Streptococcus agalactiae

• Bacteria called group B Streptococcus (group B strep, GBS) commonly live in people’s gastrointestinal and genital tracts.
• The gastrointestinal tract is the part of the body that digests food and includes the stomach and intestines.
• The genital tract is the part of the body involved in reproduction and includes the vagina in women.
• Most of the time the bacteria are not harmful and do not make people feel sick or have any symptoms.
• Sometimes the bacteria invade the body and cause certain infections, which are known as GBS disease.

Streptococcus agalactiae

Cause

Streptococcus agalactiae or group B Streptococcus (group B strep, GBS) cause GBS disease.

Incidence

Approximately 30,800 cases of invasive GBS disease occur annually in the United States in all age groups.

Types of Infections

GBS bacteria can cause many types of infections:

• Bacteremia and sepsis
• Bone and joint infections
• Meningitis
• Pneumonia
• Skin and soft-tissue infections

Streptococcus agalactiae on Granada medium

GBS most commonly causes bacteremia, sepsis, pneumonia, and meningitis in newborns. It is very uncommon for GBS to cause meningitis in adults.

Risk factors

GBS disease is most common in newborns. There are factors that can increase a pregnant woman’s risk of having a baby who will develop GBS disease, including:

• Testing positive for GBS bacteria late in pregnancy
• Developing a fever during labor
• Having 18 hours or more pass between when their water breaks and when their baby is born

Other medical conditions that put adults at increased risk include:

• Diabetes
• Heart disease
• Congestive heart failure
• Cancer or history of cancer
• Obesity

Risk for serious GBS disease increases as people get older.

Beta hemolysis on blood agar

Transmission

• GBS bacteria commonly live in people’s gastrointestinal and genital tracts.
• The gastrointestinal tract is the part of the body that digests food and includes the stomach and intestines.
• The genital tract is the part of the body involved in reproduction and includes the vagina in women.
• The bacteria do not spread through food, water, or anything that people might have come into contact with.
• How people get these bacteria or spread them to others is generally unknown.
• Most babies who get GBS disease in the first week of life (early-onset) are exposed to the bacteria this way.
• Babies who develop GBS disease from the first week through three months of life have late-onset disease.
• The bacteria may have come from the mother during birth or from another source.
• Other people that live with someone who has GBS bacteria, including other children, are not at risk of getting sick.

Signs and symptoms

In Newborns and Their Mothers The symptoms of GBS disease can seem like other health problems in newborns and babies. Symptoms include:

Streptococcus group B

• Fever
• Difficulty feeding
• Irritability or lethargy
• Difficulty breathing
• Blue-ish color to skin
• Babies who get it in the first week of life have “early-onset GBS disease.”

Symptoms of bacteremia (blood stream infection) and sepsis (the body’s extreme response to an infection) include:

CAMP test

• Fever
• Chills
• Low alertness

Symptoms of pneumonia:

• Fever
• Chills
• Cough
• Rapid breathing or difficulty breathing
• Chest pain

Skin and soft-tissue infections:

• Red
• Swollen or painful
• Warm to the touch
• Full of pus or other drainage
• People with skin infections may also have a fever.

Bone and joint infections:

• Fever
• Chills
• Swelling
• Stiffness or inability to use the affected limb or joint

Streptococcus agalactiae

Lab tests

A culture and sensitivity test is usually performed of the blood, urine or CSF. It can take a few days to get these results since the bacteria need time to grow. Sometimes GBS bacteria can cause urinary tract infections when a sample of urine to diagnose urinary tract infections.

=CAMP test

• If the laboratory is not able to identify group B streptococci (GBS) by the Lancefield grouping procedure, there are other microbiologic tests that can be used to identify GBS. This picture shows one of these tests.
• It is called the CAMP test where CAMP is an acronym for the authors of this test (Christie, Atkinson, Munch, Peterson).
• The CAMP test takes advantage of the capacity of GBS to produce this CAMP factor; most other hemolytic streptococci do not produce CAMP factor. This picture shows the group B Streptococcus (on the right) and a group A Streptococcus (GAS) (on the left).
• Down the middle we have inoculated the plate with a Staphylococcus aureus strain (vertical streak).
• We then inoculated the GBS (on right) and GAS (on left) perpendicular to the Staphylococcus streak.
• We inoculated the agar plate so as not to touch the two different organisms (Staphylococcus and Streptococcus) but to come close to each other.
• The Staphylococcus is used because it produces a lysin that only partially lyses the red blood cells (called beta-lysin).
• The CAMP factor reacts with the partially lysed area of the blood agar plate to enhance the hemolytic activity.

Treatment

• Treatment is with antibiotics such as beta-lactams, which includes penicillin and ampicillin.
• Sometimes people with soft tissue and bone infections may need additional treatment, such as surgery.
• Treatment will depend on the kind of infection caused by GBS bacteria.
• Patients should ask their or their child’s doctor about specific treatment options.

Complications

• Active surveillance for invasive GBS disease is ongoing in a multistate population.
• Neurologic sequelae include sight or hearing loss and cerebral palsy.
• Death occurs in about 5% of infants and adults.

Streptococcus agalactiae Resources
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