Antibiotic advice based on an intra-operative Gram-stain during cholecystectomy

Intra-operative microscopy of the bile was performed during cholecystectomy in 335 patients. Based on the results, individual antibiotic advice was given. Bacteria were seen in the Gram-stained smear from 96 patients of whom 86 had a positive culture. In five patients a negative Gram-stain correlated with a positive culture (sensitivity 94.5%, specificity 95%, positive predictive value 89.5% and negative predictive value 97.5%). In only four patients (1.2%) did the antibiotic advice turn out to be wrong. Eight patients (2.4%) had signs of postoperative infection: one after wrong antibiotic advice, one who did not have prophylaxis because of false negative microscopy, four who did not have prophylaxis for clinical reasons but who had positive Gram-stains, and two despite apparently appropriate antimicrobial prophylaxis. An intra-operative Gram-stain as a guide to individual antibiotic advice given by a medical microbiologist during cholecystectomy is recommended.