The objective of this work - reported in BMC Veterinary Research by Shiona Glass-Kaastra of the University of Guelph in Canada and co-authors - was to assess retrospectively records received through the Ontario Swine Veterinary-based Surveillance programme between July 2007 and July 2009 to describe and assess relationships between reported treatment failure, antimicrobial use, diagnosis and body system affected.

Antimicrobial use occurred in 676 records, 80.4 per cent of all records recording treatment (840). The most commonly used antimicrobials were penicillin (34.9 per cent), tetracyclines (10.7 per cent) and ceftiofur (7.8 per cent), and the use of multiple antimicrobials occurred in 141/676 records (20.9 per cent).

A multi-level logistic regression model was built to describe the probability of reported treatment failure.

The odds of reported treatment failure were significantly reduced if the record indicated that the gastro-intestinal (GI) system was affected, as compared to all other body systems (p< 0.05).

In contrast, the odds of reported treatment failure increased by 1.98 times if two antimicrobials were used as compared to one antimicrobial (p = 0.009) and by 6.52 times if three or more antimicrobials were used as compared to one antimicrobial (p = 0.005).

No significant increase in reported treatment failure was seen between the use of two antimicrobials and three or more antimicrobials.

No other antimicrobials were significantly associated with reported treatment failure after controlling for body system and the number of antimicrobials used.

Failure of antimicrobial treatment is more likely to occur in non-GI conditions than GI conditions, concluded Glass-Kaastra and co-authors, and the use of multiple antimicrobial products is also associated with an increased probability of antimicrobial treatment failure.

The authors suggest that a more preventative approach to herd health should be taken in order to reduce antimicrobial inputs on-farm, including improved immunity via vaccination, management and biosecurity strategies.

Furthermore, they suggest that improved immunity may be viewed as a form of antimicrobial stewardship to the industry by reducing required antimicrobial inputs and consequently, reduced selection pressure for antimicrobial resisitance.

Reference

Glass-Kaastra S.K., D.L. Pearl, R.J. Reid-Smith, B. McEwen, S.A. McEwen, R. Amezcua and R.M. Friendship. 2013. Describing antimicrobial use and reported treatment efficacy in Ontario swine using the Ontario swine veterinary-based Surveillance program. BMC Veterinary Research. 9:238.

December 2013