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Gene sequence analysis methods, including 16S rRNA identification, allows accurate identification of Streptococcus species, which include phenotypically closely related species that are difficult to differentiate using conventional chemical methods. We report a case of bacteremia due to Streptococcus tigurinus , identified by 16S rRNA, in a 72-year-old woman with gastrointestinal cancer and ascites. She was hospitalized to undergo elective tumor-related surgery. Five days prior to undergoing surgery, she developed a fever with no obvious source of infection. Blood cultures identified gram-positive cocci. The patient's bacteremia was initially thought to be caused by an Enterococcus species, given her underlying gastrointestinal disease. However, alpha-hemolytic, mucoid, circular colonies were observed on sheep blood agar the following day. Although matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and biochemical testing suggested Streptococcus pneumoniae , we conducted further investigation to identify the bacterium, as the patient had no symptoms of infections usually related with S. pneumoniae such as pneumonia, meningitis, or sinusitis, and the bacteremia occurred 30 days after hospitalization. Finally, the gram-positive cocci were identified as S. tigurinus , assigned to the Streptococcus mitis group in 2012. Although the origin of infection was unclear, it was suspected that peritonitis or bacterial translocation from the gastrointestinal tract caused the bacteremia. This novel species was recently reported as being extremely pathogenic and different from other Streptococcus species. It has been reported to occur in cases of infectious endocarditis and bacteremia. In this article, we reviewed previous reports of S. tigurinus infection and summarized the clinical and pathogenetic features. [ABSTRACT FROM AUTHOR]

Among the Citrobacter genus, the most commonly isolated bacteria from human specimens are Citrobacter freundii and Citrobacter koseri , and previous cases of infection due to Citrobacter braakii have been rarely reported. We present a case of bacteremia due to C. braakii in a 38-year-old woman with cervical cancer. She was admitted to our hospital with complaints of a fever, chills, and nausea. Blood culture results showed gram-negative bacilli identified as C. braakii via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis, although biochemical testing findings were suggestive of C. freundii . Since a rare pathogen was detected in the present case and the results of additional biochemical studies were suggestive of both C. braakii and Citrobacter farmeri , genetic analysis was conducted. Finally, the gram-negative bacilli were confirmed as C. braakii , a member of the C. freundii complex since 1993, by 16S ribosomal RNA gene sequencing analysis. The gastrointestinal tract was considered the portal of entry, because the patient had a rectal fistula and other cultures such as urine and vaginal discharge incubated species other than C. braakii . The patient recovered after receiving treatment with ciprofloxacin for 14 days. The epidemiology and clinical characteristics of C. braakii infection are still unknown because of the limitations in accurate identification by using currently available commercial biochemical testing and previously, only 6 cases of C. braakii infection have been reported. Physicians should focus on this species, because it causes community-acquired infections, although further studies are needed to clarify the clinical characteristics of C. braakii infections. [ABSTRACT FROM AUTHOR]