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BACKGROUND: Over the last decade, use of acellular dermal matrix in both breast surgery and abdominal wall reconstruction has gained popularity. Because the body's ability to integrate ADM, they have been touted as resistant to infection. Although this has been the case in hernia repair, 3 recent meta-analyses have demonstrated an increased risk of infection when used for breast reconstruction. This may be due to the fact that some ADM products are actually not sterile, but instead are "aseptically processed."
METHODS: In order to test the sterility of ADM products, five separate 2x4cm samples of 13 different brands of ADM (Table 1) were sterilely cut into 1x1cm pieces and placed in liquid culture media for aerobic/anaerobic bacteria, acid-fast bacilli (AFB), and fungi. Standard culture media was incubated for 2 weeks and AFB for 6 weeks. The Biomerieux Vitek 2 system was used to identify organisms from positive cultures. Separate samples of the ADMs were fixed and processed for paraffin embedding and used for fluorescent in-situ hybridization (FISH) using a universal bacterial DNA probe EUB338 to detect any presence of bacterial DNA on the ADMs. FISH slides were evaluated with confocal microscopy. The Mann-Whitney U test was utilized with p<0.05 considered significant.
RESULTS: The following ADMs had positive cultures: AlloDerm (bacillus sp.), AlloDerm RTU (staph warneri), DermaMatrix (staph epidermidis), XCM biologic (bacillus sp., staph warneri), Flex HD (staph warneri), and SurgiMend (staph warneri, staph epidermidis). Of the positive cultures, 3 were from terminally sterilized ADMs, and 3 were from aseptically processed ADMs. Results of FISH demonstrated traces of bacterial DNA on all matrices except for Integra (Table 1, Figure 1). Number of bacteria per high-power field (HPF) on FISH ranged from 0 (Integra) to 13 (AlloDerm) with an average of 2.3. There were more bacteria per HPF in the aseptically processed group compared to the sterile group, although this did not reach significance (3.6 vs. 1.9, p=0.09).
CONCLUSION: Standard culture techniques of both sterile and aseptically processed ADMs yielded an equal amount of positive cultures, all of which were standard skin flora and could have been contaminants. FISH analysis demonstrated evidence of prior bacterial contamination on all ADMs with the exception of Integra. Whether these findings are correlated with clinical infections remains to be studied.
