Legally admissible amounts of antibiotics in milk affect the growth of lactic acid bacteria

The antibiotic administration in dairy livestock is a current widespread practice. The purpose of thestudy was to evaluate whether milk from antibiotic-treated animals, following the application of thewithdrawal time and fully complying with European requirements in relation to residue content,affected the development of lactic acid bacteria. Forty-five raw milk samples were collected afterthe withdrawal period and analysed to verify their compliance with the European maximum limitsusing four commercial screening tests. Lactobacillus delbrueckii subsp. bulgaricus growth and acidi-fying activity were delayed from 5 to 8 h in milk from cow treated with b-lactams and sulfonamidespresent in low concentration (cephalosporins < 15 lg/kg; penicillins < 8 lg/kg; sulfonami-des < 10 lg/kg) and their effect persisted over time. No influences were detected in Streptococcusthermophilus and Lb. helveticus development. The use of antibiotics can hamper the starter perfor-mances, opening questions about the safety of dairy pro