Usefulness of Gram stain examination of peritoneal fluid in postoperative peritonitis to guide empirical antibiotherapy

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Surgical Infections

Background:

• Postoperative peritonitis management often involves empirical antibiotic therapy.
• Gram stain examination (GSE) of peritoneal fluid is proposed to guide initial antibiotic choices, including glycopeptides and antifungals.
• Evidence supporting GSE for guiding therapy against Gram-positive cocci is lacking.

Purpose of the Study:

• To evaluate the diagnostic performance of Gram stain examination (GSE) in predicting peritoneal fluid culture results.
• To assess the utility of GSE in guiding empirical antibiotic therapy for postoperative peritonitis.

Main Methods:

• Retrospective single-center study analyzing 152 episodes of postoperative peritonitis.
• Assessed concordance between GSE and peritoneal fluid cultures for various microorganisms.
• Evaluated factors influencing concordance, particularly for Gram-positive cocci peritonitis.

Main Results:

• GSE demonstrated poor predictive value for peritoneal fluid culture results.
• Positive predictive values were 87% for Gram-positive cocci (GPC), 86% for Gram-negative bacilli, and 94% for fungi.
• Negative predictive values were 41% for GPC and 31% for Gram-negative bacilli, indicating low reliability.

Conclusions:

• GSE is not a reliable tool for guiding empirical antibiotherapy in postoperative peritonitis.
• The results of GSE cannot reliably exclude the presence of Gram-positive cocci in peritoneal fluid cultures.
• Systematic empirical use of glycopeptides may be considered to ensure adequate coverage for resistant Gram-positive cocci.