Overview
When harmful bacteria get into places they shouldn’t and start to multiply, it can lead to your dog getting a bacterial infection. Unlike viruses, which the body usually has to fight off on its own, bacterial infections can often be treated with medication, especially if caught early.
Bacterial infections in dogs can range from mild skin issues to more serious illnesses.
What causes bacterial infections in dogs?
Bacterial infections are most common when your dog’s immune system is weakened. Stress, illness, poor diet, or other health conditions like diabetes or Cushing’s can make it harder to keep bacteria in check. Even bacteria that normally live on the skin can cause trouble.
Bacteria can come from other animals, or from the environment — through dirty water, food, soil, or from shared items like bowls and toys. Warm, damp, dark areas also give bacteria a chance to thrive. And, as you might expect, breaks in the skin — from bites, scratches, or constant licking — make infections more likely.
Which dogs are most at risk of bacterial infections?
Dogs who spend a lot of time in kennels or shelters are more at risk, as close contact and cramped spaces can make hygiene tricky. The risk varies with breed as well — skin folds and floppy ears can give bacteria the warm, damp and dark conditions they prefer, so breeds with these features tend to get skin and ear infections more. Dogs who scratch a lot, like those with allergies or parasites, have a higher chance of irritating their skin and making infection more likely. Lastly, puppies and older dogs are often more at risk due to their weaker immune systems.
Common bacterial infections in dogs
One bacterial infection isn’t necessarily as common as another. Here are the ones you're most likely to come across:
Skin infections: These are some of the most common bacterial problems in dogs. They often begin when scratching or licking — triggered by allergies, parasites or injuries — breaks the skin. Warm, damp and dark areas like skin folds are especially at risk.
Ear infections: These often affect dogs with floppy ears or lots of hair in the ear canal, and those with allergies. Ear infections are painful, leading to scratching, redness, and a noticeable smell.
Urinary tract infections (UTIs): These are more common in female dogs and can make urination frequent or painful. If left untreated, they can sometimes lead to more serious problems like kidney infections.
Kennel cough: This is a nasty respiratory infection that spreads super quickly through the air. As the name suggests, kennel cough is especially common in dogs that spend time in kennels, shelters, or daycare.
How to prevent bacterial infection in dogs?
Many bacterial infections can be avoided by being consistent with a few good habits:
Routine vet visits: regular check-ups help catch issues early. Keeping vaccinations up-to-date also protects against leptospirosis and kennel cough — that’s two fewer bacterial infections to worry about.
Good hygiene: wash bedding, bowls, and toys often. Regular grooming and bathing also help keep skin healthy and bacteria at bay.
Parasite protection: fleas and ticks can spread bacteria, including those that cause Lyme disease. Year-round treatment is important, especially for dogs who spend lots of time outdoors.
A balanced diet: a healthy and balanced diet supports your dog’s immune system via the microbiome. Avoid raw food, as it may carry bacteria like salmonella.
Clean water: make sure your dog always has access to fresh water. Don’t let them drink from puddles — these can carry harmful bacteria.
Skin checks: scratching or licking can break the skin and lead to infection. Tackling the cause — like fleas, allergies, or food sensitivities — helps protect their skin.
Keep ears and skin folds dry: dry these areas well whenever your dog gets wet, whether from bathing, swimming, or from walking on a rainy day. Your vet can recommend suitable products if needed. This is all the more important if your dog has floppy ears or deep skin folds.
Spot early signs: changes in appetite, behaviour, or toilet habits can be early warnings. Quick action helps prevent small problems becoming serious.
Pet Health Club plans help you stay on top of preventive care — covering check-ups, vaccinations, and parasite treatments in a simple monthly cost.
Bacterial skin infections in dogs
Skin infections are a common reason for vet visits. Red, itchy, flaky, or smelly skin may be a sign of a bacterial infection. These often appear in damp areas or where licking and scratching have damaged the skin. Some cases are mild, while others can become more serious.
When the skin is damaged, bacteria that normally live on the surface can cause problems. With the right treatment, these infections usually clear up fine.
Pyoderma
This is a term for skin infections in dogs — the name ‘pyoderma’ literally means ‘pus in the skin’. Most bacterial skin infections fall into this category, and it can affect different skin layers:
Surface pyoderma affects the outermost skin layer and includes hot spots and skin fold infections.
Superficial pyoderma involves hair follicles and upper skin layers, often causing redness, scabs and hair loss.
Deep pyoderma reaches lower layers, leading to swelling, discharge or sore, draining areas. Affected dogs may also seem tired or uncomfortable.
Pyoderma often develops as a secondary condition to issues like flea allergies, food sensitivities, hormone imbalances, or immune system issues. Vets may use skin swabs or allergy tests to diagnose it, and treatment usually includes prescribed medicines or topical creams. Pyoderma can also follow from paronychia, a type of nail bed infection. This can happen if your dog has unhealthy nails and doesn't get treatment.
Staphylococcal infections in dogs
Staph infections often lead to red, itchy, or scabby skin. They can get worse if your dog licks or scratches the area, which many dogs will absolutely try to do. These infections can keep coming back if the root cause isn’t treated, and are more common in dogs with sensitive skin.
Skin fold dermatitis
Also known as intertrigo — skin fold dermatitis can appear where skin rubs together, like the face, neck, armpits, or tail. They’re common in brachycephalic breeds like Bulldogs, Pugs, and Shar Peis. The moisture and friction of the moving folds create ideal conditions for bacteria to grow. Signs include redness, discharge, and a bad smell. Treatment usually involves keeping the affected areas clean and dry using medicated wipes or creams from your vet.
Yeast dermatitis in dogs
Yeast infections aren’t caused by bacteria, but they often show up alongside bacterial infections and share many of the same signs. They’re caused by a fungus called Malassezia pachydermatis, and common signs include thickened, flaky skin and a strong, musty smell.
Bacterial ear infections in dogs
Already a very common type of bacterial infection in dogs, ear infections are even more likely to affect breeds with floppy ears or lots of ear hair, like Cocker Spaniels and Poodles (your vet may advise regular ear cleaning to help lower your dog's chance of an ear infection if they are one of these breeds). They are also strongly associated with allergic skin disease in dogs. Signs include head shaking, scratching, redness, swelling, and strong-smelling discharge from the ear canals. Moisture, wax, and hair can all create the warm, damp conditions bacteria — and sometimes yeast — thrive in.
Bacterial ear infections can be painful and may lead to deeper problems if left untreated. Most cases are treated with medicated drops for cleaning your dog’s ears, but — if their ear is badly swollen — sedation may be needed for a full clean.
Otitis
Otitis is the term for inflammation of the ear — and it’s one of the most common ear issues in dogs. Otitis externa affects the outer ear canal and often causes redness, discharge, itchiness, and a strong smell. Treatment usually involves medicated or anti-inflammatory ear drops to clear the infection and ease discomfort.
Some dogs get recurring ear infections (known as chronic or recurrent otitis), often due to allergies, skin conditions, or ear shape. These cases may need longer treatment and ongoing care. In more severe cases, repeated inflammation can narrow the ear canal, and surgery may be needed. If left untreated, an outer ear infection can spread deeper into the middle or inner ear (otitis media or interna). Head tilting, balance problems, and unusual eye movements are all symptoms of these more advanced infections.
Bacterial eye infections in dogs
Eye infections in dogs can be uncomfortable and may lead to more serious problems if untreated. Signs include redness, discharge, squinting, frequent blinking, or goopy discharge of a yellowish or greenish colour.
Bacterial conjunctivitis in dogs
Conjunctivitis is the most common bacterial eye infection in dogs, causing inflammation of the pink tissue around the eye (known as the conjunctiva). Signs of bacterial conjunctivitis include redness, swelling, squinting, and sticky discharge. Treatment usually involves medicated drops or ointments, and sometimes tablets if the infection is more advanced, and most dogs make a full recovery if treatment begins quickly. On the other hand, if bacterial conjunctivitis is left untreated, it can spread deeper or cause lasting damage. It’s always wise to speak to your vet if your dog seems in pain or struggling with seeing.
Bacterial gut infections in dogs
Bacterial gut infections in dogs can range from mild tummy upsets to more serious issues needing vet care. Signs include diarrhoea, vomiting, low appetite, and sometimes fever or tiredness. Dogs usually pick these infections up from contaminated food, water, or faeces.
Salmonella infections in dogs
Rare but often serious, salmonella infections in dogs may cause diarrhoea, fever, and in severe cases blood poisoning (septicaemia or sepsis). Infections are often linked to raw food, and some strains can spread to humans — meaning it’s one to keep an eye on, for both your sakes.
Gastrointestinal campylobacteriosis
Campylobacter infections can cause diarrhoea, vomiting and fever, especially in puppies and younger dogs. They’re spread by Campylobacter bacteria and can pass to people, so be careful to practice good hygiene when handling affected dogs.
Clostridial enterotoxicosis
Clostridial infections, caused by Clostridium perfringens, can lead to bouts of profuse diarrhoea — sometimes with mucus, blood, or straining. They may be short-term or ongoing, and are often triggered by stress or sudden diet changes. Treatment usually involves medication and a high-fibre or prebiotic diet.
Helicobacter infections
When Helicobacter bacteria come to live in the stomach they can cause long-term vomiting or inflammation. Diagnosis often involves tests like a biopsy (a tiny tissue sample) or an endoscopy (a small camera used to look inside the body). Treatment usually includes medication to help reduce stomach acid and ease discomfort.
Colibacillosis
Some strains of E. coli can cause this type of infection in the gut or urinary tract, especially in puppies. Good hygiene and avoiding contaminated food or water are the best ways to help prevent it.
Tyzzer disease
This rare condition is caused by the bacteria called Clostridium piliforme. Tyzzer disease can lead to diarrhoea, jaundice, and tiredness. As with many bacterial infections, it mostly affects puppies or dogs with weakened immune systems.
Urinary tract and reproductive infections in dogs
Urinary and reproductive infections are fairly common in dogs, particularly in older females. Some are mild and easy to treat, while others can be more serious — or even life-threatening. Spotting the signs early and getting vet care quickly can make a big difference.
Urinary tract infections (UTIs)
UTIs are usually caused by bacteria — often E. coli — entering through the urethra and reaching the bladder. Female dogs are more at risk due to their shorter urethras. If you notice your dog needing to pee more often, straining to urinate, having accidents indoors, licking more than usual at their genitals, or having very strong-smelling pee, it might be a sign of a UTI. Blood in the urine can be a serious symptom — if you spot this, see a vet right away. Testing a urine sample from your dog is usually how UTIs are diagnosed, and medication is the typical treatment. If left untreated, UTIs can lead to more serious problems, including kidney infections.
Pyelonephritis
In most cases caused by bacteria moving up from the bladder, pyelonephritis is a type of kidney infection. Signs can include fever, vomiting, tiredness, or pain when touched around the back or sides. It’s diagnosed with urine tests, bloodwork, and sometimes scans. Treatment typically involves medication, with some follow-up checks afterwards to make sure it’s cleared.
Cystitis
This is a type of inflammation of your dog's bladder, and it can have several causes — including infection, bladder stones, and tumours. Common signs include blood in the urine, straining, and repeatedly needing to wee for small amounts. Diagnosis may involve urine tests or scans, and treatment depends on the cause but can include medication, pain relief, or changes to your dog’s diet.
Pyometra
Pyometra is a serious and life-threatening infection of the uterus in unspayed female dogs. It usually develops a few weeks after your dog's heat cycle, when hormonal changes allow bacteria to grow inside the uterus. Signs can include tiredness, vomiting, drinking more than usual, urinating more than usual, and either vaginal discharge or a swollen belly. Emergency surgery to remove the uterus is often needed, along with medication and fluids.
Mastitis
This infection of the mammary glands is usually seen in nursing dogs. Mastitis can happen when bacteria enter through the teat or when milk builds up. Signs include swelling, warmth, redness, pain, and sometimes discoloured milk. Most infections respond well to vet-prescribed medication and supportive care, though some may need hospital treatment if the infection spreads.
Systemic bacterial infections in dogs
Systemic bacterial infections spread through the bloodstream and can affect multiple organs, including the heart, kidneys, joints, spine or nervous system. They’re more serious than local infections and often need urgent treatment.
These infections often start in the skin, gut, or urinary tract. From there they will spread if untreated. Some are passed on by ticks or fleas, and some can affect humans.
Leptospirosis
Leptospirosis is a serious disease that can spread through contaminated water or the urine of infected animals. The infection targets the liver and kidneys, and can sometimes cause bleeding or affect the lungs. This is one which can be passed to humans too. Your dog’s routine vaccinations — included in Pet Health Club — offer protection from leptospirosis. It’s the easiest way to keep them safe from this dangerous disease.
Lyme disease (borreliosis)
This bacterial illness is passed to dogs by ticks and can cause joint swelling, fever, tiredness, and — if left untreated — serious kidney problems. Some dogs might seem stiff or generally off, while others show no signs at all. Vets can diagnose Lyme disease with a blood test, and medication is usually very effective. Your best defense? Check your dog for ticks after walks and use a regular tick-control product.
Endocarditis
Often linked to dental disease transferring bacteria into the bloodstream, endocarditis is a serious infection of the heart valves. It can lead to heart murmurs, tiredness, and — in serious cases — heart failure. If your dog has endocarditis, they need veterinary attention as quickly as possible.
Discospondylitis
An infection in the bones and discs of the spine, discospondylitis is usually spread through the bloodstream. It can cause back pain, stiffness, and in very bad cases, nerve-related signs like weakness or wobbliness. It’s more common in large or older dogs.
Tularemia
A rare but serious bacterial infection, this is usually spread by ticks or contact with infected wildlife. Signs of tularemia can include fever, swollen lymph nodes, and general weakness. It can also spread to humans, and it can be very serious when it does.
Septicemia, bacteremia, and septic arthritis
These infections happen when bacteria enter the bloodstream, letting it spread throughout the body. Septicemia and bacteremia can lead to life-threatening illness and often develops as a complication of another infection. Treatment for both of these infections usually involves IV antibiotics and fluids.
One complication of septicemia is known as septic arthritis, where the infection spreads to one or more joints. This can cause limping, swelling and pain, and sometimes develops as a complication of septicemia. Septic arthritis sometimes needs surgery to help clear bacteria from the joints.
Want more information on bacterial infections in dogs?
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Medically reviewed by Lizzie Youens, BSc(Hons) BVSc MRCVS
Published on 28/08/2018 • Reviewed on 01/05/2025