The bactericidal action of spectinomycin on Neisseria gonorrhoeae

Abstract

The in vitro bactericidal activity for gonococci of four different antibiotics, penicillin, tetracycline, kanamycin and spectinomycin at their appropriate peak serum concentrations was compared. Spectinomycin was much more rapidly bactericidal for gonococci than the other antibiotics tested; this contrasts sharply with the bacteristatic action of spectinomycin for Escherichia coli at concentrations as high as 1 mg/ml. This rapid bactericidal action may be advantageous for any attempts to eradicate penicillinase producing gonococci. Electron microscope studies showed that spectinomycin produces alterations in gonococcal surface morphology leading to lysis. No significant differences were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis between the outer envelope proteins of gonococci grown in the presence or absence of spectinomycin, but there was evidence of ultrastructural damage to the cytoplasmic membrane. It is suggested that spectinomycin may inhibit the synthesis of a critical cytoplasmic membrane protein leading to ultimate impairment of the osmotic integrity of the cell.