Journal of Small Animal Practice • Vol 59 • April 2018 • © 2018 British Small Animal Veterinary Association
Journal of Small Animal Practice (2018) 59, 238–242
Accepted: 16 November 2017; Published online: 11 January 2018
A study to evaluate the primary causes
associated with Pseudomonas otitis in
Department of Dermatology , Rutland House Veterinary Hospital , Saint Helens , Merseyside , WA9 4HU , UK
Corresponding author email: email@example.com; firstname.lastname@example.org
: To evaluate the primary causes, age of onset and time from diagnosis of otitis to development
of Pseudomonas otitis in each case.
: Data from clinical records of 60 dogs were extracted to address the study
objectives. Pseudomonas otitis was diagnosed by clinical signs and positive culture.
: In total, 57 purebred dogs and three crossbreed dogs were included: 32 dogs had unilateral and
28 bilateral disease. Underlying primary causes of otitis were allergy (42), masses (8), endocrine disease
(7) and autoimmune disease (3). The mean age of onset of otitis (and subsequent time to development
of Pseudomonas otitis) in dogs with allergic otitis was 40 months (28 months), with endocrine disease
was 56 months (19 months) and masses 99 months (10 months).
: The most common primary causes of otitis in dogs with Pseudomonas infections
are, in decreasing frequency: allergies, masses, endocrine disease and autoimmune disease. Secondary
infections with Pseudomonas developed more quickly if there was a mass or autoimmune disease, as
compared with allergies and endocrinopathies.
There are numerous studies that describe the investigation and
therapy of Pseudomonas otitis ( Wooley & Blue 1975 , Foster
& Deboer 1998 , Martin Barrasa et al . 2000 , Nuttall & Cole
2007 , Wildermuth et al . 2007 , Paterson 2012 , Steen & Paterson
2012 ) but none that specifically consider the underlying primary
causes or age of onset of cases of otitis with secondary Pseudomo-
nas species infection. Common primary causes of otitis externa
have been well-described ( Paterson 2002 , Saridomichelakis et al .
2007 , Zur et al . 2011 ), but there are sparse data on dogs diag-
nosed with otitis to describe the most common primary causes
for Pseudomonas otitis. One study suggests that dogs with endo-
crine disease are more prone to infection with “rods” ( Zur et al .
2011 ), but no other link is made between primary cause and type
of secondary infection . The bacterial flora of the normal canine
ear is predominantly Gram-positive cocci ( Harvey et al . 2005 ).
Acute cases of otitis externa are most commonly associated with
Gram-positive organisms such as Staphylococcus species ( Grono
& Frost 1969 , Kowalski 1988 ). Chronic inflammatory change
within the ear canal leads to increased numbers of Gram-nega-
tive bacteria ( Grono & Frost 1969 , Sharma & Rhoades 1975 ),
but there is no information to suggest how long after the initial
onset of otitis Pseudomonas infection occurs. The purpose of this
retrospective study was to investigate the primary diseases most
commonly associated with Pseudomonas otitis and the time from
initial onset of otitis to development of Pseudomonas infection
for each of the underlying primary causes.
MATERIAL AND METHODS
The clinical records of a referral hospital in the northwest of Eng-
land were searched for all dogs that were presented with Pseudo-
monas otitis between January 2009 and December 2015. Cases
were only included if a detailed clinical history had been provided
by the primary care veterinary surgeon, which enabled the inves-
tigators to establish the age at which otitis was first diagnosed and