Influence of carbon-dioxide tension and medium buffer concentration on medium pH and MIC values of erythromycin for Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 in a micro-aerobic atmosphere.
The effect of an elevated carbon-dioxide tension on medium pH and MIC determination with erythromycin for Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) was investigated in a micro-aerobic atmosphere, using an agar dilution method. During 30 h of incubation in an atmosphere containing approximately 6% CO2, 5% O2 and 89% N2, pH of uninoculated, as well as of seeded, blood agar plates decreased from 7.4 to 6.8. MIC values of erythromycin were two dilution steps higher after micro-aerobic incubation than after aerobic incubation. A decrease in agar pH during micro-aerobic incubation was eliminated by increasing the phosphate buffer concentration in the medium. However, MIC values of erythromycin remained high.
D000332:Aerobiosis; D002245:Carbon Dioxide / Q000494:pharmacology*; D003470:Culture Media; D004917:Erythromycin / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects*
D003470:Culture Media; D002245:Carbon Dioxide; D004917:Erythromycin