Characterisation of the effect of flavomycin on the rumen microflora

Flavomycin is a phosphoglycolipid antibiotic, which is used exclusively for the purpose of growth promotion. Existing data indicated that this antibiotic promoted growth in ruminants by a mechanism that differed from previously characterised antibiotics. Investigation of the effect of flavomycin on the ruminal flora was carried out using in vitro, in vivo and molecular techniques. Flavomycin suppressed ruminal populations of Fusobacterium necrophorum and other hyper-ammonia producing bacteria, increasing protein retention within the rumen. Restriction of ruminal numbers of F. necrophorum may also reduce the incidence of liver abscesses, as well as alleviating metabolic and immune burdens associated with this bacterium. Molecular analysis of the rumen bacterial population demonstrated several flavomycin-associated responses, although the recovery of multiple sequences from individual denaturing gradient gel bands prevented identification of the flavomycin sensitive bacteria. The majority of the microbial diversity detected by 16S rDNA analysis represented uncultured bacterial species, indicating the limited cultural representation of the bacterial diversity present within the rumen. From these results it was concluded that the growth promoting activity of flavomycin was due to the increased efficiency of dietary protein utilisation, although the role of uncultured bacteria is not clear. Characterisation of a flavomycin resistance mechanism and demonstration of its ability to confer cross-resistance to therapeutic antibiotics highlighted previous concerns regarding the use of antibiotics as feed additives. The ban on the use of flavomycin as a feed supplement, as of 2005, is a wise precautionary measure. It will contribute to ensuring the long-term efficacy of this class of antibiotics for future therapeutic application.EThOS - Electronic Theses Online ServiceGBUnited Kingdo