Case Presentation: This is a 58 year old male with a past medical history of MDD, GAD, history of polysubstance abuse, history of enterococcus bacteremia complicated by aortic valve endocarditis status post valvular replacement and hemorrhagic stroke who was admitted to the hospital for urosepsis. Of note, this patient was previously hospitalized for Lactobacillus bacteremia presumably associated with a dental procedure performed just prior to his presentation. He had received a PICC and was planned to receive a total of 8 weeks of intravenous ampicillin. However, the patient refused to complete the full 8 weeks and had his PICC removed after only 7 weeks of intravenous antibiotics. On physical exam, patient had BP of 98/58 with a heart rate of 90bpm. Temperature was 98F. Patient was in mild distress, pale with conjunctival pallor, and lethargic. Cardiovascular exam revealed a 4/6 systolic murmur heard best at the right sternal border. The remainder of the exam was benign. There were no focal neurologic deficits. He had no skin rash or lesions. Patient was anemic with a Hgb of 10.0 and had a WBC count of 7.76. Lactate was 1.6. Blood cultures grew Lactobacillus casei.On CT imaging of abdomen/pelvis, patient was found to have a mycotic superior mesenteric aortic aneurysm as seen on CT imaging. He subsequently underwent a TTE/TEE which revealed a thickened aortic valve with worsening aortic stenosis, suspicious for endocarditis. CT surgery was consulted who performed a resection of the aneurysm. Patient was discharged with a PICC and a plan to complete 6 weeks of intravenous ampicillin.
Discussion: Lactobacillus casei is a common component of modern probiotics. In recent years, probiotics have grown in popularity, both in the public and in study of C. diff treatment and prophylaxis. To date, there is little evidence to suggest a relationship between the increased use of probiotics and Lactobacillus bacteremia. Because Lactobacillus exists in the GI flora, even patients positive for Lactobacillus bacteremia who are taking probiotics may have a natural alternative source of infection. The mechanism by which Lactobacillus infect human hosts has not been widely studied. In one case report, a patient with indolent continuous L. casei bacteremia had presented with a sudden onset of thoracic pain due to an aortic arch dissection. The suggested mechanism is that Lactobacillus is able to survive and colonize vascular surfaces, with the possible formation of biofilm. This results in penetration of vascular walls and development of dissections and aneurysms. In addition, members of the Lactobacillus genus have been shown to produce arylamidases that function like human Factor Xa. This would presumably allow them to promote platelet activation and generation of thrombi to which they could adhere.
Conclusions: Lactobacillus bacteremia is rare but rising in incidence and gaining increasing attention. Lactobacillus promotes platelet activation and intravascular coagulation, and it can also form biofilms. These characteristics give it increased ability to infect vascular architecture, causing endocarditis and aneurysms. One should therefore be aware of the potential vascular complications associated with lactobacillus bacteremia.