Evaluation of RGM Medium for Isolation of Nontuberculous Mycobacteria from Respiratory Samples from Patients with Cystic Fibrosis in the United States

Plongla, Rongpong; Preece, Clair; Perry, John D.; Gilligan, Peter H.

doi:10.1128/jcm.02423-16

Cited by 28 publications

(33 citation statements)

References 22 publications

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“…Although the sensitivity of RGM30 with a 28-day incubation period was comparable to that of the MGIT system (P ϭ 0.6171) and Middlebrook 7H11 agar (P ϭ 0.3711) for the recovery of MABSC, RGM30 performed better for the recovery of all rapidly growing mycobacteria isolated in this study (P ϭ 0.0001). This finding was consistent with previous studies (14,15), demonstrating that RGM medium provided performance equivalent to that of the MGIT system or even better for the recovery of MABSC and other rapidly growing mycobacteria. Notably, the time to recovery of MABSC on RGM medium was comparable to the average time to positivity of MABSC on the MGIT system (ϳ4 days).…”

Section: Discussionsupporting

confidence: 93%

“…However, the incubation at 35°C (with 8% CO 2 ) supported growth of certain slowly growing mycobacteria, including MAC, M. lentiflavum, and M. simiae. In this study, we extended the incubation time of RGM plates to 28 days as described in a previous study (15) with the goal of increasing recovery of slowly growing mycobacteria. Our results showed increased recovery of NTM from RGM medium, including both rapidly and slowly growing mycobacteria upon extended incubation from 10 to 28 days.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, a new selective medium (RGM medium), which is composed of Middlebrook 7H9-based agar supplemented with oleic acid-albumin-dextrose-catalase (OADC) and four antimicrobial agents (12,13), has been shown to have high performance for the recovery of rapidly growing mycobacteria from respiratory specimens from CF patients (12)(13)(14)(15). RGM medium was superior to Burkholderia cepacia complex selective medium and showed performance equivalent to or higher than that of the MGIT system.…”

mentioning

confidence: 99%

“…RGM medium was superior to Burkholderia cepacia complex selective medium and showed performance equivalent to or higher than that of the MGIT system. An added advantage was the ability of RGM medium to inhibit growth of other nonmycobacterial organisms in CF patients' respiratory specimens without requirement for a decontamination step (12)(13)(14)(15). The use of an extended incubation period of 28 days allows RGM medium to be used for the isolation of all NTM, rather than simply rapidly growing species, but there are only limited data on the recovery of slowly growing species (15).…”

mentioning

confidence: 99%

“…An added advantage was the ability of RGM medium to inhibit growth of other nonmycobacterial organisms in CF patients' respiratory specimens without requirement for a decontamination step (12)(13)(14)(15). The use of an extended incubation period of 28 days allows RGM medium to be used for the isolation of all NTM, rather than simply rapidly growing species, but there are only limited data on the recovery of slowly growing species (15). Furthermore, while several studies have evaluated the performance of RGM medium in the setting of CF, RGM medium has yet to be studied in the non-CF patient population with underlying lung conditions.…”

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confidence: 99%

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Performance of RGM Medium for Isolation of Nontuberculous Mycobacteria from Respiratory Specimens from Non-Cystic Fibrosis Patients

et al. 2019

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A new selective medium for rapidly growing mycobacteria (RGM medium) was evaluated on respiratory specimens from non-cystic fibrosis patients and compared to the mycobacterial growth indicator tube (MGIT) system and Middlebrook 7H11 agar for the isolation of all nontuberculous mycobacteria (NTM). A total of 203 mucolyzed respiratory specimens collected from 163 patients were inoculated on RGM medium and incubated at both 30°C (RGM30) and 35°C (RGM35) over a 28day period. N-Acetyl-L-cysteine-sodium hydroxide (NALC-NaOH)-decontaminated specimens were inoculated into MGIT and Middlebrook 7H11 agar and incubated at 35°C for 42 days. NTM were identified by matrix-assisted laser desorption ionizationtime of flight mass spectrometry (MALDI-TOF MS) or gene sequencing. A total of 133 NTM isolates were recovered overall from 101 (49.8%) specimens collected from 85 (52.1%) patients by a combination of all culture methods. The sensitivity of RGM30 for the recovery of NTM was significantly higher than that of either the MGIT system (76.7% versus 59.4%; P ϭ 0.01) or Middlebrook 7H11 agar (76.7% versus 47.4%; P ϭ 0.0001) alone, but it was not significantly different from that of an acidfast bacillus culture (AFC) which includes both MGIT and Middlebrook 7H11 agar (76.7% versus 63.9%; P ϭ 0.0647). RGM35 had significantly lower sensitivity than the MGIT system (49.6% versus 59.4%; P ϭ 0.0367) and AFC (49.6% versus 63.9%; P ϭ 0.0023). RGM medium was highly effective at inhibiting the growth of nonmycobacterial organisms in the respiratory specimens, with breakthrough contamination rates of 5.4% and 4.4% for RGM30 and RGM35, respectively.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Performance of RGM Medium for Isolation of Nontuberculous Mycobacteria from Respiratory Specimens from Non-Cystic Fibrosis Patients

et al. 2019

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Solid Media Used for Isolation

Wengenack

2023

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Both liquid and solid media are recommended for optimal recovery of mycobacteria in culture. Pure cultures of mycobacteria, particularly Mycobacterium tuberculosis , are still required, despite the availability of molecular technology, to obtain phenotypic antimicrobial susceptibility test results and for strain typing. The advantage of solid medium is that it enables the detection of mixed cultures and contaminants. Egg‐based or agar‐based media may be used. The main advantage of an egg‐based medium is that it best supports the growth of M. tuberculosis and permits niacin testing, if needed. The advantages of agar‐based media include less contamination and earlier and easier visibility of colonial morphology. Colonial morphology can aid in the identification of mycobacteria. Use of both nonselective and selective media is needed for optimal mycobacterial isolation, the latter containing one or more antimicrobial agents to prevent overgrowth by contaminating bacteria or fungi.

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