A study on antibiotics residues in drinking milk sold in Istanbul

Antibiotics which are used in animals for treating, battening and similar purposes may leave residues in foods derived from these animals. The human consumption of such foods can cause serious health problems. Raw milk is one of the foods most likely to contain residues of antibiotics. The scope of this study is to determine possible residues of tetracycline and sulfonamide group antibiotics Doxycycline (DC), oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), sulfathiazole (ST), sulfaquinoxaline (SQX) sulphapyridine (SP), sulfamethoxazole (SMZ), sulfamerazine (SMZ), sulfadoxine (SDX) sulphadimethoxine (SDM), sulfadiazine (SD), sulfachloropyridazine (SCP), Sulfamethazin (SMT) in drinking milk samples collected from in Istanbul. For this purpose, 26 samples of raw milk, 30 samples of pasteurized milk belonging to different companies, 93 samples of UHT-treated milk, 149 samples in total, were collected within a year from various sales points. All were analyzed via LC-MS /MS in laboratory. Antibiotic residues have been detected in 16 out of analized raw samples, SMX, SQX, SDX in one sample, TC in 12 samples, OTC in 14 samples, DC in 6 samples, CTC in 6 samples, were detected. Other antibiotics residues were not observed. Antibiotic residues were detetected in 14 of pasteurized milk samples including OTC residue in all samples, SDX residue in 4 samples, SMT, SQX and CTC residues each in 2 samples and SDM residue in one sample. Antibiotic residues were detetected in 30 samples of UHT-treated milk, SMT residue in 14, SD residue in 9, SDM residue in 5, SDX and CTC residues in 4, OTC residue in 4, SMX and TC residues in 2, SQX residue in one sample. The highest number of antibiotic residues which were detected in the same sample for raw milk, pasteurized milk and UHT- treated milk specimens were 4,5 and 4 respectively. The most common residue detected within all samples was the residue of OTC with a highest concentration of 11.19 µg/kg. The highest concentartion among all the samples was detected as 13,76 µg/kg which belonged to DC residue. Although less type of antibiotic residues were present in raw milk samples, the concentration of the residues were observed to be higher compared to other type of samples. According to our analysis, aproximately half of the milk which were sold in Istanbul region contains tetracycline and sulfonamide group of antibiotic, however none of them are above 100µg/kg, which is the legally allowed upper limit. Our findings showed that analyzed samples were complying legal obligations. This indicates, drinking milk producers are showing sensitivity about the antibiotic residue content of their products introduced to the market. From another persipective, almost half of the milk samples contains antibiotic residue within legal limits. Especially with antibiotic residue inclusion of almost half of the milk, especially considered as given to consumption required purification time obtained before the milk from the given antibiotics to be relatively high animal values detected in raw milk.