Principles for targeted antibiotic use in urinary tract and enteric infections: a review with special emphasis on norfloxacin.

Urinary tract infections (UTI) and bacterial enteric infections are caused by the aerobic faecal flora. In UTI that flora is spread via the urethra to the urine and in some cases also to the renal parenchyma. Dissemination from urine to blood resulting in septicaemia may occur. Treatment of UTI should be given with antibiotics that cause minimal ecological disturbances in the faecal flora, i.e. emergence of resistance and selection of resistant species which may cause reinfections, should be avoided. If an antibiotic does not cause diarrhoea, poor absorption from the gastrointestinal tract is to be preferred when UTI is treated since it will result in a reduction of the reservoir of bacteria capable of reinfecting the patient post-treatment. In enteric infections, the aetiology is bacterial in about 60% of the cases. Such infections is by far more common in the third world where it is a problem mainly in neonates, infants and children but also for travellers. Antibiotic treatment of diarrhoea with antibiotics like doxycycline, ampicillin or co-trimoxazole may cause rapid selection of resistant faecal Enterobacteriaceae, which in many cases are multiple resistant. This is also the case if antibiotics are used to prevent travellers' diarrhoea. The 4-quinolones offer a new approach to treatment of both UTI and enteric infections. Their wide antibacterial spectrum against aerobes and lack of activity against anaerobes is in this respect optimal. Moreover, some of them, e.g. norfloxacin and ciprofloxacin, are poorly absorbed and will markedly reduce the faecal aerobes without selecting other bacterial species. Norfloxacin has a well proven efficacy in UTI but remains to be proven in enteric infections.