Recurrent Bacillus subtilis Var. Natto Bacteremia and Review of the Literature on Bacillus subtilis: The First Case Report

Abstract

BACKGROUND Fermented foods, such as yogurt, are often considered healthy; however, there have been numerous reported cases of bacteremia associated with their consumption. In this report, we present a case of Bacillus subtilis var. natto (B. subtilis var. natto) bacteremia related to the consumption of natto, a traditional Japanese food made from fermented soybeans. We also conducted a literature review on B. subtilis bacteremia. CASE REPORT We report the case of a 41-year-old woman who presented with fever, had a medical history of congenital liver fibrosis, and experienced recurrent B. subtilis var. natto bacteremia along with acute cholangitis. Although she discontinued eating natto, she developed pyogenic thrombophlebitis due to B. subtilis var. natto. We successfully treated her with meropenem and an anti-coagulant. To investigate the management and prognosis of B. subtilis var. natto bacteremia, we conducted a literature review of B. subtilis intra-abdominal infection. We identified 17 papers describing 30 cases of B. subtilis intra-abdominal infection, 4 cases of which were caused by B. subtilis var. natto; the median age of the patients was 71 years (range, 15-96 years), 14 patients (47%) were female, and 3 patients (10%) died. From our findings, our case was the only one of recurrent B. subtilis var. natto infection. Even after patients discontinue eating natto, they should be carefully monitored. CONCLUSIONS Due to advancements in PCR identification techniques, case reports of infections caused by B. subtilis var. natto are increasing.

Figure 1.

Abdominal computed tomography showing a superior mesenteric vein thrombus in the portal vein, with mesenteric panniculitis and numerous collateral blood vessels (A: coronal axis), and dilatation of the common bile duct (B: horizontal axis). A septic thrombophlebitis of the portal vein on admission (C: red arrow) disappeared after 9 months of anticoagulation (D: red arrow).

Figure 2.

(A, B) Colony of the B. subtilis in the blood agar gel.

Figure 3.

Genetic analysis results showing that the isolates of our specimens Bacillus subtiliis var. natto and Bacillus subtilis subsp. subtilis were homologous to the sequence of BioF (A) and BioW (B).

Figure 4.

Review process of the Bacillus subtilis-related intra-abdominal infection.

Figure 5.

Number of published cases and articles according to year.