HELICOBACTER PYLORI: UPDATE
The role of Helicobacter Pylori (HP) in gastric
The Medical Benefits Schedule
The PyTest® has several
ulcers has been wel established by Nobel
changed in November 2006
advantages over other tests for
Prize winners Professor Barry Marshal and
to rebate diagnostic breath
HP and is now available through
Dr Robin Warren.
Australian researchers Professor Barry Marshall
conditions of overcrowding, hygiene and
and Dr Robin Warren were awarded the Nobel
questionable water supply. The bacteria may be
Prize in medicine in 2005 for their groundbreaking
spread to food via flies and cockroach excreta,
achievement in 1981 of identifying the bacteria
although spread by flies is less likely. Interestingly
Helicobacter Pylori as the causative organism for
there is a high prevalence of HP in sheep's milk and
70 to 90 per cent of gastric and duodenal ulcers.
this may have been where homo-sapiens first
Helicobacter Pylori (HP) is also found in 80 per
acquired the infection. Surprisingly it does not
cent of patients with gastric cancer and mucosal-
survive in yoghurt.
associated lymphoid tumours, and has been
classified as a carcinogen for these cancers. Ongoing Disease associations
research continues as to its relationship with cancer
and whether eradication therapy in the asymptomatic HP can adhere to the gastric epithelium via specific
patient may prevent gastric cancer.
adhesion molecules, then bacterial enzymes and cytotoxins can cause structural damage and induce
HP is a gram-negative bacteria that has evolved
an inflammatory response.
to inhabit the hostile environment of the human stomach. A spiral/helical shape and specialised
Aspirin and other NSAID side effects are more
motility al ow the organism to swim in a corkscrew-
likely in the presence of HP infection. Al patients
like fashion through the viscous gastric mucous
with dyspepsia should be considered as possibly
down to the gastric mucosa. It resists the effect of
having the infection through its causal association
gastric acidity by breaking down the endogenous
with gastritis. There is an association with morning
urea via the activity of the enzyme urease, creating a
sickness in pregnancy and this is important to
protective cloud of alkaline ammonia.
consider prenatal y.
First-line triple therapies include metronidazole,
Epidemiology of Helicobacter Pylori
clarithromycin and a proton pump inhibitor. Other therapies exist for the 25 per cent of patients where
Up to 40 per cent of Australians are colonised by
first-line therapy fails to clear the infection (90 per
HP. In some ethnic groups, over 50 per cent may be
cent of patients with failed therapy have resitance
colonised (eg some South East Asian groups).
to metronidazole and clarithromycin). Recent work
HP is most commonly spread by direct faecal oral
in microbiology at Melbourne Pathology showed
transmission, often within family groups. Toddlers
amoxicillin and tetracyclines remain useful agents.
often acquire HP from their mother due to shared
The role of re-infection is still being determined.
eating habits. Acquisition later in life is often through
Monitoring of patients to ensure bacterial eradication,
hygiene factors. For example, HP is often found
is associated with symptomatic improvement in
under the fingernails and in the mouth, particulary in
HELICOBACTER PYLORI: UPDATE cont.
body and is converted by the respiratory system to carbon dioxide (CO ).
THE UREA BREATH TEST FOR HELICOBACTER PYLORI
Medications to avoid during the PyTest®
The urea breath test was pioneered by Professor
Barry Marshal in 1988. He has since fine-tuned the
test and PyTest® is now the only breath test
accredited in Australia (TGA), USA (FDA) and
Canada (Health Canada).
Features of the PyTest®
Flagyl, Amoxil, Klacid,
Requires only a six-hour fast No baseline breath sample required
Least invasive test for HP
IgG and IgA serology is not useful for monitoring
Col ection procedure takes less than 20 minutes
eradication or acute infection. IgG tends to persist for
Some medications must be avoided prior to test
many years after infection and cannot be used as a
measure of active disease. Serology may not detect all
It is acceptable for patients to take medication for other
strains of HP due to varying immune responses.
conditions and to have breakfast as the test can be performed in the afternoon after the fasting period.
Medicare-rebatable for both diagnostic testing and
Faecal HP antigen testing offers some advantage in
eradication purposes (one month after treatment is
patients unable to withhold medications, or in young
completed) from 1 November 2006.
children living in a household where someone has HP infection. Samples need to be fresh as levels can be low.
The PyTest® procedure
The PyTest® has a special y designed gelatine capsule
Gastroscopy and biopsy can show inflammation and
containing maize starch microspheres impregnated by
the bacteria using special stains. Two antral biopsies are
14C urea. The radioactivity involved is tiny; we are all
general y recommended and the test has a 95 per cent
exposed to twice that amount of radiation through our
sensitivity and specificity.
normal environment each day.
The ‘rapid urease test' involves innoculation of
gastroscopy samples into a medium where pH indicators
change colour due to released ammonia. The test can
20mL of water. Three give a result within 20 minutes.
minutes is al owed then 20mL more
In patients for whom repeated therapy has failed, highly
water is swal owed
sensitive culture on mucosal biopsy can be used. The
culture takes seven days.
capsule is not lodged
dr Zhong Lu MBBS, FRCPA, PhD
in the oesophagus.
Dr Zhong is a Chemical Pathologist at Melbourne
After seven minutes,
Pathology and also works at Austin Health. She
the breath sample is
graduated from the Guangzhou Medical Col ege in
taken into a bal oon.
China then moved to Melbourne to study a Master of Human Nutrition at Deakin University. She
The microspheres are released within two minutes of
completed a PhD in Epidemiology and Preventive
entering the stomach and can easily penetrate the
Medicine at Monash University in 2001.
mucosal layer, al owing the test to operate reliably within 10 minutes. Tablets used in other tests take too
For further information, please contact one of our Specialist Pathologists:
dr Zhong Lu
long to dissolve and urea solutions don't penetrate
(pictured) MBBS, FRCPA, PhD - Chemical Pathologist
dr Rob Baird
the mucosal layer. Because urease is denatured at
MBBS, FRACP (Infectious Diseases), FRCPA (Microbiology)
Director of Microbiology
pH<5, it is only found in the lower levels of the mucous
Prof Prithi Bhathal MBBS, PhD, FRCPA - Histopathologist
layer. Urea is then broken down to ammonia and
dr Ken Sikaris MBBS, FRCPA, BSc(Hons), FAACB
bicarbonate. The bicarbonate freely diffuses into the
Director of Chemical Pathology
Melbourne Pathology ABN 63 074 699 139 A subsidiary of SONIC HEALTHCARE LIMITED103 Victoria Parade Col ingwood, Victoria 3066 Switchboard 9287 7700 www.mps.com.au Details correct at time of printing - February 2007
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