Epidemiology of typhoid and multidrug-resistance in Asia

Abstract

Typhokl fever still poses a tremendous problem in developirrg countries, with aLmost 17 miLlion cases annually with 0.6 milliort deaths. Of these almost 75-80Vo of the cases and deaths occur in Asia alone, where th.e clisease is endemic. Although chloramphenicol resistance has been recognized since the early I 970s, definitive reports of emergence of strauts o/Salmonella typhi resistant to ampicillirt, chloramphenicol and trimethoprim-sulfa i.e. multidrug-resistant (MDR) typhoid, fl,rst appeared in 1987 from the Indian subcotxtirxent. Since then, MDR typhoid has been reported from other parts of Asia, including the Middle East and Soutlt East Asia. These MDR S.typhi isoLates have been resportsible for several outbreaks against a background of endemic typhoid because of the increasirxg ease of uttern.ational traveL, MDR typhoidal isolates have aLso been reported from Europe and North Anrcrica. Much of this resistance is l(:nown. to be mediated by relatively large plasmid.s belonging to the H I incompatibility group among of strains belongirtg b rhe VI phage types E} , Ml, Cl, O5-l and DI-N. Limited. amount of data on molecular'characterizafion o/ S.typhi strains from Papun New Guinea indicate limited genetic diversity with most isolates from fatal cases possessing the pulsed-field gel electrophoresis pattertt combination Xl Sl Al . Estimates of the relative proportiorr of MDR S.typhi isolates fron the Indian subcotttinent in recent r-ears lnve rangecl front 50-65%, posirtg considerable problems in therapy. A wide variety of therapeutic approaches have been tried, inclutlittg oral quinolones and third generation cephal.osporins. A worrying trend has been the recetxt emergence of S.typhi strains with chromosomal resistance to quinoLones, alnng with incresing report of delayed defervecence and treatment failure. A welcome lrend are the very recent rep.ort from Pakistan and India indicating a resurgetxce of chloramp