MICROBIOLOGICAL EVALUATION OF ANTIBIOTIC RESIDUES IN MEAT, MILK AND EGGS

Abstract

Microbiological tests are widely used to detect antibiotic residues in the meat, milk and eggs for better care of the quality and health safety. In the present study microbiological inhibition test i.e. Swab Test on Animal Food (STAF) was developed indigenously for screening of animal foods for presence of antibiotic residues. In this test local isolated culture of Bacillus subtilis was used as a test microorganism due to its high sensitivity to detect a wide range of antibiotics commonly used in animal disorders. The concentration of spore suspension of Bacillus subtilis JS2004 used in the formation of STAF plate was optimized at 2x107 spores/ ml. At this concentration, inhibition zone around Neomycin control disc was 10-16 mm. Nutrient agar was used as a medium in spore suspension and 0.4% dextrose was added as a constituent of medium. Zones of inhibition around swab samples and Neomycin control disc were observed and the diameter was measured. All swab samples showing a minimum of 2 mm wide inhibition zone around them were considered as positive for presence of antibiotic residues. The swab samples showing no zone of inhibition or a zone measuring less than 2 mm were considered as negative. Results of application of STAF test was on animal food samples revealed the high incidence of antibiotic residues.