D135
Culture and Sensitivity, Serology, and Virus Isolation 

  1. Bacterial Culture and Sensitivity: Anytime a bacterial infectious agent is suspected, it is highly recommended that a culture and sensitivity be performed. Problems such as diarrhea, abortions, pneumonia, and abscesses are reasons to use culture and sensitivity. Samples that can be submitted for culture and sensitivity include the following:
  1. Manure from an animal with diarrhea. A small sample should be taken from the animal. Avoid contaminating the sample with manure from other animals.
  2. A sample taken from the nasal passages, lungs, a wound, or abscess. 
  3. Tissue and organ samples taken from an animal that has been recently euthanized or has died from other causes. Testing the entire aborted fetus and placenta is often helpful.

(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 responds 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.

Risks to Patient: Varies, depending on the sample needed to 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 removing 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, abortions, and diarrhea would indicate the need for identification of the possible viral cause. 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 often require a second blood sample to be taken 14-21 days after the first.)
  2. Manure from an animal with diarrhea.
  3. A sample taken from the nasal passages or lungs.
  4. Tissue and organ samples taken from an animal that has been recently euthanized or has died from other causes. Submit the entire aborted fetus and placenta if possible.

(Contact a veterinarian for specifics on handling these samples.)

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 - This is where the lab actually finds and identifies the virus. This test can be expensive, but is very specific for identifying the virus.
  2. IFA or indirect fluorescent antibody - This is another test to identify the specific virus. These tests are often performed 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 responses are referred to as titers and can sometimes appear as a response to vaccination. Therefore, a second blood sample is often taken and tested to help determine if there is a natural infection or just a response to vaccination.
  4. ELISA or enzyme linked immunosorbent assay - This is also a blood test looking for the specific antibodies produced by the immune system against a particular virus. These tests can also identify the actual virus.

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

Diagnostic Value: 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.