Multiplication of legionella pneumophila sequence types 1, 47, and 62 in buffered yeast extract broth and biofilms exposed to flowing tap water at temperatures of 38°C to 42°C

“Legionella pneumophila proliferates in freshwater environments at temperatures ranging from 25 to 45°C. To investigate the preference of different sequence types (ST) for a specific temperature range, growth of L. pneumophila serogroup 1 ST1 (environmental strains), ST47 and ST62 (disease-associated strains) was measured in buffered yeast extract broth (BYEB) and biofilms grown on plasticized polyvinyl chloride in flowing heated drinking water originating from a groundwater supply. The optimum growth temperature in BYEB was approx. 37°C (ST1), 39°C (ST47) and 41°C (ST62), respectively, with maximum growth temperatures of 42°C (ST1) and 43 °C (ST47 and ST62). In the biofilm at 38°C the ST47 and ST62 strains multiplied equally well as compared to the environmental ST1 strain and an indigenous L. pneumophila non-SG1, all attaining a concentration of approx. 107 colony-forming units cm-2. Raising the temperature to 41°C did not impact these levels within four weeks, but the colony counts of all strains tested declined (at 0.14 to 0.41 day-1) when the temperature was raised to 42°C. At this temperature, the concentration of Vermamoeba vermiformis in the biofilm, determined with qPCR, was about two log units lower as compared to the concentration at 38°C. In columns operated at a constant temperature, ranging from 38 to 41°C, none of the tested strains multiplied in the biofilm at 41°C in which also V. vermiformis was not detected. These observations suggest that strains of ST47 and ST62 did not multiply in the biofilm at a temperature ≥ 41°C because of the absence of a thermotolerant host.”

(Citaat: van der Kooij, D., Brouwer-Hanzens, A.J., Veenendaal, H.R., Wullings, B.A. – Multiplication of legionella pneumophila sequence types 1, 47, and 62 in buffered yeast extract broth and biofilms exposed to flowing tap water at temperatures of 38°C to 42°C – Applied and Environmental Microbiology 82(2016)22, p.6691-6700)

(Erratum: van der Kooij, D. et al. – Multiplication of Legionella pneumophila Sequence Types 1, 47, and 62 in Buffered Yeast Extract Broth and Biofilms Exposed to Flowing Tap Water at Temperatures of 38°C to 42°C – Applied and Environmental microbiology 83(2017)1, art. no. e03036-16 – doi: 10.1128/AEM.03036-16)