Interaction of Legionella pneumophila and Helicobacter pylori with bacterial species isolated from drinking water biofilms.

Maria S Gião,Charles W Keevil,Nuno F Azevedo,Sandra A Wilks,Maria J Vieira

doi:10.1186/1471-2180-11-57

Abstract

BackgroundIt is well established that Legionella pneumophila is a waterborne pathogen; by contrast, the mode of Helicobacter pylori transmission remains unknown but water seems to play an important role. This work aims to study the influence of five microorganisms isolated from drinking water biofilms on the survival and integration of both of these pathogens into biofilms.ResultsFirstly, both pathogens were studied for auto- and co-aggregation with the species isolated from drinking water; subsequently the formation of mono and dual-species biofilms by L. pneumophila or H. pylori with the same microorganisms was investigated. Neither auto- nor co-aggregation was observed between the microorganisms tested. For biofilm studies, sessile cells were quantified in terms of total cells by SYTO 9 staining, viable L. pneumophila or H. pylori cells were quantified using 16 S rRNA-specific peptide nucleic acid (PNA) probes and cultivable cells by standard culture techniques. Acidovorax sp. and Sphingomonas sp. appeared to have an antagonistic effect on L. pneumophila cultivability but not on the viability (as assessed by rRNA content using the PNA probe), possibly leading to the formation of viable but noncultivable (VBNC) cells, whereas Mycobacterium chelonae increased the cultivability of this pathogen. The results obtained for H. pylori showed that M. chelonae and Sphingomonas sp. help this pathogen to maintain cultivability for at least 24 hours.ConclusionsIt appears that M. chelonae may have an important role in the survival of both pathogens in drinking water. This work also suggests that the presence of some microorganisms can decrease the cultivability of L. pneumophila but not the viability which indicates that the presence of autochthonous microorganisms can lead to misleading results when the safety of water is assessed by cultivable methods alone.

Highlights

It is well established that Legionella pneumophila is a waterborne pathogen; by contrast, the mode of Helicobacter pylori transmission remains unknown but water seems to play an important role
In comparison to total cells, 49% were cultivable on Buffered Charcoal Yeast Extract (BCYE) agar and 50% were detected by peptide nucleic acid (PNA)-fluorescence in situ hybridization (FISH)
No co-aggregation of L. pneumophila or H. pylori was observed with any of the bacteria isolated from drinking water biofilms, demonstrating that while all of the bacteria used in this study have the ability to form biofilms they are attaching to the Unplasticized polyvinylchloride (uPVC) surfaces without aggregating in the planktonic phase with the other microorganisms [36]

Summary

Introduction

It is well established that Legionella pneumophila is a waterborne pathogen; by contrast, the mode of Helicobacter pylori transmission remains unknown but water seems to play an important role. Bacteria can adhere to surfaces forming a complex structure called a biofilm. Legionella pneumophila is a waterborne pathogen that can cause Legionnaires’ disease or Pontiac fever [13,14]. This pathogen is found naturally in fresh water reservoirs and can contaminate drinking water when disinfection is inefficient, being transmitted to man when contaminated aerosols are inhaled [12,15,16,17].

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