Structural and Functional Aspects of Class A Carbapenemases.

The fight against infectious diseases is probably one of the greatest public health challenges faced by our society, especially with the emergence of carbapenem-resistant gram-negatives that are in some cases pan-drug resistant. Currently,β-lactamase-mediated resistance does not spare even the newest and most powerful β-lactams (carbapenems), whose activity is challenged by carbapenemases. The worldwide dissemination of carbapenemases in gram-negative organisms threatens to take medicine back into the pre-antibiotic era since the mortality associated with infections caused by these superbugs is very high, due to limited treatment options. Clinically-relevant carbapenemases belong either to metallo-β- lactamases (MBLs) of Ambler class B or to serine-β-lactamases (SBLs) of Ambler class A and D enzymes. Class A carbapenemases may be chromosomally-encoded (SME, NmcA, SFC-1, BIC-1, PenA, FPH-1, SHV-38), plasmid-encoded (KPC, GES, FRI-1) or both (IMI). The plasmid-encoded enzymes are often associated with mobile elements responsible for their mobilization. These enzymes, even though weakly related in terms of sequence identities, share structural features and a common mechanism of action. They variably hydrolyse penicillins, cephalosporins, monobactams, carbapenems, and are inhibited by clavulanate and tazobactam. Three-dimensional structures of class A carbapenemases, in the apo form or in complex with substrates/inhibitors, together with site-directed mutagenesis studies, provide essential input for identifying the structural factors and subtle conformational changes that influence the hydrolytic profile and inhibition of these enzymes. Overall, these data represent the building blocks for understanding the structure-function relationships that define the phenotypes of class A carbapenemases and can guide the design of new molecules of therapeutic interest

Draft Genome Sequence of the Serratia rubidaea CIP 103234T Reference Strain, a Human-Opportunistic Pathogen.

We provide here the first genome sequence of a Serratia rubidaea isolate, a human-opportunistic pathogen. This reference sequence will permit a comparison of this species with others of the Serratia genus

Whole-Genome Sequence of a European Clone II and OXA-72-Producing Acinetobacter baumannii Strain from Serbia.

We report here the draft genome sequence of a carbapenem-resistant Acinetobacter baumannii strain isolated from a patient, a strain which previously stayed in Serbia. This isolate possessed the blaOXA-72 carbapenemase gene. The draft genome sequence consists of a total length of 3.91 Mbp, with an average G+C content of 38.8%

Feeding behaviour of broiler chickens: a review on the biomechanical characteristics

Feed related costs are the main drivers of profitability of commercial poultry farms, and good nutrition is mainly responsible for the exceptional growth rate responses of current poultry species. So far, most research on the poultry feeding behaviour addresses the productivity indices and birds' physiological responses, but few studies have considered the biomechanical characteristics involved in this process. This paper aims to review biomechanical issues related to feed behaviour of domestic chickens to address some issues related to the feed used in commercial broiler chicken production, considering feed particle size, physical form and the impact of feeders during feeding. It is believed that the biomechanical evaluation might suggest a new way for feed processing to meet the natural feeding behaviour of the birds

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii in New Caledonia

ABSTRACTCarbapenem-resistant Acinetobacter baumannii (CR-Ab) ranked third, with a frequency of 24.8%, among 202 strains of multidrug-resistant bacteria isolated from clinical samples in the main hospital of New Caledonia in 2004. All CR-Ab isolates were analysed by isoelectric focusing, conjugation, pulsed-field gel electrophoresis and PCR for the presence of carbapenemase genes. Fifty CR-Ab isolates produced carbapenemase OXA-23. The isolates belonged to a single clone presenting several subtypes, suggesting an endemic situation. This study further illustrates the widespread prevalence of carbapenemase OXA-23-producing CR-Ab isolates in the South Pacific

Optimization of the MALDIxin test for the rapid identification of colistin resistance in Klebsiella pneumoniae using MALDI-TOF-MS

Background. With the dissemination of carbapenemase producers, a revival of colistin was observed for the treatment of infections caused by multidrug-resistant Gram-negatives. Unfortunately, the increasing usage of colistin led to the emergence of resistance. In Klebsiella pneumoniae, colistin resistance arises through addition of L-arabinose-4N (L-Ara4N) or phosphoethanolamine (pEtN) on the native lipid A. The underlying mechanisms involve numerous chromosome-encoded genes or the plasmid-encoded phosphoethanolamine transferase MCR. Currently, detection of colistin resistance is time consuming since it still relies on MIC determination by broth microdilution. Recently, a rapid diagnostic test based on MALDI-TOF detection of modified lipid A was developed (the MALDIxin test) and tested on Escherichia coli and Acinetobacter baumannii. Objectives. Optimize the MALDIxin test for the rapid detection of colistin resistance in Klebsiella pneumoniae. Methods. This optimization consists on an additional mild-acid hydrolysis of 15 min in 1% acetic acid. The optimized method was tested on a collection of 81 clinical K. pneumoniae isolates including 49 colistin resistant strains among which 45 correspond to chromosome-encoded resistance, 3 MCR-related resistance and one isolate harbouring both mechanisms. Results. The optimized method allowed the rapid (< 30 min) identification of L-Ara4N and pEtN modified lipid A of K. pneumoniae which are known to be the real triggers of polymyxin resistance. In the same time, it discriminates between chromosome-encoded and MCR-related polymyxin resistance. Conclusions. The MALDIxin test has the potential to become an accurate tool for the rapid diagnostic of colistin resistance in clinically-relevant Gram negative bacteria

Worldwide Diversity of Klebsiella pneumoniae That Produce β-Lactamase blaKPC-2 Gene1

TOC summary: Clones harboring different plasmids with identical genetic structure could be the origin of worldwide spread

Editorial: Antimicrobial Resistance as a Global Public Health Problem: How Can We Address It?

No abstract availabl