7. Wrap up
Don says, You commented that veterinarians synthesize clinical and diagnostic data to select antimicrobials for treatment. Could you expand on this further?
Sue says, The initial decision is not which antimicrobial to use, but rather regards whether or not there is sufficient evidence to support the diagnosis of a bacterial infection. Veterinarians use a variety of information to make this decision, which typically includes a history gathered from the client, a physical examination of the pet and knowledge of the diseases that are associated with the affected body site or sites. This includes knowledge of the frequency of diseases observed in their own practice and the underlying causes of disease, such as non-infectious causes like metabolic or degenerative diseases and toxicities, or infectious causes which can include bacterial, viral or fungal agents.
Only diseases associated with bacterial agents may need antimicrobial therapy. In the previous examples, uncomplicated feline upper respiratory tract disease is frequently associated with viral agents, so antimicrobials may not be beneficial in treating this condition. As well, feline lower urinary tract disease is frequently not associated with any infection (i.e. sterile) and so consequently antimicrobial use usually would not be beneficial.
Some diseases like canine kennel cough may be associated with a bacterial infection, but usually don’t need antimicrobial treatment as they are often self-limiting. It is important to understand that antimicrobial use may be associated with adverse events like allergic reactions (including anaphylaxis), vomiting, diarrhea, and selection pressure for antimicrobial resistance. Further, you will be billing the client for medications that may not be necessary, some of which are expensive. Therefore, unnecessary use of antimicrobials may be associated with negative, unwarranted consequences.
Don says, The information that veterinarians use to make decisions about antimicrobial use seems somewhat subjective. Are there any tests that veterinarians can use to help with the decision-making process?
Sue says, Most clinical decisions are some-what subjective. Obtaining objective data can improve the clinical decision process and this can be as simple as taking a temperature or heart rate. For suspected or known bacterial infections, bacterial culture and antimicrobial susceptibility testing is a diagnostic test that can be used to support the diagnosis and guide treatment. This simply involves gathering the appropriate sample, such as urine if a bladder or kidney infection is suspected and sending this to an accredited diagnostic laboratory. There they grow the bacteria and then test the bacteria to see which antimicrobials are effective. The results are usually available in 48 hours for most infections. It is a very cost effective test especially when compared to other common diagnostics tests like serum biochemistry and thyroid panels. Unfortunately, it is an underutilized diagnostic test. In one population of veterinarians, over a 12 month period, data on over 1,000 antimicrobial prescriptions was collected and only 40 bacterial culture and antimicrobial susceptibility tests were performed to support the diagnosis for which these prescriptions were prescribed (2). As with every diagnostic test, it has some limitations. Some argue that they are going to treat with antimicrobials anyway and therefore a culture and susceptibility would needlessly waste a client’s money. In some cases, immediate and, appropriate antimicrobial treatment can save an animal’s life. Even in these situations, performing a culture and susceptibility is beneficial because veterinarians can use this information to choose the most appropriate antimicrobial once the results are available. In some cases, this could actually save a client’s money because veterinarians may learn that a cheaper antimicrobial may be effective or that the disease is not associated with a bacterial infection and therefore antimicrobial treatment could be discontinued. Unfortunately, it is difficult to obtain a sample from some parts of the body, such as the lung, and some organisms may be more difficult to culture as they require special conditions for growth, or grow very slowly. Despite these limitations, bacterial culture and antimicrobial susceptibility testing would be performed wherever possible and used as an additional tool to support diagnosis and treatment.
Don says, Thank you Sue. I appreciate the time you have taken today to discuss some of the issues about antimicrobial use in small animals, the role they play in animal health and the public health issue of antimicrobial resistance.
Sue says, Thank you Don. I appreciate you interest and hope that the information is useful to your readers. I look forward to your report.