Natto intake is a risk factor of Bacillus subtilis bacteremia among children undergoing chemotherapy for childhood cancer: A case-control study

Abstract

BackgroundNatto, a popular, daily food in Japan, is made from soybeans fermented by Bacillus subtilis. The aim of this retrospective case-control study (matched 1: 4) is to determine whether natto intake is a risk factor of B. subtilis bacteremia in this population. MethodsThe retrospective, matched case-control study was conducted at Tokyo Metropolitan Children's Medical Center between April 2012 and June 2020 and included pediatric patients younger than 15 years who received chemotherapy for cancer. Patients who received hematopoietic stem cell transplantation were excluded. Patients with B. subtilis bacteremia were compared with controls matched for age and underlying diseases. Dietary information within seven days from the date of blood culture collection was extracted from medical records. Multivariate logistic regression was performed to define the risk factors of B. subtilis bacteremia. ResultsIn total, 23 patients with B. subtilis bacteremia were identified and matched to 92 controls. The percentage of patients and controls who ingested natto within seven days from the date of blood culture collection was 78% and 50%, respectively. On univariate analysis, the odds ratio of natto intake for B. subtilis bacteremia was 3.6 (95% confidence interval [CI]: 1.2–10.5). Multivariable logistic regression tests after controlling for neutropenia revealed that B. subtilis bacteremia was associated significantly with natto intake at odds ratio 3.3 (95% CI: 1.1–9.6). ConclusionNatto intake was associated with B. subtilis bacteremia during chemotherapy for childhood cancer.