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Relationship between Organic Carbon and Opportunistic Pathogens in Simulated Glass Water Heaters.

Williams K, Pruden A, Falkinham JO, Edwards M, Williams K, Pruden A, Iii JO, Edwards M - Pathogens (2015)

Bottom Line: R2 > 0.89).R2 = 0.82 to 0.97, for 2 out of 4 time points) and over a limited TOC range (0-1000 µg/L), no other correlations were identified between other OPPPs and added TOC.These results suggest that reducing organic carbon in distributed water is not adequate as a sole strategy for controlling OPPPs, although it may have promise in conjunction with other approaches.

View Article: PubMed Central - PubMed

Affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. kwilli@vt.edu.

ABSTRACT
Controlling organic carbon levels in municipal water has been hypothesized to limit downstream growth of bacteria and opportunistic pathogens in premise plumbing (OPPPs). Here, the relationships between influent organic carbon (0-15,000 µg ozonated fulvic acid /L) and the number of total bacteria [16S rRNA genes and heterotrophic plate counts (HPCs)] and a wide range of OPPPs (gene copy numbers of Acanthamoeba polyphaga, Vermamoeba vermiformis, Legionella pneumophila, and Mycobacterium avium) were examined in the bulk water of 120-mL simulated glass water heaters (SGWHs). The SGWHs were operated at 32-37 °C, which is representative of conditions encountered at the bottom of electric water heaters, with water changes of 80% three times per week to simulate low use. This design presented advantages of controlled and replicated (triplicate) conditions and avoided other potential limitations to OPPP growth in order to isolate the variable of organic carbon. Over seventeen months, strong correlations were observed between total organic carbon (TOC) and both 16S rRNA gene copy numbers and HPC counts (avg. R2 > 0.89). Although M. avium gene copies were occasionally correlated with TOC (avg. R2 = 0.82 to 0.97, for 2 out of 4 time points) and over a limited TOC range (0-1000 µg/L), no other correlations were identified between other OPPPs and added TOC. These results suggest that reducing organic carbon in distributed water is not adequate as a sole strategy for controlling OPPPs, although it may have promise in conjunction with other approaches.

No MeSH data available.


Related in: MedlinePlus

Effect of stagnation on HPC (CFU/mL) vs. TOC (Stagnation: 1X per week 80% water change—Experiment A3; Regular Flow Regime: 3X per week 80% water change—Experiment A2).
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pathogens-04-00355-f001: Effect of stagnation on HPC (CFU/mL) vs. TOC (Stagnation: 1X per week 80% water change—Experiment A3; Regular Flow Regime: 3X per week 80% water change—Experiment A2).

Mentions: Strong correlations were consistently observed between TOC (0–15,000 µg/L) and both HPC counts (CFU) and total bacteria (as 16S rRNA gene copies) during intervals involving regular 3X per week 80% water changes in Experiment A1 (Average R2 values of 0.89 and 0.97 for 16S rRNA genes and HPCs, respectively) (Table 1). Experiment A2 was distinct from A1 in terms of accumulated biomass, a slightly lower temperature, and a longer stagnation during inoculation (25 vs. 13 days for A1). When 3X per week 80% water changes were resumed to initiate experiment A2, the correlations of HPCs and 16S rRNA to TOC correspondingly weakened (R2 = 0.65 and 0.63, respectively) (Table 1). Finally, in Experiment A3, when stagnation was extended by decreasing the 80% water change frequency to 1X per week, no significant correlations with added TOC were identified (Figure 1; Table 1).


Relationship between Organic Carbon and Opportunistic Pathogens in Simulated Glass Water Heaters.

Williams K, Pruden A, Falkinham JO, Edwards M, Williams K, Pruden A, Iii JO, Edwards M - Pathogens (2015)

Effect of stagnation on HPC (CFU/mL) vs. TOC (Stagnation: 1X per week 80% water change—Experiment A3; Regular Flow Regime: 3X per week 80% water change—Experiment A2).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493478&req=5

pathogens-04-00355-f001: Effect of stagnation on HPC (CFU/mL) vs. TOC (Stagnation: 1X per week 80% water change—Experiment A3; Regular Flow Regime: 3X per week 80% water change—Experiment A2).
Mentions: Strong correlations were consistently observed between TOC (0–15,000 µg/L) and both HPC counts (CFU) and total bacteria (as 16S rRNA gene copies) during intervals involving regular 3X per week 80% water changes in Experiment A1 (Average R2 values of 0.89 and 0.97 for 16S rRNA genes and HPCs, respectively) (Table 1). Experiment A2 was distinct from A1 in terms of accumulated biomass, a slightly lower temperature, and a longer stagnation during inoculation (25 vs. 13 days for A1). When 3X per week 80% water changes were resumed to initiate experiment A2, the correlations of HPCs and 16S rRNA to TOC correspondingly weakened (R2 = 0.65 and 0.63, respectively) (Table 1). Finally, in Experiment A3, when stagnation was extended by decreasing the 80% water change frequency to 1X per week, no significant correlations with added TOC were identified (Figure 1; Table 1).

Bottom Line: R2 > 0.89).R2 = 0.82 to 0.97, for 2 out of 4 time points) and over a limited TOC range (0-1000 µg/L), no other correlations were identified between other OPPPs and added TOC.These results suggest that reducing organic carbon in distributed water is not adequate as a sole strategy for controlling OPPPs, although it may have promise in conjunction with other approaches.

View Article: PubMed Central - PubMed

Affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. kwilli@vt.edu.

ABSTRACT
Controlling organic carbon levels in municipal water has been hypothesized to limit downstream growth of bacteria and opportunistic pathogens in premise plumbing (OPPPs). Here, the relationships between influent organic carbon (0-15,000 µg ozonated fulvic acid /L) and the number of total bacteria [16S rRNA genes and heterotrophic plate counts (HPCs)] and a wide range of OPPPs (gene copy numbers of Acanthamoeba polyphaga, Vermamoeba vermiformis, Legionella pneumophila, and Mycobacterium avium) were examined in the bulk water of 120-mL simulated glass water heaters (SGWHs). The SGWHs were operated at 32-37 °C, which is representative of conditions encountered at the bottom of electric water heaters, with water changes of 80% three times per week to simulate low use. This design presented advantages of controlled and replicated (triplicate) conditions and avoided other potential limitations to OPPP growth in order to isolate the variable of organic carbon. Over seventeen months, strong correlations were observed between total organic carbon (TOC) and both 16S rRNA gene copy numbers and HPC counts (avg. R2 > 0.89). Although M. avium gene copies were occasionally correlated with TOC (avg. R2 = 0.82 to 0.97, for 2 out of 4 time points) and over a limited TOC range (0-1000 µg/L), no other correlations were identified between other OPPPs and added TOC. These results suggest that reducing organic carbon in distributed water is not adequate as a sole strategy for controlling OPPPs, although it may have promise in conjunction with other approaches.

No MeSH data available.


Related in: MedlinePlus