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Running head: HELICOBACTER PYLORI
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Helicobacter Pylori
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Helicobacter pylori is a spiral-shaped Gram-negative bacillus that thrives in the stomach;
it can be the cause of duodenal ulcers, peptic ulcers, gastritis, gastric adenocarcinoma and gastric
glandular atrophy. It secretes urease enzyme that catalyse urea hydrolysis to produce ammonia
and carbon dioxide. The products create a neutral microenvironment that surrounds the
bacterium. The principal mechanism by which the H.pylori infections occur is not known well.
Those who are at risk of H.pylori infection include those who are in developing countries, those
who share households and those in overcrowded places.
H. pylori can be observed microscopically using smeared tissue gram stains or imprints
of biopsies. The bacteria has been identified as curved rods. Specimens for the culture of this
bacteria are separated from gastric mucosa of untreated patients. The specimens can also be got
from the rectum, faeces, oesophagus and gall bladder.
H. pylori mycobacteria is cultured in blood agar media containing Columbia or Brucella
agar as the base. The agar is supplemented with cyclodextrin B for culture media that are blood
free. Horse or sheep blood may be used to improve bacterial growth, but horse blood has a
higher growth rate than sheep blood. Egg yolk emulsion agar can be used to culture H. pylori.
This bacteria grows poorly on selective antibiotic-containing media. Liquid media can be used
for H. pylori cultivation, but it grows slowly wit-formation of coccoid forms. Stuarts transport
medium is usually used to transport biopsies for up to 24 hours at 40C.
H. pylori microorganisms are spiral and microaerophilic. In gastric biopsy systems, the
microorganisms show bluntly rounded ends. When they are cultured, however, they assume rodlike shapes. When culturing occurs for an extended period, coccoid forms of the microorganism
are abundant. These forms are metabolically active, but they cannot be cultured in vitro. The size
of H. pylori microorganism ranged from 2.5 to 5.0 micrometres in length and 0.5 to 1.0 in
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diameter. There are four to six flagella in each H. pylori microorganism to aid in bacterial
motility. The flagella extend from the flagellar sheath. If tannic acid is used to examine the
ultrastructure of the bacteria, the outer membrane is seen to be coated with a structure similar to
glycocalyx. This surface of the H. pylori can be linked to the microvilli in the gastrointestinal
system. H.pylori cells that have been associated with aggregates of Urease and a heat shock
protein GroEL. The function of cryptic plasmids of strains of Helicobacter pylori is not well
understood.pHe112, and pHe14 plasmids have mobilization regions for conjugative transfer.
Bacterial conjugation is a possible mechanism of lateral DNA transfer in the in the
microorganism.
As a microaerophilic bacteria, it means that it requires oxygen for survival. The presence
of hydrogenase in the organism allows energy to be utilized through oxidation of molecular
hydrogen in the intestinal microbes. Production of oxidases, catalases, and ureases by the
microorganism enables it to form biofilms. Also, the ability of the microorganism to convert
from spiral to viable but non-culturable coccoid could facilitate its survival rates. The presence
of Lophotrichous bacteria in the H.pylori makes it highly motile.
There are five major outer membrane families in Helicobacter pylori. Putative and known
adhesins fall under the largest family. Others include flagellum associated proteins, porins as
well as iron transporters. The outer membrane of H. pylori just like the membranes of other
Gram-negative bacteria has lipopolysaccharides and phospholipids. However, the O-antigen of
the Lipopolysaccharide may be similar with the Lewis blood group antigens that are located in
the gastrointestinal epithelium. Cholesterol and glycosides are present in the outer membrane of
these microorganisms
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A large diversity of strains of H. pylori has been demonstrated. Genomes of three strains of H.
pylori have been successfully sequenced. Strain “26695” was found to have 1.7 million base
pairs. An analysis of transcription at the nucleotide resolutions has confirmed the acid induction
of urease. The molecular masses of H. pylori outer membrane proteins are approximately
80kDa.HspB and Urease have been found to be in high concentration in the outer membrane
proteins.
There are no defined media for the organism since it has a complex solid or liquid media.
There is supplementation of serum, whole blood, and egg yolk emulsion. As much as these
supplements may act as nutritional substrates to the microorganism, detoxification may be their
other function. It Is due to this reason that the supplementation with cyclodextrins promotes
proper growth of H. pylori. Under microaerobic conditions, fresh isolates of the bacteria grow
well. Some strains turn to be aerotolerant after laboratory passage that they can survive in 10%
carbon IV oxide. It grows poorly under anaerobic conditions. Maximum growth occurs at
temperature of about 350C
Microbiological studies have shown that H. pylori does not require carbohydrates for its
metabolism whether oxidative or fermentative. The microorganism, however, has a glucose
kinase activity linked to the bacterial cell membrane. It appears to catabolize D-glucose through
specific transporters. H. pylori has also been shown to have urea cycle activity that serves as a
way of removing excess nitrogen from the cell. An essential component of H. pylori metabolism
is Fumarate reductase which can be targeted to have therapeutic effects. Polyphosphate granules
have been found to be energy reserves for the bacterium, and they are associated with the gastric
epithelium
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Since the microorganism is associated with infections like Zollinger Ellison, should be
eradicated from the body once it has been identified in person suffering from peptic ulcers.
Complications of H. pylori infection include internal bleeding, obstruction, perforation and
peritonitis.The most effective eradication of this bacterium is one week twice daily regimens of a
proton pump inhibitor such as omeprazole, and clarithromycin and amoxicillin. Omeprazole
20mg, clarithromycin 500mg, and amoxicillin 1g or omeprazole 20mg, clarithromycin 250mg
and metronidazole 400mg are mostly used. Ranitidine bismuth citrate is a chemical entity which
incorporates bismuth into the ranitidine molecule and was designed for H. pylori eradication.
This regimen is not as effective as the triple therapy in H. pylori eradication discussed above.
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Annotated Bibliography
1. Colledge, H. & Cafasso,J.(2015, Oct 13). H.Pylori Infection. Retrieved from
http://www.healthline.com/health/helicobacter-pylori#Causes2
This article answers a lot of common questions about helicobacter pylori that someone
who has never heard of this particular bacteria, would ask. It explains what helicobacter
pylori is, who is at risk, symptoms, how is it diagnosed, and how is it treated.
2. Rohrer,S., Holsten, L., Weiss, E., Benghezal, M., Fischer, W., & Haas, R. (2012).
Multiple Pathways of Plasmid DNA Transfer in Helicobacter pylori. Retrieved from
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447787/
In this article, there is a focus on the multiple pathways of plasmid DNA transfer in
Helicobacter pylori. Some topics include: verification of plasmid transfer between
different h. pylori strains, DNaseI-sensitive natural transformation and a DNaseI-resistant
transfer mechanism, plasmid-encoded relaxase MobA but not chromosomally encoded
relaxases contribute to plasmid transfer, bacterial strains and growth conditions,
electroporation natural transformation and conjugation of h. pylori, and mating
experiments.
3. Dunn, B.E, Cohen, H., & Blaser, M.J. (1997). Helicobacter pylori. Retrieved from
http://cmr.asm.org/content/10/4/720.full.pdf
The article explains the discovery of h. pylori and historical development of its role in human
disease, epidemiology of h. pylori infection, microbiological characteristics , pathogenesis of
infection, and diagnosis of infection.
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4. Castillo-Rojas, G., Cerbón ,M.A., & López-Vidal, Y. (2008).Presence of Helicobacter pylori in a
Mexican Pre-Columbian Mummy. Retrieved from
http://bmcmicrobiol.biomedcentral.com/articles/10.1186/1471-2180-8-119
This article talks about the presence of helicobacter pylori in pre-Columbian mummies from
Northern Mexico. They explain the research methods that were used on mummies from La
Ventana and Durango, the results of their biopsies in order to increase knowledge about human
beings and their diseases.
5. Pommerville, J.C. (2014). Fundamentals of Microbiology, 10th edition. [VitalSource Bookshelf
Online]. Retrieved from https://kaplan.vitalsource.com/#/books/9781284047059/
This book uses real life examples in order to understand the significance of microbiology in
today’s world. The information from this book is imperative to nursing and health sciences
regarding diseases and infections.