Vancomycin and nisin A are effective against biofilms of multi-drug resistant Staphylococcus aureus isolates from human milk
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Date
2020-01
Authors
Angelopoulou, Angeliki
Field, Des
Pérez-Ibarreche, Mariana
Warda, Alicja K.
Hill, Colin
Ross, R. Paul
Journal Title
Journal ISSN
Volume Title
Publisher
PLOS
Published Version
Abstract
Human milk provides complete nutrition for infants and at the same time promotes the growth of specific bacteria in the infant gastrointestinal tract. Breastfeeding can often be discontinued due to mastitis which is an inflammation of the breast tissue. We isolated 18 Staphylococcus aureus strains from milk donated by healthy (n = 6), subclinical (n = 6), and mastitic (n = 6) mothers, two strains of which were VISA (Vancomycin Intermediate S. aureus). All tested strains (n = 12) were able to form biofilms. We then examined the impact of nisin A and vancomycin alone and in combination on biofilm formation and eradication of selected strains (n = 8). We observed strain-specific responses, with the combinatorial treatment at 1/4X MIC (for both singularly) significantly inhibiting biofilm formation for seven out of eight strains when compared with nisin A or vancomycin alone. None of the selected treatments were able to eradicate pre-formed biofilms. Finally, we selected two strains, namely a VISA (APC3814H) and a strong biofilm former (APC3912CM) and used confocal microscopy to evaluate the effects of the antimicrobial agents at 1X MIC on biofilm inhibition and eradication. All treatments inhibited biofilm formation of APC3814H but were ineffective in eradicating a pre-formed biofilm. Single treatments at 1X MIC against APC3912CM cells did not prevent biofilm formation whereas combination treatment caused increased death of APC3912CM cells. Finally, the combination treatment reduced the thickness of the pre-formed APC3912CM biofilm as compared with the single treatments.
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Keywords
Bacterial biofilms , Vancomycin , Staphylococcus aureus , Mastitis , Antibiotic resistance , Antimicrobials , Antibiotics , Milk
Citation
Angelopoulou, A., Field, D., Pérez-Ibarreche, M., Warda, A.K., Hill, C. and Ross, R.P. (2020) ‘Vancomycin and nisin A are effective against biofilms of multi-drug resistant Staphylococcus aureus isolates from human milk’, PLOS ONE,15(5), e0233284 (19pp). doi: 10.1371/journal.pone.0233284