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.


OBJECTIVE
To determine and compare the minimum bactericidal/fungicidal concentrations (MBCs/MFCs) of several topical antimicrobial agents against veterinary pathogens.


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
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.
Small Animal Veterinary Teaching Hospital, University of Liverpool, Leahurst Chester High Road, Neston, CH64 7TE, UK.
Maarja
M
Uri
Small Animal Veterinary Teaching Hospital, University of Liverpool, Leahurst Chester High Road, Neston, CH64 7TE, UK.
Laura M
LM
Buckley
Small Animal Veterinary Teaching Hospital, University of Liverpool, Leahurst Chester High Road, Neston, CH64 7TE, UK.
Louise
L
Marriage
Small Animal Veterinary Teaching Hospital, University of Liverpool, Leahurst Chester High Road, Neston, CH64 7TE, UK.
Neil
N
McEwan
Small Animal Veterinary Teaching Hospital, University of Liverpool, Leahurst Chester High Road, Neston, CH64 7TE, UK.
Vanessa M
VM
Schmidt
D000287:Administration, Topical; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects*; D017610:Calcium Compounds / Q000494:pharmacology*; D002710:Chlorhexidine / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects; D006722:Honey; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008290:Malassezia / Q000187:drug effects*; D010865:Pilot Projects; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013210:Staphylococcus / Q000187:drug effects; D013440:Sulfides / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D000893:Anti-Inflammatory Agents; D017610:Calcium Compounds; D013440:Sulfides; C033907:calcium sulfide; C063919:hydrocortisone aceponate; D002710:Chlorhexidine; D006854:Hydrocortisone