antibiotic-efficacy-testing-an-ex-vivo-model-pseudomonas-aeruginosa

Antibiotic Efficacy Testing in an Ex vivo Model of <em>Pseudomonas aeruginosa</em> and <em>Staphylococcus aureus</em> Biofilms in the Cystic Fibrosis Lung

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a ...

University of Warwick

Bacterial biofilms are known to have high antibiotic tolerance which directly affects clearance of bacterial infections in people with cystic fibrosis (CF). Current antibiotic susceptibility testing methods are either based on planktonic cells or do not reflect the complexity of biofilms . Consequently, inaccurate diagnostics affect treatment choice, preventing bacterial clearance and potentially selecting for antibiotic resistance. This leads to prolonged, ineffective treatment.

Predicting Antibiotic-Associated Virulence of  Using an  Lung Biofilm Model.

 is the most prevalent organism isolated from the airways of people with cystic fibrosis (CF), predominantly early in life. Yet its role in the pathology of lung disease is poorly understood. In mice, and many experiments using cell lines, the bacterium invades cells or interstitium, and forms abscesses. This is at odds with the limited available clinical data: interstitial bacteria are rare in CF biopsies and abscesses are highly unusual. Bacteria instead appear to localize in mucus plugs in the lumens of bronchioles. We show that, in an established  model of CF infection comprising porcine bronchiolar tissue and synthetic mucus,  demonstrates clinically significant characteristics including colonization of the airway lumen, with preferential localization as multicellular aggregates in mucus, initiation of a small colony variant phenotype and increased antibiotic tolerance of tissue-associated aggregates. Tissue invasion and abscesses were not observed. Our results may inform ongoing debates relating to clinical responses to  in people with CF.

An  cystic fibrosis model recapitulates key clinical aspects of chronic  infection.

 biofilms cause recalcitrant infections with extensive and unpredictable antibiotic tolerance. Here, we demonstrate increased tolerance of colistin by  when grown in medium that mimics cystic fibrosis (CF) sputum versus standard medium in  biofilm assays, and drastically increased tolerance when grown in an  CF model versus the  assay. We used colistin conjugated to the fluorescent dye BODIPY to assess the penetration of the antibiotic into  biofilms and showed that poor penetration partly explains the high doses of drug necessary to kill bacteria in these biofilms. The ability of antibiotics to penetrate the biofilm matrix is key to their clinical success, but hard to measure. Our results demonstrate both the importance of reduced entry into the matrix in -like biofilm, and the tractability of using a fluorescent tag and benchtop fluorimeter to assess antibiotic entry into biofilms. This method could be a relatively quick, cheap and useful addition to diagnostic and drug development pipelines, allowing the assessment of drug entry into biofilms, in -like conditions, prior to more detailed tests of biofilm killing.

Effect of host-mimicking medium and biofilm growth on the ability of colistin to kill .

 biofilm infections in the cystic fibrosis (CF) lung are highly resistant to current antimicrobial treatments and are associated with increased mortality rates. The existing models for such infections are not able to reliably mimic the clinical biofilms observed. We aimed to further optimise an  pig lung (EVPL) model for  CF lung infection that can be used to increase understanding of chronic CF biofilm infection. The EVPL model will facilitate discovery of novel infection prevention methods and treatments, and enhanced exploration of biofilm architecture. We investigated purine metabolism and biofilm formation in the model using transposon insertion mutants in  PA14 for key genes: ,  and . Our results demonstrate that EVPL recapitulates a key aspect of  infection metabolism, and that the pathogen forms a biofilm with a clinically realistic structure not seen in other  studies. Two pathways known to be required for  biofilm infection - the Gac regulatory pathway and production of the Pel exopolysaccharide - are essential to the formation of this mature, structured biofilm on EVPL tissue. We propose the high-throughput EVPL model as a validated biofilm platform to bridge the gap between  work and CF lung infection.

Esther Sweeney

School of Life Science

University of Warwick

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

Esther Sweeney

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University of Warwick

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

School of Life Science