Clinical Testing

The VDHL offers screening for enteric bacterial pathogens from stool samples. Bacteria most commonly associated with food-borne illnesses are isolated and identified through a combination of culture, biochemical and enzyme immunoassay tests. Stool samples must be submitted in a culture and sensitivity media (Kit #1 containing modified Cary-Blair medium).

Health care providers can order kits from the laboratory or patients may pick up kits at the laboratory with a note from their health care provider with the request.

Specimens submitted for enteric screening are tested for the following organisms: 

• Salmonella
• Shigella
• Campylobacter
• E. coli O157
• Shiga-toxin producing E. coli
• Yersinia
• Vibrio (upon request)
• Aeromonas (upon request)

Per Vermont's Reportable and Communicable Disease Rule, hospitals are required to submit positive cultures/specimens to the VDHL for confirmation and PFGE testing for Salmonella, Shigella, Campylobacter, E. coli O157, Shiga-toxin producing E. coli, Yersinia and Vibrio. Slants, CNS media, VDHL Kit #1 and plates are accepted. Hospital laboratories that perform Culture Independent Diagnostic Tests (CIDT) may submit stool samples in CNS or in a VDHL Kit #1. 

See more information on enteric diseases from the CDC

The VDHL serves as a reference laboratory for the culture and identification of bacterial isolates that may be of public health significance. Clinical samples may be accepted for primary isolation, but pure isolates are required for identification and serotyping.  

Laboratories experiencing difficulties with identification of certain organisms may contact the VDHL for possible referral to the Centers for Disease Control (CDC).

Note: Anaerobic testing is not performed at Vermont Department of Health Laboratory.

The following services are available from the VDHL's Reference Bacteriology Lab:

• Culture and Identification of Neisseria gonorrhoeae
• Identification and Serotyping of Neisseria meningitidis
• Serotyping of Haemophilis influenza from sterile sites
• Culture and Identification of Legionella spp.
• Serotyping of Salmonella spp.
• Confirmation of E.coli O157:H7
• Identification of Shiga-toxin producing E.coli, non-O157:H7
• Identification and grouping of Shigella spp.
• Serotyping of Vibrio cholerae (Ogawa and Inaba)
• Culture and Identification of Campylobacter species
• Culture and Identification of Listeria spp.
• Phenotypic and genotypic analysis of Carbapenemase producing enterobacteriacea
• Identification of Yersinia enterocolitica
• Identification of Aeromonas species.

The Vermont Department of Health Laboratory uses two assays for detection of Bordetella pertussis and Bordetella parapertussis from nasopharyngeal swabs.

• The PCR test amplifies the genetic material of the bacteria when present in a sample so it can be detected. Testing is usually performed on Mondays and Thursdays.

• Pertussis culture allows the recovery of the bacteria to investigate potential outbreaks. Typically a pertussis culture and PCR test can both be ordered as early in the illness as possible. Culture results are available seven days after sample receipt.

More information from the Health Department on whooping cough

For more information from the CDC on whooping cough

For information on best practices for using PCR for diagnosis of pertussis (CDC)

The VDHL offers a nucleic acid amplified test (Kit #7) for simultaneous detection of chlamydia and gonorrhea from:

• Urine

• Endocervical swabs

• Patient collected vaginal swabs

Find information on Vermont’s Sexually Transmitted Disease (STD) program and services.

Find more information on sexually transmitted diseases from the CDC

Brucellosis is an infectious disease caused by the Brucella species bacteria. The most common ways people get this disease is by consuming undercooked meat or unpasteurized dairy products, breathing in the bacteria, or the bacteria entering the body through a wound after touching an infected animal. The most commonly infected animals include sheep, cattle, goats, pigs and dogs. 

Tularemia is an animal and human disease caused by the bacterium Francisella tularensis. Humans can become infected through tick and deer fly bites, skin contact with infected animals, drinking contaminated water, or breathing in contaminated aerosols or agricultural dusts.

The VDHL performs agglutination tests to detect Brucella or Francisella antibodies in blood serum specimens.

For the optimal test interpretation, two serum specimens should be submitted. The first specimen should be collected while the patient is exhibiting symptoms. The second should be collected two to three weeks later. A significant increase in the antibody level between the two specimens could indicate an exposure to Brucella or Francisella. 

See more information from the Health Department on Francisella

See more information from the CDC on Brucellosis

Syphilis is a sexually transmitted disease that can have serious health complications if not treated early. 

Two Syphilis blood serum tests are performed at the VDHL:

RPR – The Rapid Plasma Reagin test is a non-treponemal test. When a person is infected with syphilis,  cellular damage occurs, resulting in the release of specific lipids into the bloodstream. The RPR test detects antibodies produced by the body against these specific lipids. The RPR test can be used to gauge how effective treatment is, the test will become negative when the person is successfully treated. The RPR test can result in false positives, especially if a patient has other underlying health conditions such as lupus or rheumatic fever. The VDHL will confirm all positive RPR results with a treponemal test. (FTA-ABS test). 

FTA-ABS  - The Treponemal Antibody-Absorption test looks for antibodies produced by the body against the bacteria itself (Treponema pallidum). The FTA-ABS test is performed on all positive RPR test results to rule out the possibility of a false positive result. If the FTA-ABS test is positive, it confirms the patient has been exposed to the bacteria. The FTA-ABS test is not an acceptable test to determine how effective treatment is because patients who test FTA-ABS positive produce antibodies against Treponema pallidum for life. 

Find more information from the CDC on Syphilis.

Find information on Vermont’s Sexually Transmitted Disease (STD) program and services.

• The QFT-Plus is an interferon-gamma (IFN-y) release assay, commonly known as an IGRA, and is a current alternative to the tuberculin skin test (TST or Mantoux). Unlike the TST, the QFT-Plus is a controlled laboratory test that requires only one patient visit and is unaffected by previous vaccination with Bacille-Calmette Guerin (BCG).

• The QFT-Plus consists of a 4-tube collection system optimized with tuberculosis-specific antigens that elicit both CD8 and CD4 T cell responses.  It has been shown that CD8 T cells have a higher frequency of detection in people with active TB disease vs. latent infection and allows for greater detection in active TB subjects with HIV co-infection and in young children.

• A positive QFT-Plus is a strong indicator of exposure to TB, but it cannot differentiate between active infection with TB and latent tuberculosis infection (i.e. a person who has no signs or symptoms of disease). 

• Positive QFT-Plus results are used in conjunction with risk assessments, radiography, and other medical and diagnostic evaluations by the patient’s doctor.

The Influenza Surveillance program is a year-round monitoring program used to determine which influenza strains are circulating in Vermont's human population. This information is used by the CDC for influenza vaccine development. 

Real-time PCR is used at the VDHL to analyze clinical specimens from participating sentinel influenza providers, hospital emergency departments enrolled in the Early Aberration Reporting System (EARS), long-term care facilities, and medical providers with special requests (e.g. hospitalized patient with influenza-like-illness or a suspect H5N1 case). 

Predominant strains in Vermont include Influenza A (subtypes H1, H3, and the less common H5 and H7) and Influenza B (lineages Victoria and Yamagata).

Find more information from the Health Department on Influenza Surveillance here.

Norovirus is the leading cause of acute gastroenteritis and viral foodborne-disease illness in the United States. It is highly contagious and can spread from person to person, or through contaminated food, water, or surfaces. Norovirus can be serious, especially for young children and older adults.

The VDHL participates in a national norovirus surveillance network called CaliciNet, supported by the CDC, which monitors for current norovirus strains and helps to identify newly emerging strains. 

All requests for norovirus testing must have prior approval from Vermont Department of Health Epidemiology. 

If you suspect a norovirus outbreak, call the Health Surveillance Division at 802-863-7240 or 1-800-640-4374 (toll free in Vermont).

• More information on norovirus from the CDC

• More information on food safety and norovirus

• More information from the CDC on CaliciNet

The Vermont Arbovirus Surveillance Program is a cooperative initiative between the Department of Health and the Agency of Agriculture, Food and Markets. It monitors the presence of Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV) in mosquitoes.

Mosquitoes are obtained using various trapping methods by the Agency of Agriculture from towns throughout the Vermont. The mosquitoes are submitted to the VDHL for testing using real-time PCR. 

Test results are posted on the Health Department’s website, allowing state and local governments to determine what the threat is to public health. The public can use this information to determine if extra precautions, such as the use of insect repellents, may be necessary when spending time outside. 

Find more information on Mosquito-borne Diseases (Arbovirus), including Surveillance, Testing and Data (Health Department).

Measles, mumps, rubella, and varicella (chickenpox) are vaccine-preventable viral diseases that are spread from person to person through the air. Varicella can also be spread through contact with the fluid filled blisters. 

The VDHL can test blood serum specimens for the presence of antibodies produced against measles, mumps, rubella and varicella by using an enzyme immunoassay. Patients with positive test results are said to have acceptable antibody levels to prevent disease. Patients who do not have detectable levels of antibodies should discuss the result with their physician to determine if a vaccine booster is required. Serum is the preferred specimen type for the immunoassay tests.

If active disease is suspected for measles or mumps, the Laboratory uses real-time PCR test methods to determine if detectable levels of virus are present in the patient’s blood. 

For the measles real time PCR test, throat (oropharyngeal), nasal or NP (nasopharyngeal) swabs are the preferred specimen types. For the mumps PCR test, oral swabs, buccal swabs and urine specimens are the preferred specimen types.

• More information from the Health Department on mumps

• More information from the CDC on mumps

• More information from the Health Department on measles

• More information from the CDC on measles

• More information from the Health Department on varicella

• More information from the CDC on varicella

• More information from the CDC on rubella

Hepatitis B and C are viruses that spread most commonly through blood or through IV drug use. Both viruses usually result in a short term illness. However, in some people the disease can become chronic, resulting in severe damage to the liver (cirrhosis). A vaccine is available for Hepatitis B, but currently there is no vaccine for Hepatitis C. 

The VDHL can test blood serum specimens for the presence of antibodies produced against the hepatitis virus by using an enzyme immunoassay.

There are three key markers targeted for Hepatitis B (Hepatitis B surface antigen, core antigen, and surface antibody), which aids physicians in determining acute or chronic disease in the patient. 

The Laboratory can also test patients with a known Hepatitis B vaccine history to determine if they are immune or require a booster. 

The Laboratory also provides serological testing for Hepatitis C virus.

• More information from the Health Department on Hepatitis B

• More information from the Health Department on Hepatitis C

• More information from the CDC on Hepatitis B and C

Human Immunodeficiency Virus (HIV) infection is spread by contact with blood and other body fluids. HIV attacks disease-fighting cells in the body called CD4 T cells, resulting in a lowered immune response to other infectious agents such as bacteria or other viruses. The two most common types of HIV are HIV-1, found worldwide, and HIV-2, a less common type principally found in Africa. 

The VDHL uses two tests that detect antibodies made by the body in response to HIV. 

The first and most sensitive HIV test used is a 4^th generation combination antigen/antibody immunoassay. This test detects HIV-1, HIV-2, and the HIV-1 p24 antigen. The 4^th generation immunoassay has the earliest detection of the HIV-1 p24 antigen, which is detectable around 15 days post infection in blood. 

Positive specimens are confirmed with an additional assay that will differentiate between HIV-1 or HIV-2. 

The second antibody immunoassay available at the Laboratory is used to test oral fluid specimens. Oral fluid may be preferred by patients as it a quick and less invasive specimen to collect. An oral fluid swab (collected in the designated collection container) is stable at room temperature for 21 days, allowing for more shipment options. 

Detection of HIV antibody by the oral fluid test is not usually possible until approximately 30 days post infection. Confirmation by the use of the Western Blot, which only detects HIV-1, is also required for oral fluid specimens.

• Fast Facts from the CDC on HIV

• Information from the Health Department on anonymous and confidential HIV testing