Susceptibility patterns of enteroaggregative Escherichia coli associated with traveller's diarrhoea: emergence of quinolone resistance

Enteroaggregative Escherichia coli (EAggEC) isolates were identified as a c ause of traveller's diarrhoea in 50 (9%) of 517 patients and their antimicr obial susceptibility was determined. Molecular epidemiological characterisa tion and investigation of the mechanisms of acquisition of quinolone resist ance among nalidixic acid-resistant EAggEC strains was performed. Seventeen (34%) of 50 patients needed antimicrobial therapy, because of persistence of symptoms in nine cases and the severity of symptoms in eight cases. Ampi cillin and tetracycline resistance was high, whereas chloramphenicol and co -trimoxazole showed moderate activity and amoxicillin plus clavulanic acid, nalidixic acid and ciprofloxacin showed very good activity. Resistance to nalidixic acid was demonstrated in three isolates, two from patients who ha d travelled to India. In all three strains the resistance was linked to mut ations in the gyrA gene alone or in both gyrA and parC genes. Although cipr ofloxacin shows excellent in-vitro activity and could be useful in the trea tment of traveller's diarrhoea in patients travelling abroad, it may not be useful in patients who have journeyed to India or to Mexico.