A novel culture medium for isolation of rapidly-growing mycobacteria from the sputum of patients with cystic fibrosis

Preece, Clair; Perry, Audrey; Gray, Bethany; Kenna, D.; Jones, Amanda; Cummings, Stephen; Robb, A.; Thomas, Matthew F.; Brodlie, Malcolm; O’Brien, Christopher J.; Bourke, Stephen; Perry, John D.

doi:10.1016/j.jcf.2015.05.002

Cited by 35 publications

(39 citation statements)

References 27 publications

(25 reference statements)

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“…44347) for the isolation of mycobacteria from 502 sputum samples. Mycobacteria were detected in 54 samples using RGM medium and in only 17 samples using Cepacia selective agar (P Յ 0.0001) (18). As media for the isolation of B. cepacia have been recommended for the isolation of mycobacteria, this prompted us to examine different commercial brands of such media, to compare their abilities to support the growth of rapidly growing mycobacteria and their selectivity against other flora associated with CF sputum samples.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Various Culture Media for Detection of Rapidly Growing Mycobacteria from Patients with Cystic Fibrosis

et al. 2016

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cIsolation of nontuberculous mycobacteria (NTM) from the sputum of patients with cystic fibrosis (CF) is challenging due to overgrowth by rapidly growing species that colonize the lungs of patients with CF. Extended incubation on Burkholderia cepacia selective agar (BCSA) has been recommended as an expedient culture method for the isolation of rapidly growing NTM in this setting. The aim of this study was to assess five selective media designed for the isolation of Burkholderia cepacia complex, along with two media designed for the isolation of mycobacteria (rapidly growing mycobacteria [RGM] medium and Middlebrook 7H11 agar), for their abilities to isolate NTM. All seven media were challenged with 147 isolates of rapidly growing mycobacteria and 185 isolates belonging to other species. RGM medium was then compared with the most selective brand of BCSA for the isolation of NTM from 224 sputum samples from patients with CF. Different agars designed for the isolation of B. cepacia complex varied considerably in their inhibition of other bacteria and fungi. RGM medium supported the growth of all isolates of mycobacteria and was more selective than any other medium. NTM were recovered from 17 of 224 sputum samples using RGM medium, compared with only 7 samples using the most selective brand of BCSA (P ‫؍‬ 0.023). RGM medium offers a superior option, compared to other selective agars, for the isolation of rapidly growing mycobacteria from the sputum of patients with CF. Furthermore, the convenience of using RGM medium enables routine screening for rapidly growing NTM in all submitted sputum samples from patients with CF. Burkholderia cepacia complex (BCC) and nontuberculous mycobacteria (NTM) are both recognized as potentially important pathogens when isolated from the lungs of patients with cystic fibrosis (CF). The use of a selective culture medium is recommended for the isolation of BCC (1), and several brands of such media are commercially available. Rapidly growing mycobacteria (RGM) represent a subset of NTM that generate colonies on solid culture media within 7 days of incubation (2). The predominant species of NTM within the CF population in Europe is Mycobacterium abscessus complex (MABSC) (3-5), and there is convincing evidence that the prevalence of infection by MABSC in the CF population is increasing (3,(5)(6)(7). This rapidly growing species comprises three subspecies, i.e., Mycobacterium abscessus subsp. abscessus, Mycobacterium abscessus subsp. bolletii, and Mycobacterium abscessus subsp. massiliense.Culture of mycobacteria from sputum samples has traditionally relied on methods that were designed to accommodate slowly growing mycobacteria, particularly Mycobacterium tuberculosis, which is comparatively rare among cystic fibrosis patients. Such methods are laborious and expensive, as they involve chemical decontamination of samples and subsequent culture on both liquid and solid media (8, 9). Furthermore, contamination of cultures by faster growing microorganisms may mean that cultures have to be aban...

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Section: Discussionmentioning

confidence: 99%

Evaluation of Various Culture Media for Detection of Rapidly Growing Mycobacteria from Patients with Cystic Fibrosis

et al. 2016

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“…In the first published evaluation of the use of RGM medium, Preece et al demonstrated performance superior to the use of BCSA for recovery of mycobacteria (11). The study examined 502 consecutive sputum samples from patients with CF in the United Kingdom and reported that 54 isolates of NTM were recovered on RGM medium versus 17 recovered on BCSA (P Յ 0.0001).…”

Section: Discussionmentioning

confidence: 99%

“…However, not all NTM will grow on BCSA and overgrowth, particularly by fungi and Gram-negative bacteria, remains a problem (10). Preece et al (11) recently described a new selective agar, RGM medium, to target rapidly growing species of mycobacteria, which represent the dominant species in many geographical areas (3,4,12). The sensitivity of RGM medium proved to be clearly superior to that of BCSA when evaluated with 502 sputum samples from patients with CF.…”

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Comparison of Mycobacterial Growth Indicator Tube with Culture on RGM Selective Agar for Detection of Mycobacteria in Sputum Samples from Patients with Cystic Fibrosis

et al. 2016

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dNontuberculous mycobacteria (NTM) are an important cause of pulmonary disease in patients with cystic fibrosis (CF). A new culture medium (RGM medium) for the isolation of rapidly growing mycobacteria from the sputum of cystic fibrosis patients has recently been reported. The aim of this study was to compare culture of sputum samples on RGM medium with culture using a standard automated liquid culture method. Sputum samples were obtained from 187 distinct patients with CF attending King's College Hospital, London, United Kingdom. Each sample was decontaminated with 3% oxalic acid and inoculated into a mycobacterial growth indicator tube (MGIT) that was monitored for 42 days using the Bactec MGIT 960 instrument. Each sample was also cultured, without decontamination, onto RGM medium, which was incubated for 10 days at 30°C. Mycobacteria were isolated from 28 patients (prevalence, 15%). Mycobacteria were detected in 24 samples (86%) using the MGIT and in 23 samples (82%) using RGM medium (P ‫؍‬ 1.00). In this setting, RGM medium showed sensitivity equivalent to that of the MGIT for isolation of NTM from the sputum of patients with CF. RGM medium offers a simple, convenient tool that can be embedded into routine culture methods, allowing the culture of all sputum samples that are submitted from patients with CF. N ontuberculous mycobacteria (NTM) are an important cause of pulmonary disease in patients with cystic fibrosis (CF) (1). In the largest studies, the prevalence of NTM in sputum has been estimated to be 6 to 13% for patients with CF (2), and there is convincing evidence that prevalence is increasing in the CF population (3-6). NTM are detected by culture of sputum using methods that were designed primarily for the isolation of Mycobacterium tuberculosis. Consensus guidelines state that culture should be performed in liquid media using an automated growth detection system (such as the mycobacterial growth indicator tube [MGIT]) and note that concomitant culture on solid media (e.g., Lowenstein-Jensen medium) may increase the diagnostic yield (1).Detection of NTM is frequently challenging due to the presence of other bacterial and fungal species in the lungs of CF patients. Competing species typically show a higher growth rate than mycobacteria and are frequently resistant to multiple antibiotics that might be used to select for growth of mycobacteria. To resolve this, sputum samples are subjected to treatment with chemicals in order to eliminate or reduce the burden of nonmycobacterial species. Chemical treatments include N-acetyl-L-cysteine (0.5%) plus sodium hydroxide (2%), 5% oxalic acid, or 1% chlorhexidine (1). However, such decontamination protocols are labor intensive, they may reduce the viability of NTM, and they may be ultimately unsuccessful if there is a high burden of nonmycobacterial species (7-9).Culture on solid agar-based media is an attractive option as this can potentially allow recovery of NTM even in specimens that contain other viable species. For example, Esther et al. (10) demonstrat...

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“…We also found that isolates were obtained from a gastric source with MABSC negative sputa. MABSC were therefore identified for the first time from a gastric sample in these patients, despite rigorous and extended previous sputum based surveillance in a tertiary laboratory, with a specialised interest in MABSC culture methodology16.…”

Section: Discussionmentioning

confidence: 99%

Nontuberculous mycobacteria in gastrostomy fed patients with cystic fibrosis

Al-Momani

Perry

Jones

et al. 2017

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Multi-drug resistant Mycobacterium abscessus complex (MABSC) is a form of Nontuberculous mycobacteria (NTM) of special, international concern in Cystic Fibrosis (CF). We hypothesised that gastric juice and percutaneous endoscopic gastrostomy (PEG) feeding devices might yield MABSC isolates. Gastric juice and sputa from sixteen adult PEG fed CF patients and five replaced PEG tubes were studied. Bacterial and fungal isolates were cultured. Mycobacterium were identified by rpoB, sodA and hsp65 gene sequencing and strain typed using variable number tandem repeat. Bacteria and/or fungi grew from all gastric juice, sputa and PEG samples. MABSC were detected in 7 patients. Five had MABSC in their sputum. Two had an identical MABSC strain in their sputum and gastric juice and one had the same strain isolated from their PEG tube and sputum. Two patients who were sputum sample negative had MABSC isolated in their gastric juice or PEG tube. MABSC were therefore identified for the first time from a gastric sample in a minority of patients. We conclude that gastric juice and PEG-tubes may be a potential source of MABSC isolates in CF patients, and these findings warrant further study.

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A novel culture medium for isolation of rapidly-growing mycobacteria from the sputum of patients with cystic fibrosis

Cited by 35 publications

References 27 publications

Evaluation of Various Culture Media for Detection of Rapidly Growing Mycobacteria from Patients with Cystic Fibrosis

Evaluation of Various Culture Media for Detection of Rapidly Growing Mycobacteria from Patients with Cystic Fibrosis

Comparison of Mycobacterial Growth Indicator Tube with Culture on RGM Selective Agar for Detection of Mycobacteria in Sputum Samples from Patients with Cystic Fibrosis

Nontuberculous mycobacteria in gastrostomy fed patients with cystic fibrosis

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