A Novel Lipid-Based MALDI-TOF Assay for the Rapid Detection of Colistin-Resistant Enterobacter Species

Smith RD, McElheny CL, Izac JR, Gardner FM, Chandler CE, Goodlett DR, Doi Y, Johnson JK, Ernst RK. Microb Sectrum 2022 Feb 2.

Enterobacter species are classified as high-priority pathogens due to high prevalence of multidrug resistance from persistent antibiotic use. For Enterobacter infections caused by multidrug-resistant isolates, colistin (polymyxin E), a last-resort …

Rapid identification of mcr-1-positive Escherichia coli from patient urine using a novel lipid-based MALDI-TOF-MS assay

Smith RD, Izac JR, Ha M, et al. Access Microbio. 2021 Dec 17

Mobilized colistin resistance (mcr) genes confer resistance to colistin, a last-resort antibiotic for multidrug-resistant Gram-negative infections. In this case report, we describe a novel lipid-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) diagnostic used to rapidly …

Deep-sea microbes as tools to refine the rules of innate immune pattern recognition

Gauthier AE, Chandler CE, Poli V, Gardner FM, et al. Sci Immunol. 2021 Mar 12

The assumption of near-universal bacterial detection by pattern recognition receptors is a foundation of immunology. The limits of this pattern recognition concept, however, remain undefined. As a test of this hypothesis, we determined whether mammalian cells can recognize bacteria that they have never had …

Colistin heteroresistance is largely undetected among carbapenem-resistant Enterobacterales in the United States

Band V, Satola S, Smith R, et al. mBio 2021 Jan 26

Heteroresistance is a form of antibiotic resistance where a bacterial strain is comprised of a minor resistant subpopulation and a majority susceptible subpopulation. We showed previously that colistin heteroresistance can mediate the failure of colistin therapy in an in vivo infection model, even for isolates designated susceptible …

Rapid microbial identification and colistin resistance detection via MALDI-TOF MS using a novel on-target extraction of membrane lipids

Sorensen M, Chandler CE, Gardner F, et al. Scientific Reports 2020 Dec.

Rapid infection diagnosis is critical to improving patient treatment and outcome. Recent studies have shown microbial lipids to be sensitive and selective biomarkers for identifying bacterial and fungal species and antimicrobial resistance. Practical procedures for microbial lipid …

Early evolutionary loss of the lipid A modifying enzyme PagP resulting in innate immune evasion in Yersinia pestis

Chandler CE, Harberts EM, Pelletier MR, et al. Proc Natl Acad Sci U S A 2020 Sep 15.

Immune evasion through membrane remodeling is a hallmark of Yersinia pestis pathogenesis. Yersinia remodels its membrane during its life cycle as it alternates between mammalian hosts (37 °C) and ambient (21 °C to 26 °C) temperatures of the arthropod transmission vector or external …

Streamlined Analysis of Cardiolipins in Prokaryotic and Eukaryotic Samples Using a Norharmane Matrix by MALDI-MSI

Yang H, Jackson SN, Woods AS, et al. J Am Soc Mass Spectrom. 2020 Oct 5.

Cardiolipins (CLs) are an important, regulated lipid class both in prokaryotic and eukaryotic cells, yet they remain largely unexplored by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) in tissues. To date, no in-depth optimization studies of label-free visualization of CLs in …

On-tissue derivatization of lipopolysacharide for detection of lipid A using MALDI-MSI

Yang H, Chandler CE, Jackson SN, et al. Analytical Chemistry 2020 Sep.

We developed a method to directly detect and map the Gram-negative bacterial virulence factor lipid A derived from lipopolysaccharide (LPS) by coupling acid hydrolysis with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). As the structure of lipid A (endotoxin) determines the …

Bacterial medium-chain 3-hydroxy fatty acid metabolites trigger immunity in Arabidopsis plants

Kutschera A, Dawid C, Gisch N, Schmid C, et al. Science 2019 Apr 12

In plants, cell-surface immune receptors sense molecular non–self-signatures. Lipid A of Gram-negative bacterial lipopolysaccharide is considered such a non–self-signature. The receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) mediates plant immune responses to Pseudomonas

A Prospective Study of Acinetobacter baumannii Complex Isolates and Colistin Susceptibility Monitoring by Mass Spectrometry of Microbial Membrane Glycolipids

Leung LM, McElheny CL, Gardner FM, et al. J Clin Microbiol. 2019 Feb.

Acinetobacter baumannii is a prevalent nosocomial pathogen with a high incidence of multidrug resistance. Treatment of infections due to this organism with colistin, a last-resort antibiotic of the polymyxin class, can result in the emergence of colistin-resistant strains. Colistin resistance primarily occurs via …

Rapid Microbial Identification and Antibiotic Resistance Detection by Mass Spectrometric Analysis of Membrane Lipids

Liang T, Leung LM, Opene B, et al. Analytical Chemistry 2019 Jan.

Infectious diseases have a substantial global health impact. Clinicians need rapid and accurate diagnoses of infections to direct patient treatment and improve antibiotic stewardship. Current technologies employed in routine diagnostics are based on bacterial culture followed by morphological trait differentiation and …

Pathogen Identification Direct From Polymicrobial Specimens Using Membrane Glycolipids

Fondrie WE, Liang T, Oyler BL, et al. Scientific Reports 2018 Oct.

With the increased prevalence of multidrug-resistant Gram-negative bacteria, the use of colistin and other last-line antimicrobials is being revisited clinically. As a result, there has been an emergence of colistin-resistant bacterial species, including Acinetobacter baumannii and Klebsiella pneumoniae.

Optimized surface acoustic wave nebulization facilitates bacterial phenotyping

Liang T, Schneider T, Yoon SH, et al. Int J Mass Spectrom. 2018 Apr.

We report on the characterization of three different Surface Acoustic Wave Nebulization (SAWN) chip designs for use in mass spectrometric (MS) analysis of the bacterial glycolipid known as lipid A. We used three different statistical methods to objectively calculate MS noise level and, subsequently, signal-to-noise …

Lipid A structural modifications in extreme conditions and identification of unique modifying enzymes to define the Toll-like receptor 4 structure-activity relationship

Scott AJ, Oyler BL, Goodlett DR, Ernst RK. Biochim Biophys Acta Mol Cell Biol Lipids. 2017 Nov

Strategies utilizing Toll-like receptor 4 (TLR4) agonists for treatment of cancer, infectious diseases, and other targets report promising results. Potent TLR4 antagonists are also gaining attention as therapeutic leads. Though some principles for TLR4 modulation by lipid A have been …

Structural modification of LPS in colistin-resistant, KPC-producing Klebsiella pnemoniae

Leung LM, Cooper VS, Rasko DA, et al. J Antimicrob Chemother. 2017 Nov.

Colistin resistance in Klebsiella pneumoniae typically involves inactivation or mutations of chromosomal genes mgrB, pmrAB or phoPQ, but data regarding consequent modifications of LPS are limited.
To examine the sequences of chromosomal loci implicated in colistin resistance and the …

Identification of the ESKAPE pathogens by mass spectrometric analysis of microbial membrane glycolipids

Leung LM, Fondrie WE, Doi Y, et al. Sci Rep. 2017 Jul

Rapid diagnostics that enable identification of infectious agents improve patient outcomes, antimicrobial stewardship, and length of hospital stay. Current methods for pathogen detection in the clinical laboratory include biological culture, nucleic acid amplification, ribosomal protein characterization, and genome sequencing. …

Structural Modification of Lipopolysaccharide Conferred by mcr-1 in Gram-Negative ESKAPE Pathogens

Liu YY, Chandler CE, Leung LM, et al. Antimicrob Agents Chemother. 2017 May 24

mcr-1 was initially reported as the first plasmid-mediated colistin resistance gene in clinical isolates of Escherichia coli and Klebsiella pneumoniae in China and has subsequently been identified worldwide in various species of the family Enterobacteriaceae. mcr-1 encodes a …

Norharmane Matrix Enhances Detection of Endotoxin by MALDI-MS for Simultaneous Profiling of Pathogen, Host, and Vector Systems

Scott AJ, Flinders B, Cappell J, Liang T, Pelc RS, et al. Pathog Dis. 2016 Nov

The discovery of novel pathogenic mechanisms engaged during bacterial infections requires the evolution of advanced techniques. Here, we evaluate the dual polarity matrix norharmane (NRM) to improve detection of bacterial lipid A (endotoxin), from host and vector tissues infected with Francisella novicida

Site-specific activity of the acyltransferases HtrB1 and HtrB2 in Pseudomonas aeruginosa lipid A biosynthesis

Hittle LE, Powell DA, Jones JW, Tofigh M, Goodlett DR, Moskowitz SM, Ernst RK. Pathog Dis. 2015 Nov

Pseudomonas aeruginosa (PA) is an opportunistic Gram-negative pathogen associated with nosocomial infections, acute infections and chronic lung infections in patients with cystic fibrosis. The ability of PA to cause infection can be attributed to its ability to adapt to a multitude of …

Unique structural modifications are present in the lipopolysaccharide from colistin-resistant strains of Acinetobacter baumannii

Pelletier MR, Casella LG, Jones JW, et al. Antimicrob Agents Chemother. 2013 Oct

Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause severe infections, including hospital-acquired pneumonia, wound infections, and sepsis. Multidrug-resistant (MDR) strains are prevalent, further complicating patient treatment. Due to the increase in MDR strains, the cationic …

Influence of lipid A acylation pattern on membrane permeability and innate immune stimulation

Li Y, Wang Z, Chen J, Ernst RK, Wang X. Mar Drugs. 2013 Aug 26

Lipid A, the hydrophobic anchor of lipopolysaccharide (LPS), is an essential component in the outer membrane of Gram-negative bacteria. It can stimulate the innate immune system via Toll-like receptor 4/myeloid differentiation factor 2 (TLR4/MD2), leading to the release of inflammatory cytokines. In this study, six Escherichia …

LPS remodeling is an evolved survival strategy for bacteria

Li Y, Powell DA, Shaffer SA, Rasko DA, et al. Proc Natl Acad Sci U S A 2012 May 29

Maintenance of membrane function is essential and regulated at the genomic, transcriptional, and translational levels. Bacterial pathogens have a variety of mechanisms to adapt their membrane in response to transmission between environment, vector, and human host. Using a well-characterized model of lipid …

Unique lipid A modifications in Pseudomonas aeruginosa isolated from the airways of patients with cystic fibrosis

Ernst RK, Moskowitz SM, Emerson JC, et al. J Infect Dis. 2007 Oct

Three structural features of lipid A (addition of palmitate [C16 fatty acid], addition of aminoarabinose [positively charged amino sugar residue], and retention of 3-hydroxydecanoate [3-OH C10 fatty acid]) were determined for Pseudomonas aeruginosa isolates from patientswith cystic fibrosis (CF; n = 86), from the environment …

pmrA(Con) confers pmrHFIJKL-dependent EGTA and polymyxin resistance on msbB Salmonella by decorating lipid A with phosphoethanolamine

Murray SR, Ernst RK, Bermudes D, et al. J Bacteriol 2007 Jul

Mutations in pmrA were recombined into Salmonella strain ATCC 14028 msbB to determine if pmrA-regulated modifications of lipopolysaccharide could suppress msbB growth defects. A mutation that functions to constitutively activate pmrA [pmrA(Con)] suppresses msbB growth defects …