2.3. Sample collection

Samples of serum (≥ 1 mL) and dialysate (≥ 5 mL) were collected at 1, 2, 3, 5, 7, 10, and 14 days after complete instillation of the dialysis containing antibiotics into the peritoneal cavity. The serum samples were collected at 6 am. For patients treated with antibiotics twice (the modified group), samples were collected at the following times: DS4-08:00, DS1-12:00, DS2-16:00, DS3-20:00. DS4 and DS1 contained antibiotics. DS4 was retained in the abdominal cavity throughout the night from 20:00 the day before until 08:00, at which time the samples were collected. DS1 was retained in the abdominal cavity for 4 h before sample collection at 12:00. DS2 and DS3, which did not contain antibiotics, were retained in the abdominal cavity for 4 h. Serum samples were collected at 06:00, coinciding with the lowest level. For patients who were treated with antibiotics once (the traditional group), samples were collected at the following times: DS4-08:00, DS1-12:00, DS2-16:00, DS3-20:00. Only DS4 contained antibiotics. DS4 was retained in the abdominal cavity throughout the night from 20:00 the day before until 08:00, at which time the samples were collected. All collected samples were centrifuged at 1500×g and frozen at −80 °C within 1 h of collection.