Effect of antimicrobial agents on the piliation of Pseudomonas aeruginosa and adherence to mouse tracheal epithelium.

The effect of subminimal inhibitory concentrations (sub-MICs) of antimicrobial agents on the adherence of Pseudomonas aeruginosa (pili+) to trachea mucosal cells, the first stage in the development of P. aeruginosa respiratory tract infections, was investigated. The adherence of P. aeruginosa to the cells of the lower respiratory tract using a model of acid-injured trachea in mice was observed by electron microscopy (transmission and scanning). When P. aeruginosa was cultured with 1/4 MIC of erythromycin, minocycline, clindamycin, ofloxacin or tobramycin at 37 degrees C for 4 hours, the number of pili was significantly reduced (P < 0.01), together with a significant reduction in the number of adherent bacteria at 1/4 MIC of erythromycin (P < 0.01). No suppressive effects of piperacillin or ceftazidime were obtained on the piliation and adhesion of P. aeruginosa. These findings indicate that sub-MICs of erythromycin reduce the adherence of P. aeruginosa to the tracheal mucosa, which may prevent the onset of P. aeruginosa respiratory tract infection.