<p>There are provided new cephem compounds (synisomers) repsesented by the following general formula (I):
<Chemistry id="chema01" num="0001"><Image id="ia01" he="25" wi="102" file="IMGA0001.TIF" imgContent="chem" imgFormat="TIFF" inline="no" /></Chemistry>wherein R<Sup>1</Sup> means a lower alkyl group, R<Sup>2</Sup> denotes an ester-forming group of the carboxyl group, and the 4-methylthiazolyl group and the cephem moiety are cis to each other relative to the carbon-carbon double bond of the substituted vinyl group in the side chain at the 3-position of the cephem nucleus. The cephem compounds exhibit strong antibacterial activities not only against resistant strains of bacteria and gram-negative bacteria but also against gram-positive bacteria and moreover have very low toxicity.</p>
