Bacterial infections are common in dogs and can involve many areas of the body, including the skin, ears, mouth, urinary tract, respiratory system, and internal organs. Some infections are mild and easy to treat, but others can become life-threatening if they are not diagnosed and managed promptly.
The appropriate treatment depends on the location of the infection, the likely bacteria involved, the severity of symptoms, and whether there is an underlying condition that makes the infection more likely to recur. Antibiotics can be very helpful when needed, but they should only be used under veterinary guidance. The AVMA emphasizes the importance of the judicious use of antimicrobial drugs to protect animal health and help prevent antimicrobial resistance.
What Causes Dog Bacterial Infections?
Dogs are exposed to bacteria every day through their skin, mouth, environment, food, water, and contact with other animals. Not all bacteria are bad. In fact, many bacteria normally live on the skin, in the mouth, and in the digestive tract without causing a problem.
An infection can occur due to bacterial overgrowth, access to damaged tissue, or spread into an area where bacteria do not belong. Possible causes include:
- Skin allergies or itchiness
- Bites, scratches, or wounds
- Moisture in the ears or folds of the skin
- Tartar and dental plaque
- Abnormalities of the urinary tract
- Decreased immune response
- Contact with infected water, urine, or soil
- Other predisposing conditions for infection
Bacterial infections can look like other health problems, so a veterinarian may need to perform tests before choosing the right treatment.
Common Dog Bacterial Infection Signs
Symptoms depend on the area of the body involved. However, common symptoms of bacterial infection in dogs may include:
- Redness, swelling, or warmth
- Discharge, bad smell, or pus
- Itching, licking, chewing, or scratching
- Sneezing, coughing, or nasal discharge
- Tenderness or pain when touched
- Accidents in the house or frequent urination
- Bad breath, drooling, or difficulty eating
- Fever, tiredness, or loss of appetite
- Nausea, vomiting, or diarrhea
- A wound that does not heal
If your dog looks painful, seems very tired, stops eating, has trouble breathing, has a fever, or has symptoms that are getting worse quickly, call your veterinarian right away.
1. Skin Infections in Dogs Caused by Bacteria
One of the most common bacterial problems dogs have is bacterial skin infection. These infections are often referred to as pyoderma. They may appear as red bumps, pustules, scabs, hair loss, flaky skin, odor, or itchy areas.
Another underlying problem often causes the skin’s barrier to break down. Allergies, fleas, hormonal disease, over-licking, skin folds, moisture, or wounds can all make it easier for bacteria to multiply. Treatment for pyoderma can include topical therapy, systemic antimicrobial therapy, and management of underlying triggers, according to the MSD Veterinary Manual.
Treatments for Bacterial Skin Infections
Treatment may include medicated shampoos, topical antiseptic products, ointments, or oral antibiotics if the infection is deeper or more widespread. Topical therapy alone may be adequate to treat superficial pyoderma in some cases. According to the MSD Veterinary Manual, uncomplicated surface or superficial pyoderma may sometimes be managed with topical antimicrobial treatment, such as chlorhexidine-based products.
If the infection recurs, the veterinarian will usually look for the underlying cause. Your dog may be prone to recurrent skin infections due to allergies, parasites, endocrine disease, immune problems, or incomplete treatment.
2. Ear Infections in Dogs Caused by Bacteria
Dogs are also prone to ear infections, especially dogs with allergies, floppy ears, narrow ear canals, frequent swimming, or excess ear wax. Bacteria can flourish in the ear canal if the conditions there are warm, moist, inflamed, or irritated.
Symptoms of a bacterial ear infection can include:
- Head shaking
- Scratching the ears
- Redness of the ear
- Bad smell
- Brown, yellow, or pus-like discharge
- Pain when the ear is touched
- Swelling of the ear canal
Severe bacterial ear infections may require a combination of antibiotics and anti-inflammatory medications to reduce symptoms such as discharge, pain, swelling, and secretions, according to the Merck Veterinary Manual.
How Do You Treat Bacterial Ear Infections?
Treatment usually includes cleaning the ear, ear drops, anti-inflammatory medication, and sometimes oral medication if the infection is severe or has spread deeper. The veterinarian may look at the ear discharge under a microscope to check for bacteria, yeast, mites, or inflammation.
Never use leftover ear drops for recurrent ear infections. Chronic ear problems can involve allergies, resistant bacteria, changes to the ear canal, foreign bodies, or middle ear disease.
3. Urinary Tract Infection in Dogs
A urinary tract infection, or UTI, is an infection caused by bacteria anywhere in the urinary system, but most commonly in the bladder. Any dog can get a UTI, but females are more prone to urinary tract infections than males.
Symptoms of a urinary tract infection may include:
- Frequent urination
- Difficulty urinating
- Accidents in the house
- Blood in the urine
- Strong-smelling urine
- Licking around the urinary opening
- Painful urination
Bacterial cystitis is usually diagnosed with a urine sample. Urinalysis and bacterial culture are common tools veterinarians use to diagnose bacterial bladder infections, according to the Merck Veterinary Manual.
Treatment of Urinary Tract Infection
Treatment usually involves antibiotics selected by the veterinarian. Sometimes, a urine culture and sensitivity test may be recommended to identify the bacteria and determine which antibiotic is likely to work.
If UTIs are recurrent, the veterinarian may look for underlying problems such as bladder stones, diabetes, kidney disease, anatomical abnormalities, or incomplete resolution of a previous infection.
4. Bacterial Respiratory Infections in Dogs
Dogs can develop infections of the respiratory system involving the nose, throat, trachea, bronchi, or lungs. Certain respiratory diseases are caused by viruses, some by bacteria, and some by more than one infectious agent.
One example is canine infectious respiratory disease complex, or kennel cough. According to the AVMA, antibiotics are generally not needed or recommended for kennel cough, except when there are signs of bacterial pneumonia or prolonged illness.
Respiratory infection symptoms may include:
- Coughing or sneezing
- Nasal discharge
- Eye discharge
- Fever
- Exhaustion
- Loss of appetite
- Rapid breathing or difficulty breathing
Treatment of Respiratory Tract Infections
Mild upper respiratory infections may clear up with rest, isolation from other dogs, hydration, and supportive care. If a bacterial infection or pneumonia is suspected, the veterinarian may prescribe antibiotics and may recommend chest X-rays, bloodwork, or other diagnostics.
Difficulty breathing, blue or pale gums, collapse, high fever, or a wet cough with weakness all require urgent treatment.
5. Infections of Teeth and Tooth Roots
Bacteria naturally collect in the mouth as plaque. Over time, plaque and tartar can cause gum disease, tooth decay, tooth root abscesses, and oral pain. Dental infections can be especially easy to miss because many dogs continue to eat even if their mouth hurts.
Signs of a dental infection can include:
- Bad breath
- Bleeding or red gums
- Drooling
- Dropping food
- Chewing on one side
- Swelling of the face
- Pawing at the mouth
- Loose or broken teeth
According to Cornell’s canine health information, treatment of existing dental disease includes a thorough oral exam, dental X-rays as needed, and cleaning above and below the gum line under anesthesia.
Management of Dental Infections
Treatment may include professional dental cleaning, dental X-rays, extraction of diseased teeth, pain control, and antibiotics as needed. However, antibiotics alone usually do not cure dental disease. VCA says antibiotics can be used for a tooth root abscess, but they will not fix the underlying tooth injury by themselves.
That is why dental infections typically need definitive dental treatment, not just medication.
6. Wound Infections and Abscesses
Cuts, punctures, bite wounds, and scratches can become infected when bacteria enter the skin or deeper tissues. Bites are particularly serious because bacteria can be driven under the skin, even though the surface wound may look small.
Signs of an infected wound or abscess might include:
- Inflammation
- Redness or heat
- Pain
- Pus or discharge
- Bad smell
- Fever
- Lethargy
- A wound that is growing or not healing
Treatment of Wound Infection
Treatment is based on the depth and severity of the wound. The veterinarian may clean and flush the area, drain an abscess, remove damaged tissue, prescribe antibiotics, provide pain relief, or apply a bandage or drain.
If the wound is deep, caused by a bite, close to the eye, or has swelling or pus, have a veterinarian check it as soon as possible.
7. Leptospirosis
Leptospirosis is a serious bacterial disease caused by bacteria called Leptospira. Dogs can be exposed through contact with contaminated water, soil, wildlife urine, or infected animals. It can be dangerous to people and can attack the kidneys, liver, and other organs.
Signs may include:
- Fever
- Vomiting
- Diarrhea
- Loss of appetite
- Lethargy
- Increased thirst or urination
- Yellow skin or gums, also known as jaundice
- Muscle aches
- Kidney or liver issues
Cornell’s Canine Health Center states that leptospirosis is treated with antibiotics, most commonly doxycycline, for at least two weeks, and that hospitalization with IV fluids and electrolyte management is often needed initially.
How Leptospirosis Is Treated
Treatment usually includes antibiotics and supportive care. Severely affected dogs may need hospitalization, IV fluids, anti-nausea medication, nutritional support, blood pressure management, and monitoring of kidney and liver function.
Because leptospirosis can be zoonotic, meaning it can spread from animals to people, owners should follow their veterinarian’s instructions carefully for cleaning, handling urine, and reducing exposure risk.
How Veterinarians Diagnose Bacterial Infections in Dogs
Diagnosis depends on the suspected location of the infection. A veterinarian may recommend:
- Physical exam
- Skin impression, scraping, or cytology
- Ear cytology
- Urinalysis
- Bacterial culture and sensitivity testing
- Bloodwork
- X-rays or ultrasound
- Dental X-rays
- Wound sampling
- Testing for specific diseases, such as leptospirosis
Culture and sensitivity testing can be especially important for recurring infections, deep infections, severe infections, or infections that do not respond to initial treatment. This helps the veterinarian choose an antibiotic that is more likely to work.
How Are Bacterial Infections in Dogs Treated?
Treatment varies depending on the type and severity of infection. A dog’s treatment plan may include:
- Topical antiseptic products
- Medicated shampoos
- Ear drops or ointments
- Oral antibiotics
- Injectable antibiotics in some cases
- Pain relief
- Anti-inflammatory medication
- Wound cleaning or drainage
- Dental treatment
- IV fluids or hospitalization for serious infections
- Treatment of underlying conditions
Antibiotics should be given exactly as prescribed. Owners should not stop treatment early, skip doses, share antibiotics between pets, or use leftover medication from a previous illness.
Why You Should Not Use Leftover Antibiotics
Using leftover antibiotics can be risky. The medication may be wrong for the type of infection, the dose may be incorrect, the duration may be too short, or the infection may not be bacterial at all. In some cases, the wrong medication can delay proper treatment or contribute to resistant bacteria.
Antimicrobial resistance is a major concern in both human and veterinary medicine. The AVMA’s guidance on antimicrobial use emphasizes responsible use of these drugs to preserve their effectiveness.
When to Call a Veterinarian
Contact your veterinarian if your dog has signs of infection that do not improve quickly, keep returning, or appear with pain, fever, swelling, discharge, or lethargy.
Seek urgent veterinary care if your dog has:
- Trouble breathing
- Collapse or severe weakness
- Pale, blue, or yellow gums
- Rapidly spreading swelling
- A deep bite wound
- A painful eye or sudden vision change
- Repeated vomiting or diarrhea
- Inability to urinate
- High fever or severe lethargy
Early treatment can help prevent a mild infection from becoming more serious.
Treating Bacterial Infections in Dogs
Bacterial infections in dogs can affect the skin, ears, urinary tract, respiratory system, mouth, wounds, and internal organs. Many infections can be treated successfully, but the right approach depends on an accurate diagnosis and a treatment plan from a veterinarian.
Antibiotics are important tools, but they are not always needed for every infection-like symptom. Some conditions require topical treatment, cleaning, dental care, wound management, supportive care, or treatment of an underlying disease.
If your dog has signs of a bacterial infection, the safest step is to contact your veterinarian. With proper diagnosis, targeted treatment, and follow-up care, many dogs recover well and return to normal activity.
Disclaimer: This information is for general informational purposes only and is not intended as veterinary or medical advice. It should not be used as a substitute for professional care. Please consult a licensed veterinarian for diagnosis, treatment, and guidance regarding your animal’s health.