In vitro antimicrobial resistance of Pseudomonas aeruginosa isolated from canine otitis externa in Rio de Janeiro , Brazil

Vet Pharm & Therapeutics

Page³

et al. 2019

Otitis 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.

Section: Introductionmentioning

confidence: 99%

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

Vet Pharm & Therapeutics

Page³

et al. 2019

“…Resistant pathogens often associated with canine OE are meticillin‐resistant Staphylococcus pseudintermedius (MRSP), multidrug‐resistant S. pseudintermedius (MDRSP) and MDR Pseudomonas aeruginosa (MDRPA) . Pseudomonas otitis has been reported with organisms demonstrating increasing fluoroquinolone resistance and multidrug resistance to at least three or four antimicrobial classes …”

Section: Introductionmentioning

confidence: 99%

“…4,5 Pseudomonas otitis has been reported with organisms demonstrating increasing fluoroquinolone resistance and multidrug resistance to at least three or four antimicrobial classes. 6,7 The emergence of antimicrobial resistance (AMR) is a global threat to both human and animal populations. 8 A significant public health risk was identified with increasing reports of AMR transmission between companion animals and humans.…”

Section: Introductionmentioning

confidence: 99%

In vitro antimicrobial activity of narasin and monensin in combination with adjuvants against pathogens associated with canine otitis externa

Khazandi

et al. 2019

Veterinary Dermatology

Background The emergence of antimicrobial resistance represents a serious human and animal health risk. Good antimicrobial stewardship is essential to prolong the lifespan of existing antibiotics, and new strategies are required to combat infections in man and animals. Hypothesis/Objectives To determine the in vitro interaction of ionophores (narasin or monensin) with antimicrobial adjuvants (N‐acetylcysteine (NAC), Tris‐EDTA or disodium EDTA) against bacterial strains representing pathogens associated with canine otitis externa (OE). Animal/Isolates American Type Culture Collection (ATCC) strains Staphylococcus aureus 29213, Pseudomonas aeruginosa 27853 and P. aeruginosa biofilm producer PAO1, and a clinical isolate of Proteus mirabilis from a case of canine OE were tested. Methods and materials A 2D microdilution checkerboard method was used, allowing calculation of fractional inhibitory concentration index (FICI), dose reduction index (DRI) and plotting of isobolograms. Results The combination of narasin with either Tris‐EDTA or disodium EDTA produced additive effects (FICI = 0.75) against P. aeruginosa ATCC 27853 and P. aeruginosa biofilm producer ATCC PAO1. An additive effect (FICI = 0.53–0.75) was found against S. aureus ATCC 29213 when narasin or monensin were combined with NAC. The highest DRI (32‐fold) was found with monensin/NAC where the MIC of monensin was reduced from 4 to 0.125 μg/mL. Conclusions and clinical importance The combination of narasin with Tris‐EDTA or disodium EDTA is a promising strategy to inhibit the intrinsic resistance elements of Gram‐negative bacteria. These novel combinations potentially could be useful as a multimodal approach to treat mixed infections in canine OE.

“…Micro‐organisms typically associated with OE are Staphylococcus pseudintermedius (formerly S. intermedius ), Pseudomonas aeruginosa , β‐haemolytic Streptococcus spp., Proteus mirabilis and Malassezia pachydermatis . Emergence of antimicrobial resistance has been described in a number of these bacterial species with increasing frequency, especially meticillin‐resistant Staphylococcus pseudintermedius (MRSP) which are often multidrug‐resistant to other antimicrobial classes, and multidrug‐resistant P. aeruginosa which often show resistance to at least three to four classes of antimicrobials …”

Section: Introductionmentioning

confidence: 99%

In vitro antimicrobial activity of narasin against common clinical isolates associated with canine otitis externa

Khazandi

et al. 2018

Veterinary Dermatology