What is the diagnosis and management for a 90-year-old patient presenting with recurrent Streptococcus (Strep) gallolyticus bacteremia without an identifiable source?

Differential Diagnosis for Recurrent Strep Gallolyticus Bacteremia

Single Most Likely Diagnosis

• Colorectal Cancer: Strep gallolyticus (formerly known as Streptococcus bovis biotype I) bacteremia is strongly associated with colorectal cancer. The bacterium is commonly found in the gastrointestinal tract, and its presence in the bloodstream can indicate a breach in the intestinal wall, such as that caused by a tumor.

Other Likely Diagnoses

• Diverticulitis: Inflammation of the diverticula in the colon can lead to bacterial translocation into the bloodstream, causing bacteremia.
• Gastrointestinal Ulcer or Perforation: Similar to colorectal cancer, ulcers or perforations in the gastrointestinal tract can provide a portal of entry for Strep gallolyticus into the bloodstream.
• Prosthetic Valve Endocarditis: Although less common, Strep gallolyticus can cause endocarditis, especially in patients with prosthetic heart valves.

Do Not Miss Diagnoses

• Endocarditis with a Normal-appearing Valve: Even if the patient does not have a prosthetic valve, native valve endocarditis is a potentially life-threatening condition that must be considered.
• Intra-abdominal Abscess: An abscess in the abdominal cavity can be a source of recurrent bacteremia and requires prompt diagnosis and treatment.
• Immunocompromised State: Conditions such as HIV/AIDS, immunosuppressive therapy, or other immunodeficiencies can predispose patients to recurrent infections, including Strep gallolyticus bacteremia.

Rare Diagnoses

• Bacteremia from a Non-gastrointestinal Source: Although less common, Strep gallolyticus can occasionally be found in other parts of the body, such as the skin or urinary tract, and cause bacteremia.
• Gastrointestinal Lymphoma: This is a rare condition that can cause bacterial translocation and bacteremia.
• Other Gastrointestinal Malignancies: While colorectal cancer is the most common association, other gastrointestinal malignancies, such as gastric or small intestine cancer, can also be a source of Strep gallolyticus bacteremia.