Pet Medication: Antibiotic Use and Misuse

By T. J. Dunn, Jr., DVM

Returning to his lab one morning in 1928 after a two-week vacation, Scottish microbiologist Sir Alexander Fleming realized that one petri dish inoculated with Staphylococcus bacteria had been accidentally left open. About to dispose of the worthless moldy dish, he noticed a clear halo devoid of any bacterial overgrowth surrounding each mold colony.

For some strange reason the bacteria weren’t growing in these small halos of agar surrounding the greenish mold.

Curious, as all scientists are, he asked himself why not? Instead of discarding the "contaminated" petri dish, he explored the antibacterial properties of the unusual mold, called Penicillium notatum, and the rest is history.

Since Fleming’s discovery of penicillin huge strides have been taken in the research and development of wide varieties of antimicrobial chemicals, and researchers continue to seek newer, safer, and more effective methods of interfering with bacterial and other microorganism replication.

One of the greatest challenges veterinary and human doctors face today is to make appropriate antibiotic selections that effectively help the patient recover from bacterial, yeast and fungal infections -- while at the same time not harming the patient.

How would harm come to a patient being administered antibiotics? One common example is the over-prescribing of antibiotics -- using them when not really indicated.

Recently a young Wirehaired Fox Terrier was presented to me because of sudden onset of loose, foul smelling stool. There was no history of the dog having eaten anything unusual, the diet was excellent, no intestinal parasites were evident on the fecal analysis, and the patient was not dehydrated, vomiting, nor acting depressed. The temperature was normal and abdominal palpation revealed a loose, gassy and non-painful character.

My diagnosis was a viral enteritis -- call it "intestinal flu," if you like. After discussing my diagnosis, and my preferred treatment of withholding all dog food for 24 hours, allowing plenty of fresh water, and simply allowing the dog to eat small amounts of yogurt every two hours until the following day, the owner asked ,"Aren’t you going to give him some antibiotics?"

I had to convince the concerned and skeptical owner that if my diagnosis was correct, this patient did not need antibiotics and in fact might develop a much worse diarrhea if we went that route. Plus, once an antibiotic is used in a patient there is the potential for that patient to develop a resistant population of bacteria. And someday, when antibiotics are truly needed, if that antibiotic is chosen as a treatment the infection may be refractory to the drug.

What this patient needed was to have "good" bacteria reintroduced into the gastrointestinal tract so that the correct balance of bacterial flora could be reestablished. Antibiotic administration should be reserved for patients who truly need them. Indiscriminate or casual use of antibiotics may lead to bacterial resistance in a patient as well as set up the potential for a future allergic reaction to the drug.

Conversely, in urinary tract infections and in skin infection cases called pyoderma, long-term administration of antibiotics may be necessary to eliminate tough infections. Often, with pyoderma, antibiotics are actually under-prescribed.

According to veterinary dermatologist Rusty Muse of Tustin, California, most pyoderma cases require an appropriate antibiotic for as long as six to eight weeks to be effective.

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