Water Sampling Module for Collecting and Concentrating Legionella pneumophila from Low-to-Medium Contaminated Environment

Abstract

The detection of water contamination with Legionella pneumophila is of critical importance to manufacturers of water processing equipment and public health entities dealing with water networks and distribution systems. Detection methods based on polymerase chain reaction or biosensor technologies require preconcentration steps to achieve attractive sensitivity levels. Preconcentration must also be included in protocols of automated collection of water samples by systems designed for quasi-continuous monitoring of remotely located water reservoirs for the presence of L. pneumophila. We designed and characterized a water sampling module for filtration and backwashing intended for analysis of low-to-medium contaminated water, typically with L. pneumophila bacteria not exceeding 50 colony-forming units per milliliter. The concentration factors of 10× and 21× were achieved with 0.22 and 0.45 µm filters, respectively, for samples of bacteria prepared in clean saline solutions. However, a 5× concentration factor was achieved with 0.45 µm filters for a heavily contaminated or turbid water typical of some industrial water samples.

Selective Detection of Legionella pneumophila Serogroup 1 and 5 with a Digital Photocorrosion Biosensor Using Antimicrobial Peptide-Antibody Sandwich Strategy

“…The DIP-biosensor technology has been investigated for detection of different bacteria, including E. coli , Bacillus sp., and L. pneumophila [ 23 , 39 , 44 ], with typical LOD at 10 3 CFU/mL. Therefore, detection of L. pneumophila SG1 at 100 CFU/mL represents a significant step towards development of a field-operating DIP biosensor that is expected to deliver enhanced biosensing based on the introduction of filtration and preconcentration techniques of water samples originating from different sources [ 69 ].…”

Semi-automated water sampling module for repeated sampling and concentration of Bacillus cereus group spores

“…1 . The unit employs a peristaltic pump and a set of pinch valves that allow processing of bacterial suspensions while eliminating contact of metallic or plastic parts of the valves employed for building a conventional WSM 12 . That minimized chemical degradation of the system and eliminated adventitious contamination of processed samples.…”

“…Examples of the filtration methods and type of filters investigated for this purpose are provided in Table 1 . The reported concentration factors (CF) of microorganisms achieved with filtration are in the 5–586 range 9 – 12 . It is important to indicate that CF depend on the filtered material and the backwash volumes.…”

“… Filter material Filtration mode Micro-organisms CF CF Max Method of evaluation Automatization References Ceramic Tangential E. coli Up to 500 500 Volumetric concentration Yes Zhang et al 9 Polysulfone Ultrafiltration Polysulfone dialysis filter MWCO 30 KDA S. enterica B. atrophaeus var. globigii endospores MS2 bacteriophage E1 bacteriophage C. parvum 426–486 326–353 560–566 246–360 526–586 666 PCR No Polaczyk et al 10 Polycarbonate Membrane filtration L. pneumophila 31–82 100 Fluorescence microscopy No Yamaguchi et al 11 Polyvinylidene fluoride Membrane filtration L. pneumophila 5–20 33 Culture Yes Moumanis et al 12 …”

“…Our preliminary results to pre-concentrate B. cereus spores with a polyvinylidene difluoride (PVDF) filter-based system were unsatisfactory. This was due to the excessive adhesion of spores to the filter material and surfaces of the components employed for constructing the filtration system, originally designed for filtration of L. pneumophila 12 . That observation is consistent with the reports of strong adhesion of bacterial spores to hydrophobic surfaces 14 , 15 .…”