In vitroantimicrobial activity of a commercial ear antiseptic containing chlorhexidine and Tris-EDTA

Abstract

Minimum bactericidal concentrations (MBCs) of a commercial ear antiseptic containing chlorhexidine 0.15% and Tris-EDTA (Otodine) were determined by broth microdilution for 150 isolates representing the most common pathogens associated with canine otitis. The microorganisms were classified into three groups according to their levels of susceptibility. The most susceptible group included Staphylococcus pseudintermedius, Malassezia pachydermatis, Streptococcus canis and Corynebacterium auriscanis, which were generally killed by 1 : 64 dilution of the antiseptic product (MBC = 23/0.8 microg/mL of chlorhexidine/Tris-EDTA). The most resistant organism was Proteus mirabilis, which survived up to 1 : 8 dilution of the product (MBC = 375/12 microg/mL). Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus displayed intermediate MBCs ranging between 188/6 and 47/1.5 microg/mL. Interestingly, S. pseudintermedius was more susceptible than S. aureus, and no significant difference was observed between meticillin-resistant and meticillin-susceptible isolates within each species, indicating that antiseptic use is unlikely to co-select for meticillin resistance. Although the concentrations required for killing (MBCs) varied considerably with microorganism type, the combination of chlorhexidine 0.15% and Tris-EDTA was active against all the pathogens most commonly involved in canine otitis.

Study to assessin vitroantimicrobial activity of nine ear cleaners against 50Malassezia pachydermatisisolates

“…Variable in vitro activity between ear cleaners against a single M. pachydermatis isolate has also been reported . Our results support previous in vitro reports of anti‐ Malassezia activity of Epi‐Otic ® , Otodine ® and Sancerum ® . They also show antimicrobial action of two cleaners not previously assessed (Surosolve® and TrizUltra™ + Keto), and retained action of a reformulated ear cleaner (CleanAural Dog ® ).…”

“…As in other recent studies, it is difficult to conclude the exact reason for the extent of in vitro antimicrobial activity of the ear cleaners tested, because they varied widely in their ingredients; it is possible that individual components may potentiate each other.…”

“…This study was undertaken to investigate the in vitro activity of nine ear cleaners against 50 M. pachydermatis isolates. Antiseptics with activity against M. pachydermatis may offer an alternative to the use of polypharmacy drugs that contain antibiotics . Five of the ear cleaners analysed (Epi‐Otic ® , MalAcetic Aural ® , Otodine ® , Otoclean ® and Sancerum ® ) have previously been shown to have in vitro activity against M. pachydermatis .…”

In vitro antimicrobial activity of a gel containing antimicrobial peptide AMP2041, chlorhexidine digluconate and Tris‐EDTA on clinical isolates of Pseudomonas aeruginosa from canine otitis

“…Maintenance of activity at diluted concentrations is an important feature for antimicrobial agents used on the skin and in the ear canals. 19,20 A prior study of AMP2041 showed bactericidal effect against PA ATCC strain 27853 at an MBC value of 2.14 lg/mL after 2 h of contact time, 17 whereas reported MICs for chlorhexidine digluconate against PA range from 8 to >70 lg/mL. 21 Although Tris-EDTA alone is known to be bacteriostatic, its addition to topical products significantly lowers the MIC and MBC values for several antimicrobials.…”

Bacterial contamination of commercial ear cleaners following routine home use

“…Tris–EDTA by itself was ineffective against P. aeruginosa and S. intermedius in a recent study by Swinney et al. 7 When chlorhexidine, 7,27 benzyl alcohol, 28 lysozyme, 29 or sodium dodecyl sulfate 30 are added, however, efficacy is greatly improved, primarily against Pseudomonas . Only one of the solutions with an applicator tip contaminated with pathogenic bacteria contained Tris–EDTA.…”