Resistance to Different Antibiotics
Campylobacter spp. have also shown increasing antimicrobial resistance in the past decade, and again much of this resistance appears related to the veterinary use of antibiotics. Although there is considerable geographic variation, macrolide resistance in C. jejuni, which is mainly due to mutational alteration of domain V of 23S rRNA, is increasing worldwide, including in Europe and the USA.94 C. coli shows higher erythromycin resistance rates (4–50%) than C. jejuni (0–20%). The proportion of isolates resistant to fluoroquinolones, which is caused by stepwise mutations in gyrA and/or parC genes, has increased dramatically around the world over the last 20 years (from 0% to over 80% in some areas). There is consistent evidence that this is a result of the addition of quinolones to chicken feed. In every country where this has been investigated, quinolone resistance in human Campylobacter isolates increased in frequency soon after the introduction of these drugs in animal husbandry, but long after their licensing in human medicine. In the USA, domestic chickens were determined by epidemiological and molecular investigations as the predominant source of quinolone-resistant C. jejuni infection in the years after these drugs were licensed for use in poultry in 1995. In South Africa, Thailand and Taiwan, very high rates of multiple resistance to quinolones, macrolides, tetracyclines and ampicillin often leave no effective antimicrobial treatment for Campylobacter enteritis.
