Bloodstream Infection and Colorectal Cancer Risk in Queensland Australia, 2000-2019

Bloodstream infections may occur as a complication of colorectal cancer or be a marker for its occult presence. The objectives of this study were to quantify the overall and etiology-specific risks for incident colorectal cancer-associated bloodstream infection.

Population-based surveillance for community-onset bloodstream infection was conducted among adults aged 20 years and older in Queensland, Australia between 2000 and 2019. Statewide databases were used to identify patients with incident colorectal cancer and collect clinical and outcome information.

After exclusion of 1794 patients with prior colorectal cancer, a cohort of 84,754 patients was assembled, of which 1030 had colorectal cancer-associated bloodstream infection and 83,724 had no colorectal cancer. Bloodstream infection was associated with a 16-fold annualized increased risk for diagnosis of colorectal cancer (incidence rate ratio 16.1; 95% confidence interval [CI], 15.1-17.1) in the adult population. Patients who had colorectal cancer-associated bloodstream infection were more likely to be older and male, have hospital-onset and polymicrobial infections, and have fewer non-cancer-related comorbidities. The organisms associated with highest risk for colorectal cancer included Clostridium species (relative risk [RR] 6.1; 95% CI, 4.7-7.9); especially C. septicum (RR 25.0; 95% CI, 16.9-35.7), Bacteroides species (RR 4.7; 95% CI, 3.8-5.8); especially B. ovatus (RR 11.8; 95% CI, 2.4-34.5), Gemella species (RR 6.5; 95% CI, 3.0-12.5), Streptococcus bovis group (RR 4.4; 95% CI, 2.7-6.8); especially S. infantarius subsp. coli (RR 10.6; 95% CI, 2.9-27.3), Streptococcus anginosus group (RR 1.9; 95% CI, 1.3-2.7), and Enterococcus species (RR 1.4; 95% CI, 1.1-1.8).

Although much attention has been afforded to S. bovis group over the past decades, there are many other isolates associated with higher risk for colorectal cancer-associated bloodstream infections.