Molecular analysis of virulence mechanisms associated with adherent-invasive Escherichia coli (AIEC)

Crohn's Disease (CD) is a chronic inflammatory bowel disease of unknown etiology. Recent work has shown that a new pathotype of Escherichia coli, Adherent Invasive E. coli (AIEC) may be associated with CD. AIEC has been shown to adhere to and invade epithelial cells and to replicate within macrophages (together this is called the AIEC phenotype). In this thesis, the AIEC phenotype of 84 E. coli strains were determined in order to identify the prevalence of this phenotype within the E. coli genus. This study showed that a significant proportion of E. coli strains (approx. 5%) are capable of adhering to and invading epithelial cells and undergoing intramacrophage replication. Moreover, the results presented in this study indicate a correlation between survival in macrophage and resistance to grazing by amoeba supporting the coincidental evolution hypothesis that resistance to amoebae could be a driving force in the evolution of pathogenicity in some bacteria, such as AIEC. In addition, this study has identified an important regulatory role for the CpxA/R two component system (TCS) in the invasive abilities of AIEC HM605, a colonic mucosa-associated CD isolate. A mutation in cpxR was shown to be defective in the invasion of epithelial cells and this defect was shown to be independent of motility or the expression of Type 1 fimbriae, factors that have been shown to be involved in the invasion of another strain of AIEC, isolated from a patient with ileal CD, called LF82. The CpxA/R TCS responds to disturbances in the cell envelope and has been implicated in the virulence of a number of Gram negative pathogens. In this study it is shown that the CpxA/R TCS regulates the expression of a potentially novel invasin called SinH. SinH is found in a number of invasive strains of E. coli and Salmonella. Moreover work presented here shows that a critical mechanism underpinning AIEC persistence in macrophages is the repair of DNA bases damaged by macrophage oxidants. Together these findings provide evidence to suggest that AIEC are a diverse group of E. coli and possess diverse molecular mechanisms and virulence factors that contribute to the AIEC phenotype. In addition, AIEC may have gone through different evolutionary histories acquiring various molecular mechanisms ultimately culminating in the AIEC phenotype. The gastrointestinal (GI) tract harbors a diverse microbiota; most are symbiotic or commensal however some bacteria have the potential to cause disease (pathobiont). The work presented here provides evidence to support the model that AIEC are pathobionts. AIEC strains can be carried as commensals in healthy guts however, when the intestinal homeostasis is disrupted, such as in the compromised gut of CD patients, AIEC may behave as opportunistic pathogens and cause and/or contribute to disease by driving intestinal inflammation.

Symptom burden in individuals with inflammatory bowel disease: a mixed methods study

To investigate the symptom burden experiences of individuals with inflammatory bowel disease (IBD). An explanatory sequential mixed methods study was conducted. A cross-sectional, correlational survey was first undertaken. Symptom burden was measured using a modified disease specific version of the Memorial Symptom Assessment Scale, which was administered to a consecutive sample of individuals with IBD (n = 247) at an IBD Outpatients department in one urban teaching hospital in Ireland. Disease activity was determined using clinical disease activity indices, which were completed by the consulting physician. A sequential qualitative, descriptive study was then conducted aimed at explaining noteworthy quantitative findings. A criterion-related purposeful sample of seven participants from the quantitative study was recruited. Semi-structured face to face interviews were conducted using an interview guide and data were analysed using content analysis. Findings revealed that participants experienced a median of 10 symptoms during the last week, however as many as 16 symptoms were experienced during active disease. The most burdensome symptoms were lack of energy, bowel urgency, diarrhoea, feeling bloated, flatulence and worry. Total symptom burden was found to be low with a mean score of 0.56 identified out of a possible range from 0 to 4. Participants with active disease (M = 0.81, SD = 0.48; n = 68) had almost double mean total symptom burden scores than participants with inactive disease (M = 0.46, SD = 0.43; n = 166) (p < 0.001). Mean total psychological symptom burden was found to be significantly greater than mean total physical symptom burden (rho = 0.73, n = 247, p < 0.001). Self-reported disease control, gender, number of flare ups in the last two years, and smoking status was found to be significant predictors of total symptom burden, with self-reported disease control identified as the strongest predictor. Qualitative data revealed tiredness, pain, bowel symptoms, worry and fear as being burdensome. Furthermore, symptom burden experiences were described in terms of its impact on restricting aspects of daily activities, which accumulated into restrictions on general life events. Psychological symptom burden was revealed as more problematic than physical symptom burden due to its constant nature, with physical and psychological symptoms described to occur in a cyclical manner. Participants revealed that disease control was evaluated not only in terms of symptoms, but also in terms of their abilities to control the impact of symptoms on their lives. This study highlights the considerable number of symptoms and the most burdensome symptoms experienced by individuals with IBD, both during active and inactive disease. This study has important implications on symptom assessment in terms of the need to encompass both physical and psychological symptoms. In addition, greater attention needs to be placed on psychological aspects of IBD care.

Cancer associated malnutrition: prevalence of cachexia, sarcopenia and impact on treatment outcomes, survival and health related quality of life

Malnutrition, sarcopenia and cancer cachexia (CC) are prevalent among cancer patients and can have detrimental effects on clinical outcomes such as quality of life (QoL) and overall survival. Cachexia is associated with lower tolerance for chemotherapy, which limits the total dose that can be delivered, the number of symptomatic responses and any survival advantage that might be accrued. Moreover, for the majority who do not respond, cachexia may be exacerbated by systemic chemotherapy, thus increasing the net symptom burden experienced by patients. The multitude of interactions between cancer location, treatments, nutritional status and QoL has never been thoroughly explored in an Irish cancer cohort. The objectives of this thesis were to further understand nutritional status, especially body composition in ambulatory cancer patients and determine the relationship between nutritional status using different assessment criteria and QoL, chemotherapy toxicity and survival among cancer patients undergoing chemotherapy. Results aimed to identify baseline factors that may be predictive of poor outcome, toxicities to chemotherapy and disease-free and overall survival. This thesis broadly divides into two sections. The first section (Chapters 3 & 4) focuses on improving our knowledge of the nutritional status of Irish cancer outpatients using a cross sectional study design. A study of 517 patients referred for chemotherapy was conducted using computed tomography (CT) imaging (body composition) and a survey that documented oncologic data, weight loss (WL) data and QoL data. We revealed that a significant proportion of Irish cancer patients undergoing chemotherapy experience unintentional WL over the previous 6 months (62%), sarcopenia (45%) and CC (43%), and the distribution of WL and nutritional risk were associated with site of primary tumour and treatment intent. Patients that had sarcopenia, nutritional risk, or CC had significantly reduced functional abilities, more symptoms and adverse global QoL. In the second section of this thesis (Chapters 5 & 6) the potential link between developing toxicity to antineoplastic regimens in patients with sarcopenia was conducted by way of retrospective studies. A retrospective serial CT analysis defined the prevalence of sarcopenia in patients with metastatic renal cell carcinoma (mRCC) and metastatic castrate resistant prostate cancer (mCRPC), which was then correlated with dose limiting toxicities of sunitinib and docetaxel respectively. Sarcopenia was prevalent in patients with mRCC and mCRPC, was an occult condition in patients with normal/high BMI, was associated with less treatment days, was a significant predictor of DLT in patients receiving sunitinib and a significant predictor of neutropenia and neurosensory toxicities in patients receiving docetaxel. This thesis attempted to address the underlying research deficiencies in Irish oncology nutritional data at national level. The findings from this thesis have implications for the planning of cancer care interventions and indicate that further research is required to improve nutritional screening, in particular for CC and sarcopenia, in the hope that timely intervention can improve both patient-centered and oncologic outcomes.