Where bacterial metabolism and virulence intersect

‘We are what we eat’, and so are the bacteria that live on us. If bacteria do not have the building blocks or metabolic pathways and capacity to create their healthy cell, they will be disadvantaged when it comes to establishing an infection

Elastic and Piezoelectric Properties of Boron Nitride Nanotube Composites

This paper is the second part of a two-part series where the first part presents a molecular dynamics model of a single Boron Nitride Nanotube (BNNT) and this paper scales up to multiple BNNTs in a polymer matrix. This paper presents finite element (FE) models to investigate the effective elastic and piezoelectric properties of (BNNT) nanocomposites. The nanocomposites studied in this paper are thin films of polymer matrix with aligned co-planar BNNTs. The FE modelling approach provides a computationally efficient way to gain an understanding of the material properties. We examine several FE models to identify the most suitable models and investigate the effective properties with respect to the BNNT volume fraction and the number of nanotube walls. The FE models are constructed to represent aligned and randomly distributed BNNTs in a matrix of resin using 2D and 3D hollow and 3D filled cylinders. The homogenisation approach is employed to determine the overall elastic and piezoelectric constants for a range of volume fractions. These models are compared with an analytical model based on Mori-Tanaka formulation suitable for finite length cylindrical inclusions. The model applies to primarily single-wall BNNTs but is also extended to multi-wall BNNTs, for which preliminary results will be presented. Results from the Part 1 of this series can help to establish a constitutive relationship for input into the finite element model to enable the modeling of multiple BNNTs in a polymer matrix

LuxS-independent formation of AI-2 from ribulose-5-phosphate

<p>Abstract</p> <p>Background</p> <p>In many bacteria, the signal molecule AI-2 is generated from its precursor <it>S</it>-ribosyl-L-homocysteine in a reaction catalysed by the enzyme LuxS. However, generation of AI-2-like activity has also been reported for organisms lacking the <it>luxS </it>gene and the existence of alternative pathways for AI-2 formation in <it>Escherichia coli </it>has recently been predicted by stochastic modelling. Here, we investigate the possibility that spontaneous conversion of ribulose-5-phosphate could be responsible for AI-2 generation in the absence of <it>luxS</it>.</p> <p>Results</p> <p>Buffered solutions of ribulose-5-phosphate, but not ribose-5-phosphate, were found to contain high levels of AI-2 activity following incubation at concentrations similar to those reported <it>in vivo</it>. To test whether this process contributes to AI-2 formation by bacterial cells <it>in vivo</it>, an improved <it>Vibrio harveyi </it>bioassay was used. In agreement with previous studies, culture supernatants of <it>E. coli </it>and <it>Staphylococcus aureus luxS </it>mutants were found not to contain detectable levels of AI-2 activity. However, low activities were detected in an <it>E. coli pgi-eda-edd-luxS </it>mutant, a strain which degrades glucose entirely via the oxidative pentose phosphate pathway, with ribulose-5-phosphate as an obligatory intermediate.</p> <p>Conclusion</p> <p>Our results suggest that LuxS-independent formation of AI-2, via spontaneous conversion of ribulose-5-phosphate, may indeed occur <it>in vivo</it>. It does not contribute to AI-2 formation in wildtype <it>E. coli </it>and <it>S. aureus </it>under the conditions tested, but may be responsible for the AI-2-like activities reported for other organisms lacking the <it>luxS </it>gene.</p

AI-2 does not function as a quorum sensing molecule in Campylobacter jejuni during exponential growth in vitro

<p>Abstract</p> <p>Background</p> <p><it>Campylobacter jejuni </it>contains a homologue of the <it>luxS </it>gene shown to be responsible for the production of the signalling molecule autoinducer-2 (AI-2) in <it>Vibrio harveyi </it>and <it>Vibrio cholerae</it>. The aim of this study was to determine whether AI-2 acted as a diffusible quorum sensing signal controlling <it>C. jejuni </it>gene expression when it is produced at high levels during mid exponential growth phase.</p> <p>Results</p> <p>AI-2 activity was produced by the parental strain NCTC 11168 when grown in rich Mueller-Hinton broth (MHB) as expected, but interestingly was not present in defined Modified Eagles Medium (MEM-α). Consistent with previous studies, the <it>luxS </it>mutant showed comparable growth rates to the parental strain and exhibited decreased motility halos in both MEM-α and MHB. Microarray analysis of genes differentially expressed in wild type and <it>luxS </it>mutant strains showed that many effects on mRNA transcript abundance were dependent on the growth medium and linked to metabolic functions including methionine metabolism. Addition of exogenously produced AI-2 to the wild type and the <it>luxS </it>mutant, growing exponentially in either MHB or MEM-α did not induce any transcriptional changes as analysed by microarray.</p> <p>Conclusion</p> <p>Taken together these results led us to conclude that there is no evidence for the role of AI-2 in cell-to-cell communication in <it>C. jejuni </it>strain NCTC 11168 under the growth conditions used, and that the effects of the <it>luxS </it>mutation on the transcriptome are related to the consequential loss of function in the activated methyl cycle.</p

Improving children’s and their visitors’ hand hygiene compliance

Background: Numerous interventions have tried to improve healthcare workers' hand hygiene compliance, however little attention has been paid to children's and their visitors’ compliance.Aim: To increase children’s and visitors’ compliance using interactive educational interventions. Methods: This was an observational study of hand hygiene compliance before and after the introduction of educational interventions. Qualitative data in the form of Questionnaires and interviews was obtained.Findings: Hand hygiene compliance increased by 21.4% (P [less than] 0.001) following the educational interventions, with children's compliance reaching 40.8% and visitors' being 50.8%. Compliance varied depending on which of the five moments of hygiene was observed (P [less than] 0.001), with the highest compliance was ‘after body fluid exposure’ (96%). Responses from questionnaires showed educational interventions raised awareness of the importance of hand hygiene (69%, 57%) compared to those who hadn't experienced the educational intervention (50%). Conclusion: Educational interventions may result in a significant increase in children's and visitors' hand hygiene (P [less than] 0.001)

JMM profile: rifampicin: a broad-spectrum antibiotic

Rifampicin (also known as rifampin) inhibits RNA synthesis, and is used to treat tuberculosis, leprosy, staphylococcal infections and legionnaires' disease. It can also protect at-risk populations from Haemophilus influenzae type b and Neisseria meningitidis. It is a polyketide antibiotic and is on the World Health Organization (WHO) list of essential medicines due to its critical importance to human medicine. The adverse effect of liver toxicity is controlled by testing during prolonged treatment regimes. Rifampicin's red-orange colour can result in the colouration of sweat, tears and urine. Resistance to rifampicin arises from mutation of the target RNA polymerase or ADP ribosylation of the antibiotic or efflux. Mycobacteria may become singularly resistant to rifampicin or as part of multidrug or extensive drug resistance

Hybrid Poly(<i>β</i>‐amino ester) Triblock Copolymers Utilizing a RAFT Polymerization Grafting‐From Methodology

The biocompatibility, biodegradability, and responsiveness of poly(β‐amino esters) (PBAEs) has led to their widespread use as biomaterials for drug and gene delivery. Nonetheless, the step‐growth polymerization mechanism that yields PBAEs limits the scope for their structural optimization toward specific applications because of limited monomer choice and end‐group modifications. Moreover, to date the post‐synthetic functionalization of PBAEs has relied on grafting‐to approaches, challenged by the need for efficient polymer–polymer coupling and potentially difficult post‐conjugation purification. Here a novel grafting‐from approach to grow reversible addition–fragmentation chain transfer (RAFT) polymers from a PBAE scaffold is described. This is achieved through PBAE conversion into a macromolecular chain transfer agent through a multistep capping procedure, followed by RAFT polymerization with a range of monomers to produce PBAE–RAFT hybrid triblock copolymers. Following successful synthesis, the potential biological applications of these ABA triblock copolymers are illustrated through assembly into polymeric micelles and encapsulation of a model hydrophobic drug, followed by successful nanoparticle (NP) uptake in breast cancer cells. The findings demonstrate this novel synthetic methodology can expand the scope of PBAEs as biomaterials

JMM Profile: Carbapenems: a broad-spectrum antibiotic

Carbapenems are potent members of the β-lactam family that inhibit bacterial cell-wall biosynthesis inhibitors . They are highly effective against Gram-negative and Gram-positive drug-resistant infections . As such, carbapenems are typically reserved as an antibiotic of last resort. The WHO lists meropenem as an essential medicine. Nausea and vomiting are reported in ≤20% of carbapenem recipients, with 1.5% suffering seizures. Enzymatic hydrolysis of the β-lactam ring is the main driver of clinical resistance. These enzymes can be classified as Class A, B and D. Classes A and D are serine β-lactamases, whereas Class B rely on metal-mediated hydrolysis, typically through zinc

A Simple Polymicrobial Biofilm Keratinocyte Colonization Model for Exploring Interactions Between Commensals, Pathogens and Antimicrobials

© 2020 Jordana-Lluch, Garcia, Kingdon, Singh, Alexander, Williams and Hardie. Skin offers protection against external insults, with the skin microbiota playing a crucial defensive role against pathogens that gain access when the skin barrier is breached. Linkages between skin microbes, biofilms and disease have not been well established although single-species biofilm formation by skin microbiota in vitro has been extensively studied. Consequently, the purpose of this work was to optimize and validate a simple polymicrobial biofilm keratinocyte model for investigating commensal, pathogen and keratinocyte interactions and for evaluating therapeutic agents or health promoting interventions. The model incorporates the commensals (Staphylococcus epidermidis and Micrococcus luteus) and pathogens (Staphylococcus aureus and Pseudomonas aeruginosa) which form robust polymicrobial biofilms on immortalized keratinocytes (HaCat cells). We observed that the commensals reduce the damage caused to the keratinocyte monolayer by either pathogen. When the commensals were combined with P. aeruginosa and S. aureus, much thinner biofilms were observed than those formed by the pathogens alone. When P. aeruginosa was inoculated with S. epidermidis in the presence or absence of M. luteus, the commensals formed a layer between the keratinocytes and pathogen. Although S. aureus completely inhibited the growth of M. luteus in dual-species biofilms, inclusion of S. epidermidis in triple or quadruple species biofilms, enabled M. luteus to retain viability. Using this polymicrobial biofilm keratinocyte model, we demonstrate that a quorum sensing (QS) deficient S. aureus agr mutant, in contrast to the parent, failed to damage the keratinocyte monolayer unless supplied with the exogenous cognate autoinducing peptide. In addition, we show that treatment of the polymicrobial keratinocyte model with nanoparticles containing an inhibitor of the PQS QS system reduced biofilm thickness and P. aeruginosa localization in mono- and polymicrobial biofilms