Detection of antibiotics residues in milk Antibiotics residues

Detection of antibiotics residues in milk

� Antibiotics residues in milk, particularly those in pencillin, are undesirable not only from the standpoint of health, but also because the presence of antibiotic residues in milk may lead to:

1. inhibit the desired growth of microorganisms in fermented dairy products. 2. Selling milk with antibiotics is illegal in many countries as it may have harmful effects on people, lead to allergic reactions in sensitive consumers 3. Development resistant strains of bacteria.

� Aim: To detect of antibiotic residues in raw milk � Equipment: 1. Milk sample 2. Nutrient agar 3. Sensitive bacteria for all kinds of antibiotics (Geobacillus stearothermophillus) 4. Paper disks

� Procedure 1. Prepare agar medium containing Geobacillus stearothermophillus 2. Dip the paper discs into the milk sample and place on the plate. 3. Incubate the plate for 24 h to 48 h at 37 C° � Results If there is antibiotic in the milk it will be inhibit growth of bacteria, produced a circle of inhibition around the disc.

� Early qualitative and quantitative tests were time consuming and because results were not available for several hours, not suited to screening of milk prior to receipt. �A number of manufactures now market test kits that enable the handlers to screen milk for drug residues prior to pick up and/or receipt at the milk plant.

� Classification 1. of antibiotics detection tests in milk: Test based on acid production by the lactic acid bacteria such as Streptococcus thermophiles and Lactobacillus bulgaricus. 2. Tests based on reduction of dyes e. g. Methylene blue, Resazurine and Tripheyltetrazolium chloride (TTC). 3. Test based on planting procedures (Growth inhibition tests) e. g. Cylinder plate method, Disc Assay method and Well Diffusion method. 4. Recent methods (e. g. Tests based on monoclonal antibody technology, p-enzyme test, Radioimmunoassay method).