Background -Pseudomonas spp. are commonly isolated from dogs with clinical otitis and have been shown to produce biofilm. There is a paucity of studies demonstrating biofilm growth in veterinary medicine.Hypothesis/objectives -To compare biofilm production of Pseudomonas spp. isolated from dogs with otitis using three different enrichment broths at two different time points. Speciation was performed.Animals -One hundred isolates from 98 dogs with clinical otitis were assessed for biofilm production.Methods and materials -One hundred isolates were assessed for biofilm production using a microtitre plate assay. Biofilm production in Luria-Bertani Broth (LBB), Mueller-Hinton Broth (MHB) and Tryptic Soy Broth (TSB) were assessed after 18 and 24 h of incubation.Results -At 18 h, biofilm production was demonstrated in 87% of LBB, 91% of TSB and 93% of MHB grown isolates. By 24 h, this was 92% of LBB, 96% of TSB and 99% of MHB isolates. Biofilm production was significantly increased after 24 h incubation compared to 18 h. A significant difference was noted in biofilm production between LBB and MHB (P = 0.0349), but not between LBB and TSB (P = 0.3727) or MHB and TSB (P = 0.3687) at 24 h incubation. Two isolates were speciated as P. fluorescens and 98 as P. aeruginosa.Conclusion and clinical importance -Not all enrichment broths were equivalent to one another and 24 h incubation was superior to 18 h. Biofilm production was high in this population of Pseudomonas spp. isolates.

Ear cleaners with activity against Malassezia may help to reduce the unnecessary use of antibiotic-containing polypharmaceutical ear medications. This study shows that the use of a large number of isolates may provide a more accurate account of the in vitro activity of a product.

Topical treatment with ear cleaners is considered to be a valuable adjunct in the treatment of canine otitis that involves multi-antimicrobial-resistant organisms such as Pseudomonas spp. Where treatment with antimicrobials is not an option, the use of these preparations, as a sole form of therapy, may be effective in some cases. As a comparison with other similar studies looking at the activity of ear cleaners against bacterial isolates from otitis, this study uses isolates from 50 ears from 48 dogs providing a significant number of isolates for analysis.

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often appears to be associated with postsurgical wound infections, the great majority of MRSP isolates I see are in dogs and cats with skin problems, often following prolonged courses of antimicrobial therapy. In a letter to Veterinary Record (May 5, 2007, vol 160, pp 635-636), I and a colleague suggested that MRSP may pose a greater challenge to the control of opportunistic infection in animals than MRSA, and this would appear to be the case, not least because of the wider spectrum of antimicrobial resistance displayed by MRSP (Steen and Webb 2010). In that same letter, we also suggested that, should there be zoonotic transmission of MRSP to people, then the associated public health issues may be greater than those of MRSA, for reasons of drug resistance. Cases of potential zoonotic transmission are now in the literature (Stegmann and others 2010). In 2006, when I first began to collate data on the incidence of meticillin-resistant staphylococcal isolates in samples submitted from companion animals for bacterial culture and sensitivity, almost all of these were strains of MRSA, 100 per cent of which were recovered from post-surgical wound infection sites. In that same year I saw very few cases of MRSP. Between