Posted: June 25th, 2009 - 8:45am

In the United Kingdom, 387 tonnes of antimicrobial drugs were used, in 2007 in veterinary medicine, for food producing animals and for companion animals. Eighty nine per cent was given via the oral route, mainly in feed premixes or drinking water medication and 10% by injection. Tetracyclines were the most commonly used antibiotic (45%) followed by trimethoprim/sulphonamide combinations (19%) and beta-lactam antibiotics (penicillins, synthetic penicillins etc) at 17%. The cephalosporins and fluoroquinolones, which are considered of critical importance in human medicine only accounted for 1.6% and 0.5% of animal use respectively, which is low. Use in swine, although only 9 million are slaughtered each year in the UK, is estimated to account for 53% of antimicrobial use. As a result, there is a marked responsibility on the swine veterinarian to use antimicrobial drugs responsibly and judiciously to achieve the best outcomes both clinically, bacteriologically and economically for his clients, to try to limit the development of antimicrobial resistance in the pig population but also to try to reduce the chances of spread of resistance to the human population.
When antimicrobials are used there is always a risk that the selection of antimicrobial resistance will occur. Some bacterial species, such as Escherichia coli, appear to develop resistance more quickly than others and some antimicrobials, e.g. the tetracyclines, more easily induce resistance.
The best approach  to antibiotic resistance is to avoid or reduce the use of antimicrobials by using high health (specific pathogen free (SPF) animals, employing disease eradication or vaccination programmes where possible and using management and hygiene strategies to reduce infectious challenge. When forced to use antimicrobials, optimum programmes of use must be employed to reduce the opportunities for resistance development. Making sure the right organism is being treated, by culturing and antimicrobial susceptibility testing, using knowledge of effective drug concentrations to kill the organism in the target tissues or fluids. Understanding the pharmacokinetics of the antimicrobials is essential and relating these to the pharmacodynamic effect on the bacteria to achieve not only a clinical cure but also a bacterial cure. Going beyond the mutant selection window, also helps to improve the long term clinical effect of an antimicrobial and reduces the development of resistance.
The full article by veterinarian David Burch of Octagon Services includes data tables and references and is available online at
www.octagon-services.co.uk/pigs.htm