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Modification of the outer membrane charge by a polymyxin B (PMB)-induced PmrAB two-component system appears to be a dominant phenomenon in PMB-resistant Acinetobacter baumannii . PMB-resistant variants and many clinical isolates also appeared to produce outer membrane vesicles (OMVs). Genomic, transcriptomic, and proteomic analyses revealed that upregulation of the pmr operon and decreased membrane-linkage proteins (OmpA, OmpW, and BamE) are linked to overproduction of OMVs, which also promoted enhanced biofilm formation. The addition of OMVs from PMB-resistant variants into the cultures of PMB-susceptible A. baumannii and the clinical isolates protected these susceptible bacteria from PMB. Taxonomic profiling of in vitro human gut microbiomes under anaerobic conditions demonstrated that OMVs completely protected the microbial community against PMB treatment. A Galleria mellonella- infection model with PMB treatment showed that OMVs increased the mortality rate of larvae by protecting A. baumannii from PMB. Taken together, OMVs released from A. baumannii functioned as decoys against PMB. Wrapped in a thick, protective outer membrane, Acinetobacter baumannii bacteria can sometimes cause serious infections when they find their way into human lungs and urinary tracts. Antibiotics are increasingly ineffective against this threat, which forces physicians to resort to polymyxin B, an old, positively-charged drug that ‘sticks’ to the negatively-charged proteins and fatty components at the surface of A. baumannii . Scientists have noticed that when bacteria are exposed to lethal drugs, they often react by releasing vesicles, small ‘sacs’ made of pieces of the outer membranes which can contain DNA or enzymes. How this strategy protects the cells against antibiotics such as polymyxin B remains poorly understood. To investigate this question, Park et al. examined different strains of A. baumannii , showing that bacteria resistant to polymyxin B had lower levels of outer membrane proteins but would release more vesicles. Adding vesicles from resistant strains to non-resistant A. baumannii cultures helped cells to survive the drugs. In fact, this protective effect extended to other species, shielding whole communities of bacteria against polymyxin B. In vivo, the vesicles protected bacteria in moth larvae infected with A. baumannii , leading to a higher death rate in the animals. Experiments showed that the negatively-charged vesicles worked as decoys, trapping the positively-charged polymyxin B away from its target. Taken together, the findings by Park et al. highlight a new strategy that allows certain strains of bacteria to protect themselves from antibiotics, while also benefitting the rest of the microbial community.

Summary GacS/GacA is a conserved two‐component system that functions as a master regulator of virulence‐associated traits in many bacterial pathogens, including Pseudomonas spp., that collectively infect both plant and animal hosts. Among many GacS/GacA‐regulated traits, type III secretion of effector proteins into host cells plays a critical role in bacterial virulence. In the opportunistic plant and animal pathogen Pseudomonas aeruginosa, GacS/GacA negatively regulates the expression of type III secretion system (T3SS)‐encoding genes. However, in the plant pathogenic bacterium Pseudomonas syringae, strain‐to‐strain variation exists in the requirement of GacS/GacA for T3SS deployment, and this variability has limited the development of predictive models of how GacS/GacA functions in this species. In this work we re‐evaluated the function of GacA in P. syringae pv. tomato DC3000. Contrary to previous reports, we discovered that GacA negatively regulates the expression of T3SS genes in DC3000, and that GacA is not required for DC3000 virulence inside Arabidopsis leaf tissue. However, our results show that GacA is required for full virulence of leaf surface‐inoculated bacteria. These data significantly revise current understanding of GacS/GacA in regulating P. syringae virulence.

The virulence of Staphylococcus aureus is essentially determined by cell wall associated proteins and secreted toxins that are regulated and expressed according to growth phases and/or growth conditions. Gene expression is regulated by specific and sensitive mechanisms, most of which act at the transcriptional level. Regulatory factors constitute numerous complex networks, driving specific interactions with target gene promoters. These factors are largely regulated by two-component regulatory systems, such as the agr, saeRS, srrAB, arlSR and lytRS systems. These systems are sensitive to environmental signals and consist of a sensor histidine kinase and a response regulator protein. DNA-binding proteins, such as SarA and the recently identified SarA homologues (SarR, Rot, SarS, SarT, SarU), also regulate virulence factor expression. These homologues might be intermediates in the regulatory networks. The multiple pathways generated by these factors allow the bacterium to adapt to environmental conditions rapidly and specifically, and to develop infection. Precise knowledge of these regulatory mechanisms and how they control virulence factor expression would open up new perspectives for antimicrobial chemotherapy using key inhibitors of these systems.

The Gram-negative opportunistic pathogen Pseudomonas aeruginosa ubiquitously inhabits soil and water habitats and also causes serious, often antibiotic resistant, infections in immunocompromised patients (e.g. cystic fibrosis). This versatility is mediated in part by a large repertoire of two-component regulatory systems that appear instrumental in the regulation of both virulence processes and resistance to antimicrobials. Major two-component regulatory system proteins demonstrated to regulate these diverse processes include PhoP-PhoQ, GacA-GacS, RetS, LadS, and AlgR, among others. Here, we summarize the current body of knowledge of these and other two-component systems that provides insight into the complex regulation of virulence and resistance in P. aeruginosa.

The two-component regulatory system comprised of the sensor kinase, GacS, and its response regulator, GacA, is involved in regulation of secondary metabolism and many other aspects of bacterial physiology. Although it is known that the sensor kinases RetS and LadS feed into the GacS/GacA system, the mechanism through which this occurs is unknown, as are the protein-protein interactions in this system. To characterize and define these interactions, we utilized a bacterial two-hybrid system to study the interactions of GacS and GacA from Pseudomonas fluorescens CHA0. Domains of GacA and GacS, identified through bioinformatics, were subcloned and their ability to interact in vivo was investigated. We found that the entire GacA molecule is required for GacA to interact with itself or GacS. Furthermore, the HisKA/HATPase/REC domains of GacS together are responsible for GacS interacting with GacA, while the HAMP domain of GacS is responsible for GacS interacting with itself. In addition, homologs of Pseudomonas aeruginosa hybrid sensor kinases, RetS and LadS, were identified in P. fluorescens, and shown to interact with GacS, but not GacA.

More than 200 new infrastructure regulators have been created around the world in the last 15 years. They were established to encourage clear and sustainable long-term economic and legal commitments by governments and investors to encourage new investment to benefit existing and new customers. There is now considerable evidence that both investors and consumers—the two groups that were supposed to have benefited from these new regulatory systems—have often been disappointed with their performance. The fundamental premise of this book is that regulatory systems can be successfully reformed only if there are independent, objective and public evaluations of their performance. Just as one goes to a medical doctor for a regular health checkup, it is clear that infrastructure regulation would also benefit from periodic checkups. This book provides a general framework as well as detailed practical guidance on how to perform such “regulatory checkups.”.

Background: Medicines regulators, while performing a vital public health activity, are often perceived as both negative cost centers for governments and as impediments to innovation and economic development. The Mexican government recently undertook a regulatory optimization program focused on transforming the Mexican medicines regulatory pathway into one that is efficient, value-added, aligned with international norms, resource accountable, and one that protects and promotes public health, while also facilitating economic development. Methods: To facilitate the implementation of a new national access to medicines policy, the national government and the Mexican medicines regulatory agency instituted a multifaceted series of regulatory and legal reforms, which are described in this paper. These reforms encompassed multiple aspects of the regulatory oversight of medicines: administrative processes, clinical trials oversight, reliance on market authorization information and reports (ie, “work products”) of other trusted regulators, and validation of activities by both Pan American Health Organization (PAHO) and WHO. Findings: These reforms have resulted in a marked positive impact on the availability of safe, effective, quality medicines at lower costs for Mexicans, both in the private and public sectors, while simultaneously facilitating expansion of the Mexican pharmaceutical industry. Interpretation: The regulatory optimization approach undertaken by Mexico could be a useful model for other countries that are trying to provide appropriate public health protection to their citizens, facilitate access to needed quality medicines, and encourage local economic development.

Background Access to quality-assured, safe and efficacious medical products is fundamental for Universal Health Coverage and attaining Sustainable Development Goal 3: Ensure Healthy Lives and Well-being for All. To guarantee this right, there is a need for robust and efficiently performing national regulatory systems for the regulation of medical products. Well-functioning regulatory systems apply globally accepted standards which ensure that the level of control is proportionate to the level of public health risk. Objective of the study The study aimed at analysing the regulatory systems for medical products in the 16 Member States of the Southern African Development Community (SADC). It provides an overview of the national regulatory systems for medical products in the region in 2017 and outlines the institutional frameworks, which enable the implementation of regulatory functions. Methodology A survey was conducted in March-December 2017 in English, French and Portuguese. National Regulatory Authorities for medical products (NMRAs) of the 16 Member States within SADC responded to the questions asked and sent in their answers. The survey was constructed around five themes instrumental for implementation of the Universal Health Coverage actions framework. Three of the themes are discussed in this article. Results The outcome of the survey demonstrates that within SADC, NMRAs vary in terms of organisational set-up and modalities of medical product regulation. The majority are within the Ministries of Health, and a few are either semi-autonomous or autonomous. Legal frameworks for medical products are in place for some of the SADC NMRAs, although they vary in the scope of products subject to regulation. Traditional medicines, biologicals and medical devices are regulated, however not uniformly across the region. Conclusion Despite major progress over the years, the survey demonstrates variable levels of governance and regulatory framework among NMRAs in SADC. The survey supports the need for shifting from the broad strengthening of the regulatory systems which exist and are underpinned by the mandates, to more product-type focused approaches. This shift will ensure that medical products are quality-assured, safe and effective for a performant Health Systems attainment of the Universal Health Coverage and Sustainable Development Goals.

The classical TCS system in bacterial signal transduction is composed of two proteins—a histidine kinase and its cognate response regulator. More and more studies have revealed the presence of accessory proteins that can modulate the histidine kinase activity and affect signal transduction, but their mechanisms remain largely elusive. This study unveils a previously unrecognized mechanism by which bacterial accessory lipoproteins mediate TCS activation. We provide compelling evidence that QseG directly interacts with QseE through an evolutionarily conserved structural interface, readily and sufficiently activating QseE’s autokinase activity and downstream signaling. Given the essential role of QseEF in bacterial virulence and stress adaptation, our findings pave the way for the development of antimicrobial strategies targeting this conserved lipoprotein-mediated activation mechanism.

Multidrug efflux systems not only cause resistance against antibiotics and toxic compounds but also mediate successful host colonization by certain plant‐associated bacteria. The genome of the nitrogen‐fixing soybean symbiont Bradyrhizobium japonicum encodes 24 members of the family of resistance/nodulation/cell division (RND) multidrug efflux systems, of which BdeAB is genetically controlled by the RegSR two‐component regulatory system. Phylogenetic analysis of the membrane components of these 24 RND‐type transporters revealed that BdeB is more closely related to functionally characterized orthologs in other bacteria, including those associated with plants, than to any of the other 23 paralogs in B. japonicum. A mutant with a deletion of the bdeAB genes was more susceptible to inhibition by the aminoglycosides kanamycin and gentamicin than the wild type, and had a strongly decreased symbiotic nitrogen‐fixation activity on soybean, but not on the alternative host plants mungbean and cowpea, and only very marginally on siratro. The host‐specific role of a multidrug efflux pump is a novel feature in the rhizobia-legume symbioses. Consistent with the RegSR dependency of bdeAB, a B. japonicum regR mutant was found to have a greater sensitivity against the two tested antibiotics and a symbiotic defect that is most pronounced for soybean.