A pleurocidin analogue with greater conformational flexibility, enhanced antimicrobial potency and in vivo therapeutic efficacy.

Antimicrobial peptides (AMPs) are a potential alternative to classical antibiotics that are yet to achieve a therapeutic breakthrough for treatment of systemic infections. The antibacterial potency of pleurocidin, an AMP from Winter Flounder, is linked to its ability to cross bacterial plasma membranes and seek intracellular targets while also causing membrane damage. Here we describe modification strategies that generate pleurocidin analogues with substantially improved, broad spectrum, antibacterial properties, which are effective in murine models of bacterial lung infection. Increasing peptide-lipid intermolecular hydrogen bonding capabilities enhances conformational flexibility, associated with membrane translocation, but also membrane damage and potency, most notably against Gram-positive bacteria. This negates their ability to metabolically adapt to the AMP threat. An analogue comprising D-amino acids was well tolerated at an intravenous dose of 15 mg/kg and similarly effective as vancomycin in reducing EMRSA-15 lung CFU. This highlights the therapeutic potential of systemically delivered, bactericidal AMPs

Temporin L and aurein 2.5 have identical conformations but subtly distinct membrane and antibacterial activities

Frogs such as Rana temporaria and Litoria aurea secrete numerous closely related antimicrobial peptides (AMPs) as an effective chemical dermal defence. Damage or penetration of the bacterial plasma membrane is considered essential for AMP activity and such properties are commonly ascribed to their ability to form secondary amphipathic, α-helix conformations in membrane mimicking milieu. Nevertheless, despite the high similarity in physical properties and preference for adopting such conformations, the spectrum of activity and potency of AMPs often varies considerably. Hence distinguishing apparently similar AMPs according to their behaviour in, and effects on, model membranes will inform understanding of primary-sequence-specific antimicrobial mechanisms. Here we use a combination of molecular dynamics simulations, circular dichroism and patch-clamp to investigate the basis for differing anti-bacterial activities in representative AMPs from each species; temporin L and aurein 2.5. Despite adopting near identical, α-helix conformations in the steady-state in a variety of membrane models, these two AMPs can be distinguished both in vitro and in silico based on their dynamic interactions with model membranes, notably their differing conformational flexibility at the N-terminus, ability to form higher order aggregates and the characteristics of induced ion conductance. Taken together, these differences provide an explanation of the greater potency and broader antibacterial spectrum of activity of temporin L over aurein 2.5. Consequently, while the secondary amphipathic, α-helix conformation is a key determinant of the ability of a cationic AMP to penetrate and disrupt the bacterial plasma membrane, the exact mechanism, potency and spectrum of activity is determined by precise structural and dynamic contributions from specific residues in each AMP sequence

A systematic review and meta-analysis of adjuncts to minimally invasive treatment of urethral stricture in men

Context Urethral stricture disease (USD) is initially managed with minimally invasive techniques such as urethrotomy and urethral dilatation. Minimally invasive techniques are associated with a high recurrence rate, especially in recurrent USD. Adjunctive measures, such as local drug injection, have been used in an attempt to reduce recurrence rates. Objective To systematically review evidence for the efficacy and safety of adjuncts used alongside minimally invasive treatment of USD. Evidence acquisition A systematic review of the literature published between 1990 and 2020 was conducted in accordance with the PRISMA checklist. Evidence synthesis A total of 26 studies were included in the systematic review, from which 13 different adjuncts were identified, including intralesional injection (triamcinolone, n = 135; prednisolone, n = 58; mitomycin C, n = 142; steroid-mitomycin C-hyaluronidase, n = 103, triamcinolone-mitomycin C-N-acetyl cysteine, n = 50; platelet-rich plasma, n = 44), intraluminal instillation (mitomycin C, n = 20; hyaluronic acid and carboxymethylcellulose, n = 70; captopril, n = 37; 192-iridium brachytherapy, n = 10), application via a lubricated catheter (triamcinolone, n = 124), application via a coated balloon (paclitaxel, n = 106), and enteral application (tamoxifen, n = 30; deflazacort, n = 36). Overall, 13 randomised controlled trials were included in the meta-analysis. Use of any adjunct was associated with a lower rate of USD recurrence (odds ratio [OR] 0.37, 95% confidence interval [CI] 0.27–0.50; p < 0.001) compared to no adjunct use. Of all the adjuncts, mitomycin C was associated with the lowest rate of USD recurrence (intralesional injection: OR 0.23, 95% CI 0.11–0.48; p < 0.001; intraluminal injection: OR 0.11, 95% CI 0.02–0.61; p = 0.01). Urinary tract infection (2.9–14%), bleeding (8.8%), and extravasation (5.8%) were associated with steroid injection; pruritis of the urethra (61%) occurred after instillation of captopril; mild gynaecomastia (6.7%) and gastrointestinal side effects (6.7%) were associated with oral tamoxifen. Conclusions Adjuncts to minimally invasive treatment of USD appear to lower the recurrence rate and are associated with a low adjunct-specific complication rate. However, the studies included were at high risk of bias. Mitomycin C is the adjunct supported by the highest level of evidence. Patient summary We reviewed studies on additional therapies (called adjuncts) to minimally invasive treatments for narrowing of the urethra in men. Adjuncts such as mitomycin C injection result in a lower recurrence rate compared to no adjunct use. The use of adjuncts appeared to be safe and complications are uncommon; however, the studies were small and of low quality

Impacts of Metabolism and Organic Acids on Cell Wall Composition and Pseudomonas aeruginosa Susceptibility to Membrane Active Antimicrobials

Reliable antimicrobial susceptibility testing is essential in informing both clinical antibiotic therapy decisions and the development of new antibiotics. Mammalian cell culture media have been proposed as an alternative to bacteriological media, potentially representing some critical aspects of the infection environment more accurately. Here, we use a combination of NMR metabolomics and electron microscopy to investigate the response of Escherichia coli and Pseudomonas aeruginosa to growth in differing rich media to determine whether and how this determines metabolic strategies, the composition of the cell wall, and consequently susceptibility to membrane active antimicrobials including colistin and tobramycin. The NMR metabolomic approach is first validated by characterizing the expected E. coli acid stress response to fermentation and the accompanying changes in the cell wall composition, when cultured in glucose rich mammalian cell culture media. Glucose is not a major carbon source for P. aeruginosa but is associated with a response to osmotic stress and a modest increase in colistin tolerance. Growth of P. aeruginosa in a range of bacteriological media is supported by consumption of formate, an important electron donor in anaerobic respiration. In mammalian cell culture media, however, the overall metabolic strategy of P. aeruginosa is instead dependent on consumption of glutamine and lactate. Formate doping of mammalian cell culture media does not alter the overall metabolic strategy but is associated with polyamine catabolism, remodelling of both inner and outer membranes, and a modest sensitization of P. aeruginosa PAO1 to colistin. Further, in a panel of P. aeruginosa isolates an increase between 2- and 3-fold in sensitivity to tobramycin is achieved through doping with other organic acids, notably propionate which also similarly enhances the activity of colistin. Organic acids are therefore capable of nonspecifically influencing the potency of membrane active antimicrobials

Safety and efficacy of non-steroidal anti-inflammatory drugs to reduce ileus after colorectal surgery

Background: Ileus is common after elective colorectal surgery, and is associated with increased adverse events and prolonged hospital stay. The aim was to assess the role of non-steroidal anti-inflammatory drugs (NSAIDs) for reducing ileus after surgery. Methods: A prospective multicentre cohort study was delivered by an international, student- and trainee-led collaborative group. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The primary outcome was time to gastrointestinal recovery, measured using a composite measure of bowel function and tolerance to oral intake. The impact of NSAIDs was explored using Cox regression analyses, including the results of a centre-specific survey of compliance to enhanced recovery principles. Secondary safety outcomes included anastomotic leak rate and acute kidney injury. Results: A total of 4164 patients were included, with a median age of 68 (i.q.r. 57\u201375) years (54\ub79 per cent men). Some 1153 (27\ub77 per cent) received NSAIDs on postoperative days 1\u20133, of whom 1061 (92\ub70 per cent) received non-selective cyclo-oxygenase inhibitors. After adjustment for baseline differences, the mean time to gastrointestinal recovery did not differ significantly between patients who received NSAIDs and those who did not (4\ub76 versus 4\ub78 days; hazard ratio 1\ub704, 95 per cent c.i. 0\ub796 to 1\ub712; P = 0\ub7360). There were no significant differences in anastomotic leak rate (5\ub74 versus 4\ub76 per cent; P = 0\ub7349) or acute kidney injury (14\ub73 versus 13\ub78 per cent; P = 0\ub7666) between the groups. Significantly fewer patients receiving NSAIDs required strong opioid analgesia (35\ub73 versus 56\ub77 per cent; P &lt; 0\ub7001). Conclusion: NSAIDs did not reduce the time for gastrointestinal recovery after colorectal surgery, but they were safe and associated with reduced postoperative opioid requirement