Skin Culture and Sensitivity: When a Skin Infection Needs a Culture

A skin culture grows the germs from a skin scraping or swab in the lab, so a vet can see which bacteria are present and which medicines hold them back. It is mostly used when a dog's or cat's skin infection keeps returning or does not improve. A quick cytology smear is often done first, and a registered veterinarian reads both results.

When does a skin infection need a culture?

A culture becomes useful when the picture is less clear. Your vet may ask for one when:

• the infection comes back soon after it seems to settle
• earlier treatment did not work as expected
• there are many pustules, sores or crusts
• the smear shows a type of germ the vet wants to identify

It helps to know what a culture cannot do. It names the germ, but it does not explain why the skin became infected. Infections often return because something underneath keeps the skin weak, such as an allergy, mites or a hormone problem. Your vet may need other tests to find that cause.

Why is a cytology smear usually done first?

A Skin Impression Smear Cytology is a fast way to look at what is on the skin. A glass slide is pressed on a moist or crusted area, or a swab is rolled across it. The slide is stained and read under the microscope. The pathologist can see round or rod-shaped bacteria, yeast, and the inflammatory cells the body sends to the area.

Cytology gives a first answer quickly, but it has limits. It cannot always name the exact germ, and it cannot show which medicine will work. That is the job of the culture. The smear often helps the vet decide whether a culture is worth doing.

How is the sample taken and grown?

For a Skin Scraping Bacterial Culture & Sensitivity, the vet collects material from the affected skin, often from the edge of a sore, from under a crust or from a pustule that has not yet burst. Clean tools are used so that stray germs from the room do not enter the sample. The lab tells you how to keep the sample until it arrives.

In the lab, the sample is spread on a growth plate and kept warm. Any bacteria in it multiply until they form visible spots called colonies. The lab then identifies the germ. For the sensitivity part, the germ is tested against a set of antibiotics in the dish, and the lab notes which ones stop its growth. Your vet uses that report to choose treatment.

Why take the sample before antibiotics?

Antibiotic tablets, creams or medicated washes already on the skin can reduce what grows in the dish. The culture may then look clean or show only a few survivors, and that can mislead the vet.

If your pet has already had medicine, tell your vet exactly what was used. Please do not scrub or apply new products to the area just before the sample is taken. Ask your vet before you change any medicine on your own.

How do mange mites and ear swabs fit in?

Mites can cause the itch that leads to scratching, and scratching breaks the skin and lets bacteria in. A Skin Scraping (Mange Mite Examination) checks for mites under the microscope, and is often asked for beside a culture when a pet is very itchy.

Ears are another place where infection returns. When the ears are red, smelly or full of discharge, an Ear Swab Culture & Sensitivity follows the same steps as a skin culture: the swab is grown, the germ is named and its response to medicines is checked.

The Dermatitis Safety Panel typically groups a blood count, a fungus examination, a fungal culture and an allergy antibody test for itchy, inflamed skin. The exact list is confirmed when you book.

How is the result read?

A pet's skin always carries some normal bacteria, so a germ that grows is not always the one causing the trouble. The vet reads the culture with the smear, the look of the skin and the pet's history, and may repeat the test if the sample was poor.

Read next

If a lump rather than a rash is worrying you, Biopsy or FNAC: Which Test for a Lump in a Pet? explains how the vet chooses between a needle sample and a tissue sample. When itching is the main complaint, IgE Blood Tests in Itchy Pets: What They Can and Cannot Show looks at what an allergy blood test can and cannot tell you.

Testing in Bhopal

Pet owners in Bhopal can ask for free sample collection from home, and the lab is at C-200, C Sector, Shahpura, Bhopal. Samples from other districts can arrive by courier, bus parcel or through your vet. Call or WhatsApp +91 88175 01118, and the lab confirms the method, sample needs and reporting time when you book. Your vet can take the skin swab cleanly, so book the test after the visit.