What Is Streptococcus Group F?
Streptococcus group F bacteria, also known as Streptococcus anginosus group or Strep milleri, are a group of Gram-positive cocci that can cause infections in humans. The group includes three main bacterial species:
- Streptococcus anginosus
- Streptococcus intermedius
- Streptococcus constellatus
These bacteria are part of the normal flora found in the mouth, gastrointestinal tract, and urogenital tract. However, they can sometimes cause infections if the bacteria enter the bloodstream or sterile sites in the body like the central nervous system.
Key Features of Streptococcus Group F
Streptococcus group F has the following key features:
- Gram-positive cocci that appear in chains or pairs under the microscope.
- Facultative anaerobes - can grow with or without oxygen.
- Catalase-negative and bile insoluble.
- Cannot ferment sodium hippurate.
- Variable ability to hydrolyse esculin and ferment carbohydrates.
They are distinguished from other streptococcal groups like streptococcus pyogenes (group A strep) by their different carbohydrate fermentation patterns and cell wall antigens.
Infections Caused by Streptococcus Group F
Streptococcus group F most commonly causes infections at sites colonized with the bacteria such as the mouth, GI tract, or female genital tract. However, the bacteria can spread to cause invasive infections including:
Abscesses
Strep group F bacteria are a common cause of abscesses in internal organs such as the brain, liver, and abdominal cavity. They can also cause skin, muscle, and lung abscesses, particularly after surgery or trauma.
Bacteremia
The bacteria may enter the bloodstream from an infection at a mucosal site like the mouth or GI tract, leading to bacteremia. This bloodstream infection is often polymicrobial with other oral streptococci.
Endocarditis
Strep group F can cause a serious infection of the inner lining of the heart known as infective endocarditis. This infection can damage or destroy heart valves.
Meningitis
Streptococcus group F is an uncommon cause of meningitis, an infection of the membranes surrounding the brain and spinal cord. It accounts for 1-3% of bacterial meningitis cases.
Pneumonia
The bacteria can also spread from the throat or sinuses to cause pneumonia, an infection of the lungs. This may occur in people with underlying lung disease.
Peritonitis
Peritonitis is inflammation of the peritoneum, the thin tissue lining the inner wall of the abdomen. Strep group F can cause peritonitis arising from the gastrointestinal tract or female genital tract.
Toxic Shock Syndrome
Rarely, streptococcus group F may release toxins into the bloodstream causing toxic shock syndrome. This is a life-threatening condition involving fever, low blood pressure, and multi-organ failure.
Risk Factors
Factors that increase the risk of developing an invasive Strep group F infection include:
- Recent surgery or trauma
- Diabetes
- Cancer
- Liver disease
- Heart disease or heart valve abnormalities
- HIV/AIDS
- Immunosuppressant drugs
- Dialysis treatment
The bacteria may enter the bloodstream more easily in people with pre-existing wounds, medical devices like catheters, or a weakened immune system.
Diagnosis
Diagnosing an invasive Strep group F infection may involve:
Blood Cultures
Blood cultures can detect streptococcus group F bacteremia. A sample of blood is added to bottles containing nutrients to encourage bacterial growth.
Culture of Infected Site
Culturing pus from an abscess or fluid from normally sterile sites like the cerebrospinal fluid or joint fluid can identify the bacteria.
PCR
Polymerase chain reaction (PCR) tests can rapidly detect Strep group F DNA in blood, cerebrospinal fluid or other samples.
Imaging Tests
Imaging studies like X-rays, CT scans or MRI scans may help locate abscesses or signs of infection in organs.
Endocarditis Diagnosis
Endocarditis may be suspected based on certain echocardiogram findings. Other criteria like positive blood cultures are used to make the diagnosis.
Treatment
Treatment of invasive Strep group F infections involves:
Antibiotics
Intravenous antibiotics are used to treat serious Strep group F infections. Penicillins like ampicillin are commonly used. Cephalosporins, vancomycin, or clindamycin may also be options.
Abscess Drainage
Draining pus from abscesses by surgery or radiology procedures helps remove the infection source. This may promote healing.
Surgery
Surgery may be necessary to remove infected heart valves in endocarditis or implanted medical devices infected with strep group F bacteria.
Supportive Care
Supportive treatments like IV fluids and medications to maintain blood pressure may be needed for sepsis or shock.
Complications
Potential complications of invasive Strep group F infections may include:
- Sepsis - life-threatening bloodstream infection
- Septic shock with dangerously low blood pressure
- Heart failure or heart valve damage from endocarditis
- Brain damage from meningitis
- Abscess rupture spreading infection
- Toxic shock syndrome
- Death in severe cases
Prevention
Preventing Strep group F infections centers around:
- Good wound care and hygiene to prevent bacterial entry into the bloodstream
- Not using antibiotics unnecessarily which can allow drug-resistant Strep strains to develop
- Practicing safe healthcare infection control in hospitals and clinical settings
- Good dental care and oral hygiene to prevent strep gaining entry from the mouth
- Vaccines like pneumococcal vaccine to help prevent respiratory infections that may spread to become invasive
There is currently no vaccine available specifically targeting Strep group F bacteria.
Prognosis
The prognosis for invasive Strep group F disease depends on:
- The site of infection
- How quickly treatment is started
- The person's age and medical history
- Complications like septic shock or meningitis generally worsen the prognosis
With prompt appropriate antibiotic treatment and drainage procedures if needed, many patients recover fully. However, mortality rates may approach 10-30% or higher for more severe infections like endocarditis or meningitis caused by Strep group F bacteria.
Key Points About Streptococcus Group F Infections
- Strep group F includes S. anginosus, S. intermedius, and S. constellatus bacteria that colon
FAQs
What types of infections does streptococcus group F cause?
Strep group F bacteria mainly cause abscesses in organs like the liver or brain. They can also lead to bacteremia, meningitis, pneumonia, peritonitis, endocarditis, and toxic shock syndrome in some cases.
How do you diagnose a Strep group F infection?
Culturing blood, pus, or fluids from normally sterile sites can identify Strep group F. PCR tests and imaging studies like CT scans may also help diagnosis. Blood cultures are done to detect bacteremia.
What is the treatment for Strep group F infections?
Intravenous antibiotics like penicillins, cephalosporins or vancomycin are used to treat serious Strep group F disease. Drainage of abscesses, valve surgery for endocarditis, and supportive care may also be needed.
Who is most at risk for invasive disease from Strep group F?
People with recent surgery, trauma, diabetes, cancer, liver or heart disease, dialysis treatment, and those taking immunosuppressant drugs or with HIV/AIDS are at higher risk of invasive Strep group F infections.
How can you prevent Strep group F infections?
Good wound care and hygiene, prudent antibiotic use, infection control in hospitals, dental care, and vaccines like pneumococcal vaccine may help prevent Strep group F infections.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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