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

Abstract

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 (SG1) 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 temperatures in BYEB were approximately 37°C (ST1), 39°C (ST47), and 41°C (ST62), 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 compared to growth of the environmental ST1 strain and an indigenous L. pneumophila non-SG1 strain, all attaining a concentration of approximately 10 7 CFU/cm ؊2 . Raising the temperature to 41°C did not impact these levels within 4 weeks, but the colony counts of all strains tested declined (at a specific decline rate of 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 quantitative PCR (qPCR), was about 2 log units lower than 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 of >41°C because of the absence of a thermotolerant host. IMPORTANCEGrowth of Legionella pneumophila in tap water installations is a serious public health concern. The organism includes more than 2,100 varieties (sequence types). More than 50% of the reported cases of Legionnaires' disease are caused by a few sequence types which are very rarely detected in the environment. Strains of selected virulent sequence types proliferated in biofilms on surfaces exposed to warm (38°C) tap water to the same level as environmental varieties and multiplied well as pure culture in a nutrient-rich medium at temperatures of 42 and 43°C. However, these organisms did not grow in the biofilms at temperatures of >41°C. Typical host amoebae also did not multiply at these temperatures. Apparently, proliferation of thermotolerant host amoebae is needed to enable multiplication of the virulent L. pneumophila strains in the environment at elevated temperatures. The detection of these amoebae in water installations therefore is a scientific challenge with practical implications. T he genus Legionella currently includes ca. 63 (sub)species (https://www.dsmz.de), at least 20 of which have been implicated in legionellosis (1). Legionella pneumophila is responsible for more than 90% of the reported cases of Legionnaires' disease (LD) in Europe (2), the United States (3), Canada (4), and Japan (5). This species includes 15 polyclonal serogroups (SGs). Most of the cli...

Primary Colonizing Betaproteobacteriales Play a Key Role in the Growth of Legionella pneumophila in Biofilms on Surfaces Exposed to Drinking Water Treated by Slow Sand Filtration

“…Host amoebae. Vermamoeba vermiformis, previously named Hartmannella vermiformis (34), is ubiquitous in drinking water (31) and has been identified as an amoebal host for L. pneumophila in many studies, mostly under experimental conditions, (e.g., see references [35][36][37][38][39]. In the biofilms exposed to warm treated groundwater, the colony counts of L. pneumophila were strongly related to the concentrations of V. vermiformis (9).…”

“…A constant LpC/BfC ratio therefore requires a steady-state situation in biofilm concentration and composition. A steadystate situation is represented by the growth of L. pneumophila on plasticized PVC at 38°C with a constant water flow and an average BfC of 27 (Ϯ5.7) ϫ 10 3 pg ATP cm Ϫ2 (39). For a period of 100 days, a value of Ϫ1.99 Ϯ 0.16 was derived for log b (ϭ log LpC Ϫ 2 log BfC) ( Fig.…”

Electrically heatable carbon nanotube point-of-use filters for effective separation and in-situ inactivation of Legionella pneumophila

“…Legionella can colonize water distribution lines and building plumbing, contaminating water supplies after it has been centrally treated. Legionella thrive in the temperature range of 25 to 54 °C, a range that includes hot water systems, shower heads and even cold-water systems in warm climates [5][6][7][8][9][10][11].…”

Água em elevada temperatura: é viável a sua aplicabilidade no controle do biofilme de equipo odontológico?

“…Todavia, apesar das vantagens inerentes dessas substâncias e/ou produtos para a manutenção do ambiente biologicamente seguro na Odontologia, há desvantagens relacionadas à toxicidade e desequilíbrio do ecossistema ambiental a curto ou longo prazo, que podem ser contornadas pela substituição por agentes físicos, como as ondas acústicas (PANTANELLA et al, 2019) e a água em elevada temperatura (AL-HIYASAT et al, 2007;COLEMAN et al, 2008;LEONI et al, 2015;DITOMMASO et al, 2016a;VAN DER KOOIJ et al, 2016).…”

“…Em encanamento de hotéis, a água em elevada temperatura controlou o biofilme, mas essa solução simples pode aumentar os custos e inviabilizar a sua implementação, porque há a necessidade do uso de caldeiras e misturadores, com água quente e fria para se atingir a temperatura adequada que não cause injúrias térmicas nos clientes (BORELLA et al, 2005). (BARBEAU, 2000;BORELLA et al, 2005;O'DONNELL et al, 2011;PASQUARELLA et al, 2012;LEONI et al, 2015;DITOMMASO et al, 2016a;DITOMMASO et al, 2016b;VAN DER KOOIJ et al, 2016), que pode ser monitorada por meio de um bom indicador, a quantificação de bactérias heterotróficas aeróbias totais (DITOMMASO et al, 2016a).…”