Unit 3 antimicrobials Flashcards

Question

1st line antibiotics

Answer 1

The “go to” antibiotics Three characteristics Bactericidal Narrow spectrum Least side effects 1 and 2 make them less likely to cause resistance

Answer 2

All have a beta-lactam ring Penicillins, cephalosporins, carbapenems (only human products available- no veterinary data yet) 1st line antibiotics -cidal, narrow spectrum, less s/e Resistance is often (but not always) due to beta-lactamase destruction of the pharmaceutically active beta-lactam ring Bacteria that are resistant to penicillins are usually resistant to the cephalosporins and vice-versa Patient with penicillin allergies also have allergies to other beta-lactams

Answer 3

Part of the beta-lactam antibiotics; contain a beta-lactam ring Mostly kill gram + bacteria Drug binds to the bacteria enzyme responsible for cross-linking the peptidoglycan layers that make up the cell wall Prevents stabalization of the cell wall; bacteria die from water entering the cell Only works on actively dividing bacteria

Answer 4

Bactericidal Bactericidal drugs have a lower risk of causing resistance when used correctly Narrow spectrum of activity Narrow spectrum drugs are less likely to cause resistance Older drugs only work on Gram+ Newer broad-spectrum drugs have some Gram - activity Fewer side effects Because animal cells do not have cell walls

Answer 5

Well absorbed from injection sites Excellent volume of distribution Drawn to inflamed tissues; can even penetrate abscesse

Answer 6

Not metabolized in liver Eliminated in active form in the kidneys; also found in active form in secretions (milk)

Answer 7

When given orally they may destroy beneficial Gram + bacteria residing in the lumen of the intestinal tract, allowing more pathogenic bacteria to proliferate Yogurt, pre/probiotics to counteract this Adverse reactions to penicillins are rare, but can include type I hypersensitivity reactions Must observe withdrawal times in food animals. Label all dispensed medications with clear instructions for proper administration and WTs

Answer 8

There is lots of resistance to the penicillins Via plasmids that contain the gene for the beta-lactamase enzyme Beta-lactamase cutes the beta-lactam ring so drug is no longer active This plasmid can be shared with other bacteria and is passed to progeny→ spread of resistance Enzyme inactivates any drug containing beta-lactam ring Penicillins, cephalosporins, carbopenams

Answer 9

Very narrow spectrum (gram + only)

Answer 10

Comes in various injectable formulations Formulations are NOT interchangeable Different pharmacokinetics result in different duration of effects Different withdrawal times

Answer 11

Na+/K+ Pen G (aqueous) IV or IM use Most commonly used, shortest acting (1h); 3 d WDT

Answer 12

Give IM only. NEVER give IV as it will cause sudden death due to heart block. 24 h duration Procaine reaction in horses Procaine will also test + at a horse show

Answer 13

Slow release formulation. 5d duration; 28d WDT

Answer 14

Broad spectrum = Gram + and a limited number of Gram - Binds to the surface of Gram - cell wall and prevents bacteria from adhering to surfaces and one another (prevents colonizing) Commonly used in SA

Answer 15

Ampicillin and Amoxicillin Injectable and oral form

Answer 16

These drugs are held in reverse, used to treat severe, resistant Gram - infections Activity against Pseudomonas and other gram - bacteria Batter able to penetrate the outer cell wall compared to other penicillins They are synergist when administered with aminoglycosides, and have good activity against anaerobes E.g. Ticarcillin, piperacillin, carbenicillin

Answer 17

amoxicillin/clavulanic acid (amoxi-clav)

Answer 18

Amoxicillin which has been combined with a second drug, clavulanic acid Clavulanic acid (or sulbactam) protect the penicillin from bacterial beta-lactamase enzymes Clavamox®; Noroclav®; Clavaseptin®

Answer 19

Fairly safe because animal cells do not have cell walls Side effects related to disturbance of normal flora, formulations, allergy GI issues Most common Only if given orally Vomit, diarrhea, inappetance Chemical irritation or disturbs normal flora Will decrease if given with food; BUT, giving with food decreases absorption May need to adjust dose or give 1h after feeding Rapid injection IV can cause neurological signs or anaphylaxis or sudden death allergies/anaphylaxis in animals and people can be very severe

Answer 20

Rapid injection IV can cause neurological signs or anaphylaxis or sudden death Anytime a penicillin is given IV, give by slow injection (a single dose over 10-20 min) Procaine PenG should NEVER be given IV (IM only) Giving IV causes acute excitement and death due to local anesthetic overdose Can occur when given IM if a small amount enters a vessel Horse hyperalert, spooked, may collapse, lasts 2-5 minutes

Answer 21

allergies/anaphylaxis in animals and people can be very severe Of all the beta-lactams, occurs most commonly with the penicillins PenG is naturally derived from the Penicillium fungus and has the highest risk of allergy Some animals/people with penicillin allergies may also react to cephalosporins and carbapenems More likely if injected Hives, swelling of throat, vomit, diarrhea, hepatitis, pruritus, vasodilation Watch WDTs in food animals

Answer 22

Recognize by “Cef” prefix Contain the beta-lactam ring Block cell wall synthesis Gram + bacteria Susceptible to beta-lactamase resistance Same plasmid-driven mechanism as for penicillins Concentration-dependent Very commonly used Names usually begin with “ceph-” or “cef-”

Answer 23

1st generation Oldest; gram + only Cephalexin -commonly used orally Cefazolin (Kefzol®)- surgical prophylaxis; slow IV over 20 min 3rd generation Cefovecin (Convenia®) Cefpodoxime (Simplicef®) Ceftiofur (Excenel®-SID;Excede®-2 treatments 5 days apart) Newer generations are broader spectrum (also get gram - and anaerobes) and have better tissue distribution

Answer 24

Cephalosporins Contains cefovecin (3rd gen) Long acting 14 days in therapeutic range after single SQ injection Has been over-used due to convenience; seeing increased resistance. Recommend susceptibility testing before use Reminder: always indicate current and rect antibiotics on lab submission forms Must be re-administered on (or before) day 14 if infection has not resolved completely

Answer 25

Cats that are difficult to pill UTI (off label) Soft tissues abscesses

Answer 26

GI issues if given orally Most common side effect if given orally Vomit, diarrhoea, inappetence due to chemical irritation or disruptions of GI flora Always give with food Needs to be written directly on the prescription label Allergy and anaphylaxis May or may not be related to penicillin allergy Incidence is lower than that seen in penicillins IM injection may be painful in LA

Answer 27

Recognized by “micin/mycin” suffix Damages the cell membrane and block protein synthesis Aerobic, gram -ve, bactericidal Concentration dependent Hydrophilic Very severe adverse effects

Answer 28

Usually found in topical eye and ear formulations; also in topical wound ointments Examples end in “micin (mycin)” Gentamicin (ear drops:Mometamax® otic, Otomax®; can be used short-term IV) Neomycin(Tresaderm®otic,Polysporin® wound ointments) Amikacin–broadest spectrum, infusion beads,can be used short- term IV Tobramycin–(Tobrex® ophthalmic drops)

Answer 29

TWO MAJOR adverse effects of ALL aminoglycosides are nephrotoxicity (kidney damage) and ototoxicity (damage to the auditory nerves and inner ear) Occur commonly Nephrotoxicity is reversible; ototoxicity is irreversible Increased risk with systemic administration; decreased risk if used locally Increased risk with longer duration of use Increased risk in older patients, patients with pre-existing renal or neurological issues

Answer 30

Very likely to occur if drug given systemically for more than 7 days Drug accumulates in renal tubule cells and is directly toxic to cells Must monitor for urine casts to detect damage to renal cells Must monitor for plasma levels to avoid toxic levels–therapeutic drug monitoring Increased risk if very young, very old, hypotensive, pre-existing renal disease

Answer 31

Damage to auditory nerves (deafness) and inner ear (vestibular toxicity) Neomycin, gentamycin most toxic These drugs are commonly found in SA ear meds Common adverse effect of use of topical ear meds

Answer 32

Ruptured eardrum Broken skin Cats Older Extended dosing If underlying neurological disease

Answer 33

Clinical signs: loss of hearing, pain, head tilt, loss of balance, Hoarders syndrome (unequal pupils, droopy lid) Stop meds→ flush ear with saline→ must be seen

Answer 34

Not a first line antibiotic Not approved for use in food-producing animals Based on culture and sensitivity only Usually given as a local drug Poor oral absorption, so should be OK if dog licks Do not use longer than prescribed even if topical Only use systemically under specific circumstances Use as per label Do not give more than recommended Do not give longer than recommended Follow all contraindications Do not use on pyogenic infection sites–inactivated by pus which is acidic

Answer 35

Recognized by ‘floxacin’ suffix Newest class of antibiotic Inhibits DNA replication; broad spectrum, -cidal Recommended to only be used for: Hospital-acquired infections (especially of the urogenital tract) For other severe infections only if there is proven resistance to other older antibiotic classes Still a reserved class in human medicine Names end in “-floxacin”

Answer 36

Arguably over-used in vet med Different routes available (oral and injectable) Wide-spread and excellent tissue penetration Treat skin, respiratory and urinary infections Newer drugs have once-a-day oral dosing Also found in many ear drops due to SID dosing Commonly used to treat bacterial infections in reptiles No quinolones approved and labeled for use in horses.

Answer 37

Disrupts joint formation in young animals Bubble-like lesions in cartilage Avoid or use with caution in young or growing animals Enrofloxacin can cause retinal damage in cats with potential for irreversible blindness High risk of creating antibiotic resistance

Answer 38

Binds to ribosomes and blocks protein synthesis Bacteriostatic Broadest spectrum of all antibiotic classes Gram + and Gram –, Mycoplasma, rickettsial organisms (Lyme, Anaplasmosis, Erlichia) Time dependant Lots of resistance Up to 30 different bacterial resistance genes have been identified

Answer 39

3 generations; vets have access to 1st and 2nd generation drugs 1st gen: tetracycline, oxytetracycline 2nd gen: minocycline, doxycycline 3rd gen (2005): reserved for human resistant cases Seeing lots of resistance, esp to 1st generation drugs Names end in“-cycline”

Answer 40

Commonly used in all SA and LA species Doxycycline is the drug of choice for tick borne diseases and heartworm Subtherapeutic doses added to feed shown to enhance growth Poultry, calves, pigs Banned for trade purposes in Europe, North America Commonly used to treat respiratory, urinary and skin infections, sepsis Including metaphylaxis of Shipping Fever

Answer 41

Cattle and horses do not tolerate oral dosing Check if formulation can be given IM, IV, SQ There are short-and long-acting injectable forms Long-acting IM forms commonly used in food animal production (up to q5d dosing) WDTs are very different for short- and long-acting IV injections are ALWAYS over 10-20 min Rapid IV will cause fatal arrhythmia and collapse Usually PO route in SA Give 1-2 hours apart from dairy products. If given WITH diary products, drug will bind to Ca+ and not get absorbed Always follow with some water after administering PO

Answer 42

Binds to calcium; binds to bone and teeth Causes yellow discoloration of teeth if given to young animals or pregnant/nursing animal May slow bone growth Avoid pregnant/growing animals Nausea, vomit, diarrhea, inappetance Due mostly to effects on normal flora Will help if given with food (not dairy) Esophageal necrosis Occurs if pill sticks to side of esophagus Highest risk in cats; can occur in any species **Owners MUST flush with a syringe of water after pilling Risk of fatal arrhythmia if given fast IV Due to chelation of calcium in blood; Ca+ is no longer available for muscle contraction Sudden collapse, death Horses most susceptible

Answer 43

Oxytetracycline is also used to treat contracted tendons in foals believed to chelate Ca in muscle therefore causes relaxation and allows limb to extend. Followed by bandaging/splinting. Must be done in the first few days after birth.

Answer 44

Recognized by “sulfa” prefix Anti-metabolites; inhibit folate synthesis to stop growth – bacteriostatic ; broad spectrum Excellent tissue distribution Goes everywhere incl. CNS, prostate, eye Lots of resistance, drug interactions and side effects

Answer 45

Feed additives stay in the GI tract and are NOT absorbed; used to treat coccidiosis in chickens Systemic sulfa drugs are given PO, IV, IM; enter plasma and used to treat tissue infections

Answer 46

Most commonly used systemic sulfa drug “Old drug” Occasionally used in SA, horses Used in food animals in Canada; banned in USA

Answer 47

KCS – keratoconjunctivitis sicca, “dry eye” Decreased tear production causes increased risk of corneal irritation and corneal ulcers May be permanent Watch for red eye, blinking, mucus coat over eyes Allergic skin reactions/rashes Hives, redness, pruritus, hives Crystallization of drug in the urine SA, dehydrated, if acidic pH Anorexia Bone marrow suppression Fever and polyarthritis Idiosyncratic fatal liver failure Hypothyroidism Teratogen – deformities in the neural tube due to folate deficiency Lots of drug interactions-fatal arrhythmias if given with detomidine in horses.

Answer 48

Bacterial protein inhibitors Bacteriostatic or cidal depending on concentration Works against anaerobes, gram positive aerobic cocci and toxoplamsa parasites Distributed to milk and can cause diarrhea in nursing young Can cross placenta Partially metabolized by liver Contraindicated for use in animals who rely on fermentation for digestion of food e.g. horses rodents, ruminants and rabbits

Answer 49

Effective drug for use in deep pyodermas, abscesses, dental infections, bite wounds and osteomyelitis IM, PO Most common adverse effect is GI upset Can happen with any route of delivery (PO or IM) Inappetance, vomit, diarrhea Discontinue drug usually recommended May see hypersalivation or lip smacking in cats after PO administration. IM injection may see pain at injection site

Answer 50

Bacteriostatic by inhibiting protein synthesis Primarily used to treat gram positive bacterial respiratory disease. Azithromycin(Zithromax®), and Erythromycin– human drugs Tilmicosin (Micotil®), Tylosin(Tylan®) and Tuliathromycin (Draxxin®)– Veterinary drugs

Answer 51

Commonly used in beef cattle and sheep Metaphylaxis and treatment of bovine shipping fever Long-acting injectable, q72h Give SQ ONLY (slows down absorption) Highly irritating if given IM

Answer 52

Improper use can cause cardiotoxicity Drug blocks Ca+-channels Tachycardia, decreased cardiac output, hypotension CAN BE FATAL If given IV Drug is contraindicated in horses, pigs, due to cardiotoxicity Also reported in people handling drug

Answer 53

Be fatal Exposure to scratches can cause severe inflammation, pain Low dose systemic exposure can cause dizziness, hypotension High dose systemic injection can cause cardiac arrest (5%) Use needle/syringe safety especially with: Pressurized injection guns Multi-dose syringes Carrying loaded syringes in pockets

Answer 54

Never attach needle to syringe containing drug until ready to use Wear gloves Avoid eye contact (can be absorbed via the conjunctiva) Never work alone with this drug Ensure proper restraint/chute system Lots of fatal drug interactions, so must be able to tell emergency workers name of drug Wash immediately in the event of spills or accidental contact

Answer 55

Used to treat a variety of anaerobic bacterial infections in small animal and horses. Banned from use in food animals Due to risk of fatal aplastic anemia in humans. Wear gloves when handling and avoid inhalation of powder. Wash hands after handling tablets or capsules Need to ensure owners are aware of fatal effects Inhibits Cyp450 enzymes

Answer 56

Similar to Chloramphenicol but lacks the functional group that causes aplastic anemia Commonly used in feedlot cattle and swine Only approved for use in these 2 species WDT Cattle Metaphylaxis and treatment of bovine shipping fever; foot rot and infectious bovine keratoconjunctivitis Long-acting IM injection Swine Added to feed for respiratory infections.

Answer 57

Local tissue reaction Can cause tissue loss at slaughter-go for neck/chest. Very bad if more than 10 ml per site given IM Inappetance, diarrhea Decreased water consumption Reversible bonemarrow suppression More common if chronic high dose Increased residues in the environment if using for metaphylaxis in feedlots Banned in dairy Avoid in horses due to possible fatal acute colitis

Answer 58

Bacterocidal Commonly used to treat SA diarrhea Anti-protozoal (Coccidia, Giardia,trichomonas...) Clostridia and other anaerobes (hoof abcesses – horses)

Answer 59

Can be given on an empty stomach Has a bitter taste and can cause vomiting and anorexia in small animals Must dilute and neutralize if giving IV Treated cattle must not be slaughtered for food Side effects can occur at therapeutic dose: Neurological effects (ataxia , vestibular signs, head tilt, abnormal nystagmus, disorientation) Tremor and seizures

Answer 60

Probiotic made by Iams Live bacteria are genetically modified to be resistant to metronidazole Given with metronidazole.

Answer 61

Right drug for the right bug Avoid sending ABCs to pacify owners Perform culture and sensitivity testing to ensure correct drug Avoid prophylactic use Maintain therapeutic range Correct mg/kg dose Correct frequency of dosing Correct route of administration Avoid ELDU Treat until the infection has resolved Do not stop just because clinical signs have resolved Have patient come back for recheck Ensure negative culture Only dispense one course at a time No “standing” repeats for antibiotics Prevents hoarding and/or intermittent use Preventing residues (adhering to WDTs) Avoid ELDU Also address hygiene, husbandry, wound care Client communication to ensure owner compliance

Answer 62

Explain dosing frequency Ex. q12h (not BID) Finishing the prescribed amount Explain need to complete a full course; do not stop just because symptoms have resolved Do not stock-pile, do not give excess Explain about resistance issues Show owners how to give Poor compliance is often because of difficulty/inconvenience Emphasize need for rechecking to ensure infection has resolved Go over side effects GI upset is very common for PO routes Most common signs of GI upset? Give with food (most antibiotics) Tetracyclines – wash down after pilling, avoid giving with dairy Common side effects Give WDT if food animal OR horse Follow-up To identify adverse effects when they occur

Answer 63

Used to treat mycoses (fungi diseases) Infections can be superficial (Malassezia, Dermatophytes) or systemic (blastomycosis) Mechanism of action Damage cells; usually cell membranes Blocks cell replication Drug must be protected from light

Answer 64

Lower therapeutic index than antibiotics Fungi and animal cells are both eukaryotic Lots of common structures and proteins Consider all to be teratogenic: Never use in any pregnant animal Wear gloves to handle if pregnant

Answer 65

Polyenes Amphotericin B, Nystatin, Azoles Ketoconazole (Nizarol®) Itraconazole, fluconazole Antimetabolites Superficial anti-dermatophytes Griseofulvin B

Answer 66

Examples: nystatin, amphotericin B Binds to sterols located in fungal cell membrane and punches holes into cells Very severe side effects if systemic Binds cholesterol in patient’s cell membranes Kidney damage in 80% patients at therapeutic dose Severity of disease must justify systemic use

Answer 67

IV injectable –amphotericin B To treat very severe systemic mycosis Rapid onset (hours) Will cause systemic toxicity Topical polyenes - nystatin Local application decreases systemic toxicity Commonly found in skin creams (polysporin, diaper creams) and ear drops Very poor oral bioavailability

Answer 68

#1 choice of anti-fungal when possible due to fewer side-effects “-azoles” ketoconazole (Nizarol®) (oral, topical) itraconazole (oral and topical; cats) fluconazole (oral, IV) miconazole (topical, infusion) clotrimazole (topical, infusion)

Answer 69

Disrupts fungal cell membrane synthesis Fewer side effects than previous class; but slower onset of action (5-10 days) Oral, injectable and topical formulations Commonly used: Ringworm Allergic yeast dermatitis Very severe yeast otitis

Answer 70

GI upset – nausea, vomit, inappetance Can decrease by splitting single large dose into smaller doses throughout day Hepatotoxicity Older animals, pre-existing liver damage, prolonged treatment Inhibits cytochrome P450 activity Can increase toxicity of other drugs Decreases steroid production Suppresses adrenal gland function ketoconazole is used to treat Cushing’s disease; it damages the adrenal glands in a reversible manner Can cause an iatrogenic Addison’s disease Teratogenic

Answer 71

Still used, but less common than in past Treatment of superficial dermatophytoses (ringworm) in dogs, cats, horse Oral formula only

Answer 72

GI effects: inappetance, vomit, diarrhea Teratogen - NEVER USE IN PREGNANT ANIMALS Cats more susceptible to toxic effects Teratogenic in cats

Answer 73

Viruses cannot replicate on their own MUST infect a host cell and use the host cell’s enzymes to replicate Opportunities to stop virus infections: Inactivate the free virion Prevent attachment/entry Kill virus factories (i.e., infected host cells) Block viral enzymes involved in replication – very few of these; most are hard to access and rapidly mutate

Answer 74

Viruses are hard to treat, because would require damaging the body’s own cells that virus has infected Antibiotics do NOT work on viruses Knowing whether a disease is caused by a virus is important when talking to owners Most effective way to treat a virus infection is to boost the body’s own immune response to the virus Vaccines

Answer 75

Preventing transmission and vaccinations are keystone to control of viral infections Limited number of anti-virals exist Limitations due to: Virus have limited targets Limited access due to intracellular infection Risk/damage to infected host cells

Answer 76

Drug to treat HIV in humans Inhibits viral RNA replication enzymes Has been used treat FIV ($$$$)

Answer 77

Treat herpes virus (ex.feline herpesvirus) Inhibits viral DNA replication Adverse effects: may cause GI upset if given orally

Answer 78

Non-specific anti-viral; works against all viruses Part of innate immune response and blocks entry of virus into adjacent cells Questionable efficacy, but few side effects Will use to treat severe FURD, FeLV, FIP

Answer 79

Amino acid Nutraceutical; OTC Anti-herpes virus activity (respiratory disease cats) Available as powders, foams, gels, treats

Unit 3 antimicrobials Flashcards

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