Sensi disc chloramphenicol

The assay was performed in accordance with a previously described protocol (Kissoyan et al. [52 (link)]) with some modifications. E. coli OP50 was grown in TSB overnight at 37°C under aerobic conditions, and C. acnes strains were grown in GAM broth for 3 days at 37°C under anaerobic conditions. For preparation of the mixed culture, each broth culture was further incubated with S. aureus overnight at 37°C under aerobic conditions. The optical density at 600 nm (OD₆₀₀) of the bacterial suspension was adjusted to 1.0 using TSB or GAM broth. Then, the culture was centrifuged at 69 × g for 5 min and the culture supernatant was filtered with a 0.45-μm syringe filter unit (Millex-HV) to obtain cell-free supernatant. Sterile 10-mm filter paper (Advantec, Japan) was inoculated with 50 μl of the filtered supernatant and placed on S. aureus-inoculated Mueller-Hinton plates. Sensi-Disc ampicillin 10 μg (Becton Dickinson, USA) and Sensi-Disc chloramphenicol 30 μg (Becton Dickinson, USA) were used as positive controls. The plates were incubated overnight at 37°C and visualized.

The assay was performed in accordance with a previously described protocol (Kissoyan et al. [52 (link)]) with some modifications. E. coli OP50 was grown in TSB overnight at 37°C under aerobic conditions, and C. acnes strains were grown in GAM broth for 3 days at 37°C under anaerobic conditions. For preparation of the mixed culture, each broth culture was further incubated with S. aureus overnight at 37°C under aerobic conditions. The optical density at 600 nm (OD₆₀₀) of the bacterial suspension was adjusted to 1.0 using TSB or GAM broth. Then, the culture was centrifuged at 69 × g for 5 min and the culture supernatant was filtered with a 0.45-μm syringe filter unit (Millex-HV) to obtain cell-free supernatant. Sterile 10-mm filter paper (Advantec, Japan) was inoculated with 50 μl of the filtered supernatant and placed on S. aureus-inoculated Mueller-Hinton plates. Sensi-Disc ampicillin 10 μg (Becton Dickinson, USA) and Sensi-Disc chloramphenicol 30 μg (Becton Dickinson, USA) were used as positive controls. The plates were incubated overnight at 37°C and visualized.