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In vitro activity of an ear rinse containing tromethamine, EDTA, and benzyl alcohol on bacterial pathogens from dogs with otitis

Lynette K. Cole DVM, MS1, Dao H. Luu MS, DSA, MBA2, Paivi J. Rajala-Schultz DVM, PhD3, Cheyney Meadows VMD, PhD4, and Audrey H. Torres DVM, MS5
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  • 1 Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.
  • | 2 MDS Pharma Services, 865 MicheleBohec Blvd, Blainville, QC J7C 5J6, Canada.
  • | 3 Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.
  • | 4 Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.
  • | 5 Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.

Abstract

Objective—To evaluate the in vitro activity of an ear rinse (ER) containing tromethamine, EDTA, and benzyl alcohol on bacterial pathogens from dogs with otitis.

Sample Population—Organisms were collected from ear swab specimens from the external and middle ear and included Staphylococcus spp (n = 11; Staphylococcus intermedius [7] and Staphylococcus spp [4]), Pseudomonas aeruginosa (5), Proteus spp (5), β-hemolytic streptococcus (11), and 1 control strain of each organism.

Procedures—3 test solutions were evaluated including EDTA, tromethamine, and benzyl alcohol (ER); EDTA and tromethamine (ER without benzyl alcohol [ER – BA]); and purified water. Ten-milliliter aliquots of each test solution were transferred into 36 tubes and inoculated with one of the organisms. Samples were retrieved from each tube at 0, 15, 30, 45, and 60 minutes, transferred to Petri dishes, mixed with soybeancasein digest agar, and incubated. After incubation, plates were examined for growth, and the number of colonies was expressed as CFU per milliliter.

Results—ER significantly decreased bacterial growth in vitro of P aeruginosa and β-hemolytic streptococcal organisms within 15 minutes, Proteus spp within 30 minutes, and Staphylococcus spp within 60 minutes. Comparatively, the presence of benzyl alcohol in ER significantly decreased bacterial growth of β-hemolytic streptococcus and Proteus spp.

Conclusions and Clinical Relevance—On the basis of results of this study, future studies should be performed to evaluate the in vivo efficacy of ER alone as a treatment for otic infections caused by β-hemolytic streptococcus, P aeruginosa, and Proteus spp and of ER combined with an antimicrobial agent for otic infections caused by Staphylococcus spp.

Abstract

Objective—To evaluate the in vitro activity of an ear rinse (ER) containing tromethamine, EDTA, and benzyl alcohol on bacterial pathogens from dogs with otitis.

Sample Population—Organisms were collected from ear swab specimens from the external and middle ear and included Staphylococcus spp (n = 11; Staphylococcus intermedius [7] and Staphylococcus spp [4]), Pseudomonas aeruginosa (5), Proteus spp (5), β-hemolytic streptococcus (11), and 1 control strain of each organism.

Procedures—3 test solutions were evaluated including EDTA, tromethamine, and benzyl alcohol (ER); EDTA and tromethamine (ER without benzyl alcohol [ER – BA]); and purified water. Ten-milliliter aliquots of each test solution were transferred into 36 tubes and inoculated with one of the organisms. Samples were retrieved from each tube at 0, 15, 30, 45, and 60 minutes, transferred to Petri dishes, mixed with soybeancasein digest agar, and incubated. After incubation, plates were examined for growth, and the number of colonies was expressed as CFU per milliliter.

Results—ER significantly decreased bacterial growth in vitro of P aeruginosa and β-hemolytic streptococcal organisms within 15 minutes, Proteus spp within 30 minutes, and Staphylococcus spp within 60 minutes. Comparatively, the presence of benzyl alcohol in ER significantly decreased bacterial growth of β-hemolytic streptococcus and Proteus spp.

Conclusions and Clinical Relevance—On the basis of results of this study, future studies should be performed to evaluate the in vivo efficacy of ER alone as a treatment for otic infections caused by β-hemolytic streptococcus, P aeruginosa, and Proteus spp and of ER combined with an antimicrobial agent for otic infections caused by Staphylococcus spp.

Contributor Notes

Supported by IVX Animal Health Incorporated.

Presented in part at the 20th Annual Meeting of the North American Veterinary Dermatology Forum, Sarasota, Fla, April 2005.

Address correspondence to Dr. Cole.