Effect of residual doxycycline concentrations on resistance selection and transfer in porcine commensal Escherichia coli.
Int J Antimicrob Agents
; 51(1): 123-127, 2018 Jan.
Article
in En
| MEDLINE
| ID: mdl-28668675
ABSTRACT
Pig feed may contain various levels of antimicrobial residues due to cross-contamination. A previous study showed that a 3% carry-over level of doxycycline (DOX) in the feed results in porcine faecal concentrations of approximately 4 mg/L. The aim of this study was to determine the effect of residual DOX concentrations (1 and 4 mg/L) in vitro on selection of DOX-resistant porcine commensal Escherichia coli and transfer of their resistance plasmids. Three different DOX-resistant porcine commensal E. coli strains and their plasmids were characterised. These strains were each brought in competition with a susceptible strain in a medium containing 0, 1 and 4 mg/L DOX. Resistant bacteria, susceptible bacteria and transconjugants were enumerated after 24 h and 48 h. The tet(A)-carrying plasmids showed genetic backbones that are also present among human E. coli isolates. Ratios of resistant to susceptible bacteria were significantly higher at 1 and 4 mg/L DOX compared with the blank control, but there was no significant difference between 1 and 4 mg/L. Plasmid transfer frequencies were affected by 1 or 4 mg/L DOX in the medium for only one of the resistance plasmids. In conclusion, DOX concentrations of 1 and 4 mg/L can select for resistant E. coli in vitro. Further research is needed to determine the effect of these concentrations in the complex environment of the porcine intestinal microbiota.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Sulfadiazine
/
Trimethoprim
/
Chlortetracycline
/
Doxycycline
/
Drug Resistance, Bacterial
/
Escherichia coli
/
Animal Feed
/
Anti-Bacterial Agents
Limits:
Animals
Language:
En
Journal:
Int J Antimicrob Agents
Year:
2018
Document type:
Article
Publication country:
HOLANDA
/
HOLLAND
/
NETHERLANDS
/
NL
/
PAISES BAJOS
/
THE NETHERLANDS