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

• Published in: Diagnostic microbiology and infectious disease 2022-02, Vol.102 (2), p.115593-115593, Article 115593
• Main Authors: Ditommaso, Savina, Giacomuzzi, Monica, Memoli, Gabriele, Garlasco, Jacopo, Zotti, Carla M.
• Format: Article
• Language: English
• Subjects: Bacteriological Techniques - standards; Culture; Culture Media - standards; Environmental Monitoring - standards; Environmental samples; Guidelines as Topic; Humans; Legionella; Legionella - isolation & purification; Media; Water Microbiology - standards
• ISSN: 0732-8893; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2021.115593

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. [Display omitted]