Superconducting decay length in a ferromagnetic metal

The complex decay length xi characterizing penetration of superconducting correlations into a ferromagnet due to the proximity effect is studied theoretically in the frame of the linearized Eilenberger equations. The real part xi_1 and imaginary part xi_2 of the decay length are calculated as functions of exchange energy and the rates of ordinary, spin flip and spin orbit electronic scattering in a ferromagnet. The lengths xi_1,2 determine the spatial scales of, respectively, decay and oscillation of a critical current in SFS Josephson junctions in the limit of large distance between superconducting electrodes. The developed theory provides the criteria of applicability of the expressions for xi_1 and xi_2 in the dirty and the clean limits which are commonly used in the analysis of SF hybrid structures.Comment: 5 pages, 3 figure

Molecular epidemiology of ESBL-producing E. coli and K. pneumoniae: establishing virulence clusters

Laure Surgers,1,2 Peter Boersma,3 Pierre-Marie Girard,1,4 Audrey Homor,5 Delphine Geneste,2 Guillaume Arlet,2,5 Dominique Decré,2,5 Anders Boyd4 1Infectious Diseases Department, Saint-Antoine Hospital, APHP, Paris, France; 2Sorbonne University, INSERM, U1135, Centre d’Immunologie et des Maladies Infectieuses, CIMI Team 13, Paris, France; 3Department of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, USA; 4INSERM, Sorbonne Université, Institut Pierre Louis d’Épidémiologie et de Santé Publique, Paris, France; 5Bacteriology Department, Saint-Antoine Hospital, APHP, Paris, France Objective: To genetically characterize clusters of virulence factors (VFs) among extended spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae and assess whether these clusters are associated with genetic determinants or clinical outcomes. Methods: One hundred forty-eight E. coli and 82 K. pneumoniae clinical isolates were obtained from 213 patients in Paris, France. Isolates underwent ESBL characterization, MultiLocus Sequence Typing (MLST) typing and phylogenetic group identification. Detection of ten E. coli and seven K. pneumoniae VF-encoding genes were assessed, from which a k-medians partition algorithm with Jaccard similarity measure was used to construct clusters. Results: CTX-M was the predominant ESBL and susceptibility to trimethoprim–sulfamethoxazole (32%), ciprofloxacin (22%) and aminoglycosides (32%) was low. In E. coli, there were five identified clusters, with significantly different distributions of ESBL-sequence type (P<0.001), ST131 (P<0.001) and phylogenetic group (P=0.001) between clusters. “Siderophore exclusive”, “siderophore exclusive with iroN ” and “adhesin sfa/papGIII-rich” clusters had higher 12-month mortality rates compared to others (49% vs 22%, respectively, P=0.02). In K. pneumoniae, three different clusters, with significantly different distributions of aminoglycoside-sensitivity (P<0.004), MLST-type (P<0.001) and relaxase plasmids (P=0.001) were described. Conclusion: Distinct clusters of E. coli and K. pneumoniae VFs are observed within ESBL-producing isolates and are strongly associated with several genetic determinants. Their association with overall morbidity and mortality requires further evidence. Keywords: ESBL, virulence, mortality, E. coli, K. pneumonia

Features of Toxoplasma gondii reactivation after allogeneic hematopoietic stem-cell transplantation in a high seroprevalence setting

We performed a single-centre retrospective study to evaluate the effectiveness of Toxoplasma gondii prevention strategies after allogeneic stem-cell transplantation. The charts of 138 allogeneic stem-cell recipients over a 4-year period were reviewed. Forty-nine percent of patients were not receiving optimal trimethoprim–sulfamethoxazole (TMP–SMZ) prophylaxis at day +30, mainly due to persistent cytopenia. Six months after transplantation, the rate of toxoplasmosis reactivation was 11.6%, including nine cases of Toxoplasma infection and seven cases of Toxoplasma disease. Fifty-six percent of cases of reactivation occurred before day +30. Thirty-eight percent occurred in patients receiving atovaquone prophylaxis. In 57% of patients presenting with Toxoplasma disease, signs of disease were present at first evidence of Toxoplasma DNA in peripheral blood samples. This study illustrates the limitations inherent to currently used toxoplasmosis prevention strategies and argues for the use of a combined prophylactic and preemptive approach. After performing the initial study, we limited the use of atovaquone in favour of TMP–SMZ when possible, and implemented an early prevention strategy consisting of the introduction of prophylaxis starting on day of engraftment. Over the following 16 months, 88.9% of eligible Toxoplasma-seropositive patients were receiving TMP–SMZ at day +30, and the rate of early Toxoplasma reactivation was 1.5%

Clinical and microbiological determinants of severe and fatal outcomes in patients infected with Enterobacteriaceae producing extended-spectrum β-lactamase

Although extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have become a worldwide public health concern, little is known regarding the clinical course of colonized or infected individuals. Our objective was to characterize the determinants of fatal outcomes related to ESBL-producing microorganisms at a large hospital in Paris, France. In 2012–2013, all consecutive patients with clinical samples testing positive for ESBL-producing Enterobacteriaceae at Saint-Antoine Hospital were identified. Patient clinical data were obtained at hospital entry, while information on intensive care unit (ICU) admissions and death were prospectively collected. Risk-factors for fatal 1-year outcomes were assessed using logistic regression. In total, 643/4684 (13%) ESBL-positive samples were observed, corresponding to 516 episodes (n = 206, 40% treated) among 330 patients. Most episodes were nosocomial-related (n = 347/516, 67%) involving Escherichia coli (n = 232/516, 45%) or Klebsiella pneumoniae (n = 164/516, 32%). Empirical antibiotic therapy was adequate in 89/206 (43%) infections, while the median length of hospital stay was 30 days [interquartile range (IQR) = 11–55] and 39/201 (19%) were admitted to the ICU. Overall, 104/241 patients (43%) with available data died within 1 year. In the multivariable analysis, 1-year death was associated with age >80 years (p = 0.01), concomitant comorbidity (p = 0.001), nosocomial-acquired infection (p = 0.002), and being infected rather than colonized (p < 0.001). In this series of patients with identified samples of ESBL-producing Enterobacteriaceae, hospital burden was large and 1-year mortality rates high. Understanding which patients in this setting would benefit from broad-spectrum empirical antibiotic therapy should be further examined