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Decontamination strategies used for afb culture significantly reduce the viability of Mycobacterium abscessus complex in sputum samples from patients with cystic fibrosis

Lookup NU author(s): Dr Stephen Bourke, Dr John Perry



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2021 by the authors. Licensee MDPI, Basel, Switzerland. Nontuberculous mycobacteria are important respiratory pathogens in patients with cystic fibrosis (CF). For diagnosis, international guidelines recommend culture of sputum that has been decontaminated via chemical treatment. Fifty‐six sputum samples from 32 patients known to be previously colonized or infected with NTM were subdivided, and the aliquots were subjected to six different decontamination strategies, followed by quantitative culture for NTM. Thirty sputum samples contained Mycobacterium abscessus complex (MABSC) and 11 contained Mycobacterium avium complex (MAC). Decontamination strategies included treatment with N‐acetyl L‐cysteine with 2% sodium hydroxide (NALC‐NaOH), 4% NaOH, 1% chlorhexidine, 0.5 N sulfuric acid, 5% oxalic acid, double decontamination with NALC‐NaOH, followed by 5% oxalic acid, and saline (0.85%) as a control. The samples were also cultured directly with no treatment. Treatment with NALC‐NaOH resulted in an average reduction in colony count of 87% for MABSC when compared with direct culture. NaOH at 4% caused a 98.3% average reduction in colony count. All treatments that included NaOH resulted in colony counts that were statistically lower than those obtained from direct culture or the saline‐treated control (p < 0.05). Standard treatments using sulfuric or oxalic acids were less deleterious, but still resulted in an average reduction in colony count of at least 30%. The viability of MAC was much less affected by most decontamination treatments. In conclusion, the viability of MABSC was severely compromised by standard decontamination regimens. This supports recent evidence showing that optimal recovery of MABSC is achieved by culture on an appropriate selective agar without decontamination of sputum samples.

Publication metadata

Author(s): Stephenson D, Perry A, Nelson A, Robb AE, Thomas MF, Bourke SJ, Perry JD, Jones AL

Publication type: Article

Publication status: Published

Journal: Microorganisms

Year: 2021

Volume: 9

Issue: 8

Online publication date: 27/07/2021

Acceptance date: 23/07/2021

Date deposited: 12/08/2021

ISSN (electronic): 2076-2607

Publisher: MDPI AG


DOI: 10.3390/microorganisms9081597


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