RESUMEN
PURPOSE: In postoperative peritonitis, Gram stain examination (GSE) of peritoneal fluid has been proposed as a guide for the prescription of glycopeptides and antifungal therapy in empirical antibiotherapy. No data support this approach for Gram-positive cocci. We aimed to evaluate the performance of GSE in predicting the results of the culture of peritoneal fluid. METHODS: In this retrospective single-center study, concordance between GSE and culture of peritoneal fluid was assessed for different types of microorganisms. Factors associated with concordance of the two tests were evaluated in the subpopulation of Gram-positive cocci peritonitis. RESULTS: Among the 152 episodes, the GSE was negative in 57 cases. The negative predictive value and the positive predictive value were 41% and 87% for Gram-positive cocci (GPC), 31% and 86% for Gram-negative bacilli, and 78% and 94% for fungi. GSE is not a reliable guide for the choice of empirical antibiotherapy and cannot reliably rule out the presence of GPC at culture. If we aim to achieve a high rate of adequacy, the systematic use of glycopeptide in the empirical antibiotherapy may be considered. CONCLUSION: GSE shows poor performance to predict the results of culture of peritoneal fluid in postoperative peritonitis. Avoiding covering resistant GPC cannot be based on the result of GSE.