Novel Quantitative Assay to Describe In Vitro Bovine Mastitis Bacterial Pathogen Inhibition by Non-<i>aureus</i> Staphylococci
Bruno Toledo-Silva,
Lisa Beuckelaere,
Anneleen De Visscher,
Chloë Geeroms,
Evelyne Meyer,
Sofie Piepers,
Damien Thiry,
Freddy Haesebrouck,
Sarne De Vliegher
Affiliations
Bruno Toledo-Silva
M-Team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Lisa Beuckelaere
M-Team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Anneleen De Visscher
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science, Agricultural Engineering, 9820 Merelbeke, Belgium
Chloë Geeroms
M-Team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Evelyne Meyer
Department of Veterinary and Biosciences, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Sofie Piepers
M-Team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Damien Thiry
Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine and Institute for Fundamental and Applied Research in Animals and Health (FARAH), University of Liège, 4000 Liège, Belgium
Freddy Haesebrouck
Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
Sarne De Vliegher
M-Team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium
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.
