title: A novel culture medium for isolation of rapidly-growing mycobacteria from the sputum of patients with cystic fibrosis.
abstract: BACKGROUND
  Isolation of mycobacteria from the sputum of patients with cystic fibrosis (CF) is challenging due to the overgrowth of cultures by other bacteria and fungi. In this setting, Burkholderia cepacia selective agar (BCSA) has been recommended as a convenient and effective culture medium for the isolation of rapidly-growing, non-tuberculous mycobacteria (NTM). A novel selective culture medium (RGM medium) was evaluated for the isolation of rapidly-growing NTM from the sputum of children and adults with CF.
  
  
  METHODS
  A total of 118 isolates of rapidly-growing mycobacteria and 98 other bacteria and fungi were inoculated onto RGM medium. These were assessed for growth at 30°C over a seven day period. A total of 502 consecutive sputum samples were collected from 210 patients with CF. Each sample was homogenized and cultured onto RGM medium and also onto BCSA. Cultures were incubated for 10days at 30°C.
  
  
  RESULTS
  Of 118 isolates of mycobacteria all but one grew well on RGM medium, whereas 94% of other bacteria and fungi were inhibited. A total of 55 sputum samples (from 33 distinct patients) yielded NTM using a combination of both RGM and BCSA (prevalence: 15.7%). NTM were recovered from 54 sputum samples using RGM medium compared with only 17 samples using BCSA (sensitivity 98% vs. 31%; P≤0.0001). A total of 419 isolates of non-mycobacteria were recovered from sputum samples on BCSA compared with 46 on RGM medium.
  
  
  CONCLUSIONS
  RGM medium offers a simple and effective culture method for the isolation of rapidly-growing mycobacteria from sputum samples from patients with CF without decontamination of samples. RGM medium allows for the systematic screening of all sputum samples routinely referred for culture from patients with CF.
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK; Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Clair L
authors.initials: CL
authors.lastname: Preece
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
authors.forename: Audrey
authors.initials: A
authors.lastname: Perry
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
authors.forename: Bethany
authors.initials: B
authors.lastname: Gray
authors.affiliation: Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, Public Health England, London, UK.
authors.forename: Dervla T
authors.initials: DT
authors.lastname: Kenna
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Jones
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Cummings
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
authors.forename: Ali
authors.initials: A
authors.lastname: Robb
authors.affiliation: Paediatric Respiratory Unit, Great North Children's Hospital, Newcastle upon Tyne NE1 4LP, UK.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Thomas
authors.affiliation: Paediatric Respiratory Unit, Great North Children's Hospital, Newcastle upon Tyne NE1 4LP, UK.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Brodlie
authors.affiliation: Paediatric Respiratory Unit, Great North Children's Hospital, Newcastle upon Tyne NE1 4LP, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: O'Brien
authors.affiliation: Adult Cystic Fibrosis Centre, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Bourke
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK; Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne NE1 8ST, UK. Electronic address: john.perry@nuth.nhs.uk.
authors.forename: John D
authors.initials: JD
authors.lastname: Perry
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001431:Bacteriological Techniques / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003470:Culture Media; D003550:Cystic Fibrosis / Q000382:microbiology*; D006801:Humans; D007223:Infant; D008875:Middle Aged; D009161:Mycobacterium / Q000254:growth & development* / Q000302:isolation & purification; D013183:Sputum / Q000382:microbiology*; D055815:Young Adult
chemical_list: D003470:Culture Media
keywords: Culture media; Mycobacterium abscessus; Non-tuberculous mycobacteria