No description available.

The etiology of viral diarrhoea in children in the Kingdom of Saudi Arabia (KSA) is incompletely characterized. Available data suggest that the causative agents are found at approximately similar frequencies here as elsewhere. However KSA is not a typical country; the lack of rivers and lakes may affect the paths open for virus spread in the Kingdom and the relatively high year-round temperature may limit virus survival in the environment. Sewage is disposed of to sea after treatment, and although virus is found in seawater, exposure via recreational use is limited those living along the coast. Virus is also found in seafood which may aid transmission inland but drinking water is supplied by desalination, a process that would effectively inactivate most viruses. Thus the bulk of viral transmission must be presumably via person to person or food-borne spread inland. Secondly, KSA plays host to many millions of visitors each year who flock to the country from all over the world in a short time period; the Hajj or annual pilgrimage to Makkah. This influx of persons offers opportunity both for the introduction of new strains of viruses and also for person to person transmission in these crowded venues. Consequently, there may be subtle differences in the manner of circulation of these viruses in KSA. This project set out to study the epidemiology of diarrhea viruses in pediatric populations. The study addressed initially rotavirus, enteric adenovirus and astrovirus but was later expanded to include norovirus. Viruses were sought in faecal specimens and characterized for genotype using molecular methods for the first time in KSA. The survey focused on three locations; Jeddah, Makkah and Riyadh. During the Hajj the chief population fluxes are via Jeddah to Makkah. One thousand samples were obtained from children (aged six years or less) presenting with diarrhoea and thus representing community acquired rather than nosocomial infections. Human rotavirus (HRV) group A was detected in 6% (60/ 1000). By RT-PCRG1 was the predominant VP7 genotype (36/58, 62%), followed by the unique G9 (19/58, 33%). The other HRV genotypes found, 02 and 03, were less common at 1.2% (1/58) and 3.4% (2/58), respectively. P-type determination was also performed by RT-PCR and P[8] was clearly the most common (45/56, 80.3%). Overall 01P[8] was the most common, accounting for 60.7% of total samples positive for both genotypes. Rarer types 09P[4] (2/56, 3.57%) and 09P[6] (6/56, 10.7%) were identified for the first time in KSA. Enteric adenovirus (EAdV) was evident in 14/1000 pediatric stool samples (1.4%) by ELISA and all were also positive by RT- PCR. Enteric types 40 and 41 were distinguished using RT- PCR and RFLP; five samples were positive for EAdV-40 and 7 for EAdV-41. One sample showed a mixed infection of both 40 and 41. A single sample was eventually typed as type 31 by Sequencing. Human astrovirus (HAstV) was found in 1.9% (19/1000 samples). All but one was identified as type 8. This was a surprising finding since these infections were not nosocomial but independent, community-acquired cases. The remaining sample could not be amplified. Human caliciviruses are among the most common causes of gastrointestinal and there are no data for these viruses in Saudi Arabia. A smaller panel of 253 stool samples was tested for norovirus by ELISA and 9/253 were found positive (3.5%). Overall, most infections with rotavirus were detected in children of 1 year of age or less (P=0.047), and in children of 3 year of age or less with astrovirus likewise, in adenovirus most of the infections were detected in children of 2 year of age or less with P-Value of= 0.05, and 0.01 respectively. All viruses were distributed equally between males and females. HRV was the most common diarrhoeal virus detected followed by norovirus, although the rotavirus incidence found here was lower than that reported in previous studies. Infections showed a peak shortly after the Hajj during the study period. Novel HRV were found, with the first detection of the emergent G9 serotype and some combinations of G and P types new in KSA. Adenovirus 31 was reported for the first time and we found an unexpectedly high incidence of astrovirus serotype 8.

Unsafe drinking water, together with poor hygiene and sanitation, are the main contributors to diarrhoeal disease, a leading cause of mortality and morbidity especially among young children in low-income settings. While the Millennium Development Goals seek to halve the portion of the population without access to safe water by 2015, the high cost of piped-in supplies has led the World Health Organization to call for alternative approaches, including household water treatment. This thesis describes the results of certain research concerning the effectiveness, cost-effectiveness and field implementation of household water treatment for the prevention of diarrhoeal disease. In a systematic review of interventions to improve water quality for the prevention of endemic diarrhoea, 30 studies covering 38 intervention trials were identified and meta- analyzed. The studies varied considerably in design, setting, type of intervention and point of intervention. The evidence suggests that in settings with sufficient water quantity, interventions to improve the microbiological quality of drinking water are effective in preventing diarrhoea, and that household-based interventions are about twice as effective as conventional improvements at the water source. The costs of such water quality interventions was compiled and combined with the effectiveness data from the systematic review to determine the cost-effectiveness of interventions to improve water quality. In most settings, household water treatment meets established criteria for "highly cost effective" health interventions. In a six-month pilot programme in Colombia, household-based water filters were associated with a substantial improvement in microbial water quality and a 60% reduction in the prevalence of diarrhoea (OR = 0.40,95% CI = 0.25,0.63, P<0.0001). In a study to assess the drinking water response to the Indian Ocean tsunami, household water treatment had only a limited role, suggesting the need to consider under what circumstances such interventions can contribute to the delivery of safe drinking water in the immediate aftermath of an emergency. The thesis concludes with some thoughts on the challenge of implementing household water treatment and the need for further research.

No description available.

PhD (Microbiology) / Department of Microbiology / Diarrhoea is still a major problem worldwide. Enteric pathogens such as Enteroaggregative E. coli (EAEC), Enteropathogenic E. coli (EPEC) and Enterotoxigenic E. coli (ETEC) have been reported to cause diarrhoea in children under the age of 5 years. The incidences of these pathogens are due to factors such as poor water quality, sanitation and hygiene practices. Infections with these pathogens result in diarrhoea and have been reported to result in severe disease outcomes more especially in children under 2 years of age. EPEC infections have been well studied using in vitro analyses, with studies highlighting the adherence traits, proteins and virulence genes involved in pathogenesis and inflammatory responses. EPEC is characterized by localized adherence with microcolony formation at the site of infection. In vivo studies have reported on human EPEC infection. However, the current animal models have not been able to replicate clinical outcomes (such as diarrhoea and weigh loss) of EPEC infection similar to humans. Therefore, there is still a need for a suitable small animal model that mimic clinical outcomes of human EPEC infections in vivo. Children living in poor environmental conditions are more susceptible to diarrhoeal pathogens. Furthermore, the incidences of children being exposed to co-infections (more than one pathogen at the same time) is relatively high. The EAEC/EPEC (A/P) and EPEC/ETEC (P/T) co-infections have been increasingly detected in children with and without diarrhoea. It has been suggested that patients infected with these co-infections might result in severe disease outcome than those infected with single pathogens. Pathogens are constantly evolving and the microbe-microbe interaction in the host can result in these pathogens competing for the same niche and thus result in increased virulence. Interaction of co-infections can lead to increased inflammatory responses thus affecting the infected host. The first objective of this study was to develop an EPEC murine model using weaned C57BL/6 mice that have been pretreated with antibiotic cocktail. Mice were orally infected with wild-type (WT) typical EPEC, bfp- and escN mutant strains. The WT had transient weight loss and wet stools with mucous; and the bfp- infected mice also had transient weight loss and bloody stool appearance. Increase in inflammatory biomarkers MPO, LCN-2, CRP, IL-6 and SAA were observed in the WT and bfp- infected mice. The mice infected with escN mutant did not exhibit any weight changes and the stools were similar to the uninfected mice. Furthermore, no inflammatory biomarkers were observed in mice infected with the escN mutant. Metabolic perturbations were observed in WT EPEC infected mice at day 3 post infection with the TCA cycle metabolites (reduced succinate, citrate, fumarate, cis-aconitate) being excreted at lower quantities indicating that the energy production in the infected mice was greatly affected. The second objective of this study was to determine the interaction between the P/T coinfections using in vitro and in vivo analyses. In vitro, human colorectal tumour 8 (HCT-8) cells were infected with single strains of ETEC, EPEC and both the pathogens and incubated for 3 hours. After infection the cells were analysed for bacterial adherence using real-time PCR. The single strains adhered at the same rate similar to the P/T coinfected cells. IL-8, as a marker of inflammatory response, was measured using ELISA. The results indicated that the P/T co-infected cells had a significant increase in IL-8 response higher than the single infections. The P/T co-infections were further analysed in vivo using the EPEC murine model developed in this study. Interestingly, mice infected with P/T co-infections developed severe diarrhoea accompanied with significant increased weight loss and some mice died during the 3-day infection period. The inflammatory responses MPO, LCN-2 and SAA were higher in the co-infected mice indicating a synergistic effect. The bfp and eltA virulence genes were significantly increased in the P/T co-infections. The third objective of this study was to determine the interaction between A/P coinfections using in vitro and in vivo analyses. HeLa cells and HCT-8 cells were infected with EAEC, EPEC and both the pathogens at the same time in order to determine adherence and inflammatory responses. EAEC adherence was higher than EPEC and A/P co-infections adherence. A/P co-infections did not have increased IL-8 response in HCT-8 cells when compared to EAEC alone. The virulence genes involved in EPEC adherence and Type 3 Secretion System (bfp, eae, tir, ler, per, espB and espA) were significantly reduced in A/P co-infected cells. An interesting adherence trait was observed between the A/P co-infections in HeLA cells, EAEC was found to adhere around EPEC altering the localized adherence pattern. The A/P co-infections were further analysed using the EPEC murine model developed in this study. The A/P infected mice had diminished weight changes and EAEC shedding was enhanced when EPEC was present. Faecal inflammatory biomarkers MPO and LCN-2 in A/P infected mice did not have any additive effect. The findings of this study contributed significantly to the knowledge of human EPEC infection in weaned C57BL/6 mice, highlighting clinical outcomes, inflammatory responses and metabolic perturbations. Furthermore, this study also highlighted the interaction of P/T and A/P co-infections using in vitro and in vivo analyses in order to determine the disease severity and outcomes. It was observed in this study that coinfections can result in either synergistic or antagonistic effects. Further studies are therefore, required in order to understand the underlying mechanisms that are involved during co-infections and this can further assist in the development of therapeutic interventions. / NRF