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

Rotcheewaphan, Suwatchareeporn, Odusanya, Oluwadamilola, Henderson, Christina, Stephenson, Dominic, Olivier, Kenneth, Perry, John and Zelazny, Adrian (2019) Performance of RGM Medium for the Isolation of Nontuberculous Mycobacteria from Respiratory Specimens from Non-Cystic Fibrosis Patients. Journal of Clinical Microbiology, 57 (2). e01519-18. ISSN 0095-1137

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Abstract

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 28-day period. N-acetyl-L-cysteine–sodium hydroxide (NALC-NaOH) decontaminated specimens were inoculated into a MGIT and Middlebrook 7H11 agar and incubated at 35°C for 42 days. NTM were identified by matrix assisted laser desorption ionization-time 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 either MGIT system (76.7% versus 59.4%; p = 0.01) or Middlebrook 7H11 agar (76.7% versus 47.4%; p = 0.0001) alone but it was not significantly different from acid-fast bacilli culture (AFC) which includes both MGIT and Middlebrook 7H11 agar (76.7% versus 63.9%; p = 0.0647). RGM35 had significantly lower sensitivity compared to the MGIT system (49.6% versus 59.4%; p = 0.0367) and AFC (49.6% versus 63.9%; p = 0.0023). RGM medium was highly effective at inhibiting the growth of non-mycobacterial organisms in the respiratory specimens with breakthrough contamination rates of 5.4% and 4.4% for RGM30 and RGM35, respectively.

Item Type:	Article
Subjects:	C500 Microbiology
Department:	Faculties > Health and Life Sciences > Applied Sciences
Depositing User:	Becky Skoyles
Date Deposited:	15 Jan 2019 16:10
Last Modified:	11 Oct 2019 14:02
URI:	http://nrl.northumbria.ac.uk/id/eprint/37594

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