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C S Lewin

Publications and source records attributed to C S Lewin.

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The bactericidal activity of DR-3355, an optically active isomer of ofloxacin.

The bactericidal activity of compound DR-3355, an optically active isomer of ofloxacin, was measured against Escherichia coli, Staphylococcus aureus and S. epidermidis, in nutrient broth and in phosphate-buffered saline. DR-3355 was found to be approximately twice as active as ofloxacin in terms of the concentration at which maximum bacterial kill was achieved. Hence it appears that DR-3355 is twice as active as ofloxacin not only in terms of its ability to inhibit bacterial multiplication but also in its ability to kill bacteria. DR-3355 was found to be active against non-dividing bacteria and did not require either active RNA or protein biosynthesis in order to kill bacteria.

Bacterial Proteins↗

Bactericidal mechanisms of ofloxacin.

Ciprofloxacin and ofloxacin are known to exert a second bactericidal mechanism (termed B) against Escherichia coli which functions even when protein synthesis is inhibited by chloramphenicol or when RNA synthesis is inhibited by rifampicin. However, the bactericidal activity of ciprofloxacin against a coagulase-negative staphylococcus (Staphylococcus warneri) was found to be abolished by chloramphenicol so the 4-quinolone does not exert mechanism B against this species. On the other hand, ofloxacin did exhibit mechanism B against S. warneri because the drug remained bactericidal in the presence of chloramphenicol. When S. aureus was investigated results similar to those observed in S. warneri were obtained throughout the range of clinically achievable concentrations of ofloxacin and ciprofloxacin. Ofloxacin seems to exhibit mechanism B against the staphylococci while ciprofloxacin does not. This may explain why ciprofloxacin is more potent than ofloxacin against Gram-negative bacteria but against staphylococci both drugs are equipotent.

Chloramphenicol↗