Biofilm production of Pseudomonas spp. isolates from canine otitis in three different enrichment broths

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.