TY - JOUR

T1 - Effect of ampicillin, cephalexin, ceftiofur and tetracycline treatment on selection of resistant coliforms in a swine faecal microcosmos

AU - Herrero-Fresno, A.

AU - Olsen, J. E.

PY - 2020

Y1 - 2020

N2 - Aims: To analyse and compare the effect of selection power for antimicrobial resistance (AMR) in coliforms of two kinds of β-lactams—aminopenicillins; ampicillin (Amp) and cephalosporins; cephalexin (Cpn) and ceftiofur (Cef)—and tetracycline (Tet) using an approach based on a swine faecal microcosmos. Methods and Results: Sixteen faecal samples from 32 pigs (mixed two by two) were treated with Amp, Cpn, Cef and Tet for 6 h (T6h) at concentrations expected to reach the animals gut when using in vivo standard doses. Controls (no drug added) were also tested. Next, samples were 1 : 100 diluted and left under the same conditions (no antimicrobial added) for further 20 h (T20h). The proportion of resistant coliform bacteria (R coliforms) to each antimicrobial was analysed just before starting the treatment (T0), at T6h and at T20h. Coselection was also studied by replica plating. Treatment for 6 h yielded significant increase in proportion of R coliforms, regardless of the drug and lack of selection pressure showed different effects at T20h depending on the antimicrobial used. Selective pressure was associated with the type of the β-lactam with Amp selecting for significantly higher numbers of R coliforms than cephalosporins. Conclusions: AMR development was observed following short treatment, and for Amp and Tet treatment, resistance persisted 20 h beyond the interruption of treatment. An association between kind of β-lactam and power of selection was found. Significance and Impact of the Study: AMR represents a threat to human health globally and antimicrobial treatment of livestock has a direct impact on this problem. Through our approach based on a swine faecal microcosmos, we demonstrated the effect on AMR development of several drugs commonly used in livestock. Cephalosporins, representing last-line antimicrobials in human medicine, exerted lower selective pressure than Amp under the conditions used and yielded higher proportion of multidrug-R strains.

AB - Aims: To analyse and compare the effect of selection power for antimicrobial resistance (AMR) in coliforms of two kinds of β-lactams—aminopenicillins; ampicillin (Amp) and cephalosporins; cephalexin (Cpn) and ceftiofur (Cef)—and tetracycline (Tet) using an approach based on a swine faecal microcosmos. Methods and Results: Sixteen faecal samples from 32 pigs (mixed two by two) were treated with Amp, Cpn, Cef and Tet for 6 h (T6h) at concentrations expected to reach the animals gut when using in vivo standard doses. Controls (no drug added) were also tested. Next, samples were 1 : 100 diluted and left under the same conditions (no antimicrobial added) for further 20 h (T20h). The proportion of resistant coliform bacteria (R coliforms) to each antimicrobial was analysed just before starting the treatment (T0), at T6h and at T20h. Coselection was also studied by replica plating. Treatment for 6 h yielded significant increase in proportion of R coliforms, regardless of the drug and lack of selection pressure showed different effects at T20h depending on the antimicrobial used. Selective pressure was associated with the type of the β-lactam with Amp selecting for significantly higher numbers of R coliforms than cephalosporins. Conclusions: AMR development was observed following short treatment, and for Amp and Tet treatment, resistance persisted 20 h beyond the interruption of treatment. An association between kind of β-lactam and power of selection was found. Significance and Impact of the Study: AMR represents a threat to human health globally and antimicrobial treatment of livestock has a direct impact on this problem. Through our approach based on a swine faecal microcosmos, we demonstrated the effect on AMR development of several drugs commonly used in livestock. Cephalosporins, representing last-line antimicrobials in human medicine, exerted lower selective pressure than Amp under the conditions used and yielded higher proportion of multidrug-R strains.

KW - antimicrobial resistance

KW - E. coli

KW - faecal microcosmos

KW - swine

KW - tetracycline

KW - β-lactams

U2 - 10.1111/jam.14721

DO - 10.1111/jam.14721

M3 - Journal article

C2 - 32430970

AN - SCOPUS:85086178332

VL - 129

SP - 1238

EP - 1247

JO - Proceedings of the Society for Applied Bacteriology

JF - Proceedings of the Society for Applied Bacteriology

SN - 0266-8254

IS - 5

ER -