Some bacteria are able to secrete a biochemical netting that can cover and protect colonies from other bacteria, germicides, and other adverse conditions.  When these nettings form on the surface of containers, tubing or mechanical structures, the biofilm can shield the underlying bacteria.  Biofilm is not visible without magnification with a microscope. It is not uncommon for bacteria to grow under biofilm produced by other bacteria.

Person or animal without symptoms of illness that harbors and sheds virulent bacteria that can infect others or contaminate the environment.

In the specific discussion of testing for lactose intolerance, the amount of lactose introduced (ingested) that is used to trigger a response that is then measured by the specific test.

Some pathogens are able to grow within the intestinal tract of humans or animals, without causing illness. To distinguish this from infection, when it occurs without illness it is termed colonization.

When an animal's intestinal tract contains virulent bacteria that are shed in the feces, however, the animal is not ill.

Unit of measure for numbers of bacteria in a sample. Describes the number of colonies that form from a sample. When bacteria multiply on culture they form masses called colonies.  Since bacteria often adhere to each other, it is not possible to be sure that each colony results from the multiplication of a single starting bacterium.  Therefore, the term colony forming units is used to acknowledge that the origin of the colony could have been a single bacterium or a group of bacteria that were stuck together.

Ability to grow/multiply of a specific type of bacteria when surrounded by other types in the same environment.

Within many environments there are large numbers of different bacteria, many of which are present in very large numbers. In such complex environments, those bacteria present in small numbers grow more slowly or maybe excluded. There are many explanations for this inhibition including; the ability of some bacteria to secrete products that kill or injure other bacteria, the competition for nutrients and physical interactions.

Laboratory technique to enable individual bacteria present in a specimen to grow/multiply forming masses/colonies visible to the unaided eye. Also a mixture of nutrients specifically formulated to enable specific types of bacteria to grow/multiply.

A specific disease occurrence that is widespread across large geographic area. Usually pertaining to a single animal or group of animals.

Illness involving the cells lining the intestinal tract, including the stomach, small and large intestine.

Disease that is a significant public health problem spreading and infecting large numbers of people, or specific animals.

Occasionally an outbreak occurs with unusually high numbers of severe illness complications. The strain identified is often called an epidemic clone. Most commonly used with listeriosis.

Extrapulmonary

Localized disease in parts of the body other than the airways and lungs.

A specific type of thread-like projection from the cell wall of some types of bacteria that enable movement.

Category of subtypes distinguished by the proteins in the bacteria's flagellum. Testing is made easier since the characteristic is on the outside of the bacteria.

Natural animal feed composed of grasses and non-woody plants as eaten in pasture, or harvested as hay.  Generally does not include the seeds or roots.

Illness involving the cells lining the intestinal tract, including the stomach, small and large intestine.

Different characteristics identified by the nucleic acid content, genetic molecules, usually DNA sequences.

Scientifically established subgroup under "Family". The genus name is the first word in the official name for a bacterial group, e.g. Listeria monocytogenes.  Listeria is the genus,  monocytogenes is the species.

Large group of bacteria identified under the microscope because they stain "negative" with dyes included in the Gram Stain. After the method is complete individual bacteria have a pink color.

Large group of bacteria identified under the microscope because they stain "positive" with dyes included in the Gram Stain.  After the method is complete individual bacteria have a purple color.

A protein associated with flagella (projections on surface of bacteria that enable motility), easily identified by commercially available test and used to distinguish between serotypes of bacteria, e.g. E. coli H7.

Serious complication associated with certain forms of toxins produced by some virulent bacteria that may cause temporary kidney failure particularly in children.  See sidebar in Pathogen Summary E. Coli page 7.

Genetic information that has been transferred between different species usually with viruses acting as the transfer agent. In contrast to ancestral genetic information.

A particular subtype of bacteria has become selectively virulent in a single animal.  Does not grow or multiply in other animals.

General term used to describe mechanisms that resist infection.

Interval between ingestion of virulent bacteria and onset of symptoms of illness.

Amount of a virulent bacteria that will cause illness when consumed.  See sidebar Infectious Dose.

Capable of establishing physical location to grow and multiply in a host. Also meaning form of bacteria that can be spread from one infected individual to others.

Mechanically introduce a type of bacteria.  Usually in the context of an experiment to determine fate of a specific type of bacteria. Example: inoculating 100,000 individual bacteria into milk to determine whether they will grow, multiply, become inactivated or are killed.

In tissues, the space between cells.

The complex of microorganism that populate the gut. Includes all forms of microscopic organisms.

Organism will only grow within living cells of the host animal.

Grouping of subtypes generally related to genetic heritage.

In general any illness caused by listeria. However, it is more commonly used to describe the extremely rare severe systemic illness excluding the far more frequent mild forms of gastroenteritis.

Any infection of the mammary glands.

Some significant laboratory evidence that two or more isolates/strains of bacteria were the "same" or very similar.

Capable of self propelled movement, usually determined by observing the bacteria with a microscope.

Will only grow and multiply within the cells of a host.

Two or more illness in people in different households that are linked by a common source and within a specified time course.

General term for group of bacteria that have been associated with illness. Usually in the form of the scientific name for the group.

Illness that occurs during the development of the fetus and in the newborn.

Continuing to shed virulent bacteria for a long time (years) after an infection but without symptoms of illness.

Different characteristics identified by the expression of genetic material.  Examples: shape, production of specific protein, motility, by-products of metabolism, types of nutrient that can be utilized.

One of the types of laboratory techniques used to distinguish genetic characteristics of a bacterial isolate.

Laboratory test technique that predictably cuts up DNA sequences into large fragments, which are then separated into "sizes". Results in characteristic bands along a column of gel.

Bacteria with elongated body when viewed in the microscope.  In contrast to cocci which are spherically shaped.

Subclassification of animals (including cows, goats, and sheep) that have digestive system that efficiently digests grasses and hay (leafy plants high in cellulose fiber).

Within a cluster of illnesses associated with a common cause, when someone becomes infected from close contact with someone in the cluster, rather than from ingesting the food, they are categorized as secondary infections. In contrast those who become infected from consumption of the food are considered primary infections.

Illness resolves without medical interventions.

Category of subtypes distinguishable by different protein antigens (typically distinguished by the use of commercial antibody preparations).

Subtype distinguishable by different antigens (typically distinguished by the use of commercial antibody preparations).  This is used with subtypes of the genus salmonella.  In most other organisms the term serotype is used to distinguish subtypes of a species based on differences in a surface protein on the organism.

Membrane filter in the pipe lines from the milking to the bulk storage tank, designed to remove particles from the milk.

Characteristic of an antigen contained within the body of a bacterium.

In epidemiology are those individuals with illness that have no known association with other ill individuals.

When used in a scientific name the scientific abbreviation for "all species"  e.g. Salmonella spp. Meaning all of the species within the genus salmonella.

A term used for subtypes of a species.

Infectious state when the outward signs of illness are minimal.

Recognized subdivisions of the named species.

General term used to describe different groups within a named species.

When there is colonization of pathogens in the intestines of animals, the condition is generally transient, and the concentration of pathogens shed in the feces is low. However, there are uncommon individual animals that tend to have persistent colonization and shed much higher concentrations of the pathogen in their feces.  These individual animals are called super shedders.

Person who is capable of becoming infected.

The infectious bacteria have spread from the intestine into the body, usually through the blood stream and may infect other organs of the body.

Molecule, often a protein, produced by bacteria that cause damage or illness. Some bacterial toxins remain within the bacteria (endogenous), others are secreted outside (exogenous).

Some pathogens are able to grow within the intestinal tract of humans or animals, without causing illness.  When this colonization occurs for only a short time, or intermittently it is termed transient.  The usual pattern in these cases is that the concentration of pathogens shed in the feces is low.

Milk that has not been pasteurized, homogenized, separated or otherwise mechanically altered after milking.

Genetic material that has been passed down over a long time from generation to generation.  The DNA is within a chromosome. See sidebar in Pathogen Summary E. coli page 3.

Individual component of virulent bacteria necessary in the sequence of steps leading to illness.

Infectious diseases transmitted to humans from infected animals. Occasionally applied to human infections transmitted from animals even if the animals were not sick.