skip to main content

This content will become publicly available on January 16, 2025

Title: Altering the interfacial rheology of Pseudomonas aeruginosa and Staphylococcus aureus with N-acetyl cysteine and cysteamine

Chronic lung infection due to bacterial biofilms is one of the leading causes of mortality in cystic fibrosis (CF) patients. Among many species colonizing the lung airways,Pseudomonas aeruginosaandStaphylococcus aureusare two virulent pathogens involved in mechanically robust biofilms that are difficult to eradicate using airway clearance techniques like lung lavage. To remove such biological materials, glycoside hydrolase-based compounds are commonly employed for targeting and breaking down the biofilm matrix, and subsequently increasing cell susceptibility to antibiotics.

Materials and methods

In this study, we evaluate the effects of N-acetyl cysteine (NAC) and Cysteamine (CYST) in disrupting interfacial bacterial films, targeting different components of the extracellular polymeric substances (EPS). We characterize the mechanics and structural integrity of the interfacial bacterial films using pendant drop elastometry and scanning electron microscopy.

Results and discussion

Our results show that the film architectures are compromised by treatment with disrupting agents for 6 h, which reduces film elasticity significantly. These effects are profound in the wild type and mucoidP. aeruginosa, compared toS. aureus. We further assess the effects of competition and cooperation betweenS. aureusandP. aeruginosaon the mechanics of composite interfacial films. Films ofS. aureusand wild-typeP. aeruginosacocultures lose mechanical strength while those ofS. aureusand mucoidP. aeruginosaexhibit improved storage modulus. Treatment with NAC and CYST reduces the elastic property of both composite films, owing to the drugs’ ability to disintegrate their EPS matrix. Overall, our results provide new insights into methods for assessing the efficacy of mucolytic agents against interfacial biofilms relevant to cystic fibrosis infection.

more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Date Published:
Journal Name:
Frontiers in Cellular and Infection Microbiology
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Background

    Chronic rhinosinusitis (CRS) is a significant manifestation of cystic fibrosis (CF) with wide‐ranging symptom and disease severity. The goal of the study was to determine clinical variables that correlate with outcome measures of disease severity.


    A prospective, longitudinal, observational study of 33 adults with symptomatic CRS treated in a CF‐focused otolaryngology clinic was performed. Symptom severity, the presence of rhinosinusitis exacerbations, and endoscopic appearance were assessed, and regression analysis was used to determine clinical predictors of disease outcome.


    Thirty‐three adults with CF‐CRS were included in the study and followed for a mean of 15 months. Rhinosinusitis exacerbations occurred in 61% of participants during the study, and female sex increased the odds of presenting with an exacerbation visit. Sinus disease exacerbations were associated with an odds ratio of 2.07 for presenting with a pulmonary exacerbation at the next visit. CF‐related diabetes was found to be associated with worse symptoms and endoscopic appearance. Infection withStaphylococcus aureuspredicted worsening of symptoms, whereas infections withPseudomonas aeruginosaimproved over time. Allergic rhinitis was associated with worse endoscopic appearance, and nasal steroid use was associated with improved endoscopic appearance.


    Sex, CF‐related diabetes, sinonasal infection status, allergic rhinitis, and nasal steroid use may all modulate severity of CF‐CRS in adults. Sinusitis exacerbation may be a precursor to pulmonary exacerbation.

    more » « less
  2. Background

    The purpose of this retrospective review was to determine how patient‐related factors and culture data affect neo‐osteogenesis in patients with chronic rhinosinusitis (CRS) and patients with cystic fibrosis (CF) with CRS.


    Information from a database associated with a large tertiary medical center was used to assess adult patients with CF CRS and non‐CF CRS (total, n = 102; CF CRS, n = 31; non‐CF CRS, n = 71). Radiologic evidence of neo‐osteogenesis was measured using the Global Osteitis Scoring Scale (GOSS), and mucosal disease was assessed using the Lund‐Mackay score (LMS) by 2 independent reviewers who were blinded to the patient's disease state. Bacterial cultures were obtained endoscopically. Multiple logistic regression models were used to evaluate the effect of age, sex, number of previous surgeries, CF, and culture species on the odds of neo‐osteogenesis.


    Fifty‐one of the 102 patients (50%) met radiologic criteria for neo‐osteogenesis. Sixty‐nine patients (67.6%) with CF CRS and non‐CF CRS had culture data. In the multiple logistic regression model, male gender was significantly associated with neo‐osteogenesis (odds ratio [OR], 5.2; 95% confidence interval [CI], 1.68‐17.86;p= 0.006).Pseudomonas aeruginosawas not associated with neo‐osteogenesis (OR, 3.12; 95% CI, 0.84‐12.80;p= 0.097). Age, number of surgeries, CF,Staphylococcus aureus, and coagulase‐negativeStaphylococcuswere not statistically significant.


    To our knowledge, this is the first study to assess risk factors associated with neo‐osteogenesis and patients with CF CRS. Interestingly, male gender was the only significant predictor of neo‐osteogenesis.

    more » « less
  3. Abstract

    Bacterial infections in cystic fibrosis (CF) patients are an emerging health issue and lead to a premature death. CF is a hereditary disease that creates a thick mucus in the lungs that is prone to bacterial biofilm formation, specificallyPseudomonas aeruginosabiofilms. These biofilms are very difficult to treat because many of them have antibiotic resistance that is worsened by the presence of extracellular DNA (eDNA). eDNA helps to stabilize biofilms and can bind antimicrobial compounds to lessen their effects. The metallo‐antimicrobial peptide Gaduscidin‐1 (Gad‐1) eradicates establishedP. aeruginosabiofilms through a combination of modes of action that includes nuclease activity that can cleave eDNA in biofilms. In addition, Gad‐1 exhibits synergistic activity when used with the antibiotics kanamycin and ciprofloxacin, thus making Gad‐1 a new lead compound for the potential treatment of bacterial biofilms in CF patients.

    more » « less
  4. Abstract Objectives

    To assess the ability of oxyclozanide to enhance tobramycin killing of Pseudomonas aeruginosa biofilms and elucidate its mechanism of action.


    Twenty-four hour biofilms formed by the P. aeruginosa strain PAO1 and cystic fibrosis (CF) isolates were tested for susceptibility to oxyclozanide and tobramycin killing using BacTiter-Glo™ and cfu. Biofilm dispersal was measured using crystal violet staining. Membrane potential and permeabilization were quantified using DiOC2(3) and TO-PRO-3, respectively.


    Here we show that the ionophore anthelmintic oxyclozanide, combined with tobramycin, significantly increased killing of P. aeruginosa biofilms over each treatment alone. This combination also significantly accelerated the killing of cells within biofilms and stationary phase cultures and it was effective against 4/6 CF clinical isolates tested, including a tobramycin-resistant strain. Oxyclozanide enhanced the ability of additional aminoglycosides and tetracycline to kill P. aeruginosa biofilms. Finally, oxyclozanide permeabilized cells within the biofilm, reduced the membrane potential and increased tobramycin accumulation within cells of mature P. aeruginosa biofilms.


    Oxyclozanide enhances aminoglycoside and tetracycline activity against P. aeruginosa biofilms by reducing membrane potential, permeabilizing cells and enhancing tobramycin accumulation within biofilms. We propose that oxyclozanide counteracts the adaptive resistance response of P. aeruginosa to aminoglycosides, increasing both their maximum activity and rate of killing. As oxyclozanide is widely used in veterinary medicine for the treatment of parasitic worm infections, this combination could offer a new approach for the treatment of biofilm-based P. aeruginosa infections, repurposing oxyclozanide as an anti-biofilm agent.

    more » « less
  5. Although destructive airway disease is evident in young children with cystic fibrosis (CF), little is known about the nature of the early CF lung environment triggering the disease. To elucidate early CF pulmonary pathophysiology, we performed mucus, inflammation, metabolomic, and microbiome analyses on bronchoalveolar lavage fluid (BALF) from 46 preschool children with CF enrolled in the Australian Respiratory Early Surveillance Team for Cystic Fibrosis (AREST CF) program and 16 non-CF disease controls. Total airway mucins were elevated in CF compared to non-CF BALF irrespective of infection, and higher densities of mucus flakes containing mucin 5B and mucin 5AC were observed in samples from CF patients. Total mucins and mucus flakes correlated with inflammation, hypoxia, and oxidative stress. Many CF BALFs appeared sterile by culture and molecular analyses, whereas other samples exhibiting bacterial taxa associated with the oral cavity. Children without computed tomography–defined structural lung disease exhibited elevated BALF mucus flakes and neutrophils, but little/no bacterial infection. Although CF mucus flakes appeared “permanent” because they did not dissolve in dilute BALF matrix, they could be solubilized by a previously unidentified reducing agent (P2062), but not N -acetylcysteine or deoxyribonuclease. These findings indicate that early CF lung disease is characterized by an increased mucus burden and inflammatory markers without infection or structural lung disease and suggest that mucolytic and anti-inflammatory agents should be explored as preventive therapy. 
    more » « less