Antibacterial

A drug that kills or inhibits the growth of bacteria.

Antibiotics

A class of substances that kill or inhibit the growth of bacteria. Examples are penicillin, tetracycline, and fluoroquinolones. Originally, antibiotics were derived from natural sources, e.g., penicillin from molds, but many currently used antibiotics are semi-synthetic and modified with additions of synthetic chemical components. Some scientists reserve the term antibiotic for naturally produced substances and use antimicrobial to encompass both synthetic and natural forms.

Antibiotic resistance

The capacity of bacteria to inactivate or exclude antibiotics or otherwise block their inhibitory or killing effects. Resistant bacteria evolve as a result of using antibiotics. Antibiotics kill or inhibit susceptible bacteria and resistant ones survive.

Antibiotic susceptibility

The opposite of resistance and applies to bacteria that are killed or inhibited by an antibiotic. Susceptibility to one antibiotic does not mean susceptibility to all antibiotics.

Antimicrobials

A class of substances that destroy or inhibit the growth of bacteria. Includes synthetic and natural chemical substances.

Bacteria

Microscopic, single-celled organisms.

Broad-spectrum antibiotic

An antibiotic effective against a large number of bacterial species.

Commensal bacteria

Bacteria that live inside or on the body and do not usually cause disease. May be beneficial to the host.

Escherichia coli

commensal bacteria that live in the intestine and sometimes causes opportunistic infections.

Flora

The populations of commensal bacteria normally present in the intestine, body openings, and on the skin.

Food-borne pathogens

Food-borne pathogens are defined as infectious organisms associated with livestock which can cause diseases in humans. They include Salmonella, Campylobacter, E. coli O157:H7, and Listeria.

Gene

A segment of DNA that carries the directions for the structure of a given protein. Antibiotic-resistance genes direct the synthesis of antibiotic-resistance proteins.

Incidence

The frequency of new occurrences of disease within a defined time interval. Incidence rate is the number of new cases of a specified disease divided by the number of people in a population over a specified period of time, usually one year.

Methicillin-resistant Staphylococcus aureus (MRSA)

Strictly speaking, a bacterial strain resistant to methicillin. In practice, MRSAs are generally resistant to many antibiotics and some are resistant to all but vancomycin.

Microorganism

Minute, microscopic or submicroscopic living organisms; includes bacteria, fungi, and protozoa. Viruses are often included in this category though they are incapable of growth and reproduction outside of host cells.

Multiple drug resistance

Applies to bacteria that are resistant to more than one antibiotic.

Narrow spectrum antibiotic

An antibiotic effective against a limited number of microorganisms.

Nosocomial infection

Infection acquired during hospitalization that is not present at the time of hospital admission.

Opportunistic infection

An infection caused by an organism that is usually benign, such as a commensal bacterium.

Pathogen

Pathogenicity

Capacity to cause disease.

Prophylactic use of antibiotics

Treating with antibiotics before evidence of infection to prevent disease. In livestock production, prophylactic doses may range from sub therapeutic to therapeutic levels depending upon the drug, the animal, and environment.

Therapeutic uses of antibiotics

Treating with antibiotics once a disease has developed