Clinical Importance of Streptococcus gallolyticus infection among colorectal cancer patients: systematic review and meta-analysis.

BACKGROUND: Streptococcus bovis has long been associated with colorectal cancer (CRC). However, not all genospecies are as closely related to CRC. With this systematic review, we aim to increase the awareness of the association between S. bovis biotype I (Streptococcus gallolyticus) and CRC and urge for uniform molecular microbiological classification. METHODS: In January 2011, the PubMed database was searched for all studies that investigated the association between S. bovis, infective endocarditis (IE), and CRC. A total of 191 studies were screened for eligibility and yielded 52 case reports and 31 case series, of which 11 were used for meta-analysis on the association between S. bovis biotype, IE, and adenomas/carcinomas (CRC). RESULTS: Among the S. bovis-infected patients who underwent colonic evaluation, the median percentage of patients who had concomitant adenomas/carcinomas was 60% (interquartile range, 22%), which largely exceeds the disease rate reported in the general asymptomatic population. Meta-analysis showed that patients with S. bovis biotype I infection had a strongly increased risk of having CRC (pooled odds ratio [OR], 7.26; 95% confidence interval [CI], 3.94-13.36) and IE (pooled OR, 16.61; 95% CI, 8.85-31.16), compared with S. bovis biotype II-infected patients. Notably, CRC occurred more often among patients with S. bovis IE than among patients with S. bovis infection at other sites (pooled OR, 3.72; 95% CI, 2.03-6.81). CONCLUSIONS: Our meta-analysis clearly indicates that S. bovis should no longer be regarded as a single species in clinical practice, because S. gallolyticus (S. bovis biotype I) infection, in particular, has an unambiguous association with CRC.