Title : Unveiling the uncommon pathogenesis of Streptococcus Gallolyticus subspecies pasteurianus Bacteremia and its link to gastric pathology
Abstract:
Background
While Streptococcus gallolyticus subsp. gallolyticus has a well-known association with colorectal cancer, an epidemiological association between S. gallolyticus subsp. pasteurianus and hepatobiliary diseases has been suggested. Herein, we present a unique case of S. gallolyticus subsp. pasteurianus bacteremia in a patient with a complex medical background, including autoimmune hepatitis, liver cirrhosis, and multiple potential gastrointestinal sources. A detailed gastrointestinal evaluation also revealed a bleeding gastric polyp and colonic tubular adenomas. With evolving understanding of its association with gastrointestinal pathologies beyond colorectal cancer, it opens an intriguing area for future research into its potential link to gastric conditions.
Case presentation
A 73-year-old female with a past medical history of autoimmune hepatitis on azathioprine, chronic anemia, COPD, type 2 diabetes mellitus, paroxysmal atrial fibrillation, and hypertension presented with complaints of left foot swelling for one day, generalized weakness, and back pain for the past two weeks. Approximately one week prior, she was admitted to an outside hospital with similar complaints of back pain. MRI scans of the lumbar spine and pelvis revealed degenerative changes throughout the lumbarspine and possible compressive pathology at the L5 nerve root on the left. Thereafter, she was discharged with pain medications and muscle relaxants.
Upon arrival at our facility, her vital signs were as follows: temperature 37.6°C, heart rate 82, and blood pressure 114/83. Physical examination was notable for a grade 2 systolic murmur over the precordium, erythema and warmth over the lateral aspect of the left foot, and tenderness to palpation. Laboratory results on admission showed a white blood cell count of 6.3, hemoglobin 8.1 g/dL, platelets 251, CRP 9.1 mg/L, proBNP 614 pg/mL, ESR 104 mm/h, and lactate 1.5 mmol/L. Iron studies revealed an iron level of 16 μg/dL, TIBC 202 μg/dL, iron saturation 8%, and ferritin 75 ng/mL suggestive of iron deficiency anemia. The patient was started on IV ceftriaxone every 24 hours for suspected foot cellulitis, and gastrointestinal consultation was requested to evaluate the anemia for possible GI etiology. Blood cultures obtained on admission grew Streptococcus gallolyticus subspecies pasteurianus on both aerobic and anaerobic broths after two days of incubation, and the patient was continued on ceftriaxone 2g every 24 hours per susceptibility testing. A transthoracic echocardiogram revealed a possible vegetation on the anterior mitral valve leaflet and a prior finding of mild mitral valve regurgitation. A transesophageal echocardiogram confirmed the presence of a small vegetation on the posterior mitral valve leaflet, measuring 5 mm x 6 mm near the commissure. The EGD revealed a 10 mm semi-pedunculated hyperplastic polyp with active bleeding in the gastric cardia, which was removed, clipped, and injected with epinephrine. Colonoscopyrevealed seven tubular polyps which were removed. Her repeat blood cultures were negative. While all this was ongoing, the patient continued to have lower back pain which continued to worsen, especially with movement. A repeat MRI of the lumbar spine and pelvis showed findings concerning for L4/L5 discitis with adjacent mild osteomyelitis of L3 and L4, and a small epidural abscess spanning the L4 vertebral body. Due to the need for neurosurgical intervention, she was transferred to a higher-level facility. There, she underwent laminectomy with drainage of the epidural abscess, but the cultures from the abscess did not reveal any growth. Her antibiotic regimen was changed to Penicillin G 24 million units IV daily via continuous infusion to complete a total of six-week course of antibiotics. A repeat TEE, performed 11 days after the prior one, revealed no valvular vegetations. Azathioprine was withheld for the course of her infection.
Conclusion/Discussion
Numerous studies have established a strong association between S. gallolyticus subsp. pasteurianus bacteremia and underlying hepatobiliary disease, as well as, though much less frequently, colonic pathology. Notably, our patient had a long-standing history of liver cirrhosis secondary to autoimmune hepatitis. Immunosuppressive therapy with azathioprine and prednisone could have also played a role.Unlike the well-established link between S. gallolyticus subsp. gallolyticus (formerly bovis biotype I) and colorectal carcinoma, there is limited information on S. gallolyticus subsp. pasteurianus bacteremia and its connection to gastrointestinal pathology. With no specific treatment guidelines available, a colonoscopy is recommended if the source of infection remains unidentified. Apart from association with colorectal carcinoma, a few cases have also reported S. gallolyticus bacteremia originating from other seemingly benign sources, such as cellulitis or colonic adenomas.
In our case, apart from multiple risk factors as discussed above, the potential sources of infection could
include intestinal adenomas or a bleeding gastric polyp. Existing literature primarily focuses on the
association with colonic pathology, and there is no documented link between gastric polyps and S.
gallolyticus bacteremia. This presents an intriguing area for further research and exploration to better
understand potential associations with gastric pathologies. The need for upper GI endoscopy apart from
thorough colonic and hepatobiliary–pancreatic assessment should also be considered in appropriate
clinical settings.
