The visualisation of interactions between Acinetobacter baumannii and the antimicrobial peptides: colistin sulphate, bicarinalin and BP100

It is estimated that there are over 700,000 deaths annually worldwide due to multi-drug resistant (MDR) bacterial infections and by 2050 this is predicted to rise to 10 million. One of these MDR organisms is Acinetobacter baumannii, an opportunistic pathogen implicated in pneumonia, meningitis and septicaemia. It is especially difficult to treat due to its ability to become rapidly resistant to a wide range of antimicrobials and persist due to its ability to form biofilms. Biofilms are sessile communities of bacterial cells, attached to surfaces and embedded within a protective polysaccharide matrix, making them 10-1000 times more resistant than their planktonic form. Antimicrobial peptides (AMPs) are a diverse group of polypeptides that are present in nearly all living things as part of the innate immune system. They are being extensively researched as potential alternatives to classical antibiotics. The objective of this research project was to compare the bactericidal and biofilm activity of two synthetic nature inspired antimicrobial peptides, bicarinalin and BP100, with colistin sulphate. Colistin sulphate is an antimicrobial peptide, currently used as a last resort treatment of A. baumannii infections. The bacteriostatic and bactericidal effects of colistin sulphate, bicarinalin and BP100 on A. baumannii 19606 were assessed using microbiological assays and the consequences of peptide action was visualised on single cells of A. baumannii using atomic force microscopy (AFM). The changes in the roughness and area of the cell surface at increasing peptide concentrations were determined to quantify the effect of the three different peptides. The effect of the peptides on biofilm formation was investigated by determining the minimum biofilm inhibition concentration (MBIC) and on preformed biofilms using the biofilm removal assay. Peptide action on the biofilms was visualised by scanning III electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The nucleic acid stain SYTO9 was used with CLSM to visualise and quantify biofilm bio-volume reduction at increasing concentrations of peptide. Bactericidal results showed concentrations of 0.5 μg/ml for colistin sulphate and 4 μg/ml for both bicarinalin and BP100. Biofilm removal assay results highlighted that at higher concentrations, both bicarinalin and BP100 had significantly greater biofilm removal potential than colistin sulphate. At peptide concentrations of 1024 μg/ml, biofilm reduction was only circa 50% for colistin sulphate but 65% and 83% for the AMPs bicarinalin and BP100 respectively. At 2048 μg/ml, the highest concentration analysed, BP100 eradicated 95% of the biofilm, nearly twice that of colistin. AFM illustrated dramatic changes in cell size and membrane conformity when treated with peptides of concentrations at and above the MBC. SEM images showed the decrease in biofilm presence and cellular changes as peptide concentration increased. CLSM images and bio-volume quantification, with increasing peptide concentrations, further reinforced the evidence that bicarinalin and BP100 were more effective than colistin against A. baumannii biofilms at high concentrations. At a concentration of 1000 μg/ml, bicarinalin and BP100 removed approximately 50-55% of the biofilms, twice as much as colistin, a trend consistent with the biofilm removal assay results. The results demonstrated the potential for AMPs as therapeutic alternatives to the currently used treatment against A. baumannii infections. Compared to colistin sulphate, bicarinalin and BP100 had generally better removal potential against A. baumannii biofilms

Resolving physical interactions between bacteria and nanotopographies with focused ion beam scanning electron microscopy

To robustly assess the antibacterial mechanisms of nanotopographies, it is critical to analyze the bacteria-nanotopography adhesion interface. Here, we utilize focused ion beam milling combined with scanning electron microscopy to generate three-dimensional reconstructions of Staphylococcus aureus or Escherichia coli interacting with nanotopographies. For the first time, 3D morphometric analysis has been exploited to quantify the intrinsic contact area between each nanostructure and the bacterial envelope, providing an objective framework from which to derive the possible antibacterial mechanisms of synthetic nanotopographies. Surfaces with nanostructure densities between 36 and 58 per μm(2) and tip diameters between 27 and 50 nm mediated envelope deformation and penetration, while surfaces with higher nanostructure densities (137 per μm(2)) induced envelope penetration and mechanical rupture, leading to marked reductions in cell volume due to cytosolic leakage. On nanotopographies with densities of 8 per μm(2) and tip diameters greater than 100 nm, bacteria predominantly adhered between nanostructures, resulting in cell impedance

Demographic and socio-economic risk factors associated with self-reported TB

BACKGROUND : The infectiousness of Mycobacterium tuberculosis is known to be shaped by the human environment, with research showing positive associations with poverty, homelessness and overcrowding, among other factors. In this study, the focus is primarily on environmental health risks for TB, particularly on those associated with sociodemographic and household living conditions in South Africa. METHODS : Data for this study were collected between 2014 and 2019 from a number of sites implementing community-oriented primary care (COPC) in the Gauteng Province of the country. Community health workers (CHWs) used AitaHealthtm, a custom-built mobile information management application, to obtain data on the TB status and environmental conditions of households. Statistical models were used to determine associations between various demographic, socio-economic and environmental risk factors, and TB. RESULTS : Approximately 12,503 TB cases were reported among 7,769 households. Substance use and male-headed households were found to have significant associations in households with at least one individual with TB. Overcrowding, as well as lack of access to piped water and adequate sanitation were also found to be positively associated with a 'TB-household. CONCLUSION : Improvements in housing and services, particularly the provision of piped water and reticulated flush toilets, are needed to control and prevent TB in South Africa.https://theunion.org/our-work/journals/ijtldhj2023Family MedicineGeography, Geoinformatics and Meteorolog

Impact of surface topography and coating on osteogenesis and bacterial attachment on titanium implants

Titanium (Ti) plays a predominant role as the material of choice in orthopaedic and dental implants. Despite the majority of Ti implants having long-term success, premature failure due to unsuccessful osseointegration leading to aseptic loosening is still too common. Recently, surface topography modification and biological/non-biological coatings have been integrated into orthopaedic/dental implants in order to mimic the surrounding biological environment as well as reduce the inflammation/infection that may occur. In this review, we summarize the impact of various Ti coatings on cell behaviour both in vivo and in vitro. First, we focus on the Ti surface properties and their effects on osteogenesis and then on bacterial adhesion and viability. We conclude from the current literature that surface modification of Ti implants can be generated that offer both osteoinductive and antimicrobial properties

Optimising the data combination rule for seamless phase II/III clinical trials

We consider seamless Phase II/III clinical trials which compare K treatments with a common control in Phase II, then test the most promising treatment against control in Phase III. The final hypothesis test for the selected treatment can use data from both Phases, subject to controlling the familywise type I error rate. We show that the choice of method for conducting the final hypothesis test has a substantial impact on the power to demonstrate that an effective treatment is superior to control. To understand these differences in power we derive optimal decision rules, maximising power for particular configurations of treatment effects. Rules with optimal frequentist properties are found as solutions to multivariate Bayes decision problems. Although the optimal rule depends on the configuration of treatment means considered, we are able to identify two decision rules with robust efficiency: a rule using a weighted average of the Phase II and Phase III data on the selected treatment and control, and a closed testing procedure using an inverse normal combination rule and a Dunnett test for intersection hypotheses. For the first of these rules, we find the optimal division of a given total sample size between Phase II and Phase III.We also assess the value of using Phase II data in the final analysis and find that for many plausible scenarios, between 50% and 70% of the Phase II numbers on the selected treatment and control would need to be added to the Phase III sample size in order to achieve the same increase in power

Mechanistic and phenotypic studies of bicarinalin, BP100 and colistin action on Acinetobacter baumannii

Acinetobacter baumannii has been identified by the WHO as a high priority pathogen. It can be resistant to multiple antibiotics and colistin sulphate is often used as a last-resort treatment. However, the potentially severe side-effects of colistin are well documented and this study compared the bactericidal and anti-biofilm activity of two synthetic nature-inspired antimicrobial peptides, bicarinalin and BP100, with colistin. The minimum bactericidal concentration (MBC) against planktonic A. baumannii was approximately 0.5 μg/ml for colistin sulphate and ∼4 μg/ml for bicarinalin and BP100. A. baumannii commonly occurs as a biofilm and biofilm removal assay results highlighted that both bicarinalin and BP100 had significantly greater potential than colistin. Atomic force microscopy (AFM) showed dramatic changes in A. baumannii cell size and surface conformity when treated with peptide concentrations at and above the MBC. Scanning electron microscopy (SEM) visualised the reduction of biofilm coverage and cell surface changes as peptide concentration increased. Liposome assays revealed that these peptides most likely act as pore-forming agents in the membrane. Bicarinalin and BP100 may be effective therapeutic alternatives to colistin against A. baumannii infections but further research is required to assess if they elicit cytotoxicity issues in patients

Discourse structure and language technology

This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.An increasing number of researchers and practitioners in Natural Language Engineering face the prospect of having to work with entire texts, rather than individual sentences. While it is clear that text must have useful structure, its nature may be less clear, making it more difficult to exploit in applications. This survey of work on discourse structure thus provides a primer on the bases of which discourse is structured along with some of their formal properties. It then lays out the current state-of-the-art with respect to algorithms for recognizing these different structures, and how these algorithms are currently being used in Language Technology applications. After identifying resources that should prove useful in improving algorithm performance across a range of languages, we conclude by speculating on future discourse structure-enabled technology.Peer Reviewe

Interpreting Mamelodi community-oriented primary care data on tuberculosis loss to follow-up through the lens of intersectionality

BACKGROUND: Tuberculosis (TB) is a persistent major public health challenge in South Africa. This article examines the social determinants and demographic factors associated with TB loss to follow-up through the lens of intersectionality. AIM: The aim of this study was to describe and interpret the social determinants and demographic factors associated with TB patients lost to follow-up (LTFU). SETTING: Mamelodi, an urban settlement in the South African District of Tshwane. METHODS: AitaHealth™ is an Information and Communications Technology (ICT) mobile and web application that is used by community health workers. Data from patients with TB were extracted from the 64 319 households registered on AitaHealth™ over a 3-year period. Univariate and multivariate analyses were used to compare patients who were adherent to TB treatment and those LTFU. RESULTS: Of the 184 351 individuals screened for TB, 788 reported that they were diagnosed with TB (an incidence of 427 cases per 100 000). Of the 704 eligible for inclusion in this analysis, 540 (77%) were on treatment and 164 (23%) were LTFU. The factors associated with LTFU were aged over 60, not having a South African identification document, migration and death in the household, and higher mean household income. Conclusion: The results of this study serve as a reminder to clinicians of the importance of the three-stage assessment (biopsychosocial) in the approach to patients with TB. Understanding the intersection of social determinants and demographic factors helps clinicians and others identify and respond to the specificity of patient, health system and non-health policy issues at play in LTFU.http://www.phcfm.orgpm2021Family Medicin

Enhanced and stem-cell-compatible effects of nature-inspired antimicrobial nanotopography and antimicrobial peptides to combat implant-associated infection

Nature-inspired antimicrobial surfaces and antimicrobial peptides (AMPs) have emerged as promising strategies to combat implant-associated infections. In this study, a bioinspired antimicrobial peptide was functionalized onto a nanospike (NS) surface by physical adsorption with the aim that its gradual release into the local environment would enhance inhibition of bacterial growth. Peptide adsorbed on a control flat surface exhibited different release kinetics compared to the nanotopography, but both surfaces showed excellent antibacterial properties. Functionalization with peptide at micromolar concentrations inhibited Escherichia coli growth on the flat surface, Staphylococcus aureus growth on the NS surface, and Staphylococcus epidermidis growth on both the flat and NS surfaces. Based on these data, we propose an enhanced antibacterial mechanism whereby AMPs can render bacterial cell membranes more susceptible to nanospikes, and the membrane deformation induced by nanospikes can increase the surface area for AMPs membrane insertion. Combined, these effects enhance bactericidal activity. Since functionalized nanostructures are highly biocompatible with stem cells, they make promising candidates for next generation antibacterial implant surfaces