Standard versus biofilm antimicrobial susceptibility testing to guide antibiotic therapy in cystic fibrosis

Smith, Sherie; Waters, Valerie; Jahnke, Nikki; Ratjen, Félix

doi:10.1002/14651858.cd009528.pub5

“…The amount of antibiotic required to achieve 3 log 10 killing of EVPL-grown bacteria is often significantly higher than the MIC or the MBEC calculated from standard in vitro assays, even when SCFM is used for these assays (Figure 3). This is consistent with a Cochrane review that reported that current implementations of in vitro biofilm susceptibility testing do not provide any increased predictive power for antibiotic prescribing in CF compared to standard susceptibility testing 16 .…”

Section: Representative Resultssupporting

confidence: 89%

“…the Calgary biofilm device, which uses biofilms grown on the surface of plastic pegs set within the wells of a microplate containing standard AST medium (e.g., cationadjusted Muller-Hinton broth) 14 , 15 . This assay does no better at predicting which antibiotics will work in vivo than standard planktonic AST 16 . The impact on patients with CF is stark.…”

Section: Introductionmentioning

confidence: 98%

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

Harrington

¹

,

Sweeney

²

,

Alav

³

et al. 2021

JoVE

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The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a poor correlation between antibiotic susceptibility testing (AST) results using standard diagnostic methods (e.g., broth microdilution, disk diffusion, or Etest) and clinical outcomes after antibiotic treatment. Attempts to improve AST by the use of off-the-shelf biofilm growth platforms show little improvement in results. The limited ability of in vitro biofilm systems to mimic the physicochemical environment of the CF lung and, therefore bacterial physiology and biofilm architecture, also acts as a brake on the discovery of novel therapies for CF infection. Here, we present a protocol to perform AST of CF pathogens grown as mature, in vivo-like biofilms in an ex vivo CF lung model comprised of pig bronchiolar tissue and synthetic CF sputum (ex vivo pig lung, EVPL).Several in vitro assays exist for biofilm susceptibility testing, using either standard laboratory medium or various formulations of synthetic CF sputum in microtiter plates.Both growth medium and biofilm substrate (polystyrene plate vs. bronchiolar tissue) are likely to affect biofilm antibiotic tolerance. We show enhanced tolerance of clinical Pseudomonas aeruginosa and Staphylococcus aureus isolates in the ex vivo model; the effects of antibiotic treatment of biofilms is not correlated with the minimum inhibitory concentration (MIC) in standard microdilution assays or a sensitive/resistant classification in disk diffusion assays.The ex vivo platform could be used for bespoke biofilm AST of patient samples and as an enhanced testing platform for potential antibiofilm agents during pharmaceutical research and development. Improving the prescription or acceleration of antibiofilm drug discovery through the use of more in vivo-like testing platforms could drastically

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“…Most if not all of the described host and microbial factors are absent in conventional AST, and the biofilm phenotype and phenotypic diversity of P. aeruginosa observed in vivo, are not captured. Nevertheless, clinical studies focusing on biofilm susceptibility to guide antibiotic therapy did not show an improvement in P. aeruginosa density in sputum or lung function parameters compared with conventional AST [175]. Hence, mimicking the biofilm phenotype alone may not be sufficient to fill the gap between in vitro and in vivo antibiotic susceptibility.…”

Section: Mediators Of the Immune Responsementioning

confidence: 99%

The cystic fibrosis lung microenvironment alters antibiotic activity: causes and effects

Bossche

¹

,

Broe

²

,

Coenye

³

et al. 2021

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Chronic airway colonisation by Pseudomonas aeruginosa, a hallmark of cystic fibrosis (CF) lung disease, is associated with increased morbidity and mortality and despite aggressive antibiotic treatment, P. aeruginosa is able to persist in CF airways. In vitro antibiotic susceptibility assays are poor predictors of antibiotic efficacy to treat respiratory tract infections in the CF patient population and the selection of the antibiotic(s) is often made on an empirical base. In the current review, we discuss the factors that are responsible for the discrepancies between antibiotic activity in vitro and clinical efficacy in vivo. We describe how the CF lung microenvironment, shaped by host factors (such as iron, mucus, immune mediators and oxygen availability) and the microbiota, influences antibiotic activity and varies widely between patients. A better understanding of the CF microenvironment and population diversity may thus help improve in vitro antibiotic susceptibility testing and clinical decision making, in turn increasing the success rate of antibiotic treatment.

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“…Make a final cross-sectional incision across the bronchiole before any branching is visible to remove the bronchiole from the lungs. 16. Place the bronchiole in the first DMEM/RPMI 1640 wash.…”

Section: Dissection and Infection Of Ex Vivo Pig Lung (Evpl) Tissuementioning

confidence: 99%

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

Harrington

¹

,

Sweeney

²

,

Alav

³

et al. 2021

JoVE

View full text Add to dashboard Cite

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a poor correlation between antibiotic susceptibility testing (AST) results using standard diagnostic methods (e.g., broth microdilution, disk diffusion, or Etest) and clinical outcomes after antibiotic treatment. Attempts to improve AST by the use of off-the-shelf biofilm growth platforms show little improvement in results. The limited ability of in vitro biofilm systems to mimic the physicochemical environment of the CF lung and, therefore bacterial physiology and biofilm architecture, also acts as a brake on the discovery of novel therapies for CF infection. Here, we present a protocol to perform AST of CF pathogens grown as mature, in vivo-like biofilms in an ex vivo CF lung model comprised of pig bronchiolar tissue and synthetic CF sputum (ex vivo pig lung, EVPL).Several in vitro assays exist for biofilm susceptibility testing, using either standard laboratory medium or various formulations of synthetic CF sputum in microtiter plates.Both growth medium and biofilm substrate (polystyrene plate vs. bronchiolar tissue) are likely to affect biofilm antibiotic tolerance. We show enhanced tolerance of clinical Pseudomonas aeruginosa and Staphylococcus aureus isolates in the ex vivo model; the effects of antibiotic treatment of biofilms is not correlated with the minimum inhibitory concentration (MIC) in standard microdilution assays or a sensitive/resistant classification in disk diffusion assays.The ex vivo platform could be used for bespoke biofilm AST of patient samples and as an enhanced testing platform for potential antibiofilm agents during pharmaceutical research and development. Improving the prescription or acceleration of antibiofilm drug discovery through the use of more in vivo-like testing platforms could drastically

show abstract

Standard versus biofilm antimicrobial susceptibility testing to guide antibiotic therapy in cystic fibrosis

Cited by 16 publications

References 38 publications

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

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 cystic fibrosis lung microenvironment alters antibiotic activity: causes and effects

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

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