Streptococcus mitisStrains Causing Severe Clinical Disease in Cancer Patients

• DOI: 10.3201/eid2005.130953
• Publication Date: 2014-03-26T18:03:55Z
• Authors: Samuel A. Shelburne; Pranoti Sahasrabh...; Miguel Saldana; Hui Yao; Xiaoping Su; Nicola Horstmann; Erika Thompson; Anthony R. Flores
• Keywords: 0301 basic medicine; Bacteremia; Streptococcus mitis; Infectious and parasitic diseases; RC109-216; Severity of Illness Index; Cohort Studies; Mice; 03 medical and health sciences; Neoplasms; Streptococcal Infections; neutropenia; Animals; Humans; bacteremia; Phylogeny; 0303 health sciences; Genes, Essential; Virulence; Research; R; viridans group streptococci; 3. Good health; Pitt bacteremia score; Disease Models, Animal; Genes, Bacterial; 13. Climate action; Medicine; Female; cancer patients; Genome, Bacterial; Multilocus Sequence Typing

The genetically diverse viridans group streptococci (VGS) are increasingly recognized as the cause of a variety of human diseases. We used a recently developed multilocus sequence analysis scheme to define the species of 118 unique VGS strains causing bacteremia in patients with cancer; Streptococcus mitis (68 patients) and S. oralis (22 patients) were the most frequently identified strains. Compared with patients infected with non-S. mitis strains, patients infected with S. mitis strains were more likely to have moderate or severe clinical disease (e.g., VGS shock syndrome). Combined with the sequence data, whole-genome analyses showed that S. mitis strains may more precisely be considered as >2 species. Furthermore, we found that multiple S. mitis strains induced disease in neutropenic mice in a dose-dependent fashion. Our data define the prominent clinical effect of the group of organisms currently classified as S. mitis and lay the groundwork for increased understanding of this understudied pathogen.