We performed an in vitro study to determine whether certain bacteria may lyse a commercially available fibrin seal (Beriplast®, Behringwerke, Marburg, FRG). Fibrinogen solution was mixed with actively growing bacterial cultures, and thrombin was added. During 20 days of incubation at 37 °C complete lysis was observed with a number of different bacteria, however, at different rates. Complete lysis within 1–5 days was observed for the following species (number of strains in parentheses): Streptococcus faecalis (3), Pseudomonas aeruginosa (2), Serratia marcescens (2), and Serratia liquefaciens (1). Lysis was observed after 6–10 days for Enterobacter cloacae (2), Morganella morganii (2), Escherichia coli (2), S. marcescens (1), and Klebsiella pneumoniae (2). Lysis after 11–16 days was observed for Streptococcus pyogenes (2), S. faecalis (2), and Staphylococcus aureus (2). Rapid lysis was associated with the ability of the strain to liquefy gelatin, i.e. the production of a p