Streptococcus viridians bacteraemia and colonic adenocarcinoma

Abstract

Even though Streptococcus bacteraemia is an infrequent presentation of colonic malignancies, there is a well-established link between Streptococcus bovis bacteraemia and colonic malignancies. Most of the physicians are well aware of this correlation and further workup is pursued in most of the cases. However, many physicians may not be aware that other species of Streptococcus viridians, other than S. bovis, can be associated with colonic malignancies. In this case report, we present a case of Streptococcus viridians (anginosus) bacteraemia as a complication of an undiagnosed sigmoid adenocarcinoma. While further evidence is needed to warrant a gastrointestinal (GI) workup in a patient with other species of Streptococcus viridians bacteraemia, we would like to increase the awareness in the physicians’ community regarding Streptococcus viridians, other than S. bovis bacteraemia. This would be especially relevant for patients who have no GI screening, as Streptococcus viridians bacteraemia can be an early sign of colonic neoplasm.

Background

Over the years, there has been growing evidence supporting the relationship between Streptococcus bovis and colonic malignancies.^{1 2} The scope of the evidence is also expanding in the association with other gastrointestinal neoplasms and liver disease.^{3 4} Getting a colonoscopy after a S. bovis bacteraemia is the standard of care at this point. The focus of this case report will be on other species of Streptococcus viridians. With the exception of sporadic case reports published in different journals, including some literature review, a direct correlation is not yet well established between Streptococcus viridians, other than S. bovis and colonic malignancies. Although there might be a link between the two entities, since a proved correlation is not yet established, many doctors are not aware of this possibility.

Case presentation

The patient is a 73-year-old man with a medical history of hypertension, hyperlipidaemia and recently diagnosed atrial fibrillation (on warfarin), who presented with recurrent gastrointestinal bleed. The patient was discharged from hospital 1 week ago. At the previous admission, he was hospitalised for Streptococcus viridians (anginosus) bacteraemia, anaemia, gastrointestinal bleeding and new onset atrial fibrillation. During that presentation, the patient had a temperature of 103.7 degree Fahrenheit, heart rate 135 beats per minute, blood pressure 135/72 mm/Hg, respiratory rate 20 breaths per minute and oxygen saturation 94% on room air. The patient was pale and tachycardic. The abdomen was non-tender, but mildly distended. There was no hepatosplenomegaly and no palpable mass. Rectal examination revealed no mass, but it was guaiac positive. Haemoglobin and haematocrit were 8 and 24.9, respectively, and leucocytes were 10 000 with 78% neutrophils and 16% bands. Urinalysis and chest X-ray were negative. CT of the abdomen and pelvis showed non-specific focal thickening of sigmoid colon, likely in the setting of infectious/inflammatory entities, based on radiology report. No abscess or fluid collection noted. At that time, Streptococcus viridians (anginosus) sensitive to penicillin grew in the blood cultures. Transthoracic and transoesophageal echocardiography showed no vegetation. Even though the patient had bacteraemia with a microorganism known to cause infective endocarditis, he did not meet Duke criteria to make that diagnosis. Surveillance blood cultures also came out negative. No clear source of bacteraemia was found at that time, but given the findings on abdominal CT and poor dentition, it would most likely be in the intestine or oral cavity. Regarding anaemia and gastrointestinal bleeding, the patient had oesophagogastroduodenoscopy that showed gastric ulcers, for which the patient received proton pump inhibitor. Immunostaining for Helicobacter pylori was negative and biopsy was negative for malignant cells. Regarding atrial fibrillation, the patient was started on warfarin. The patient was discharged on treatment with penicillin and was instructed to follow-up with the gastroenterologist (colonoscopy) and dental workup.

The patient was readmitted for gastrointestinal bleeding 1 week after discharge. On the second admission the patient's blood pressure was 119/65 mm/Hg, heart rate 81 beats per minute, respiratory rate 18 breaths per minute, oxygen saturation of 96% on room air with a temperature of 99.2 degree Fahrenheit. The physical examination revealed mild pallor. The abdomen was soft non-tender, mildly distended and with hyperactive bowel sounds. No rebound, guarding or rigidity was noted. Digital rectal examination was grossly bloody.

His laboratory data showed that haemoglobin and haematocrit were 8.5 and 26.1, respectively, and no leukocytosis or left shift. Oesophagogastroduodenoscopy on the previous admission showed healing gastric ulcers, but no active bleeding. Since the digital rectal examination showed bright red blood, colonoscopy was pursued. The patient developed obstruction during the preparation. CT of the abdomen showed possible colonic pneumatosis and colonoscopy was abandoned at that time. Barium enema showed apple core lesion, suspicious of neoplasm at the level of distal sigmoid (figures 1 and 2). Endoscopy showed an obstructing mass at the level of sigmoid colon (figures 3 and 4). A stent was placed through the mass to relieve the obstruction. No samples were taken during the sigmoidoscopy, but macroscopic appearance was consistent with malignant lesion. Tumour markers showed a carcinoembryonic antigen level of 31.3. The patient was taken to the operating room and had a sigmoid colectomy with a descending end colostomy. Surgical pathology/cytology report showed invasive colonic adenocarcinoma.

Figure 1.

Apple core lesion at the sigmoid colon.

Figure 2.

Apple core lesion at the sigmoid colon.

Figure 3.

Mass at the level of the sigmoid colon.

Figure 4.

Mass at the level of the sigmoid colon.

After the discharge, he has been followed by a haematology–oncology specialist for stage II T3 N0 colon cancer. He is feeling better and gaining weight.

Discussion

Since the first article in 1951¹ that suggested a correlation between S. bovis and colonic neoplasm, there has been growing evidence that established this correlation, identified both on clinical^2–4 and laboratory studies.^5–7

While for S. bovis there is enough evidence to pursue further workup, in a case of bacteraemia there is not yet a direct link between other species of Streptococcus viridians bacteraemia and colonic neoplasm with the exception of sporadic case reports like this one. Streptococcus viridians is a group of α-haemolytic or non-haemolytic streptococci found mostly in the oral cavity and gastrointestinal (GI) tract. S. bovis is part of this group as well. Streptococcus viridians usually have low virulence and would not cause sepsis unless there is some impaired immunity on the background and there is damage of the integrity of mucosa.

In the case above the Streptococcus viridians (anginosus) bacteraemia seems to be an early signs of colonic neoplasm. As mentioned previously, there have been case reports that hint towards a correlation between species of Streptococcus viridians other than bovis, with colonic neoplasms.^8–15 Even with these case reports, there has not been enough evidence to include a routine workup for colonic neoplasm in a patient with Streptococcus viridians bacteraemia, other than S. bovis, for which there is a well-established link. Furthermore, there are no definite studies to evaluate if proteins related with other species of Streptococcus viridians have any effect on carcinogenesis or angiogenesis. While further evidence is needed to warrant a GI workup in a patient with Streptococcus viridians bacteraemia other than bovis, we would like to increase the awareness in the physicians’ community regarding unexplained bacteraemia due to other species of Streptococcus viridians. This would be especially relevant for patients who have no GI screening, as Streptococcus viridians bacteraemia can be an early sign of colonic neoplasm. In the case above, the patient had Streptococcus anginosus bacteraemia, which despite being part of Streptococcus viridians group, is mostly associated with abscess formation, rather than infective endocarditis.

Learning points.

• In the case of unexplained bacteraemia thorough workup is needed to identify the source.

• Physicians need to be aware that Streptococcus viridians, other than Streptococcus bovis, bacteraemia can be an early sign of colonic neoplasm.

• Gastrointestinal workup may be warrantied in certain cases of Streptococcus viridians bacteraemia, other than bovis, as it can reveal colonic neoplasm.

• Identification of microorganism at the level of species it is very helpful, since it gives you clues towards the complications and associations.

• In case of iron deficiency anaemia both upper and lower endoscopy should be performed, even in the case when upper endoscopy has revealed a source, since other sources can be missed.