Temperature-dependent growth modeling of environmental and clinical Legionella pneumophila MLVA-genotypes.

Abstract

Legionella pneumophila cause waterborne infections resulting in severe pneumonia. High resolution genotyping of L. pneumophila isolates can be achieved by Multiple-Locus Variable number of tandem repeat Analysis (MLVA). Recently, we found that different MLVA genotypes of L. pneumophila, dominated different sites in a small drinking-water network, with a genotype-related temperature and abundance regime. The current study focuses on understanding the temperature-dependent growth kinetics of the genotypes that dominated the water network. Our aim was to model mathematically the influence of temperature on the growth kinetics of different environmental and clinical L. pneumophila genotypes and compare it with their ecological niches. Environmental strains showed a distinct temperature preference with significant differences among the growth kinetics of the three studied genotypes (Gt4, Gt6 and Gt15). Gt4 strains exhibited superior growth at lower temperatures (25-30 °C) while Gt15 strains appeared to be best adapted to relatively higher temperatures (42-45 °C). The temperature-dependent growth traits of the environmental genotypes were consistent with their distribution and temperature preferences in the water network. Clinical isolates exhibited significantly higher growth rates and reached higher maximal cell densities at 37°C and 42°C than the environmental strains. Further research on the growth preferences of L. pneumophila clinical and environmental genotypes will result in better understanding of their ecological niches in drinking water systems as well as in the human body.