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An invisible threat? Aspergillus positive cultures and co-infecting bacteria in airway sample

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Title: An invisible threat? Aspergillus positive cultures and co-infecting bacteria in airway sample
Authors: Davies, J
Hughes, D
Rosenthal, M
Cuthbertson, L
Ramadan, N
Felton, I
Simmonds, N
Loebinger, M
Price, H
Armstrong-James, D
Elborn, S
Cookson, W
Moffatt, M
Item Type: Journal Article
Abstract: Background Aspergillus fumigatus (Af) infection is associated with poor lung health in chronic suppurative lung diseases but often goes undetected. We hypothesised that inhibition of Af growth by Pseudomonas aeruginosa (Pa) increases the frequency of false-negative Af culture in co-infected people. Using a substantial group of cystic fibrosis (CF) airway samples, we assessed the relationship between Af and bacterial pathogens, additionally comparing fungal culture with next-generation sequencing. Methods Frequency of co-culture was assessed for 44,554 sputum/BAL cultures, from 1,367 CF patients between the years 2010–2020. In a subgroup, Internal Transcribed Spacer-2 (ITS2) fungal sequencing was used to determine sequencing-positive, culture-negative (S+/C-) rates. Results Pa+ samples were nearly 40% less likely (P<0.0001) than Pa- samples to culture Af, an effect that was also seen with some other Gram-negative isolates. This impact varied with Pa density and appeared to be moderated by Staphylococcus aureus co-infection. Sequencing identified Af-S+/C- for 40.1% of tested sputa. Samples with Pa had higher rates of Af-S+/C- (49.3%) than those without (35.7%; RR 1.38 [1.02–1.93], P<0.05). Af-S+/C- rate was not changed by other common bacterial infections. Pa did not affect the S+/C- rates of Candida, Exophiala or Scedosporium. Conclusions Pa/ Af co-positive cultures are less common than expected in CF. Our findings suggest an Af-positive culture is less likely in the presence of Pa. Interpretation of negative cultures should be cautious, particularly in Pa-positive samples, and a companion molecular diagnostic could be useful. Further work investigating mechanisms, alternative detection techniques and other chronic suppurative lung diseases is needed.
Issue Date: 1-Mar-2023
Date of Acceptance: 12-Jul-2022
URI: http://hdl.handle.net/10044/1/98514
DOI: 10.1016/j.jcf.2022.07.009
ISSN: 1569-1993
Publisher: Elsevier
Start Page: 320
End Page: 326
Journal / Book Title: Journal of Cystic Fibrosis
Volume: 22
Issue: 2
Copyright Statement: © 2022 The Authors. Published by Elsevier B.V. on behalf of European Cystic Fibrosis Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Publication Status: Published
Online Publication Date: 2022-07-22
Appears in Collections:National Heart and Lung Institute
Faculty of Medicine

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