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Oral Administration of Antimicrobials Increases Antimicrobial Resistance in E. coli from Chicken

02 February 2015

From a review of published literature, researchers in Germany found that the administration of a single antimicrobial resulted in a higher level of antimicrobial resistance in most cases, and this tended to increase when more than antimicrobial and/or higher dosages were used.

Antimicrobials play an important role in animal and human health care. Researchers at Germany's Federal Institute for Risk Assessment in Berlin including first-named author, Celine Simoneit, undertook a systematic review to assess the effects of oral administration of antimicrobials on the development of antimicrobial resistance (AMR) in Escherichia coli (E. coli) from chickens. They also studied the effects of the administration of more than one antimicrobial and of different dosages were studied.

In a paper published in Preventive Veterinary Medicine, they explain that they searched the literature in November 2012 from the electronic databases ISI Web of Science, PubMed, Scopus and a national literature database (DIMDI) as well as the database ProQuest LLC. The search was updated in March 2014.

The researchers included original studies describing a treatment (A) and a control group of either non-treatment (C) or initial value (0) and determining AMR in E. coli at different sample points (SP).

The literature search resulted in 35 full-text articles on the topic, seven (20 per cent) of which contained sufficient information on the administered antimicrobial and the impact of treatment on AMR.

Most papers described the use of more than one antimicrobial, several dosages, controls (non-treatment or pre-treatment) and measured AMR at different SPs leading to a total of 227 SPs on the impact of the use of antimicrobials on AMR in chickens.

Seventy-four per cent of the SPs (168/227) described a higher AMR-rate in E. coli from treated animals than from controls.

After the administration of a single antimicrobial, AMR increased at 72 per cent of the SPs. Administration of more than one antimicrobial increased AMR at 82 per cent of the SPs.

Higher dosages were associated with similar or higher AMR rates, the Berlin-based researchers found.

Simoneit and colleagues concluded that the limited number of studies for each antimicrobial agent and the high variability in the resistance effect call for more well-designed studies on the impact of oral administration on AMR development and spread.


Simoneit C., E. Burow, B-A. Tenhagen and A. Käsbohrer. 2015. Oral administration of antimicrobials increase antimicrobial resistance in E. coli from chicken – a systematic review. Preventive Veterinary Medicine. 118:1-7.

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February 2015

Antimicrobial Resistance

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