Descriptive analysis of microbiological data obtained from suspected cases of canine otitis externa in the island of Gran Canaria between 2020 and 2022

Abstract

Canine external otitis is the most prevalent otic disease in dogs. This condition arises from various causes, but microbial infection plays a key role. The objective of the descriptive analysis described as part of this final degree dissertation is to assess the presence of microorganisms associated with otitis externa in dogs from Gran Canaria, to provide updated data on the prevalence of these microorganisms and the occurrence of multidrug-resistant bacterial. For this purpose, a dataset from microorganism identification results and antibiograms obtained by a veterinary clinical diagnostic laboratory (Animal Lab, S.L.) was used. Out of the 604 suspected cases sent to the laboratory for analysis, a positivity rate of 78.1% (n=472) was observed. No statistically significant relationship between dog breeds or sex and increased susceptibility to otitis externa could be determined. A total of 42 different microorganisms were detected according to VITEK classification. The most frequent pathogens were Malassezia spp. (22.45%, n=132), Staphylococcus pseudointermedius (22.28%, n=131), Pseudomonas aeruginosa (18.71%, n=110), Proteus mirabilis (9.35%, n=55) and Escherichia coli (7.65%, n=45). Out of the 472 positive cases, 18% (n=85) were involved in coinfections. Malassezia spp. was present in 72.9% of these coinfections (n=62), followed by S. pseudintermedius (44,7%, n=38) and P. aeruginosa (27.1%, n=23) of presence in the coinfection cases. The coinfection of S. pseudintermedius and Malassezia spp. was the most common combination (31.7%, n=27). The antimicrobial sensitivity of the 4 most frequent pathogens and the levels of resistance to the most frequently used antimicrobials was also determined. The highest levels of resistance were observed for benzylpenicillin (62.63%, n=119) and ampicillin (60.43%, n=84). Multidrug-resistance phenotypes were observed in 34.9% (n=114) of the cases. These findings offer microbiologists and clinicians valuable, up-to-date insights into the causes and management of challenging cases involving multidrug-resistant bacteria, highlighting the relevance on antimicrobial resistance in veterinary medicine.