H J O'Connor

Trinity College Dublin, Dublin, L, Ireland

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Publications (94)664.85 Total impact

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    ABSTRACT: Eradication rates of first-line triple therapy for Helicobacter pylori infection have fallen in the recent years. The main reasons for treatment failure are poor compliance due to complicated treatment regimens and the emergence of antibiotic-resistant strains of H. pylori. Treatment failure is a cause for concern with regard to the complications of H. pylori infection, which include gastric and peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma. This review describes considerations for optimizing standard first-line triple therapy, as well as alternatives to the standard first-line treatment, such as bismuth quadruple therapy, sequential therapy, concomitant therapy and hybrid therapy. Studies using levofloxacin-based and rifabutin-based regimens for the treatment of multiresistant infections have also been reviewed. The current most up-to-date systematic reviews and meta-analyses comparing the efficacy of these treatments have been discussed, in light of the recent antimicrobial susceptibility testing data, regional antibiotic resistance rates and the Maastricht IV guidelines on the management of H. pylori infection.
    European journal of gastroenterology & hepatology. 06/2014;
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    ABSTRACT: BACKGROUND:: Ileal intubation is being increasingly performed at colonoscopy and has in turn lead to an increasingly recognized subgroup of patients-those with mild terminal ileal inflammation, an entity that we have coined isolated active ileitis (IAI). The aims of this study were to define the natural history of IAI and determine if IAI shares a similar genetic and serologic profile with Crohn's disease (CD). METHODS:: Patients with IAI were identified from our institution's histopathology and endoscopy databases. Cases attended for repeat colonoscopy and blood were analyzed for the expression of antineutrophil cytoplasmic antibody, anti-OmpC, anti-Saccharomyces cerevisiae antigen (ASCA) IgA, ASCA IgG, and anti-CBir antibodies and NOD2 genotyping. Age and sex-matched healthy controls, CD, and UC cases were also recruited. RESULTS:: Sixty-three patients with IAI were recruited. There was no significant difference in the prevalence of antibodies between IAI cases and healthy controls for antineutrophil cytoplasmic antibody, OmpC, ASCA IgA, or ASCA IgG. The presence of all 5 antibodies was significantly higher in the CD group than the IAI group, P < 0.05. There were 28.6% of CD cases that carried one or more NOD2 variants, compared to 26.2% of the IAI cohort and 6.1% of healthy controls. Forty-three cases underwent follow-up ileocolonoscopy. Six of 43 cases (14%) had definite CD. CONCLUSIONS:: A majority of IAI cases developed persistent symptoms and terminal ileal abnormalities; however, only 14% developed classical, histological, or radiological features of CD. Although patients with IAI have a low level of seropositivity, similar to healthy controls, they do share an excess of NOD2 mutations with CD cases.
    Inflammatory Bowel Diseases 06/2013; · 5.12 Impact Factor
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    ABSTRACT: INTRODUCTION: Helicobacter pylori eradication rates using conventional triple therapies are falling, making viable second-line and rescue regimens necessary. Levofloxacin, tetracycline and rifabutin are three efficacious antibiotics for rescue therapy. AIM: We aimed to assess the resistance rates for H. pylori against these antibiotics in an Irish cohort. METHODS: Gastric biopsies were collected from 85 patients infected with H. pylori (mean age 46 years) in the Adelaide and Meath Hospital, Dublin in 2008 and 2009. Susceptibility to antibiotics was tested using the Etest. Clinical information was obtained from endoscopy reports and chart review. RESULTS: 50.6 % of patients were females. Mean age was 47 years. Ten had prior attempts at eradication therapy with amoxicillin-clarithromycin-PPI, two had levofloxacin-based second-line therapy. 11.7 % [95 % CI (6.5-20.3 %)] (N = 10) had strains resistant to levofloxacin. There were no strains resistant to rifabutin or tetracycline. Levofloxacin resistance in the under 45 age group was 2.6 % (1/38) compared to 19.1 % (9/47) of above 45 age group (p = 0.02). DISCUSSION: The levofloxacin rates illustrated in this study are relatively low by European standards and in line with other studies from the United Kingdom and Germany, with younger patients having very low levels of resistance. Levofloxacin, tetracycline and rifabutin are all valid options for H. pylori eradication in Irish patients but the importance of compliance cannot be underestimated.
    Irish Journal of Medical Science 04/2013; · 0.51 Impact Factor
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    ABSTRACT: We present a salutary lesson learned from three cases with significant complications that followed anorectal intervention in the presence of radiation proctitis due to prior radiotherapy for adenocarcinoma of the prostate. After apparent routine rubber band ligation for painful haemorrhoids, one patient developed a colo-cutaneous fistula. Following laser coagulation for radiation proctitis, one patient required a pelvic exenteration for a fistula, while another developed a rectal stenosis. Those diagnosing and treating colonic conditions should be mindful of the increased prevalence of patients who have had radiotherapy for prostate cancer and the potential for complications in treating these patients.
    Irish medical journal 03/2012; 105(3):91-3. · 0.51 Impact Factor
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    ABSTRACT: Eosinophilic oesophagitis is a recently recognized oesophageal disorder characterized by a combination of clinical and endoscopic features as well as the histological finding on oesophageal biopsy of greater than 15 eosinophils per high powered field. Recent reports suggest eosinophilic oesophagitis is increasing in incidence and this increase cannot be fully explained by increased recognition of the disorder. The aim of this retrospective study was to assess the incidence of eosinophilic oesophagitis within the catchment area of a tertiary referral hospital in southwest Dublin, Ireland. The histopathology database at the Adelaide and Meath Hospital was used to identify all oesophageal biopsies obtained between January 2000 and July 2008 reported to show evidence of oesophagitis. Biopsy samples with greater than 15 eosinophils per high powered field in at least two fields were highlighted as possible eosinophilic oesophagitis. The oesophageal biopsies of patients identified in this way were reviewed by a histopathologist with a special expertise in gastroenterology for features suggestive of eosinophilic oesophagitis. Twenty-five thousand three hundred and sixty-five upper gastrointestinal endoscopies were performed between January 2000 and July 2008. A total of 11 072 sets of oesophageal biopsies were taken and 1364 (12.3%) of these revealed evidence of oesophagitis. Only 13 (0.1%) patients had oesophageal biopsies showing greater than 15 eosinophils per high powered field. The median age of this patient group was 23 years (interquartile range 10.5-50.5 years), with 46% of patients under 18 years at the time of diagnosis. The male to female ratio was 5.5 : 1 compared with 1.1 : 1 in the oesophagitis group as a whole, (P=0.002). There was no significant association between endoscopic findings or presenting complaints and the average number of eosinophils per high powered field. The average number of biopsies taken in patients with endoscopic findings suggestive of eosinophilic oesophagitis was 3.75 compared with 1 in patients without those features, (P=0.01). Our findings suggest that eosinophilic oesophagitis is a rare disorder predominantly affecting young men.
    European journal of gastroenterology & hepatology 09/2011; 23(12):1116-21. · 1.66 Impact Factor
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    Alaa Alakkari, Angelo Zullo, Humphrey J O'Connor
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    ABSTRACT: Research published over the past year has documented the continued decline of Helicobacter pylori-related peptic ulcer disease and increased recognition of non-H. pylori, non-steroidal anti-inflammatory drugs ulcer disease--idiopathic ulcers. Despite reduced prevalence of uncomplicated PUD, rates of ulcer complications and associated mortality remain stubbornly high. The role of H. pylori in functional dyspepsia is unclear, with some authors considering H. pylori-associated nonulcer dyspepsia a distinct organic entity. There is increasing acceptance of an inverse relationship between H. pylori and gastroesophageal reflux disease (GERD), but little understanding of how GERD might be more common/severe in H. pylori-negative subjects. Research has focused on factors such as different H. pylori phenotypes, weight gain after H. pylori eradication, and effects on hormones such as ghrelin that control appetite.
    Helicobacter 09/2011; 16 Suppl 1:33-7. · 3.51 Impact Factor
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    ABSTRACT: Assessment of the long-term safety of anti-tumour necrosis factor therapies is vital for the safe treatment of inflammatory bowel disease, a disease affecting a young cohort of patients. The aim of this retrospective study was to assess the safety and long-term outcome of infliximab use in clinical practice in our institution on an intention to treat basis over the 10-year period from December 1998 to 31 December 2008. All cases receiving infliximab for ulcerative colitis or Crohn's disease over a 10-year period were identified from hospital pharmacy records. The study was based on a single centre cohort, with an unselected patient group. A total of 271 patients were identified as receiving infliximab for either Crohn's disease or ulcerative colitis over the 10-year study period. In total, 2169 infusions were given to the patient cohort. Fifty adverse events led to discontinuation of infliximab therapy in 47 cases. Two patients stopped due to neurological complications. There were six malignancies diagnosed within the cohort during the study period. Four of these were diagnosed while the individual was receiving Infliximab and two occurred at an interval of 21-52 months post their final infliximab infusion. A total of five deaths (1.5%) were observed during the study period. Infliximab therapy seems to be safe and efficacious in the long term. Although the development of malignancy remains a concern, we have not seen an increased risk of serious infection within our cohort.
    European journal of gastroenterology & hepatology 07/2011; 23(7):603-6. · 1.66 Impact Factor
  • Gastroenterology 01/2011; 140(5). · 12.82 Impact Factor
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    ABSTRACT: Colorectal polyps are usually asymptomatic and are found opportunistically. Individuals with adenomata are at increased risk for cancer and therefore guidelines exist for surveillance of these lesions including those of the British Society of Gastroenterology (BSG). Deviation from these guidelines is common and increases the workload of endoscopy. We examined those individuals waiting for endoscopy for polyp surveillance to see whether strict adherence to BSG guidelines could facilitate opportunities for screening. A total of 413 patients with earlier colonic polyps were examined, of whom 50 patients were excluded based on having alternative indications for surveillance, 179 (49.3%) were appropriately scheduled for surveillance and 184 patients (55.9%) were scheduled incorrectly. Seventy-nine patients (30%) could have been discharged; of these, 59 had hyperplastic polyps. Of the remaining 105 inappropriate triages under surveillance at the wrong interval, seven patients were scheduled for too infrequent surveillance and 98 were too frequent. A total of 284 patients with adenomatous polyps were under surveillance of whom 11 patients (3.8%) were in the high-risk category and all were appropriately scheduled, and 75 patients (26.4%) were in the intermediate-risk category, of whom 48 were appropriately scheduled, 20 were incorrectly triaged as high risk and seven were triaged as low risk. A total of 198 (69.7%) patients were in the low-risk category, 117 of these were correctly triaged, 15 were incorrectly triaged as high risk and 66 were classified as intermediate risk. Over a five-year period, 318 unnecessary colonoscopies are being performed. On the basis of the data obtained from a population-based colorectal screening programme using immunohistochemical-faecal occult blood testing in our department another 1516 patients could be screened annually without requiring any additional endoscopy resources, if strict adherence to guidelines was assured.
    European journal of cancer prevention: the official journal of the European Cancer Prevention Organisation (ECP) 10/2010; 20(1):40-5. · 2.21 Impact Factor
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    ABSTRACT: Helicobacter pylori eradication rates have fallen considerably in recent years. Antibiotic resistance is thought to be rising. To examine the levels of resistance to metronidazole (MTZ) and clarithromycin (CLA) in H. pylori, isolates were taken in a reference centre in Ireland from 2007 to 2008 and were compared to a similar cohort from a study in 1997. Antimicrobial susceptibilities were tested by E-test. Frequencies of spontaneous metronidazole and clarithromycin resistance were measured on an agar plate containing the antibiotics at concentrations of 2x and 4x minimum inhibition concentration values. Clinical data were obtained from charts, laboratory and endoscopy reports. Two hundred and twenty-two patients were analyzed, 98 were females. Colonies amenable to culture were grown in 219 patients. Thirty-seven had prior attempts at eradication therapy (all with amoxicillin-CLA-proton pump inhibitor. A total of 31.5% of the patients had strains resistant to MTZ and 13.2% of the patients were noted to have strains resistant to CLA. About 8.6% of the patients had strains resistant to both the agents. CLA resistance was 9.3% in those who had no prior eradication therapy compared with 32.4% of those who had. CLA resistance increased from 3.9%, among treatment-naive patients in 1997, to 9.3% in our study. MTZ resistance was 29.1% in the treatment-naive population. In 1997, MTZ resistance in the treatment-naive cohort was 27.1%. MTZ resistance was more likely to occur in females (35.4 vs. 28.5%) than in males. This study shows that resistance to CLA among Irish patients infected with H. pylori has increased since 1997. The future of treatment may well lie in the widespread use of sensitivity testing before the treatment. This would promote an accurate treatment.
    European journal of gastroenterology & hepatology 03/2010; 22(9):1123-7. · 1.66 Impact Factor
  • Gastroenterology 01/2010; 138(5). · 12.82 Impact Factor
  • Gastroenterology 01/2010; 138(5). · 12.82 Impact Factor
  • Gastroenterology 01/2010; 138(5). · 12.82 Impact Factor
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    ABSTRACT: Video capsule endoscopy is an invaluable tool for examining the small bowel. It is non-invasive and generally well tolerated, however its role in the assessment of the severity and extent of small bowel Crohn's disease has not, to date, been adequately evaluated. All capsule endoscopies performed over a two year period in a tertiary referral centre in subjects with known or suspected Crohn's disease were reviewed. Twenty-six capsule endoscopy studies in total were included. These were performed in 15 cases of known Crohn's disease, 5 cases of suspected Crohn's disease, 3 cases of endoscopically diagnosed non-specific terminal ileal inflammation and finally 3 post colectomy cases of indeterminant being considered for IPAA formation. Ten patients known to have small bowel Crohn's disease were prospectively recruited; of 3 with normal small bowel follow through or CT exams, one had an abnormal capsule endoscopy. The other 7 patients had small bowel follow through or abdominal CT scans consistent with small bowel Crohn's disease; additional mucosal abnormalities were detected by capsule endoscopy in 6 cases with capsule retention in the stomach in one. Of 5 with colonic Crohn's disease normal small bowel imaging corresponded with normal capsule endoscopy in all but one. A diagnosis of Crohn's disease was made in 2 out of 5 cases of suspected Crohn's disease on the basis of the capsule endoscopy findings. Three patients with non-specific acute terminal ileal inflammation at ileocolonoscopy were confirmed to have ongoing inflammation. The capsule was retained in four subjects beyond 24 h. Capsule endoscopy more accurately determines the severity and extent of the Crohn's disease in the small bowel than traditional imaging modalities.
    Journal of Crohn s and Colitis 12/2009; 3(4):282-6. · 3.39 Impact Factor
  • Aamir Saleem, Asghar Qasim, Humphrey J O'Connor, Colm A O'Morain
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    ABSTRACT: An ideal antibiotic regimen for Helicobacter pylori should achieve eradication rates of approximately 90%. Current 7-day triple therapy is successful in about two-thirds of patients. A novel treatment is required to achieve higher eradication with minimal induction of bacterial resistance. The aim of this article is to evaluate the safety and efficacy of a single triple capsule (Pylera) containing bismuth, metronidazole and tetracycline, given with omeprazole for the eradication of H. pylori infection. Extensive literature searches were conducted using PubMed data from 1982 to 2007. This search included headings of H. pylori, bismuth and eradication therapy. The triple capsule Pylera, when given with omeprazole, achieved eradication rates ranging between 84 and 97%. Eradication rates were similar for clarithromycin- and metronidazole-resistant strains. Eradication rates with an omeprazole, bismuth, metronidazole and tetracycline regimen appeared comparable for metronidazole-resistant and -sensitive strains. This effect is not seen with the use of triple therapy in cases of clarithromycin resistance. Clinical trials did not report any serious side effects from bismuth-based regimens and compliance was similar to standard triple therapy. Bismuth-based triple therapy using Pylera is a simplified, effective and well-tolerated regimen achieving cure rates of above 90%.
    Expert Review of Anticancer Therapy 10/2009; 7(7):793-9. · 3.22 Impact Factor
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    ABSTRACT: Helicobacter pylori infection is eradicated with antimicrobial agents and drug-resistant strains make successful treatment difficult. Geographical variations in virulence-factor genotype also exist. To evaluate prevalence of drug resistance and virulence-factor genotype in Irish H. pylori strains and to investigate if there is any relationship between drug resistance and genotype. Helicobacter pylori strains isolated from 103 patients were examined. Antimicrobial susceptibilities were tested by Etest. The virulence-factor genotypes were determined using PCR. Frequencies of spontaneous metronidazole-resistance were measured in vitro. Metronidazole resistance was present in 37.9% of strains examined. 16.5% of strains were clarithromycin-resistant and resistance to both agents observed was found in 12.6% of strains. 68% of strains were cagA(+). The dominant vacA type was s1/m2, followed by s1/m1 and s2/m2. The metronidazole resistance rate in cagA(-) group was significantly higher than in cagA(+) (P = 0.0089). Spontaneous resistance to metronidazole in cagA(-) occurred in higher frequency when compared with cagA(+). cagA(+) and vacAs1/m2 type was the dominant genotype in Irish H. pylori strains. Significant rates of metronidazole resistance were observed in cagA(-) group. cagA(-) strains tend to acquire metronidazole resistance in vitro. Absence of cagA might be a risk factor in development of metronidazole resistance.
    Alimentary Pharmacology & Therapeutics 08/2009; 30(7):784-90. · 4.55 Impact Factor
  • Asghar Qasim, Colm A O'Morain, Humphrey J O'Connor
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    ABSTRACT: Treatment of Helicobacter pylori (H. pylori) infection has become a key factor in the management of dyspepsia and is the treatment of choice for peptic ulcer disease. First-line eradication regimens combining a proton pump inhibitor (PPI) with clarithromycin and amoxicillin or metronidazole are considered most effective when given for a minimum period of 1 week. Eradication regimens of shorter duration have shown promising results but clinical experience remains limited. Pharmacological properties such as bioavailability and plasma concentrations of individual PPIs differ between individuals but it remains unclear whether these differences impact on the efficacy of eradication therapy and are influenced by renal or hepatic impairment. Bioavailability of PPIs also differs and is impacted on by factors including intragastric pH, metabolic pathways, potency on an mg-for-mg basis and intrinsic antibacterial activity. Several significant pharmacokinetic differences between the PPIs do not seem to influence overall H. pylori eradication rates for first-line triple therapy. However, comparison of factors including pharmacokinetics and treatment duration may prove important in achieving successful eradication with second- and third-line treatments. Based on the factors which influence therapy outcome, we suggest an algorithm for the use of H. pylori eradication therapies.
    Fundamental and Clinical Pharmacology 02/2009; 23(1):43-52. · 1.99 Impact Factor
  • Gastrointestinal Endoscopy - GASTROINTEST ENDOSCOP. 01/2009; 69(5).
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    ABSTRACT: Antibiotic resistance has resulted in unsatisfactory eradication results with dual and now triple therapy in many countries. Newer antibiotics and changes in dosing and duration of therapy may overcome resistant strains but may only provide limited improvement in eradication rates. Sequential therapy with amoxicillin (1 g twice a day) and a proton pump inhibitor (PPI) (twice a day) given for 5 days followed by a PPI plus clarithromycin (500 mg twice a day) and tinidazole (500 mg twice a day) for 5 days is now a first-line therapy for Helicobacter pylori in some countries. Standard triple therapy is effective in regions where clarithromycin resistance is low. Levofloxacin based triple therapy is an effective alternative to quadruple therapy in second-line treatment. Adjuvant therapy may reduce side-effects and improve compliance. Molecular and genomic research on H. pylori may result in the development of targeted antibiotic therapy; however, more research is required in this field. Further research in vaccination is also necessary before this can become an option in clinical practice.
    Helicobacter 10/2008; 13 Suppl 1:35-40. · 3.51 Impact Factor
  • B J Egan, H J O'Connor, C A O'Morain
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    ABSTRACT: Since the discovery of Helicobacter pylori in the early 1980s several treatment regimens have been developed to effectively treat this infection. International guidelines have allowed consensus on the best management and improved eradication rates. In recent years increasing antimicrobial resistance and falling eradication rates highlight the need for updated guidelines. In this article we review the most recent European management guidelines and in view of the unavailability of some drugs consider new treatment regimens for the management of H. pylori in Ireland.
    Irish Journal of Medical Science 09/2008; 177(3):185-8. · 0.51 Impact Factor

Publication Stats

1k Citations
664.85 Total Impact Points


  • 2002–2011
    • Trinity College Dublin
      • • Department of Gastroenterology and Hepatology
      • • Department of Clinical Medicine
      Dublin, L, Ireland
  • 1996–2011
    • The Adelaide and Meath Hospital Ireland
      Dublin, Leinster, Ireland
  • 2009
    • Naas General Hospital
      Blessington, Leinster, Ireland
  • 2006
    • St. James's Hospital
      Dublin, Leinster, Ireland
  • 2004
    • Trinity College
      Hartford, Connecticut, United States
  • 1999–2002
    • University College Dublin
      Dublin, Leinster, Ireland
  • 1995–1997
    • Midland Regional Hospital Tullamore
      Tulach Mhór, Leinster, Ireland
  • 1987
    • The University of York
      • Yorkshire Cancer Research Unit
      York, ENG, United Kingdom
  • 1984
    • University of Leeds
      • School of Medicine
      Leeds, ENG, United Kingdom