Molecular Diagnosis Of Enteric Fever: Progress And Perspectives

Enteric fever is a severe systemic Gram-negative bacterial infection caused by several serovars of Salmonella enterica subspecies enterica, including S. Typhi and S. Paratyphi serotypes A (most commonly), B and C. It is characterised by high fever and a myriad of other non-specific features, including abdominal pain and constipation, headache, myalgia and arthralgia, cough, lymphadenopathy and rash. S. Typhi, the human-specific causative agent of typhoid fever, is thought to account for an estimated 21 million new cases and 216,000 deaths every year (Crump et al., 2004). S. Typhi is generally transmitted in food and water contaminated with faeces from those excreting bacteria, either during the acute illness or during chronic asymptomatic carriage, although infection of health-care or laboratory workers through poor hygiene practices or accidental exposure is also described. Transmission in regions with adequate sanitation and sewage facilities is uncommon as, in general, a relatively high inoculum is required to survive the gastric acid environment and cause infection. Enteric fever is therefore most common in resource-poor settings where the provision of clean drinking water and sewage disposal facilities is inadequate. South and Central Asia, Africa and South and Central America are considered endemic for this disease and particularly high incidence rates are found in the Indian sub-continent and South-east Asia, with rates exceeding 100 per 100,000 population per year (Bhan et al., 2005). In other countries typhoid fever remains an important consideration for travellers both preand post-travel (Levine et al., 1982; Ackers et al., 2000; Bhan et al., 2005).