Transplantation infection
A novel model to study bacterial adherence to the transplanted airway: Inhibition of Burkholderia cepacia adherence to human airway by dextran and xylitol

https://doi.org/10.1016/j.healun.2003.09.023Get rights and content

Abstract

Background

Lung infection with Burkholderia cepacia complex before lung transplantation in patients with cystic fibrosis is a major risk factor for decreased post-operative survival rates compared with those of patients colonized with the more common opportunistic pathogen Pseudomonas aeruginosa. Because adherence to mucosal surfaces is an important initial step in infection, we investigated the use of non-toxic neutral polysaccharides and a sugar alcohol to prevent adherence of B cepacia complex to allograft airway epithelium.

Methods

We used human airway explants prepared from donor tracheobronchial tissue to test the effect of dextrans and xylitol in inhibiting the binding of Burkholderia cepacia complex. We used immunofluorescence and electron microscopy to determine the distribution of bacteria in the explants.

Results

Burkholderia cepacia complex bound to the explants and was found only in the surface mucus layer. Dextran 40 kd applied before adding the bacteria decreased the number of bound organisms by 80% to 99%. Smaller molecular mass dextrans (4 and 20 kd) were ineffective. Xylitol inhibited bacterial binding by 67% to 85%. Both agents seemed to decrease the thickness of the surface mucus, suggesting that they may indirectly inhibit bacterial binding by removing adherent surface mucus.

Conclusions

Treating donor lungs with dextran 40 kd or xylitol before (and possibly after) surgery may inhibit the adherence of Burkholderia cepacia complex to airways and may prevent or decrease subsequent infection of the allografts.

Section snippets

Bacteria and culture conditions

All Bcc isolates used in this study, except for ATCC 25416, were isolated from the sputa of patients with CF. We isolated BC7 (genomovar IIIa), which belongs to the ET12 clonal lineage and has been described previously,14, 23 from a Toronto patient with CF. C5393 (genomovar II), FC473 (genomovar IV), and CEP040 (genomovar V) are Bcc research panel isolates24 and were kindly provided by Dr. Mahenthiralingam (Cardiff School of Biosciences, Cardiff University, UK). ATCC 25416 (genomovar I) is an

Morphology of airway explants and immunostaining of mucins

Airway explants maintained in BEGM at an air-liquid interface for 24 hours showed normal pseudostratified epithelium composed of columnar ciliated cells, goblet cells, and basal cells (Figure 1A, arrows). A thick basement membrane, characteristic of proximal airways, was observed below the epithelium. Beneath the basement membrane was the lamina propria with richly vascularized connective tissue containing monocytes. The apical surface was covered with a mucuslike layer (Figure 1A, asterisks).

Discussion

We have demonstrated that airway explants obtained at the time of lung transplantation can be used to study bacterial adherence. This system models in part the in vivo situation, because it represents the ischemic, cold, stored human airway segments consisting of well-differentiated respiratory epithelia with mucus-secreting and ciliated cells and a protective coat of mucus covering the apical surface of intact epithelia. The 5 tested Bcc genomovars exhibited binding to the explants, and the

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