In vitro susceptibility of contagious ovine digital dermatitis associated Treponema spp. isolates to antimicrobial agents in the UK.
BACKGROUND
Contagious ovine digital dermatitis (CODD) is an important cause of infectious lameness in sheep in the UK and Ireland and has a severe impact on the welfare of affected individuals. The three treponemal phylogroups Treponema medium/Treponema vincentii-like, Treponema phagedenis-like and Treponema pedis spirochaetes have been associated with clinical CODD lesions and are considered to be a necessary cause of disease. There are scant data on the antimicrobial susceptibility of the treponemes cultured from CODD lesions.


OBJECTIVE
The aim of this study was to determine in vitro the miniumum inhibitory concentration/ minimum bactericidal concentration (MIC/MBC) of antimicrobials used in the sheep industry for isolates of the three CODD associated treponeme phylogroups T. medium/T. vincentii-like, T. phagedenis-like and T. pedis.


METHODS
Twenty treponeme isolates; from 19 sheep with clinical CODD lesions.


METHODS
A microdilution method was used to determine in vitro the MIC/MBC of 10 antimicrobial agents for 20 treponeme isolates (five T. medium/T. vincentii-like, 10 T. phagedenis-like and five T. pedis). The antimicrobials tested were penicillin G, amoxicillin, oxytetracycline, tilmicosin, lincomycin, spectinomycin, tylosin, tildipirosin, tulathromycin and gamithromycin.


RESULTS
The treponeme isolates tested showed low MICs and MBCs to all 10 antimicrobials tested. They were most susceptible to gamithromycin and tildipirosin (MIC90: 0.0469 mg/L), and were least susceptible to lincomycin, spectinomycin and oxytetracycline (MIC90: 48 mg/L, 24 mg/L and 3 mg/L, respectively).


CONCLUSIONS
These data are comparable to in vitro antimicrobial susceptibility data for treponemes cultured from bovine digital dermatitis lesions. Dependent on local licensing, penicillin and tilmicosin appear to be the best candidates for future in vivo studies.
Department of Epidemiology and Population Health, Institute of Infection and Global Health, The University of Liverpool, Leahurst Campus, Neston, Wirral, CH64 7TE, UK.
Joseph W
http://orcid.org/0000-0002-3684-0277
JW
Angell
Department of Infection Biology, Institute of Infection and Global Health, The University of Liverpool, Liverpool Science Park IC2, 146 Brownlow Hill, Liverpool, L3 5RF, UK.
Simon R
SR
Clegg
Department of Infection Biology, Institute of Infection and Global Health, The University of Liverpool, Liverpool Science Park IC2, 146 Brownlow Hill, Liverpool, L3 5RF, UK.
Leigh E
LE
Sullivan
Department of Epidemiology and Population Health, Institute of Infection and Global Health, The University of Liverpool, Leahurst Campus, Neston, Wirral, CH64 7TE, UK.
Jennifer S
JS
Duncan
Department of Epidemiology and Population Health, Institute of Infection and Global Health, The University of Liverpool, Leahurst Campus, Neston, Wirral, CH64 7TE, UK.
Dai H
DH
Grove-White
Department of Infection Biology, Institute of Infection and Global Health, The University of Liverpool, Liverpool Science Park IC2, 146 Brownlow Hill, Liverpool, L3 5RF, UK.
Stuart D
SD
Carter
Department of Infection Biology, Institute of Infection and Global Health, The University of Liverpool, Liverpool Science Park IC2, 146 Brownlow Hill, Liverpool, L3 5RF, UK.
Nicholas J
NJ
Evans
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D058066:Digital Dermatitis / Q000453:epidemiology / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology / Q000382:microbiology*; D014208:Treponema / Q000187:drug effects*; D014211:Treponemal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D006113:United Kingdom / Q000453:epidemiology
D000900:Anti-Bacterial Agents