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Bacteria & Yeast Infections in DogsUpdated 10 months ago

Low numbers of bacteria and yeast usually live harmlessly on the surface of healthy dog ear skin; so, it’s common and quite normal to find small (occasional) numbers under the microscope. Overpopulation causes clinical signs and requires treatment.

What Are Common Microbes Found In Dog Ears?

What Are Signs Of Ear Infections In Dogs?

How Do I Check For An Ear Infection?

When And How Are Ear Infections In Dogs Treated?

How Do I Know If The Infection Is Gone After Treatment?

How Does My Dog Get An Ear Infection?

What Are Common Microbes Found In Dog Ears?

Bacteria and yeast (Malassezia) are single-celled microbes, invisible to the naked eye. There are two main forms (shapes) of bacteria commonly detected from an ear swab cytology: cocci (sphere-shaped) and bacilli (rod-shaped). Yeast are dark spheres (larger than bacteria) often with an extra smaller sphere, so they take on the shape of small footprints. Low numbers of bacteria and yeast usually live harmlessly (symbiosis) on the surface of healthy ear skin; so, it’s common and quite normal to find small (occasional) numbers under the microscope. This is especially true for yeast and cocci, while less so for bacilli. If no bacteria or yeast are detected (none seen), that’s normal too. Even though we share some types of ear and skin bacteria and yeast between pets and people, they aren’t contagious. This is because there’s almost always an underlying reason(s) the bacteria or yeast overpopulate (1+, 2+, 3+, 4+) to cause clinical signs.

What Are Signs Of Ear Infections In Dogs?

Clinical signs of bacterial and/or yeast ear infection (one or more):

  • repeated scratching ears, head, or neck
  • frequent head shaking
  • rubbing head and ears on floor
  • doesn’t like ear(s) touched
  • skin irritation in or around ears
  • hearing loss
  • black or brown ear discharge
  • yellow ear discharge
  • ear redness
  • ear sores
  • scabs on ear flap
  • strong ear odor

How Do I Check For An Ear Infection?

Veterinarians suspicious of an ear infection will swab the ear crevices and flaps of both ears for cytology. At MySimplePetLab, ear swab samples from our from home Ear Infection Dog Test are thinly smeared (“rolled” or “dotted”) onto a glass microscope slide, colorized with special stains, and examined with 1000x (oil-immersion) magnification. This is the gold-standard way to search for bacteria and yeast on the surface of the ear. The distinction between yeast, cocci, and bacilli is important for treatment selection. Yeast are fungi, so need to be treated with anti-fungal medication. While both cocci and bacilli are forms of bacteria, each type is generally susceptible to different classes of antibiotics. The MySimplePetLab ear cytology results will also indicate if the cocci or bacilli bacteria found are extracellular (outside cells) or intracellular (inside cells). Finding the bacteria free-living on the skin surface is most common. If bacteria are being gobbled up by immune cells (intracellular bacteria), it’s a sign that the infection is even more serious.

When And How Are Ear Infections In Dogs Treated?

If the bacterial and/or yeast counts are high (1+, 2+, 3+, 4+) in your dog’s ear swab samples, and especially if with one or more clinical signs, then a physical exam of your dog’s ears is needed by a veterinarian. Treatment of microbe infections in the ear typically involves prescription anti-fungals for yeast and prescription antibiotics for bacteria. Either can come as ointments topically applied to the surface of the ear or given by mouth, and/or antiseptic wipes and ear flushes that inhibit yeast or bacterial growth.

How Do I Know If The Infection Is Gone After Treatment?

Retesting with an ear cytology after treatment and a recheck ear exam, even if symptoms have improved, is commonly done by veterinarians to ensure that the yeast and bacteria numbers have returned to normal (none seen or occasional). Especially when ear treatments aren’t working, it’s important to take the next step with your veterinarian. They may recommend a culture of the discharge to determine exactly which bacteria is the problem and which antibiotic(s) are able to kill it. It’s also important to look for underlying (primary, secondary, perpetuating, or predisposing) causes that allow the yeast and bacteria to overgrow. Solving or supporting the underlying problem may be necessarily to fully resolve or best manage the ear infection.

How Does My Dog Get An Ear Infection?

We have listed below some primary and secondary causes of ear infections in dogs. Some dogs may also have existing medical issues that may make them more predisposed to getting ear infections. 

Primary causes:

  • allergy (environmental, food, contact)
  • parasites (ear or skin mites)
  • endocrine disease (hypothyroid, Cushing’s)
  • skin barrier or gland disorders
  • foreign material in ear

Secondary causes:

  • other bacterial infection
  • yeast (Malassezia) infection
  • medication reaction
  • over cleaning

Perpetuating factors:

  • disruption of skin migration to clean ears
  • swollen ear canals
  • ruptured eardrum (tympanum)
  • middle ear infection (behind eardrum)

Predisposing factors:

  • excessively hairy ear canals
  • floppy ears
  • narrow ear canals
  • excessive moisture (swimming, bathing)
  • ear polyps, adenomas, or cancer
  • trauma / injury
  • immune suppression

 

Additional Questions? Chat us at MySimplePetLab.com, email [email protected], or call us at 833-PET-TEST (833-738-8378).

 


Sources

Otitis Externa in Animals - Ear Disorders - Merck Veterinary Manual (merckvetmanual.com

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