D135
Culture and Sensitivity,
Serology, and Virus Isolation

  1. Bacterial Culture and Sensitivity: When a bacterial infectious agent is suspected, it is recommended that a culture and sensitivity be performed. Problems such as diarrhea, ear infections, pneumonia, urinary tract infections, and abscesses are reasons to use culture and sensitivity. Samples that can be submitted for culture and sensitivity include the following:
  1. Feces from an animal with diarrhea. A small sample of feces should be taken from the animal. Avoid contaminating the sample with feces from other animals.
  2. A sample taken from the nasal passages, lungs, wound, or abscess.
  3. A sample of urine.
  4. An ear swab.

(Obtaining and handling these types of samples requires special training and may require a veterinarian’s assistance.)

Performing a culture involves obtaining the desired sample and submitting it to the appropriate laboratory as quickly as possible. At the lab, the sample is placed on a culture medium where bacteria are allowed to grow. Identifying the specific bacteria is based on the growth characteristics of the bacteria on a particular culture medium, microscopic examination, and other procedures. Once the type of bacteria is determined, the bacteria is subjected to several different antibiotics. Sensitivity will be determined, based on how the bacteria respond to the antibiotics. Sensitivities are reported as Resistant, Sensitive, and Intermediate. Resistant means the particular antibiotic is not effective against that bacteria. Sensitive means the particular antibiotic is effective against that bacteria, and intermediate means the antibiotic is moderately effective against that bacteria. The appropriate treatment for the problem can then be initiated without trying to guess which antibiotic may or may not work.

Diagnostic Value: Very high, especially for infections which are difficult to treat such as recurring urinary tract infections and bone infections.

Risks to Patient: The risks vary, depending on the sample needed for culture. Fecal cultures, for example, pose no risk at all to a patient, whereas a culture and sensitivity of a liver abscess would pose a much greater risk, possibly requiring surgery and removal of a small portion of liver.

Relative Cost: Moderate.

  1. Serology and Virus Isolation: When a viral cause of disease is suspected, it may be recommended that the specific virus be identified. Problems such as pneumonia or diarrhea are situations where the exact viral cause can be identified. Samples that can be used for virus identification include the following:
  1. Blood samples for serology. (These samples indicate whether an animal has been exposed to a specific virus, and may require a second blood sample to be taken 14-21 days after the first.)
  2. Feces from an animal with diarrhea.
  3. A sample taken from the nasal passages or lungs.

Once these samples are properly taken and transported to the appropriate laboratory, multiple tests can be performed. Some of the tests include the following:

  1. Virus isolation - The lab actually finds and identifies the virus. This test can be expensive but is very specific for identifying the virus.
  2. IFA (Indirect Fluorescent Antibody) - This test is used to identify a specific virus. These tests are often used to identify an animal infected with rabies or when respiratory problems are suspected.
  3. Serologic tests - These tests are performed on blood samples and are used to determine immune responses to specific viruses. These immune system responses are referred to as titers and can sometimes result from vaccination. As a consequence, a second blood sample is often taken and tested to help determine if the animal has a natural infection or just a response to vaccination.
  4. ELISA (Enzyme Linked Immunosorbent Assay) - This is also a test looking for a specific virus. The FeLV/FIV snap test on page D228 is an example of this type of test.

Once a specific virus has been identified as the problem, appropriate measures such as vaccination of exposed animals can be initiated.

Diagnostic Value: Diagnostic value is very high, especially for infections which are difficult to treat.

Risks to Patient: Varies, depending on the procedure used to obtain the sample.

Relative Cost: Moderate to high.