Evaluation of a novel rapidly-growing mycobacteria medium for isolation of Mycobacterium abscessus complex from respiratory specimens from patients with bronchiectasis

Abstract

This single center study assessed the performance of a novel solid rapidly-growing mycobacteria (RGM) medium for the recovery of nontuberculous mycobacteria (NTM), especially Mycobacterium abscessus complex, in patients with underlying bronchiectasis. A total of 297 mycobacterial sputa from 116 patients were plated directly on RGM medium and, following decontamination, onto an agar biplate [Middlebrook 7H11 and Mitchison (selective) agar] and into broth media (VersaTrek). The recovery of M. abscessus complex was increased by approximately 12% by implementation of the RGM medium. Contamination was reduced to 2% from 48% and 95% on routine solid media and broth cultures respectively. Our study corroborated previous studies in that recovery of M. abscessus complex was enhanced and contamination was virtually eliminated without the need for specimen decontamination when utilizing RGM medium.

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

“…With respect to MAC, there was a lower impact of the various decontamination treatments examined here, with NALC-NaOH reducing the viable count by 28.9%. This is consistent with the fact that there is little, if any, advantage of using RGM medium for isolation of MAC when compared to AFB culture, as documented in previous studies [ 7 , 19 , 20 , 21 ]. A limitation of this paper is that we are not able to offer conclusions on NTMs other than MABSC and MAC.…”

“…This effect is particularly acute for treatments containing NaOH against MABSC. This supports the abundance of recently acquired evidence showing that the optimal recovery of MABSC is achieved by culture on an appropriate selective agar, without decontamination of sputum samples [ 7 , 19 , 21 ].…”

Mycobacterium biofilms

“…However, most NTM can also be isolated with these systems, and criteria for the interpretation of the microbiological results have been developed for a clear interpretation of the isolation of these environmental species [ 58 ]. In the present moment, some specific media for NTM have been developed and have been used, not only for clinical samples, but for environmental ones [ [85] , [86] , [87] ]. These later samples are of special interest, because NTM grow in them as part of polymicrobial biofilms, and because the slow growing of all species (compared with other bacteria) the isolation of them can be problematic.…”