MBBS II Helicobacter pylori PDF

CLINICAL CASE A 48-year-old man presents with a 2-month history of upper abdominal pain associated with nausea. It is made worse when he drinks coffee, soda, or alcohol. He takes antacid medications that provide temporary relief. He had smoked for 20 years and used to drink one or two alcoholic...

CLINICAL CASE A 48-year-old man presents with a 2-month history of upper abdominal pain associated with nausea. It is made worse when he drinks coffee, soda, or alcohol. He takes antacid medications that provide temporary relief. He had smoked for 20 years and used to drink one or two alcoholic beverages in a week and took NSAIDs often. His general physical examination and vital signs are normal. Abdominal examination is notable for epigastric tenderness. A CBC shows a mild hypochromic, microcytic anemia. He is referred to a gastroenterologist for an upper GI endoscopy, which shows diffuse gastritis and a gastric ulcer. Author: Prof. Dr. Jatan B.S. What organism is most likely to be visualized on histologic evaluation of a gastric biopsy specimen? Besides microscopy, what other test provide rapid detection of this organism? What two factors facilitate this organism's ability to colonize stomach? Organism on histologic evaluation of a gastric biopsy: The organism likely to be visualized on biopsy specimen is Helicobacter pylori. Other clinical test for rapid detection: The urease test. Factors facilitating this organism's ability to colonize the stomach: Blockage of acid production by a bacterial acid-inhibitory protein and neutralization of acid by ammonia produced by urease activity. Author: Prof. Dr. Jatan B.S.  Helicobacter pylori Introduction Morphology, cultural characters & biochemical reactions Virulence and pathogenesis Clinical features Laboratory diagnosis Treatment and Prevention Author: Prof. Dr. Jatan B.S.  Introduction Helicobacter pylori, which persistently colonizes the stomachs of ~50% of the world's human population, is the main risk factor for peptic ulceration as well as for gastric adenocarcinoma and gastric MALT (mucosa-associated lymphoid tissue) lymphoma. Author: Prof. Dr. Jatan B.S.  In 1983, John Robin Warren and Barry James Marshall in Australia described a spiral campylobacter like organism colonizing human stomach and was initially named Campylobacter pyloridis and subsequently as C. pylori which has now been assigned as Helicobacter pylori. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S.  There are 23 species but only few are medically important Helicobacter species associated with Human Disease Species Common Reservoir Human Disease Hosts H. pylori Human, primates, pigs Gastritis, Peptic ulcer, gastric adenocarcinoma, MALT B-cell lymphoma H. heilmannii Human Gastritis H. cinaedi Human, hamster Gastroenteritis, septicemia, proctocolitis H. fennelliae Humans Gastroenteritis, septicemia, proctocolitis The infection is present in 70%-90% of persons with duodenal ulcers and in ~ 70% of those with gastric ulcers. Antibiotic treatment of H. pylori infection promotes healing of ulcers and tends to prevent their recurrence. Author: Prof. Dr. Jatan B.S.  Morphology, cultural characters & biochemical reactions H. pylori is short curved, S shaped GNB(3X0.5-0.9 µm). It is motile by a tuft of unipolar flagella (lophotrichate). Strict microaerophilic (10%CO2,5%O2, 85%N2), does not grow anaerobically. High humidity and 5-10% CO2 are required for growth. Media include Butzler’s medium, Skirrow's medium (Similar to chocolate agar with vancomycin, polymyxin B, trimethoprim) and other selective media with antibiotics (e.g., cefazolin, bacitracin, nalidixic acid, amphotericin). Most strains take 3-7 days to grow. Colonies: Small, translucent, gray, 1–2 mm in diameter, weakly β-hemolytic. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S. Biochemical Characteristics of Helicobacter species Test H. pylori H. cinaedi H. fennelliae Catalase and Oxidase + WP WP H2S ± ± ± Urease + - - Optimal growth 25ºC - - - 37ºC + + + 42ºC - - - Growth susceptibility Cephalothin (30µg) S S S Nalidixic acid (30µg) R S S Author: Prof. Dr. Jatan B.S.  Virulence and pathogenesis Two conditions are key for the development of peptic ulcers: (1) H. pylori infection (2) Mucosal exposure to gastric acid and pepsin. Normal phenomena: Gastric mucus is relatively impermeable to acid and has a strong buffering capacity. On the lumen side of the mucus, the pH is low (1.0–2.0) while on the epithelial side pH is about 7.4. H. pylori grows optimally at pH of 6.0–7.0 and would be killed or do not grow at the pH within the gastric lumen. Author: Prof. Dr. Jatan B.S. What makes H. pylori cause ulcer? H. pylori’s motility and ability to reach deep mucous layer near the epithelial surface where physiologic pH is present. Production of proteases and phospholipases which break down the glycoprotein-lipid complexes in the gastric mucus, thus weakening the first line of mucosal defense. Bacterial toxins and LPS damage the mucosal cells. Bacterial proteins are immunogenic & induce inflammation. The urease breaks down urea to form toxic compounds such as ammonium chloride and monochloramine further buffering of acid and may directly damage the cells. Author: Prof. Dr. Jatan B.S.  Although H. pylori does not invade the tissues, it induces an intense inflammatory response. Increased production of proinflammatory cytokines such as IL-1, IL-6, TNF and most notably, IL-8 produced by the mucosal epithelial cells recruits and activates neutrophils. Several bacterial gene products are involved in this. E.g. CagA, VacA, BabA etc Author: Prof. Dr. Jatan B.S.  Bacterial pathogenicity island and toxin gene Cag pathogenicity island, made up of 30 genes has cagA (Cytotoxin associated gene A), cagA gene codes for a relatively long 1186 amino acid protein. VacA (Vacuolating toxin gene A) some of which encode pro-inflammatory proteins and a complex type IV secretion system. This toxin cause epithelial injury and cause ulcer. BabA recognizes a polysaccharide-modified protein present on the surface of mucosal cells known as the Lewis b antigen. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S. Gastric metaplasia and H. pylori colonization: H. pylori enhances gastric acid secretion and impairs duodenal bicarbonate production, thus reducing luminal pH in the 1st part of duodenum which favor gastric metaplasia (the presence of gastric epithelium) in the duodenum. Such metaplastic foci provide areas for H. pylori colonization. Author: Prof. Dr. Jatan B.S.  Several H. pylori proteins are immunogenic, and they evoke a robust immune response in the mucosa. Both activated T cells and B cells can be seen in chronic gastritis caused by H. pylori. The B lymphocytes aggregate to form follicles. The role of T and B cells in causing epithelial injury is not established, but may be involved in the pathogenesis of MALT lymphomas. Author: Prof. Dr. Jatan B.S.  NSAIDs are the major cause of peptic ulcer disease in persons who do not have H. pylori infection Risk factors for NSAID-induced gastroduodenal toxicity are increasing age, higher dose, and prolonged usage. NSAIDS suppress mucosal prostaglandin synthesis and this increases secretion of HCl, and reduces bicarbonate & mucin production. Synthesis of glutathione, a free-radical scavenger, is also reduced. Some NSAIDs can penetrate the gut mucosal cells as well. Author: Prof. Dr. Jatan B.S.  Excess production of gastric acid from a tumor (Zollinger-Ellison syndrome) causes multiple peptic ulcerations in the stomach, duodenum, and even the jejunum. Smoking impairs mucosal blood flow and healing. Alcohol has not been proved to directly cause peptic ulceration, but alcoholic cirrhosis is associated with an increased incidence of peptic ulcers. Corticosteroids in high dose and with repeated use promote ulcer formation. Personality & psychological stress also contribute. Author: Prof. Dr. Jatan B.S. Sites of ulcer: Anterior & posterior walls of 1st portion of the duodenum. Lesser curvature of the stomach Occasional on the greater curvature or anterior or posterior walls of the stomach, the very same locations of most ulcerative cancers. Author: Prof. Dr. Jatan B.S. Histopathological changes: Ulcers of the alimentary tract are defined histologically as a breach in the mucosa that extends through the muscularis mucosae into the submucosa or deeper. This is to be contrasted to erosions, in which there is a breach in the epithelium of the mucosa only. Erosions may heal within days, whereas healing of ulcers takes much longer. Author: Prof. Dr. Jatan B.S. Gross features: All ulcers, whether gastric or duodenal, have an identical gross and microscopic appearance. Most are round, sharply punched-out craters 2-4 cm in diameter, those in the duodenum tend to be smaller, and occasional gastric lesions are significantly larger. The surrounding mucosal folds may radiate like wheel spokes. The base of the crater appears remarkably clean, as a result of peptic digestion of the inflammatory exudate and necrotic tissue. Peptic ulcer of the duodenum. The ulcer is small (2 cm) with a sharply punched-out Author: Prof. Dr. Jatan B.S. appearance. Unlike cancerous ulcers, the margins are not elevated.  Infrequently, an eroded artery is visible in the ulcer (usually associated with a history of significant bleeding). If the ulcer crater penetrates through the duodenal or gastric wall, a localized or generalized peritonitis may develop. Perforation can be sealed by adjacent structures such as adherent omentum, liver or pancreas. Author: Prof. Dr. Jatan B.S. Microscopic features: The histologic appearance varies with the activity, chronicity, and degree of healing. In a chronic, open ulcer, four zones can be distinguished: 1. The base and margins have a thin layer of necrotic fibrinoid debris underlain by 2. A zone of active nonspecific inflammatory infiltration with neutrophils predominating 3. Granulation tissue, deep to which is 4. Fibrous, collagenous scar that fans out widely from the margins of the ulcer. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S. Scarring and healing Vessels trapped within the scarred area are characteristically thickened and occasionally thrombosed, but in some instances they are widely patent. With healing, the crater fills with granulation tissue, followed by re- epithelialization from the margins and more or less restoration of the normal architecture but extensive fibrous scarring remains. Author: Prof. Dr. Jatan B.S.  Clinical features Epigastric pain (gnawing, burning, or boring pain) worse at night and occurs usually 1-3 hours after meals during the day. The pain is relieved by alkalis or food sometimes. Nausea, vomiting, bloating, belching and significant weight loss may be because of some hidden malignancy. Bleeding and perforation in one-third of patients. Malignant transformation in about 2% of patients, generally from ulcers in the pyloric channel, very rare with gastric ulcers. Author: Prof. Dr. Jatan B.S.  Diagnosis Clinical diagnosis based on history and clinical examination Lab diagnosis Specimens (Should be fresh and not delayed in transport for more than 3 hours and can be kept up to 5 hours at 4ºC) 1. Gastric & duodenal biopsy specimens for histopathological examination and also minced in saline and used for culture. 2. Blood is collected for determination of serum antibodies. Smears Routine stains demonstrate gastritis, and Giemsa or special silver stains can show the curved or spiral organisms. Author: Prof. Dr. Jatan B.S. Noninvasive detection methods: Breath test –Rapid presumptive diagnosis (100% sensitive and 99.2% specific) Serology Invasive detection methods: Endoscopy (biopsy) Urease test – Rapid presumptive diagnosis Stain of histologic section: Gram, Warthin-Starry stain, Giemsa stain, Acridine orange stain – Definitive diagnosis Culture – Small grey, 1-2 mm colonies- Biochemical: Oxidase, catalase, urease – Definitive diagnosis PCR- can detect HP within a few hours. Not routine in clinical use. Author: Prof. Dr. Jatan B.S. Author: Prof. Dr. Jatan B.S. Breath test –Rapid presumptive diagnosis: It is vivo tests for urease activity. 13C- or 14C-labeled urea is ingested by the patient. If H. pylori is present, the urease activity generates labeled CO2 that can be detected in the patient's exhaled breath after 10-30 minutes. Serology (Antibody detection) The serum Abs persist even if the H. pylori infection is eradicated hence its role is limited. IgG level of >12 units is significant. Author: Prof. Dr. Jatan B.S. Urease test – Rapid presumptive diagnosis Rapid tests to detect urease activity are widely used for presumptive identification of H. pylori in specimens. Gastric biopsy material can be placed onto a urea-containing medium with a color indicator. If H. pylori is present, the urease rapidly splits the urea and the resulting shift in pH yields a color change in the medium. Author: Prof. Dr. Jatan B.S. Helicobacter pylori colonized on the surface of regenerative epithelium, stained with the Warthin-Starry method. Author: Prof. Dr. Jatan B.S. Culture: Butzler’s medium Skirrow's medium HP medium BHI Modified Thayer-Martin agar Growth of H. pylori on HP and BHI agar plates Author: Prof. Dr. Jatan B.S. Rapid detection of H. pylori Antibody form whole blood/serum/plasma can also be done. Detection of H. pylori antigen in stool specimens by enzyme immunoassay (89% sensitive and 95% specific) is appropriate as a test of cure for patients with known H. pylori infection who have been treated. Author: Prof. Dr. Jatan B.S.  Treatment and Prevention Recommended Treatment Regimens for Helicobacter pylori Regimen, Duration Drug 1 Drug 2 Drug 3 Drug 4 First-Line Treatment Regimen 1: OCA Omeprazole (20 mg Clarithromycin (500 Amoxicillin — (7–14 days) bid) mg bid) (1 g bid) Regimen 2: OCM Omeprazole (20 mg Clarithromycin (500 Metronidazole — (7–14 days) bid) mg bid) (500 mg bid) Second-Line Treatment Regimen 3: OBTM Omeprazole (20 mg Bismuth Tetracycline (500 Metronidazole (500 mg tid) (14 days) bid) subsalicylate (2 tabs mg qid) qid) Author: Prof. Dr. Jatan B.S.  Amoxicillin resistance rare (0.3%-1.4% generally, rates as high as 38% have been reported). It may be because of transfer of gene encoding drug resistance.  Metronidazole and Clarithromycin resistance has also been found.  Vaccines are under trials on animals and humans Author: Prof. Dr. Jatan B.S.