Antimicrobial resistance and resistance mechanisms of Enterobacteriaceae in ICU and non-ICU wards in Europe and North America: SMART 2011-2013.

Intensive care units (ICUs) are often described as hotbeds of antimicrobial resistance, with high rates of extended-spectrum ß-lactamase (ESBL)-producing and multidrug-resistant (MDR) Enterobacteriaceae. Data from the SMART study were used to examine differences between the susceptibility of Enterobacteriaceae from ICU and non-ICU wards in Europe and North America. In total, 21,470 Enterobacteriaceae isolates from intra-abdominal and urinary tract infections were collected at 90 sites in 20 European and North American countries in 2011-2013. Susceptibility and ESBL phenotypes were determined using the CLSI broth microdilution method and breakpoints. Susceptibility was lower and ESBL and MDR rates were higher in ICUs, with much greater ICU/non-ICU differences in Europe than North America. Susceptibility was lower and ESBL and MDR rates were higher in Europe than in North America in both patient locations. Resistance among Enterobacteriaceae in Europe was largely driven by Klebsiella pneumoniae, which had high rates of ESBLs (41.2% in ICUs; mostly CTX-M) and carbapenemases (13.2%; mostly KPC and OXA). For all Enterobacteriaceae combined, only ertapenem and amikacin inhibited >90% of isolates in ICUs in both regions. In North America, ertapenem, imipenem and amikacin inhibited >90% of K. pneumoniae from ICUs, whereas in Europe only amikacin did. ESBL and MDR rates varied considerably within Europe. Antimicrobial resistance was higher in Europe than North America, especially in ICUs. Further surveillance at the country, hospital and even patient ward level, and investigation of reasons for these findings, would be useful for the development of effective strategies to reduce antimicrobial resistance in ICUs.

Dissemination of NDM metallo-ß-lactamase genes among clinical isolates of Enterobacteriaceae collected during the SMART global surveillance study from 2008 to 2012.

The prevalence of carbapenemase enzymes continues to increase. Among the Ambler class B enzymes is the New Delhi metallo-ß-lactamase (NDM). This particular enzyme is capable of hydrolyzing nearly all ß-lactam antimicrobial agents and has spread rapidly, becoming a global problem. Therapeutic treatment options for patients infected with isolates which produce this enzyme are difficult to manage, as cross-resistance to other antimicrobial classes is common. The Study for Monitoring Antimicrobial Resistance Trends (SMART) is a global surveillance study evaluating the antimicrobial susceptibilities of numerous Gram-negative bacterial species recovered from people with intra-abdominal and urinary tract infections. The Clinical and Laboratory Standards Institute methods and a molecular analysis identified 134 isolates of Enterobacteriaceae (nine species) and one Acinetobacter sp. with blaNDM genes. These isolates were collected in nine countries, and >95% of the isolates possessed the NDM-1 variant. The MIC90 values were >4 mg/liter and >8 mg/liter for ertapenem and imipenem, respectively. No tested ß-lactam or ß-lactamase inhibitor combination had activity against these isolates. Resistance to amikacin (79.9%) and levofloxacin (82.8%) was common. Nearly all the isolates encoded additional enzymes, including AmpC cephalosporinases and extended-spectrum ß-lactamases. There is an urgent need for infection control and continued global monitoring of isolates which harbor the NDM enzyme, as evidenced by recent outbreaks.

The phage N4 virion RNA polymerase catalytic domain is related to single-subunit RNA polymerases.

In vitro, bacteriophage N4 virion RNA polymerase (vRNAP) recognizes in vivo sites of transcription initiation on single-stranded templates. N4 vRNAP promoters are comprised of a hairpin structure and conserved sequences. Here, we show that vRNAP consists of a single 3500 amino acid polypeptide, and we define and characterize a transcriptionally active 1106 amino acid domain (mini-vRNAP). Biochemical and genetic characterization of this domain indicates that, despite its peculiar promoter specificity and lack of extensive sequence similarity to other DNA-dependent RNA polymerases, mini-vRNAP is related to the family of T7-like RNA polymerases.

N4 RNA polymerase II, a heterodimeric RNA polymerase with homology to the single-subunit family of RNA polymerases.

Bacteriophage N4 middle genes are transcribed by a phage-coded, heterodimeric, rifampin-resistant RNA polymerase, N4 RNA polymerase II (N4 RNAPII). Sequencing and transcriptional analysis revealed that the genes encoding the two subunits comprising N4 RNAPII are translated from a common transcript initiating at the N4 early promoter Pe3. These genes code for proteins of 269 and 404 amino acid residues with sequence similarity to the single-subunit, phage-like RNA polymerases. The genes encoding the N4 RNAPII subunits, as well as a synthetic construct encoding a fusion polypeptide, have been cloned and expressed. Both the individually expressed subunits and the fusion polypeptide reconstitute functional enzymes in vivo and in vitro.

The domain of hypertrophic chondrocytes in growth plates growing at different rates.

In this study, we tested the hypotheses that (a) both the domain volume (volume of the cell and the matrix it has formed) and matrix volume of juxtametaphyseal hypertrophic chondrocytes in the growth plate is tightly controlled, and that (b) the domain volume of juxtametaphyseal hypertrophic chondrocytes is a strong determinant of the rate of bone length growth. We analyzed the rate of bone length growth (oxytetracycline labeling techniques) and nine stereologic and kinetic parameters related to the juxtametaphyseal chondrocytic domain in the proximal and distal radial and tibial growth plates of 21- and 35-day-old rats. The domain volume increased with increasing growth rates, independent of the location of the growth plate and the age of the animal. Within age groups, the matrix volume per cell increased with increasing growth rates, but an identical growth plate had the same matrix volume per cell in 21- and 35-day-old rats. The most suitable regression model (R2 = 0.992) to describe the rate of bone length growth included the mean volume of juxtametaphyseal hypertrophic chondrocytes and the mean rate of cell loss/cell proliferation. This relationship was independent of the location of the growth plate and the age of the animal. The data suggest that the domain volume of juxtametaphyseal hypertrophic chondrocytes, as well as the matrix volume produced per cell, may be tightly regulated. In addition, the volume of juxtametaphyseal hypertrophic chondrocytes and the rate of cell loss/rate of cell proliferation may play the most important role in the determination of the rate of bone length growth.

Effects of succinylcholine on the electroencephalogram of dogs.

Electroencephalograms of 20 dogs given succinylcholine and concurrent artificial respiration were recorded. The amplitudes of the fast activity of the electroencephalograms were approximately one-fifth that observed in awake dogs. In addition, the occurrence of slow waves (6 to 8 Hz) was more marked in those dogs treated with succinylcholine. Succinylcholine caused a low amplitude dominant activity with increased moderate amplitude low frequency waves.