galleria-mellonella-as-an-antimicrobial-screening-model

<i>Galleria mellonella</i> as an Antimicrobial Screening Model

To combat the rising global issue of antibiotic resistance, the accelerated development of novel antibiotics is essential. Current preclinical ...

cystic-fibrosis-aggregate-biofilm-model-to-study-infection-relevant

Cystic Fibrosis Aggregate Biofilm Model to Study Infection-relevant Gene Expression

Standard pre-clinical testing methods for novel antimicrobial therapeutics used to treat chronic lung infections in people with cystic fibrosis do not ...

University of Dundee

 is the dominant  pathogen recovered from lung infection in people with cystic fibrosis. However, as an understudied pathogen there are knowledge gaps in relation to its population biology, phenotypic traits and useful model strains. A phylogenomic study of  was undertaken using a total of 283 genomes, of which 73 were sequenced and 49 phenotypically characterized as part of this study. Average nucleotide identity analysis (ANI) and phylogenetic alignment of core genes demonstrated that the  population separated into two distinct evolutionary clades, defined as lineage 1 (=58 genomes) and lineage 2 (=221 genomes). To examine the population biology of , a representative subgroup of 77  genomes (28 from the reference databases and the 49 novel short-read genome sequences) were selected based on multilocus sequence typing (MLST), isolation source and phylogenetic placement criteria. Comparative genomics was used to identify  lineage-specific genes -  in lineage 1 and  in lineage 2 - and diagnostic PCRs targeting them were successfully developed. Phenotypic analysis of 49 representative  strains showed considerable inter-strain variance, but the majority of the isolates tested were motile and capable of biofilm formation. A striking absence of  protease activity  was observed, but no lineage-specific phenotypic differences were demonstrated. Using phylogenomic and phenotypic criteria, three model  CF strains were identified, BCC0084 (lineage 1), BCC1272 (lineage 2a) and BCC0033 lineage 2b, and their complete genome sequences determined.  CF strains BCC0033 and BCC0084, and the environmental reference strain, ATCC 17616, were all capable of short-term survival within a murine lung infection model. By mapping the population biology, identifying lineage-specific PCRs and model strains, we provide much needed baseline resources for future studies of .

Identification of two distinct phylogenomic lineages and model strains for the understudied cystic fibrosis lung pathogen .

 is an opportunistic pathogen that is responsible for infections in people living with chronic respiratory conditions, such as cystic fibrosis (CF) and non-CF bronchiectasis (NCFB). Traditionally, in people with chronic respiratory disorders,  infection has been managed with a combination of inhaled and intravenous antibiotic therapies. However, due in part to the prolonged use of antibiotics in these people, the emergence of multi-drug resistant  strains is a growing concern. The development of anti-virulence therapeutics may provide a new means of treating  lung infections whilst also combatting the AMR crisis, as these agents are presumed to exert reduced pressure for the emergence of drug resistance as compared to antibiotics. However, the pipeline for developing anti-virulence therapeutics is poorly defined, and it is currently unclear as to whether  and  models effectively replicate the complex pulmonary environment sufficiently to enable development and testing of such therapies for future clinical use. Here, we discuss potential targets for  anti-virulence therapeutics and the effectiveness of the current models used to study them. Focus is given to the difficulty of replicating the virulence gene expression patterns of  in the CF and NCFB lung under laboratory conditions and to the challenges this poses for anti-virulence therapeutic development.

Emerging strategies to target virulence in  respiratory infections.

Pseudomonas aeruginosa is a cause of chronic respiratory tract infections in people with cystic fibrosis (CF), non-CF bronchiectasis, and chronic obstructive pulmonary disease. Prolonged infection allows the accumulation of mutations and horizontal gene transfer, increasing the likelihood of adaptive phenotypic traits. Adaptation is proposed to arise first in bacterial populations colonizing upper airway environments. Here, we model this process using an experimental evolution approach. Pseudomonas aeruginosa PAO1, which is not airway adapted, was serially passaged, separately, in media chemically reflective of upper or lower airway environments. To explore whether the CF environment selects for unique traits, we separately passaged PAO1 in airway-mimicking media with or without CF-specific factors. Our findings demonstrated that all airway environments-sinus and lungs, under CF and non-CF conditions-selected for loss of twitching motility, increased resistance to multiple antibiotic classes, and a hyper-biofilm phenotype. These traits conferred increased airway colonization potential in an in vivo model. CF-like conditions exerted stronger selective pressures, leading to emergence of more pronounced phenotypes. Loss of twitching was associated with mutations in type IV pili genes. Type IV pili mediate surface attachment, twitching, and induction of cAMP signalling. We additionally identified multiple evolutionary routes to increased biofilm formation involving regulation of cyclic-di-GMP signalling. These included the loss of function mutations in bifA and dipA phosphodiesterase genes and activating mutations in the siaA phosphatase. These data highlight that airway environments select for traits associated with sessile lifestyles and suggest upper airway niches support emergence of phenotypes that promote establishment of lung infection.

Daniel R. Neill

Division of Molecular Microbiology,
School of Life Sciences,
Division of Molecular Microbiology, School of Life Sciences

University of Dundee

Galleria mellonella as an Antimicrobial Screening Model

Cystic Fibrosis Aggregate Biofilm Model to Study Infection-relevant Gene Expression

Daniel R. Neill

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Division of Molecular Microbiology,School of Life Sciences,Division of Molecular Microbiology, School of Life Sciences

University of Dundee

Galleria mellonella as an Antimicrobial Screening Model

Cystic Fibrosis Aggregate Biofilm Model to Study Infection-relevant Gene Expression

Division of Molecular Microbiology,
School of Life Sciences,
Division of Molecular Microbiology, School of Life Sciences