Strep gallolyticus is a bacterium involved in human health. While it commonly resides in the gut without causing issues, it has a notable connection to specific medical conditions. Understanding this bacterium, its typical environment, and how it can impact health is important.
Understanding Strep gallolyticus
Strep gallolyticus is a bacterium that was previously known as Streptococcus bovis biotype I. It belongs to the Streptococcus genus. This reclassification helps in more accurately identifying its specific characteristics.
This bacterium is Gram-positive and a facultative anaerobe, meaning it stains purple in a Gram stain test and can grow with or without oxygen. It is non-motile and does not form spores. Under a microscope, Strep gallolyticus appears as spherical cells arranged in pairs or chains.
Its natural habitat is primarily the gastrointestinal tract of humans and animals. Strep gallolyticus is known for its ability to break down complex carbohydrates and can degrade tannins, which are organic compounds found in plants. This characteristic is reflected in its name, “gallolyticus,” referring to its capacity to decarboxylate gallate, an acid derived from tannin degradation.
Its Connection to Serious Illnesses
Strep gallolyticus is linked to two health conditions: infective endocarditis and colorectal cancer. The presence of this bacterium in the bloodstream often prompts further medical investigation due to these associations.
Infective endocarditis is an infection of the inner lining of the heart, or its valves. Strep gallolyticus is a recognized cause of this condition, particularly in older individuals or those with pre-existing heart valve issues. The bacterium possesses surface structures called pili, which help it attach to and colonize heart valves, especially at sites of tissue damage where collagen is exposed. This adherence can lead to the formation of vegetations, which are masses of bacteria and host cells on the heart valves.
The association between Strep gallolyticus and colorectal cancer (CRC) is well-documented and often leads to a recommendation for a colonoscopy if the bacterium is found in the blood. Studies have shown that a significant percentage of patients (25% to 80%) with Strep gallolyticus bacteremia also have underlying colorectal tumors. This strong epidemiological link suggests that the bacterium may either contribute to the development of these lesions or thrive in the tumor environment.
One hypothesis is that Strep gallolyticus might promote inflammation within the colon, which can contribute to cancer progression. Another idea suggests the bacterium acts as a marker for existing gastrointestinal lesions, as these may provide an entry point into the bloodstream. The bacterium’s ability to bind to collagen, often expressed in damaged tissues, could facilitate its passage into the blood from pre-malignant polyps or tumors.
Identification and Treatment
Identifying Strep gallolyticus infections begins with laboratory tests. Blood cultures are the primary diagnostic method for systemic infections, detecting the bacterium within 24 to 48 hours.
Once Strep gallolyticus is identified in the bloodstream, further investigative procedures are often necessary to determine the source of the infection and any associated conditions. For suspected infective endocarditis, an echocardiogram is commonly performed to visualize vegetations on heart valves. In cases of Strep gallolyticus bacteremia or endocarditis, a colonoscopy is generally recommended due to the strong association with colorectal neoplasia. This procedure helps detect adenomas or carcinomas in the colon.
Treatment for Strep gallolyticus infections primarily involves antibiotic therapy. Most strains are susceptible to common antibiotics like penicillin G and ampicillin. For patients with penicillin allergies, vancomycin is a suitable alternative. Ceftriaxone is another antibiotic to which Strep gallolyticus isolates have shown susceptibility.
Antibiotic susceptibility testing is performed to guide the choice and duration of treatment, ensuring the most effective antibiotic is used. In cases of infective endocarditis, a combination therapy that includes gentamicin may be considered for the initial two weeks, although this is weighed against potential side effects like kidney or ear toxicity. The duration of antibiotic treatment can range from four to six weeks, depending on the severity and type of infection. Beyond antibiotics, managing any underlying conditions, such as surgical intervention for severe endocarditis or the removal of polyps or treatment of tumors for colorectal cancer, is an important part of comprehensive care.