QUINOLONE RESISTANCE AND CAMPYLOBACTER SPP

Campylobacter are a frequent cause of diarrhoea in man. The in-vitro s usceptibility of all species to the fluoroquinolones and the good resp onse observed in early clinical trials has led to the proposal that th ese agents may be useful in the treatment of campylobacter enteritis a nd other more complicated campylobacter infections. However, fluoroqui nolone-resistant campylobacters have been reported in up to 50% of iso lates from man. The numbers of resistant isolates varies both between and within countries, factors associated with this include foreign tra vel, local usage of fluoroquinolones, especially in animal husbandry, and whether the microbiology laboratory tests for susceptibility to fl uorinated agents, or just nalidixic acid. Fluoroquinolone-resistant ca mpylobacter have emerged during therapy with fluoroquinolones and been responsible for treatment failure. The mechanism of resistance in mos t isolates is due to mutation in the gyr A (at threonine 86) gene whic h encodes the A subunit of DNA gyrase. The suggestion of cross resista nce to non-quinolone antibiotics, such as tetracycline and/or erythrom ycin, is probably explained by coincidental occurrence in isolates alr eady resistant to such drugs. The proposal that the veterinary use of fluoroquinolones has led to the selection of fluoroquinolone-resistant campylobacters in poultry which then enter the food-chain to infect m an has been viewed as controversial. In the UK fluoroquinolone were on ly licensed for this use in 1993; it will be interesting to see whethe r resistant isolates increase the number, thereby lending support for this hypothesis.