DIHYDROSTREPTOMYCIN OR STREPTOMYCIN IN COMBINATION WITH PENICILLIN-G IN DAIRY-CATTLE THERAPEUTICS - A REVIEW AND REANALYSIS OF PUBLISHED DATA .2. RESISTANCE AND RESIDUES

Combination formulations of penicillin G salts and dihydrostreptomycin were developed during the 1960s and are currently marketed in New Zea land for parenteral and intramammary use in dairy cattle. In this pape r, the second part of a two paper series, the mechanisms by which bact eria develop resistance to each of these drugs independently is review ed and the impact of this resistance on potential for synergy is discu ssed. Further, the considerable potential for tissue drug residues wit h dihydrostreptomycin or streptomycin from these formulations is exami ned by re-analysis of literature data, demonstrating an urgent need to reassess the place for aminoglycoside-containing formulations in dair y cattle therapeutics.