Case Presentation:

An 88 year old man with a history of severe aortic stenosis with transcatheter aortic valve replacement and unprovoked pulmonary embolism (on lifetime warfarin) presented with four days of lethargy and weakness. He denied any fevers, chills, abdominal pain, diarrhea, or urinary symptoms. He was compliant with scheduled dental cleanings and took prophylactic antibiotics during a visit six months prior. Vitals were temperature 97.4°F, blood pressure 99/67, pulse 55, respirations 17, and O2 saturation 98% on room air. Physical exam demonstrated a soft 2/6 systolic ejection murmur at the right upper sternal border and a benign abdomen without palpable masses. Rectal exam showed hemorrhoids. Stool was positive for occult blood. Pertinent labs included white blood cell count 6.1 K/µL, hemoglobin 11.4 g/dL (from 13.6 two months prior), iron 20 ug/dL, iron saturation 10%, ferritin 81 ng/mL, and international normalized ratio 3.8. Blood cultures were positive for Streptococcus sanguinis in 4/4 bottles. Transthoracic echocardiogram demonstrated no macroscopic vegetations. Transesophageal echocardiogram was not performed due to the patient’s comorbidities. The patient was empirically treated for endocarditis with intravenous penicillin and gentamycin given his artificial valve. Further investigation for the source of bacteremia included a positron emission tomography (PET) scan showing increased metabolic uptake in the descending colon and rectum. Subsequent colonoscopy revealed two large polyps in the ascending and sigmoid colon consistent with tubular adenomas. The patient was discharged home to complete six weeks of intravenous antibiotics. However, he was quickly re-admitted with hematochezia with hemoglobin drop to 7.3 g/dL. Repeat colonoscopy revealed a four-centimeter pre-malignant rectal mass. After the patient’s bleeding resolved off anticoagulation, he was discharged to continue outpatient treatment for endocarditis.


Discovery of gastrointestinal (GI) neoplasms is occasionally preceded by bacteremia. Although the association between Streptococcus bovis and colonic malignancy is well-described, other streptococcal species are common colonic commensals and have been linked to occult GI tumors in case reports. Seven cases of S. sanguinis bacteremia associated with occult gastrointestinal malignancy have been previously reported. While S. sanguinis is commonly isolated from gingival crevices, it may occasionally be isolated from colonic mucosa. Prior case series reveal both oral and colonic sites seed S. sanguinis bacteremia with roughly equal frequency, and some cases initially attributed to gingival inflammation were subsequently revealed to be secondary to advanced carcinoma. By disrupting intestinal mucosa, GI neoplasms may facilitate translocation of bacteria into the blood.


Our observations, in combination with other reported cases, indicate internists should seriously consider potential underlying GI neoplasm in any patient who develops S. viridans bacteremia without clear etiology after routine workup.