Boleij A. Clin Infect Dis. 2011;53:870-878.
Streptococcus bovis should no longer be regarded
as a single species in clinical practice because only S. bovis biotype
I, or S. gallolyticus infection, has an explicit association with
colorectal cancer, according to researchers from the Netherlands.
“Our data show that S. gallolyticus
infection has a significant association with colonic adenomas and
carcinomas,” Harold Tjalsma, PhD, of the Radboud University
Nijmegen Medical Center in the Netherlands, told Infectious Disease
News. “This association is surprisingly lower for the closely related
bacterium S. infantarius. As both species were often classified as S.
bovis, one can imagine that the overall association between S. bovis
and colorectal cancer has systematically been underestimated. With this study,
we want to emphasize that proper and consistent microbial classification is
crucial to understand the full impact of these bacterial infections in
colorectal cancer patients.”
Annemarie Boleij, Msc, and other colleagues from
Tjalsma’s group conducted a systematic review of all studies that assessed
the association between S. bovis, infective endocarditis and
colorectal cancer. A search of the PubMed database revealed 52 case reports and
31 case series; 11 of which were used for meta-analysis on the association
between S. bovis biotype, infective endocarditis and adenomas or
Of the S. bovis-infected patients who underwent
colonic evaluation, 60% of patients (interquartile range [IQR], 22%) had
concomitant adenomas or carcinomas. “This significantly exceeds the
disease rate reported in the general asymptomatic population,” the
Compared with S. bovis biotype II-infected
patients, those with S. bovis biotype I had a significantly increased
risk for colorectal cancer (OR=7.26; 95% CI, 3.94-13.36) and infective
endocarditis (OR=16.61; 95% CI, 8.85-31.16). Colorectal cancer was more common
among those with S. bovis infective endocarditis vs. those with S.
bovis-infection elsewhere (OR=3.72; 95% CI, 2.03-6.81).
“Our study advocates full bowel examination in all
patients who are diagnosed with S. gallolyticus infection, and
clinicians should be aware of this new nomenclature,” Tjalsma said.
“Furthermore, we hope that our study stimulates clinical microbiology labs
to perform additional subtyping when a S. bovis strain has been found.
To fully exploit the presence of S. gallolyticus as intestinal biosensor
for colorectal cancer, molecular tools need to be established to accurately
monitor subclinical infections of this bacterium. Eventually, novel S.
gallolyticus-based assays may be implemented in colorectal cancer screening
programs aid in early detection, which is crucial in the battle against this
disease.” – by Ashley DeNyse
Disclosure: This work was supported by the Dutch
Cancer Society (KWF; project KUN 2006-3591 to A. B.).