Medical Microbiology and Infection

at a Glance

Fourth EditionStephen Gillespie and Kathleen Bamford

Case Studies

Case 5

A traveller has returned from South East Asia on the overnight flight. They present to the emergency room and appear dehydrated. The patient vomits but the most prominent symptom is a large volume of watery diarrhoea. In view of the travel history you suspect an infectious cause.

  • 1. How do you investigate this?

    Stool cultures need to be sent for culture, ova and cysts. The laboratory should be informed that this is a returning traveller so that special media that will identify Vibrios as well as Salmonella and Shigella are used. The acute presentation means that parasites are less likely than bacterial causes of diarrhoea but may also be present in the returning traveller.

    A full blood count and C-reactive protein should be measured. Blood cultures should also be carried out if the patient is febrile.

  • 2. How does Vibrio cholerae cause disease?

    The main pathogenic determinant is vibrio toxin with five A subunits and one B subunit. The B subunit binds to the GM1 ganglioside on the gut epithelium and causes a rise in cAMP, which results in massive fluid secretion into the gut. The bacteria are also motile so are able to penetrate the mucus layer on the epithelium.

  • 3. How is cholera spread?

    Cholera is a human infection that is spread by contaminated food and water, primarily in parts of the world where there is inadequate sanitation and safe water. It can cause large epidemics (pandemics) especially where there is war with large-scale refugee movement.

  • 4. What other infections are associated with refugee camps and unsafe water supplies?

    Other gastrointestinal infections are likely. Enteric fever caused by Salmonella typhi and S. paratyphi as well as food poisoning strains of salmonella, campylobacter, shigella, E. coli and enteroviruses may all be prevalent. Respiratory infections will be able to spread, as will Neisseria meningitidis. Wound and skin infections may be more prevalent especially if war has been a driver for migration.

  • 5. How would you treat a patient with cholera?

    Oral rehydration solution (salt and glucose mix) is the mainstay of treatment. If the patient is severely dehydrated intravenous fluids may be required. Tetracycline or ciprofloxacin may shorten the course of infection.

  • 6. How could infection be prevented?

    A safe water supply is the key to prevention. This means that all useable and potable water should be separated from sewage management. There is currently no effective vaccine for cholera although several are in development.

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