Intraphagocytic bactericidal activity of bacterial DNA gyrase inhibitors against Serratia marcescens

Addition of phenylbutazone (2 mg/ml) to 55 vol% of fresh defibrinated human blood permitted leukocytic ingestion of Serratia marcescens bacteria, but blocked phagocytic killing activity. The group A (phage tail) bacteriocin bA+ 16 served to kill extraphagocytic test bacteria. Five bacterial DNA gyrase inhibitors (ciprofloxacin, enoxacin, norfloxacin, nalidixic acid and pipemidic acid) revealed intraphagocytic bactericidal activity against ingested S. marcescens bacteria of three test strains; the extent of intraphagocytic activity of these drugs approximated that of rifampin. Following combination with unmodified defibrinated human blood (55 vol%), ciprofloxacin, enoxacin, norfloxacin and pipemidic acid yielded additive effects against 3 assay strains of S. marcescens and Escherichia coli strain ATCC 25922; nalidixic acid was inferior in this regard. These data might guide chemotherapy of parenchymatous urinary tract infections.