EFFECT OF 6-FLUORO-8-METHOXY QUINOLONE (AM-1155) AGAINST CHRONIC AIRWAY INFECTION WITH PSEUDOMONAS-AERUGINOSA IN A RAT MODEL

We studied the effect of AM-1155, a newly developed quinolone, against chronic airway infection with Pseudomonas aeruginosa using a previous ly described rat model. AM-1155 (25 mg/kg) or ciprofloxacin (25 mg/kg) or saline (controls) were injected sc for 14 days (from day 4 to day 17) after the inoculation of agar beads containing P. aeruginosa. The number of viable cells of intrapulmonary P. aeruginosa, histological f indings of the lungs and immunoglobulin levels of serum and bronchoalv eolar lavage fluid were examined in rats 11 and 18 days after the trea tment. The findings indicated that the number of viable cells of P. ae ruginosa in lungs was significantly decreased in the AM-1155- or cipro floxacin-treated group compared with the non-treated control group. Hi stological examination in the non-treated control group showed hyperpl asia of bronchus-associated lymphoid tissue as well as cellular infilt ration in airways, but not prominently in the AM-1155- or ciprofloxaci n-treated group. The IgG and IgA levels in serum and bronchoalveolar l avage fluid were significantly lower in the AM-1155- and ciprofloxacin -treated groups than in the control group. These in-vivo effects of AM -1155 were comparable to those of ciprofloxacin. These findings sugges t that treatment with AM-1155 and ciprofloxacin suppressed excessive i mmune responses, preventing progression of airway damage in the chroni c infectious state.