Profiling bacterial survival through a water treatment process and subsequent distribution system

Abstract

Aims: To profile fractions of active bacteria and of bacteria culturable with routine heterotrophic plate count (HPC) methods through a typical water treatment process and subsequent distribution system. In doing so, investigate how water treatment affects both bacterial abundance and diversity, and reveal the identities of active bacteria not detected by traditional HPC culture. Methods and Results: Profiling active fractions was performed by flow cytometric cell sorting of either membrane-intact (BacLight TM kit) or enzymatically active (carboxyfluorescein diacetate, CFDA) bacteria, followed by eubacterial 16S rDNA-directed PCR and denaturing gradient gel electrophoresis (DGGE). Water treatment significantly reduced active bacterial numbers detected by the BacLight TM kit and CFDA assay by 2AE89 and 2AE81 log respectively. Bacterial diversity was also reduced from >20 DGGE bands in the active fractions of reservoir water to only two bands in the active fractions of finished water. These two bands represented Stenotrophomonas maltophila, initially culturable by HPC, and a Burkholderia-related species. Both species maintained measurable traits of physiological activity in distribution system bulk water but were undetected by HPC. Conclusions: Flow cytometric cell sorting with PCR-DGGE, to assess water treatment efficacy, identified active bacteria from a variety of major phylogenetic groups undetected by routine HPC. Following treatment S. maltophila and a Burkholderia-related species retained activity and entered distribution undetected by HPC. Significance and Impact of the Study: Methods used here demonstrate how water treatment operators can better monitor water treatment plant efficacy and assess distribution system instability by the detection and identification of active bacteria recalcitrant to routine HPC culture.

Antibiotic resistance in urban aquatic environments: can it be controlled?

“…Therefore, it is expected that in drinking water, both the diversity of bacterial species and the possible occurrence of antibiotic resistance will have different characteristics of what can be found in wastewater. Water disinfection is known to cause a dramatic bottleneck on bacterial diversity (Hoefel et al 2005;Eichler et al 2006;Vaz-Moreira et al 2013) and bacteria ubiquitous in aquatic environments, such as members of the genus Aeromonas, may be reduced to levels below the limit of detection by culture-dependent methods (Figueira et al 2011). However, other groups that comprise bacteria with recognized ubiquity and genome plasticity, demonstrated by the acquired capacity to degrade xenobiotics or to resist to some antibiotics, such as members of the genera Pseudomonas, Acinetobacter, or family Sphingomonadaceae, are commonly found in tap water (Vaz-Moreira et al 2014).…”

Culturability and Survival of Marine, Freshwater and Clinical Pseudomonas aeruginosa

“…A 1-mL aliquot of water with appropriate dilutions was mixed with 3 μL of a mixture of 3.34 nM SYTO 9 green and 20 mM propidium iodide (Molecular Probes, Eugene, OR, USA) dissolved in dimethyl sulfoxide (DMSO) prepared according to the manufacturer's instructions, and incubated for 15 min in the dark at room temperature (18). The mixture was filtered through 0.2-μm Nuclepore Track-Etch Membrane polycarbonate black filters (Whatman, Middlesex, UK).…”

Stenotrophomonas maltophilia infection in hematopoietic SCT recipients: high mortality due to pulmonary hemorrhage

“…Stenotrophomonas maltophilia is a non-fermentative, Gram-negative bacillus that is ubiquitous in the natural and hospital environment, [1][2][3][4] and exhibits intrinsic resistance to many antibiotics including b-lactams, carbapenems and aminoglycosides. 5,6 Although S. maltophilia is not usually highly virulent, it is a significant pathogen in immune-compromised patients, and the incidence of S. maltophilia infection is increasing.…”