol drugs

bacteriostatic time dependent

What bacteria are chloramphenicol effective against?

broad spectrum effective against MRSA NOT pseudomonas

What is the pharmacokinetics of chloramphenicols

good absorption and distribution can give PO to horses

What is an adverse effect of phenicol drugs

cause fatal aplastic anemia - can occur in humans = wear PPE

How does florphenicol compare to chloramphenicol

does not cause aplastic anemia but it has less efficacy

What bacteria is florphenicol effective against

gram (-) anaerobes

What is florphenicol used for

ruminant and swine respiratory disease small animals NOT horses = colitis

Name one nitroimidazole

metronidazole

What is the mechanism of metronidazole

makes short lived intermediates and ROS in bacteria/protozoa destroys DNA

What are the general characteristics of nitroimidazoles

concentration dependent bacteriocidal

What is the efficacy of metronidazole

anaerobe protozoa (giardia)

How is metronidazole administered

PO tastes bad

What is metronidazole used for

dog/cat/people = giardia tx antiinflammation in GI

What are the adverse effects of metronidazole administration

tastes bad changes GI microbiome causes neuropathy reduces appetite

What is the mechanism of action of fluoroquiniolones

inhibit bacterial DNA gyrase (unwind DNA) = prevents DNA replication - it iinhibits it at lower concentrations than it would like to inhibit mammal DNA gyrase also inhibit topoisomerase 4 (separate daughter chromosomes)

What are fluoroquinolones effective against

good gram - varied gram + pseudomonas!

What are the characteristics of fluoroquinolones

bactericidal concentration depndentt higher risk of multidrug resistance - will predispose to itt accumulates intracellularly

What category drug are fluoroquinolones

Category 1 (high human importance)

What are the pharmacokinetic characteeristics of fluoroquinolones

good PO absorption - can be given topical - giving IV is extra label: will precipitate in fluids (use separate lines and give slow) will penetrate CNA/prostate and accumulates in the urine

What are the adverse effects of fluoroquinolones

no extralabel use in production animals arthropathy (cartilage damage) in young animals enters milk cats = retinal toxicity = bliiind - they are deficient in BRCP efflux protein in the retinal cells seizure in predisposed animals

Give 1 example of fluoroquinolones

enrofloxacin (baytril)

What mechanisms of resistance are there against fluoroquinolones

change target enzyme altere influx and efflux plasmid mediated resistance allows fast resistance development and spread

What are 3 ways to mitigate AMR against fluoroquinolones

dont usee mass medication- metaphylaxis use when supported by C/S use on individual basis