Managing recurrent otitis externa in dogs: what have we learned and what can we do better?

Abstract

Recurrent otitis externa is a common problem in dogs. Topical treatment for each flare is successful in the short term, but repeated cycles of inflammation and infection lead to chronic inflammatory changes, pain and aversion, and antimicrobial resistance. These make the flares more frequent and harder to control. Eventually, the changes become irreversible and require a total ear canal ablation/lateral bulla osteotomy or ablative laser surgery. Most ear canal surgery is avoidable if recurrent otitis is properly managed at an earlier stage. This requires a different mindset and approach to these cases, taking advantage of recent research and clinical findings. Most importantly, clinicians must appreciate that all recurrent ear infections in dogs are secondary. To achieve a good long-term outcome, it is essential that all the underlying factors in each case are diagnosed and managed using the primary, secondary, predisposing, and perpetuating framework. This means that the primary condition must be diagnosed and managed, the secondary infection treated, predisposing risks identified and corrected, and the perpetuating factors reversed. Treatment is in 2 phases: induction to get the ears in remission and then long-term maintenance therapy to prevent relapses. Treatment should be appropriate to each dog but will typically involve ear cleaning, topical antimicrobial therapy, and topical or systemic glucocorticoids. Novel treatments for infection and inflammation will offer additional options in the future. Understanding the triggers for recurrent otitis in dogs will help clinicians plan effective management regimens that will make a huge difference to the quality of life of their patients and their owners.

Microbiological Survey and Evaluation of Antimicrobial Susceptibility Patterns of Microorganisms Obtained from Suspect Cases of Canine Otitis Externa in Gran Canaria, Spain

“…S. pseudintermedius and other coagulase-positive staphylococci, Malassezia spp. and P. aeruginosa , Proteus spp., E. coli and beta-haemolytic streptococci are consistently described as the most common microorganisms found in cases of canine otitis externa [ 1 , 6 , 32 , 33 ]. Our results are in agreement with the current literature, as S. pseudintermedius (22.9%), M. pachydermatis (22.6%), P. aeruginosa (18.3%), E. coli (7.9%) and S. schleiferi (2.9%) were the most common microorganisms detected.…”

“…Canine otitis externa has relevant welfare implications, as it is frequently associated with discomfort and pain. In addition, if untreated or unproperly managed, it can lead to chronic changes that will enable the presence of more frequent ear infections, which can increase in severity and become refractory to classic drug-based treatments [ 6 ].…”

“…This resistant mechanism has also been described in the two most prevalent pathogens isolated in cases of canine otitis externa, Staphylococcus ( S .) pseudintermedius and M. pachydermatis [ 6 , 13 ]. Therefore, when treatment protocols for canine otitis externa are not adapted to the role of biofilm-producing microorganisms in the infection, the potential suboptimal use of antimicrobial treatments can facilitate the appearance of multidrug-resistant (MDR) microorganisms, one of the main threats to public health worldwide and a central concern for One Health initiatives [ 14 ].…”

“…The development of antimicrobial resistance (AMR) in bacteria and the emergence of MDR microorganisms has both animal welfare and public health connotations. Dogs carrying MDR pathogens have a higher risk of being involved in multiple failed treatment regimens [ 6 ] and in some cases can only be treated by using last-resort surgical procedures as the only therapeutic option. The public health, or One Health, concern associated with the presence of AMR and MDR pathogens lies in the zoonotic potential of some of the most common bacteria isolated from cases of canine otitis externa.…”

“…For example, the ability of some Pseudomonas (P.) aeruginosa isolates¸the most prevalent Gram-negative bacteria found in cases of canine otitis [2], to produce biofilms can reach up to 40%, leading to increases in the antimicrobial concentration needed for an effective resolution of the infection [12]. This resistant mechanism has also been described in the two most prevalent pathogens isolated in cases of canine otitis externa, Staphylococcus (S.) pseudintermedius and M. pachydermatis [6,13]. Therefore, when treatment protocols for canine otitis externa are not adapted to the role of biofilm-producing microorganisms in the infection, the potential suboptimal use of antimicrobial treatments can facilitate the appearance of multidrugresistant (MDR) microorganisms, one of the main threats to public health worldwide and a central concern for One Health initiatives [14].…”