Anaerobic gram-negative rod bacteremia as a marker of gastrointestinal cancer in Japanese patients: a single-center retrospective study.

Background: Gram-negative rod (GNR) bacteremia has been suggested as a clinical marker of occult cancer; however, no studies are available in this regard in the Japanese population. Here, we investigated the risk factors for gastrointestinal cancer with GNR bacteremia.

Methods: Patients with GNR bacteremia admitted to St. Luke's International Hospital between January 2011 and July 2021 were included. The clinical data of patients with and without cancer, 1 year before and after GNR bacteremia diagnosis, were compared. Univariate analysis was performed using χ2 and Fisher's exact tests for categorical variables and the Mann-Whitney U test for continuous variables, while multivariable analysis was performed using logistic regression analysis, and a P of <0.05 was considered statistically significant.

Results: Of 2,296 GNR bacteremia-positive patients, 96 were associated with gastrointestinal cancer, and univariate analysis showed significant differences between the gastrointestinal cancer and comparison groups in terms of mean body mass index (BMI; 20.5 vs. 21.8 kg/m2), Enterobacterales detection (64.6% vs. 81.3%), and anaerobic GNR detection (24.0% vs. 8.5%). Thirty-five (36%) and 61 (64%) patients had upper and lower gastrointestinal cancer, respectively. There were 23 patients with anaerobic GNR bacteremia related to 24 strains (upper and lower gastrointestinal cancer, 5 and 18 cases, respectively). Multivariate analysis identified anaerobic GNR [odds ratio, 3.440; 95% confidence interval (CI): 2.085-5.675, P<0.001] as a significant risk factor for cancer.

Conclusions: Anaerobic GNR in blood cultures may be a risk factor for gastrointestinal cancer. Therefore, it is necessary consider cancer workup, such as endoscopy, for patients with anaerobic GNR bacteremia.