One-loop flavor changing electromagnetic transitions

We discuss the effect of the external fermion masses in the flavor-changing radiative transitions of a heavy fermion (quark or lepton) to a lighter fermion at the one-loop level, and point out an often overlooked crucial difference in the sign of a charge factor between transitions of the down type $s\to d\gamma$ and the up type $c\to u\gamma$. We give formulas for the $F\to f\gamma$ effective vertex in various approximations and the exact formula for $t\to c\gamma$ and $\tau \to \mu \gamma$.Comment: LaTeX 16 pages + 4 postscript figures. Misprints corrected, some Comments adde

Bloodstream and endovascular infections due to Abiotrophia defectiva and Granulicatella species

BACKGROUND: Abiotrophia and Granulicatella species, previously referred to as nutritionally variant streptococci (NVS), are significant causative agents of endocarditis and bacteraemia. In this study, we reviewed the clinical manifestations of infections due to A. defectiva and Granulicatella species that occurred at our institution between 1998 and 2004. METHODS: The analysis included all strains of NVS that were isolated from blood cultures or vascular graft specimens. All strains were identified by 16S rRNA sequence analysis. Patients' medical charts were reviewed for each case of infection. RESULTS: Eleven strains of NVS were isolated during the 6-year period. Identification of the strains by 16S rRNA showed 2 genogroups: Abiotrophia defectiva (3) and Granulicatella adiacens (6) or "para-adiacens" (2). The three A. defectiva strains were isolated from immunocompetent patients with endovascular infections, whereas 7 of 8 Granulicatella spp. strains were isolated from immunosuppressed patients, mainly febrile neutropenic patients. We report the first case of "G. para-adiacens" bacteraemia in the setting of febrile neutropenia. CONCLUSION: We propose that Granulicatella spp. be considered as a possible agent of bacteraemia in neutropenic patients

Detection of Vibrio cholerae and Acanthamoeba species from same natural water samples collected from different cholera endemic areas in Sudan

<p>Abstract</p> <p>Background</p> <p><it>Vibrio cholerae </it>O1 and <it>V. cholerae </it>O139 infect humans, causing the diarrheal and waterborne disease cholera, which is a worldwide health problem. <it>V. cholerae </it>and the free-living amoebae <it>Acanthamoeba </it>species are present in aquatic environments, including drinking water and it has shown that <it>Acanthamoebae </it>support bacterial growth and survival. Recently it has shown that <it>Acanthamoeba </it>species enhanced growth and survival of <it>V. cholerae </it>O1 and O139. Water samples from different cholera endemic areas in Sudan were collected with the aim to detect both <it>V. cholerae </it>and <it>Acanthamoeba </it>species from same natural water samples by polymerase chain reaction (PCR).</p> <p>Findings</p> <p>For the first time both <it>V. cholerae </it>and <it>Acanthamoeba </it>species were detected in same natural water samples collected from different cholera endemic areas in Sudan. 89% of detected <it>V. cholerae </it>was found with <it>Acanthamoeba </it>in same water samples.</p> <p>Conclusions</p> <p>The current findings disclose <it>Acanthamoedae </it>as a biological factor enhancing survival of <it>V. cholerae </it>in nature.</p

Pathogen-pathogen interactions: a comparative study of Escherichia coli interactions with the clinical and environmental isolates of Acanthamoeba

In this study, we compared the interactions of invasive and non-invasive strains of E. coli with clinical and environmental isolates of Acanthamoeba. The environmental isolate of Acanthamoeba exhibited significantly higher association with E. coli compared with the clinical isolates of Acanthamoeba. The ratio of E. coli per amoebae was more than 8-fold higher in the environmental isolate compared with the clinical isolates of Acanthamoeba. Interestingly, non-pathogenic environmental Acanthamoeba showed uptake and/or survival of the non-invasive E. coli. In contrast, clinical isolates of Acanthamoeba did not support uptake and/or survival of non-invasive E. coli. Using several mutants derived from K1, we demonstrated that outer membrane protein A (OmpA) and lipopolysaccharide (LPS) are crucial bacterial determinants responsible for E. coli K1 interactions and in the intracellular survival of E. coli in Acanthamoeba. The use of Acanthamoeba as a model to study E. coli K1 pathogenesis and to understand bacterial immune evasion strategies is discussed further