Editor—In Piddock’s editorial on fluoroquinolone resistance it was stated that Salmonella typhimurium with decreased susceptibility to fluoroquinolones and campylobacter resistant to fluoroquinolones have been isolated from animals and retail poultry.1 Unfortunately, information about the incidence of fluoroquinolone resistant S typhimurium and campylobacter from human infections was not provided, nor was there any reference to underlying epidemiological events leading to the development of resistance.
The Laboratory of Enteric Pathogens is the national reference centre for salmonellas from humans in England and Wales. Since 1990 the most common serotypes have been S enteritidis, S typhimurium, S virchow, and S hadar. These are primarily zoonotic in origin, and the main food animal reservoirs are poultry, cattle, and pigs. In 1996, 702 of 5849 (12%) isolates of S typhimurium were resistant to ciprofloxacin at 0.125 mg/l, a 12-fold increase since 1994.2 Of particular importance has been the increasing occurrence of ciprofloxacin resistance in phage type 104 (DT104) already resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracyclines, with 12% of DT104 resistant to ciprofloxacin in 1996 and 1997.3 This increase is subsequent to the licensing in 1993 of ciprofloxacin analogues for use in animal husbandry and is also reflected in food animals, with 78% of isolates of DT104 from turkeys, 31% from chickens, 11% from cattle, 5% from pigs, and 12% from sheep resistant to quinolones in 1997.4 Concern has been expressed about the therapeutic implications for humans of fluoroquinolone resistance in multiresistant DT104, and a lack of clinical response has recently been reported from Denmark in an outbreak of quinolone resistant DT104 associated with pork in which seven people were admitted to hospital—six were treated with fluoroquinolones and one died.5
The Laboratory of Enteric Pathogens is also the national reference centre for campylobacter species from humans, and of 5800 isolates referred in 1996 and 1997, 12% were resistant to ciprofloxacin at >8 mg/l, and a further 4% had a ciprofloxacin minimum inhibitory concentration of 0.5 mg/l. Ciprofloxacin resistance was most pronounced in Campylobacter coli, with 22% of isolates resistant.
The report from Denmark shows the clinical consequences for humans of the continuing use of fluoroquinolone antibiotics in food animals. A recent report by the House of Lords Select Committee on Science and Technology has recommended the rapid introduction of a code of practice on the use of fluoroquinolones in food animals. In light of the Danish experience, it is hoped that these recommendations will be rapidly implemented.
References
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