7-(D Alpha -Amino- Alpha -(p-hydroxyphenyl)acetamido)-3-(1,2,3triazol-5-ylthiomethyl)-3-cephem-4 -carboxylic acid and its nontoxic, pharmaceutically acceptable salts exhibit highly desirable solubility in water, are efficiently absorbed on oral administration to provide relatively high and prolonged blood levels and are potent antibacterial agents useful in the treatment of infectious diseases in animals, including man, caused by many Gram-positive and Gram-negative bacteria. 7-(D- Alpha -Amino- Alpha -(p-hydroxyphenyl)acetamido)-3-(1,2,3triazol-5-ylthiomethyl)-3-cephem-4 -carboxylic acid is prepared, for example, by contacting methyl D-(-)- Alpha -amino- Alpha -(4hydroxyphenyl)acetate or an acid addition salt thereof with 7amino-3-(1,2,3-triazol-5-ylthiomethyl)-3-cephem-4-carboxylic acid or a salt thereof in aqueous solution in the presence of enzyme derived from a microorganism selected from the group consisting of Xanthomonas citri (IFO 3835), Acetobacter turbidans (ATCC 9325) and Pseudomonas melanogenum (IFO 12020).