Dissertations / Theses on the topic 'Pathogen reservoir'

Background: In order to optimize net transmission success, parasites are hypothesized to evolve towards causing minimal damage to their reservoir host while obtaining high shedding rates. For many parasite species however this paradigm has not been tested, and conflicting results have been found regarding the effect of arenaviruses on their rodent host species. The rodent Mastomys natalensis is the natural reservoir host of several arenaviruses, including Lassa virus that is known to cause Lassa haemorrhagic fever in humans. Here, we examined the effect of three arenaviruses (Gairo, Morogoro and Lassa virus) on four parameters of wild-caught Mastomys natalensis: body mass, head-body length, sexual maturity and fertility. After correcting for the effect of age, we compared these parameters between arenavirus-positive (arenavirus RNA or antibody) and negative animals using data from different field studies in Guinea (Lassa virus) and Tanzania (Morogoro and Gairo viruses). Results: Although the sample sizes of our studies (1297, 749 and 259 animals respectively) were large enough to statistically detect small differences in body conditions, we did not observe any adverse effects of these viruses on Mastomys natalensis. We did find that sexual maturity was significantly positively related with Lassa virus antibody presence until a certain age, and with Gairo virus antibody presence in general. Gairo virus antibody-positive animals were also significantly heavier and larger than antibody-free animals. Conclusion: Together, these results suggest that the pathogenicity of arenaviruses is not severe in M. natalensis, which is likely to be an adaptation of these viruses to optimize transmission success. They also suggest that sexual behaviour might increase the probability of M. natalensis to become infected with arenaviruses.

Studies of extraintestinal infections caused by genetically related strains of Escherichia coli among unrelated people have demonstrated the epidemic potential of this group of bacteria. These related extraintestinal pathogenic E. coli (ExPEC) may have a common source. Our group recently described how retail meat, particularly chicken, may be a reservoir for ExPEC causing human urinary tract infections (UTIs). By moving upstream on the farm to fork continuum, this study tests whether the reservoir for ExPEC is in food animals themselves. A total of 824 geographically and temporally matched E. coli isolates from cecal contents of slaughtered food animals (n=349) and human UTI (n=475) sources were compared. Using 6 different typing methods, an evolutionary relationship was observed between E. coli isolates from the food animal reservoir and human UTI. Moreover, chicken was the predominant animal species from where the related isolates originated. Using an evolutionary model, chicken was determined to be the most likely source of the human UTI isolates. This study confirmed that an animal reservoir, principally in chicken, may exist for ExPEC causing community-acquired UTI.
Les études portant sur les infections extra-intestinales causées par des souches d'Escherichia coli génétiquement apparentées, chez des personnes non reliées entre elles, ont démontré le potentiel épidémique de ce groupe de bactéries. Ces souches d'E. coli pathogènes extra-intestinales (ExPEC) apparentées auraient possiblement une source commune. Notre groupe a récemment décrit comment la viande de détail, plus particulièrement le poulet, pourrait être un réservoir d'ExPEC responsables d'infections urinaires (IUs) chez les humains. En se déplaçant plus en amont dans le continuum de la ferme à la fourchette, cette étude teste si le réservoir d'ExPEC se trouve dans les animaux de production eux-mêmes. Un total de 824 isolats d'E. coli de provenances géographique et temporelle communes, prélevés dans le contenu caecal d'animaux abattus (n=349) et de cas d'IU humaine (n=475) ont été comparés. Par l'utilisation de 6 différentes méthodes de typage, une relation évolutionnaire a été observée entre les isolats d'E. coli provenant du réservoir animal et d'IU humaine. De plus, le poulet était l'espèce animale prédominante parmi les isolats parentés. L'utilisation d'un modèle évolutionnaire a permis de déterminer que le poulet est la source la plus probable des isolats d'IU humaine. Cette étude a confirmé qu'un réservoir animal, principalement chez le poulet, pourrait exister pour les ExPEC qui causent des IUs acquises en communauté.

Estuarine environments are biologically productive ecosystems that are both economically and socially important. Consequently, a decline in the microbiological water quality can pose a risk to human health and have severe socioeconomic consequences, especially for areas that rely on tourism and shellfisheries for income. The enumeration of faecal indicator bacteria (FIB) in water samples has been the paradigm for estimating water quality in coastal zones, but there is an emerging view that sediments are a poorly studied and yet a significant reservoir of FIB. The aims of this thesis were: (I) to investigate the role of sediments as a reservoir for FIB and other potentially pathogenic bacteria; (II) to examine the spatial ecology of FIB in relation to sediment composition (grain size and organic matter content); (III) to investigate the influence of point and diffuse pollution sources on the abundance of bacteria in marine and estuarine sediments; (IV) to investigate the abundance of human pathogenic bacteria in the Conwy estuary, North Wales, UK, and (V) to investigate the influence of suspended particulate matter (SPM) on the survival of FIB in both fresh and brackish water. Culturable E. coli, total coliforms, enterococci (FIB), Salmonella, Campylobacter, Vibrio spp. and heterotrophic bacteria were enumerated in sediments and water from the Conwy estuary that is subject to various point and diffuse sources of pollution. FIB counts were three orders of magnitude greater in sediments compared with the overlying water column, demonstrating that estuarine sediments are a significant reservoir for FIB and other potential pathogens. In addition, sediment grain size analysis and organic matter content determinations revealed that finer sediments such as clay, silt and very fine sand contained significantly higher concentrations of all bacterial groups enumerated. The enumeration of FIB in marine sediments surrounding an offshore sewage outfall pipe revealed that spatial variations in FIB abundance reflected the course of the sewage effluent plume as predicted by a hydrodynamic model, demonstrating the impact of point sources of microbial pollution on the underlying sediments. To address the actual pathogen content of sediments in the Conwy estuary (rather than only indicator bacteria), PCR and qPCR were utilized to detect and quantify known pathogen virulence genes, revealing that estuarine sediments are a reservoir for pathogenic bacteria. Furthermore, qPCR suggested greater concentrations of FIB compared with culture counts from the same sample, indicating the possible presence of viable but non-culturable (VBNC) bacteria. Consequently, sediment-associated bacteria pose a risk to human health if they are resuspended into the water column under certain hydrodynamic processes, as tide-dominated estuaries usually contain large areas of fine sand that are easily mobilized. To investigate the influence of SPM concentration on FIB survival, fresh and brackish water containing low (~16 mg/l), high (~160 mg/l) and extreme (~1650 mg/l) SPM concentrations were inoculated with crude sewage and sheep faeces. FIB were enumerated every 24 hrs for 5 days, revealing that SPM concentrations influence FIB survival in brackish water but had minimal influence in freshwater over time. In general, FIB concentrations increased with a decrease in SPM concentration. These data add to a limited body of evidence on the role of sediments as a reservoir for pathogenic bacteria, with implications for routine monitoring protocols that assess the microbial pollution of environmental waters. In addition, these data suggest that catchment-based risk assessments of microbial pollution in aquatic systems should consider the source of FIB, the hydrodynamics of the environment, and the subsequent influence of SPM concentrations, all of which determine the survival of FIB in aquatic environments.

This was a study to determine if invertebrate vectors (i.e. flies and slugs) were able to acquire human pathogens from local ruminant faeces and potentially transfer them to vegetables or ready-to-eat food. A field survey revealed that slugs are able to acquire pathogenic strains of E. coli O.157 that were indistinguishable from those isolated from local sheep faeces. Laboratory experiments demonstrated that commensal E. coli had relatively long survival rates on and in slugs, where the slugs were able to transfer E. coli by direct contact or excretion. Escherichia coli had a slow decline rate in excreted slug faeces with a decimal reduction time of 13.9 days. The results suggest that slugs have the potential to transfer pathogenic E. coli to vegetables. The second part of this work aimed at identifying temporal or host related relationships in the Campylobacter population of cattle and sheep. The Multi-locus sequence typing (MLST) technique was used in addition to quantifying the prevalence and concentrations of Campylobacter excreted by cattle and sheep present on the same farm. Statistically significant temporal variations were identified in addition to differences between the two hosts. During the faecal sampling, flies were also collected. Flies were found to carry identical sequence types (STs) to those present in local ruminant faecal samples. However, despite the relatively low Campylobacter prevalence in flies, certain STs were over represented, suggesting some degree of host restriction. A low number of slugs were also sampled where the Campylobacter ST isolated, had not been identified on this farm or elsewhere. Flies and slugs are able to acquire E. coli O157 and Campylobacter strains, thus posing a potential risk of transfer to vegetable crops.

Objective: One of the main theoretical proposals of Intensive Short-term Dynamic Psychotherapy (ISTDP; Davanloo, 1990) is that experiencing of previously unconscious guilt over aggressive impulses associated with attachment trauma leads to increase in self-compassion. The present study aimed to test this assumption. Method: Videotaped sessions from five therapies from a randomized controlled trial of 20-sessions of time-limited ISTDP for treatment-refractory depression were rated with the Achievement of Therapeutic Objectives Scale (ATOS; McCullough, Larsen, Schanche, Andrews& Kuhn, 2003b). Degree of patient guilt arousal and self-compassion were rated on all available sessions. Data were analyzed using a replicated single-subject time-series approach. Results: Guilt arousal was not shown to positively predict self-compassion for any of the five patients. For one patient guilt arousal negatively predicted self-compassion two sessions ahead in time. Conclusion: The current study yields no support that the experience of guilt over aggressive feelings and impulses leads to increases in self-compassion. On the contrary, the finding that guilt negatively predicted self-compassion for one patient must be considered as an indication that this treatment process might negatively impact self-compassion for some patients in some contexts. However, there are several methodological limitations to the current study in the light of which the results should be regarded as tentative.

The quality of recreational and shellfishing waters has historically been monitored using commensal, allochthonous bacteria shed in feces (fecal indicator bacteria, FIB). The fate of FIB in the environment should mimic that of bacterial, protozoan, and viral human pathogens, which may also be allochthonous (e.g. Salmonella, Cryptosporidium, or enteric viruses) or autochthonous (e.g. Vibrio spp.) to aquatic environments. FIB are contributed to water from human and animal sources; however, pollution source cannot be determined by conventional FIB measurements. Because fecal source determination is important for pollution remediation and assessment of human health risks, microbial source tracking (MST) methods are increasingly used in water quality studies. The host-specific genes (markers) used for MST include the 16S rRNA of Bacteroides HF183 and the T-antigen of human polyomaviruses (HPyVs). In my work, correlations among FIB, MST markers, and autochthonous pathogens were explored in the context of factors that may influence these relationships. Specifically, the effects of stormwater runoff, sediment resuspension, and survival/persistence of FIB on submerged aquatic vegetation were investigated in a recreational lake. Furthermore, the relationship between FIB and concentrations of the autochthonous pathogen, V. vulnificus, was investigated at water bodies surrounding Tampa Bay. I hypothesized that degraded water quality would influence the concentration and/or population structure of V. vulnificus, a potentially lethal human pathogen. Finally, I hypothesized that the gene encoding a sodium-phosphate transporter (nptA) would be differentially expressed in V. vulnificus strains under varying conditions of salinity and phosphate concentration. I hypothesized that stormwater infrastructure/runoff, SAV, and sediments would serve as reservoirs for FIB, human-associated microbes (HF183 and HPyVs), and allochthonous pathogens (Salmonella, Cryptosporidium, Giardia, and enteric viruses). FIB concentrations in the water were positively associated with those in the sediment, SAV, and with 24hr antecedent rainfall. At least one MST marker or pathogen was found in 35% of samples following rain events. These data were incorporated into a Bayesian model, which predicted pathogen absence when fecal coliform concentrations were low. Stormwater was also shown to be an important reservoir/conveyance system for FIB, human-associated microbes, and pathogens. I hypothesized that polluted estuarine waters in Tampa Bay, and oysters harvested from them, would contain higher V. vulnificus concentrations, and that the population structure would be altered compared to unpolluted waters. Enumeration included direct plating, enrichment followed by plating, and quantitative PCR (qPCR). V. vulnificus colonies isolated directly on mCPC agar were rarely PCR-confirmed, although enrichment and qPCR methods yielded a higher confirmation frequency. Unconfirmed colonies resembling V. vulnificus were identified as V. sinaloensis via 16S rRNA sequence analysis and were more frequently detected in less polluted waters. Comparison of growth rates among V. vulnificus and V. sinaloensis strains in enrichment media and seawater showed that V. vulnificus had faster growth rates (µ) in enrichment media, but that µ of V. sinaloensis strains was greater in seawater. V. sinaloensis presence can therefore lead to overestimation of V. vulnificus concentrations when samples are directly plated. These results highlight a need for better understanding of the ecology and virulence potential of this newly-described species. Finally, I hypothesized that V. vulnificus strains with varying virulence potential would differentially express the nptA gene in response to changes in environmental conditions. Expression studies were performed on biotype 1, 2, and 3 strains, and strains more closely associated with environmental reservoirs (water or oysters) showed up to 100-fold greater nptA expression than strains isolated from clinical cases. Gene expression in environmentally-associated, but not clinically-isolated, strains was highest in media at pH 6.0 vs. those at pH ≥ 7.0 and at 10 / salinity. In contrast, expression was highest among clinical strains at 10 / salinity, pH 8.0 media. Sequence analysis of the nptA gene also divided strains into environmentally- and clinically-isolated groups. These results suggest that differences in gene expression may be related to host preference and may be associated with differential virulence of strains in humans. These studies demonstrate a relationship between water quality (determined by FIB concentrations) and the prevalence of allochthonous and autochthonous human pathogens, and reveal that many environmental habitats may serve as reservoirs for FIB and pathogens. Differences in water quality were further demonstrated to impact the community structure of Vibrio spp. and may affect the relative abundance of strains with greater virulence potential.

All natural aquatic systems harbour a vast variety of microorganisms. In the aquatic microbial food web, the larger microorganisms (i.e. protozoa) feed on the smaller microorganisms (i.e. bacteria and phytoplankton). An increase in nutrient availability results in changes of the microbial food web structure, like altered community composition and blooms of toxic phytoplankton. In this thesis work I hypothesised that nutrient-rich aquatic environments, with strong protozoan predation, favour the occurrence of predation-resistant bacteria like F. tularensis, and that the microbial food web may provide a reservoir for the bacterium between outbreaks. By using a size-structured ecosystem food web model it was shown that the protozoan predation pressure on bacteria, defined as protozoan predation per bacterial biomass, increases with increasing nutrient availability in aquatic systems (estimated chlorophyll a 0.2 to 112 μg L-1). This dynamics was caused by increasing growth-rate of a relatively constant number of bacterial cells, maintaining the growth of an increasing number of protozoan cells. The results were supported by meta-analysis of field studies. Thus my results suggest that protozoa control the bacterial community by predation in nutrient-rich environments. In a field study in a natural productivity gradient (chlorophyll a 1.4 to 31 μg L-1) it was shown that intense selection pressure from protozoan predators, favours predation-resistant forms of bacteria. Thus, the abundance of predation-resistant bacteria increases with increasing nutrient availability in lakes. Furthermore, I could demonstrate that the bacterium Francisella tularensis, the causative agent of tularemia, was present in eutrophic aquatic systems in an emerging tularemia area. Isolated strains of the bacterium were found to be resistant to protozoan predation. In a microcosm study, using natural lake water, high nutrient availability in combination with high abundance of a small colourless flagellate predator favoured the occurrence of F. tularensis holarctica. In laboratory experiments F. tularensis strains were able to form biofilm at temperatures between 30-37°C, but not below 30°C. In conclusion, I have shown that the protozoan predation pressure on bacteria increases with increasing nutrient availability in aquatic systems. Predation-resistant forms of bacteria, such as F. tularensis are favoured in nutrient-rich environments. The complexity of the microbial food web and nutrient-richness of the water, influence the transmission of the pathogenic F. tularensis holarctica. However, over long periods of time, the bacterium survives in lake water but may lose its virulence. The temperature-regulated biofilm formation by F. tularensis may play a role in colonization of vectors or for colonization of hosts, rather than for survival in aquatic environments.

Access to clean drinking water is one of the most important resources for any society and its citizens. Without access to clean drinking water, health and living quality will be affected when pathogens will make people ill.In arid countries such as Ethiopia with seasonal drought, efforts to manage the water resources to last longer can be made by constructing dams and artificial irrigation systems. One example of this is the Koga dam in the Merawi region where a dam has been constructed to provide water for artificial irrigation. By irrigating an area one changes the hydrological conditions which might change the chemical composition of groundwater.This report aims to try and collect data that support the theory of the hydrological conductivity between irrigation water and groundwater in the area. Samples of groundwater and surface water was collected and compared to see if any conclu-sions supporting this theory could be made. Also general drinking water parameters were included such as presence of biological pathogens. The number of samples collected is on its own not enough to draw conclusions from but when combined with previous field work in the area and studying literature it supports the assumption of irrigation affecting the groundwater composition.
Tillgång till rent dricksvatten är en av de viktigaste resurserna för samhället såväl som varje enskild människa. Utan tillgång till rent dricksvatten kan hälsa och livs-kvalitet komma att påverkas av vattenburna patogener.I torra länder som Etiopien med periodisk torka har man gjort insatser för att hushålla med vattnet utöver regnperioderna. Ett exempel på detta är Kogadammen i Merawi, där en fördämning har konstruerats för att förse ett område med konst-bevattning. Genom bevattning ett område ändrar man de hydrologiska förhållanden som råder vilket gör att grundvattnets sammansättning kan komma att ändras.Denna rapport syftar till att försöka samla in data som stödjer teorin att konst-bevattningen i området påverkar grundvattnets sammansättning. Prover av grund-vatten och ytvatten samlades och jämfördes för att se om några slutsatser kunde dras. Också allmänna dricksvatten parametrar ingick såsom förekomsten av bio-logiska patogener. Antalet prover som tagits är ensamt inte tillräckligt för att dra slutsatser, men när de kombineras med data från tidigare fältarbete i området och litteraturstudier stödjer de antagandet om att konstbevattningen i området påverkar grundvattensammansättningen.

Lilium grayi (Gray’s Lily), a southern Appalachian endemic species, is threatened by a Lilium-specific fungal pathogen, Pseudocercosporella inconspicua. The disease is characterized by tan lesions that can cause early senescence, while also lowering seed production and viability. This project tested for P. inconspicua conidia and accessed health at nine locations. The disease was present and ubiquitous across the range of L. grayi. Through identification of P. inconspicua conidia in the field, L. superbum (Turk’s Cap Lily) was identified as an additional host, while L. michauxii (Michaux’s Lily) was disease-free. However, infection was inducible in both species. With the disease widespread in L. superbum and this species represented by many large populations, L. superbum may act as disease reservoir, further complicating the outlook for L. grayi. The disease should be considered an epidemic because of its impact on individual plants, its commonness within populations, and its ubiquity across the geographical range.

Ascochyta blight (synonym: blackspot) is a serious, globally distributed, primarily foliar disease of Pisum sativum L. (field pea). It is typically caused by a combination of three or four fungal species that can exist independently of each other, called a complex. Phoma koolunga, identified in 2009 in South Australia, is the most recent addition in the Ascochyta complex. Despite multiple international studies on Ascochyta blight of field pea, P. koolunga has not been reported anywhere else in the world and the origins of the pathogen, and if it occurs on other legume species remain unknown. This study provides new information on the host range of P. koolunga on leguminous plants in controlled growth room conditions. To establish a host range, disease incidence and severity were assessed on 41 legume species comprising Australian native, weed, crop, pasture legumes and wild type Pisum, Lathyrus and Vicia species, following inoculation using two isolates of P. koolunga. All legumes tested, except Cicer arietinum (chickpea), developed leaf lesions and some also had stem and tendril lesions. Incidence and severity differed significantly among species but not consistently between isolates. The ability of the P. koolunga isolates to cause lesions on a wide range of legumes, including natives, in controlled environment conditions, suggests that it has a broad host range in humid and mild temperature conditions conducive for disease. Although all 17 native species developed some degree of leaf spotting, seven were considered susceptible because disease incidence was greater than 55 percent. This research also details the isolation, identification and classification of Didymellaceae fungi causing leaf spots, collected from legumes during field studies undertaken to investigate a possible native origin of P. koolunga. Samples from plants with leaf spots were collected from field pea growing regions throughout New South Wales, South Australia and Victoria taken back to the laboratory and cultured. The resultant fungal isolates were identified based on both morphology and phylogenetic analyses of the internal transcribed spacer region and part of the RNA polymerase II subunit B gene region. P. koolunga was not detected on native, weed or pasture legumes that had leaf spot symptoms in any of the regions visited, and only one isolate was recovered from field pea in the entire 2-year collection period. However, six novel species from the family Didymellaceae were isolated from Australian native legumes, five were from South Australia and one from New South Wales. The locations are represented by four different Australian Indigenous Peoples native language groups. Representatives of those groups were approached to request permission to use a suitable Aboriginal word for species epithet and permissions granted. These fungi are described here as Didymella djirangnandiri from Swainsona galegifolia, Didymella kaurna from Gastrolobium celsianum, Neodidymelliopsis tinkyukuku from Hardenbergia violaceae, Nothophoma garlbiwalawarda from Senna artemisioides, Nothophoma naiawu, and Nothophoma ngayawang also from S. artemisioides. Additional findings from the field collections were the identification of three new host-pathogen associations for Australia. Didymella pinodes, the primary pathogen responsible for Ascochyta blight of field pea, was isolated from leaf spots on naturalised species Vicia cracca (tufted vetch) in New South Wales and on Senna artemisioides from five different locations across South Australia. The discovery that these legumes may serve as an inoculum reservoir hosts for D. pinodes has implications for epidemiology and management of Ascochyta blight of field pea because both commonly occur in field pea growing regions throughout South Australia. Didymella lethalis was isolated from naturalised species, Lathyrus tingitanus (tangier pea), growing in a creek bed located in a well-used recreation area in Adelaide, South Australia. Phylogenetic analyses indicated that P. koolunga has a close relationship with the recently named species Ascochyta boeremae and supports the re-naming of P. koolunga as Ascochyta. Confirmation of the correction in nomenclature to Ascochyta koolunga comb. nov. was achieved with PCR followed by sequencing at two additional loci, the partial gene regions of ß-tubulin and the partial large subunit nrDNA (LSU). In summary, the controlled growth room results revealing a wide legume host range, and field collection results yielding no isolations from legumes other than field pea, suggest that P. koolunga is unlikely to have originated as a pathogen of Australian native legumes and provides no evidence regarding possible origins.
Thesis (MPhil) -- University of Adelaide, School of Agriculture, Food and Wine, 2020

The increase of antibiotic resistance against antibiotics (AB) is an alarming phenomenon threatening the human well being and heading back to the pre-antibiotic era where many infectious diseases may become again untreatable with antibiotics. There is a strong correlation between AB use and occurrence of resistances which suggests anthropogenically-driven environments as reservoirs of antibiotic resistant bacteria (ARB). Among anthropogenically - driven environments, wastewater treatment plants (WWTPs), have been linked with the increased incidence of pathogens and ARB in freshwater ecosystems. Principal goal of the study was to evaluate the role of WWTPs as environmental reservoirs for antibiotic resistance and pathogenic bacteria. In this thesis, classical and molecular microbiology methods were applied to analyse resistance levels of bacterial communities from wastewater and wastewater-polluted environments at different geographical locations of developed (German and Switzerland) and developing (Nigeria) countries. Additionally, a novel approach which makes use of a combination of quantitative genomics, Next Generation Sequencing and drug-related health data was applied to quantitatively detect antibiotic resistance genes (ARG) in wastewater and assess their seasonal dynamics. The relative abundance of ARG was not reduced by the WWTPs in the treated effluent. Effluents were responsible for significantly high levels of ARB and ARG in the receiving environment because capable of introducing and/or selecting ARB carrying ARG on genetic mobile elements. The ARG levels differed between seasons independently from the water sanitation. High ARG levels were displayed in autumn and winter in coincidence with the higher uptake of antibiotics by the outpatients of the municipality.Contrary to the ARG, the abundance of bacteria was reduced by WWTPs processes in the effluent of developed countries. The WWTPs were also responsible for the changes of the microbial community from the wastewater to the effluent. Contrary to developed countries, the poor treatment of wastewater in Nigeria facilitated the spread of multi-drug resistant pathogens in the freshwater ecosystem. These bacteria were also carriers of clinically relevant ARG contributing to the accumulation of multiresistant pathogens in the environment. All in all, this thesis shows that well established WWTP technologies are not capable to prevent or reduce the abundance of ARG in the freshwater ecosystem and poorly treated wastewater enriches the environmental reservoirs of ARG. Antibiotic resistance can spread across taxonomically distant bacteria and therefore explain the strong dispersal of ARG in wastewater effluents. These results show that antibiotic resistances are also ubiquitous in the freshwater environment and that anthropogenically - driven environments determine the incidence of antibiotic resistance. As for the clinic, tackling the problem of antibiotic resistance in the environment is fundamental. Without any action, the environmental reservoirs of resistance will increase and therapeutic failure in the clinic will irreversibly compromise the biggest progress in medicine of the 20th century.

Submitted in partial compliance with the requirements for a Master Degree in Technology: Chiropractic at the Durban University of Technology, 2009.
Background: Research has indicated the majority of bacteria on chiropractic adjustment beds (beds), can persist on dry inanimate surfaces for months. Thus, insufficient disinfection procedures create continuous sources of pathogens endangering patients and healthcare workers alike. This research study aimed to assess the beds as reservoirs for micro-organisms, at a chiropractic teaching clinic (clinic) in South Africa. Method: A selection of samples obtained from the headrests and armrests of the beds were serially diluted, plated in duplicate (using the spread plate technique) and incubated for 24-48 hours at 37°C. After inspection for the presence of micro-organisms, those present were enumerated to determine their quantities, the microbial build-up throughout the day, as well as the degree of the transmission from the patients to the beds during treatment. The incidence of the micro-organisms was established, along with their identities, using microscopic and macroscopic characteristics. These micro-organisms were also used to assess the efficacy of the disinfectant currently in use by the clinic. Results: Microbial growth was present on 89.4% of the beds sampled. The quantities of the micro-organisms increased significantly (p=0,027) from 7:30 am to 16:30 pm, with the median increasing from 25 colony forming units (cfu) / cm2 to 714 792 cfu/ cm2. The microbial build-up was highly significant (p<0.001), with a median of 346 cfu/ cm2 at 7:30 am and 10:30 am; increasing to 162 291 cfu/ cm2 by 13:30 pm and 250 million cfu/ cm2 by 16:30 pm. There was also a significant increase (p<0.001) in the quantity of micro-organisms during treatment with a median of 0 cfu/ cm2 before treatment that rose to 23 479 cfu/cm2 after treatment, indicating that the micro-organisms present on the beds were being deposited by the patient`s skin during the treatment. The most prevalent micro-organisms identified were Staphylococci and Serratia, with an average of 59% and 40% of colonies; while Micrococci and Bacilli were relatively uncommon. No growth was evident after 5 minutes of exposure to the disinfectant during the growth inhibition test. For the Kirby Bauer test, the average size of the zone of inhibition increased as the dilution decreased. The disinfectant is effective but more so against the Gram-positive than the Gram-negative bacteria. The disinfectant was 5,0, 5,5 and 5,6 times more effective than phenol in eradicating Staphylococci, Serratia and Bacilli, respectively. Conclusions and Recommendations: This study showed that micro-organisms were present on the beds. Staphylococci and Serratia have been implicated in many healthcare associated infections. The present disinfectant is effective, but should be used in between every patient. A different or additional disinfectant that is more effective against the Gram-negative bacteria should be considered for future use.

MSc (Microbiology)
Department of Microbiology
Background: Escherichia coli is a facultative anaerobic bacterium that forms part of the gut microbiota. It is used as an indicator that confirms recent faecal contamination. E. coli have been identified amongst the pathogens that are mostly responsible for moderate to severe diarrheal outbreaks in the low and middle-income countries. With South Africa facing an issue in water scarcity, issues concern poor sanitation and hygiene practices results in serious public health problems and allows E. coli to be transmitted from infected human or animal faeces to a new susceptible host using environmental reservoirs such as soil, water, hands as the transmission pathway. Objective: The primary objective of the study was to characterize E. coli strains from rural communities of Vhembe district, Limpopo, South Africa. Methodology: Households of 7 villages in the Vhembe district were randomly selected. A total of 81 households (HHs) were part of the study. In each household, a structured questionnaire was used to background information on WASH practices. Samples taken from each HH included toilet seat swabs, floor swabs, child and mother handwash samples, stored water samples and running tap water samples. A total of 399 samples were analysed using Colilert® Quanti-trays®/2000 method to detect the presence of Escherichia coli. Positive E. coli samples were further identified using multiplex polymerase chain reaction (m-PCR) to determine the pathogenic strains of E. coli. Transmission pathways were established using identified strains. Results: Data from the structured questionnaires showed common problems of availability of running tap water; lack of provision of sanitation; open practice on defaecation and very little hand hygiene practices. A total of 91 (22.81%) samples tested positive for E. coli with the Colilert® Quanti-trays®/2000 method. The mothers’ handwash samples had the most E. coli prevalence followed by stored water samples. The most prevalent E. coli pathotype was EPEC with the virulence gene eae. Atypical EPEC (60.44%) outnumbered the typical EPEC (5.49%). The pathotype ETEC was detected in 41.76% samples and EHEC in 9.89% samples. Transmission pathway was observed from the different households; with eae gene (aEPEC) being the most detected from samples looking at the LT gene (ETEC). v | P a g e Discussion: All 7 villages are facing common issues such as lacking running water, poor sanitation and improper hand hygiene practices. The mothers were the most contaminated and it was observed that its due to the daily activities that they perform around the house. It is of importance for them to practice proper hand hygiene to prevent transmission of pathogenic E. coli to the children via direct or indirect transmission route. The pathogenic E. coli was detected from all different samples collected from the households including the floor and toilet seat samples. EPEC was detected the most, and studies have shown that this strain is known to cause diarrheal infections in young children from developing countries. Conclusion: The members of the study village households were aware of the WASH services and its importance. However, proper implementation into their day-to-day life is lacking due to the high number of TC and E. coli detected from handwash samples and stored water samples from the households. Recommendation: Appropriate WASH strategies should be established to ensure good health at the village households. Further studies should be done to check possible transmission pathways from more village households.
NRF