Abstract
Notwithstanding direct detection of microbial/viral pathogens or their associated toxins, the quality of drinking water may also be evaluated according to its pro-inflammatory potential. In this latter setting, contamination with pathogens or their products is determined according to the magnitude of activation of blood-derived immune/inflammatory cells following exposure to test water samples in vitro, usually by monitoring the synthesis of pro-inflammatory cytokines. The primary objective of the current study was to apply this procedure to evaluate the pro-inflammatory potential of water sampled at entry, as well as at various stages of treatment, from 3 major water treatment facilities in the greater Pretoria region, viz., the Daspoort, Hartbeespoort, and Rietvlei Water Treatment Facilities. Control water samples included domestic tap water, bottled water from a commercial source, and distilled water. Peripheral blood mononuclear leukocytes (MNL) were isolated from the blood of healthy, adult, human volunteers (n=3), enumerated, suspended in tissue culture medium RPMI 1640 containing antibiotics at a concentration of 1x10 6 /ml, and exposed to the various water samples (10%) for 18 h at 37°C. Following incubation, the cell-free supernatants were assayed for the cytokine, interleukin-6 (IL-6), using a quantitative, sandwich, enzyme immunoassay procedure. The mean values for the untreated control system and for a positive control system exposed to bacterial endotoxin (120 ng/ml) were 153.5 ±17 and 1 561 ±30 pg/ml, respectively (p= 0.03). The production of IL-6 was unaffected following exposure of MNL to the control water samples. However, inlet water sampled from all three facilities, especially Hartbeespoort, resulted in significant activation of production of IL-6 by MNL, which declined with progressive treatment, consistent with removal of pro-inflammatory contaminants. Surprisingly, however, a rebound in pro-inflammatory activity was evident in outlet water sampled from Hartbeespoort. In conclusion, the results of the current study appear to support the efficiency of water treatment procedures at the Daspoort and Rietvlei Treatment Facilities, while confirming the usefulness of IL-6-based assays as adjuncts to conventional water quality testing procedures. Keywords : Endotoxin, inflammatory activity, interleukin-6, mononuclear leukocytes, water quality
Highlights
Traditional water quality testing techniques test for the presence of indicator organisms (Hunter, 2003)
The balance is likely to consist of natural killer cells and other leukocyte subtypes represented at low concentrations in blood
Traditional water treatment procedures such as chlorination are designed to eliminate living organisms, but chlorination has little or no effects on bacterial breakdown products such as endotoxin (Gorbet and Sefton, 2005). Some assays such as the limulus amoebocyte lysate (LAL) test detect microbial breakdown products such as Gram-negative bacterial endotoxin, which may be present in river and drinking water (Poole et al, 2003; Wichmann et al, 2004; Gorbet and Sefton, 2005; Pool, 2008), these procedures are ineffective in the detection of other pyrogenic substances (Gorbet and Sefton, 2005; Hodgson, 2006)
Summary
Traditional water quality testing techniques test for the presence of indicator organisms (Hunter, 2003). In the study reported by Wichmann et al (2004), exposure to treated drinking water samples did not induce cytokine secretion by human leukocytes in vitro, while contrasting effects were observed following exposure to all the river water samples tested, confirming the findings of an earlier study (Pool et al, 2003). These latter authors reported that induction of secretion of the cytokine, interleukin (IL)-6, was dependent on the concentration of the contaminant(s) and origin of the water samples. Difficultto-detect pro-inflammatory substances in water may pose a threat to public health
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