Clinical and microbiological characteristics of Ruminococcus gnavus bacteremia and intra-abdominal infection.

OBJECTIVES: Ruminococcus gnavus is a rare human pathogen, and clinical data on R. gnavus infection are insufficient. This retrospective study aimed to investigate the clinical characteristics of R. gnavus infections. METHODS: This study included 13 cases of bacteremia and three cases of non-bacteremia infections caused by R. gnavus. We evaluated the patient data, infection source, clinical outcomes, and antimicrobial susceptibility of R. gnavus isolates for these cases. RESULTS: The median age of patients was 75 years (range 47-95), and eight patients were female. Twelve cases were presumed to have an intra-abdominal infection source, and the remaining four cases had an unknown infection source. The most common underlying conditions were immunosuppression (seven cases), solid tumors (seven cases), and history of gastrointestinal surgery (five cases). Thirteen patients exhibited gastrointestinal problems (dysfunction, bleeding, intra-abdominal infection, or inflammation). Multiple pathogens were observed in six cases, and fatal outcomes were recorded in three cases. Antimicrobial susceptibility data were available for eight isolates, all of which exhibited low minimum inhibitory concentrations to penicillin (≤0.03 µg/mL), ampicillin-sulbactam (≤0.5 µg/mL), piperacillin-tazobactam (≤4 µg/mL), and metronidazole (≤0.5-1 µg/mL). CONCLUSION: Ruminococcus gnavus is frequently associated with an intra-abdominal infection source, and treatment strategies should consider the possibility of multiple pathogens.

Catheter-related bloodstream Mycobacterium wolinskyi infection in an umbilical cord blood transplant recipient: a case report.

BACKGROUND: Catheter-related bloodstream infection (CRBSI), caused by rapidly growing mycobacteria (RGM), is a rare infectious complication in hematopoietic stem cell transplant (HSCT) recipients and can often be misdiagnosed as Gram-positive rod (GPR) bacteremia. CASE PRESENTATION: We present a case of CRBSI caused by Mycobacterium wolinskyi, a rare RGM, in a 44-year-old female patient who received an umbilical cord blood transplant. CONCLUSIONS: Rapidly growing mycobacteria can stain as GPRs and may grow in routine blood culture media after 3-4 days of incubation. These features are not widely known to clinicians, and acid-fast staining is therefore recommended when unidentifiable GPRs are detected in blood cultures, especially in immunocompromised patients, such as those with hematologic malignancies or intravascular devices.

Early diagnosis of Cryptococcus neoformans var. grubii meningitis using multiplex PCR assay in an immunocompetent patient.

Cryptococcosis is an invasive fungal infection that mainly affects the lungs and central nervous system. While patients with cell-mediated immunodeficiency are at high risk of developing cryptococcosis, there have been increasing reports of cryptococcosis in immunocompetent individuals with no underlying conditions. Herein, we report a case of cryptococcal meningitis in a 55-year-old apparently immunocompetent man with a history of heavy alcohol consumption. Although the patient was initially treated for tuberculous meningitis and varicella-zoster virus induced vasculopathy due to a history of exposure to tuberculosis and a presence of stroke, a multiplex polymerase chain reaction (PCR) assay of cerebrospinal fluid (CSF) identified Cryptococcus species unexpectedly, enabling swift treatment and a favorable clinical outcome. The multiplex PCR assay, which can identify multiple pathogens simultaneously and instantly, may lead to early diagnosis and treatment by detecting unanticipated pathogens. Furthermore, the strain was identified through multilocus sequence typing (MLST) analysis as Cryptococcus neoformans var. grubii, Sequence Type 5, molecular type: VNI. Although simplified microbial identification techniques such as mass spectrometry have recently been developed, molecular biological assays are still essential for the accurate identification of infectious strains.

A case of Salmonella osteomyelitis mimicking a malignant tumor of the humerus in an immunocompetent adult patient identified using broad-range polymerase chain reaction with sequencing of a biopsied specimen.

BACKGROUND: Salmonella infections are associated with gastroenteritis, enteric fever, bacteremia, focal infection, and chronic carrier state. Cases of Salmonella osteomyelitis are uncommon and mainly occur in individuals with immunosuppressive conditions. Herein, we report a case of Salmonella osteomyelitis that required differentiation from malignancy in an immunocompetent adult patient. CASE PRESENTATION: A 31-year-old previously healthy male truck driver presented with a 2-week history of pain in his left upper arm. He had fallen off the back of a truck 2 months previously and injured the left side of his body. He also had bloody diarrhea and fever. Computed tomography and magnetic resonance imaging revealed a lesion that appeared to be a bone tumor in the left humerus, and the patient was referred to our cancer center from another clinic. Culture of a biopsy specimen of the left humerus was negative; however, the consensus sequence in broad-range polymerase chain reaction (PCR) showed the highest similarity to the 16S rRNA gene of Salmonella enterica subspecies enterica. Curettage of the left humerus was performed, and the patient was administered levofloxacin for 6 weeks. He recovered left arm function and had no recurrence during 2 months of follow-up. CONCLUSIONS: When the culture of blood or biopsy specimens is negative in situations wherein a specific infection is suspected, broad-range PCR with sequencing should be considered to determine the causative organism.