Bacterial membrane activity of α-peptide/β-peptoid chimeras: Influence of amino acid composition and chain length on the activity against different bacterial strains

<p>Abstract</p> <p>Background</p> <p>Characterization and use of antimicrobial peptides (AMPs) requires that their mode of action is determined. The interaction of membrane-active peptides with their target is often established using model membranes, however, the actual permeabilization of live bacterial cells and subsequent killing is usually not tested. In this report, six α-peptide/β-peptoid chimeras were examined for the effect of amino acid/peptoid substitutions and chain length on the membrane perturbation and subsequent killing of food-borne and clinical bacterial isolates.</p> <p>Results</p> <p>All six AMP analogues inhibited growth of twelve food-borne and clinical bacterial strains including Extended Spectrum Beta-Lactamase-producing <it>Escherichia coli</it>. In general, the Minimum Inhibitory Concentrations (MIC) against Gram-positive and -negative bacteria were similar, ranging from 1 to 5 μM. The type of cationic amino acid only had a minor effect on MIC values, whereas chain length had a profound influence on activity. All chimeras were less active against <it>Serratia marcescens </it>(MICs above 46 μM). The chimeras were bactericidal and induced leakage of ATP from <it>Staphylococcus aureus </it>and <it>S. marcescens </it>with similar time of onset and reduction in the number of viable cells. EDTA pre-treatment of <it>S. marcescens </it>and <it>E. coli </it>followed by treatment with chimeras resulted in pronounced killing indicating that disintegration of the Gram-negative outer membrane eliminated innate differences in susceptibility. Chimera chain length did not influence the degree of ATP leakage, but the amount of intracellular ATP remaining in the cell after treatment was influenced by chimera length with the longest analogue causing complete depletion of intracellular ATP. Hence some chimeras caused a complete disruption of the membrane, and this was parallel by the largest reduction in number of viable bacteria.</p> <p>Conclusion</p> <p>We found that chain length but not type of cationic amino acid influenced the antibacterial activity of a series of synthetic α-peptide/β-peptoid chimeras. The synthetic chimeras exert their killing effect by permeabilization of the bacterial cell envelope, and the outer membrane may act as a barrier in Gram-negative bacteria. The tolerance of <it>S. marcescens </it>to chimeras may be due to differences in the composition of the lipopolysaccharide layer also responsible for its resistance to polymyxin B.</p

Development and field-testing of the Dementia Carer Assessment of Support Needs Tool (DeCANT)

Objectives:Caring for a person with dementia is associated with poor mental, physical, and social health, which makes it important to consider how carers are best supported in their caring role to preserve both their and the person with dementia's well-being. At present, a robust instrument to assess carers' support needs does not exist. This study aimed to develop a self-reported questionnaire to assess the support needs of carers of people with dementia. The objectives were to: (1) generate items, (2) pilot test, and (3) field-test the questionnaire.Design:Development and field-testing of a new questionnaire.Settings:Primary and secondary health and social care of informal carers and people with dementia in nine municipalities and one dementia clinic in a hospital in Denmark.Participants:Eight experts, 12 carers, and 7 digital users participated in pilot testing. 301 carers participated in field-testing.Measurements:Items for inclusion were generated based on interviews and literature review. An iterative process of data collection was applied to establish face and content validity of the Dementia Carer Assessment of Support Needs Tool (DeCANT) using Content Validity Index among experts and cognitive interviews with carers. Field-testing of DeCANT among carers included using the 12-item Short Form Health Survey, the Barthel-20 Index, and the Neuropsychiatric Inventory.Results:Initially, an item pool of 63 items was generated, and pilot testing reduced this to 42 items. Subsequent field-testing resulted in a 25-item version of DeCANT, and confirmatory factor analysis of three hypothesized models demonstrated a marginally better fit to a four-factor model with fit indices of: χ2 = 775.170 (p &lt; 0.001), root mean square error of approximation = 0.073, Comparative Fit Index = 0.946, the Tucker-Lewis Index = 0.938, and weighted root mean residual (WRMR) = 1.265.Conclusions:DeCANT is a 25-item carer-reported questionnaire that can be used to help identify their support needs when caring for a person with dementia to enable supportive interventions and improve carers' health and well-being. </p

Translation, Cultural Adaptation, and Psychometric Properties of the Danish Version of the Anti-Clot Treatment Scale

Background The Anti-Clot Treatment Scale (ACTS) is a 17-item, 2-factor (Burdens and Benefits), patient-reported outcome instrument to evaluate patient satisfaction with oral anticoagulant treatment.Objectives This study aimed to translate and culturally adapt the English version of the ACTS into Danish and to subsequently validate the Danish version in a population of patients treated with dabigatran etexilate for atrial fibrillation.Methods The ACTS was translated into Danish and culturally adapted. This prospective phase 4 study included 232 respondents who completed the Danish ACTS after 1 month of treatment with dabigatran etexilate for atrial fibrillation. Psychometric properties were evaluated. For test–retest reliability, the ACTS was measured twice, 2 weeks apart, in a subgroup of 50 stable patients.Results Generally, a high level of treatment satisfaction was found. Confirmatory factor analysis showed a suboptimal fit for the two-factor model of the original version. Using modification indices of confirmatory factor analysis, a four-factor model had the best fit. Cronbach’s α for internal consistency was acceptable at 0.78. There was good test–retest reliability with intraclass correlation at 0.80. Smallest detectable changes (SDCs) for individual patients were 5.89 points for the total ACTS, 5.57 for the reverse Burdens, and 3.34 for Benefits scores. Group SDCs were 0.39, 0.37, and 0.22 respectively. Substantial ceiling effects limit the ability to detect improvement at the high end of the scale.Conclusion The Danish version of the ACTS has inadequate structural validity.Reliability was acceptable. Ceiling effects challenge detection of improvement oftreatment satisfaction in clinical practice in this patient population.Background The Anti-Clot Treatment Scale (ACTS) is a 17-item, 2-factor (Burdens and Benefits), patient-reported outcome instrument to evaluate patient satisfaction with oral anticoagulant treatment.Objectives This study aimed to translate and culturally adapt the English version of the ACTS into Danish and to subsequently validate the Danish version in a population of patients treated with dabigatran etexilate for atrial fibrillation.Methods The ACTS was translated into Danish and culturally adapted. This prospective phase 4 study included 232 respondents who completed the Danish ACTS after 1 month of treatment with dabigatran etexilate for atrial fibrillation. Psychometric properties were evaluated. For test–retest reliability, the ACTS was measured twice, 2 weeks apart, in a subgroup of 50 stable patients.Results Generally, a high level of treatment satisfaction was found. Confirmatory factor analysis showed a suboptimal fit for the two-factor model of the original version. Using modification indices of confirmatory factor analysis, a four-factor model had the best fit. Cronbach’s α for internal consistency was acceptable at 0.78. There was good test–retest reliability with intraclass correlation at 0.80. Smallest detectable changes (SDCs) for individual patients were 5.89 points for the total ACTS, 5.57 for the reverse Burdens, and 3.34 for Benefits scores. Group SDCs were 0.39, 0.37, and 0.22 respectively. Substantial ceiling effects limit the ability to detect improvement at the high end of the scale.Conclusion The Danish version of the ACTS has inadequate structural validity.Reliability was acceptable. Ceiling effects challenge detection of improvement oftreatment satisfaction in clinical practice in this patient population

Adaptive Evolution of Escherichia coli to an α-Peptide/β-Peptoid Peptidomimetic Induces Stable Resistance.

Antimicrobial peptides (AMPs) and synthetic analogues thereof target conserved structures of bacterial cell envelopes and hence, development of resistance has been considered an unlikely event. However, recently bacterial resistance to AMPs has been observed, and the aim of the present study was to determine whether bacterial resistance may also evolve against synthetic AMP analogues, e.g. α-peptide/β-peptoid peptidomimetics. E. coli ATCC 25922 was exposed to increasing concentrations of a peptidomimetic (10 lineages), polymyxin B (10 lineages), or MilliQ water (4 lineages) in a re-inoculation culturing setup covering approx. 500 generations. All 10 lineages exposed to the peptidomimetic adapted to 32 × MIC while this occurred for 8 out of 10 of the polymyxin B-exposed lineages. All lineages exposed to 32 × MIC of either the peptidomimetic or polymyxin B had a significantly increased MIC (16-32 ×) to the selection agent. Five transfers (≈ 35 generations) in unsupplemented media did not abolish resistance indicating that resistance was heritable. Single isolates from peptidomimetic-exposed lineage populations displayed MICs against the peptidomimetic from wild-type MIC to 32 × MIC revealing heterogeneous populations. Resistant isolates showed no cross-resistance against a panel of membrane-active AMPs. These isolates were highly susceptible to blood plasma antibacterial activity and were killed when plasma concentrations exceeded ≈ 30%. Notably, MIC of the peptidomimetic against resistant isolates returned to wild-type level upon addition of 25% plasma. Whole-genome sequencing of twenty isolates from four resistant lineages revealed mutations, in murein transglycosylase D (mltD) and outer-membrane proteins, which were conserved within and between lineages. However, no common resistance-conferring mutation was identified. We hypothesise that alterations in cell envelope structure result in peptidomimetic resistance, and that this may occur via several distinct mechanisms. Interestingly, this type of resistance result in a concomitant high susceptibility towards plasma, and therefore the present study does not infer additional concern for peptidomimetics as future therapeutics

Validity and reliability of the Danish version of QUALIDEM

INTRODUCTION: QUALIDEM is a dementia-specific QoL instrument that allows a proxy-based Quality of Life rating in all stages of dementia. It was originally developed in The Netherlands and has later been translated into English and German. This study endeavoured to translate, cross-culturally adapt and test important psychometric properties of a Danish version in a cross-sectional validation study with a nested test-retest design.METHOD: All items underwent forward and backward translation by bilingual academics. Persons with dementia were recruited from 28 healthcare units in a Danish municipality. The severity of dementia was determined using a pragmatic approach allowing the site team to trichotomise the disease (mild, moderate-severe and very severe) before scoring the QUALIDEM. Psychometric properties for QUALIDEM were determined for item characteristics, construct validity, internal consistency, test-retest reliability, measurement error and floor and ceiling effects. The study was approved by The Danish Data Protection Agency.RESULTS: A total of 169 persons with dementia, aged 51-103, were included. The construct validity testing showed that the overall proportion of correctly hypothesised correlations was 83%. Testing for internal consistency, Cronbach's α ranged from 0.65 to 0.85 in mild-severe dementia with three out of nine subscales having values below 0.7. For very severe dementia, Cronbach's α ranged from 0.44 to 0.81, with three out of six subscales having insufficient values. For test-retest reliability, the intra-class correlation coefficients ranged from 0.56 to 0.86. The 'scale width' method revealed a marked ceiling effect in all subscales ranging from 30.6% to 87.7%.DISCUSSION: The QUALIDEM was successfully translated and cross-culturally adapted into Danish. Most subscales show acceptable internal consistency and test-retest reliability. However, a substantial measurement error and ceiling effect was present in most subscales.CONCLUSION: With few exceptions, the subscales of the Danish version of QUALIDEM have acceptable validity and reliability. Future research should address the limitations of the ceiling effects.</p