ANTIMICROBIAL RESIDUES IN MILK AND SELECTED MILK PRODUCTS OF CHITTAGONG, BANGLADESH

Abstract

Antimicrobials are imprudently used in dairy cows for treating different infectious diseases and their indiscriminate use followed by unawareness about withdrawal periods leave antimicrobial residues in milk and milk products. A cross sectional study was conducted to determine antimicrobial residue in milk and selected milk products of Chittagong area and effect of heat on residue during the period of November 2013 to May 2014. For this, 280 milk samples from commercial and household dairy farms were collected from Chittagong Metropolitan Area and Patiya upazila of Chittagong district. Forty milk samples were collected from different milk distributing points of the city and also 50 samples from the available brands milk in Bangladesh. A total of 144 milk products sample including dahi, rasogolla and powder milk were collected from different brand’s showroom and grocery shops. A pretested questionnaire was also implemented for identifying the associated risk factors of prevalence of antimicrobial residue during sample collection from commercial farms. Both the milk and products samples were screened for antimicrobial residue by Thin Layer Chromatography and then confirmed by using Ultra High Performance Liquid Chromatography. The oxytetracycline and gentamicin residues were found in milk at higher percentages in commercial dairy farms. Categories of farm, cow illness, treatment given and antimicrobials used have significant (p ≤ 0.05) relationship on prevalence of antimicrobial residue in milk (18%). Five percent of the dairy products had antimicrobial residue including 4.2% dahi and 2.1% powder milk samples. But no antimicrobial residue was in rasogolla. The effect of heat on prevalence of antimicrobial residue in milk was insignificant (p > 0.05). The concentrations of amoxicillin (339.9μg/l) and oxytetracycline (195μg/l) residue were significantly (p ≤ 0.01) reduced by heat treatment. The amoxicillin and oxytetracycline residues were higher than the Maximum Residue Limit in milk and the ciprofloxacin residue in dahi (0.6μg/kg) was within the Maximum Residue Limit. However, most of the antimicrobials in milk were beyond the acceptable Maximum Residue Limit and assumed to causing serious public health threat. This work will contribute to understanding the levels of antimicrobial residue in milk and selected milk products as well as in taking measures regarding public health concerns.