Term
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Definition
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Term
|
Definition
| competes for Asite of ribosome with tRNA |
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Term
|
Definition
| mismatch of codon:anticodon = misreading = dysfunctional protiens |
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Term
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Definition
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Term
|
Definition
| premature termination of peptide chain |
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Term
| macrolides and lincosamides mech = |
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Definition
| inhibit translocation of ribosome along mRNA |
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Term
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Definition
| inhibits DHPS = inhibit synth of folic acid |
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Term
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Definition
| inhibit DHFR = = inhibit synth of folic acid |
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Term
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Definition
| inhibit DNA gyrases re-annealing ability = fragmented DNA |
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Term
| what kind of surgery would you use Abs prophylactically? |
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Definition
| bone surgey as bone infection hard to tx |
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Term
| shouldnt use cidal and static drugs togther, why? |
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Definition
| static drugs block cidal drugs |
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Term
| polymers of bacterial cell wall = |
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Definition
|
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Term
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Definition
| ...peptide crosslinking and tertrapeptide side chains |
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Term
| what drug inhibits crosslinking of peptides to tetrapeptide side chains? |
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Definition
beta lactam
(inhibits transpeptidation/ peptidoglycan synth/synth of cell wall)what is essj |
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Term
| what drug inhibits crosslinking of peptides to tetrapeptide side chains? |
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Definition
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Term
| what is essential for beta lactam to have antibacterial activity? |
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Definition
|
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Term
| what makes bacteria resisitant to beta lactam? |
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Definition
| beta lactamase (destroys ring structure = makes drug inactive) |
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Term
|
Definition
amoxycillin and ampicillin (v. common in vetmed)
penicillin
cephalosporin |
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Term
| what can you give with beta lactams to inhibit beta lactamase? |
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Definition
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Term
|
Definition
| clavulonic acid + amoxycillin |
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Term
| advantages of semi-synthetic penicillins = |
|
Definition
incr stability to acids
decr beta lactamase susceptibility
incr activity against gram - bacteria |
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Term
| penicillins distribution = |
|
Definition
| widely distributed but doesnt cross BBB as its a weak acid |
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Term
| elimination of penicillin = |
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Definition
rapid (active elimination by kidneys as its a weak acid)
=short half life |
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Term
| how can you improve short half life of penicillin? |
|
Definition
| give procain Pen = counter ion to make it insoluble = when inject acts a a small depo of penicillin which is slowly released over 2-3days =overcome rapid elimination |
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Term
| admin of cephalopsorins = |
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Definition
| some can be given orally, most given parenterally |
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Term
| distribution of cephalosporin = |
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Definition
| widely distributed, some cross BBB |
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Term
| elimination of cephalosporin = |
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Definition
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Term
| adverse reactions of beta lactams = |
|
Definition
1. idiosyncratic hypersensitivity reactions (more common with penicillin in dogs, horses & humans - 2nd admin = been immunised = get reaction)
2. GI upset due to change in gut flora
3. superinfection |
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Term
| beta lactams contraindicated in what sp? |
|
Definition
| gpigs and hamsters as superinfection is fatal in these sp. |
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Term
| drugs that inhibit bacterial protein synth = |
|
Definition
tetracyclin (compete for Asite with tRNA)
aminoglycosides (misreading of message)
chloramphenical (inhibit transpeptidation)
puromycin (premature termination of peptide chain)
macrolides (inhibit translocation of ribosome along mRNA) |
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Term
| selectivity of tetracyclin = |
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Definition
| largely thorugh selective uptake by active transport into prok. cells |
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Term
| which antibacterials is water soluble? |
|
Definition
aminoglycoside
Sulphonamide & trimethorpim |
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Term
| which antibacterial is lipid soluble? |
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Definition
|
|
Term
| give 3 examples of aminoglycosides and how do you admin them? |
|
Definition
streptomycin (IM)
neomycin (oral)
gentamycin (IM) |
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Term
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Definition
misreading of translocation = nonsense protein = damaged mb= incr [drug] = more drug gets in = stop ribosome completley = ribosomal blockade
bacteriocidal |
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Term
| are aminoglycosides absorbed from the gut? |
|
Definition
no, neomycin = gd for gut infections or to clear gut of bacteria b4 surgery
(cant give neomycin parenterally as too toxic!) |
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Term
| does aminoglycoside cross BBB? |
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Definition
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|
Term
| elimination of aminoglycosides = |
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Definition
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|
Term
| clinical use of aminoglycosides = |
|
Definition
1. tx gram - infections, used with beta lactam (eg penstrep)
2. more effective at alkaline pH = gd at txing urinary tract infections
3. gentamycin reserved for tx of pseudomonas |
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Term
| Aminoglycosides adverse reaction = |
|
Definition
| 1. vestibular or auditory toxicity (reversible or irreversible) 2. nephrotoxicity (more common in cats) 3. some impairment to neuromuscular transmission 4. synergise with anaesthetics so dont use during surgery 5. synergise with muscarinic R blockers = reversible mm weakness |
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Term
| what sp of bacteria are inately R to aminoglycosides? |
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Definition
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|
Term
| bacterial R in aminoglycosides = |
|
Definition
| develops rapidly due to bacterial enzymes inactivating drugs |
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Term
| only tx with aminoglycosides for 2-3days max. why? |
|
Definition
to decr the risk of bacterial R
with strep and gentamycin, no longer than this due to toxicity! |
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|
Term
| pros and cons of aminoglycoside being + charged = |
|
Definition
pros= ion trapping in bacteria = incr [drug] in bug
cons= poorly absorbed and rapid excretion by kidneys |
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Term
|
Definition
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Term
|
Definition
blocks tRNA access of ribosome to A site
bacteriostatic |
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Term
| selectivity of tertacyclines due to ... |
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Definition
| ...selective uptake by bacteria |
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Term
|
Definition
orally on empty stomach
DONT give with Ca2+ containing food due to ion chelation and inhibition of absorption |
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Term
| distribution of tertacyclins = |
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Definition
|
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Term
| tertacyclin elimination by... |
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Definition
|
|
Term
| clinl use of tertacyclins = |
|
Definition
wide spectrum of activity
recyclled through bile and therfore excellent for biliary or gut infections |
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Term
| adverse reactions of tertacyclins = |
|
Definition
uncommon
1. superinfection (horses and small furies espec-septicaemia, shock and death!)
2. sometimes dental hyperplasia & bone deformities (Ca2+ chelation = decr Ca2+)
3. Cattle = CVS collapse and CV shock if admin rapidly IV (Ca2+ chelation = decr Ca2+ = CV effects) |
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Term
| bacterial R of tertacyclins = |
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Definition
| relatively common and transmitted on plasmids involved in synth of proteins thats transport tetracyclins out of the cell |
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Term
|
Definition
|
|
Term
| -ive charge of tertacyclins = |
|
Definition
| allows tertacyclins to coordinate around/sit around cations = bind to Ca2+ or Mg+ = cause toxic effects :( |
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Term
|
Definition
| IM, but painful so often admin with a LA |
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Term
|
Definition
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Term
|
Definition
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Term
| mech of action of macrolides and lincosamides |
|
Definition
bind to 50S subunit of ribosome and induce dissociation of tRNA = disrupt peptide chain completion = inhibit translocation
high dose =bacteriocidal
low dose= bacteriostatic |
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Term
| macrolides and lincosamides shouldnt be given with... |
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Definition
| ...chloramphenicol (have same binding site so will out compete eachother = decr response of each drug) |
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Term
| erythromycin is acid unstable which means... |
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Definition
| ...its broken down in stomach, but may be admin orally in coated tablets (enteric coat) |
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Term
| clinical use of macrolides and lincosamides |
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Definition
| predominantly effective against gram + (like penicillin therefore often give if pateint allergic to pen) |
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Term
| what bacteria is R to erythromycin? |
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Definition
|
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Term
| how does R to macrolides and lincosamides occur? |
|
Definition
change binding site of drug on 50S ribosome subunit
R transmitted by plasmids |
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Term
| macrolides spectrum of activity is imilar to what drug? |
|
Definition
|
|
Term
| lincosamides are reserved for tx of... |
|
Definition
...anaerobic bacteria
or used when other Abs cant reach area of infection eg osteomyelitis as lincosamides have excellent tissue penetration |
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Term
| advers effects of macrolides and lincosamides |
|
Definition
rare
GI upset (cramps, nausea, vom and diarrhoea) |
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Term
| Name 2 chloramphenicol Abs licenced in vetmed |
|
Definition
chlormaphenicol
florfenicol |
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Term
|
Definition
inhibti peptidyltransferase =inhibit transpeptidation
bacteriostatic |
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Term
| chloramphenicols distribution = |
|
Definition
| diffuses well around the body, including BBB |
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Term
| admin of chloramphenicol = |
|
Definition
oral, well absorbed
ointment -topical admin on eye
rarely used systemically |
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Term
| metab of chloramphenicol = |
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Definition
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|
Term
| chloramphenicol is banned from use in... |
|
Definition
| ...food animals due to its v gd efficacy against salmonella typhi in man (alot of drugs S. typhi R to!) |
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Term
| adverse reactions of chloramphenicol = |
|
Definition
| in cats where metab is poor = drug accum = reversible or irreverible (aplastic anaemia) BM supression |
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Term
|
Definition
by bacteria producing chloramphenical acetyl transferase
little R as not used v often |
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Term
| 2 drugs that bacteria have developed R to due to producing enzymes against drugs = |
|
Definition
beta lactams
chloramphenicol
aminoglycosides |
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Term
| Abs affecting nuceliec acid synth in bacteria = |
|
Definition
sulphnamide and trimethorpim
(effect synth of folic acid)
and Quinolones (inhibit DNA gyrase) |
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Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| how is trimethoprim slective for bacteria as mammals have DHFR too? |
|
Definition
| mammalian DHFR has a diff structure to bacterial DHFR |
|
|
Term
| sulphonamide + trimethoprim = |
|
Definition
synergise = bacteriocidal
(alone = bacteriostatic) |
|
|
Term
| sulphonamides and trimethorpim are structural analogues of... |
|
Definition
|
|
Term
| are sulphonamides and trimethorpim well absorbed from the gut? |
|
Definition
|
|
Term
| distribution of sulphonamides and trimethorpim = |
|
Definition
| gd, penetrate tissues well |
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|
Term
| elimination of sulphonamides and trimethorpim = |
|
Definition
|
|
Term
| adverse reactions of sulphonamides and trimethorpim = |
|
Definition
1. keratoconjunctivitis
2. renal damage (avoid as lon as patient has plenty of water) |
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Term
| bacterial R of sulphonamides and trimethorpim = |
|
Definition
| widespread R across UK!! :( due to inactivating enzymes and change in target site (DHPS and DHFR) |
|
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Term
|
Definition
inhibit bacterial DNA gyrases reannealing ability = DNA fragmentation
bacteriocidal |
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Term
| quinolones target gram - or + bacteria? |
|
Definition
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|
Term
| give 2 examples of quinolones |
|
Definition
| nalidixic acid and difloxacin |
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Term
|
Definition
|
|
Term
| elimination of quinolones = |
|
Definition
|
|
Term
| quinolone used commonly to tx... |
|
Definition
| ...bacterial infection in cows |
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|
Term
| quinolones spectrum of activity = |
|
Definition
| restricted to aerobic bugs |
|
|
Term
| adverse reaction sof quinolone = |
|
Definition
rare
-may cause inhbition of cartilage growth in young D&Cs
-can predispose animal to epilepsy |
|
|
Term
| quinolone is contraindicated in... |
|
Definition
|
|
Term
|
Definition
| slow and usually due to change in taget DNA gyrase |
|
|
Term
| genetic determinants of bacterial R = |
|
Definition
1. chrom mutation
2. extrachrom -plasmids
3. transfer of genes between genetic elements of a bacteria via transposons
4. transfer of genes between bacteria by conjugation and transduction (by plasmids) |
|
|
Term
| biochemical mechanisms of required antibiotic R = |
|
Definition
1. inactivation of Ab
2. alteration to drug target
3. decr drug accum in bacteria |
|
|
Term
| why are gram - bugs more intrinsically R ? |
|
Definition
|
|
Term
| how are anaerobic bugs intrinsically R to aminoglycosides? |
|
Definition
| lack the O2 dependant transport req to take up aminoglycosides |
|
|
Term
| why are pseudomonas aeruginosa and mycobacterium tuberculosis R to most Abs? |
|
Definition
v. impermeable cell wall and huge array of ability to transfer plasmids
(R commonly already there or develops v quickly) |
|
|
Term
| selection of suitable drug = |
|
Definition
1. bacterial sensitivity
2. sp and breed
3. predisposition to toxicity (eg Gpig superinfection after pen admin)
4. site of infection
5. mode of antibacterial action (static or cidal)
6. drug factors - dose, duration of action, route of admin |
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