Epidemiology and comparative analysis of Yersinia in Ireland

Yersiniosis is an acute or chronic enteric zoonosis caused by enteropathogenic Yersinia species. Although yersiniosis is predominantly associated with gastroenteric forms of infection, extraintestinal forms are often reported from the elderly or patients with predisposing factors. Yersiniosis is often reported in countries with cold and mild climates (Northern and Central Europe, New Zealand and North of Russian Federation). The Irish Health Protection Surveillance Centre (HPSC) currently records only 3-7 notified cases of yersiniosis per year. At the same time pathogenic Yersinia enterocolitica is recovered from pigs (main source of pathogenic Y. enterocolitica) at the levels similar to that observed in Yersinia endemic countries. Introduction of Yersinia selective culture procedures may increase Yersinia isolation rates. To establish whether the small number of notifications of human disease was an underestimate due to lack of specific selective culture for Yersinia we carried out a prospective culture study of faecal samples from outpatients with diarrhoea, with additional culture of appendix and throat swabs. Higher levels of anti-Yersinia seroprevalence than yersiniosis notification rates in endemic countries suggests that most yersiniosis cases are unrecognised by culture. Subsequently, in addition to a prospective culture study of clinical specimens, we carried out serological screening of Irish blood donors and environmental screening of human sewage. Pathogenic Yersinia strains were not isolated from 1,189 faeces samples, nor from 297 throat swabs, or 23 appendix swabs. This suggested that current low notification rates in Ireland are not due to the lack of specific Yersinia culture procedures. Molecular screening detected a wider variety of Y. enterocolitica-specific targets in pig slurry than in human sewage. A serological survey for antibodies against Yersinia YOP (Yersinia Outer Proteins) proteins in Irish blood donors found antibodies in 25%, with an age-related trend to increased seropositivity, compatible with the hypothesis that yersiniosis may have been more prevalent in Ireland in the recent past. Y. enterocolitica is a heterogeneous group of microorganisms that comprises strains with different degree of pathogenicity. Although non-pathogenic Y. enterocolitica lack conventional virulence factors, these strains can be isolated from patients with diarrhoea. Insecticidal Toxin Complex (ITC) and Cytolethal Distending Toxins can potentially contribute to the virulence of non-pathogenic Y. enterocolitica in the absence of other virulence factors. We compared distribution of ITC and CDT loci among pathogenic and non-pathogenic Y. enterocolitica. Additionally, to demonstrate potential pathogenicity of non-pathogenic Y. enterocolitica we compared their virulence towards Galleria mellonella larvae (a non-mammalian model of human bacterial infections) with the virulence of highly and mildly pathogenic Y. enterocolitica strains. Surprisingly, virulence of pathogenic and non-pathogenic Y. enterocolitica in Galleria mellonella larvae observed at 37°C did not correlate with their pathogenic potential towards humans. Comparative phylogenomic analysis detects predicted coding sequences (CDSs) that define host-pathogen interactions and hence providing insights into molecular evolution of bacterial virulence. Comparative phylogenomic analysis of microarray data generated in Y. enterocolitica strains isolated in the Great Britain from humans with diarrhoea and domestic animals revealed high genetic heterogeneity of these species. Because of the extensive human, animal and food exchanges between the UK and Ireland the objective of this study was to gain further insight into genetic heterogeneity and relationships among clinical and non-clinical Y. enterocolitica strains of various pathogenic potential isolated in Ireland and Great Britain. No evidence of direct transfer of strains between the two countries was found.

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.

Immunomodulatory effects exerted by Lactobacillus salivarius strains on innate immune cells

Despite increased application of commensal bacteria for attempting to improve the symptoms of a variety of inflammatory conditions, including inflammatory bowel diseases, diarrhoea and irritable bowel syndrome, therapeutic approaches that involve live bacteria are hampered by a limited understanding of bacterium-host interactions. Lactobacilli are natural inhabitants of the mammalian gastrointestinal tract and many lactobacilli are regarded as probiotics meaning that they exert a beneficial influence on the health status of their consumers. Modulation of immune responses is a plausible mechanism underlying these beneficial effects. The aim of this thesis was to investigate the effect of 33 Lactobacillus salivarius strains on the production of inflammatory cytokines from a variety of human and mouse immune cells. Induction of immune responses in vitro was shown to be bacterial- and mouse strain-dependent, cell type-dependent, blood donor-dependent and bacterial cell number-dependent. Collectively, these data suggest the importance of a case-by-case selection of candidate strains for their potential therapeutic application. Toll-like receptors (TLRs) recognize microbe-associated molecular patterns (MAMPs) and play a critical role in shaping microbial-specific innate and adaptive immune responses. Following ligand engagement, TLRs trigger a complex network of signalling that culminate in the production of inflammatory mediators. The investigation of the molecular mechanisms underlying the Lb. salivarius-host interaction resulted in the identification of a novel role for TLR2 in negatively regulating TLR4 signalling originated from subcellular compartments within macrophages. Notably, sustained activation of JAK/STAT cascade and M1-signature genes in TLR2-/- macrophages was ablated by selective TLR4 and JAK inhibitors and by absence of TLR4 in TLR2/4-/- cells. In addition, other negative regulators of TLR signalling triggered by Lb. salivarius strains were found to be the adapter molecules TIRAP and TRIF. Understanding negative regulation of TLR signalling may pave the way for the development of novel therapeutics to limit inflammation in multiple diseases.