[Persistance of streptomycin residues in the calf organism after parenteral therapeutic administration].

Streptomycin concentrations were determined in various calf tissues after i. m. administration of Streptomycin sulphate preparation of Rumanian provenience in the dose of l g pro toto using the biological diffusion method according to Gartside (1960). Spore suspensions of B. subtilis (ATCC 6633) and B. cereus var. mycoides (ATCC 11778) strains were employed as test organisms. B. subtilis was able to reveal considerably more residues. Another method using vegetative forms of the above microorganisms proved unsuitable for the tests. Two, three, five and ten days after the injection both slaughtered calves were positive, at 15 days only one of the two calves examined was positive, whereas at 20 days both calves were negative. Of the individual samples predominant majority of the findings come from the liver and from the spot of injection; residue findings from other tissues (bile, peritoneal muscles) are only sporadic. Skeletal musculature was negative in all cases except for the site of injection. In the samples from the injection site antimicrobial resudue activity was demonstrated in two cases following 1 month of freezing at -15 to -20 degrees C. For the tested preparation, a preslaughter withdrawal time of 20 days is recommended.