Increased survival of experimentally evolved antimicrobial peptide-resistant Staphylococcus aureus in an animal host.

Antimicrobial peptides (AMPs) have been proposed as new class of antimicrobial drugs, following the increasing prevalence of bacteria resistant to antibiotics. Synthetic AMPs are functional analogues of highly evolutionarily conserved immune effectors in animals and plants, produced in response to microbial infection. Therefore, the proposed therapeutic use of AMPs bears the risk of ‘arming the enemy’: bacteria that evolve resistance to AMPs may be cross‐resistant to immune effectors (AMPs) in their hosts. We used a panel of populations of Staphylococcus aureus that were experimentally selected for resistance to a suite of individual AMPs and antibiotics to investigate the ‘arming the enemy’ hypothesis. We tested whether the selected strains showed higher survival in an insect model (Tenebrio molitor) and cross‐resistance against other antimicrobials in vitro. A population selected for resistance to the antimicrobial peptide iseganan showed increased in vivo survival, but was not more virulent. We suggest that increased survival of AMP‐resistant bacteria almost certainly poses problems to immune‐compromised hosts

Conceptualisations of landscape differ across European languages

Acknowledgments: Thanks to Peter Sercombe for assistance with English data collection and to Maximilian Hartmann for assisting in the creation of the network visualisations. Funding: This work was funded by a Bank of Sweden Tercentenary Foundation Jubilee Initiative Grant (https://www.rj.se/en), grant ref. NHS14-1665:1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Role of horizontally transferred copper resistance genes in Staphylococcus aureus and Listeria monocytogenes

Bacteria have evolved mechanisms which enable them to control intracellular concentrations of metals. In the case of transition metals, such as copper, iron and zinc, bacteria must ensure enough is available as a cofactor for enzymes whilst at the same time preventing the accumulation of excess concentrations, which can be toxic. Interestingly, metal homeostasis and resistance systems have been found to play important roles in virulence. This review will discuss the copper homeostasis and resistance systems in Staphylococcus aureus and Listeria monocytogenes and the implications that acquisition of additional copper resistance genes may have in these pathogens

An Investigation into the Function and Regulation of GAPDH in Staphylococcus aureus

Staphylococcus aureus is an important pathogen of both humans and animals. With the growing spread of MRSA strains in clinical environments and the wider community, it is imperative that we understand the basic physiology of this species to find new antimicrobial or vaccine targets. This project focuses on the function and regulation of glyceraldehyde-3-phosphate dehydrogenase, or GAPDH, an essential component of glucose metabolism. S. aureus contains two GAPDH homologues; GapA, a known GAPDH protein and GapB, the function of which is undefined. Using a number of complementary approaches we have shown that GapA and GapB have reciprocal functions during glucose metabolism, and that both homologues are required during infection. We have also identified novel “moonlighting” roles for both GapA and GapB and shown that both genes are regulated by divalent metal ions. Interestingly iron regulation of gapA is strain variable at the transcriptional level due to sequence variation between strains, and appears to involve a S. aureus repeat (STAR) element locus. To our knowledge this is the first indication that these repeat elements are functional. STAR elements are found across the S. aureus genome, and the number of repeats at each locus is variable between strains. Surprisingly the three STAR loci (gapR, hprK and orf0733) analysed are highly conserved and maintained in the S. aureus genome at a level similar to that of MLST loci which suggests that they may have an important function, although transcriptional analysis failed to identify a correlation between repeat number and transcript levels. However transcriptional analysis did demonstrate that a number of STAR and non-STAR associated loci in S. aureus, including housekeeping genes involved in central metabolism, known transcriptional regulators and virulence factors show strain variable levels of expression, which may play a role in the significant adaptability of S. aureus

An investigation into the function and regulation of GAPDH in Staphylococcus aureus

Staphylococcus aureus is an important pathogen of both humans and animals. With the growing spread of MRSA strains in clinical environments and the wider community, it is imperative that we understand the basic physiology of this species to find new antimicrobial or vaccine targets. This project focuses on the function and regulation of glyceraldehyde-3-phosphate dehydrogenase, or GAPDH, an essential component of glucose metabolism. S. aureus contains two GAPDH homologues; GapA, a known GAPDH protein and GapB, the function of which is undefined. Using a number of complementary approaches we have shown that GapA and GapB have reciprocal functions during glucose metabolism, and that both homologues are required during infection. We have also identified novel “moonlighting” roles for both GapA and GapB and shown that both genes are regulated by divalent metal ions. Interestingly iron regulation of gapA is strain variable at the transcriptional level due to sequence variation between strains, and appears to involve a S. aureus repeat (STAR) element locus. To our knowledge this is the first indication that these repeat elements are functional. STAR elements are found across the S. aureus genome, and the number of repeats at each locus is variable between strains. Surprisingly the three STAR loci (gapR, hprK and orf0733) analysed are highly conserved and maintained in the S. aureus genome at a level similar to that of MLST loci which suggests that they may have an important function, although transcriptional analysis failed to identify a correlation between repeat number and transcript levels. However transcriptional analysis did demonstrate that a number of STAR and non-STAR associated loci in S. aureus, including housekeeping genes involved in central metabolism, known transcriptional regulators and virulence factors show strain variable levels of expression, which may play a role in the significant adaptability of S. aureus.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

ARSA.CFUdat

in vivo survival of AMP-resistant S. aureu

ARSA.survDat.21d

Survival of T. molitor infected with AMP-resistant S. aureu

Comparing selection on S. aureus between antimicrobial peptides and common antibiotics.

With a diminishing number of effective antibiotics, there has been interest in developing antimicrobial peptides (AMPs) as drugs. However, any new drug faces potential bacterial resistance evolution. Here, we experimentally compare resistance evolution in Staphylococcus aureus selected by three AMPs (from mammals, amphibians and insects), a combination of two AMPs, and two antibiotics: the powerful last-resort vancomycin and the classic streptomycin. We find that resistance evolves readily against single AMPs and against streptomycin, with no detectable fitness cost. However the response to selection from our combination of AMPs led to extinction, in a fashion qualitatively similar to vancomycin. This is consistent with the hypothesis that simultaneous release of multiple AMPs during immune responses is a factor which constrains evolution of AMP resistant pathogens

Comparison of the Regulation, Metabolic Functions, and Roles in Virulence of the Glyceraldehyde-3-Phosphate Dehydrogenase Homologues gapA and gapB in Staphylococcus aureus▿

The Gram-positive bacterium Staphylococcus aureus contains two glyceraldehyde-3-phosphate dehydrogenase (GAPDH) homologues known as GapA and GapB. GapA has been characterized as a functional GAPDH protein, but currently there is no biological evidence for the role of GapB in metabolism in S. aureus. In this study we show through a number of complementary methods that S. aureus GapA is essential for glycolysis while GapB is essential in gluconeogenesis. These proteins are reciprocally regulated in response to glucose concentrations, and both are influenced by the glycolysis regulator protein GapR, which is the first demonstration of the role of this regulator in S. aureus and the first indication that GapR homologues control genes other than those within the glycolytic operon. Furthermore, we show that both GapA and GapB are important in the pathogenesis of S. aureus in a Galleria mellonella model of infection, showing for the first time in any bacteria that both glycolysis and gluconeogenesis have important roles in virulence

Fold-change in MIC/population/week (median of 3 tests/combination), relative to ancestral population.

<p>Zero observed inhibition is denoted by indication of MIC greater than the fold-change in MIC that would be inferred by MIC at the greatest concentration of stressor assayed.</p>**<p>data excluded due to low OD upon inoculation into MIC assays.</p><p>l: low-density (pexiganan) and e: extinct cultures.</p