title: Impact of the use of β-lactam antimicrobials on the emergence of Escherichia coli isolates resistant to cephalosporins under standard pig-rearing conditions.
abstract: The aim of this study was to evaluate if the treatments with ceftiofur and amoxicillin are risk factors for the emergence of cephalosporin resistant (CR) E. coli in a pig farm during the rearing period. One hundred 7-day-old piglets were divided into two groups, a control (n = 50) group and a group parenterally treated with ceftiofur (n = 50). During the fattening period, both groups were subdivided in two. A second treatment with amoxicillin was administered in feed to two of the four groups, as follows: group 1 (untreated, n = 20), group 2 (treated with amoxicillin, n = 26), group 3 (treated with ceftiofur, n = 20), and group 4 (treated with ceftiofur and amoxicillin, n = 26). During treatment with ceftiofur, fecal samples were collected before treatment (day 0) and at days 2, 7, 14, 21, and 42 posttreatment, whereas with amoxicillin, the sampling was extended 73 days posttreatment. CR E. coli bacteria were selected on MacConkey agar with ceftriaxone (1 mg/liter). Pulsed-field gel electrophoresis (PFGE), MICs of 14 antimicrobials, the presence of cephalosporin resistance genes, and replicon typing of plasmids were analyzed. Both treatments generated an increase in the prevalence of CR E. coli, which was statistically significant in the treated groups. Resistance diminished after treatment. A total of 47 CR E. coli isolates were recovered during the study period; of these, 15 contained blaCTX-M-1, 10 contained blaCTX-M-14, 4 contained blaCTX-M-9, 2 contained blaCTX-M-15, and 5 contained blaSHV-12. The treatment with ceftiofur and amoxicillin was associated with the emergence of CR E. coli during the course of the treatment. However, by the time of finishing, CR E. coli bacteria were not recovered from the animals.
authors.affiliation: Centre de Recerca en Sanitat Animal, UAB-IRTA, Barcelona, Spain.
authors.forename: Karla
authors.initials: K
authors.lastname: Cameron-Veas
authors.affiliation: Centre de Recerca en Sanitat Animal, UAB-IRTA, Barcelona, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Solà-Ginés
authors.affiliation: Centro de Vigilancia Sanitaria Veterinaria, Universidad Complutense de Madrid, Madrid, Spain Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Moreno
authors.affiliation: Universidad de Lleida, Departamento de Producción Animal, Lleida, Spain.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Fraile
authors.affiliation: Centre de Recerca en Sanitat Animal, UAB-IRTA, Barcelona, Spain Institut de Recerca i Tecnologia Agroalimentàries, Barcelona, Spain Lourdes.migura@cresa.uab.cat.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Migura-Garcia
mesh_terms: D000658:Amoxicillin / Q000008:administration & dosage / Q000494:pharmacology; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002511:Cephalosporins / Q000008:administration & dosage / Q000494:pharmacology*; D004363:Drug Utilization; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D005243:Feces / Q000382:microbiology; D005838:Genotype; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D010957:Plasmids / Q000032:analysis; D013552:Swine; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D000658:Amoxicillin; C053503:ceftiofur