Abstract
In vivo study on selection of ESBL-producing Escherichia coli in the intestinal tract of pigs treated with extended-spectrum cephalosporins
Cavaco, LM1,2, Aarestrup FM2, Abatih, E1, Guardabassi, L1
- 1- Faculty of Life Sciences, University of Copenhagen, DK-1870 Frederiksberg C; Denmark
- 2- National Food Institute, Technical University of Denmark; DK-1790 Copenhagen V, Denmark
B-lactams including penicillins and extended-spectrum cephalosporins such as ceftiofur and cefquinome are widely used in pig production. In this study, pig experiments were used to compare the in vivo effects of different ß-lactam antibiotics on selection of ESBL-producing E. coli in the intestinal microflora .
Twenty female 8 week-old specific pathogen-free pigs were randomly allocated into 4 groups of 5 pigs each. All pigs were inoculated intragastrically with a blaCTX-M-positive Escherichia coli of porcine origin. Three groups were treated for three days with either amoxicillin (15mg/Kg BW SID IM), ceftiofur (3mg/Kg BW SID IM) or cefquinome (2 mg/Kg BW SID IM) whereas pigs in the control group were kept untreated. Faecal samples were collected from all pigs before inoculation (day 1) and following antibiotic treatment at day 4, 8, 15, 22 and 25. Total coliforms and cefotaxime-resistant coliforms were counted on MacConckey agar plates without and with 2mg/L cefotaxime, respectively. Selected cefotaxime-resistant colonies were identified as E. coli by biochemical testing and the presence of the gene was confirmed by PCR.
Surprisingly, all but one of the pigs carried cephalosporin resistant coliforms carrying blaCTX-M genes in the faeces prior to inoculation. Following treatment both relative and total numbers of cefotaxime-resistant E. coli were significantly higher in the two groups treated with cephalosporins compared to the control group and this trend persisted until the end of the experiment. In the group treated with amoxicillin an increase in the counts of cefotaxime-resistant E. coli was only observed at day 22 and 25. All selected isolates from the treatment groups were shown to carry blaCTX-M, therefore indicating selection of this gene during treatment.
Treatment with ceftiofur or cefquinome was shown to induce selection of ESBL-producing E. coli in the intestinal tract for at least 22 days after the end of treatment. The selective effects persisted for a period longer than the withdrawal times recommended for these antimicrobials (9 days for ceftiofur and 5 days for cefquinome). Treatment with amoxicillin seemed to have a less selective effect compared with the cephalosporins. Considering the critical importance of extended-spectrum cephalosporins in human medicine, their use in pig production should be carefully considered since selection of ESBL-producing E .coli in the intestinal microflora is likely to increase the risk of carcass contamination during the slaughtering process and the consequent risk of foodborne transmission to humans.
| Original language | English |
|---|---|
| Title of host publication | Ikke angivet |
| Number of pages | 1 |
| Publisher | INRA |
| Publication date | 2007 |
| Pages | 14 |
| Publication status | Published - 2007 |
| Event | Symposium on Antimicrobial Resistance in Animals and the Environment (ARAE - 2007) - Tours, France Duration: 17 Dec 2007 → 19 Dec 2007 Conference number: 2 |
Conference
| Conference | Symposium on Antimicrobial Resistance in Animals and the Environment (ARAE - 2007) |
|---|---|
| Number | 2 |
| Country/Territory | France |
| City | Tours |
| Period | 17/12/2007 → 19/12/2007 |
Keywords
- Former LIFE faculty
- E.coli
- ESBL
- CTX-M
- Pig
- ceftiofur
- cefquinome
- amoxicillin
- treatment