Novel Quantitative Assay to Describe In Vitro Bovine Mastitis Bacterial Pathogen Inhibition by Non-aureus Staphylococci

Bruno Toledo-Silva, Lisa Beuckelaere, Anneleen De Visscher, Chloe Geeroms, Evelyne Meyer, Sofie Piepers, Damien Thiry, Freddy Haesebrouck, Sarne De Vliegher

Research output: Contribution to journalA1: Web of Science-articlepeer-review


In this paper, we describe a new quantitative method to evaluate and quantify in vitro growth inhibition of mastitis-related bacteria. Colony-forming units of Staphylococcus (S.) aureus (n = 10), Escherichia (E.) coli (n = 10), and Streptococcus (S.) uberis (n = 10) were quantified after their growth on top of layers of trypticase soy agar (TSA) containing six different concentrations (varying from 102 to 107 CFU/mL) of bovine non-aureus staphylococci (NAS), i.e., S. chromogenes (n = 3) and S. simulans (n = 3) isolates. Growth inhibition of the mastitis-related major bacterial pathogens, including E. coli, was confirmed by all NAS, an effect that varied highly among NAS isolates and was not evident from the semiquantitative method with which the new method was compared. By subsequent application of the new method on a larger set of 14 bovine NAS isolates, we observed that S. simulans and NAS originating from teat apices (especially S. epidermidis) required lower concentrations to inhibit both methicillin-sensitive (MSSA) (n = 5) and methicillin-resistant S. aureus (MRSA) isolates (n = 5) originating from milk. Therefore, the new assay is a promising tool to precisely quantify the intra- and inter-species differences in growth inhibition between NAS.
Original languageEnglish
Article number264
Issue number2
Publication statusPublished - Feb-2022


  • dairy cows
  • mastitis
  • growth inhibition
  • coagulase-negative staphylococci
  • Staphylococcus aureus
  • Escherichia coli
  • Streptococcus uberis

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