Biology subjects

Douglas, E. J. A.

Publications and source records attributed to Douglas, E. J. A..

5 recordsLinked to original sources

bioRxiv2026

Murepavadin is a broad-spectrum outer membrane permeabiliser

Murepavadin is a Pseudomonas-specific antibiotic that targets LPS transport protein LptD. However, whilst the mode of action of murepavadin is well defined, the mechanism by which the drug gains access to LptD remains unresolved. Here, we demonstrate a self-directed uptake mechanism for murepavadin, whereby binding to lipid A induces outer membrane disruption, enabling entry of the antibiotic into the periplasm and access to LptD. Murepavadin-LPS interactions were not specific to P. aeruginosa, however, and were found to cause OM disruption across a wide range of Gram-negative bacteria, resulting in increased antibiotic susceptibility. We also discovered that murepavadin-mediated OM disruption sensitised E. coli to the membrane attack complex of the complement system. In conclusion, murepavadin is a broad-spectrum membrane permeabiliser, which results in increased bacterial susceptibility to antibiotics and host defences.

microbiology↗

bioRxiv2025

Polymyxin heteroresistance in Klebsiella oxytoca

Antibiotic heteroresistance presents a growing public health concern since the phenotype is associated with treatment failure and is hard to detect using conventional diagnostic testing. In this study, we characterized polymyxin B heteroresistance in a collection of clinical and environmental isolates of Klebsiella oxytoca, an opportunistic pathogen associated with hospital-acquired infections. All six of the isolates tested exhibited heteroresistance, indicated by a 16-fold difference between the highest non-inhibitory concentration (2 {micro}g/mL) and the minimum inhibitory concentration (32-64 {micro}g/mL) observed in population analysis profile (PAP) assays. Heteroresistance was found to be due to the presence of a stable sub-population of resistant bacteria and was unaffected by growth phase or the presence of host antimicrobial factors present in human serum. MALDI-TOF analysis revealed L-Ara4N modifications of the lipid A of resistant sub-populations. This pilot study identifies polymyxin heteroresistance in K. oxytoca may complicate treatment of infections caused by this organism.

microbiology↗

bioRxiv2025

Polymyxin B lethality requires energy-dependent outer membrane disruption

Polymyxin antibiotics target lipopolysaccharide (LPS) in both membranes of the bacterial cell envelope, leading to bacterial killing through a mechanism that remains poorly understood. Here, we demonstrate that metabolic activity is essential for polymyxin lethality and leverage this insight to determine its mode of action. Polymyxin B (PmB) efficiently killed exponential phase E. coli but was unable to eliminate stationary phase cells unless a carbon source was available. Antibiotic lethality correlated with surface protrusions, LPS loss, and a significant reduction in outer membrane (OM) barrier function, processes that required LPS synthesis and transport. While the energy-dependent OM disruption was not directly lethal, it facilitated PmB access to the inner membrane (IM), which the antibiotic permeabilised in an energy-independent manner, leading to cell death. Finally, we show that the polymyxin resistance determinant MCR-1 prevents PmB-mediated LPS loss and OM protrusions and thereby renders the antibiotic ineffective.

microbiology↗

bioRxiv2023

Extensive re-modelling of the cell wall during the development of Staphylococcus aureus bacteraemia

Introductory Paragraph / AbstractThe bloodstream represents a hostile environment that bacteria must overcome to cause bacteraemia. To understand how the major human pathogen Staphylococcus aureus manages this we have utilised a functional genomics approach to identify a number of new loci that affect the ability of the bacteria to survive exposure to serum, the critical first step in the development of bacteraemia. The expression of one of these genes, tcaA, was found to be induced upon exposure to serum, and we show that it is involved in the elaboration of a critical virulence factor, the wall teichoic acids (WTA), within the cell envelope. The activity of the TcaA protein alters the sensitivity of the bacteria to cell wall attacking agents, including antimicrobial peptides, human defence fatty acids, and several antibiotics. This protein also affects the autolytic activity and lysostaphin sensitivity of the bacteria, suggesting that in addition to changing WTA abundance in the cell envelope, it also plays a role in peptidoglycan crosslinking. With TcaA rendering the bacteria more susceptible to serum killing, while simultaneously increasing the abundance of WTA in the cell envelope, it was unclear what effect this protein may have during infection. To explore this, we examined human data and performed murine experimental infections. Collectively, our data suggests that whilst mutations in tcaA are selected for during bacteraemia, this protein positively contributes to the virulence of S. aureus through its involvement in altering the cell wall architecture of the bacteria, a process that appears to play a key role in the development of bacteraemia.

microbiology↗

bioRxiv2021

The MpsB protein contributes to both the toxicity and immune evasion capacity of Staphylococcus aureus.

Understanding the role specific bacterial factors play in the development of severe disease in humans is critical if new approaches to tackle such infections are to be developed. In this study we focus on genes we have found to be associated with patient outcome following bacteraemia caused by the major human pathogen Staphylococcus aureus. By examining the contribution these genes make to the ability of the bacteria to survive exposure to the antibacterial factors found in serum, we identify three novel serum resistance associated genes, mdeA, mpsB and yycH. Detailed analysis of an MpsB mutant supports its previous association with the slow growing SCV phenotype of S. aureus, and we demonstrate that the effect this mutation has on membrane potential prevents the activation of the Agr quorum sensing system, and as a consequence the mutant bacteria do not produce cytolytic toxins. Given the importance of both toxin production and immune evasion to the ability of S. aureus to cause disease, we believe these findings explain the role of the mpsB gene as a mortality-associate locus during human disease.

microbiology↗