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143 Cards in this Set

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What are the classes of Beta Lactam cell wall inhibitors?
Penicillins, Cephalosporins, Carbapenems, Monobactams
What are the Non-Beta Lactam Cell Wall Inhibitors
Vancomycin, bacitracin
Which anitbacterial agent works by disrupting the cell membrane?
Polymyxins
Which classes of antibacterials inhibit protein synthesis and on which ribosomal sub-unit do they effect?
Aminogylcosides
Tetracyclines
Amphenicols
Macrolides
Lincosamides
Which classes inhibit metabolism?
sulfonamides
diaminopyrimidines
Which classes inhibit replication?
Fluoroquinolones
Metronidazole
Rifampin
Antibiotics that inhibit cell wall synthesis include:
beta lactams, bacitracin, vancomycin
Antibiotics that inhibit cell membrane function include:
polymyxins
Antibiotics that inhibit protein synthesis include:
Aminoglycosides, Tetracylcines, Macrolides, Amphenicols, Lincosamides
Antibiotics that inhibit nucleic acid synthesis include:
Fluoroquinolines, Rifampin, Metronidazole
Antibiotics that interfere with bacterial metabolism include:
Sulfonamides, Diaminopyrimidines
When do we use first line antibiotics?
used against easy to kill bacteria
very effective against G(+), not effective or weakly effective against G(-)
What are some examples of typical first line antibiotics?
Narrow Spectrum Penicillis (penicillin G)
Broad Spectrum Penicillins (ampicillin, amoxicillin)
Augmented Penicillins (clavomox)
First Generation Cephalosporins (Cephalexin, Cephlazolin)
Bacitracin (G+), Neomycin(aminoglycoside), macrolides (erythromycin, azithromycin), lincosamides, tetracylcines, sulfonamides, amphenicols.
When do we use 2nd line antibiotics?
more serious life threatening infections
tough gram negative bacterial infxns
in combination with 1st line to tx mixed infxn (broad spectrum combinations)
Examples of 2nd line antibiotics include:
2nd and 3rd generation cephalosporins (Cefoxitin, cefuroxime, ceftiofur), aminoglycosides (gentamycin, streptomycin, amikacin), fluoroquinolones (Enrofloxacin)
When are 3rd line antibiotics indicated?
Very effective against specific tough bacteria (pseudomonas, staphalococcus, Gram Negative infxns). ONLY use based on culture
Examples of 3rd line antibiotics include:
vancomycin, monobactams, carbapenems, antipseudomonal penicillins ( ticarcillin, carbenicillin), antienteric penicillins (mellicam), antistaphylococcal penicillins (methacillin, oxacillin, coracillin, didoxacillin, nafacillin)
What is the order of activity against gram negative infections of the Penicillins?
Augmented > broad > narrow
Penicillins work by?
They are bacteriocidal. They work by inhibiting bacterial cell wall synthesis by interfering with Penicillin Binding Proteins
Describe the absorption, distribution and metabolism of Penicillins.
Absorption: weak organic acids, given with salts to increase duration of action.
Distribution: low vD, High concentration in interstitial fluid (ok b/c most infections are extracellular), Poor BBB penetration.
Metabolism: excreted unchanged in urine. Crosses placenta and excreted in milk
What are the dosing considerations of Penicillins?
bactericidal, time dependent killing effect, cell must be actively dividing for them to be effective, action is slow and characterized by a lag period, synergistic with aminoglycosides.
General activity rules for Penicillins:
Narrow, Broad, Augmented
Effective against many G(+) Aerobes, G (+) and G(-) anaerobes.
How can you increase your spectrum for treating a mixed infection. (what other drugs would you use with broad penicillins?)
Broad Penicillin + Aminoglycoside/ Fluoroquinolone
Why would we want to combine a broad spectrum penicillin (ie, amoxicillin or ampicillin) with a drug like gentamycin or enrofloxacin?
To get full coverage against gram postive, gram negative, anaerobes, and aerobes---WIDENS THE SPECTRUM
In what type of infections would I use penicillin drugs such as methacillin, oxacillin, or cloracillin?
These are antistaphylococcal penicillins and have resistance to beta lactamases produced by staph.

Bovine mastitis, skin infxns of dogs
In what type of infections would you use penicillins such as ticarcillin, carbenicillin
These are antipseudomonal drugs effective against tough G(-) pseudomonas infections. May have reduced activity against G (+)
In what type of infections would you use penicillins such as mellinam?
Antienteric
no effect on G(+) or Pseduomonas
Active against enterobacteriaceae
Cephalosporins are divided into 4 generations. How does activity against G(+) and G(-) change as we go up in generation?
As you go up generations the avitvity against G(+) bacteria decreases, and the activity of G(-) bacteria increaes.
What are some examples of 1st generation cephalosporins?
Cephalexin, Cephazolin, Cephapirin
Examples of Second Generation Cephalosporins
Cefoxitin, cefuroxime
Examples of 3rd Generation Cephalosporins:
ceftiofur, cefotaxime, cefocvecin, cefpodoxime, cefoperazone,ceftazadime
What is special about 3rd generation cephalosporins that sets them apart from other cephalosporins?
1. Some are effective against pseudomonal infections
2. They can penetrate the brain
What drug is considered 4th generation cephalosporin and why is it's use favored?
Cefepime- most broad spectrum against both gram postive and negative aerobes. Only have to give it once and effective despite owner compliance
What is special about cefovecin? What generation of cephalosporin does it belong to.
Cefovecin has an extremely long duration of action b/c it is highly protein bound. Given once as a SQ injection and stays in the body for up to 2 weeks. It is a 3rd generation
If you have an infection in the bone which first line antibiotic are you more likely to use? Penicillin or Cephalosporin
Cephalosporins have wider distribution and good bone penetration when compared with penicillins
What are some considerations when dosing cephalosporins?
bactericidal
time dependent
synergistic with aminoglycosides
Uses of first generation cephalosporins
combined with aminoglycosides and fluoroquinolones to improve gram negative spectrum and allow 4-quadrant coverage.
Used in antibacterial prophylaxis in surgery cefazolin
Used in skin, bone, and soft tissue infections in dogs (vetter penetration than penicillins.
What types of antibiotics would we combine to gain "4-quadrant coverage"?
Broad Spectrum Penicillin (amoxicillin, ampicillin)
OR 1st generation cephalosporin (cephalexin, cephazolin)
+ Aminoglycosides and Fluroquinolones (for cephalosporins
Which cephalosporin is effective against Bacteroides flagilis and which generation does it belong to.
Cefoxitin = second generation.
which generation of cephalosporins should be considered for enterobacteriaceae infxns?
3rd generation
What are some uses of third generation cephalosporins?
not a first line antibiotic- mainly for tough gram negative infxns. Meningitis caused by gram negative bacteria in small aniamsl.
Why is imipenem considered a 3rd line antibiotic and what class of drugs does it belong to?
It is a carbapenem. It is one of the few antibiotics effective against gram positive aerobes and anaerobes and gram negative aerobes and anaerobes.
What are the pharmacokinetics of carbapenems?
Must give imipenem IV or IM q4-6h
Distribution: wide distribution; may penetrate CNS in meningitis, crosses the placenta and excreted in milk.
metabolism/excretion: excreted in kidneys
Antibacterial spectrum of imipenem?
aerobic and anaerobic gram positive or gram negative infections including Pseudomonas aeuruginosa
Uses of carbapenems:
used for tough gram negative infections, should not be used for gram positive.
Which beta lactams penetrate the brain?
3rd generation cephalosporins
Carbapenems (Imipenem)
Monobactams (Aztreonam)
What is the antibacterial spectrum of monobactams (aztreonam)?
Narrow spectrum
Active against gram negative aerobic bacteria (including Pseudomonas)
Vancomycin is a non-beta lactam cell wall inhibitor. How do these types of drugs interfere with cell wall that differs from Penicillin drugs?
Vancomycin and other non-beta lactam cell wall inhibitors such as Bacitracin work by binding directly to the cell wall whereas Beta Lactams like Penicillin interfere with penicillin binding proteins.
When is it appropriate to use vancomycin?
Vancomycin is a 3rd line antibiotic used against gram positive aerobes and anaerobes
MRSA!!!! (methicillin resistant staphylococcus)
What are the dosing considerations of vancomycin?
absorption: poorly absorbed orally
distribution: tissue penetration is poor and it doesn not cross the bbb
metabolism" most excreted in kidneys
What are two antibiotics used to treat topical skin infections? Which is mainly effective for gram positive? Gram negative?
Bacitracin (gram positive); Polymyxin (gram negative)
Name the three antibiotics used in Triple Antibiotic Cream
Neomycin, Bacitracin, Polymyxin
Why is bacitracin only used topically and not for systemic gram positive infections?
It is nephrotoxic. Poorly absorbed orally
What type of infection is treated with oral bacitracin?
GI infections especially those caused by C. perfringens in suckling pigs or necrotic enteritis in poultry.
What is the mechanism of action for polymyxins
bactericidal
disrupts cell membrane phospholipids, resulting in increased cell permeability by detergent acting
What are the dosing considerations for Polymyxins? what other antibiotic has similar considerations?
poorly absorbed orally
highly nephrotoxic
used primarily topically and orally (GIT)
What is the spectrum of polymyxin?
Acts mainly against gram negative bacteria, including Pseudomonas aeruginosa.
What is the antibiotic spectrum of fluoroquinolones?
effective against gram positives and negatives. Not effective against anaerobes
Fluoroquinolones are _________ line?
2nd line antibiotics. They are used in a serious infection where tough gram negative or mixed infections are suspected.
In what patients would we use fluoroquinolones over aminoglycosides?
Renal failure and shock (poor perfusion)
What are examples of fluoroquinolones?
ciprofloxacin, enrofloxacin, orbifloxacine, difloxacin, marbofloxacin
How do fluoroquinolones work?
rapid bactericidal action
inhibits bacterial DNA Gyrase
The dosing considerations of fluoroquinolones are...
concentration dependent
exhibit post antibiotic effect- better to give once daily at high doses
antagonized by chloramphenicol or rifampin. Synergistic with beta lactams and lincosamides
Hypoxia and low pH decrease activity (not good for anaerobes)
Which drugs antagonize fluoroquinolones?
chloramphenicol or rifampin
Which drugs are synergistic with fluoroquinolones?
beta lactams and linocsamides
What are the pharmacokinetics of fluoroquinolones?
absorption: readily absorbed orally
Distribution: wide distribution to tissues, penetration of bone, skin, cartilage and brain because of high lipid solubility. Highly concentrated in lungs and prostate
Metabolism: urine and bile. Dosages need to be reduced in patients with renal failure, concentrations may be higher in urine and bile than in serum during elimination
What is the antibiotic spectrum of fluoroquinolones?
gram negative aerobes, gram positive aerobes

Inactive against anaerobes

active against intracellular infections such as chlamydia and rickettsia
Mycoplasma
Fluoroquinolones are most often used when?
good second line antibiotic for tough gram negative infections. It is commonly combined with penicillin, 1st generation cephalosporin or clindamycin for better anaerobic and G(+) aerobic coverage.

Drug of choice for gram negative urinary infections.

used in intracellular infections: ricketssia, chlamydia, mycoplasma
What are the adverse effects of fluoroquinolones?
relatively safe, cartilage erosionin growing animals, seizure at high doses with CNS disorders, toxic shock syndrome, Enrofoxacine causes concentraion dependent retinal damage in cats,
What are special dosing considerations when administering fluoroquinolones to cats? Why is this the case?
Fluoroquinolones like enrofoxacin may cause a concentration dependent retinal damage in cats and therefore cats should be given lower doses, BID
Why shouldn't fluoroquinolones be given to young animals?
Fluoroquinolones may cause cartilage erosin in growing animals especially ing dogs. It should not be used in young animals (under 1 year old) unless absolutely necessary.
What are some examples of aminoglycosides?
Streptomycin, neomycin, gentamycin, amikacin
How do aminoglycosides work?
rapid bactericidl action by inhibiting the 30S ribosome unit to inhibit protein synthesis.
The dosing considerations for aminoglycosides are:
concentration dependent with post antibiotic effect and time dependent toxicity. May be better to give once daily at higher doses.

Administered parenterally and topically on the skin and mucous membranes
Which drugs are synergistic with aminoglycosides?
beta latams increase penetration.
Also lincosamides
Why are aminoglycosides ineffective against anaerobic bacterial infections/
penetration ofbacterial cells is either by passive diffusion or active transport which requires oxygen.
Why is it best to give aminoglycosides by injection?
poor oral absorption.
How are aminoglycosides excreted?
Renal
What is the antibacterial spectrum of aminoglycosides?
broad spectrum (similar spectrum to fluoroquinolones)
gram negative aerobes- including tough gram negatives like enteric bacteria and some are effective against pseudomonas
gram positive aerobes
Not effective against anaerobes
Intracellular bacteria- mycoplasma, mycobacteria, leptospirosis
When are gentamicin and amikacin indicated?
gentamicin and amikacin are for serious gram negative infections (skin, eye, ear, septicemia, respiratory tract and urinary tract. Both are effective against Pseudomonas
When is streptomycin indicated?
Streptomycin is used for mycobacteria and leptospirosis
What is the major concern when using aminoglycosides?
Nephrotoxicity, especially with prolonged use, patient in shock or patients with renal disease. Toxicity is TIME dependent. Increased risk of nephrotoxicity with lasiks. Neomycin is the most nepthrotoxic, streptomycin is the least.
Degree of nephrotoxcity of aminoglycoside drugs:
Neomycin>Gentamicin>Amikacin>Streptomycin
Aminoglycosides are severely nephrotoxic but what are the other adverse effects of this class?
ototoxcity, cochlear toxic (also increased by loop diuretics), weak neuromuscuar blockade of ACH at Nicotinic receptor. Should not use in animals myasthenia gravis or muscle relaxants. Weak cardivascular depression following IV injections.
Which drugs belong to the Tetracylcines?
Chlortetracycline, oxytetracycline, tetracycline, minocycline, doxycycline
Which Tetracycline drugs are more lipophilic than the others? What does this mean in terms of pharmacokinetics?
Minocycline and Doxycycline
they can penetrate cells more easily. They can cross special barriers like the BBB.
How do tetracylcine drugs work?
bacteriostatic
Bind 30S inhibit bacterial protein synthesis
What sort of things alter the absorption of tetracyclines?
milk, calcium, magnesium, manganese, iron, and aluminum.
Most tetracyclines are only excreted in the urine. What is the difference between in minocycline and doxycycline metabolism?
doxycycline is excreted mainly in the GIT in bile and by diffusion.
Minocycline urinary excretion is low
enterohepatic recycling
excreted in milk
What are the uses of tetracyclines?
G(+) aerobes- Listeria in ruminants
G(-) aerobes- not really
Anaerobes: Clostridia
INTRACELLULAR BACTERIA: rickettsia, ehrlichia, anaplasma, and chlamydia
Good against mycoplasma, Borrelia, haemobartonella, and brucellosis, leptospirosis
What are some non antibacterial actions of tetracyclines?
antiinflammatory, antiapoptotic, and immunosuppressive properties. may be neuroprotective.
Why wouldn't we give tetracyclines to young animals?
yellow teeth. Binds to Ca in teeth and bones
What are some adverse effects of tetracyclines?
GIT upset, at high doses it can be nephrotoxic and heaptotoxic, deposition in bone and teeth, cardiovascular depression following rapid IV injection, irritating to tissues.
Which drugs belong to the amphenicol group? Which of these is highly toxic to humans?
Chloramphenicol is toxic
Florfenicol- safe in food animals
Why is chloramphenicol so dangerous in humans?
It causes irreversible aplastic anemia
How do amphenicols work?
bacteriostatic
bind to the 50s subunit to inhibit protein synthesis
Amphenicols are antagonistic with many other drugs, please name a few.
fluoroquinolones, bactericidal drugs like beta lactams, macrolides and lincosamides
Describe the pharmacokinetics of amphenicols.
Absorption: good oral absorption
Distribution: wide distribution, including to brain and eye
Metabolism: liver, inactive in urine
Describe the anitmicrobial spectrum of amphenicols.
Good against gram positive and gram negative aerobes and anaerobes INCLUDING BACTEROIDES FRAGILIS) resistance in enterics
Good for intracellular infections too
What are the uses of chloramphenicol?
Chloramphenicol is used for local infections (eyes, ear, mammary gland), also for meningitis and prostatitis caused by G(-) and anaerobes.
What are the uses of florfenicol?
It is approved for treatment of bovine respiratory disease (Mannheimia haemolytica, Pasterurella multocida, and Hameophilus somnus) in cattle
Even though amphenicols are similar to broad spectrum penicillins and first generation cephalosporins against gram positive aerobes, and some gram negative aerobes and anaerobes, why might we reconsider their use?
anmphenicols are bacteriostatic and have serious side effects.
What are some adverse effects of amphenicols?
danger of NON DOSE RELATED irreversible fatal aplastic anemia in humans. Contraindicated in food animals (chloramphenicol)

Both cause a dose related reversible bone marrow suppression in animals
vomiting, diarrhea, anaphylaxis
Animals should not be immunized during tx.
What are some drugs that belong to the macrolides?
erythromycin, tylosin, tilmicosin, azithromycin, clarithromycin
Macrolides are basic compounds, what does this tell you about where they concentrate in the body and what infections they might be good for treating.
As basic compounds they concentrate in acidic areas such as the mammary gland and prostate. They are good at treating infections of these places as well as in the pulmonary system.
How do macrolides work?
bacteriostatic. binds to 50s ribosomonal subunit causing inhibition of protein synthesis
Is it a good idea to combine macrolides with other antibiotics?
No sometimes they are synergistic, antagonistic or indifferent. They are antagonistic with chloramphenicols or lincosamides.
Describe the pharmacokinetics of macrolides.
well absorbed, erythromycin must be enteric coated to prevent degradation by stomach acid, but newer ones are acid stable. Widely distributed with acidic trapping, do not achieve high concentrations in brain. Metabolized in liver, excreted in bile as metabolites.
Why would you have to be careful if administering erythromycin with other drugs?
It is an enzyme inhibitor thus may decrease the metabolism of other drugs.
Which macrolide is the drug of choice for treating Rhodococcus equi in foals?
erythromycin + rifampin
Which macrolide is the drug of choice for treating diarrhea and abortion due to Camplyobacter jejuni in dogs and foals?
Erythromycin
Which macrolide is effective in treating mycoplasma infections in cattle and swine
tylosin
Which macrolide in long acting prepartions is used for bovine respiratory disease due to Mannheimia haemolytica and Pasteurella multocida by SQ injection only?
Tilmicosin
What are some drugs in the Linocsamides?
linocmycin, clindamycin, pirlimycin
How do linocsamides work?
they bind to the 50s ribosomal subunit, bacteriostatic
Lincosamides are synergistic with which drugs to creat good 4 quadrant coverage?
Fluoroquinolones and Aminoglycosides
Linocosamides are basic drugs, therefore where are they likely to be used for infections
udder and prostate
What is the antibiotic spectrum of linocosamides?
gram positive aerobes, weak against gram negative aerobes.
Have excellent gram positive and gram negative anaerobic coverage.
What are the uses of lincosamides?
effective against mycoplasma, toxoplasma, alternative first line abs,
Gram anaerobic dental infections ins small animals
What are the adverse effects of lincosamides?
relatively safe antibiotic, vomitting diarrhea and anaphylactic shock, neuromsuclar blockage. Contraindcated in HORSES, rabbits, & guinea pigs b/c of fatal diarrhea due to inhibition of normal microflora.
which drugs are part of sulfonamides?
sulfacetamide, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfamethazine, sulfaquinoxaline, sulfasalazine, sulfathiazole, sulfamethoxazole.
What sulfonamide chemistry that may cause adverse effects?
poorly soluble in water, solubility is important due to crystal formation which can cause renal toxicity. `
How do sulfonamides work?
bacteriostatic
PABA derivative causes blockage of folic acid
why are sulfonamides generally combined with diaminopyrimidines
together they become bacteriocidal
Which sulfaonamide is the drug of choice for chronic colitis in dogs?
sulfasalazine
What are common adverse effects of sulfanomides?
crystalluria and renal damage, keratoconjunctivitis sicca (dry eye) ing dogs may or may not be reversible, haematopoietic disorders such as a thrombocytopenia, leukopenia, and immune mediated hemolytic anemia. Potentially hepatotoxic
What role do sulfanomides play with vitamin K?
sulfonamides decrease vitamin K synthesis.
Diaminopyrimidine drugs include:
trimethoprim, ormetoprim, pyrimethamine
How do diaminopyrimidines work?
bacteriostatic, block converstion of dihydrofolic acid to tetrahydrofolic acid by compettiive inhibition of dihydrofolate reductase.
What are the antibacterial spectrum of diaminopyrimidines/
good against G(+) and G(-) aerobes, poor against anaerobes, effective against coccidia
What are the adverse effects of diaminopyrimidines
may induce folic acid defiency at high doses
A potentiated sulfonamide is...
sulfonamide + diaminopyrimidine
which bacteria is metronidazole strictly used against?
anaerobes
How does metronidazole work?
bactericidal,
reduces anaerobic bacteria and protozoa to metabolites that cause DNA damage
What is the antibiotic spectrum of metronidazole?
effective against gram + and gram - anaerobes( Clostridium, Bacteroides fragilis)
Effective aganst protozoa
What is metronidazole the drug of choice in treatment?
drug of choice for acute gingivitis and periodontal disease.
What are the adverse effects of metronidazole?
GIT irritation, CNS signs at large doses
What antibiotics are used to treat hepatic encephalopathy medically?
Metronidazole, Neomycin
Which antibiotic is associated with neurologic adverse effects?
metronidazole at high doses
what antibiotics would you most likely use for a kitten with possible mycoplasma or chlyamida infections
tetracylcines and fluroquinolones
Listeriosis what antibitotic to use?
pencillins in sheep
Tough staph infection in dog?
methicillin or even vancomycin
Which antibiotic is associated with vestibular problems?
aminoglycosides or metranidazole.