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Antimicrobial (Antibiotic) Resistance
What is the difference between antibiotics and antimicrobials?
Antimicrobials are drugs that either kill or suppress microscopic organisms such as bacteria, viruses and parasites. Antibiotics are the sub-group of antimicrobial drugs that act against bacteria.What is antibiotic resistance?
Antibiotic resistance is a property of bacteria that enables them to grow in the presence of antibiotic levels that would normally suppress or kill susceptible bacteria.How is resistance to antibiotics acquired?
Antibiotic resistance can occur naturally in some types of bacteria when the antibiotic, because of its characteristics, cannot suppress or kill the particular species of bacteria. It is for this reason that different antibiotics are used to treat infections caused by different bacteria.
The antibiotic resistance of greatest concern is that which is acquired by bacteria through alterations in their genetic make-up as a result of chance changes (mutations) in their DNA or through movement of antibiotic resistance genes from one bacterium to another. Continued use of an antibiotic in the face of resistance to it, allows resistant bacteria to survive the treatment and these then become the dominant bacteria in that setting. This process of selection of resistant bacteria is more likely to occur when the exposure of bacteria to antibiotics is greatest. This can occur when:
- there is overuse of antibiotics in hospitals, the community and on farms;
- antibiotics are used at low doses for long periods of time;
- there is a high number of bacteria present - a high bacterial load;
- there is a high level of resistant bacteria present.
How is resistance to antibiotics spread?
Antibiotic resistant bacteria can be spread from person to person through direct contact with infectious material, poor hygiene or poor infection control, for example, in hospitals. Similarly resistant bacteria can pass from animal to animal, usually via the faeces and this occurs more frequently when animals are held in confined conditions. It is also possible for resistant enteric (gut) bacteria to be passed from animals to humans via food or water where there is poor hygiene and sanitation.
Can antibiotic residues in food lead to antibiotic resistance?
One of the findings of the Joint Expert Technical Advisory Committee on Antibiotic Resistance (JETACAR) was that it was highly unlikely that the consumption of antibiotic residues in food would lead to the development of resistance. This is because antibiotic residue levels in food are already very low and are likely to be further reduced by cooking and other food processing and also by metabolism in the gut. On this basis, it is very unlikely that a dose high enough to inhibit sensitive bacteria and thus encourage the growth of resistant bacteria would be achieved.
What is being done in Australia to minimise antibiotic resistance in bacteria of animal origin being transferred to humans?
In Australia , the Australian Pesticides and Veterinary Medicines Authority is responsible for approving the use of antibiotics. Before an antibiotic product can be legally used, the APVMA must be satisfied that the use of the product will not result in the development of antibiotic resistance that will impair the efficacy of any other antibiotic for human or animal use. In assessing this risk, the APVMA seeks the advice of the NHMRC's Expert Advisory Group on Antimicrobial Resistance.
The Joint Expert Technical Advisory Committee on Antibiotic Resistance (JETACAR) was formed in 1997 to assess the scientific evidence for the link between the use of antibiotics in food-producing animals, the emergence of antibiotic-resistant bacteria and their spread to humans, and develop recommendations for the management of antibiotic use. As part of measures taken to address the JETACAR recommendations, a review of antibiotics used for growth promotion purposes is underway and a phase-out has begun for some animal antibiotics that are:
- ineffective in livestock production under Australian farming conditions;
- frequently used for treating infections in humans or animals, or are considered critical therapy for human use; and
- likely to impair the effectiveness of prescribed antibiotics for animal or human infections through the development of resistant strains of bacteria.
The Australian food industry maintains high standards of hygiene according to regulations and operates under approved and audited Quality Assurance/Control Schemes. Food Safety Standards facilitate hygienic practices in the production, manufacturing, transport and handling of food. This ensures that bacterial contamination in food is minimised.
In order to promote the responsible and prudent use of antibiotics, some sections of the livestock industries, the Australian Veterinary Association and its specialist bodies have developed guidelines for the prudent use of antibiotics and the livestock industries have incorporated guidelines on the responsible use of antibiotics into on-farm quality assurance programs.
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