Predatory bacteria prevent the proliferation of intraocular and fluoroquinolone-resistant .

Endogenous endophthalmitis caused by Gram-negative bacteria is an intra-ocular infection that can rapidly progress to irreversible loss of vision. While most endophthalmitis isolates are susceptible to antibiotic therapy, the emergence of resistant bacteria necessitates alternative approaches to combat intraocular bacterial proliferation. In this study the ability of predatory bacteria to limit intraocular growth of , , and was evaluated in a New Zealand white rabbit endophthalmitis prevention model.

A rise in the frequency of mutant among keratitis isolates between 1993 and 2021.

Introduction: causes vision threatening keratitis. The transcription factor regulates virulence factors in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. isolates with mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone.

Intra-ocular Predation of Fluoroquinolone-Resistant and by Predatory Bacteria.

Endogenous endophthalmitis caused by Gram-negative bacteria is an intra-ocular infection that can rapidly progress to irreversible loss of vision. While most endophthalmitis isolates are susceptible to antibiotic therapy, the emergence of resistant bacteria necessitates alternative approaches to combat intraocular bacterial proliferation. In this study the ability of predatory bacteria to limit intraocular growth of , , and was evaluated in a New Zealand White rabbit endophthalmitis prevention model.

Rise in frequency of mutant among keratitis isolates between 1993 and 2021.

causes severe vision threatening keratitis. LasR is a transcription factor that regulates virulence associated genes in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. isolates with mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone.

Predatory bacteria can reduce Pseudomonas aeruginosa induced corneal perforation and proliferation in a rabbit keratitis model.

Purpose: Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P.

Predatory Bacteria can Reduce Induced Corneal Perforation and Proliferation in a Rabbit Keratitis Model.

Purpose: keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria could alter the clinical outcome. with mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic mutant strain of was included.

The Short-chain Fatty Acid Propionic Acid Activates the Rcs Stress Response System Partially through Inhibition of d-Alanine Racemase.

The Enterobacterial Rcs stress response system reacts to envelope stresses through a complex two-component phosphorelay system to regulate a variety of environmental response genes, such as capsular polysaccharide and flagella biosynthesis genes. However, beyond Escherichia coli, the stresses that activate Rcs are not well-understood. In this study, we used a Rcs system-dependent luminescent transcriptional reporter to screen a library of over 240 antimicrobial compounds for those that activated the Rcs system in Serratia marcescens, a family bacterium.

IgaA Protein, GumB, Has a Global Impact on the Transcriptome and Surface Proteome of Serratia marcescens.

Bacterial stress response signaling systems, like the Rcs system are triggered by membrane and cell wall damaging compounds, including antibiotics and immune system factors. These regulatory systems help bacteria survive envelope stress by altering the transcriptome resulting in protective phenotypic changes that may also influence the virulence of the bacterium. This study investigated the role of the Rcs stress response system using a clinical keratitis isolate of Serratia marcescens with a mutation in the gene.

Novel Combined Lidocaine/Povidone Iodine Delivery System for Preintravitreal Injection.

Intravitreal injection has become a popular treatment for various retina disorders and dramatically increased over the past few years. In traditional preintravitreal injection, the preparation steps are time consuming for practitioners who perform a significant number of injections per day. Besides, lidocaine gel (L-Gel) shows a potential absorption barrier on the antibacterial effect of povidone iodine (PI).

Bacterial Keratitis: imilar Bacterial and Clinical Outcomes in Female versus Male New Zealand White Rabbits Infected with .

Purpose: Females and males respond differently to a number of systemic viral infections. Differences between females and males with respect to the severity of keratitis caused by Gram-negative bacteria such as are less well established.

Methods: In this study, we injected female and male New Zealand White rabbit corneas with a keratitis isolate of and evaluated the eyes after 48 hours for a number of clinical and microbiological parameters.

Antibiotics Used in Empiric Treatment of Ocular Infections Trigger the Bacterial Rcs Stress Response System Independent of Antibiotic Susceptibility.

The Rcs phosphorelay is a bacterial stress response system that responds to envelope stresses and in turn controls several virulence-associated pathways, including capsule, flagella, and toxin biosynthesis, of numerous bacterial species. The Rcs system also affects antibiotic tolerance, biofilm formation, and horizontal gene transfer. The Rcs system of the ocular bacterial pathogen was recently demonstrated to influence ocular pathogenesis in a rabbit model of keratitis, with Rcs-defective mutants causing greater pathology and Rcs-activated strains demonstrating reduced inflammation.

The Rcs Stress Response System Regulator GumB Modulates Serratia marcescens-Induced Inflammation and Bacterial Proliferation in a Rabbit Keratitis Model and Cytotoxicity .

In this study, we tested the hypothesis that the conserved bacterial IgaA-family protein, GumB, mediates microbial pathogenesis associated with Serratia marcescens ocular infections through regulation of the Rcs stress response system. The role of the Rcs system and bacterial stress response systems for microbial keratitis is not known, and the role of IgaA proteins in mammalian pathogenesis models has only been tested with partial-function allele variants of Salmonella. Here, we observed that an Rcs-activated mutant had a >50-fold reduction in proliferation compared to the wild type within rabbit corneas at 48 h and demonstrated a notable reduction in inflammation based on inflammatory signs, including the absence of hypopyons, and proinflammatory markers measured at the RNA and protein levels.

Differential susceptibility of airway and ocular surface cell lines to FlhDC-mediated virulence factors PhlA and ShlA from .

is a bacterial pathogen that causes ventilator-associated pneumonia and ocular infections. The FlhD and FlhC proteins complex to form a heteromeric transcription factor whose regulon, in , regulates genes for the production of flagellum, phospholipase A and the cytolysin ShlA. The previously identified mutation, , resulted in highly elevated expression of the operon.

mCloverBlaster: A tool to make markerless deletions and fusions using lambda red and I-SceI in Gram-negative bacterial genomes.

This study introduces mCloverBlaster as a genetic tool to create deletions and transcriptional and translational fusions in bacterial genomes using recombineering. The major advantage of this system is that it can be used to make deletions and fusions without leaving a selectable marker on the chromosome. mCloverBlaster has a kanamycin resistance cassette with an I-SceI restriction site flanked by fragments of the gene for the mClover3 fluorescent protein including direct repeats of mClover3 sequence on both sides of the kanamycin resistance gene.

Xylose-Inducible Promoter Tools for Species and Their Use in Implicating a Role for the Type II Secretion System Protein XcpQ in the Inhibition of Corneal Epithelial Wound Closure.

Tunable control of gene expression is an invaluable tool for biological experiments. In this study, we describe a new xylose-inducible promoter system and evaluate it in both and The promoter, derived from the operon, was incorporated into a broad-host-range pBBR1-based plasmid and was compared to the -derived promoter using as a reporter. Green fluorescent protein (GFP) fluorescence from the promoter was inducible in both species, but not in , which may facilitate the cloning of genes toxic to to generate plasmids.

Biologically active pigment and ShlA cytolysin of Serratia marcescens induce autophagy in a human ocular surface cell line.

Background: The cellular process of autophagy is essential for maintaining the health of ocular tissue. Dysregulation of autophagy is associated with several ocular diseases including keratoconus and macular degeneration. It is known that autophagy can be used to respond to microbial infections and that certain microbes can exploit the autophagic process to their benefit.

Use of Collagen Binding Domains to Deliver Molecules to the Cornea.

The combined activity of the tear film and blinking is remarkably efficient at removal of foreign materials from the ocular surface. This has prevented the use of certain classes of drugs for the treatment of ocular surface problems. We propose that the use of peptide and protein domains that bind to moieties on the cornea could be used to deliver therapeutics by anchoring the drugs on the ocular surface long enough to provide therapeutic effects.

Blowing epithelial cell bubbles with GumB: ShlA-family pore-forming toxins induce blebbing and rapid cellular death in corneal epithelial cells.

Medical devices, such as contact lenses, bring bacteria in direct contact with human cells. Consequences of these host-pathogen interactions include the alteration of mammalian cell surface architecture and induction of cellular death that renders tissues more susceptible to infection. Gram-negative bacteria known to induce cellular blebbing by mammalian cells, Pseudomonas and Vibrio species, do so through a type III secretion system-dependent mechanism.

Thermoregulation of Prodigiosin Biosynthesis by is Controlled at the Transcriptional Level and Requires HexS.

Several biotypes of the Gram-negative bacterium produce the tri-pyrole pigment and secondary metabolite prodigiosin. The biological activities of this pigment have therapeutic potential. For over half a century it has been known that biosynthesis of prodi giosin is inhibited when bacteria are grown at elevated temperatures, yet the fundamental mechanism underlying this thermoregulation has not been characterized.

Serralysin family metalloproteases protects Serratia marcescens from predation by the predatory bacteria Micavibrio aeruginosavorus.

Micavibrio aeruginosavorus is an obligate Gram-negative predatory bacterial species that feeds on other Gram-negative bacteria by attaching to the surface of its prey and feeding on the prey's cellular contents. In this study, Serratia marcescens with defined mutations in genes for extracellular cell structural components and secreted factors were used in predation experiments to identify structures that influence predation. No change was measured in the ability of the predator to prey on S.

In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution on Established Biofilms.

Objectives: The purpose of this study was to determine whether a commercial formulation of hypochlorous acid hygiene solution (0.01%), Avenova, can destroy existing biofilms formed by ocular clinical bacterial isolates, including blepharitis isolates of Staphylococcus aureus and coagulase-negative staphylococci, and a keratitis isolate of Pseudomonas aeruginosa.

Methods: Biofilms grown in bacterial growth media on disposable contact lens cases were challenged with hypochlorous acid hygiene solution.

An IgaA/UmoB Family Protein from Serratia marcescens Regulates Motility, Capsular Polysaccharide Biosynthesis, and Secondary Metabolite Production.

Secondary metabolites are an important source of pharmaceuticals and key modulators of microbe-microbe interactions. The bacterium is part of the family of eubacteria and produces a number of biologically active secondary metabolites. In this study, we screened for novel regulators of secondary metabolites synthesized by a clinical isolate of and found mutations in a gene for an uncharacterized UmoB/IgaA family member here named Mutation of conferred a severe loss of the secondary metabolites prodigiosin and serratamolide.

SlpE is a calcium-dependent cytotoxic metalloprotease associated with clinical isolates of Serratia marcescens.

Serralysin-like proteases are found in a wide variety of bacteria. These metalloproteases are frequently implicated in virulence and are members of the widely conserved RTX-toxin family. We identified a serralysin-like protease in the genome of a clinical isolate of Serratia marcescens that is highly similar to the canonical serralysin protein, PrtS.

Suppressor analysis of eepR mutant defects reveals coordinate regulation of secondary metabolites and serralysin biosynthesis by EepR and HexS.

The EepR transcription factor positively regulates secondary metabolites and tissue-damaging metalloproteases. To gain insight into mechanisms by which EepR regulates pigment and co-regulated factors, genetic suppressor analysis was performed. Suppressor mutations that restored pigment to the non-pigmented ∆eepR mutant mapped to the hexS ORF.

Predatory bacteria are nontoxic to the rabbit ocular surface.

Given the increasing emergence of antimicrobial resistant microbes and the near absent development of new antibiotic classes, innovative new therapeutic approaches to address this global problem are necessary. The use of predatory bacteria, bacteria that prey upon other bacteria, is gaining interest as an "out of the box" therapeutic treatment for multidrug resistant pathogenic bacterial infections. Before a new antimicrobial agent is used to treat infections, it must be tested for safety.