Helicobacter pylori


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Helicobacter pylori


Introduction to bacteria

Bacterial structure and functions

Gram positive bacteria

Staphylococcus epidermidis

Staphylococcus aureus

Staphylococcus saprophyticus

Streptococcus viridans

Streptococcus pneumoniae

Streptococcus pyogenes (Group A Strep)

Streptococcus agalactiae (Group B Strep)


Clostridium perfringens

Clostridium botulinum (Botulism)

Clostridium difficile (Pseudomembranous colitis)

Clostridium tetani (Tetanus)

Bacillus cereus (Food poisoning)

Listeria monocytogenes

Corynebacterium diphtheriae (Diphtheria)

Bacillus anthracis (Anthrax)


Actinomyces israelii

Gram negative bacteria

Escherichia coli

Salmonella (non-typhoidal)

Salmonella typhi (typhoid fever)

Pseudomonas aeruginosa


Klebsiella pneumoniae


Proteus mirabilis

Yersinia enterocolitica

Legionella pneumophila (Legionnaires disease and Pontiac fever)

Serratia marcescens

Bacteroides fragilis

Yersinia pestis (Plague)

Vibrio cholerae (Cholera)

Helicobacter pylori

Campylobacter jejuni

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

Francisella tularensis (Tularemia)

Bordetella pertussis (Pertussis/Whooping cough)


Haemophilus influenzae

Haemophilus ducreyi (Chancroid)

Pasteurella multocida


Mycobacterium tuberculosis (Tuberculosis)

Mycobacterium leprae

Mycobacterium avium complex (NORD)

Other bacteria

Mycoplasma pneumoniae

Chlamydia pneumoniae

Chlamydia trachomatis

Borrelia burgdorferi (Lyme disease)

Borrelia species (Relapsing fever)


Treponema pallidum (Syphilis)

Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species

Coxiella burnetii (Q fever)

Ehrlichia and Anaplasma

Gardnerella vaginalis (Bacterial vaginosis)


Helicobacter pylori


0 / 15 complete

USMLE® Step 1 questions

0 / 2 complete

High Yield Notes

6 pages


Helicobacter pylori

of complete


USMLE® Step 1 style questions USMLE

of complete

A group of researchers is evaluating the association between bacteria and peptic ulcer disease. A bacterial species is isolated, and its enzymatic makeup and other laboratory characteristics are studied. Which of the following bacteria features can be used in the diagnosis?  

External References

First Aid









Helicobacter pylori p. , 144


Helicobacter pylori p. , 144

Gastric adenocarcinomas

Helicobacter pylori p. , 144

Gastritis p. 388

Helicobacter pylori p. , 144

Helicobacter pylori p. , 144

associations p. 727

catalase-positive organism p. 125

disease association p. 388

Gram-negative algorithm p. 139

metronidazole p. 192

as oncogenic microbe p. 223

penicillins for p. 185

silver stain p. 123

urease-positive p. 125

urease-positive organism p. 125

MALT lymphomas

Helicobacter pylori p. , 144

Metronidazole p. 192

Helicobacter pylori p. , 144

Peptic ulcer disease p. 389

Helicobacter pylori p. , 144

Proton pump inhibitors (PPIs) p. 407

for Helicobacter pylori p. , 144


Helicobacter pylori p. , 144


Content Reviewers

Rishi Desai, MD, MPH


Evan Debevec-McKenney

Helicobacter pylori, or H. pylori for short, is a bacterium found in the stomach of over half of the world’s population.

In some individuals it can cause inflammation of the stomach lining; and can result in peptic ulcers.

In fact, complications from H. pylori ulcers is thought to have been the cause of death for the famous writer, James Joyce.

H. pylori is a gram-negative bacteria that’s shaped like a curved rod and it has 2 to 6 flagella, kind of like multiple tails, all at one end which it uses for movement.

It’s positive for urease, oxidase and catalase; and is a microaerophile, so that means it needs oxygen to survive, but requires less than the levels typically found in the atmosphere.

Now in the stomach, there are four regions - the cardia, the fundus, the body, and the pylorus.

And the pylorus itself is made up of two main parts: the antrum; and the pyloric canal, which connects to the first section of the small intestines called the duodenum.

Ok, now normally, the inner wall of the entire gastrointestinal tract is lined with mucosa, which consists of three cell layers.

The innermost layer is the epithelial layer and it absorbs and secretes mucus and digestive enzymes.

The middle layer is the lamina propria and it has blood and lymph vessels.

The outermost layer of the mucosa is the muscularis mucosa, and it’s a layer of smooth muscle that contracts and helps with the break down food.

The epithelial layer dips down below the surface of the stomach lining to form gastric pits.

And these pits are contiguous with gastric glands below which contain various epithelial cell types - each secreting a variety of substances.

So for example, foveolar cells, or surface mucus cells, secrete mucus, which is a mix of water and glycoproteins that coats the stomach epithelial cells.

With all of these digestive enzymes and hydrochloric acid floating around, the stomach and duodenal mucosa would get digested if not for this mucus which coats and protects the epithelial cells.

Within the glands, particularly in the body and fundus of the stomach, are parietal cells, which secrete hydrochloric acid to help maintain an acidic pH in the stomach.


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