Antibiotics Flashcards
Which type of bacteria is more susceptible to beta-lactams?
Gram positive
Where do gram positive bacteria secrete their B-lactamases?
into the intracellular fluid outside their cell wall.
Where do gram negative bacteria secrete their B-lactamases?
In the periplasmic space between their cell wall and cell membrane
**they are inheriently resistant to B-lactamases due to outer membrane
Name two B-lactamase inhibitors.
Clavulanic acid or Sulbactam
What bacteria do penicillins generally work on?
Gram positive.
As well as anaerobes and spirochetes
Are penicillins bacteriostatic or bacteriocidal?
Bacteriocidal
Are penicillins concentration or time dependent?
Time dependent
Do penicillins cross the BBB?
NO.
but have high concentrations in kidney, synovial fluid, lungs, skin, and soft tissue
How are penicillins excreted?
Actively in the urine
Contraindications with penicillins?
Do NOT use in reptiles, birds, or hypersensitivity patients.
Do NOT use orally in horses, ruminants, guinea pigs, or chinchillas
Name the 5 penicillins we know.
Penicillin G Ampicillin/Amoxicillin Amoxicillin-Clavulanic acid Cloxacillin Ticarcillin
Penicillin G is used more in SA or LA?
Because of this how is it usually given?
LA.
parenteral.
How is Ampicillin given and how is Amoxicillin given?
Ampicillin - parenterally
Amoxicillin - orally
*both used for SA and LA (mastitis) gram positives
What are the benefits of using Amoxicillin-Clavulanic acid?
inhibits B-lactamases to increase efficacy
What is Cloxacillin used for?
B-lactamase stable penicillin used for mastitis in cattle
What is Ticarcillin used for?
‘anti-pseudomonas’ penicillin occasionally used topical in the ear
What are first generation cephalosporins effective against?
Gram positive and less susceptible to B-lactamase than penicillins.
**Cephalosporins are more broad spectrum than penicillins
What are second generation cephalosporins effective against?
Gram positive with a greater efficacy against gram negatives.
What are third generation cephalosporins effective against?
Gram negatives with less gram positive activity
What are fourth generation cephalosporins effective against?
Broad spectrum positive and negative, plus pseudomonas and B-lactamase resistant
*Not used in vet ed usually bc ‘big gun’
Are cephalosporins time or concentration dependent?
Are they bactericidal or bacteriostatic?
Time dependent and bacteriocidal
Do cephalosporins cross the BBB?
Nope.
but well absorbed orally
Contraindications of cephalosporins?
Reptiles, birds, and hypersensitivity patients
Do NOT give orally to horses, ruminants, guinea pigs
Name three first generation cephalosporins.
Cephalexin
Cefazolin
Cephapirin
What is cefazolin used for?
First generation cephalosporin used prophylactically during surgery
What is cephapirin used for?
Mastitis in cattle via intramammary infusion
What is Cefoxitin used for?
SECOND generation cephalosporin for serious infections
Name three third generation cephalosporins.
Ceftiofur (foot rot/resp dx)
Cefovecin
Cefpodoxime
What is Cefovecin used for?
Third generation cephalosporin that is highly protein bound, given once a week or two weeks.
treats pyoderma (staph - dog, pasteurella - cats)
How does cefpodoxime become active?
Pro-drug until GI absorption turns in into an active drug
What bacteria do carbapenems work on?
Positive, negative, pseudomonas.
What is dangerous about Carbapenems?
They have a greater Post-Antibiotic Effect (PAE) than other B-lactams with a greater toxicity.
Are carbepenems time or concentration dependent?
Are they bacteriocidal or bacteriostatic?
Time dependent and bacteriocidal.
Do carbapenems cross the BBB?
YES.
What are the risks of Imipenem if not given as a slow IV infusion?
Phlebitis and Seizures.
**Meropenem is a safer alternative given SC
Name two drugs that work on cell wall synthesis but are not B-lactams.
Vancomycin and Bacitracin.
How does vancomycin work?
The glycopeptides bind to NAG and NAM to prevent cross-linking and inhibit cell wall synthesis
Is Vancomycin time or concentration dependent?
Is it bacteriocidal or bacteriostatic?
Time dependent and bacteriocidal
What does vancomycin work againt?
Almost all gram positives including MRSA.
Gram negatives are generally resistant
What drug can you give orally that works againt C. difficile in the GIT?
Vancomycin
Does Vancomycin cross the BBB?
Nope.
Adverse effects of Vancomycin?
histamine release, nephrotoxicity, and ototoxicity.
*Do NOT use in food producing animals
How does bacitracin work?
against the isoprenyl pyrophosphate enzyme responsible for the ‘building blocks’ of the cell wall.
What is Bacitracin effective against?
Gran positive.
*often used in triple antibiotic ointment with neosporin and polysporin.
How do Beta-lactams work?
disrupt transpeptidation by binding their beta-lactam ring to the penicillin binding protein
*osmotic pressures eventually lead to cytolysis
What are the categories of Beta-lactam antibiotics?
Penicillins
Cephalosporins
Carbepenems/Monobactams
What antibiotics affect the cell membrane?
Polymyxin B.
How does polymyxin B work?
Antiseptic.
Binds to LPS’s and acts as a cationic detergent to disrupt the membrane, making it bacteriocidal.
*doesnt work against gram positive
Contraindications of polymyxin B?
Toxic, limited to topical use.
Fatal anaphylactic reactions reported in Cats.
Name the five groups of drugs that disrupt protein synthesis.
Tetracyclines. Amphenicols. Macrolides/Lincosamides. Streptogramins. Aminoglycosides.
T/F Most drugs that disrupt protein synthesis are bacteriocidal.
False.
Bacteriostatic
How do tetracyclines work?
Inhibiting tRNA of the 30s ribosomal subunit as well as inhibiting MMP’s
What are tetracyclines effective against?
Positive, Negative, mycoplasma, chlamydia, spirochetes and rickettsial organisms.
*NOT good against pseudomonas and proteus
Are tetracyclines time or concentration dependent?
Time dependent
Contraindications of Tetracyclines.
Chelate divalent cations (drug-drug/drug-fluid interxns)
Antagonistic to penicillins
Toxicity issues of Tetracyclines?
Yellowing of teeth, GI issues, esophageal stricture**, dysbiosis, bitter taste, and cardiac complications with rapid IV injection.
Name the 4 tetracyclines we know.
Oxytetracycline
Chlortetracycline
Doxycycline
Minocycline (Doxy alternative)
What is oxytetracycline and chlortetracycline used for?
broad spectrum for large animals
chlortetracycline can be used as feed additive
Benefits of Doxycycline.
better GI absorption, greater CNS penetration, less renal excretion, and less likely to cause teeth/bone changes.
Risks of Doxycycline.
When given IV can cause arrhythmias, collapse, and death.
especially horses
Can cause esophageal stricture in cats if not given with water
What drug do we use to treat Ehrlichia, Anaplasma, Borriela, and Heartworm management?
Doxycycline!
How do amphenicols work?
Inhibit peptidyl transferase on the 50s ribosomal subunit.
Are amphenicals time or concentration dependent?
Bacteriocidal or bacteriostatic?
Time dependent and bacteriostatic.
Contraindications of amphenicols?
Inhibit hepatic microsomal enzymes (drug-drug interactions) and antagonize macrolides.
Adverse effects of Amphenicols?
Bone marrow suppression, idiosyncratic aplastic anemia in humans (chloramphenicol), and GI signs.
Contraindications of Chloramphenicol use in Cats.
Metabolized in the liver via glucoronidation normally, therefore more needs to be excreted in the kidney with cats. could lead to toxicity.
What is Chloramphenicol used to treat?
MRSP.
Illegal to use in food animals (use FLORFENICOL)
How do Macrolides/Lincosamides work?
Inhibit translocation and movement of the 50s ribosomal subunit
Name 5 macrolides.
Erythromycin Tylosin Tilmicosin Tulathromycin Azithromycin
Name 3 lincosamides.
Lincomycin
Pirlimycin
clindamycin
Are Macrolides time or concentration dependent?
Bacteriostatic or Bacteriocidal?
Time-dependent and bacteriostatic
What type of bacteria are macrolides effective against?
Gram positive with more anaerobic activity.
Macrolides/Lincosamides have cross resistance with what drug?
Streptogramin B
Contraindications of Macrolides?
Rabbits, gerbils, guinea pigs, and hamsters.
Do NOT give oral in adult horses and ruminants
T/F erythromycin is used IM in cattle and requires an acidic environment.
False.
It is used IM in cattle but requires an alkaline environment.
Why is tilmicosin dangerous?
CARDIOTOXIC. Do not give IV. use in LA.
What is Tulathromycin used for?
Beef and Non-lactating cattle.
Single dose treatment regimen.
What is Azithromycin used for?
Small animal infections (lasts a long time in phagocytes)
As well as Rhodococcus pneumonia in foals.
Cross Resistance with Lincomysin
Clindamycin and Erythromycin
Don’t use lincomycin in which species?
Horses, Ruminents, lagomorphs.
What is Pirlimycin used for?
Lincosamide used for mastitis via intramammary infusion.
What drug is used in SAM to treat toxoplasma?
Clindamycin
*Dont use in horses, rodents, ruminants, or lagomorphs
Tell me about Streptogramins.
- Type A and B
- Bacteriostatic alone and Bacteriocidal together
- Work on the 50s ribosomal subunit
- Effective against gram positive
- Cross resistance with Macrolides/Lincosamides
- Veterinary one = VIRGINIAMYCIN
How do aminoglycosides work?
Prevent attachment of tRNA (proofreading mechanism) to the 30s ribosomal subunit.
What are aminglycosides effective against?
Gram negative aerobes.
Are aminoglycosides time or concentration dependent?
Bacteriostatic or bacteriocidal?
CONCENTRATION dependent and bacteriocidal.
Aminoglycosides have synergism with what drugs?
Penicillins
Do aminoglycosides cross the BBB?
Nope.
Adverse effects of aminoglycosides.
Post-Antibiotic Effect (PAE)
Nephrotoxic, ototoxic, vestibular injury (gentamicin and tobramycin), auditory injury (Amikacin and neomycin).
*monitor renal parameters closely
Name four Aminoglycosides.
Gentamycin.
Amikacin.
Neomycin.
Apramycin.
What is Amikacin used for?
Gram negative infections in SA, intrauterine in horses, and intra-articular in septic arthritis foals.
*better efficacy and lower toxicity than gentamycin
How do you treat hepatic encephalopathy using GI flora?
“Gut sterilization” using Neomycin
Other drugs used for MRSA.
Linezolid, Mupirocin, and Fusidic Acid.
Name six drug groups that disrupt DNA/RNA synthesis.
Sulfonamides. Fluoroquinolones. Nitroimidazoles. Nitrofurans. Rifampin. Novobiocin.
Name four Sulfonamides.
Sulfamethoxine.
Trimethoprim-sulfadiazine.
Pyrimethamine-sulfadiazine.
Sulfasalazine.
What drug is combined with rifampin to treat Rhodococcus equi in foals?
Erythromycin.
What are the three Dihydrofolate reductase inhibitors used with Sulfonamides?
Trimethoprim.
Ormetoprim.
Pyrimethamine.
*synergistic with sulfonamides
How do sulfonamides work?
Compete with PABA from bacteria for an enzyme that synthesizes DNA.
Are sulfonamides bacteriostatic or bacteriocidal?
Bacteriostatic when used alone and Bacteriocidal when use more than one (potentiate)
In what environment do Sulfonamides not work well?
Pus.
Sulfonamides are less efective when there is an increased amount of PABA (present in pus)
*Also in the rumen they dont do well
Adverse effects of Sulfonamides.
Renal damage, crystalluria, KCS, hypersensitivity, and bone marrow suppression
What is sulfamethoxine used for?
Coccidia, shipping fever, foot rot.
What drugs do you use to treat toxoplasma?
TMS and Clindamycin
What is pyrimethoamine-sulfadiazine used for?
Protozoal infectins like sarcocystis neurona in EPM (horses)
Name four fluoroquinolones.
Enrofloxacin.
Pradofloxacin.
Ciprofloxacin.
Danofloxacin.
How do fluoroquinolones work?
Inhibit DNA-gyrase (topoisomerase) and unwind DNA.
What are fluoroquinolones effective against?
Gram negatives, mycoplasma, rickettsia, and chlamydia.
Are fluoroquinolones time or concentration dependent?
CONCENTRATION dependent
T/F Fluoroquinolones are more active in pus.
False. Less active.
Toxicities of fluoroquinolones?
Arthropathy in growing animals, acute blindness in cats***, and bone marrow suppression.
T/F Enrofloxacin is more likely to cause cat blindness than pradofloxacin.
True.
T/F Ciprofloxacin is a metabolite of enrofloxacin.
True.
How do nitroinidazoles work?
Damage to DNA and RNA repair enzymes
Name the two most common Nitroimidazoles.
Metronidazole and Ronidazole (Tritrichamonas in cats***)
T/F Sulfonamides effect thyroid measurements.
True.
What are nitroimidazoles effective against?
very effective against anaerobic bacteria.
Are nitroimidazoles bacteriostatic or bacteriocidal?
Bacteriocidal.
How do nitrofurans work?
Nonspecific damage to DNA by blocking oxidative decarboxylation.
Are nitrofurans bacteriocidal or bacteriostatic?
Bacteriostatic.
What are nitrofurans (specifically nitrofurantoin) used for?
UTI’s.
Work well in acidic environments and 50% excreted as parent drug in the urine.
Adverse effect of nitrofurantoin?
GI signs, brown colored urine, heaptotoxicity, and infertility.
What is Nitrofurazone used for
Topical wound dressing in horses.
How does Rifampin work?
inhibits B subunit of RNA polymerase
What is rifampin used for?
gram-positive, gram-neg, mycobacterium and rhodococcus equi
T/F Rifampin is almost always used with other antibiotics.
TRUE.
bacteriocidal but resistance develops quickly.
Contraindications and adverse effects of rifampin?
Induces microsomal enzymes (Drug-drug_
teratogenic, red-orange discoloration of body fluids, and hepatitis.
How does Novobiocin work?
binds to DNA gyrase to inhibit repair
T/F Novobiocin is compatible with macrolides in vitro.
FALSE. Novobiocin is incompatible with macrolides in vitro.
T/F Resistance develops quickly with Novobiocin.
TRue
What is Methanamine used for? (Adjunct therapy)
Urinary antispetic.
broken down to formalin in urine, requires acidic enviroment.
What is Carbadox used for? (Adjunct therapy)
gram-negative organisms but potentially carcinogenic
What is TrizEDTA used for? (Adjunct therapy)
EDTA damages cell surface of gram negatives.
USed for pseudomonas otitis (give prior to antibiotic to increase efficacy)
WHat is Silver used for? (Adjunct therapy)
Combined with sulfa as a topical and enrofloxacin as an otitis topical.
*can cause permanent discoloration of the skin
How can you increase oral absorption of Nitroimidazoles?
Give with food.
What is Tylosin used for?
Macrolide used for antibiotic-responsive diarrhea.
