Backgrounder:Antimicrobial Applications in the Food System and Resistance Management
Production Agriculture Applications
Antibiotics and fungicides, some of which have
identical chemical counterparts in human medicine,
have a variety of useful applications in production
agriculture. Estimates of use exist, but are influenced
by data gaps and inaccuracies. Although the total
amount of antibiotics used in human medicine and
agriculture is not precisely known, both sectors use
appreciable quantities. Estimates of the amount of
antibiotics used annually in production agriculture
range from 18.4 to 30 million pounds. This compares
with estimates for usage in human medicine that range
from 4.5 to 32.2 million pounds.
Animal Husbandry. Antibiotics have been used in
food animals (primarily cattle, swine, and poultry) for
more than 50 years to treat, prevent, or control
infectious disease, or to improve efficiency of feed
utilization and weight gain. Use of antibiotics in bison
production is generally discouraged, occurring only
for treatment purposes. In aquaculture, antibiotics are
only approved to treat disease and cannot be used
prophylactically (for disease prevention) or for growth
promotion.
Administration of veterinary drugs to food animals
is a critical component of an overall management system to secure the health and welfare of the animals
and ensure the safety of the products that enter the
food chain. Therapeutic antimicrobial regimens
include disease treatment1, control2, and prophylaxis
(prevention)3. Antibiotics are administered at low
levels to promote growth rate and enhance feed
efficiency in healthy livestock. The use of an in-feed
antibiotic for growth promotion occurs most often in
young, growing animals; use in older animals has a
lessened effect. Growth promotion uses allow farmers
to produce food animals at less cost because the
amount of feed required for an animal to reach
production weight is reduced. It is thought that the
mechanisms by which growth promotion is achieved
are physiological, nutritional, and metabolic in nature,
relating to antibiotic inhibition of the normal microflora,
which enables more energy to be expended for
nutrient use and increased conversion to weight gain.
Plant Agriculture Applications
Fungicides and antibiotics are used in plant
agriculture to control fungal and bacterial diseases,
e.g., to control fire blight or blister spot in fruit tress.
Trees are generally sprayed during blossom time, when
they are most susceptible to infection; the edible fruit
is not sprayed. A limited number of fruit tree species—apple, pear, and peach—are treated in such a
manner.
Food Processing Applications
A variety of “food antimicrobial agents,” including
antifungals, sanitizers, and beneficial microorganisms
and their inhibitory metabolic products, are applied
during food production and manufacturing to
improve the efficiency of the system and increase the
safety and quality of the product.
Several different types of antimicrobials are used in
food manufacturing to either clean, sanitize, or
disinfect, by reducing the levels of microorganisms on
environmental and food contact surfaces and human
skin and preventing cross-contamination. Several
types of antimicrobials are also used in food formulations,
on food tissues, and on ready-to-eat (RTE)
product surfaces to prevent food spoilage and control
pathogen growth.
Some food preservatives, such as common table
salt, have been in use for hundreds of years, but most
others have been extensively applied only in recent
decades. Food antimicrobial agents are generally not
used alone to control foodborne pathogens, but are
included as synergistic components of the “multiple
hurdle approach” to microbial control. Common
applications of food antimicrobials include use of
sodium nitrite to inhibit Clostridium botulinum in
cured meats if product temperature abuse occurs,
organic acid solutions as spray sanitizers to control
pathogens on beef carcasses, nisin and lysozyme to
control C. botulinum in pasteurized process cheese,
and lactate to control L. monocytogenes in processed
RTE meat and poultry products.
Bacteria and/or the antibacterial products of their
metabolism may also be used to control undesirable
microorganisms. Some bacteria, such as those referred
to as lactic acid bacteria (LAB) and which may be
naturally-occurring either in the initial microflora of
fermented or other foods (e.g., vacuum packaged
meats) or added as starter cultures, may be used
because they can inhibit the growth of spoilage and
pathogenic bacteria by depleting nutrients and oxygen
and producing inhibitory metabolic substances such as
lactic and acetic acids.
Managing Antimicrobial Resistance
A number of strategies are used throughout the
food system, from agricultural production to the
home, to manage the risk of antimicrobial resistance.
These strategies for minimizing and containing antimicrobial resistance include various antibiotic
alternatives and judicious antibiotic use guidelines.
Resistance monitoring systems also contribute to risk
management.
A variety of guidelines exist for responsible (proper,
appropriate, prudent, or judicious) use of antibiotics
in human and veterinary medicine. The guidelines
recognize that any use of antibiotics, human or
animal, has the potential to select for antibiotic
resistance and that all uses of antibiotics cannot be
eliminated or severely constrained. Therefore, the
intent of the documents is to promote appropriate use
of antibiotics, maximizing efficacy and minimizing
resistance development. In practice, this involves
prescribing antibiotic therapy when and only when it
is beneficial to the patient, targeting therapy to the
desired pathogens, and using the appropriate drug,
dose, and treatment duration. Responsible use is not necessarily reduced use,
however; antibiotics may offer valuable benefits when
used appropriately.
Veterinary and other professionals may use nonantibiotic
interventions early in the life of animals to
promote healthy animals that do not become ill and
are unlikely to need antimicrobial treatment. An
example of effective alternatives to antimicrobials is
the use of vaccines in the salmon and trout industries
to control enteric redmouth disease and vibriosis,
where vaccinating young fish “fingerlings” is standard
practice. Another example is the use in feed for food
animals of one or more types of microorganisms to
competitively exclude pathogens, a practice in Europe
and other countries. None of such alternative approaches,
however, can replace therapeutic antibiotic
uses.
The key point of influence that food scientists have
in preventing the spread of resistant and sensitive
pathogenic microorganisms in foods is preventing
them from entering the food supply and, if present,
inactivating them or preventing their growth. Food
manufacturing interventions that effectively reduce
the prevalence of foodborne pathogens also reduce the
prevalence of those that are resistant to antibiotics.
Use of the multiple hurdle approach likely combats
development of resistance to singular antimicrobial
food safety interventions.
1 Treatment is the administration of an antimicrobial to an animal or group of animals exhibiting clinical disease.
2 Control is the administration of an antimicrobial to animals, usually as a herd or flock early in the course of disease onset in the population.
3 Prophylaxis is the administration of an antimicrobial to exposed at-risk healthy animals, generally in a herd or flock situation prior
to the onset of a disease.