Group D Streptococcus (GDs) Infections - Pathophysiology, Causes, Diagnosis, and Treatment

Introduction

Streptococcus Bovis/gallolyticus is a type of bacterial species classified under Group D streptococcus (GDS). They are predominantly found in the gastrointestinal tract of human beings and animals. Streptococcus gallolyticus was formerly known as Streptococcus Bovis. They are the main causative organism of septicemia and infective endocarditis in the elderly population and immunocompromised individuals. It has also been found to cause colorectal cancer (CRC) and liver disease.

Less common infections include:

• Urinary tract infections.

• Meningitis (inflammation of the membranes of the brain).

• Neonatal sepsis (infection of an infant’s blood).

• Spontaneous bacterial peritonitis (inflammation of the abdominal wall cover).

• Septic arthritis (joint infection).

• Vertebral osteomyelitis (infection of the backbone).

Streptococcus Bovis mostly cause group D streptococcal infections. One of the unique characteristics of Streptococcus Bovis is its ability to grow in bile but not in 6.5 % sodium chloride.

What Is the Pathophysiology of Group D Streptococcus Infection?

Bacterial infections usually are not thought to be a direct cause of cancer. However, bacteria are found to be associated with cancer by two mechanisms: chronic inflammation and the production of cancer-causing substances. It has been found that bacteria cause cancer by producing toxic by-products of certain metabolism in the body.

Streptococcus Bovis enters the body through the gastrointestinal tract. In some cases, the urinary tract, liver, mouth, and throat can also be the source of infection. Streptococcus Bovis bacteremia is mostly associated with cancer or precancerous lesions of the colon. Bacteremia is the presence of bacteria in the bloodstream. The bacteria have also been found in the stools of such patients.

Streptococcus Bovis has also been associated with noncancerous as well as cancerous diseases of the colon. Relationships between bacteremia or endocarditis and chronic liver disease have also been reported. In a few rare cases, gastric cancer has also been associated with Streptococcus Bovis bacteremia. Recently WHO considered bacteria as possible cancer-causing agents.

What Is the Epidemiology of Group D Streptococcus Infection?

The SENTRY antimicrobial surveillance program does not list group D Streptococcus among the ten most common organisms causing bacteremia in the United States. According to the SCOPE program, streptococci was around six percent of all the blood culture tests in thirty U.S hospitals.

Streptococcus Bovis was around 2.4 % among the other streptococci bacteria. In 1997, a review of the international collaboration on endocarditis merged database (ICE-MD) found that Streptococcus Bovis was responsible for around 16.7 % of all streptococcal-caused infective endocarditis in the United States.

Internationally, SENTRY data shows that Streptococcus Bovis was found in 1.3 % and 1.6 % cases of streptococcal bacteremia in Canada and Latin America, respectively. In a German study, 177 cases of infective endocarditis were reported between 1983 and 1996, out of which twenty-two cases were caused by Streptococcus Bovis. Recent studies have found an association between infective endocarditis caused by Streptococcus Bovis, mainly in France and neighboring countries of southern Europe.

What Causes Group D Streptococcus Infections?

Group D streptococci and other similar bacteria belong to the family streptococcaceae. Group D streptococci, at times, are also referred to as Streptococcus bovis and Streptococcus equinus complex. Streptococcus Bovis has recently been named streptococcus gallolyticus. Streptococcus has further been classified into Streptococcus Bovis-I and Streptococcus Bovis-II. Streptococcus Bovis-I is commonly associated with endocarditis (inflammation of the inner lining of the heart valves and chambers) and cancerous or noncancerous injuries. Streptococcus Bovis-II is commonly associated with bacteremia of the liver and related structures.

What Are the Clinical Features of Group D Streptococcus Infections?

Streptococcus Bovis infection generally presents with bacteremia and fever.

The signs and symptoms of endocarditis caused by Streptococcus Bovis include:

1. Presence Of Heart Murmurs - The extra noise heard during a heartbeat. It is heard when the blood does not flow through the heart smoothly. These murmurs develop with time.

2. Splinter Hemorrhages - These are thin reddish-brown lines of blood under the nail.

3. Conjunctival Petechiae - Red or purple spots on the conjunctiva.

4. Osler Nodules - These are red-purple, tender nodules on the skin.

5. Janeway lesions - These are non-tender, bleeding nodules on the skin.

6. Roth Spots - These are reddish spots on the retina of the eye.

7. Embolism - Small dislodged particles blocking an artery.

8. Anorexia - is an eating disorder.

9. Septic Infarction Or Vascular Occlusion - It is the blockage of an artery.

10. Kidney Failure - Is caused by immune-complex glomerulonephritis.

11. Cerebral Hemorrhage is caused by a ruptured mycotic aneurysm (infection of the blood vessel wall).

12. Weight loss.

How Are Group D Streptococcal Infections Diagnosed?

Laboratory Tests Include:

• Complete blood count.

• Blood cultures - A positive blood culture test usually comes during the first 24 to 48 hours.

• Electrolyte evaluation.

• Creatinine level.

• Liver function tests.

Radiology:

• Echocardiography.

• Colonoscopy - This is done to find out the cancerous areas of the colon.

• Esophagogastroduodenoscopy (EGD) - It is used to detect the presence of cancerous areas in the esophagus, stomach, and duodenum.

• Liver ultrasound and CT scanning - It is done in case of liver disease.

Other Tests Include:

MIC (minimal inhibitory concentration) testing - In case the organism is antibiotic resistant, an antimicrobial susceptibility test or MIC testing is required.

How Are Group D Streptococcal Infections Treated?

• Most Streptococcus Bovis are susceptible to Penicillin.

• Intravenous administration of Penicillin is effective if given for four weeks.

• For moderate antibiotic susceptibility, Penicillin and Gentamicin are administered for four weeks and two weeks, respectively.

• Surgery is recommended in case of heart failure or complicated endocarditis.

• Mycotic aneurysm clipping may be indicated after cerebral arteriography.

• Colon or liver surgery can be done if required.

Medications are used to eliminate the infection, prevent complications, and reduce the mortality risk.

• Penicillin G.

• Ceftriaxone.

• Vancomycin.

• Gentamicin.

Conclusion

Streptococcus Bovis/gallolyticus are bacteria that belong to the group D streptococci. They are most commonly found in the intestines of healthy individuals. They are associated with liver disease, meningitis, endocarditis, and colorectal cancer. Streptococcus Bovis was renamed streptococcus gallolyticus in 2003. It is highly sensitive to Penicillin. As a precaution, patients with Streptococcus bovis infection with or without endocarditis should undergo a check for gastrointestinal cancer. Endocarditis caused by Streptococcus is a severe infection. It is highly fatal if left untreated. The increased mortality risk is related to the severity of the infection and the presence of other underlying diseases.