Molecular Epidemiology of Extended-Spectrum Beta-Lactamase-Producing Escherichia Coli in Tunisia and Characterization of Their Virulence Factors and Plasmid Addiction Systems.

Molecular epidemiology of extended-spectrum beta-lactamase-producing Escherichia coli in Tunisia and characterization of their virulence factors and plasmid addiction systems.

BMC Microbiol. 2013 Jun 25; 13(1): 147
Mnif B, Harhour H, Jdidi J, Mahjoubi F, Genel N, Arlet G, Hammami A

Extended-spectrum beta-lactamases (ESBLs), particularly CTX-M- type ESBLs, are among the most important resistance determinants spreading worldwide in Enterobacteriaceae. The aim of this study was to characterize a collection of 163 ESBL-producing Escherichia coli collected in Tunisia, their ESBL-encoding plasmids and plasmid associated addiction systems.The collection comprised 163 ESBL producers collected from two university hospitals of Sfax between 1989 and 2009. 118 isolates harbored blaCTX-M gene (101 blaCTX-M-15 gene and 17 blaCTX-M-14 gene). 49 isolates carried blaSHV-12 gene, 9 blaSHV-2a gene and only 3 blaTEM-26 gene. 16 isolates produced both CTX-M and SHV-12. The 101 CTX-M-15-producing isolates were significantly associated to phylogroup B2 and exhibiting a high number of virulence factors. 24 (23.7%) of the group B2 isolates belonged to clonal complex ST131. Pulsed-field gel electrophoresis (PFGE) typing revealed a genetic diversity of the isolates. 144 ESBL determinants were transferable mostly by conjugation. The majority of plasmid carrying blaCTX-M-15 genes (72/88) were assigned to various single replicon or multireplicon IncF types and had significantly a higher frequency of addiction systems, notably the VagCD module.This study demonstrates that the dissemination of CTX-M-15 producing E. coli in our setting was due to the spread of various IncF-type plasmids harboring multiple addiction systems, into related clones with high frequency of virulence determinants. HubMed – addiction


A Computationally Designed Water-Soluble Variant of a G-Protein-Coupled Receptor: The Human Mu Opioid Receptor.

PLoS One. 2013; 8(6): e66009
Perez-Aguilar JM, Xi J, Matsunaga F, Cui X, Selling B, Saven JG, Liu R

G-protein-coupled receptors (GPCRs) play essential roles in various physiological processes, and are widely targeted by pharmaceutical drugs. Despite their importance, studying GPCRs has been problematic due to difficulties in isolating large quantities of these membrane proteins in forms that retain their ligand binding capabilities. Creating water-soluble variants of GPCRs by mutating the exterior, transmembrane residues provides a potential method to overcome these difficulties. Here we present the first study involving the computational design, expression and characterization of water-soluble variant of a human GPCR, the human mu opioid receptor (MUR), which is involved in pain and addiction. An atomistic structure of the transmembrane domain was built using comparative (homology) modeling and known GPCR structures. This structure was highly similar to the subsequently determined structure of the murine receptor and was used to computationally design 53 mutations of exterior residues in the transmembrane region, yielding a variant intended to be soluble in aqueous media. The designed variant expressed in high yield in Escherichia coli and was water soluble. The variant shared structural and functionally related features with the native human MUR, including helical secondary structure and comparable affinity for the antagonist naltrexone (K d ?=?65 nM). The roles of cholesterol and disulfide bonds on the stability of the receptor variant were also investigated. This study exemplifies the potential of the computational approach to produce water-soluble variants of GPCRs amenable for structural and functionally related characterization in aqueous solution. HubMed – addiction


Dimensions of Temperament Modulate Cue-Controlled Behavior: A Study on Pavlovian to Instrumental Transfer in Horses (Equus Caballus).

PLoS One. 2013; 8(6): e64853
Lansade L, Coutureau E, Marchand A, Baranger G, Valenchon M, Calandreau L

Pavlovian to instrumental transfer (PIT) is a central factor in how cues influence animal behavior. PIT refers to the capacity of a Pavlovian cue that predicts a reward to elicit or increase a response intended to obtain the same reward. In the present study, using an equine model, we assessed whether PIT occurs in hoofed domestic animals and whether its efficacy can be modulated by temperamental dimensions. To study PIT, horses were submitted to Pavlovian conditioning whereby an auditory-visual stimulus was repeatedly followed by food delivery. Then, horses were submitted to instrumental conditioning during which they learned to touch with their noses an object signaled by the experimenter in order to obtain the same reward. During the PIT test, the Pavlovian conditioned stimulus was presented to the animal in the absence of reward. At the end of the experiment, a battery of behavioral tests was performed on all animals to assess five temperamental dimensions and investigate their relationships with instrumental performance. The results indicate that PIT can be observed in horses and that its efficacy is greatly modulated by individual temperament. Indeed, individuals with a specific pattern of temperamental dimensions (i.e., higher levels of gregariousness, fearfulness, and sensory sensitivity) exhibited the strongest PIT. The demonstration of the existence of PIT in domesticated animals (i.e., horses) is important for the optimization of its use by humans and the improvement of training methods. Moreover, because PIT may be implicated in psychological phenomena, including addictive behaviors, the observation of relationships between specific temperamental dimensions and PIT efficacy may aid in identifying predisposing temperamental attributes. HubMed – addiction



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