Reference Tables

Suggested Treatment Options by Condition [Equine]

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(C/S = culture and susceptibility testing)

Cardiovascular Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Bacterial endocarditis
  • Pasteurella spp.
  • Actinobacillus spp.
  • Streptococcus spp.
 Penicillin + (Gentamicin or Enrofloxacin) Rifampin + antibiotic chosen based on C/S

Central Nervous System Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Intracranial abscess
  • Streptococcus equi equi
 Penicillin ± Trimethoprim-sulfa Chloramphenicol Antibiotic therapy should be used in combination with surgical debridement
Meningitis
  • Mannheimia haemolytica
  • Actinomyces spp.
  • Klebsiella spp.
  • Streptococcus spp.
 Chloramphenicol or Trimethoprim-sulfa Ceftriaxone
Tetanus
  • Clostridium tetani
 Metronidazole or Penicillin Broad-spectrum therapy is indicated in cases of suspected aspiration pneumonia secondary to tetanus

Gastrointestinal Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Bacterial cholangiohepatitis
  • Salmonella spp.
  • Escherichia coli
  • Pseudomonas spp.
  • Actinobacillus equuli
  • Clostridium spp.
  • Pasteurella spp.
  • Streptococcus spp.
 Penicillin + Gentamicin Trimethoprim-sulfa Submit biopsy for C/S
Choke – prophylaxis against pneumonia
  • Streptococcus zooepidemicus
  • Rhodococcus equi
 Trimethoprim-sulfa ± Metronidazole Penicillin + Gentamicin
Diarrhea – acute
  • Salmonella spp.
  • Clostridium spp.
  • Neorickettsia risticii
  • Aeromonas spp.
  • Lawsonia intracellularis
  • Escherichia coli
  • Actinobacillus spp.
 Antibiotic selection based on most likely differential diagnosis (e.g. oxytetracycline for PHF, metronidazole for clostridial diarrhea) Penicillin + Gentamicin ± Metronidazole C/S indicated to confirm diagnosis and further guide antimicrobial selection
Diarrhea – chronic (>1mo duration) (See note) C/S indicated prior to choosing treatment
Peritonitis – primary
  • Actinobacillus equuli
  • Escherichia coli
  • Staphylococcus spp.
  • Streptococcus spp.
  • Bacteroides fragilis, Clostridium spp.
 Penicillin ± Gentamicin Trimethoprim-sulfa Actinobacillus equuli is the most common causative agent; confirm with C/S
Peritonitis – secondary
  • Rhodococcus equi mixed infections common
 Penicillin + (Gentamicin or Enrofloxacin) + Metronidazole Chloramphenicol Substitute amikacin for gentamicin in foals; a macrolide + rifampin can be appropriate in older foals with R. equi peritonitis

Hoof and Skin Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Cellulitis
  • Staphylococcus aureus
  • Streptococcus spp.
 Trimethoprim-sulfa or (Penicillin + Gentamicin)
 Oxytetracycline or Doxycycline Use of regional limb perfusion or antibiotic impregnated beads, typically containing aminoglycosides, are also recommended
Pyoderma
  • Staphylococcus aureus
  • Staphylococcus intermedius
  • Corynebacterium pseudotuberculosis
 Trimethoprim-sulfa Oxytetracycline or Doxycycline
Subsolar abscess Not indicated Oxytetracycline or Doxycycline
Subsolar abscess – with P3 involvement
 Oxytetracycline or Doxycycline Penicillin + Gentamicin + Metronidazole

Muscle, Bone, and Joint Infections ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Clostridial myositis Metronidazole + Penicillin
Internal abscesses Penicillin + Rifampin Trimethoprim-sulfa + Rifampin Addition of rifampin to penicillin enables penicillin to more easily enter abscesses
Septic arthritis/osteomyelitis
  • Streptococcus zooepidemicus
  • Escherichia coli
  • Actinobacillus spp.
  • Staphylococcus spp.
  • Salmonella spp.
 Chloramphenicol Penicillin + Gentamicin ± Metronidazole Systemic therapy in combination with intra-articular injections or implantation of antibiotic impregnated beads is also recommended

Neonatal Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Meningitis
  • Actinobacillus equuli
  • Rhodococcus equi
  • Streptococcus spp.
  • Staphylocccus spp.
 Cefotaxime or Chloramphenicol
 Ampicillin + Amikacin
Omphalitis (umbilical infection)
  • Escherichia coli
  • Streptococcus zooepidemicus
 Trimethoprim-sulfa or (Penicillin + Gentamicin) Cefpodoxime
Patent urachus
  • Escherichia coli
  • Streptococcus spp.
  • Staphyloccus spp.
 Trimethoprim-sulfa or (Penicillin + Gentamicin) Cefpodoxime
Pneumonia – non-Rhodococcus equi
  • Streptococcus zooepidemicus
  • Streptococcus equi
  • Actinobacillus spp.
  • Pseudomonas aeruginosa
 Penicillin or Ceftiofur Penicillin + Gentamicin
Pneumonia
  • Rhodococcus equi
 Clarithromycin + Rifampin Doxycycline + Rifampin Erythromycin or azithromycin can be substituted for clarithromycin
Septic arthritis
  • Streptococcus zooepidemicus
  • Escherichia coli
  • Actinobacillus spp.
  • Salmonella spp.
 Penicillin + Amikacin ± Metronidazole Oxytetracycline Obtain blood C/S to guide treatment
Sepsis
  • Rhodococcus equi
  • Streptococcus spp.
  • Salmonella spp.
  • Escherichia coli
  • Actinobacillus spp.
  • Klebsiella spp.
  • Enterobacter spp.
  • Pseudomonas spp.
  • Clostridium spp.
 (Penicillin or Ampicillin) + Amikacin ± Metronidazole Cefotaxime or Ceftazidime or Ceftriaxone If sepsis is secondary to Rhodococcus equi pneumonia, treat as described above for pneumonia

Ocular Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Corneal ulceration
  • Streptococcus zooepidemicus
  • Pseudomonas aeruginosa
 Neomycin-Polymyxin B-Bacitracin Ofloxacin Used as a topical treatment; C/S recommended
Corneal ulceration – w/ melting
  • Pseudomonas aeruginosa
  • Staphylococcus spp.
  • Streptococcus spp.
 Levofloxacin Chloramphenicol Used as a topical treatment; antibiotic to be given in combination with an antifungal (e.g. voriconazole); C/S recommended

Prophylaxis ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Clean Surgery
 Penicillin
Contaminated Surgery Penicillin + Gentamicin
High-risk surgery Penicillin + Gentamicin

Respiratory Tract Diseases – Lower Respiratory Tract ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Pleuropneumonia
  • Streptococcus equi zooepidemicus
  • Escherichia coli
  • Actinobacillus spp.
  • Klebsiella spp.
  • Enterobacter spp.
  • Staphylococcus aureus
  • Pasteurella spp.
  • Bacteroides spp.
  • Clostridium spp.
 Penicillin + Gentamicin ± Metronidazole Chloramphenicol
Pneumonia
  • Streptococcus equi zooepidemicus
  • Escherichia coli
  • Actinobacillus spp.
  • Klebsiella spp.
  • Enterobacter spp.
  • Staphylococcus aureus
  • Pasteurella spp.
  • Bacteroides spp.
  • Clostridium spp.
 (Penicillin + Gentamicin) or Ceftiofur Penicillin + (Gentamicin or Enrofloxacin) C/S recommended to guide therapy, particularly in cases of bronchopneumonia; ampicillin can be substituted for penicillin
Pneumonia
  • Rhodococcus equi
 Clarithromycin + Rifampin Doxycycline + Rifampin Substitute clarithromycin for gentamicin in foals

Respiratory Tract Diseases – Upper Respiratory Tract ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Guttural pouch empyema
  • Streptococcus equi
  • Streptococcus zooepidemicus
 Penicillin Oxytetracycline or Doxycycline
Primary sinusitis
  • Streptococcus spp.
 Penicillin Trimethoprim-sulfa
 Antibiotics should be used in conjunction with lavage to remove purulent material
Strangles
  • Streptococcus equi subsp. Equi
 Penicillin Trimethoprim-sulfa Horses in the early stages of disease (pre-lymphadenopathy and abscessation) are the most likely to benefit from antimicrobials, but antibiotic treatment can prevent development of protective immunity

Urogenital Diseases ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Cystitis
  • Escherichia coli
  • Streptococcus spp.
  • Enterococcus spp.
  • Staphylococcus spp.
 Trimethoprim-sulfa Penicillin + Gentamicin Sulfadiazene retains more activity after urinary excretion than sulfamethoxazole
Leptospirosis
  • Leptospira spp.
 Penicillin Oxytetracycline
Mastitis
  • Streptococcus zooepidemicus
  • Other Streptococcus spp.
 Trimethoprim-sulfa Penicillin ± aminoglycoside antibiotic C/S recommended to guide antimicrobial choice; cattle intramammary infusion products may be used off-label until selection of a systemic antibiotic can be made
Metritis
  • Streptococcus zooepidemicus
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Klebsiella pneumonia
  • Taylorella equigenitalis
 Penicillin + (Amikacin or Gentamicin) ± Metronidazole Penicillin + Gentamicin Given as a uterine lavage for endometritis
Pyelonephritis
  • Escherichia coli
  • Streptococcus zooepidemicus
  • Staphylococcus aureus
  • Corynebacterium spp.
 Trimethoprim-sulfa Penicillin Sulfadiazine retains more activity after urinary excretion than sulfamethoxazole

Wounds ↩

Condition Targeted Organisms First Line Alternative Treatment Notes
Contaminated – non-complicated Not indicated Trimethoprim-sulfa
Contaminated – on limbs
 Trimethoprim-sulfa Oxytetracycline or Doxycycline
Contaminated – w/ open fracture
 Penicillin + Gentamicin + Metronidazole
Contaminated – w/ synovial involvement
 Penicillin + Gentamicin Oxytetracycline + Metronidazole

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OSU VMC Antimicrobial Use Guidelines Copyright © 2018 by The Ohio State University College of Veterinary Medicine is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.