Residues of Antibacterial Drugs

Published studies on the effect of storage and cooking on aminoglycoside residues are limited to streptomycin and neomycin. In most studies, streptomycin was shown to be fairly resistant to storage. No measurable loss of the antimicrobial activity of streptomycin residues in meat was observed after storage at either 4 C or 18 C for 14 days (1, 2). 

Cooking can cause some loss of the antimicrobial activity of streptomycin and neomycin, the loss being dependent on both the temperature and the matrix. When milk and water matrices were heated at 100 C for 30 min, the microbiological inactivation of neomycin was determined at 25% and 35%, respectively. 

Little or no loss of antimicrobial activity was further observed after fermentation of raw sausages containing streptomycin (6). However, smoking/scalding processes could cause a 32-45% reduction of the streptomycin activity (7). When semi- or fully preserved sausages were heated at 90-95 C for 1 h, the microbiological activity of the contained streptomycin exhibited a 50% reduction of the initial dose (8) however, some of the initial activity could be demonstrated in the juices exuded from the heated sausages even when the temperature was raised to 120-125 C. 

Neomycin residues were also found to be quite stable in chicken muscle extracts heated at 100 C for 5 h (9, 10). Unlike chicken muscle extracts, milk favored the loss of the contained neomycin when heated under similar conditions no more than 0-25% of the original activity could be determined after heating at 100 C for 5 h (9, 10). 

Use of piperonyl butoxide, a potent cytochrome P-450 inhibitor, has been recommended as an effective means for preventing the degradation of chloramphenicol. Since addition of this substance to liver homogenates could result in a recovery enhancement from about 30% to 60%, it was suggested that incurred tissue samples taken for analysis should be frozen immediately after excision and homogenized in water containing 2.5% piperonyl butoxide (11). 

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