2. What Are Antimicrobials?

What is an antimicrobial and how is it made available?

The term ‘antimicrobial’ is in most cases synonymous with ‘antibiotic’, and describes a substance that kills or inhibits the growth of bacteria. Most are naturally produced by bacteria and fungi, others are man-made but have the same effect Whilst ‘antibiotic is the word popularly used, antimicrobial is the correct word to describe the whole range of substances Even today,most of the substances used are from natural origin and are produced through fermentation processes.

The first antimicrobials used were sulphonamides and penicillin discovered during the 1930s By the late 1940s the pharmaceutical industry had started to discover and select numerous individual compounds which inhibited or killed bacteria, thus extending the range of antimicrobial classes.

Although individual compounds within a class tend to have similar properties, they can differ in terms of:

> Spectrum – the species of bacteria that
can be controlled by the antimicrobial;

> Pharmacokinetics – the absorption,
distribution and elimination of the
antibiotic in the body of the animal
treated;

> Toxicity – the potential harmful
side effects of a medicine.

Now numerous classes are available for use in animals by various routes of administration, such as bolus, drench, feed, injection, intramammary, pessary, topical and water The different classes available include aminoglycosides, cephalosporins, (fluoro) quinolones, macrolides, penicillins, phenicols, pleuromutilins, polypeptides, ionophores, sulphonamides, tetracyclines, to name just a few Some of these families have been developed exclusively for animal health Before an animal medicine, including antimicrobials, can be placed on the market a manufacturer must prove to the regulatory authority the quality, safety and efficacy of the product when used as recommended These procedures are rigorous and allow the user and consumer to have confidence in licensed medicines As with human medicines, the safety, quality and effectiveness of any medicine must be proven to the satisfaction of independent regulatory authorities.

> Safety: the product is safe for the animal itself, the consumer of food derived fromtreated animals, those handling the product and the environment,
> Quality:the product is of consistent high quality, does not deteriorate and has the stability to last at least until the expiry date, and,
> Efficacy: the product’s efficacy conforms with the claims made on its information leaflet and label.
The authorisation process does not stop at this point In addition, users are required to engage in:
> Pharmacovigilance: the systematic collection of information on any adverse effect that may be observed in the daily use of the product.
In order to continuously ensure the safety of animals, consumers, users and the environment, national authorities monitor for the presence of undesirable residues In addition, many authorities monitor the quantities used and carry out surveillance of antimicrobial resistance among relevant bacteria.