Chemical Communication of Antibiotic Resistance by Highly Resistant Bacteria.

The overall antibiotic resistance of a bacterial population results from the combination of a wide range of susceptibilities displayed by subsets of bacterial cells. Bacterial heteroresistance to antibiotics has been documented for several opportunistic Gram-negative bacteria, but the mechanism of heteroresistance is unclear. I use Burkholderia cenocepacia as a model opportunistic bacterium to investigate the implications of heterogeneity in the response to the antimicrobial peptide polymyxin B (PmB) and also other bactericidal antibiotics. Here, I report that B. cenocepacia is heteroresistant to PmB. Population analysis profiling identified B. cenocepacia subpopulations arising from a seemingly homogenous culture that are resistant to higher levels of PmB than the rest of the cells in the culture, and protect the more sensitive cells from killing, as well as sensitive bacteria from other species, such as Pseudomonas aeruginosa and Escherichia coli. Communication of resistance depended on upregulation of putrescine synthesis and YceI, a widely conserved low-molecular weight secreted protein. Deletion of genes for the synthesis of putrescine and YceI abrogate protection, while pharmacologic inhibition of putrescine synthesis reduced resistance to PmB. Polyamines and YceI were also required for heteroresistance of B. cenocepacia to various bactericidal antibiotics. I propose that putrescine and YceI resemble danger infochemicals whose increased production by a bacterial subpopulation, becoming more resistant to bactericidal antibiotics, communicates higher level of resistance to more sensitive members of the population of the same or different species. Putrescine protects from antibiotics through its ability to compete with PmB for surface binding and protection against antibiotic-induced oxidative stress. YceI proteins are conserved bacterial lipocalins or “bacteriocalins”. Bacteriocalins from different Gram-positive and Gram-negative bacteria are involved in the response to hydrophobic or amphiphilic antibiotics (PmB, rifampicin, norfloxacin and ceftazidime) but not hydrophilic ones (such as gentamicin). This effect is achieved by their preferential binding affinity to hydrophobic moieties. Together, my findings uncover a novel, non-genetic and cooperative mechanism of transient increase in resistance chemically communicated from more resistant members of heterogeneous populations to less resistant bacteria of the same or other species. This multifactorial mechanism of communication of antibiotic resistance offers novel targets for antimicrobial intervention

Antimicrobial Heteroresistance: an Emerging Field in Need of Clarity

“Heteroresistance” describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic. Unfortunately, a lack of standard methods to determine heteroresistance has led to inappropriate use of this term. Heteroresistance has been recognized since at least 1947 and occurs in Gram-positive and Gram-negative bacteria. Its clinical relevance may be considerable, since more resistant subpopulations may be selected during antimicrobial therapy. However, the use of nonstandard methods to define heteroresistance, which are costly and involve considerable labor and resources, precludes evaluating the clinical magnitude and severity of this phenomenon. We review the available literature on antibiotic heteroresistance and propose recommendations for definitions and determination criteria for heteroresistant bacteria. This will help in assessing the global clinical impact of heteroresistance and developing uniform guidelines for improved therapeutic outcomes

Draft genome sequence of an enterococcus faecalis strain (24FS) that was isolated from healthy infant feces and exhibits high antibacterial activity, multiple-antibiotic resistance, and multiple virulence factors

Enterococcus faecalis 24FS is a bacteriocin-producing, multiply antibiotic-resistant, and potentially virulent bacterium isolated from healthy infant feces. The draft 2.9-Mb genome sequence revealed 2,968 protein-encoding genes; 11 antibiotic resistance, 8 virulence, and 3 bacteriocin genes; and 2 plasmids, 4 prophages, 30 insertion sequence (IS) elements, 1 transposon, and 1 integron

Complete genome sequence of Lactobacillus plantarum 10CH, a potential probiotic lactic acid bacterium with potent antimicrobial aActivity

Lactobacillus plantarum 10CH is a bacteriocin-producing potential probiotic lactic acid bacterium (LAB) strain isolated from cheese. Its complete nucleotide sequence shows a single circular chromosome of 3.3 Mb, with a G+C content of 44.51%, a 25-gene plantaricin bacteriocin gene cluster, and the absence of recognized virulence factors. [Abstract copyright: Copyright © 2017 El Halfawy et al.

Antibiotic capture by bacterial lipocalins uncovers an extracellular mechanism of intrinsic antibiotic resistance

15 p.-6 fig.The potential for microbes to overcome antibiotics of different classes before they reach bacterial cells is largely unexplored. Here we show that a soluble bacterial lipocalin produced by Burkholderia cenocepacia upon exposure to sublethal antibiotic concentrations increases resistance to diverse antibiotics in vitro and in vivo. These phenotypes were recapitulated by heterologous expression in B. cenocepacia of lipocalin genes from Pseudomonas aeruginosa, Mycobacterium tuberculosis,and methicillin-resistant Staphylococcus aureus. Purified lipocalin bound different classes of bactericidal antibiotics and contributed to bacterial survival in vivo. Experimental and X-ray crystal structure-guided computational studies revealed that lipocalins counteract antibiotic action by capturing antibiotics in the extracellular space. We also demonstrated that fat-soluble vitamins prevent antibiotic capture by binding bacterial lipocalin with higher affinity than antibiotics. Therefore, bacterial lipocalins contribute to antimicrobial resistance by capturing diverse antibiotics in the extracellular space at the site of infection, which can be counteracted by known vitamins.This work was funded by grants from Cystic Fibrosis Canada, the European Commission,a Marie Curie Career Integration grant (projects 618095, NONANTIRES), and the Infection and Immunity Translational Research Group, Northern Ireland HSC to M.A.V.;the Spanish Ministry for Economy and Competitiveness (MINECO CTQ2011-22724 and CTQ2014-57141-R), European Commission Marie Curie grants GLYCOPHARM FP7-PITNGA-2012-317297 and TOLLerant H2020-MSC-ETN-642157 to S.M.S.; and Canadian Institutes of Health research grant MOP-49597 and a grant from Cystic Fibrosis Canada to M.E.P.M.Peer reviewe

Phenotypic heterogeneity in fungi: importance and methodology

Phenotypic heterogeneity describes the variation that exists between individual cells, spores or other biological entities within genetically-uniform populations of fungi or other organisms. Studies over the last 10-15 years have successfully used laboratory- and modelling-based approaches to demonstrate the prevalence of phenotypic heterogeneity and characterise the molecular bases of the phenomenon (primarily centred around heterogeneous gene expression). In contrast to progress in these areas, the relevance of phenotypic heterogeneity for the competitive success of organisms in different natural scenarios, although widely speculated upon, has only recently begun to be investigated. This focus review addresses this latter question as tackled in recent studies with yeasts and filamentous fungi. We concentrate on the relevance to fungal activities such as survival against environmental stressors, pathogenesis, and spoilage. We also discuss methodologies for interrogating phenotypic heterogeneity in fungi. The emerging prevalence and apparent importance of fungal phenotypic heterogeneity provides a timely reminder that certain, potentially core aspects of fungal biology still remain widely under-explored

Putrescine Reduces Antibiotic-Induced Oxidative Stress as a Mechanism of Modulation of Antibiotic Resistance in <em>Burkholderia cenocepacia</em>

Communication of antibiotic resistance among bacteria via small molecules is implicated in transient reduction of bacterial susceptibility to antibiotics, which could lead to therapeutic failures aggravating the problem of antibiotic resistance. Released putrescine from the extremely antibiotic-resistant bacterium Burkholderia cenocepacia protects less-resistant cells from different species against the antimicrobial peptide polymyxin B (PmB). Exposure of B. cenocepacia to sublethal concentrations of PmB and other bactericidal antibiotics induces reactive oxygen species (ROS) production and expression of the oxidative stress response regulator OxyR. We evaluated whether putrescine alleviates antibiotic-induced oxidative stress. The accumulation of intracellular ROS, such as superoxide ion and hydrogen peroxide, was assessed fluorometrically with dichlorofluorescein diacetate, while the expression of OxyR and putrescine synthesis enzymes was determined in luciferase assays using chromosomal promoter-lux reporter system fusions. We evaluated wild-type and isogenic deletion mutant strains with defects in putrescine biosynthesis after exposure to sublethal concentrations of PmB and other bactericidal antibiotics. Exogenous putrescine protected against oxidative stress induced by PmB and other antibiotics, whereas reduced putrescine synthesis resulted in increased ROS generation and a parallel increased sensitivity to PmB. Of the 3 B. cenocepacia putrescine-synthesizing enzymes, PmB induced only BCAL2641, an ornithine decarboxylase. This study reveals BCAL2641 as a critical component of the putrescine-mediated communication of antibiotic resistance and as a plausible target for designing inhibitors that would block the communication of such resistance among different bacteria, ultimately reducing the window of therapeutic failure in treating bacterial infections

Cognitive analysis of the predisposition of sme leaders to adopt a shared value creation (cvp) strategy : using cognitive mapping

Nouvelle étape de la RSE, la Création de Valeur Partagée s’impose actuellement comme un levier stratégique qui participe à la conciliation entre le business et l’éthique. Elle permet aux entreprises de créer conjointement la valeur économique et sociétale. Si les études académiques ont démontré la pertinence de la CVP dans des grandes entreprises, son utilité dans le contexte des PME reste à prouver. Dans le cadre de cette thèse nous proposons de confronter le cadre théorique du concept de la Création de Valeur Partagée élaboré par M. Porter et M. Kramer (2011) à la réalité des PME Françaises. Il s’agit de répondre aux questions suivantes : Comment les dirigeants de PME perçoivent-ils la Création de Valeur Partagée? Dans quelle mesure la mise en place de la Création de Valeur Partagée passe-t-elle par les trois leviers identifiés par Porter et Kramer à savoir : La nouvelle conception des produits, services et marchés ; la redéfinition de la productivité dans la chaine de valeur et enfin, la participation au développement d’un pôle de compétitivité local ? Les spécificités des PME et les caractéristiques de leurs dirigeants influencent-elles le choix et la pertinence d’un levier par rapport aux autres? Dans cette recherche, nous utilisons la technique de la cartographie cognitive pour analyser et modéliser les représentations mentales des dirigeants de PME interrogés sur le concept de la Création de Valeur Partagée. La typologie élaborée démontre que si les PME participent à la Création de la Valeur Partagée, les leviers stratégiques choisis sont déterminés par la spécificité de la PME et du type de son dirigeant. Cette thématique ouvre un potentiel de recherche riche et intéressant pour le milieu académique comme pour le milieu des affaires.A new stage in CSR, Creating Shared Value (CSV) is a strategic lever that allows reconciliation between business and ethics. It enables companies to create both economic and societal value. Although academic research has demonstrated the relevance of CSV in big companies, its usefulness in the context of SMEs remains to be proven. In this thesis we propose to confront the theoretical framework of the concept of CSV developed by M. Porter and M. Kramer (2011) with the reality of French SMEs. The following questions are examined: 1) How do SME leaders perceive Creating Shared Value? 2) How does the implementation of CSV include the three levers cited by Porter and Kramer, namely: New development of products, services and markets; the redefinition of productivity in the value chain, and the development of a local competitiveness cluster? 3) And finally: how do the specificities of SMEs and the characteristics of their leaders influence the choice and the relevance of one lever as opposed to another one? In this research, we use the technique of cognitive mapping to model and analyze the mental representations of SME managers that have been interviewed on the theme of CSV. The typology used shows that if SMEs participate in Creating Shared Value the strategic levers chosen by them are determined by the SME specificity and by the type of its manager. This theme opens up a rich and interesting research potential for both academic and business communities