Spread of resistance from food animals to man--the UK experience.

Since 1990 there have been dramatic increase in the occurrence multiply drug-resistant strains of zoonotic pathogens causing infections in humans in many developed countries. Of particular note has been the epidemic spread of MR strains of S. typhimurium DT 104, which now appear to have an almost world-wide distribution. Within DT104 the increasing spectrum of resistance is of considerable concern, with strains with decreased susceptibility to ciprofloxacin increasing in incidence in the United Kingdom and also causing serious disease in humans in other countries. For campylobacters the incidence of ciprofloxacin-resistant organisms is also increasing, with reports of such isolates from numerous countries throughout the world. For VTEC O157, although resistance is increasing, multiple resistance and resistance to ciprofloxacin remains rare. Drug resistance in food-borne pathogens is an unfortunate but almost inevitable consequence of the use of antimicrobials in food animals. Although for some pathogens--e.g., Campylobacter spp., the use of antimicrobials in human medicine is also an important factor (Smith el al 1999), it is the use of antimicrobials in food animals which has been a major factor in the development of decreased susceptibility to antibiotics such as ciprofloxacin in zoonotically-transmitted salmonellas. Such use is quite legitimate. However it is regrettable that recommendations such as propounded in 1992 in the UK by the Expert Group on Animal Feedingstuffs--the Lamming Committee, that any new antibiotics with cross resistance to those used in human medicine should not be used for prophylaxis in animal husbandry, were not accepted (Anonymous, 1992). Although the clock cannot be turned back, to combat the development of resistance to such important drugs as the fluoroquinolones it is hoped that a Code of Practice for their use in food animals will soon be internationally implemented.