Helicobacter pylori (H. pylori) is a gram-negative spiral flagellate microaerophilic bacterium found in the human gastric mucosa 1. It is classified as a Group I carcinogen and is considered necessary but insufficient alone to cause gastric adenocarcinoma. More often than not, it results in chronic gastritis and colonizes its host for decades.
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Epidemiology
Initially classified as Campylobacter pylori in 1982 by Dr Barry Marshall and Dr Robin Warren (Perth, Western Australia), it was subsequently reclassified under a new genus and was renamed Helicobacter pylori in 1989 1. In 2015, up to 4.4 billion individuals were found to be colonized by H. pylori worldwide 2. The African continent has the highest prevalence (79%) and the lowest in North America (37%) and Oceania (25%) 2. In highly developed and industrialized countries, there has been a trend of declining prevalence largely due to early detection and prompt treatment.
H. pylori related gastritis increases the risk of distal gastric cancer by 8-9 times. Up to 80% of gastric cancers in developed countries are related to H. pylori 3.
Microbiology
Gram-negative spiral bacteria with 2-6 sheathed flagella granting mobility and penetrability of the gastric mucosa. The principal reservoir is the stomach, particularly at the gastric antrum. This organism has adapted to the highly acidic environment of the stomach by containing a large urease enzyme which creates urease and an alkaline environment in which it can survive 1. Being a microaerophile, it thrives at O2 levels of up to 10% CO2 and a highly humid environment 3.
Pathogenesis
Heterogenous disease spectrum which is a complex interplay between the bacteria and the host determines the clinical presentation. Though previously thought that intestinal metaplasia (type 1-3) secondary to chronic active gastritis and atrophic gastritis was the main cause of dysplasia and cancer formation, this has been disproven in previous studies.
Associated conditions
Diagnosis
urea breath test
stool antigen test
stool polymerase chain reaction (PCR)
gastroscopy with biopsy (rapid urease test, culture and histology)
serum IgG and IgA (H. pylori)
Treatment and prognosis
Current recommended eradication regimens include 5:
PPI-based triple therapy: esomeprazole 20mg BD/omeprazole 20mg BD with amoxicillin 1g BD and clarithromycin 500mg BD (first line recommended for 7 days)
Quadruple therapy: omeprazole 20mg OD, bismuth 120mg QID, metronidazole 400mg TDS and tetracycline 500mg QID (less common, 7-14 days, first line in regions with known clarithromycin resistance)
As antibiotic resistance grows, newer therapies like sequential therapy and salvage therapy are gaining traction.
History and etymology
It is postulated to have migrated out of East Africa in the human host circa 60,000 years ago. Before its formal discovery in 1982, German scientists observed spiral bacteria in the gastric lining in 1875 but were unable to culture them6.
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