November 20, 2023

Julia E. Miller, DVM, DACVD,
Sponsored by Pet King Brands

Mild, run of the mill ear infections are bread and butter in general practice, but what do we do when we are presented with exudative ears full of pus? Here are a few tips and tricks to help manage these difficult cases.

Cytology everything!
This is a dermatology mantra for a reason. More than once in my career I have been fooled by a “yeasty smelling” ear that was actually Pseudomonas otitis externa (OE) on cytology. I have learned to distrust my eyes and nose when it comes to skin and ears and always trust my cytology. Particularly in these exudative ears, cytology not only helps us select our treatments but informs what we do at our recheck examination. For example, if a patient presents with 3+ rods and 3+ degenerate neutrophils on initial cytology and on recheck two weeks later is 1+ rods and trace degenerate neutrophils you have made great progress and should continue the same treatment plan for longer.

Don’t miss a mass
It is critical to perform otoscopic examinations, particularly if the infection is unilateral. Masses or foreign bodies in the ear canal are often responsible for chronic OE in both dogs and (especially) cats. If a patient is extremely painful or aggressive on initial examination it is reasonable to initiate treatment and see what progress you make, but on recheck an otoscopic exam is a must if the infection has not resolved. If this requires sedation or a more thorough ear cleaning go for it!

To clean or not to clean…
Another mantra I live life by is “dilution is the solution to pollution.” In these highly exudative ears vigorous lavage is often required to speed along resolution. In-house, thorough ear cleanings should be a staple in your management protocol and are an excellent way to utilize the expertise of your technicians and assistants. Long-term we may need to rely on owners to continue the cleaning plan, and proper education on how to appropriately clean the ear is required for every client. Do NOT send a cleaner home without an in-person demonstration. If things aren’t resolving, chat with your local dermatologist about generally anesthetized video otoscopy, it’s amazing!

The biofilm blues
Increasingly, biofilms are being blamed for why our treatment protocols fail in some of these highly exudative ears. Biofilms are bacterial communities encased in an extracellular polymeric substance that effectively shields the bacteria from the host’s immune system and our topical antimicrobials. Several active ingredients have shown to be effective in degrading biofilms and these include the enzymes mutanase and dextranase (in ZYMOX^®  Plus, PKB), EDTA (in TrizEDTA^®, TrizULTRA+ Keto^®, Mal-A-Ket^® Plus, Dechra, and T8 keto^®, Elanco), and N-acetylcysteine (in Tris-NAC, Nextmune). Incorporating one of these products into your treatment plan may be the step you need to achieve success. With most cleaners, it is recommended to use them 15-30 minutes before treatment and the ZYMOX^®  Plus product is an all-in-one cleaner and treatment that is instilled once daily.

What treatment is the best?
As with almost all things in dermatology, there is no one size fits all treatment plan for these severe ears and treatment is a trial-and-error process. I have had successes and failures with just about every product on the market, including in-house compounded products, so it may be less about what you put in the ear and more about how you are managing the exudate and if your owners are treating the ear effectively. I find it very helpful to keep things as simple as possible (i.e. once daily medications) and make certain my owners are thoroughly educated on the treatment challenge that lies ahead.  

To culture or not to culture…THAT is the question
This is a debated topic amongst dermatologists with no strict consensus. What we do know is that susceptibilities are based on serum/plasma concentrations of antibiotics and topically we can achieve up to 10,000 times that concentration. I only use cultures to choose an oral antibiotic and the vast majority of these cases have high levels of antibiotic resistance therefore it is actually quite rare that I reach for a culture.

If at first you don’t succeed…
…either you missed something, you need to change treatment plans, or you need to give it more time. Severe otitis may take months to fully resolve so if you are making progress keep going! Remember that once you’ve resolved the otitis (well done you!) the job is not done. Most of these cases require long-term preventative plans and thorough allergy workups.

Don’t fear these highly exudative ears. Set your client’s expectations appropriately, use your microscope and otoscope routinely, clean the ear effectively, consider biofilm management, and utilize your technicians and assistants and you will be well on the path to success!

Dr. Julia E. Miller is an upstate NY native and a Cornell University College of Veterinary Medicine graduate. She completed a large animal rotating internship at the University of Georgia and then worked as a mixed small and large animal general practitioner for several years before returning to Cornell to complete her dermatology residency. After completing her residency, Dr. Miller stayed on at Cornell as an assistant clinical professor in the section of Dermatology where she was awarded the Zoetis Distinguished Teacher Award. She is now enjoying private practice life surrounded by horses and bourbon in beautiful Louisville KY. Dr. Miller has a special interest in the management of chronic otitis externa, and all things related to large animal skin disease (especially horses).

Outside of work, Dr. Miller enjoys her lovable bully dogs, riding horses, and singing whenever possible. She also loves providing continuing education to veterinarians and owners because derm is absolutely the best!