Laboratory identification and clinical characteristics of Streptococcus bovis/Streptococcus equinus complex bacteremia: a retrospective, multicenter study in Hiroshima, Japan

Abstract

Background Bacteremia due to the Streptococcus bovis/Streptococcus equinus complex (SBSEC) is associated with specific diseases, such as colorectal cancer and infective endocarditis. This study aimed to evaluate the clinical characteristics of SBSEC bacteremia and the accuracy of identification of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and phenotypic identification systems for SBSEC isolates. Methods We analyzed patients with SBSEC bacteremia retrospectively between 2012 and 2019 at three hospitals in Japan. We re-identified each SBSEC isolate using sequencing superoxide dismutase (sodA) analysis, MALDI-TOF MS using the MALDI Biotyper, and phenotypic identification using the VITEK2. Results During the study period, 39 patients with SBSEC bacteremia were identified. S. gallolyticus subsp. pasteurianus (SGSP, n = 29), S. gallolyticus subsp. gallolyticus (SGSG, n = 5), S. lutetiensis (SL, n = 4), and S. infantarius subsp. infantarius (n = 1) were identified using sodA sequencing analysis. Primary bacteremia (36%) was the most common cause of bacteremia, followed by infective endocarditis (26%) and biliary tract infections (23%). Colorectal cancer was associated significantly with SGSG bacteremia, while the sources of bacteremia were similar in each SBSEC subspecies. The MALDI Biotyper was significantly more accurate in identifying the SBSEC isolates at the subspecies level compared to the VITEK2 (92% vs. 67%, P = 0.010). In contrast, there were no significant differences in the rates of correct identification of the SBSEC isolates at the species level between the MALDI Biotyper and the VITEK2 (100% vs. 87%, P = 0.055). Conclusions Bacteremia with SGSG was associated with colorectal cancer, and the sources of bacteremia were similar in each SBSEC subspecies. The MALDI-TOF MS was significantly more accurate in identifying SBSEC isolates at the subspecies level than the phenotypic identification systems. The accurate identification of SBSEC isolates using the MALDI-TOF MS and phenotypic identification systems was sufficient at the species level, but it was insufficient at the subspecies level. Therefore, it may be reasonable for clinicians to perform echocardiographies and colonoscopies in all patients with SBSEC bacteremia.

A Rare Case of Meningitis Caused by <i>Streptococcus gallolyticus</i> subsp. <i>pasteurianus</i> in an Immunocompetent Young Adult

“…Although there is known to be a difference in the background factors of the infection between Sgp and Sgg, Sgp infection seems to be more closely associated with pancreatic cancer, chronic liver damage, diabetes mellitus, and meningitis. In contrast, the association of Sgp with infectious endocarditis and colorectal cancer seems to be weaker than that of Sgg infection (7)(8)(9)(10)(11)(12)(13). Strongyloidiasis is another coexisting condition in S. gallolyticus infection.…”

“…Furthermore, we extensively searched for papers concerning retrospective analyses summarizing S. gallolyticus infection and found five reports of cases coming from Japan ( 11 ), China ( 9 ), India ( 10 ), Denmark ( 12 ), and Spain ( 8 ). While S. gallolyticus causes a variety of disease conditions, meningitis caused by this strain was described in only one case report from China, in which the subspecies was Sgp ( 9 ).…”

“…gallolyticus accounts for 5%-10% of the intestinal flora in normal adults (4). Previous studies have shown that S. gallolyticus infection is associated with a range of clinical presentations, including meningitis, bacteremia, infective endocarditis, colorectal cancer, chronic liver disease, and diabetes mellitus (7)(8)(9)(10)(11). There have been many publications concerning this strain; however, reports on subspecies other than Sgp and Sgg are scarce.…”

“…Previously, meningitis caused by S. bovis/SBSEC was reported as S. bovis meningitis, but recently, several papers described the subspecies of S. bovis/SBSEC (3,(8)(9)(10)(11)(12). In a retrospective analysis of the Dutch cohort of adults with community-acquired meningitis (3), S. gallolyticus was very infrequently identified, being found in only 5 of 1,561 cases (0.3%).…”

Bacterial Involvement in Progression and Metastasis of Colorectal Neoplasia

“…Streptococcus bovis ( S. bovis ) is a species of Gram-positive bacteria commonly associated with infective endocarditis [ 142 ] and bacteremia in humans [ 143 ]. It has been reclassified as S. gallolyticus.…”