Investigation on the regulatory roles of a second messenger cyclic diadenosine-monophosphate (C-DI-AMP) in streptococcus gallolyticus subsp. gallolyticus

Abstract

Chapter 1 -Introduction 1.1 Background information Streptococcus gallolyticus subsp. gallolyticus, a Lancefield Group D Streptococcus, is an emerging opportunistic pathogen. It is one of the gut microbiota members present in 2.5 to 15% of healthy individuals (1). Upon entering into bloodstream, S. gallolyticus subsp. gallolyticus can colonise damaged heart valves, causing infective endocarditis. S. gallolyticus subsp. gallolyticus infections can represent up to 25% of all infective endocarditis cases (2). S. gallolyticus subsp. gallolyticus was previously known as S. bovis biotype I, a traditional nomenclature that has been replaced with a system that clearly differentiate S. gallolyticus at the subspecies level. The renaming of S. bovis is clinically important. Unlike S. infantarius subsp. coli (biotype II.1) and S. gallolyticus subsp. pasteurianus (biotype II.2), S. gallolyticus subsp. gallolyticus is the specific S. gallolyticus that exhibits a strong association with the incidence of colorectal cancer among the endocarditis patients infected with S. gallolyticus (3-6). The significant enrichment of S. gallolyticus subsp. gallolyticus in the stools of these patients was reported as early as in 1951, and subsequently supported by many case reports and systemic reviews (1, 6-10). Due to the strong association of S. gallolyticus subsp. gallolyticus with colorectal cancer, UptoDate database currently lists a follow up colonoscopy as a strong medical recommendation for the endocarditis patients infected with S. gallolyticus.