in a clinical isolate of serratia marcescens different states of low and high resistance to different beta-lactam antibiotics considered to be beta-lactamase-stable , viz . cefotaxime , ceftizoxime , ceftazidime , aztreonam , cefoxitin and imipenem , were found to be connected with the presence of constitutively overproduced , chromosomally encoded beta-lactamase at concentrations in the bacterial periplasm of 0.4 and 0.9 mm , respectively .
C0007554
cefotaxime
C0007560
ceftizoxime