Biofilm production by pathogens associated with canine otitis externa, and the antibiofilm activity of ionophores and antimicrobial adjuvants

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dc.contributor.authorChan, W.Y.
dc.contributor.authorHickey, E.E.
dc.contributor.authorPage, S.W.
dc.contributor.authorTrott, D.J.
dc.contributor.authorHill, P.B.
dc.date.issued2019
dc.description.abstractOtitis externa (OE) is a frequently reported disorder in dogs associated with secondary infections by Staphylococcus, Pseudomonas and yeast pathogens. The presence of biofilms may play an important role in the resistance of otic pathogens to antimicrobial agents. Biofilm production of twenty Staphylococcus pseudintermedius and twenty Pseudomonas aeruginosa canine otic isolates was determined quantitatively using a microtiter plate assay, and each isolate was classified as a strong, moderate, weak or nonbiofilm producer. Minimum biofilm eradication concentration (MBEC) of two ionophores (narasin and monensin) and three adjuvants (N-acetylcysteine (NAC), Tris-EDTA and disodium EDTA) were investigated spectrophotometrically (OD570nm ) and quantitatively (CFU/ml) against selected Staphylococcus and Pseudomonas biofilm cultures. Concurrently, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of planktonic cultures were assessed. 16/20 of the S. pseudintermedius clinical isolates were weak biofilm producers. 19/20 P. aeruginosa clinical isolates produced biofilms and were distributed almost equally as weak, moderate and strong biofilm producers. While significant antibiofilm activity was observed, no MBEC was achieved with narasin or monensin. The MBEC for NAC ranged from 5,000-10,000 µg/ml and from 20,000-80,000 µg/ml against S. pseudintermedius and P. aeruginosa, respectively. Tris-EDTA eradicated P. aeruginosa biofilms at concentrations ranging from 6,000/1,900 to 12,000/3,800 µg/ml. The MBEC was up to 16-fold and eightfold higher than the MIC/MBC of NAC and Tris-EDTA, respectively. Disodium EDTA reduced biofilm growth of both strains at concentrations of 470 µg/ml and higher. It can be concluded that biofilm production is common in pathogens associated with canine OE. NAC and Tris-EDTA are effective antibiofilm agents in vitro that could be considered for the treatment of biofilm-associated OE in dogs.
dc.description.statementofresponsibilityWei Yee Chan, Elizabeth E. Hickey, Stephen W. Page, Darren J. Trott, Peter B. Hill
dc.identifier.citationJournal of Veterinary Pharmacology and Therapeutics, 2019; 42(6):682-692
dc.identifier.doi10.1111/jvp.12811
dc.identifier.issn0140-7783
dc.identifier.issn1365-2885
dc.identifier.orcidChan, W.Y. [0000-0002-9415-9893]
dc.identifier.orcidHickey, E.E. [0000-0002-4862-503X]
dc.identifier.orcidTrott, D.J. [0000-0002-8297-5770]
dc.identifier.orcidHill, P.B. [0000-0002-7449-4897]
dc.identifier.urihttp://hdl.handle.net/2440/121482
dc.language.isoen
dc.publisherJohn Wiley & Sons
dc.relation.granthttp://purl.org/au-research/grants/arc/LP130100736
dc.rights© 2019 John Wiley & Sons Ltd.
dc.source.urihttps://doi.org/10.1111/jvp.12811
dc.subjectPseudomonas aeruginosa
dc.subjectStaphylococcus pseudintermedius
dc.subjectN-acetylcysteine
dc.subjectTris-EDTA
dc.subjectbiofilms
dc.subjectcanine otitis externa
dc.subjectionophores
dc.titleBiofilm production by pathogens associated with canine otitis externa, and the antibiofilm activity of ionophores and antimicrobial adjuvants
dc.typeJournal article
pubs.publication-statusPublished

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