Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922
The bacterial susceptibility and the translocation of fluoroquinolones (FQs) are influenced by pH, since it determines the proportion of microspecies of the drug. Norfloxacin (NOR) and oxalic acid (AO) are antibacterial compounds. In this work, we evaluated the antibacterial activity of the NOR–AO c...
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MDPI AG
2022-11-01
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| author | Rosalía Ayala Gómez María Cecilia Becerra Graciela Pinto Vitorino |
| author_facet | Rosalía Ayala Gómez María Cecilia Becerra Graciela Pinto Vitorino |
| author_sort | Rosalía Ayala Gómez |
| collection | DOAJ |
| description | The bacterial susceptibility and the translocation of fluoroquinolones (FQs) are influenced by pH, since it determines the proportion of microspecies of the drug. Norfloxacin (NOR) and oxalic acid (AO) are antibacterial compounds. In this work, we evaluated the antibacterial activity of the NOR–AO combination on the <i>Escherichia coli</i> American Type Culture Collection 25922 strain using the checkerboard method. In addition, we analyzed the effect of pH on the NOR-AO combination. We determined the extent of NOR ionization equilibrium and calculated the apparent logP to establish the lipophilicity of NOR at the different pHs assayed. The minimum inhibitory concentration (MIC) obtained for AO and NOR was 1250 µg/mL and 0.25 µg/mL, respectively. The interaction of NOR–AO was indifferent to the concentrations tested (Fractional Inhibitory Concentration 1.12). However, an atypical behavior was observed in <i>E. coli</i> growth. We observed that at pH values below 5.8 and log D below −0.3, the cationic species of NOR predominates, decreasing its activity. As pH increased, the predominant species is zwitterionic with increased lipophilicity and restoration of NOR activity. Therefore, the acid conditions given by the presence of AO decreased the concentration of the neutral species of NOR and therefore the amount of drug capable of diffusing directly through the membrane. There is controversy in the literature regarding the mechanism of FQ translocation through the bacterial membrane; however, our results show that the pH of the medium is a determining factor that directly impacts the antibacterial activity. To deepen this study, we will continue testing new concentrations and combinations with other organic acids. |
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| last_indexed | 2024-03-11T06:06:49Z |
| publishDate | 2022-11-01 |
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| spelling | doaj.art-decc3fa3a1ac44afa4a40bac5f70fb0d2023-11-17T12:58:09ZengMDPI AGMedical Sciences Forum2673-99922022-11-011419910.3390/ECMC2022-13226Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922Rosalía Ayala Gómez0María Cecilia Becerra1Graciela Pinto Vitorino2Departamento de Farmacia y Centro Regional de Investigación y Desarrollo Científico Tecnológico, Facultad de Ciencias Naturales y Ciencias de la Salud, Universidad Nacional de la Patagonia San Juan Bosco, Km. 4, Comodoro Rivadavia 9000, ArgentinaDepartamento de Ciencias Farmacéuticas, Unidad de Investigación y Desarrollo en Tecnología Farmacéutica-Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba 5000, ArgentinaDepartamento de Farmacia y Centro Regional de Investigación y Desarrollo Científico Tecnológico, Facultad de Ciencias Naturales y Ciencias de la Salud, Universidad Nacional de la Patagonia San Juan Bosco, Km. 4, Comodoro Rivadavia 9000, ArgentinaThe bacterial susceptibility and the translocation of fluoroquinolones (FQs) are influenced by pH, since it determines the proportion of microspecies of the drug. Norfloxacin (NOR) and oxalic acid (AO) are antibacterial compounds. In this work, we evaluated the antibacterial activity of the NOR–AO combination on the <i>Escherichia coli</i> American Type Culture Collection 25922 strain using the checkerboard method. In addition, we analyzed the effect of pH on the NOR-AO combination. We determined the extent of NOR ionization equilibrium and calculated the apparent logP to establish the lipophilicity of NOR at the different pHs assayed. The minimum inhibitory concentration (MIC) obtained for AO and NOR was 1250 µg/mL and 0.25 µg/mL, respectively. The interaction of NOR–AO was indifferent to the concentrations tested (Fractional Inhibitory Concentration 1.12). However, an atypical behavior was observed in <i>E. coli</i> growth. We observed that at pH values below 5.8 and log D below −0.3, the cationic species of NOR predominates, decreasing its activity. As pH increased, the predominant species is zwitterionic with increased lipophilicity and restoration of NOR activity. Therefore, the acid conditions given by the presence of AO decreased the concentration of the neutral species of NOR and therefore the amount of drug capable of diffusing directly through the membrane. There is controversy in the literature regarding the mechanism of FQ translocation through the bacterial membrane; however, our results show that the pH of the medium is a determining factor that directly impacts the antibacterial activity. To deepen this study, we will continue testing new concentrations and combinations with other organic acids.https://www.mdpi.com/2673-9992/14/1/99norfloxacinoxalic acidpHlogP |
| spellingShingle | Rosalía Ayala Gómez María Cecilia Becerra Graciela Pinto Vitorino Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 Medical Sciences Forum norfloxacin oxalic acid pH logP |
| title | Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 |
| title_full | Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 |
| title_fullStr | Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 |
| title_full_unstemmed | Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 |
| title_short | Impact of pH on the Antibacterial Activity of Norfloxacin in Its Combined Use with Oxalic Acid against <i>Escherichia coli</i> ATCC 25922 |
| title_sort | impact of ph on the antibacterial activity of norfloxacin in its combined use with oxalic acid against i escherichia coli i atcc 25922 |
| topic | norfloxacin oxalic acid pH logP |
| url | https://www.mdpi.com/2673-9992/14/1/99 |
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