Suppression of class C β-lactamase in Enterobacter cloacae by clindamycin

Clindamycin reduced not only the β-lactamase activity but also the MIC of ceftazidime in Enterobacter cloacae NUH10. In the presence of clindamycin, intracellular and extracellular the β-lactamase activities were only 10% and 50%, respectively, compared with the control. By immunocytochemical examinations, β-lactamase were located in the cytoplasmic space in the presence of clindamycin, whereas it was found in the periplasmic space when clindamycin was not present. Western blot analysis showed when a smaller quantity of proteins on the low-molecular side after treatment clindamycin. These findings suggested that clindamycin does not suppress the synthesis of β-lactamase in E. cloacae NUH10, but suppresses the secretion of cephalosporinase from the cytoplasmic space (precursor form) to the periplasmic space (mature form).