Prevalence and diversity of Chlamydiales and other amoeba-resisting bacteria in domestic drinking water systems

Abstract

A growing number of human infections incriminate environmental bacteria that have evolved virulent mechanisms to resist amoebae and use them as a replicative niche. These bacteria are designated amoeba-resisting bacteria (ARB). Despite the isolation of these ARB in various human clinical samples, the possible source of infection remains undetermined in most cases. However, it is known that the ARB Legionella pneumophila, for instance, causes a respiratory infection in susceptible hosts after inhalation of contaminated water aerosols from various sources. The Chlamydiales order contains many ARB, such as Parachlamydia acanthamoebae or Simkania negevensis, previously implicated in human respiratory infections with no identified contamination sources. We thus investigated whether domestic water systems are a potential source of transmission of these Chlamydiales to humans by using amoebal culture and molecular methods. Other important ARB such as mycobacteria and Legionella were also investigated, as were their possible amoebal hosts. This work reports for the first time a very high prevalence and diversity of Chlamydiales in drinking water, being detected in 35 (72.9%) of 48 investigated domestic water systems, with members of the Parachlamydiaceae family being dominantly detected. Furthermore, various Legionella and mycobacteria species were also recovered, some species of which are known to be causal agents of human infections.

Chlamydiae in febrile children with respiratory tract symptoms and age-matched controls, Ghana

“…Additionally, samples with a cycle threshold of ≤35 in the 16S rRNA pan- Chlamydiales real-time PCR were analysed by sequencing the 16S rRNA amplicon. Practically, the best BLAST hit ( http://blast.ncbi.nlm.nih.gov/Blast.cgi ) of the obtained sequence with a 16S rRNA sequence from a bacterial strain that has been previously assigned taxonomically to a given species-level lineage was considered the first known organism in the National Center for Biotechnology Information (NCBI) database, and the percentage of similarity with that hit was used to perform the taxonomic assignment, as previously described [3] , [16] , [17] , [18] . Cutoffs of ≥80% [19] , ≥92.5% [20] , ≥95% [21] and ≥97% [22] sequence identity of the amplicon were used to assign the order, family, genus and species level, respectively.…”

Impact of drinking water treatment and distribution on the microbiome continuum: an ecological disturbance's perspective

“…Free-living amoebae might colonize biofilms on pipe surfaces or the surfaces of sediment particles in the distribution system. Under unfavourable conditions, they could exhibit a resistant form as cysts (Lienard et al, 2017). Nematodes could dwell in all possible niches in the drinking water system, but are particularly found in sand filters (Mott and Harrison, 1983;Locas et al, 2007).…”

What is the true clinical relevance of Simkania negevensis and other emerging Chlamydiales members?

“…This low prevalence correlates with several other European studies describing a prevalence of C. pneumoniae infection of <2% [21] , [35] , [36] . The molecular detection rate of this recognized pathogen in respiratory samples does not significantly differ from detection rate of Parachlamydiaceae [37] , [38] , [39] . Nevertheless, C. pneumoniae remains a well-established agent of respiratory diseases, sometimes causing outbreaks [40] , [41] .…”