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Zoom on starter lactic acid bacteria development into oxytetracycline spiked ovine milk during the early acidification phase

Paba, Antonio, Chessa, Luigi, Cabizza, Roberto, Daga, Elisabetta, Urgeghe, P. Paolo, Testa, M. Cecilia, Comunian, Roberta
International dairy journal 2019 v.96 pp. 15-20
Lactobacillus delbrueckii subsp. lactis, Lactobacillus helveticus, Streptococcus thermophilus, acidification, cheeses, ewe milk, food animals, human health, lactic acid, lactic acid bacteria, maximum residue limits, milk, oxytetracycline, pH, plate count, quantitative polymerase chain reaction
Residues of antibiotics used in food-producing animals can be excreted in milk, affecting the technological performance of starter lactic acid bacteria (SLAB). SLAB development and acidification performance was studied in thermised ovine milk spiked with oxytetracycline (OTC) at maximum residue limit (MRL, 100 μg kg−1), during the early acidification phase. Late milk acidification and lower lactic acid concentration revealed an antibiotic effect mainly after 6 and 7 h from inoculation, with a 6 h delay to reach pH 5.6; the delay in SLAB development was observed by BactoScan™, while viable counts were not affected. Real-time PCR evidenced OTC effect for Streptococcus thermophilus and Lactobacillus helveticus, not for Lactobacillus delbrueckii subsp. lactis. A statistically significant impact of the antibiotic was observed, even at the maximum residue limit, with possible repercussions in technological processing and in human health, due to an increase of its concentration in cheese.