Decontamination Strategies Used for AFB Culture Significantly Reduce the Viability of Mycobacterium abscessus Complex in Sputum Samples from Patients with Cystic Fibrosis

Abstract

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.

Recovery of Mycobacteria from Heavily Contaminated Environmental Matrices

“…We therefore accept that the unambiguous determination of the yield could be skewed by the difficulty of determining the true measurement of the presence of viable mycobacteria in the examined samples (missed blank samples). Yield can be affected of course by the decontamination method due to sensitivity of some mycobacterial species to a decontamination agent [ 66 ]. Cultivation may be (and will be in further work) refined by using special cultivation media (e.g., RGM) [ 67 ].…”

Azide-Masked and Trehalose-based Fluorescence Turn-On Probe for Mycobacteria

“…The sputum samples were then processed using N-acetyl-L-cysteine/sodium hydroxide (NalC/NaOH) to digest the sputa and to reduce the growth of non-acid fast bacilli. [47][48][49] The processed sputum samples were spiked with 10 8 CFU/mL M. smegmatis and were treated with Tre-Cz in the same manner as M. smegmatis. Confocal fluorescence microscopy showed that Tre-Cz could indeed image mycobacteria in sputum.…”

Granulomatosis with polyangiitis diagnosed during the treatment of otitis media with prednisolone in a patient with anti-neutrophil cytoplasmic antibody-associated vasculitis: A case report

“…However, no mycobacterial growth was detected on culture. This may be attributed to the death of the bacteria in the process of digestion and decontamination of the specimen [ 13 ]. Based on the findings on microbiological examination and lung imaging, we considered the patient to have NTM-PD.…”