Bacterial growth in saline implants: in vitro and in vivo studies

The survival of bacteria was evaluated in custom-made saline breast implants with integral injection ports in vitro and in 10 New Zealand White rabbits for Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Serratia marcescens. Pseudomonas and Serratia survived in vitro in saline-filled implants and multiplied 24-fold and 22-fold, respectively, from the initial inocula of 300 colony-forming units per cubic centimeter in 21 days. Serratia alone survived in saline implants placed on the dorsum of rabbits, proliferated 80-fold in 7 days, and tapered to 10-fold at the end of 3 weeks. Chemical analysis revealed the presence of glucose in fluid from the implants in the animal study (mean, 1.2 mg per deciliter; standard error of mean [SEM], 0.6) after 21 days and from human subjects (mean, 3.8 mg per deciliter; SEM, 1.0) after 8 months to 10 years. Serratia incubated in human breast implant fluid samples proliferated 7-fold to 30-fold greater than in the saline control in a nonaerated environment. We conclude that some bacteria are able to proliferate in saline in breast implants. Furthermore, their survival may be facilitated by a substance (i.e., glucose) that diffuses across the implant outer shell.