The use of BCYE medium for the detection of Legionella in environmental water samples: an appropriate update to ISO 11731:2017 standard?

Diagn Microbiol Infect Dis. 2022 Feb;102(2):115593. doi: 10.1016/j.diagmicrobio.2021.115593. Epub 2021 Nov 7.


We evaluated the diagnostic performances of 2 media (BCYE, MWY) on 951 Legionella-positive hospital water samples. MWY allowed detecting Legionella in 89.2% of samples, but in 10.8% (103/951) Legionella was found on BCYE plates only. In samples where Legionella was isolated with other microorganisms (663/951), MWY was essential to detect the majority of positive samples (349/663, 52.6%), as fewer plates resulted unreadable; however, in those containing Legionella only, a higher frequency of positive samples was recorded with BCYE (94.8%, 273/288) compared to MWY (85.1%, 245/288). Considering the 484 concordant positive samples, overall Legionella counts were significantly higher on BCYE (P = 0.0029), with 47% of samples showing higher counts on BCYE compared to MWY plates. Furthermore, discordant samples (positive on only one medium) showed different relative proportions between Legionella pneumophila and non-pneumophila, the latter being found more frequently on BCYE only (P = 0.0296).Our findings confirm the appropriateness of the ISO 11731:2017 update.

Keywords: Culture; Environmental samples; Legionella; Media.

Publication types

  • Comparative Study

MeSH terms

  • Bacteriological Techniques / standards*
  • Culture Media / standards*
  • Environmental Monitoring / standards*
  • Guidelines as Topic*
  • Humans
  • Legionella / isolation & purification*
  • Water Microbiology / standards*


  • Culture Media