A pilot study comparing in vitro efficacy of topical preparations against veterinary pathogens.

BACKGROUND: Topical antimicrobial agents are important for the management of cutaneous infections. For topical antimicrobial agents, in vitro efficacy data are limited. OBJECTIVES: To determine and compare the minimum bactericidal/fungicidal concentrations (MBCs/MFCs) of several topical antimicrobial agents against veterinary pathogens. MATERIALS AND METHODS: Two chlorhexidine, two oxychlorine based products (NaOCl & HOCl) lime sulfur (LS), manuka honey (MH) and hydrocortisone aceponate (HCA) were tested against American Type Culture Collection (ATCC) and clinical isolates: meticillin susceptible and resistant Staphylococcus pseudintermedius (MSSP), qac A/B carrying MSSP, antimicrobial susceptible and extended spectrum beta-lactamase producing Escherichia coli, multidrug-resistant Pseudomonas aeruginosa and Malassezia pachydermatis. The MBCs/MFCs were measured, where available, using a broth microdilution method; isolates were incubated for 3 and 10 min. RESULTS: Chlorhexidine and isopropyl alcohol (Chl(1) ) showed significantly lower MBCs (0.46 mg/L -937.50 mg/L, P = 0.027) compared to chlorhexidine and climbazole (Chl², 58.59 mg/L-1875 mg/L). NaOCl and HOCl showed excellent antimicrobial activity with HOCl having significantly lower MBCs compared to NaOCl (0.03 mg/L-1.72 mg/L and 0.03 mg/L-1.95 mg/L, respectively, P = 0.042). The detectable MBCs for LS and HCA were high, being close to the starting concentration (5,000 mg/L and 146 mg/L, respectively). The MBC/MFC for MH was not detectable. Amongst all test products there was no significant effect of contact time or isolate resistance status. CONCLUSIONS AND CLINICAL IMPORTANCE: Chlorhexidine, NaOCl and HOCl demonstrated low MBCs against tested organisms, suggesting potential in vivo efficacy. The selection of an appropriate antimicrobial agent, however, cannot be based exclusively upon MBC/MFC data; other factors should be considered.

Tris-EDTA significantly enhances antibiotic efficacy against multidrug-resistant Pseudomonas aeruginosa in vitro.

BACKGROUND: Multidrug-resistant Pseudomonas aeruginosa commonly complicates chronic bacterial otitis in dogs. HYPOTHESIS/OBJECTIVES: The aim of this in vitro study was to determine the effect of ethylenediaminetetraacetic acid-tromethamine (Tris-EDTA) on the minimal bactericidal concentrations (MBCs) and minimal inhibitory concentrations (MICs) of marbofloxacin and gentamicin for multidrug-resistant P. aeruginosa isolates from cases of canine otitis. METHODS: Eleven isolates were identified as multidrug resistant on disc diffusion; 10 were resistant to marbofloxacin and two were resistant to gentamicin. Isolates were incubated for 90 min with each antibiotic alone and in combination with Tris-EDTA at concentrations of 0.075 µg/mL to 5 mg/mL for marbofloxacin, 0.001 µg/mL to 10 mg/mL for gentamicin and 17.8:4.7 to 0.14:0.04 mg/mL for Tris-EDTA. Positive and negative controls were included. Aliquots of each antibiotic and/or Tris-EDTA concentration were subsequently transferred to sheep blood agar to determine the MBCs, and tryptone soy broth was added to the remaining suspensions to determine the MICs. RESULTS: Tris-EDTA alone was bacteriostatic but not bactericidal at any concentration. The addition of Tris-EDTA significantly reduced the median MBC (from 625 to 468.8 µg/mL; P < 0.001) and MIC (from 29.3 to 2.4 µg/mL; P = 0.008) of marbofloxacin, and the median MBC (from 625 to 39.1 µg/mL) and MIC (from 19.5 to 1.2 µg/mL) of gentamicin (both P < 0.001). CONCLUSIONS AND CLINICAL IMPORTANCE: Tris-EDTA significantly reduced the MBCs and MICs of marbofloxacin and gentamicin for multidrug-resistant P. aeruginosa in vitro. This may be of use to clinicians managing these infections in dogs.

Efficacy of a 0.0584% hydrocortisone aceponate spray in presumed feline allergic dermatitis: an open label pilot study.

This study evaluated the efficacy of a 0.0584% hydrocortisone aceponate (HCA) spray (Cortavance(®); Virbac SA) in 10 cats with presumed allergic dermatitis. The cats initially received two sprays/100 cm(2) of skin once daily. Clinical lesions (a Feline Dermatitis Extent and Severity Index; FeDESI), pruritus (10 cm visual analog scale with grade descriptors) and owner assessments of efficacy, tolerance and ease of use (from 1=very poor to 5=excellent) were assessed every 14 days. The frequency of treatment was reduced after day 28 in cats with a >50% reduction in FeDESI and pruritus scores. One cat was lost to follow up at day 28 and two at day 42. Intention-to-treat data were analysed. The FeDESI [mean (SD): day 0, 42.2 (15.7) and day 56, 9.9 (11.7); P<0.0001] and pruritus scores [day 0, 61.2 mm (20.1) and day 56, 14.6 mm (16.1); P<0.0001] significantly decreased throughout the trial. The owner scores for tolerance [median (range): day 14, 4 (1-5) and day 56, 4 (3-5); P=0.003] and ease of administration [day 14, 3 (2-5) and day 56, 4 (2-5); P=0.02] significantly increased during the trial, but there was no significant change in efficacy scores [day 14, 4 (3-5) and day 56, 4 (2-5); P=0.5]. There were no adverse effects attributable to the HCA spray, no significant changes in weight [mean (SD): day 0, 5.0 kg (1.4) and day 56, 5.0 kg (1.6); P=0.51] and no significant changes in haematology, biochemistry or urinalysis (n=4). Six cats required every-other-day treatment and four required daily treatment. In conclusion, HCA spray appeared to be effective and safe in these cats, although it is not licensed for use in this species.