Equine antibiotics Flashcards

1
Q

Penicillins: Mechanism of action? Bactericidal or static? Indications? When not used? Drug examples? Adverse effects?

A

Mechanism of action: interfere with bacterial cell wall production -> cell lysis
Bactericidal
Indications:
- G+ves
- first choice for Strep infections in horses
- most anaerobic infections
- synergistic with ahminoglycosides
Limited efficacy in abscesses (due to pH)
Poor penetration into CNS
Procaine penicillin most common in UK - IM
Adverse effects:
- anaphylaxis (type I hypersensitivity)
- haemolytic anaemia (penicillin accumulates on RBC wall)
- thrombocytopenia (type II)
- procaine penicillin: CNS signs (seizures etc) if IV or hot weather (penicillin and procaine separate if hot)

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2
Q

Cephalosporins: mechanism of action? Effective against? Adverse effects?

A

Mechanism of action: interfere with bacterial cell wall production -> cell lysis
More resistant to bacterial defences than Beta lactams
Earlier generations: mostly G+ves, very similar to penicillins
Later generations: more broad spectrum to include G-ves
Adverse effects (same as pencillins):
- anaphylaxis (type I hypersensitivity)
- haemolytic anaemia (penicillin accumulates on RBC wall)
- thrombocytopenia (type II)

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3
Q

Aminoglycosides: Mechanism of action? Concentration or time dependent? Cidal or static? Examples? Indications?

A
Mechanism of action:
- penetrate bacteria (actively pumped into cell by G-ves) and bind to 30S ribosomal subunit -> misreading of genetic code
- bactericidal
- concentration dependent (give once at high dose and lasts long time)
Examples:
- gentamicin
- amikacin
- neomycin
- streptomycin
- tobramycin
Indications:
-  G-ves
- Pseudomonas
- good for urinary infections but most common adverse effect is renal damage so be careful
Adverse effects:
- nephrotoxicity (avoid in dehydrated/renal disease or with other nephrotoxic drugs, monitor urinary GGT/creatinine, BUN, creatinine)
- endotoxaemia (death of G-ves)
- ototoxicity (not common)
- neuromuscular blockage (not common)
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4
Q

Why are aminoglycosides nephrotoxic and can cause acute kidney disease?

A

Enters tubules after filtration

  • > Uptake by cells
  • > Accumulates in lysosomes
  • > Lysosome rupture
  • > Cell damage
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5
Q

Chloramphenicol: mechanism of action? Bacteriocidal or static? Indications? When not used? Adverse effects?

A

Mechanism of action:
- binds to 50S ribosomal subunit -> inhibits protein synsthesis
- bacteriostatic (don’t use if immunosuppressed)
Indications:
- broad spectrum
- typically only used in form of eye drops
Forbidden in food production animals
Adverse effects:
- don’t give with bactericidals
- colitis
- aplastic anaemia in humans

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6
Q

Potentiated sulphonamides: What are they? Mechanism of action? When not effective? Indications? Adverse effects?

A

Combination of sulphonamide and diaminopyrimidine
Mechanism of action:
- inhibit folic acid pathway: blocks bacterial nucleic acid synthesis
- diaminopyrimidine affects folic pathway at different step
Ineffective in pus and necrotic tissue (lots of folic acid already so bacteria doesn’t need to make its own)
Indications:
- broad spectrum: Strep, Staph, some G-ves (E.coli, Salmonella)
- good for hepatic and renal infections
Ineffective against most anaerobes
Ineffective for S equi equi
Adverse effects:
- agranulocytosis, anaemia, thrombocytopenia
- crystalluria
- diarrhoea
- rapid IV administration -> collapse!
- fatal dysrhythmias when given with detomidine

So give IV slowly and don’t give in sedated horses

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7
Q

Tetracyclines: Mechanism of action? Bactericidal or static? Indications? Adverse effects?

A

Mechanism of action:
- binds to 30S ribosomal subunit -> inhibits protein synthesis
- bacteristatic
- mammalian cells cannot transport into cell
Indications:
- broad spectrum: G+ and G-, some anaerobes, Chlamydia, Mycoplasma, Ehrlichia, Ricketssia, some protozoa
- contracted tendons in foals (chelates calcium at myotendinous junction)
- doxyxycline inhibits MMPs - keratomalacia and IMMK
- good penetration (good for abscesses, intracellular infections etc)
Adverse effects:
- fatal colitis
- rapid IV -> collapse and death
- discolouration of teeth
- doxy - oral ulceration

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8
Q

Fluoroquinolones: Mechanism of action? Bactericidal or static?

A

Mechanism of action:
- inhibit bacterial DNA gyrase -> abnormal spatial configuration of DNA
- autolysines produced by bacteria kill damaged DNA
- need optimal bactericidal concentration (if too high bacteria can’t produce autolysines)
Indications:
- broad spectrum: most aerobic G-ves, some aerobic G+ves, Mycoplasma, Chlamydia, Rickettsia
- very effective against enteric G-ves (Salmonella)
Ineffective against anaerobic bacteria (beneficial in enteric infections)
Adverse effects:
- cartilage lesions (foals)
- antagonistic to antibiotics that inhibit bacterial protein synthesis (chloramphenicol, rifampin)

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9
Q

Macrolides: mechanism of action? Bacteriocidal or static? Examples? Indications? Adverse effects?

A

Mechanism of action:
- binds to 50S ribosomal subunit -> inhibits protein synthesis
- bacteriostatic
- resistance develops quickly so always given with another drug
Examples:
- erythromycin
- claruthromycin
- azithromycin (foals only)
- clindamycin and lincomycin not used in horses
Indications:
- associated with causing colitis in adult horses so restricted to treatment of Rhodococcus equi in foals
- pro kinetic (small dose IV)
Adverse effects:
- colitis and diarrhoea in adults
- hyperthermia (be careful using in hot weather)

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10
Q

Rifampin: Mechanism of action? Indications? Adverse effects?

A
Mechanism of action:
- inhibits bacterial RNA polymerase -> inhibits RNA synthesis
- no effect on mammalian cells
- rapid development of resistance (used with another drug)
Indications:
- Staph
- Rhodococcus equi (main use, in combo with macrolides)
- Mycobacteria
- Some viruses and fungi
Adverse effects:
- stains everything it contacts red
- red urine, faeces, tears, saliva
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11
Q

Metronidazole: Mechanism of action? Indications? Adverse effects?

A
Mechanism of action:
- anaerobic bacteria take up and break into small free radicals -> DNA damage
Indications:
- anaerobes
- protozoa (Giardia)
Adverse effects:
- mutagenic
- neurotoxicity
- depression and reduced appetite (poor palatability so can give rectally if makes horse feel worse orally)
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12
Q

When do wounds no longer need antibiotics usually?

A

Generally not needed once granulation tissue established

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13
Q

What does PROTECT ME stand for for antibiotic usage in horses?

A
Practice policy
Reduce prophylaxis
Other options
Types of drugs and bacteria
Employ narrow spectrum drugs
Culture and sensitivity
Treat effectively

Monitor
Educate

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14
Q

Which antibiotics can be given orally?

A
Doxycycline
Trimethoprim/sulphadiazine
Rifampin
Azithromycin
Enrofloxacin
Metronidazole
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15
Q

Which antibiotics are first line in horses?

A
Procaine penicillin
Sodium penicillin
Oxytetracycline
TMPS
Gentamicin
Neomycin
Rifampin
Azithromycin
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16
Q

Which antibiotics are protected in horses?

A

Benthazine penicillin (LA)
Ceftiofur
Cefquinome
Enrofloxacin

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17
Q

What first line antibiotic would be used for strangles?

A

Not indicated if abscessed formed

Penicillin first line for prophylaxis/airway obstruction

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18
Q

What first line antibiotic would be used for primary sinusitis?

A

Penicillin

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19
Q

What first line antibiotic would be used for secondary pneumonia (e.g. following RAO)?

A

TMPS

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20
Q

What first line antibiotic would be used for guttural pouch empyema/chondroids?

A

Penicillin

???

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21
Q

What first line antibiotic would be used for URT diseases which are not strangles or primary sinusitis?

A

TMPS

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22
Q

What first line antibiotic would be used for primary pneumonia?

A

Penicillin and gentamicin

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23
Q

What first line antibiotic would be used for Rhodococcus pneumonia?

A

Rifampin and azithromycin

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24
Q

What first line antibiotic would be used for contaminated wounds with synovial sepsis?

A

Penicillin and gentamicin

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25
Q

What first line antibiotic would be used for contaminated wound with open fracture

A

Penicillin, gentamicin and metronidazole

26
Q

What first line antibiotic would be used for contaminated wounds on limbs?

A

TMPS

27
Q

What first line antibiotic would be used for non complicated contaminated wounds?

A

Not indicated

TMPS if later needed

28
Q

What first line antibiotic would be used for cellulitis?

A

TMPS

29
Q

What first line antibiotic would be used for a sub solar abscess?

A

Not indicated

30
Q

What first line antibiotic would be used for a sub solar abscess with P3 involvement?

A

Oxytetracycline/doxycycline

31
Q

What first line antibiotic would be used for pyoderma?

A

TMPS

32
Q

What first line antibiotic would be used for periodontal disease?

A

TMPS

33
Q

What first line antibiotic would be used for periapical abscessation?

A

Oxytetracycline/doxycyline

34
Q

What first line antibiotic would be used for acute diarrhoea?

A

Not indicated

35
Q

What first line antibiotic would be used for bacterial cholangiohepatitis?

A

TMPS

Submit biopsy sample for culture

36
Q

What first line antibiotic would be used for mild peritonitis?

A

TMPS

37
Q

What first line antibiotic would be used for severe peritonitis?

A

Penicillin and gentamicin

38
Q

What first line antibiotic would be used for cystitis or pyelonephritis?

A

TMPS

39
Q

What first line antibiotic would be used forest foaling endometritis?

A

Penicillin and neomycin

40
Q

What first line antibiotic would be used forest covering endometritis?

A

IU penicillin

41
Q

What first line antibiotic would be used for mastitis?

A

TMPS

42
Q

What first line antibiotic would be used for conjunctivitis?

A

Fucidic acid

43
Q

What first line antibiotic would be used for mild corneal ulceration?

A

Chloramphenicol

44
Q

What first line antibiotic would be used for severe corneal ulceration?

A

Gentamicin and chloramphenicol

45
Q

What first line antibiotic would be used for a melting corneal ulceration?

A

Ciprofloxacin

46
Q

What first line antibiotic would be used for endocarditis?

A

Penicillin and gentamicin

47
Q

What first line antibiotic would be used for neutropenia <2.5x10^9/L and PUO?

A

TMPS

48
Q

What first line antibiotic would be used forneutropenia <1x10^9/L?

A

Penicillin and gentamicin

49
Q

What first line antibiotic would be used for neonatal pneumonia?

A

Cefquinome (protected but justified in neonate due to high mortality)

50
Q

What first line antibiotic would be used for neonatal septic arthritis?

A

Penicillin and gentamicin

51
Q

What first line antibiotic would be used for neonatal patent urachus?

A

TMPS

52
Q

What first line antibiotic would be used for neonatal umbilical infection?

A

TMPS

53
Q

What first line antibiotic would be used for neonatal sepsis

A

Cefquinome

54
Q

What first line antibiotic would be used for normal foal post foaling?

A

Not indicated

55
Q

What first line antibiotic would be used for normal foal with unobserved foaling?

A

TMPS

56
Q

What first line antibiotic would be used for premature/dysmature foal?

A

TMPS

57
Q

What first line antibiotic would be used for meningitis of neonate?

A

TMPS

58
Q

What pre-op and post-op antibiotics would be used for a clean surgery?

A

Pre-op: penicillin

Post-op: penicillin TID IV or BID IM for 24h

59
Q

What pre-op and post-op antibiotics would be used for a contaminated surgery?

A

Pre-op: penicillin and gentamicin

Post-op: penicillin and gentamicin for 5 days

60
Q

What pre-op and post-op antibiotics would be used for a high risk surgery

A

Pre-op: penicillin and gentamicin

Post-op: penicillin and genticimic for 10 days, then reassess (consider TMPS if longer treatment required)