Influence of amoxycillin and cefaclor on the colonization resistance of oropharynx.

A randomized, double-blind, controlled trial was carried out to compare amoxycillin and cefaclor in the treatment of respiratory tract infections in general practice. Their effect on the microflora of the oropharynx, their clinical effectiveness, side-effects and the incidence of superinfections were monitored. Amoxycillin and cefaclor were given three times daily in a dosage of 375 and 250 mg, respectively, for 7 days. In 72 patients treated with amoxycillin, the oropharynx became colonized with resistant Gram-negative rods in 24, with Pseudomonas in 1, with Staphylococcus aureus in 3 and with yeasts in 2 patients. In 67 patients treated with cefaclor only 2 patients became colonized with Gram-negative rods. In the amoxycillin group, 5 superinfections developed within 4 weeks after treatment. No superinfection occurred after treatment with cefaclor. Clinically, cefaclor was more effective than amoxycillin and showed fewer side-effects.