published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

This thesis studies antibiotic sensitivity of bacteria isolated from city water distribution systems.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Microorganisms show a tendency to accumulate on surfaces in aqueous environments to form biofilms. Microbial biofilms represent a significant problem in public health microbiology as the development of these microbial communities, especially in water distribution systems, may lead to (i) the enhanced growth of opportunistic pathogens, (ii) the development of organoleptic problems, (iii) the reduction in the flow rate and (iv) the regrowth of microorganisms. In this project, biofilm monitors were installed in a large water distribution system to study biofilm phenomena in drinking water systems, and to deduce the biological stability and quality of the potable water. Measurements of biofilm formation potential showed that biofilms did not reach a steady state after 100 to 150 days. The microbial cells in these biofilms were mostly non-culturable. The contribution of the heterotrophic colony count to active biomass, as determined with cell numbers based on ATP measurements were often < 1%, while the ratio of heterotrophic plate counts and direct acridine orange counts were also <1%. The ratio between cell numbers based on ATP measurements and direct acridine orange counts were often < 100%. Results also showed that under certain conditions, such as those investigated in the present study, 1 pg of ATP may not be equal to approximately 104 active bacteria/cells, as stipulated by previous investigations, and that the average ATP content per active bacterial cell is indeed less than 10-16 - 10-15 g. It was calculated that threshold values for assimilable, and dissolved organic carbon below -5 IJg Gil and -0.5 mg Gil, respectively, should be target values for the control of biofilm formation in this system. It was shown that polyethylene, polyvinylchloride, teflon, plexiglass, copper, zinc-coated steel and aluminium provide favourable attachment surfaces that allowed primary colonisation and subsequent biofilm formation. Significant (p < 0.05) differences in surface colonisation on the materials were observed, indicating that the composition of the material has a direct influence on microbial colonisation. The two grades of stainless steel evaluated in this study were the least favourable materials for biofilm formation. It was further demonstrated that the nature of the surface of these materials, flow conditions and water type all had a direct influence on biofilm formation. While modification of the attachment surface did not result in significant differences (p > 0.05) in disinfection efficiency of two commonly used biocides, the concentration of the biocide, as well as the material to which the biofilm is attached, greatly influenced biocidal efficiency. The results show that biofilm monitoring needs to be implemented at the water treatment plants in addition to common biostability measurements. / AFRIKAANSE OPSOMMING: Mikro-organismes neig om te akkumuleer aan oppervlaktes in akwatiese omgewings om biofilms te vorm. Mikrobiese biofilms verteenwoordig In betekenisvolle probleem in publieke gesondheidsmikrobiologie omdat die ontwikkeling van hierdie mikrobiese gemeenskappe in waterverspreidingsisteme mag lei tot (i) die verhoogde groei van opportunistiese patogene, (ii) ontwikkeling van organoleptiese probleme, (iii) die vermindering in die vloeitempo en (iv) die hergroei van mikro-organismes. In hierdie projek was biofilm monitors geïnstalleer in In groot waterverspreidingsisteem om biofilm fenomene in drinkwatersisteme to bestudeer, en om die biologiese stabiliteit en kwaliteit van drinkwater af te lei. Bepalings van biofilmvormingspotensiaal het aangetoon dat biofilms nie In stabiele stadium na 100 tot 150 dae bereik nie. Die mikrobiese selle in hierdie biofilms was meestal niekweekbaar. Die bydrae van die heterotrofiese kolonie tellings tot aktiewe biomassa, soos bepaal deur seltellings gebaseer op ATP metings was dikwels < 1%, terwyl die verhouding van die heterotrofiese plaatteIIings en direkte akridien oranje tellings ook < 1% was. Die verhouding tussen seltellings, gebaseer op ATP metings en direkte akridien oranje tellings was dikwels < 100%. Resultate het ook aangetoon dat onder sekere omstandighede, soos dié wat ondersoek was in die huidige studie, 1 pg ATP nie gelyk is aan min of meer 104 aktiewe bakterieë/selle soos gestipuleer deur vorige ondersoeke nie, en dat die gemiddelde ATP inhoud per aktiewe bakteriële sel inderdaad minder as 10-16 tot 10-15 g is. Dit was bereken dat die drempelwaardes vir assimileerbare en opgeloste organiese koolstof onder -51-1g C/l en -0.5 mg C/l, onderskeidelik, teikens moet wees vir die beheer van biofilmvorming in hierdie sisteem. Dit was aangetoon dat polyetileen, polyvinielchlroried, teflon, plexiglas, koper, sink-bedekte staal en aluminium gunstige aanhegtings oppervlaktes voorsien wat primêre kolonisering en daaropvolgende biofilmvorming toelaat. Betekinisvolle (p <0.05) verskille in oppervlak kolinisering op die materiale was waargeneem, wat aandui dat die samestelling van die materiaal In direkte invloed op mikrobiese kolonisering het. Die twee tipes vlekvryestaal wat geëvalueer was in hierdie studie, was die minder gunstige materiale vir biofilmvorming. Dit was verder gedemonstreer dat die aard van die oppervlak van hierdie materiale, vloeitoestande, en water tipe almal In direkte invloed het op biofilmvorming. Terwyl die aanpassing van aanhegtingsoppervlak nie die ontsrnettinqsdoeltreffendheid resultaat van die twee algemeen-gebruikte biosiede betekinisvol (p > 0.05) beïnvloed het nie, het die konsentrasie van die biosiede doeltreffendheid grootliks beïnvloed. asook die aanhegtings-materiaal, biosied Die resultate het aangetoon dat biofilm monitering geïmplementeer moet word by waterbehandelingsaanlegte as In alternatief vir algemene biostabiliteit metings.

Microcystin-LR (MCLR) is hepatotoxic to animals and humans with disruption of liver structure causing cytoskeletal damage, necrosis and pooling of blood in the liver, leading to large increase in liver weight. It is also a strong liver tumor promoter and protein phosphatase inhibitor. Microcysin-LR binds protein phosphatases 1 and 2A, and influences regulation of cellular protein phosphorylation. In the present study, a colloidal gold based immunoassay test strip was developed for Microcystin-LR detection. The detection limit was found to be 1 ng/mL. 5 nm colloidal gold test strips exhibits more efficient for detection, compared with 20 nm colloidal gold test strips. The interaction between Microcystin-LR antibody (immunoglobulin G) and colloidal gold nanoparticles was investigated by various analytical methods, including Ultraviolet/Visible (UV/VIS), Fourier Transform Infrared (FTIR) and Fluorescence spectroscopy as well as transmission electron microscopy (TEM). / by Jiesi Xu. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

The aim of this study was to investigate the microbiological quality of drinking water at the source (taps at eThekwini laboratories, standpipes and mobile community tankers) and corresponding point-of-use (storage containers and ground tanks) supplied to peri-urban areas in Durban by eThekwini Municipality. It also aimed to identify factors associated with deterioration in water quality such as storage of water, household demographics, hygiene and sanitation practices. In order to determine the microbial quality of drinking water, the pour plate method (for enumeration of heterotrophic organisms) and the membrane filtration technique (for total coliforms and E. coli enumeration) were used. Conductivity, turbidity, pH and total and residual chlorine levels of drinking water were measured. Microbial and physico-chemical data was collated and statistically analysed with epidemiological data from an associated study to determine the link between microbial quality of drinking water, household demographics, health outcomes, socio-economic status, hygiene and sanitation practices. Findings showed that all point-of-use water was unsafe for human consumption as a result of either poor source water quality, in the case of standpipes, and microbial contamination at the point-of-use, in the case of ground tanks and community tankers. The latter could be attributed to unsanitary environments, poor hygiene practices or poor wateruse behaviour. Households which included children aged 0-5 years and in which open-top containers were used for water storage had the highest rates of diarrhoea and vomiting. Water from ground tanks had the best microbial quality but people in households using this water presented with the highest rate of diarrhoea. Therefore provision of microbially safe drinking water will not reduce the rate of health outcomes if addressed in isolation. In order to reduce water-associated illness, provision of safe and adequate amounts of water, hygiene and sanitation education and education on water-use behaviour should be provided as a package. The provision of improved water delivery systems does not ensure that drinking water is safe for human consumption. Measures, such as point-of-use water treatment should be considered to ensure that drinking water provided at the source and point-of-use is microbially safe for human consumption. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.

In this problem, an attempt was made to determine the fate of various species of bacteria which had previously been isolated from other sources when inoculated into Denton tap water.

This thesis investigates the susceptibility of various bacterial species to standard purification process.

Access to a safe drinking water supply is a critical issue in a number of places across the globe. Conventional water quality monitoring technologies are slow, often taking at least two days to produce results. In recent years, there has been extensive research into emerging technologies that provide real-time results; however, there is no technology which detects all classes of biological contaminants. Biological contaminants are 5 particularly difficult to detect and quantify due to low concentrations typically present. It is not feasible to identify all biological contaminants present in a water supply; therefore, it is necessary to determine which are of highest concern based factors such as health significance, infectivity, and prevalence. The intent of this research is to evaluate microbiological detection methods and technologies based on their applicability for continuous real-time detection. This research will complement current research on biological water quality monitoring technologies for use in developing regions or in the event of an emergency and will provide suggestions for future research efforts.

The bacterium Aeromonas hydrophila is a known fish and opportunistic human pathogen commonly occurring in surface waters supplying drinking water distribution systems. The major concern of government and drinking water providers is that A. hydrophila may invade and become established in the biofilm of a distribution system, thus potentially leading to outbreaks of disease. The purpose of this study was to survey source water, distribution system biofilm, and to establish a simulated distribution system to explore the possibility of A. hydrophila invading and becoming established under normal and disrupted treatment conditions. A. hydrophila (AH) medium and the API-20E system were used for identification, while Ampicillin-Dextrin Agar (ADA) was used for enumeration. Presumptive counts were high in source water approaching 103 CFU/ml during summer months. Biofiim from an actual distribution system showed the presence of A. hydrophila in 10 % of the samples. In the simulated distribution system A. hydrophila was never found in the bulk water or biofilm under normal treatment condition, showing disinfectant efficiency. Under disrupted treatment conditions A. hydrophila was not able to colonize a pre-established biofilm over a 14 week period. / Department of Biology

Tap water collected according to standard methods was examined for microbial presence. Epifluorescent diagnoses using redox probe 5-cyano-2,3ditolyl tetrazolium chloride (CTC), 4',6-diamidino-2-phenylindole (DAPI), and acridine orange (AO) were employed for direct evidence of microorganisms. Evidence of total (DAPI or AO), respiring (CTC) bacteria, and heterotrophic plate count (HPC) was determined on multiple occasions during the summer, fall, and winter 1996-1997. Pseudomonas aeruginosa, Acinetobacter sp., Bacillus licheniformis, and Methylobacterium rhodinum were isolated and identified by the API and Biolog system using GN and GP procedures. On the basis of comparisons presented in this study between the CTC method and the standard HPC procedure, it appeared that the number of CTC-reducing bacteria in the tap water samples was typically higher than that determined by HPC, indicating that many respiring bacteria detected by the CTC reduction technique fail to produce visible colonieson the agar media used. In the seasonal data obtained by the CTC method, no difference was shown among respiring bacterial counts obtained from June through January. In the examination of P. aeruginosa viability in presence of chlorine, the number of CTC-positive bacteria exceeded the number of CFU by more than 2 logs after exposure to chlorine, suggesting that reliance on HPC overestimate the efficacy of disinfection treatment. In inactivation assays using the Biolog MT plate, no sensitivity to chlorine or chloramine disinfectants was noted even at high concentration levels (5 mg/liter). Following initial drop, bacterial activities increased as contact time increased. Thus, it appears that the MT microplate provides too low a cell concentration, too great a contact time, and/or too low a concentration of tetrazolium dye within the well for successful analysis of disinfectant capability to selected bacterial strains isolated from distribution water. / Department of Biology