This study was intended to delineate the association between digestive tract malignancies and bacteraemia due to Streptococcus gallolyticus subspecies pasteurianus.

We reviewed the medical records and microbiological results of patients with bacteraemia due to Streptococcus bovis during the period 2000–2012. Species and subspecies identification of isolates originally classified as S. bovis was confirmed by 16S rRNA sequencing and PCR restriction fragment length polymorphism (PCR-RFLP) assays. Minimum inhibitory concentrations of antimicrobial agents were determined by the broth microdilution method.

Of the 172 S. bovis complex isolates obtained from 172 patients (age range, <1–94 years, median age, 66) with bacteraemia, 31 isolates were identified to be S. gallolyticus subspecies gallolyticus, 126 were S. gallolyticus subspecies pasteurianus, and 15 were shown to be Streptococcus infantarius. The majority (n = 104, 60%) of patients were male and had underlying malignancies (n = 87, 51%). Bacteraemia due to S. gallolyticus subspecies gallolyticus was significantly associated with endocarditis while S. gallolyticus subspecies pasteurianus was more likely to be associated with malignancies of the digestive tract, including gastric, pancreatic, hepatobiliary and colorectal cancers. Septic shock at presentation was the only factor associated with mortality among patients with bacteraemia due to either subspecies of S. bovis. Isolates of S. gallolyticus subspecies pasteurianus had higher rates of resistance to macrolides and clindamycin than isolates of S. gallolyticus subspecies gallolyticus.

Extensive diagnostic work-up for digestive tract malignancies and trans-esophageal echocardiogram should be investigated in patients with bacteraemia caused by S. gallolyticus.