Abundance of Acanthamoeba spp. and Hartmannella vermiformis in artificial waters and the association with environmental factors
Date Issued
2009
Date
2009
Author(s)
Ming, Kai-Wen
Abstract
Acanthamoeba spp.and Hartmannella vermiformis were free-living amoebae and distributed widely in the natural and man-made aquatic environments. These amoebae are not only infective to human but also the hosts for other pathogenic bacteria to multiply in the environments. This study applied the real-time qPCR (Real-time quantitative polymerase chain reaction, Real-time qPCR) and constructed the cell-based standard curves to quantify these two types of amoebae in the cooling towers and hot water systems of eight nursing homes, as well as a multiple wastewater treatment plant. The environmental factors including the water characteristics, maintenances of the facilities and operation conditions were also measured or recorded to determine the factors significantly affecting the presence and the concentrations of these two targeted amoebae by the statistical analysis. The results shown that the cell-based standard curves constructed by real-time qPCR could adjust the DNA loss which was caused during the sample pretreatments; and the PCR inhibition could be solved by the appropriate PCR dilution. According to this, our study indicated that the positive rates of Acanthamoeba spp. in the water, floating biofilm (FB) and substrate biofilm (SB) samples of cooling towers were 70.4%, 22.8% and 53.8%, respectively; and the cell concentrations of the Acanthamoeba-positive samples were 965.3 cells/L, 9 cells/cm2and 1235.7 cells/g, respectively. For H. vermiformis, the positive rates and concentrations of the positive samples were 85.2%, 66.7%, 92.3% and 1664 cells/L, 49.3 cells/ cm2, 14215 cells/g, respectively. In the hot water systems, the positive rates of Acanthamoeba spp. and the averaged concentrations of positive samples in the water, faucet swab and showerhead swab samples were 60.3%, 25%, 40% and 26.1 cells/L, 3.51 cells/cm2, 0.31 cells/cm2, respectively; For H. vermiformis, the positive rates and the concentrations of the positive samples were 69.1% and 800.7 cells/L in water samples, 56.3% and 39.8 cells/cm2 in the faucet swabs and 60% and 5.6 cells/cm2 in the showerhead swabs. The result revealed that the positive rates and cell concentrations of H. vermiformis wereboth higher than Acanthamoeba spp. in the cooling towers and the hot water systems. In contrast, the positive rates of Acanthamoeba spp. in the influent water, effluent water from secondary clarifier and chlorine contact tank (88.9%, 89.2% and 83.8%) and the averaged concentrations of the positive samples (2208.5 cells/L、5594.4 cells/L、3673.4 cells/L) were both higher than those of H. vermiformis (positive rates: 77.8%, 78.4% and 78.4%; mean concentrations: 1784.4 cells/L、576.8 cells/L、548.8 cells/L). The results of statistical analysis indicated that the levels of total culturable bacteria were positively contributed to the concentrations of Acanthamoebae spp. in the cooling tower water samples（P = 0.062）, and the trend also presented for H. vermiformis in the cooling tower water samples and the swab samples of the hot water systems（P = 0.003 and 0.001）. In addition, total suspended solids were positively related to the concentrations of Acanthamoeba spp. in the hot waters (P = 0.09), while the contrary trend was observed for H. vermiformis (P<0.0001). Water temperature was adversely associated with the concentrations of H. vermiformis in cooling tower waters and swabs of hot water systems (P = 0.033 and 0.037). Moreover, concentrations of total Legionella and viable Legionnella significantly affected the concentrations of Acanthamoeba spp. and H. vermiformis in the hot waters and FB samples, respectively (P = 0.032 and 0.095). In general, H. vermiformis appeared to be more sensitive to the variance of environmental factors than Acanthamoeba spp. in the aquatic habitats.
Subjects
real-time qPCR
cooling towers
hot water systems
wastewater treatment plant
environmental factors
positive rate
concentrations of positive samples
Type
thesis
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