DNase I induced DNA degradation is inhibited by neomycin

Preparations of antimicrobials from biotechnological sources containing nuc leic acids may serve as vector for the dissemination of resistance genes. A n essential prerequisite for the acquisition of a new resistance phenotype in a transformational scenario is the availability of physically intact DNA molecules capable of transforming competent microorganisms. DNA is thought re, be an easy target for catabolic processes when present in the natural habitat of bacteria (eg. gastrointestinal tract, soil) due to the overall p resence of nucleolytic enzymes. Aminoglycoside antibiotics are known to dis play a strong affinity to nucleic acids rendering these compounds to be pri mary candidates for exerting DNA protective functions in the gastrointestin al tract when applied orally during antibiotic chemotherapy. Using a DNase I protection assay it could be demonstrated that neomycin B at a concentrat ion of 2 mM completely inhibited degradation of plasmid DNA in vitro. No in hibition of degradation was observed with streptomycin and kanamycin and th e non-aminoglycoside antibiotics oxytetracycline and ampicillin under ident ical assay conditions. Thus, neomycin preparations may be able to promote s tructural integrity of contaminating DNA-fragments in DNase-rich environmen ts.