To obtain an antimicrobial agent having excellent stability to dehydropeptidase I, having a high recovery ratio in urine, low toxicity, capable of exhibiting excellent antimicrobial activity, useful for treating and preventing bacteriosis, etc., by including a specific tricyclic heterocyclic compound as an active ingredient.
This antimicrobial agent contains a compound of formula I {A is a group of formula II (R2 is H, a 1-4C alkyl or the like; R3 is H, oxo, sulfamoylaminomethyl or the like; (k) is 0 or 1; (m) is 0-2), a group of formula III [R9 is a phenyl (which may contain one to three of a 1-4C alkyl or the like); (q) is (m)], a group of formula IV [R10 is H or a 1-4C alkyl; R11 is R10 or the like; (r) is 0-3] or a group of formula IV [R12 is R10 or the like; R13 is a 1-4C alkyl containing 1-3 substituent groups such as a halogen or the like], its salt or derivative as an active ingredient. Preferably 10-2,000 mg of the antimicrobial agent is administered to an adult once to six times a day.
SUGANO OSAMU
KOBAYASHI SHINO
SHIMOJI YASUO
OYA SATORU
