The construction of bacteria that are capable of quorum-quenching S. aureus raises a series of safety issues regarding the researcher, patients/public, and environment. At the department where our research has been carried out, the Co-ordinator of Technical Support and Safety has approved the work with our project in light of the considerations below.
The actual work on constructing and expressing RIP in E. coli do not compromise researcher safety. However, examination of the effect of RIP on resistant S. aureus biofilm formation requires the use of pathogen and resistant S. aureus strains in the lab. This puts considerable demands on the researcher and the lab to ensure no spreading of resistant S. aureus. Fortunately, the University of Southern Denmark holds a class 2 laboratory for biological research in viruses and pathogenic bacteria only. When operated by trained researchers/students, this facility should meet the requirements to researcher safety.
In terms of public safety, distribution of the present RIP expressing E. coli via BactoBandage should not be a threat to the community – even though the bandage would be used for S. aureus infected and possibly weakened subjects. The E. coli strain has been chosen for research purposes because it is non-pathogenic, and so far RIP has not been observed to be toxic (which obviously has to be examined in detail). Nevertheless, mutations in the bacterial genome occur frequently and the emergence of pathogenicity over many generations cannot be excluded. As in all other cases where bacteria are used for production, this problem is solved by continuously replacing the highly replicating population with a “stock” population that has not been reproducing (e.g. kept at -80oC). This would also enable quality control to ensure that RIP expression is not lost.
Regarding environmental safety, disposal of viable, RIP-producing E. coli should be considered. The recently acquired ability of the E. coli to impair S. aureus biofilm formation would not obviously facilitate the spread of the coli bacteria in nature. However, frequent exposure of S. aureus to RIP, through extensive use of RIP or disposal of RIP-producing bacteria, would increase the risk of RIP-resistant staphylococcus to emerge (it should be noted however that even though a synthetic RIP has been studied for quite some time, there has yet to be noted any resistant strains in the litterature ) Even though resistance cannot be circumvented, exposure to RIP can be limited. In treatment, BactoBandage should be used only when necessary, and in combination with antibiotics, to avoid survival of exposed S. aureus. In nature, survival and spreading of RIP-producing E. coli can be avoided by using an auxotroph strain that is only able to survive during addition of certain organic compounds (e.g. certain amino acids).