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The effect of chlortetracycline treatment and its subsequent withdrawal on multi‐resistant Salmonella enterica serovar Typhimurium DT104 and commensal Escherichia coli in the pig
Author(s) -
Delsol A.A.,
Anjum M.,
Woodward M.J.,
Sunderland J.,
Roe J.M.
Publication year - 2003
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1046/j.1365-2672.2003.02088.x
Subject(s) - salmonella enterica , microbiology and biotechnology , salmonella , serotype , escherichia coli , enterobacteriaceae , biology , chlortetracycline , antibiotics , bacteria , gene , biochemistry , genetics
Aims: To investigate the effect of a therapeutic and sub‐therapeutic chlortetracycline treatment on tetracycline‐resistant Salmonella enterica serovar Typhimurium DT104 and on the commensal Escherichia coli in pig. Methods and Results: Salmonella Typhimurium DT104 was orally administered in all pigs prior to antibiotic treatment, and monitored with the native E. coli . Higher numbers of S . Typhimurium DT104 were shed from treated pigs than untreated pigs. This lasted up to 6 weeks post‐treatment in the high‐dose group. In this group, there was a 30% increase in E. coli with a chlortetracycline minimal inhibitory concentration (MIC) > 16 mg l −1 and a 10% increase in E. coli with an MIC > 50 mg l −1 during and 2 weeks post‐treatment. This effect was less‐pronounced in the low‐dose group. PCR identified the predominant tetracycline resistance genes in the E. coli as tet A, tet B and tet C. The concentration of chlortetracycline in the pig faeces was measured by HPLC and levels reached 80 μ g g −1 faeces during treatment. Conclusion: Chlortetracycline treatment increases the proportion of resistant enteric bacteria beyond the current withdrawal time. Significance and Impact of the Study: Treated pigs are more likely to enter abattoirs with higher levels of resistant bacteria than untreated pigs promoting the risk of these moving up the food chain and infecting man.