A computational study of Anthracyclines interacting with lipid bilayers: Correlation of membrane insertion rates, orientation effects and localisation with cytotoxicity.

Anthracyclines interact with DNA and topoisomerase II as well as with cell membranes, and it is these latter interactions that can cause an increase in their cytotoxic activity. In the present study a detailed computational analysis of the initial insertion, orientation and nature of the interaction occurring between Anthracyclines and two different lipid bilayers (unsaturated POPC and saturated DMPC) is explored through molecular dynamics (MD) simulations; four Anthracyclines: Doxorubicin (DOX), Epirubicin (EPI), Idarubicin (IDA) and Daunorubicin (DAU) were examined. The results indicate that the increased cytotoxicity of DOX, in comparison to the other three analogues, is correlated with its ability to diffuse at a faster rate into the bilayers. Additionally, DOX exhibited considerably different orientational behaviour once incorporated into the bilayer and exhibited a higher propensity to interact with the hydrocarbon tails in both lipids indicating a higher probability of transport to the other leaflet of the bilayer.

Current and future treatment options for community-associated MRSA infection.

INTRODUCTION: Community-associated MRSA (CA-MRSA) represents a global epidemic which beautifully encapsulates the fascinating ability of bacterial organisms to adapt quickly on an evolutionary basis to the extreme selective pressure of antibiotic exposure. In stark contrast to Healthcare-associated MRSA (HA-MRSA), it has become apparent that CA-MRSA is less straight forward of a challenge in terms of controlling its transmission, and has forced clinicians to adjust empiric management of clinical syndromes such as skin and soft tissue infection (SSTI) as well as pneumonia. AREAS COVERED: This review details the history and epidemiology of CA-MRSA, while covering both current and future treatment options that are and may be available to clinicians. The authors reviewed both historic and more recent literature on this ever-evolving topic. EXPERT OPINION: While development of new anti-MRSA agents should be encouraged, the importance of antimicrobial stewardship in the battle to stay ahead of the curve with regards to the ongoing control of the MRSA epidemic should be emphasised.

Future trends in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection: An in-depth review of newer antibiotics active against an enduring pathogen.

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a major public health problem. Vancomycin and teicoplanin have been in clinical use for several decades but their drawbacks are well described. In the last 10 years, several antibiotics have been made available for clinical use. Daptomycin and linezolid have been extensively used during this period. Other agents such as ceftaroline, ceftobiprole, dalbavancin, oritavancin, tedizolid and telavancin have been approved by regulatory agencies since 2009. Many others, such as the newer tetracyclines, fluoroquinolones, oxazolidinones and pleuromutilins, are in various stages of development. In addition, an ongoing multicentre trial is investigating the role of combination of vancomycin or daptomycin with ß-lactam antibiotics. This review discusses the role of the newer antibiotics, reflecting the views of the 6th MRSA Consensus Conference meeting of the International Society of Chemotherapy MRSA Working Group that took place in 2016.

Antibiotic stewardship in low- and middle-income countries: the same but different?

BACKGROUND: Antibiotic resistance (ABR) is a quickly worsening problem worldwide, also in low- and middle-income countries (LMICs). Appropriate antibiotic use in humans and animals, i.e. antibiotic stewardship (ABS), is one of the cornerstones of the World Health Organization's global action plan for ABR. Many LMICs are in the process of developing stewardship programs. AIMS: We highlight challenges for ABS initiatives in LMICs, give an outline of (inter)national recommendations and demonstrate examples of effective, contextualized stewardship interventions. SOURCES: We searched PubMed for articles on ABS interventions in humans in LMICs. Relevant websites and experts were consulted for additional sources. CONTENT: Evidence on effective and feasible stewardship interventions in LMICs is limited, and challenges for implementation of interventions are numerous. Nevertheless, several initiatives at the international and local levels in Latin America, Africa and Asia have shown that ABS effective interventions are feasible in LMICs, although contextualization is essential. IMPLICATIONS: Specific guidance for setting up antimicrobial stewardship programs in LMICs should be developed. Strategic points might need to be progressively addressed in LMICs, such as (a) ensuring availability of diagnostic testing, (b) providing dedicated education in ABR both for healthcare workers and the general public, (c) creating or strengthening (inter)national agencies towards better regulations and audit on production, distribution and dispensing of drugs, (d) strengthening healthcare facilities, (e) exploring a broader synergism between policy makers, academia, professional bodies and civil society and (f) designing and studying easy and scalable ABS interventions for both hospital and community settings.

Engineering plant membranes using droplet interface bilayers.

Droplet interface bilayers (DIBs) have become widely recognised as a robust platform for constructing model membranes and are emerging as a key technology for the bottom-up assembly of synthetic cell-like and tissue-like structures. DIBs are formed when lipid-monolayer coated water droplets are brought together inside a well of oil, which is excluded from the interface as the DIB forms. The unique features of the system, compared to traditional approaches (e.g., supported lipid bilayers, black lipid membranes, and liposomes), is the ability to engineer multi-layered bilayer networks by connecting multiple droplets together in 3D, and the capability to impart bilayer asymmetry freely within these droplet architectures by supplying droplets with different lipids. Yet despite these achievements, one potential limitation of the technology is that DIBs formed from biologically relevant components have not been well studied. This could limit the reach of the platform to biological systems where bilayer composition and asymmetry are understood to play a key role. Herein, we address this issue by reporting the assembly of asymmetric DIBs designed to replicate the plasma membrane compositions of three different plant species; Arabidopsis thaliana, tobacco, and oats, by engineering vesicles with different amounts of plant phospholipids, sterols and cerebrosides for the first time. We show that vesicles made from our plant lipid formulations are stable and can be used to assemble asymmetric plant DIBs. We verify this using a bilayer permeation assay, from which we extract values for absolute effective bilayer permeation and bilayer stability. Our results confirm that stable DIBs can be assembled from our plant membrane mimics and could lead to new approaches for assembling model systems to study membrane translocation and to screen new agrochemicals in plants.

The Parasol Protocol for computational mutagenesis.

To aid in the discovery and development of peptides and proteins as therapeutic agents, a virtual screen can be used to predict trends and direct workflow. We have developed the Parasol Protocol, a dynamic method implemented using the AMBER MD package, for computational site-directed mutagenesis. This tool can mutate between any pair of amino acids in a computationally expedient, automated manner. To demonstrate the potential of this methodology, we have employed the protocol to investigate a test case involving stapled peptides, and have demonstrated good agreement with experiment.

An international cross-sectional survey of antimicrobial stewardship programmes in hospitals.

OBJECTIVES: To report the extent and components of global efforts in antimicrobial stewardship (AMS) in hospitals. METHODS: An Internet-based survey comprising 43 questions was disseminated worldwide in 2012. RESULTS: Responses were received from 660 hospitals in 67 countries: Africa, 44; Asia, 50; Europe, 361; North America, 72; Oceania, 30; and South and Central America, 103. National AMS standards existed in 52% of countries, 4% were planning them and 58% had an AMS programme. The main barriers to implementing AMS programmes were perceived to be a lack of funding or personnel, a lack of information technology and prescriber opposition. In hospitals with an existing AMS programme, AMS rounds existed in 64%; 81% restricted antimicrobials (carbapenems, 74.3%; quinolones, 64%; and cephalosporins, 58%); and 85% reported antimicrobial usage, with 55% linking data to resistance rates and 49% linking data to infection rates. Only 20% had electronic prescribing for all patients. A total of 89% of programmes educated their medical, nursing and pharmacy staff on AMS. Of the hospitals, 38% had formally reviewed their AMS programme: reductions were reported by 96% of hospitals for inappropriate prescribing, 86% for broad-spectrum antibiotic use, 80% for expenditure, 71% for healthcare-acquired infections, 65% for length of stay or mortality and 58% for bacterial resistance. CONCLUSIONS: The worldwide development and implementation of AMS programmes varies considerably. Our results should inform and encourage the further evaluation of this with a view to promoting a worldwide stewardship framework. The prospective measurement of well-defined outcomes of the impact of these programmes remains a significant challenge.

A cross-sectional survey of antimicrobial stewardship strategies in UK hospitals.

WHAT IS KNOWN AND OBJECTIVE: Antimicrobial stewardship programmes describe strategies to optimize antimicrobial prescribing and utilization, minimize resistance and improve patient outcomes. Strategies in hospitals are usually implemented by multidisciplinary antimicrobial teams (AMTs). The objective of this study was to describe the profile and activities of AMTs within hospitals in the United Kingdom (UK). METHOD: All hospitals within the UK (n = 836) were included, and a prepiloted questionnaire was mailed to the 'Director of Pharmacy'. Non-respondents were mailed up to two reminder questionnaires at two-weekly intervals. Main outcome measures are as follows: existence and remit of the AMTs; availability of antimicrobial-prescribing policies, aims, scope and methods of dissemination; and monitoring and feedback provided on antimicrobial policy adherence. RESULTS: Response rate was 33% (n = 273). Completed questionnaires analysed were n = 226. Eighty-two (n = 186) of respondents indicated the presence of an AMT within the hospital, with 95% of these (n = 177) reporting an antimicrobial pharmacist as part of the team. All AMTs (n = 186) were involved in development of an antimicrobial policy and almost all (99% n = 184) promoted adherence and restricting use of specific antimicrobials (97% n = 180). Ninety-eight per cent of respondents (n = 222) reported the availability of a local antimicrobial-prescribing policy within the hospital with this disseminated mainly through the hospital intranet (98% n = 217). Adherence to policy was measured mainly through audits measuring the appropriateness of antimicrobial use against the local policy (76% n = 169). Hospitals in England (P = 0·010), tertiary care hospitals (P = 0·021) and bed capacity >500 (P < 0·001) were more likely to have an AMT, as were hospitals with an accident and emergency department (P < 0·001), an infectious diseases unit (P = 0·019) and a microbiology department (P < 0·001). Audits to measure policy adherence were more likely (P < 0·001) if an AMT was present. The only variable retained in bivariate logistic regression was the presence of a microbiology unit, with an odds ratio of 14·1 (95% CI 6·02-33·33, P < 0·001). WHAT IS NEW AND CONCLUSIONS: Although most respondents reported an antimicrobial-prescribing policy, less had an AMT. Despite recent government and regional initiatives, further improvements in antimicrobial stewardship are still required.

MDRO Beijing Consensus Meeting Report: Global burden of multidrug-resistant organisms' current antimicrobial resistance problems in Asia-Pacific.

The International Society of Chemotherapy's Working Groups on Antibiotic Resistance and Antibiotic Stewardship convened a half-day workshop on the burden of multidrug-resistant organisms in the Asia-Pacific. This short review is a summary of their discussion and conclusions.

Treatment options for methicillin-resistant Staphylococcus aureus (MRSA) infection: Where are we now?

Methicillin-resistant Staphylococcus aureus (MRSA) infection continues to be a substantial global problem with significant associated morbidity and mortality. This review summarises the discussions that took place at the 4th MRSA Consensus Conference in relation to the current treatment options for serious MRSA infections and how to optimise whichever therapy is embarked upon. It highlights the many challenges faced by both the laboratory and clinicians in the diagnosis and treatment of MRSA infections.

Cerebral microcirculation and oxygen tension in the human secondary cortex.

The three-dimensional spatial arrangement of the cortical microcirculatory system is critical for understanding oxygen exchange between blood vessels and brain cells. A three-dimensional computer model of a 3 × 3 × 3 mm(3) subsection of the human secondary cortex was constructed to quantify oxygen advection in the microcirculation, tissue oxygen perfusion, and consumption in the human cortex. This computer model accounts for all arterial, capillary and venous blood vessels of the cerebral microvascular bed as well as brain tissue occupying the extravascular space. Microvessels were assembled with optimization algorithms emulating angiogenic growth; a realistic capillary bed was built with space filling procedures. The extravascular tissue was modeled as a porous medium supplied with oxygen by advection-diffusion to match normal metabolic oxygen demand. The resulting synthetic computer generated network matches prior measured morphometrics and fractal patterns of the cortical microvasculature. This morphologically accurate, physiologically consistent, multi-scale computer network of the cerebral microcirculation predicts the oxygen exchange of cortical blood vessels with the surrounding gray matter. Oxygen tension subject to blood pressure and flow conditions were computed and validated for the blood as well as brain tissue. Oxygen gradients along arterioles, capillaries and veins agreed with in vivo trends observed recently in imaging studies within experimental tolerances and uncertainty.

Treatment of bacteraemia: meticillin-resistant Staphylococcus aureus (MRSA) to vancomycin-resistant S. aureus (VRSA).

Around the world, Staphylococcus aureus remains a dominant cause of bacteraemia. Whilst meticillin resistance remains the major phenotype of concern, various levels of reduced glycopeptide susceptibility are emerging with increasing frequency. The most common MRSA phenotypes now have raised vancomycin MICs within the susceptible range (MICs of 1-2mg/L). This phenomenon, known as MIC creep, is hotly contested and often denied. Key to detecting MIC creep may be to examine isolates fresh, as freezing can allow reversion to wild-type MIC, presumably by loss of mutations. Treatment failure is common with vancomycin and it is uncertain whether higher doses are beneficial. At the other extreme, when enough mutations have accumulated, full VISA status is achieved, although this can also be unstable on storage. Heteroresistant and VISA strains can be considered the inevitable end result of continued MIC creep and are even more likely to fail glycopeptide treatment. Currently full vancomycin resistance is uncommon, with only approximately 20 strains described and confirmed worldwide. Empirical treatment for patients with undefined Gram-positive sepsis can undoubtedly be improved by knowledge of MRSA status, so this is a potential advantage of hospital admission screening. If a patient is risk-assessed or screen-positive for MRSA, and infection is not serious, then vancomycin or teicoplanin is appropriate empirical therapy, providing loading doses are given to achieve therapeutic concentrations immediately (trough 15 mg/L). For life-threatening infections, the glycopeptides are inadequate unless the isolate is likely to be fully susceptible (Etest<1.5mg/L). If not, daptomycin (8-10mg/L) can be used as monotherapy but the MIC should be measured as soon as possible.

Vancomycin in the treatment of meticillin-resistant Staphylococcus aureus (MRSA) infection: End of an era?

Infection with meticillin-resistant Staphylococcus aureus (MRSA) continues to have significant morbidity and mortality. Vancomycin, which has been the mainstay of treatment of invasive MRSA infections, has several drawbacks related to its pharmacological properties as well as varying degrees of emerging resistance. These resistant subpopulations are difficult to detect, making therapy with vancomycin less reliable. The newer agents such as linezolid, daptomycin, ceftaroline, and the newer glycopeptides telavancin and oritavancin are useful alternatives that could potentially replace vancomycin in the treatment of certain conditions. By summarising the discussions that took place at the III MRSA Consensus Conference in relation to the current place of vancomycin in therapy and the potential of the newer agents to replace vancomycin, this review focuses on the challenges faced by the laboratory and by clinicians in the diagnosis and treatment of MRSA infections.

Antimicrobial stewardship: lessons from human healthcare.

This paper focuses on antimicrobial stewardshipin human healthcare, and some concepts possibly transferable to veterinary medicine. Antimicrobial stewardship is a multidisciplinary effort to reduce antimicrobial resistance in human pathogens, when future drug development is dwindling. These strategies encourage healthcare staff to use antimicrobials prudently and, when needed, for as short a duration and with as narrow a spectrum as possible. Various methods are involved in stewardship within the healthcare setting, often implemented simultaneously, which sometimes makes evaluation of specific measures difficult. All healthcare workers must accept responsibility for stewardship, although the role of infectious diseases physicians, microbiologists, pharmacists and infection control practitioners is crucial, as are appropriate surveillance systems and information technology. Support from management and government is also beneficial. Considering the frequent use of antimicrobials in animals, it would seem sensible to apply a similarly critical approach to conserve the efficacy of the antimicrobials still available, now and in the future.

Combination antimicrobial susceptibility testing of multidrug-resistant Stenotrophomonas maltophilia from cystic fibrosis patients.

Stenotrophomonas maltophilia is increasingly being isolated from the respiratory tract of individuals with cystic fibrosis, and, because of its multidrug-resistant nature, the selection of suitable treatment regimens can be problematical. Etest methodology was used to facilitate MIC and antimicrobial combination testing on 80 isolates of S. maltophilia cultured from the respiratory tract of Scottish individuals with cystic fibrosis between 2001 and 2010. The overall rate of susceptibility for the 1,410 MIC tests was 23.1%, and resistance was 68.9%. The most active antimicrobials were minocycline, co-trimoxazole, and doxycycline, with 92.4%, 87.3%, and 58.8% of isolates being susceptible, respectively. Of the 517 combinations, 13.2% were synergistic, with the most synergistic being ticarcillin/clavulanate plus aztreonam (91.7% synergistic), ticarcillin/clavulanate plus colistin (40%), and ticarcillin/clavulanate plus levofloxacin (19.4%). Colistin plus tobramycin was the only antagonistic combination (0.2%). By the median susceptible breakpoint index, the most active combinations were minocycline plus co-trimoxazole (median index, 20), minocycline plus piperacillin-tazobactam (median, 20), and co-trimoxazole plus ceftazidime (median, 16.5). The increasing problem of multidrug resistance in organisms recovered from the respiratory tracts of individuals with cystic fibrosis is not going to go away. Current susceptibility testing methods do not address the slow-growing organisms associated with chronic infection, and interpretive standards are based on achievable blood levels of antimicrobials. Addressing these issues specifically for organisms recovered from the respiratory tracts of individuals with cystic fibrosis should lead to better therapeutic outcomes and improved wellbeing of individuals with cystic fibrosis.