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14 Initial Treatment

Jan reluctantly agrees to the urine culture saying, “Well, I guess if that’s what we need to do.  No offense doc, but I certainly don’t want to be in here for the same problem in another month!” 

Initial Treatment: 
While waiting for urine culture results, you prescribe an analgesic (Buprenorphine, 0.01mg/kg q 8 to 12 hours between the cheek and gums) to keep Nemo comfortable.  You tell Jan that the urine culture and sensitivity should be available in 2 days.  If Nemo stops producing urine or continues to be uncomfortable, she needs to bring him back in immediately!  You explain that a blockage in the urinary tract is a life-threatening situation.

Empiric antibiotic therapy is the use of an appropriate antibiotic when the exact etiologic agent is unknown. 




When is it okay to use empiric antibiotic therapy?

Emperic antibiotic therapy should only be started when depriving a patient of therapy (while waiting for urine culture and sensitivity results) may result in harm or worsening of the condition. 

  • When the agent is not known, selection of the antibiotic should be based on the most likely agent to be found in that location. 
  • Antibiotic selection needs to be selected not only on the suspected agent, but also on the ability to obtain a therapeutic concentration at the site of infection.  For most tissues, plasma concentration can be used to predict tissue concentration.  However, areas with poor blood supply can be problematic (abscesses).  Lipid membranes can also affect drug profusion (CNS, eye, prostate).



Guidelines for Emperic Antibiotic Therapy:




Antimicrobic Options

Urinary tract infection

E. coli, Proteus, Pseudomonas, Enterobacter, Pasteurella (more in cats), Staphylococcus, Streptococcus, and Enterococcus

First choices:

  • Amoxicillin + clavulanate; cephalosporins


  • Sulfonamides; fluoroquinolones; tetracyclines

In uncomplicated, never before treated, lower urinary tract infections in immunocompetent animals, amoxicillin + clavulanate is very effective against the most common pathogens (sulphonamides work better against E. coli)


E. coli, Staphylococcus, Klebsiella, Proteus, and Mycoplasma canis

First choices:

  • Sulfonamides; enrofloxacin


  • Doxycycline; erythromycin (gram-positives only)


Usually mixed with E. coli in complicated cases

First choices:

  • Amoxicillin + clavulanate; fluoroquinolones


  • Cephalosporins (do not effectively cross the blood-bronchus barrier; work for pneumonia)
  • Aminoglycosides (do not effectively cross the blood-bronchus barrier)
  • Sulphonamides
  • Clindamycin (Streptococcus)


Dogs: Staphylococcus, E. coli, Streptococcus, Salmonella, Proteus


E. coli, Klebsiella, Salmonella, anaerobes


First choices:

  • Amoxicillin + clavulanate + fluoroquinolone
  • Cephalosporin + fluoroquinolone


  • Second or third generation cephalosporins
  • Aminoglycosides (gram-negative)
  • Clindamycin (anaerobes)





Empiric Antibiotic Therapy, World Small Animal Veterinary Association World Congress Proceedings, 2009.  Helio Autran de Morais, DVM, PhD, AVCIM; Oregon State University



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