User:Alexsheh/hp

genomics

from DNA Microarrays and Gene Expression: From Experiments to Data Analysis and Modeling

• mrna is about 10% of total RNA in bacteria
• vast majority of mRNA not polyadenylated
• How much total RNA is obtained from HP extractions?
• E. coli genome size 5.1 to 5.3 Mb
• B. subtilis genome size 4.2 Mb

From QIAGEN's RNeasy Bacteria Protection Mini Kit Bacterial species Culture medium No. cells RNA yield (μg) E. coli Minimal medium 5 x 108 25 E. coli LB 5 x 108 70 B. subtilis Minimal medium 1 x 108 8 B. subtilis LB 1 x 108 15

Helicobacter pylori

From Dunn et al. 1997 in Clinical Microbiology Reviews "Helicobacter pylori"

Where it is found in the stomach. Not in gastric mucosa but in the mucus layer overlying the tissue.

Culture time of isolates. Needed longer than usual culture time (5 days vs 3 days) to see colonies.

Diseases HP is linked to:

• inflammation in the gastric mucosa (chronic superficial gastritis)
  • normally asymptomatic. Not a disease per se.
• PMN infiltration (chronic active gastritis)
• duodenal ulceration
• gastric ulceration
• peptic ulcer disease (HP is major cause)
  • used to be considered idiopathic, but HP eradication leads to cure
• adenocarcinoma of stomach-DISTAL/lower not proximal/top. World’s most important gast. malignancy.
  • Associated strongly with development of ATROPHIC GASTRITIS (precursor lesion)
  • Gastric cancer is second leading cause of cancer death worldwide
• Also affects the lymphoid system
  • gastric non-Hodgkin’s lymphomas
  • gastric mucosa associated lymphoma tissue (MALT) lymphoma
• Many of these can be corrected with antimicrobial therapy
• Menetrier’s disease (gastric folds are hypertrophic) is believed to have some correlation

Epidemiology

• Developing countries: 70-90% of population. Infection acquired b4 10 yrs age.
• Developed countries: 25-50%. Lower as less kids infected.
• “Submerging” disease as it used to be close to universal and now less than 10% of kids get infected.
• A similar disease but milder gastritis is caused by H. heilmanii

Transmission

• No known reservoir outside the human stomach.
• Three putative routes
  • Iatrogenic: doctor’s endoscopes
  • Fecal-oral: Most important but fecal isolation is uncommon (is shedding intermittent? Or VBNC?)
  • Oral-oral: premastication of food

Morphology

• Spiral, microaerophilic, gram-negative bacteria
• Shape varies depending on environment
  • Seem bluntly rounded on ends in biopsy specimens. Rod-like in solid media culture (few spirals).
  • After prolonged culture, will become more coccoidal.
    • U shaped bacilli joined by a membranous structure
    • Coccoids are metabolically active but can’t be cultured in vitro
• Size is 2.5 to 5 microns long and 0.5 to 1.0 microns wide.
• Has 4-6 unipolar sheathed flagella, each about 30 microns long and 2.5 nm thick.