The relationship between the new taxonomy of Streptococcus bovis and its clonality to colon cancer, endocarditis, and biliary disease.

ABSTRACT

BACKGROUND: The nomenclature of Streptococcus bovis has changed. The study aims were to examine and compare the clinical characteristics and outcomes of infections based on the new taxonomy and the genetic relatedness of strains. METHODS: Bacteremic cases from 2004 to 2010 at Assaf Harofeh Medical Center were reviewed. VITEK 2 later confirmed with polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was used for subspecies identification. VITEK 2 later confirmed with Etests was used for minimal inhibitory concentration (MIC) testing. Repetitive extragenic palindromic polymerase chain reaction (rep-PCR) was used to determine the genetic relatedness of strains. RESULTS: Twenty-four bacteremia cases were included. The median age of patients was 81 years (range 1 day to 91 years), two were neonates, three were pregnant, and 18 were elderly (≥ 65 years of age). The Charlson's combined conditional age-related score was 8.2 ± 2.9, and 11 (58 %) patients were immunosuppressed. There were 13 patients who had S. gallolyticus subsp. pasteurianus, six had S. gallolyticus subsp. gallolyticus, four had S. infantarius subsp. coli, and one had S. infantarius subsp. infantarius. Ten of 19 non-pregnant adult patients had colon adenoma or carcinoma, three had acute biliary disease, and five had endocarditis. Two patients died in the hospital. rep-PCR revealed polyclonality. There were no significant associations between subspecies or genotypes and the various clinical characteristics or outcomes. CONCLUSION: S. bovis bacteremia is a serious disease that affects elderly immunosuppressed individuals. Infection is strongly associated with colon pathology and endocarditis, regardless of the new taxonomy or clone complex. The identification of S. bovis is of paramount importance, and microbiology laboratories should differentiate its processing from that of other S. viridans.