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Comparative in vitro studies of cinoxacin, nalidixic acid, and oxolinic acid
Abstract:
Cinoxacin and nalidixic acid were found to be similar in in vitro activity against 138 Shigella isolates and somewhat less active than oxolinic acid on a weight basis. Cross-resistance developed when 10 shigellae were transferred on increasing amounts of the respective agent contained in Mueller-Hinton agar. Plate dilution studies of the effect of changes in agar pH on the minimum inhibitory concentration revealed that the antibacterial activity increased with decreasing pH. Protein binding investigations revealed a high degree of binding, with nalidixic acid > oxolinic acid > cinoxacin.
Insights
Cinoxacin and nalidixic acid show similar in vitro activity against Shigella, with oxolinic acid being more potent. Antibacterial activity increases as pH decreases, and protein binding varies among these quinolones.
Area of Science:
- Microbiology
- Pharmacology
Background:
- Shigella infections pose a significant public health challenge.
- Quinolone antibiotics, including cinoxacin, nalidixic acid, and oxolinic acid, are used to treat bacterial infections.
Purpose of the Study:
- To compare the in vitro activity of cinoxacin, nalidixic acid, and oxolinic acid against Shigella isolates.
- To investigate the development of cross-resistance and the impact of pH on antibacterial activity.
- To determine the protein binding characteristics of these quinolones.
Main Methods:
- In vitro susceptibility testing of 138 Shigella isolates.
- Cross-resistance studies using serial transfer on agar.
- Plate dilution method to assess the effect of pH on minimum inhibitory concentration (MIC).
- Protein binding assays.
Main Results:
- Cinoxacin and nalidixic acid demonstrated similar in vitro activity against Shigella, while oxolinic acid showed greater potency on a weight basis.
- Development of cross-resistance was observed between the tested quinolones.
- Antibacterial activity of the agents increased significantly with decreasing pH.
- Protein binding was highest for nalidixic acid, followed by oxolinic acid, and then cinoxacin.
Conclusions:
- Cinoxacin, nalidixic acid, and oxolinic acid exhibit varying in vitro efficacy and resistance patterns against Shigella.
- Environmental factors like pH critically influence quinolone activity, suggesting implications for therapeutic use.
- Differential protein binding may affect the pharmacokinetic and pharmacodynamic profiles of these antibiotics.