A pilot study of the in vitro antimicrobial activity and in vivo residual activity of chlorhexidine and acetic acid/boric acid impregnated cleansing wipes.

BACKGROUND: Topical antimicrobials are recommended for first line treatment of surface and superficial infections in dogs. This is especially important given the increasing prevalence of antimicrobial resistant infections. Antimicrobial wipes have become popular, but there are a lack of controlled studies assessing their in vitro antimicrobial and in vivo residual activity. We aimed to assess the antimicrobial efficacy of two commercial antimicrobial wipes against frequently isolated pathogens. Ten clinical and one reference isolate each of meticillin-susceptible Staphylococcus pseudintermedius (MSSP), meticillin-resistant S. pseudintermedius (MRSP), Escherichia coli (EC), extended spectrum beta-lactamase (ESBL) producing E. coli (ESBL-EC), Pseudomonas aeruginosa (PA) and Malassezia pachydermatis (MP) were tested using a modified Kirby-Bauer technique. Each isolate was tested against 6 mm discs of chlorhexidine (CHX) and acetic acid/boric acid (AABA) wipes, and positive and negative controls either overnight (bacteria) or for 3 days (Malassezia). Healthy dogs were treated with the wipes and distilled water on a randomised flank (n = 5 each). Hair samples (1 cm; 0.1 g) taken at days 0, 1 and 3 were inoculated with an isolate of each organism. Zones of inhibition (ZI) were measured. RESULTS: All isolates produced confluent growth with AABA and control wipes, except for the cleansing wipes and MP (median ZI 12 mm; 95% CI 8.2-15.8). The median (95% CI) CHX wipe ZIs (mm) were: MP 48.0 (47.0-49.0), MSSP 15.6 (14.2-17.0), MRSP 14.0 (13.6-14.4), EC 13.6 (12.0-15.2) and ESBL-EC 10.0 (9.4-10.6). PA showed confluent growth. The differences between the bacterial isolates was significant (Kruskal-Wallis p < 0.0001; post-tests MSSP = MRSP = EC > EBSL-EC > PA). Confluent growth was visible with all the hair samples. CONCLUSION: CHX but not AABA showed in vitro efficacy against MSSP, MRSP, EC and MP. ESBL-EC were less susceptible and there was no activity against PA. There was no residual activity on hair. Additional studies are required to determine efficacy of these products in clinically affected patients.

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.