Biofilm formation is an important cause of catheter-related infection. In hemodialysis, use of an antibiotic-lock has been proven to be effective to manage such a complication with preservation of the central venous catheter. In peritoneal dialysis, while biofilm has been implicated in relapsing and repeat peritonitis, both of which are caused by the identical bacteria as in their preceding peritonitis episode, no adjunctive measure has been proven to be effective to eradicate the biofilm bacteria. As a result, Tenckhoff catheter removal is the only recommended option for the patients suffering from relapsing or repeat peritonitis. In this study, the investigators are going to investigate whether the use of an antibiotic-lock can be useful to eradicate the biofilm in the Tenckhoff catheter to prevent future episodes of peritonitis caused by the same organism.

STUDY OBJECTIVES This study aims to evaluate whether the use of antibiotic-lock in the Tenckhoff catheter can eradicate the biofilm within the catheter lumen, thereby preventing further episodes of relapsing of repeat peritonitis without catheter removal.

METHODS Total 46 patients are to be recruited

When a PD patient, who has an episode of peritonitis treated successfully by IP antibiotics within the preceding 12 weeks, returns to the investigator's unit for peritonitis, the patient will be resumed on the same IP antibiotics treatment as in the last episode, while waiting for the PD effluent culture results. In the investigators' experience, the turnaround time of the microbiology report is usually 3-5 days. During this period, the patient should be closely monitored for the response to the antibiotics. The patient will be eligible for recruitment into this study if the same causative organism is confirmed subsequently. Another scenario is the absence of peritonitis symptoms, including PDE leukocyte count <100/mm3, yet there is a persistent growth of bacteria from the PDE after completion of 2-week antibiotic therapy. These patients are also eligible for study recruitment.

After recruitment, the subject will be randomized into either the intervention arm or the control arm in a 1:1 manner. In the control arm, appropriate IP antibiotics are to be continued. The dosage and duration of antibiotics will fully follow the recommendation from the latest International Society for Peritoneal Dialysis (ISPD) peritonitis guidelines. In the case of persistent bacterial growth from PDE without peritonitis symptoms, IP antibiotics will be extended up to 2 weeks more. In the intervention arm, in addition to the appropriate IP antibiotics, an antibiotic-lock will be prepared by the same antibiotics. The investigators will follow the suggested data used in hemodialysis catheter for the concentration of different antibiotics to prepare the locking solution

All antibiotics are diluted into an appropriate amount of normal saline or water to achieve the desired concentration. The resulting locking solution will be instilled precisely to fill up the Tenckhoff catheter and the transfer set once a day by the renal nurses. Prior to that, the existing PD solution is drained out first. As such, a "dry abdomen" is maintained during antibiotic-lock dwelling in the Tenckhoff catheter. This is to ensure the antibiotic-lock solution can be maintained within the catheter lumen for a prolonged period of time. After a 6-hour dwell, the antibiotic-lock is drained out and usual PD schedule is resumed. Such a daily application of antibiotic lock shall last until the course of IP antibiotics is completed.

RANDOMIZATION Randomization is carried out by drawing a consecutively numbered, sealed, opaque envelope containing a form indicating whether the subject is randomized into the intervention arm or control arm.

STUDY PARAMETERS The patients' demographics, including the age, gender, body mass index, PD vintage, etiology of end-stage renal disease, co-morbidities, together with the previous PD peritonitis history will be retrieved. The causative organisms of the current relapsing or repeat peritonitis are recorded.

After recruitment into the study and the peritonitis episode has been cured successfully, all subjects will be followed for up to 6 months after completion of their IP antibiotics treatment.

TERMINATION OF STUDY The subjects will be out from the trial when they have completed the study, or before the end of the study if their peritonitis is refractory to appropriate IP antibiotics rendering a need of timely Tenckhoff catheter removal, or at anytime the subjects decide to withdraw from the trial.

Inclusion Criteria:

• PD patients who suffer from Either relapsing peritonitis (within 4 weeks of completion of antibiotics) or repeat peritonitis (between 4 to 12 weeks of completion of antibiotics), in which the causative organism is confirmed to be identical to the one in the preceding peritonitis episode, or Persistent growth of bacteria from PD effluent (PDE) after completion of standard 2-week antibiotic treatment, despite the resolution of symptoms and PDE leukocyte count <100/mm3
• Age > 18 years old
• informed consent available

Exclusion Criteria:

• Patients who do not respond to the appropriate IP antibiotics, evident by the persistence of peritonitis symptoms in which they should be referred for timely Tenchkoff catheter removal
• Fungal or mycobacterial PD peritonitis
• Co-existing exit site or tunnel tract infection
• The presence of Tenckhoff catheter drainage dysfunction
• <= 3 years old
• Pregnant patients