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Vibrios are Gram-negative, curved, motile bacilli. There are more
than eight species; V. cholerae and V. parahaemolyticus being the
main human pathogens.
The organism is subdivided by the somatic O antigens; O1 and
O139 being the main types associated with cholera. They are able
to survive the gastric acidity, burrowing through the intestinal
mucus to attach to intestinal epithelial cells via the GM1 ganglioside
and produce a multimeric protein toxin (cholera toxin), which
stimulates adenyl cyclase within the enteric cells, resulting in the
secretion of water and electrolytes into the lumen of the bowel.
- Cholera is an exclusively human illness.
- It is transmitted via contaminated water and food.
- It is usually found in developing countries where there is inadequate
sanitation and an unsafe water supply.
- Epidemics are facilitated by war, refugee movements and mass
- Cholera gives rise to periodic pandemics: the most recent epidemic
was the seventh recorded.
The clinical features of cholera include:
- massive, painless, fluid diarrhoea (up to 20 L per day);
- severe dehydration and electrolyte imbalance.
However, it can be a mild or asymptomatic condition.
Where cholera is endemic, the diagnosis is based on clinical
features. Immobilization of cholera bacteria in a diarrhoeal
stool with specific antiserum yields a rapid diagnosis. The organism
can be cultivated on specialist medium. Biochemical identification
and serotyping should be performed to confirm the
Prevention and control
- Oral rehydration solution (salt and glucose mix).
- Intravenous fluids for severe cases.
- Tetracycline or ciprofloxacin can shorten the duration and
reduce the severity.
- Safe water supplies are the mainstay of prevention.
- Community education reduces spread.
- Experimental live attenuated and subunit vaccines are under
are associated with diarrhoeal disease and are the
commonest cause of intestinal infection. Although there are more
than 18 species of Campylobacter
, C. jejuni
is responsible for 90%
gastrointestinal infections. Infection follows
ingestion of contaminated meat, poultry, unpasteurized milk or
contaminated water. C. coli
causes bacteraemia in immunocompromised
invades and colonizes the mucosa of the
small intestine. Antibodies to GM1 ganglioside are associated with
- Influenza-like symptoms.
- Crampy abdominal pain.
- Diarrhoea, which may be blood stained.
- Children may be misdiagnosed as appendicitis or intussusception.
- Self-limiting bacteraemia is common.
- Guillain-Barr� syndrome, which is ascending demyelination
with motor and sensory deficits following a few weeks after Campylobacter infection, is a rare complication.
- Reactive arthritis may also occur.
- Culture of faeces, or other samples, on specialist medium.
- Identification by morphology and biochemical testing.
Diarrhoea is often self-limiting, but patients may be treated with
erythromycin or fluoroquinolones. An aminoglycoside may be
added for patients who have septicaemia.
Prevention and control
Prevention of campylobacteriosis depends on good animal husbandry
and abattoir practices, and on good food hygiene in shops,
dairies and the home.
Helicobacter pylori is a motile Gram-negative, spiral bacillus. H.
cinaedi and H. fennelliae have been isolated from patients with
HIV infection complicated by proctocolitis and bacteraemia.
Helicobacter pylori expresses urease, which raises the pH in the
surrounding locality, therefore protecting the bacterium from the
effects of gastric acid. The CagA pathogenicity island encodes a
type IV secretion system that injects the CagA protein into the host
cytoplasm, where subversion of a variety of cellular functions
occurs that results in IL-8 secretion and inflammatory cell recruitment.
VacA, a secreted protein that damages cells, is associated
with severe disease.
- Often asymptomatic.
- Chronic infection often takes the form of a low-grade gastritis.
- Strongly associated with both gastric and duodenal ulceration.
- Associated with an increased risk of gastric cancer.
- Culture or nucleic acid amplification test (NAAT) of gastric and
- Urease breath test.
- Stool antigen test.
- Serology, but this cannot distinguish between recent or old
- Proton pump inhibitor, clarithromycin and metronidazole or
- Specialist advice is required if resistance is suspected.
- Re-infection with H. pylori in adulthood is unusual.