Influence of carbon concentration, shear stress and temperature on survival of Legionella pneumophila in drinking water biofilms
Bibliographic record
Abstract
Biofilms can form under stressful conditions and offer protection against mechanical and chemical disruptions, hence providing a refuge for pathogens. One of the possible waterborne colonisers in drinking water distribution system biofilms is Legionella pneumophila, which is still responsible for many outbreaks of Legionellosis worldwide. The aim of this work was to study the influence of important operational parameters, including shear stress, carbon concentration and temperature, on persistence of this pathogen in drinking water biofilms. The biofilm studies were carried out using a two-stage chemostat system. The outflow culture of the first vessel fed three secondary chemostats in parallel and under different conditions of shear stress and carbon concentration. After 10 days the chemostats attained steady conditions and PVC coupons were then immersed to allow biofilm formation. The coupons were removed at different times (up to 32 days) and scraped with sterile glass beads. Planktonic and sessile cells were quantified by standard cultivation techniques (R2A and BCYE agar) and SYTO9 staining. In addition, a specific 16S rRNA peptide nucleic acid probe (PNA) was used to quantify the total numbers of L. pneumophila in the biofilm. The conditions described above were tested at two different temperatures, 15 and 20ºC. Concerning sessile cells, the number of total fluorescently labelled bacteria and L. pneumophila were similar for the three conditions studied at both temperatures. However more cultivable cells were seen when chemostats were operated with high shear and high carbon concentrations, particularly the latter. This might indicate the existence of Viable But Non Cultivable L. pneumophila that can recover cultivability under certain conditions. For example, the total of fluorescently labelled L. pneumophila was higher at 15ºC. In conclusion, temperature was the most important factor influencing the formation of biofilm and persistence of L. pneumophila. Carbon concentration also had a considerable influence on the number of total cells in water and biofilms. Shear stress played only a minor role in the numbers of planktonic and sessile cells present. ASM Biofilm Conference, Quebec City, 25-29th March 2007. ISBN: 1-55581-428-X
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".