Characterization of acquired β-lactamases in and quantification of their contributions to resistance.

is a highly problematic opportunistic pathogen that causes a range of different infections. Infections are commonly treated with β-lactam antibiotics, including cephalosporins, monobactams, penicillins, and carbapenems, with carbapenems regarded as antibiotics of last resort. Isolates of can contain horizontally acquired genes encoding β-lactamase enzymes, but the extent to which these contribute to β-lactam resistance in this species has not been systematically quantified.

Penicillin-binding protein 3 sequence variations reduce susceptibility of Pseudomonas aeruginosa to β-lactams but inhibit cell division.

Background: β-lactam antibiotics, which inhibit penicillin-binding protein 3 (PBP3) that is required for cell division, play a key role in treating P. aeruginosa infections. Some sequence variations in PBP3 have been associated with β-lactam resistance but the effects of variations on antibiotic susceptibility and on cell division have not been quantified.

Using host-mimicking conditions and a murine cutaneous abscess model to identify synergistic antibiotic combinations effective against .

Antibiotic drug combination therapy is critical for the successful treatment of infections caused by multidrug resistant pathogens. We investigated the efficacy of β-lactam and β-lactam/β-lactamase inhibitor combinations with other antibiotics, against the hypervirulent, ceftazidime/avibactam resistant Liverpool epidemic strain (LES) B58. Although minimum inhibitory concentrations differed by up to eighty-fold between standard and host-mimicking media, combinatorial effects only marginally changed between conditions for some combinations.

Murepavadin promotes the killing efficacies of aminoglycoside antibiotics against by enhancing membrane potential.

Murepavadin is a peptidomimetic that specifically targets the lipopolysaccharide transport protein LptD of . Here, we found that murepavadin enhances the bactericidal efficacies of tobramycin and amikacin. We further demonstrated that murepavadin enhances bacterial respiration activity and subsequent membrane potential, which promotes intracellular uptake of aminoglycoside antibiotics.

The PitA protein contributes to colistin susceptibility in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen that causes a wide range of problematic infections in individuals with predisposing conditions. Infections can be treated with colistin but some isolates are resistant to this antibiotic. To better understand the genetic basis of resistance, we experimentally evolved 19 independent resistant mutants from the susceptible laboratory strain PAO1.

Murepavadin induces envelope stress response and enhances the killing efficacies of β-lactam antibiotics by impairing the outer membrane integrity of .

is a ubiquitous opportunistic pathogen that can cause a variety of acute and chronic infections. The bacterium is highly resistant to numerous antibiotics. Murepavadin is a peptidomimetic antibiotic that blocks the function of lipopolysaccharide (LPS) transport protein D (LptD), thus inhibiting the insertion of LPS into the outer membrane.

Pseudomonas aeruginosa is oxygen-deprived during infection in cystic fibrosis lungs, reducing the effectiveness of antibiotics.

Pseudomonas aeruginosa infects the lungs of patients with cystic fibrosis. Sputum expectorated from the lungs of patients contains low levels of oxygen, indicating that P. aeruginosa may be oxygen-deprived during infection.

Ceftazidime resistance in Pseudomonas aeruginosa is multigenic and complex.

Pseudomonas aeruginosa causes a wide range of severe infections. Ceftazidime, a cephalosporin, is a key antibiotic for treating infections but a significant proportion of isolates are ceftazidime-resistant. The aim of this research was to identify mutations that contribute to resistance, and to quantify the impacts of individual mutations and mutation combinations.

Gene-Gene Interactions Reduce Aminoglycoside Susceptibility of through Efflux Pump-Dependent and -Independent Mechanisms.

causes a wide range of acute and chronic infections. Aminoglycosides are a cornerstone of treatment, but isolates are often resistant. The purpose of this research was to better understand the genetic basis of aminoglycoside resistance in .

Aminoglycoside-Modifying Enzymes Are Sufficient to Make Clinically Resistant to Key Antibiotics.

Aminoglycosides are widely used to treat infections of . Genes encoding aminoglycoside-modifying enzymes (AMEs), acquired by horizontal gene transfer, are commonly associated with aminoglycoside resistance, but their effects have not been quantified. The aim of this research was to determine the extent to which AMEs increase the antibiotic tolerance of .

Aminoglycoside resistance in : the contribution of the MexXY-OprM efflux pump varies between isolates.

Aminoglycoside antibiotics are widely used to treat infections of . The MexXY-OprM efflux pump is an important contributor to aminoglycoside tolerance in reference strains and expression of the genes is repressed by the MexZ repressor protein. Direct investigation of the role of this efflux pump in clinical isolates is relatively limited.

The Effects of Sub-inhibitory Antibiotic Concentrations on : Reduced Susceptibility Due to Mutations.

chronically infects in the lungs of people with cystic fibrosis and other forms of lung disease. Infections are treated with antibiotics, but over time, the bacteria acquire mutations that reduce their antibiotic susceptibility. The effects of inhibitory amounts of antibiotics in selecting for antibiotic-resistant mutants have been well studied.

β-lactam Resistance in : Current Status, Future Prospects.

is a major opportunistic pathogen, causing a wide range of acute and chronic infections. β-lactam antibiotics including penicillins, carbapenems, monobactams, and cephalosporins play a key role in the treatment of infections. However, a significant number of isolates of these bacteria are resistant to β-lactams, complicating treatment of infections and leading to worse outcomes for patients.

The Pseudomonas aeruginosa whole genome sequence: A 20th anniversary celebration.

Toward the end of August 2000, the 6.3 Mbp whole genome sequence of Pseudomonas aeruginosa strain PAO1 was published. With 5570 open reading frames (ORFs), PAO1 had the largest microbial genome sequenced up to that point in time-including a large proportion of metabolic, transport and antimicrobial resistance genes supporting its ability to colonize diverse environments.

Genome evolution drives transcriptomic and phenotypic adaptation in during 20 years of infection.

The opportunistic pathogen chronically infects the lungs of patients with cystic fibrosis (CF). During infection the bacteria evolve and adapt to the lung environment. Here we use genomic, transcriptomic and phenotypic approaches to compare multiple isolates of collected more than 20 years apart during a chronic infection in a CF patient.

Gene-Gene Interactions Dictate Ciprofloxacin Resistance in Pseudomonas aeruginosa and Facilitate Prediction of Resistance Phenotype from Genome Sequence Data.

Ciprofloxacin is one of the most widely used antibiotics for treating Pseudomonas aeruginosa infections. However, P. aeruginosa acquires mutations that confer ciprofloxacin resistance, making treatment more difficult.

Transmission, adaptation and geographical spread of the Liverpool epidemic strain.

The Liverpool epidemic strain (LES) is an important transmissible clonal lineage of that chronically infects the lungs of people with cystic fibrosis (CF). Previous studies have focused on the genomics of the LES in a limited number of isolates, mostly from one CF centre in the UK, and from studies highlighting identification of the LES in Canada. Here we significantly extend the current LES genome database by genome sequencing 91 isolates from multiple CF centres across the UK, and we describe the comparative genomics of this large collection of LES isolates from the UK and Canada.

Identification of Active Site Residues of the Siderophore Synthesis Enzyme PvdF and Evidence for Interaction of PvdF with a Substrate-Providing Enzyme.

The problematic opportunistic pathogen secretes a siderophore, pyoverdine. Pyoverdine scavenges iron needed by the bacteria for growth and for pathogenicity in a range of different infection models. PvdF, a hydroxyornithine transformylase enzyme, is essential for pyoverdine synthesis, catalysing synthesis of formylhydroxyornithine (fOHOrn) that forms part of the pyoverdine molecule and provides iron-chelating hydroxamate ligands.

One Health Aotearoa: a transdisciplinary initiative to improve human, animal and environmental health in New Zealand.

There is increased recognition that complex health challenges at the human-animal-environmental interface require a transdisciplinary, "" approach. This philosophy is particularly pertinent in Aotearoa-New Zealand because of the country's relatively isolated island ecosystem, economic reliance on agriculture and its intensification, and existing indigenous worldview that emphasises holism and interconnectivity between humans, animals and the environment. In New Zealand, the One Health Aotearoa (OHA) alliance was established in order to better connect researchers and to address a growing number of infectious diseases challenges.

Cell envelope proteases and peptidases of Pseudomonas aeruginosa: multiple roles, multiple mechanisms.

Pseudomonas aeruginosa is a Gram-negative bacterium that is commonly isolated from damp environments. It is also a major opportunistic pathogen, causing a wide range of problematic infections. The cell envelope of P.

A large-scale whole-genome comparison shows that experimental evolution in response to antibiotics predicts changes in naturally evolved clinical .

is an opportunistic pathogen that causes a wide range of acute and chronic infections. An increasing number of isolates have mutations that make them antibiotic resistant, making treatment difficult. To identify resistance-associated mutations we experimentally evolved the antibiotic sensitive strain PAO1 to become resistant to three widely used anti-pseudomonal antibiotics, ciprofloxacin, meropenem and tobramycin.

Genomic and phenotypic comparison of environmental and patient-derived isolates of suggest that antimicrobial resistance is rare within the environment.

Patient-derived isolates of the opportunistic pathogen are frequently resistant to antibiotics due to the presence of sequence variants in resistance-associated genes. However, the frequency of antibiotic resistance and of resistance-associated sequence variants in environmental isolates of has not been well studied. Antimicrobial susceptibility testing (ciprofloxacin, ceftazidime, meropenem, tobramycin) of environmental (=50) and cystic fibrosis (=42) isolates was carried out.

Nucleoside Analogues as Antibacterial Agents.

The rapid increase in antibiotic-resistant bacteria has emphasized the urgent need to identify new treatments for bacterial infections. One attractive approach, reducing the need for expensive and time-consuming clinical trials, is to repurpose existing clinically approved compounds for use as antibacterial agents. Nucleoside analogues are commonly used for treating viral and fungal infections, as well as for treating cancers, but have received relatively little attention as treatments for bacterial infections.

The Role of SreA-Mediated Iron Regulation in Maintaining - Symbioses.

In ascomycetes and basidiomycetes, iron-responsive GATA-type transcriptional repressors are involved in regulating iron homeostasis, notably to prevent iron toxicity through control of iron uptake. To date, it has been unknown whether this iron regulator contributes toward mutualistic endosymbiosis of microbes with plants, a system where the endophyte must function within the constraints of an in-host existence, including a dependency on the host for nutrient acquisition. Functional characterization of one such protein, SreA from , a fungal endosymbiont of cool-season grasses, indicates that regulation of iron homeostasis processes is important for symbiotic maintenance.

The purification of the σ/FpvR and σ/FpvR protein complexes is facilitated at room temperature.

Bacteria contain sigma (σ) factors that control gene expression in response to various environmental stimuli. The alternative sigma factors σ and σ bind specifically to the antisigma factor FpvR. These proteins are an essential component of the pyoverdine-based system for iron uptake in Pseudomonas aeruginosa.