Protection of potable water supplies demands a better understanding of the factors controlling migration of disease causing bacteria in subsurface environments. In this study, the migration behaviour of the waterborne pathogenic microorganisms Escherichia coli O157:H7 and Yersinia enterocolitica was investigated in water saturated granular systems. Both facultative bacteria were grown under aerobic and anaerobic conditions and further acclimatized to a microaerophilic or fully aerated environment for 21 h. Experiments were conducted using laboratory-scale packed columns over controlled extreme dissolved oxygen (DO) concentrations. The observed differences in the transport potential of these pathogens were found to depend strongly on the antecedent growth conditions under the tested environmental settings as well with the environmental DO in certain conditions. Further microbial characterization using cell titrations and FTIR spectroscopy gave a greater insight on the source of the surface charge that was found to dominate the attachment phenomena in sand packed columns. Techniques also revealed a probable role of other cell surface macromolecules (LPS) that could account for non-DLVO behaviour. The results illustrate the importance of considering physicochemical conditions relevant to the natural subsurface environment when designing laboratory transport experiments as evidenced by variations in microbe migration as a function of the DO under growth and acclimation. / Keywords: bacterial adhesion, bacterial transport, DLVO, physicochemical characterization, dissolved oxygen, porous media.

The contamination of drinking water by microbial pathogens is recognized as one of the most pressing water supply problems of our day. To minimize the impact of pathogens and parasites on the environment and public health, accurate methods are needed to evaluate their presence and concentration. Although various techniques exist to detect certain pathogens in water (e.g., immunofluorescence or PCR techniques), these are time- and labor-intensive. A direct, real-time method for detection and quantification of target organisms would thus be very useful for rapid diagnosis of water safety. A quartz crystal microbalance with dissipation monitoring (QCM-D) based biosensor for detection of waterborne pathogens (i.e., Escherichia coli O157:H7) was developed. The detection platform is based on the immobilization of affinity purified antibodies onto gold coated QCM-D quartz crystals via a cysteamine self-assembled monolayer. The results show that the optimal sensor response is the initial slope of the dissipation shift. A highly log-log linear response is obtained for detection of E. coli O157:H7 over a broad range of cell concentration from 3 x 105 to 1 x 109 cells/mL. The prepared biosensor also exhibits a log-log linear working range from 107 to 109 cells/mL for E. coli K12 D21, a non-pathogenic model organism. The biosensor also shows satisfactory selectivity using Bacillus subtilis . To our knowledge, this is the first study demonstrating the use of the slope of the dissipation shift as a sensor response when using QCM-D technology. / Keywords: Biosensor, QCM-D, E. coli O157:H7, polyc1onal antibodies, dissipation slope, cysteamine, self-assembled monolayer

This study was conducted to understand the interactions between irrigation water management and water quality (agro-ecological interactions). The Uda Walawe basin, in Southern Sri Lanka was chosen as the study area. Fluctuations in water quality, especially microbiological water quality, affect human health. Since the source of domestic water (drinking and washing) in this region is from the irrigation system, there is a concern for the human health effects. All the potential water sources and the water use habits of the community were identified. The water quality of these sources was then monitored for a period of 5 months (August--December 2000). Second, the water management of the Uda Walawe irrigation system was linked to the differences in water quality. The best quality water was found to come from the shallow wells (seepage water from the irrigation system). Both quantity and quality of the water were shown to fluctuate with canal construction (earthen or concrete) and irrigation water management.

Thesis (PhD.(Medical Virology)--Faculty of Health Sciences)-University of Pretoria, 2007. / Includes bibliographical references.

Water quality is concerning as many still lack access to safe drinking water. Alternate sources such as rivers (FC up to 1600 CFUs/100 mL) and rainwater are often polluted. Rainwater tanks require maintenance to improve water quality, but could be used for non-potable purposes or irrigation. Grahamstown infrastructural failures initiate deviations from DWAF 1996 domestic water guidelines for microorganisms within the distribution system. Frequent testing can decrease risks of waterborne diseases. Limitations to this are inaccessibility of rural areas, distances from testing centres and costs. The low cost H2S strip test able to be used onsite by communities, may aid in risk assessment. H2S strip test results are not affected by sulphate (14 to 4240 mg/L) or nitrite (up to 47 mg/L). Transportation of the H2S strip tests between 10 and 32°C does not modify results significantly. Similarly to other studies: Klebsiella spp.; Enterobacter spp. and Serratia spp. were isolated from H2S strip tests. The mH2S strip test corresponds best with HPC in treated water, while in untreated river water it has approximately 90% correspondence with FCs, while survival of FC causes discrepancies with the H2S test after 22 days. A faecal coliform inactivation rate of 0.1 CFUs/ day, may be longer than many pathogens. Faecal source tracking, not currently practised in South Africa, could aid health risk assessments for disaster management, which would improve the NMMP programme. Bacterial survival times could propose the time period for which water is unsafe. Bifidobacteria and Rhodococcus are proposed to help identify the faecal pollution source. But enumeration of Rhodococcus is too lengthy (21 days). The tracking ratio of bifidobacteria (between 0.1 to 6.25) is not source definitive. The bifidobacteria survival rate, could indicator the time since faecal pollution. The bifidobacteria average survival rate is 2.3 CFUs per day for both groups. The culturability and selectivity of agar is still poor, with total bifidobacteria less selectively culturable. Enterococci overgrowth of TB was decreased by Beerens media. SUB is still useful to identify potential human faecal inputs. A single tracking method is thus not suitable alone, but requires a combination of techniques.

Ph.D. / Members of Cichlidogyrus are monogenean ectoparasites occurring on the gill filaments of mainly cichlid fishes. An overview of the taxonomic background of the genus and motivation for the study is provided. In this study, existing information on their distribution is organised in a comprehensive table which includes 85 species, their taxonomic authors, hosts and localities from which they have been recorded. Representatives of this genus occur mainly in Africa, but have been found on cichlids as far as Mexico. Host specificity of members of the group is discussed. During the present investigation specimens of the genus Cichlidogyrus were found parasitising Pseudocrenilabrus philander philander, in the Padda Dam in Johannesburg, Gauteng, South Africa. Specimens were examined and identified as Cichlidogyrus philander, previously described from the same host, from Lake Kariba, in Zimbabwe. The morphology was studied utilizing light – and scanning electron microscopy. Specimens were stained with Horen‟s trichrome and photographed. Furthermore 100 whole mounted specimens, which were fixed and mounted in glycerine-ammonium-picrate, were measured. Larval specimens, and mature individuals with eggs in situ, were examined. The investigation of the ecology entailed monthly surveys during which a total of 245 fish specimens were collected with the aid of hand nets, over a period of 14 months (from March 2006 to June 2007). The fish were transported to the laboratory and killed by severing the spinal cord. Gills of specimens of P. p. philander (111), Gambusia affinis (105), Tilapia sparmanii (28) and one (1) 2 specimen of Cyprinus carpio were inspected, for the presence of monogeneans, with the aid of a dissection microscope. Only members of P. p. philander were parasitised by C. philander, indicating strict host specificity. The number of specimens varied from 0 to 184 per fish. The highest mean intensity of 91.6 occurred in the winter month of June 2007, although no significant correlation between season and the occurrence of this parasite was recorded. The prevalence was 100 % for ten of the fifteen surveys and no preference for host sex was recorded. The intensity of the infection correlates positively to the total length of the host, i.e. larger hosts harbour more worms. A positive correlation between condition factor and the total number of worms was found, indicating that more parasites are found on fish with a normal condition factor. No significant difference occurred between the numbers of parasites collected from gill arches on the left or right sides of fish. Statistical analysis of data showed that parasites disperse across the four gill arches with a higher proportion of parasites on the third and second gill arch. The highest proportion of the collected parasites occurred on the dorsal regions and on the distal ends of the gill filaments. Water quality variables do not significantly correlate to the prevalence, abundance or mean intensity of this parasite. This is the first ecological study conducted on specimens of C. philander, worldwide.

No description available.

No description available.

No description available.

The spread of antibiotic-resistant microorganisms in the environment is recognized widely as an important public health issue, with concerns about future ability to treat infectious diseases. The main risk to public health is that the resistance genes are transferred from environmental bacteria to human pathogens. Safe water is one of the most important needs in public health in the twenty first century. The major health threat posed by drinking unsafe water is the transmission of infectious diseases, which are the leading causes of mortality and morbidity for children under the age of 5 and it is estimated to cause 1.5 million deaths annually in developing countries. In addition to the wide spread cases of water-borne diseases resulting from the contamination of water sources, concerns have been raised when these diseases fail to be cured due to development of resistance to most prescribed antibiotics by the contaminating microorganisms. It is now a well-established fact that E.coli is a significant cause of diarrheal illnesses both in infants and adults in many parts of the world. Data on clinical isolates is plenty while less attention has been given to environmental isolates of these enteric pathogens. Samples from the environment such as water may serve as probable reservoirs of these pathogens; this is compounded by the entry of functional compounds of antibiotics into waterways, through humans and animals that have ingested antibiotics. This is because antibiotics are not completely metabolized and may enter waterways through the waste products of these humans or animals.Studies on antimicrobial resistance is important in order to detect changes in patterns of resistance, implement control measures on the use of antimicrobial agents, and to prevent the spread of multidrug-resistant strains of bacteria. It also provides surveillance data for antibiotic resistances, necessary to define or update guidelines for empirical treatment, as well as a guide for appropriate antibiotic supplies. Study objectives: The objectives of this research were: (i) to determine the total and faecal coliform status of drinking water sources, as an indication of quality; (ii) to determine the bacteriological profile of bacteria flora in the drinking water sources; (iii) to determine prevalence and susceptibility profiles of antibiotic resistant water-borne E.coli; (iv) to investigate the virulence genes associated with multiple antibiotic resistant E. coli isolates; (v) to compare three laboratory based techniques: PCR, API 20E, and Culture based methods used for detection of E.coli and (vi) to determine the association between multiple antibiotic resistance and radiation sensitivity (D10). © University of South Africa 2014 VII Methodology: Four hundred and sixty four (464) water samples were collected for assessment between June 2011 and May 2012. The samples were collected from 57 sampling sites, from six different water sources including: boreholes (10), a canal (1), dams (15), hand-dug wells (15), a river (1), and streams (15). Total coliforms, faecal coliforms, and E. coli analysis were done by the MPN method. Bacteria isolation and identification were done using API 20E, conventional methods, and a PCR based DNA STRIP technology that allows simultaneous detection of virulence genes and confirmation of E. coli isolates. Antibiotic susceptibility testing was also conducted using the Kirby-bauer method. Radiation sensitivity was done using a cobalt 60 source. Results: The results obtained indicated that all the water sources were of poor quality in terms of microbial distributions with total coliform and faecal coliform counts ranging between 0 to 2.4x103 MPN/100ml. E. coli counts ranged between 10 to 7.9x101MPN/100ml. Disease risk assessment of the various water sources indicated that dam water sources presented a high disease risk, while borehole water sources had a low disease risk. A total of five hundred and twenty bacterial isolates (520) were obtained during the period of study. Three hundred and five (305) isolates representing 58.65% of the total were obtained during the dry season, as against (205) representing 41.35% in the rainy season. The most commonly occurring bacteria in the water samples was Klebsiella spp constituting 20%. The next most occurring organism was E. coli (18.7%). This was followed by Pseudomonas aeruginosa (15.61%), Enterobacter spp. (15.4%), Proteus vulgaris (13.1%), and Enterococcus faecalis (9.2%). The least isolated bacteria were Vibrio cholerae (1.2%) and Shigella spp. (1.2%). The prevalence of multi drug resistance E. coli was 49.48 %. E. coli isolates showed a high sistance patterns to the tested antibiotics. They were most resistant to penicillin (32.99%), cefuroxime (28.87%), erythromycin (23.71%), and tetracycline (21.45%). In contrast, they were susceptible to nitrofurantoin (93.8%), cefotaxime and amikacin (91.75%), gentamicin (90.7%), nalidixic acid (89.65%), ciprofloxacin (74.2%), chloramphenicol (69.07%), pipemidic acid (65.97%) and cefuroxime (52.58%). Sixty-three percent (63%) of the multidrug resistant E. coli strains recorded a multiple antibiotic resistance (MAR) index value of >0.2. Six (6%) percent of he multiple antibiotic resistant were eae virulence genes producing however, none of the E. coli isolates produced the stx1 and stx2 virulent gene. The analytical profile index (API) recorded specificity and sensitivity of 99.7% and 98.50 % respectively for the detection of E. coli. The © University of South Africa 2014 VIII culture/ biochemical based methods for detection of E coli recorded specificity of 81.82% and a sensitivity of 96.91%. There was no association (P> 0.05) between radiation sensitivity (D10) and antibiotic resistances. Conclusion: The study has confirmed that majority of the water sources used for drinking and domestic purposes in the study area are highly contaminated with high levels of faecal coliforms above the recommended standards. There were also resence of bacteria of public health importance in the water sources. Both animals and humans could be sources of faecal bacteria contamination of the drinking water sources. The study confirmed a high prevalence of multiple antibiotic resistances in E. coli isolates. The eae virulence gene was associated with some of the multiple resistant E. coli isolates. The study also concludes that API 20E has a high specificity and sensitivity close to that of the PCR. Lastly, There is no association between multiple antibiotic resistant indexes and radiation sensitivity (D10) of antibiotic resistant E. coli. / School of Environmental Sciences / D. Phil. (Environmental Science)