Causative organisms

An episode of CAPD peritonitis is usually caused by a single pathogen, Dr. Gokal said. The causative organism is often a gram-positive coccus originating from the normal flora of the patient’s skin. Coagulase-negative and coagulase positive Staphylococcus species account for more than 50% of cases of CAPD peritonitis. Gram-negative organisms most frequently associated with CAPD peritonitis are Escherichia coli and Pseudomonas aeruginosa.

 


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Severe CAPD peritonitis may be polymicrobial and involve a combination of anaerobic and gram-negative aerobic bacteria. CAPD peritonitis caused by anaerobic bacteria is often associated with intestinal perforation, whereas infection due to mycobacteria usually results from previous exposure. Fungal peritoneal infections are rare, and the most common cause of these infections is Candida species.

 

 

Although the rate of CAPD peritonitis has declined in recent years, evidence suggests that the proportions of cases due to gram-negative organisms and methicillin-resistant coagulase-negative Staphylococcus (CoNS) have increased, according to Dr. Gokal. Among patients with CAPD peritonitis due to CoNS, resistance to methicillin increased significantly from 18.4% in 1992-1993 to 41.7% in 2000-2001. In contrast, the incidence of methicillin-resistant S. aureus did not change significantly during this same period. Catheter removal rates are significantly higher in patients with CAPD peritonitis due to a single gram-negative organism (16.6%) compared with gram-positive CAPD peritonitis (16.6% vs. 4.8%).3

 

Persistent infection

Most patients with CAPD peritonitis show considerable clinical improvement within 48 hours of initiating therapy. Occasionally, symptoms may persist beyond 48 to 96 hours. Reevaluation is essential in patients with persistent signs and symptoms of CAPD peritonitis at 96 hours after the start of treatment. Specifically, fluid cell counts, Gram stain, and cultures should be repeated and the antimicrobial regimen reassessed. Antibiotic removal techniques may be useful in an effort to maximize culture yield.

 

Among the principal clinical concerns in patients with CAPD peritonitis and persistent signs and symptoms is the presence of intra-abdominal or gynecologic pathology requiring surgical intervention and the presence of mycobacteria, fungi, and other atypical organisms. In patients with persistent S. aureus CAPD peritonitis, the possibility of an underlying tunnel infection or intra-abdominal abscess should be considered. Ultrasonography and CT may reveal the presence of an occult abscess in such patients.

 

Catheter removal and surgical exploration should be considered in patients with CAPD peritonitis, Dr. Gokal said. Patients who have not improved clinically by 96 hours should be cultured for anaerobic bacteria. The optimal duration of anti-microbial therapy following catheter removal in patients with resistant CAPD peritonitis has not been established. Intraperitoneal urokinase is a simple and effective treatment that may help avoid the need for catheter removal and interim hemodialysis in patients with resistant CAPD peritonitis.