The present invention provides a novel compound which has a wide antimicrobial spectrum, and in particular exhibits potent antimicrobial activity against beta-lactamase producing Gram negative bacteria. Specifically, the present invention provides a compound of the formula (I): wherein each symbol is as defined in the specification, or an amino-protected compound when the amino group is present on the ring in the 7-side chain, or a pharmaceutically acceptable salt thereof, and a pharmaceutical composition comprising the same.本發明提供一種新穎化合物,其具有廣泛之抗菌圖譜,特別是對產生β-內醯胺酶之革蘭氏陰性菌顯示出強烈抗菌活性。具體而言,本發明提供一種如式(I)所示之化合物、其7位側鏈之環上存在胺基時該胺基的保護體或其等在製藥上可接受之鹽以及含有其之醫藥組成物:(式中,各符號之意義係如說明書中所定義者)。
