The emergence of antibiotic resistance in typhoid fever

Typhoid fever, caused by Salmonella typhi, causes over 20 million cases annually, with at least 700,000 deaths. The main burden of disease is in developing countries, particularly the Indian Subcontinent and South East Asia. However, cases in returning travellers, immigrants and refugees in developed countries are not uncommon. Drug resistance is fast becoming a major problem in the management of this infection. Chloramphenicol resistance became established globally in the S.Typhi population after 1972 on plasmids of incompatibility group IncH. Multi-drug resistance defined as resistance to the three first-line agents used to treat typhoid fever, namely chloramphenicol, ampicillin and co-trimoxazole, and acquired on the same plasmid type, has been endemic in most of South East Asia and the Indian Subcontinent for many years. Resistance data from many endemic areas are sparse and with the increasing problem of reduced sensitivity to the fluoroquinolone antibiotics, empirical choice of antibiotics may be difficult. We review the historical aspects of the development of resistance and the current data available on the epidemiology of antibiotic resistance in S.Typhi.