Multi-Phase Interleaved AC-DC Step-Down Converter with Power Factor Improvement.

This paper presents the converter design of a single-phase non-isolated step-down controlled rectifier for power factor improvement and output voltage regulation. The converter consists of a full-bridge diode rectifier and a DC-DC interleaved buck converter of two or more switching cells that has an LC filter in its input. It is proposed that the interleaved switching cells operate in discontinuous conduction mode and the current through the input LC filter be continuous, avoiding switching frequency components to be injected into the grid. The controller, which has a simple structure and a small number of sensors, allows the system to achieve a high power factor. It also regulates the output voltage to a constant reference. An experimental prototype is built and tested to validate the analysis and proposed design. The closed-loop converter is evaluated both in a steady state and in transient conditions. At steady state, the converter achieves a power factor above 0.9 with a maximum of 45.4% THD at 110.1W. The main contributions of this paper are guidelines for the design of the converter, open-loop analysis, and converter control.

Rise and fall of KPC-producing Klebsiella pneumoniae in New York City.

OBJECTIVES: The study objective was to examine the epidemiological trends of KPC-producing Klebsiella pneumoniae in New York City medical centres. PATIENTS AND METHODS: Single patient isolates of K. pneumoniae were collected from nine medical centres in New York City during a 3 month period from 2013 to 2014. Isolates were tested for the presence of blaKPC. Results were compared with similar surveillance studies conducted in 2006 and 2009. Infection control data, including utilization of medical devices, were analysed at a subset of hospitals. RESULTS: There was a progressive decline in the percentage of K. pneumoniae harbouring blaKPC from 2006 to 2013-14. For the nine hospitals that participated in all three surveillance studies, the percentages of isolates with blaKPC fell from 36% in 2006 to 25% in 2009 to 13% in 2013-14. Seven of the nine hospitals had marked declines in isolates with blaKPC, while two hospitals continued to struggle with this pathogen. These two hospitals were smaller and had longer lengths of patient stay. Device utilization rates were obtained from two hospitals that successfully controlled the spread of KPC-producing K. pneumoniae; both had ∼20%-25% reduction in the usage of urinary catheters. Changes in antibiotic usage at one hospital could not explain the decline in these pathogens. CONCLUSIONS: Over the past decade there has been a steady decline in KPC-producing K. pneumoniae in most New York City hospitals. The reason for the decline is probably multifactorial, involving a reduction in device (catheter) utilization and possibly an improvement in infection control practices.

Actinomyces naeslundii: An Uncommon Cause of Endocarditis.

Actinomyces rarely causes endocarditis with 25 well-described cases reported in the literature in the past 75 years. We present a case of prosthetic valve endocarditis (PVE) caused by Actinomyces naeslundii. To our knowledge, this is the first report in the literature of endocarditis due to this organism and the second report of PVE caused by Actinomyces.

Activity of Meropenem Combined with RPX7009, a Novel ß-Lactamase Inhibitor, against Gram-Negative Clinical Isolates in New York City.

Multidrug-resistant Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are endemic to hospitals in New York City and other regions. RPX7009 is a novel ß-lactamase inhibitor with activity against serine carbapenemases. We tested the activity of meropenem plus RPX7009 against 4,500 recent Gram-negative clinical isolates from 11 New York City hospitals. The meropenem-RPX7009 combination was found to have excellent in vitro activity against Escherichia coli, K. pneumoniae, and Enterobacter spp., including multidrug-resistant (MDR) KPC-producing strains. Overall, 131/133 (98.5%) KPC-producing Enterobacteriaceae strains were inhibited by meropenem (≤1 µg/ml) plus RPX7009 (8 µg/ml). In a limited number of strains, the combination appeared to have reduced activity against KPC-producing K. pneumoniae isolates with diminished ompK35 and ompK36 expression. The addition of RPX7009 did not affect the activity of meropenem against Acinetobacter baumannii and Pseudomonas aeruginosa. The meropenem-RPX7009 combination shows promise as a novel agent against KPC-producing Enterobacteriaceae and deserves further study. Other approaches will be needed to address multidrug-resistant A. baumannii and P. aeruginosa, which typically possess different mechanisms of carbapenem resistance.

Activity of Imipenem with Relebactam against Gram-Negative Pathogens from New York City.

Imipenem with relebactam was active against Escherichia coli, Klebsiella pneumoniae, and Enterobacter spp., including K. pneumoniae carbapenemase (KPC)-producing isolates. Loss of OmpK36 in KPC-producing K. pneumoniae isolates affected the susceptibility of this combination. Enhanced activity was evident against Pseudomonas aeruginosa, including isolates with depressed oprD and increased ampC expression. However, the addition of relebactam to imipenem did not provide added benefit against Acinetobacter baumannii. The combination of imipenem with relebactam demonstrated activity against KPC-producing Enterobacteriaceae and multidrug-resistant P. aeruginosa.

Reduction in the prevalence of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in New York City.

We compared susceptibilities of Acinetobacter baumannii and Pseudomonas aeruginosa collected during surveillance studies conducted during 2009 and 2013-2014 involving hospitals in New York City. There were significant decreases in the number of carbapenem-resistant A baumannii and P aeruginosa cases during 2013-2014; it appears the institution of effective infection control measures has contributed to this decline. However the number of isolates of A baumannii with OXA-23-type ß-lactamase increased during 2013-2014.

Activity of eravacycline against Enterobacteriaceae and Acinetobacter baumannii, including multidrug-resistant isolates, from New York City.

Eravacycline demonstrated in vitro activity against a contemporary collection of more than 4,000 Gram-negative pathogens from New York City hospitals, with MIC50/MIC90 values, respectively, for Escherichia coli of 0.12/0.5 µg/ml, Klebsiella pneumoniae of 0.25/1 µg/ml, Enterobacter aerogenes of 0.25/1 µg/ml, Enterobacter cloacae 0.5/1 µg/ml, and Acinetobacter baumannii of 0.5/1 µg/ml. Activity was retained against multidrug-resistant isolates, including those expressing KPC and OXA carbapenemases. For A. baumannii, eravacycline MICs correlated with increased expression of the adeB gene.