Mahoko Ikeda

Clostridium difficile flagellin stimulates toll-like receptor 5, and toxin B promotes flagellin-induced chemokine production via TLR5

AIMS Clostridium difficile is an important pathogen in nosocomial infections. Although C. difficile toxins are considered to be major virulence factors, pathogenesis of C. difficile associated diseases remains to be determined. In this study, we investigated whether C. difficile flagellin is involved in the pathogenesis of C. difficile-associated diseases. MAIN METHODS C. difficile flagellin was extracted from bacterial body by using a combination of ultracentrifugation and low speed centrifugation. Extracted C. difficile flagellin was added to HEK293T cells transiently transfected with pUNO-mcs (empty vector) or pUNO-hTLR5, and NF-kappaB activation was compared by a dual-luciferase assay. The amount of C. difficile flagellin-induced inflammatory mediators such as interleukin-8 and CCL20 was measured by ELISA assay in the culture media of intestinal epithelial cell lines, HT29 cells and Caco-2 cells. Flagellin induced phosphorylation of p38 mitogen-activated protein kinase was examined by Western blotting analysis in Caco-2 cells. The amount of C. difficile flagellin-induced inflammatory mediators in the presence, or absence of C. difficile toxin B was also measured by ELISA assay. KEY FINDINGS C. difficile flagellin induced activation of NF-kappaB in HEK293T cells via toll-like receptor 5. C. difficile flagellin also induced activation of p38 mitogen-activated protein kinase, and promoted the production of interleukin-8 and CCL20 in intestinal epithelial cells via toll-like receptor 5. Pretreatment with toxin B enhanced flagellin-induced cytokine productions. SIGNIFICANCE Our results indicate that toxin B promotes flagellin-induced activation of intestinal epithelial cells, and that C. difficile flagellin may play a role in the occurrence of C. difficile-associated diseases.

Propionimicrobium lymphophilum and Actinotignum schaalii bacteraemia: a case report

Propionimicrobium lymphophilum is an anaerobic Gram-positive bacillus that exists in human skin and urinary tract. The pathogenicity is, however, not well known. Only two cases of urinary tract infection have been described recently. In the case presented here, the bacterium was isolated, concomitant with Actinotignum schaalii, from blood culture of a patient with fever and difficulty of urination. The bacteria were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rRNA sequencing. The case was successfully treated with ampicillin/sulbactam.

Scedosporium prolificans Endocarditis: Case Report and Literature Review.

Scedosporium prolificans, a hyaline filamentous fungus, is widely distributed in the environment and is currently an emerging human pathogen, especially among immunocompromised patients. However, S. prolificans endocarditis is rare. We herein report a case of S. prolificans endocarditis in a 64-year-old patient with breast cancer in complete remission for 30 years after chemotherapy and radiation treatment who was not cured. Susceptibility testing showed resistance to all antifungal drugs, except echinocandin. A review of the literature revealed 10 cases of S. prolificans endocarditis; of these, only one involved an immunocompetent host with no risk factors and only two patients survived. In order to improve the mortality rate, it is necessary to establish rapid diagnostic methods and efficient therapeutic approaches.

Pyogenic liver abscess due to hypervirulent Klebsiella pneumoniae in a 14-year-old boy

A 14-year-old otherwise healthy boy presented with right-sided back pain following high fever. Abdominal computed tomography scan showed a large liver abscess. Klebsiella pneumoniae (KP) was rapidly identified from peripheral blood using the melting temperature mapping (Tm) method, which enables identification of pathogenic microorganisms within four hours after patient sample collection. He was diagnosed with pyogenic liver abscess (PLA) caused by KP on the day of admission. The KP was the hypervirulent (hv) clinical variant (string test positive, serotype K1, sequence type 23, rmpA and magA positive). After intravenous antibiotic therapy and drainage of the abscess, his condition resolved. The highlights of this case report are a healthy child with hypervirulent Klebsiella pneumoniae liver abscess in Japan and the new Tm mapping method for rapid and accurate identification of the pathogenic microorganism.

Clinical and microbiological characteristics and occurrence of Klebsiella pneumoniae infection in Japan

Purpose Klebsiella pneumoniae is a pathogen that causes pneumonia and urinary tract infection. Hypervirulent K. pneumoniae strains often show hypermucoviscosity, are of the K1 or K2 serotype, and harbor the rmpA and magA genes. However, the differences in the prevalence of K. pneumoniae with these hypervirulent characteristics between the infection and colonization status are not well understood. Therefore, in this study, we compared the clinical and microbiological characteristics of K. pneumoniae isolated from urine or sputum samples of cases of infection and colonization. Patients and methods This retrospective study was conducted at a tertiary care teaching hospital in Tokyo, Japan. Patients whose sputum or urine tested positive for the presence of K. pneumoniae isolates were randomly included in the study. Clinical and microbiological data were collected from medical records. Results Of the 130 cases investigated, 68 and 62 cases showed the presence of K. pneumoniae in the sputum and urine, respectively. There were 49 infection cases, including 21 in the sputum group and 28 in the urine group. The infections were not accompanied by liver abscess. Of the 130 K. pneumoniae isolates, 25 (19.2%) showed capsular serotype K1 or K2, whereas 33 (25.4%) showed hypermucoviscosity. The prevalence of virulence genes magA, allS, rmpA, mrkD, uge, kfu-BC, and wabG was 10% (all in K1), 13.1%, 16.9%, 85.4%, 79.2%, 36.9%, and 91.5%, respectively. In both the sputum and urine groups, there was no difference in the characteristics of patients with infection and those with colonization. Analysis of microbiological characteristics revealed that only rmpA was significantly more frequent in the infection cases than in the colonization/asymptomatic cases in both the sputum and urine groups. Conclusion The rmpA-positive K. pneumoniae isolates were dominant in the infection cases compared with those in the colonization/asymptomatic cases, suggesting that rmpA may play a crucial role in the development of urinary tract infection and pneumonia.