On the influence of the cosmological constant on gravitational lensing in small systems

The cosmological constant Lambda affects gravitational lensing phenomena. The contribution of Lambda to the observable angular positions of multiple images and to their amplification and time delay is here computed through a study in the weak deflection limit of the equations of motion in the Schwarzschild-de Sitter metric. Due to Lambda the unresolved images are slightly demagnified, the radius of the Einstein ring decreases and the time delay increases. The effect is however negligible for near lenses. In the case of null cosmological constant, we provide some updated results on lensing by a Schwarzschild black hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation, references added, results unchanged, in press on PR

Occurrence of Carbapenem-Resistant Acinetobacter baumannii Clones at Multiple Hospitals in London and Southeast England

From late 2003 to the end of 2005, the Health Protection Agency's national reference laboratories received approximately 1,600 referrals of Acinetobacter spp., including 419 and 58 examples, respectively, of two carbapenem-resistant Acinetobacter baumannii lineages, designated OXA-23 clones 1 and 2. Representatives of these clones were obtained from 40 and 8 hospitals, respectively, in London or elsewhere in Southeast England. Both clones had blaOXA-23-like genes, as well as the intrinsic (but downregulated) blaOXA-51-like carbapenemase genes typical of A. baumannii. Both were highly multiresistant: only colistin and tigecycline remained active versus OXA-23 clone 1 isolates; OXA-23 clone 2 isolates were also susceptible to amikacin and minocycline. These lineages increase the burden created by the southeast (SE) clone, a previously reported A. baumannii lineage with variable carbapenem resistance contingent on upregulation of the blaOXA-51-like gene. Known since 2000, the SE clone had been referred from over 40 hospitals by the end of 2005, with 627 representatives received by the reference laboratories. The OXA-23 clone 2 is now in decline, but OXA-23 clone 1 continues to be referred from new sites, as does the SE clone. Their spread is forcing the use of unorthodox therapies, principally colistin and tigecycline, although the optimal regimens remain uncertain

Wide geographic spread of diverse acquired AmpC beta-lactamases among Escherichia coli and Klebsiella spp. in the UK and Ireland

To determine the distribution of acquired AmpC beta-lactamases in 173 isolates of Escherichia coli and Klebsiella spp. submitted to the UK's national reference laboratory for antibiotic resistance

Antimicrobial treatment and clinical outcome for infections with carbapenem- and multiply-resistant Acinetobacter baumannii around London

Carbapenem- and multiply-resistant Acinetobacter baumannii (C-MRAB) are challenging pathogens, often susceptible only to polymyxins and tigecycline. We reviewed clinical outcomes in relation to antibiotic treatment for 166 consecutive patients infected or colonised with these organisms at 18 hospitals around London, UK. Clinical data were obtained along with the isolates, which were typed by pulsed-field gel electrophoresis (PFGE). Outcomes were compared for colonised and infected patients and in relation to treatment, with associations examined by logistic regression. Most subjects (103/166; 62%) were in Intensive Care Units (ICUs) or high dependency units; 84 (50.6%) were judged to be infected and 73 (44.0%) were colonised, with 9 indeterminate. Among the 166 C-MRAB isolates, 141 belonged to OXA-23 clone 1, a European clone II lineage. Survival rates among infected and colonised patients were 68% and 67%, respectively (P > 0.05), indicating little attributable mortality. Univariate and multivariate analyses indicated poorer outcomes among ICU-infected patients and those with pulmonary infection or bacteraemia, whereas trauma patients had significantly better outcomes than the generality. Outcomes varied with hospital, even in multivariate analysis, reflecting either differences in management or case mix. There was little association between outcome and therapy with colistin and/or tigecycline except that, among patients with respiratory infection, 12/15 treated with intravenous colistin alone had poor outcome compared with 1/8 whose therapy include nebulised colistin. This difference was significant (P = 0.003), although the patients receiving nebulised drug were mostly younger, included trauma cases and were at a hospital with good outcomes

Clinical epidemiology of the global expansion of klebsiella pneumoniae carbapenemases

Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile beta-lactamases have spread internationally among Gram-negative bacteria, especially K pneumoniae, although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now

Clinical epidemiology of the global expansion of Klebsiella pneumoniae carbapenemases

Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile β-lactamases have spread internationally among Gram-negative bacteria, especially K pneumoniae, although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now

Clinical epidemiology of the global expansion of Klebsiella pneumoniae carbapenemases

Klebsiella pneumoniae carbapenemases (KPCs) were originally identified in the USA in 1996. Since then, these versatile β-lactamases have spread internationally among Gram-negative bacteria, especially K pneumoniae, although their precise epidemiology is diverse across countries and regions. The mortality described among patients infected with organisms positive for KPC is high, perhaps as a result of the limited antibiotic options remaining (often colistin, tigecycline, or aminoglycosides). Triple drug combinations using colistin, tigecycline, and imipenem have recently been associated with improved survival among patients with bacteraemia. In this Review, we summarise the epidemiology of KPCs across continents, and discuss issues around detection, present antibiotic options and those in development, treatment outcome and mortality, and infection control. In view of the limitations of present treatments and the paucity of new drugs in the pipeline, infection control must be our primary defence for now