Antibiotic
A substance, such as penicillin or streptomycin, produced by or derived from certain fungi, bacteria, and other organisms, that can destroy or inhibit the growth of other microorganisms. Antibiotics are widely used in the prevention and treatment of infectious diseases.

Antimicrobial agent 
Any substance or mixture of substances that acts against microbes (such as a disinfectant, sanitizer or sterilant).

Bacteria
Microscopic organisms composed of a single cell and lacking a defined nucleus and membrane-enclosed internal compartment.

Catheter
A hollow flexible tube for insertion into a body cavity, duct, or vessel to allow the passage of fluids or distend a passageway. Its uses include the drainage of urine from the bladder through the urethra or insertion through a blood vessel into the heart for diagnostic purposes.

Catheterization
Insertion or use of a catheter.

Cellulitis
An acute inflammation of the connective tissue of the skin, caused by infection with staphylococcus, streptococcus, or other bacteria. While cellulitis sometimes develops around wounds in the skin or surgical incisions, in other cases it arises without an obvious source for the bacterial infection.

Central Line
A catheter (tube) that is passed through a vein to end up in the thoracic (chest) portion of the vena cava (the large vein returning blood to the heart) or in the right atrium of the heart.

Cleaning
The process that removes contaminants including dust, soil, large numbers of micro-organisms and organic matter.  It is an essential prerequisite to disinfection and sterilization. It also removes the organic matter on which micro-organisms might subsequently thrive. Also see disinfection and sterilization.

Communicable 
Transmittable between persons or species; contagious.

Disinfection
A process used to reduce the number of micro-organisms but not usually bacterial spores. The process does not necessarily kill or remove all micro-organisms, but reduces their number to a level which is not harmful to health. Also see cleaning and sterilization.

Foley catheters 
A device that is put into the patient's urethra to drain the bladder of urine. Urinary tract infections are associated with the use of foley catheters.

Fungi 
Many types of fungi exist and cause problems in humans, animals and plants. Fungal infections commonly affect the skin and nails in humans. 

Germs
Microbes that cause diseases.  Also called pathogens.

Immune system
The body's natural defense system against infection and disease.  It consists of many organs and cells that have various specialized functions within the overall fight against antigens.

Infection
A state in which disease-causing microbes or organisms such as bacteria or viruses have invaded or multiplied in body tissues. Some infections do not cause disease because the microbe is quickly killed or hides where it cannot be detected. Some infections do lead to disease.

Infectious Disease
Disease caused by microbes that can be passed to or among humans. It occurs when cells or molecules in a person's body stop working properly, causing symptoms of illness. Many things can make someone more susceptible to disease, including altered genes, chemicals, aging, and infections.

Inflammation
An immune system process that stops the progression of disease-causing microbes, often seen at the site of an injury like a cut. Signs include redness, swelling, pain, and heat.

Intravenous (IV) 
Into a vein.

Intubation
The process of putting a tube into a hollow organ or passageway, often into the airway.

Lesion 
A wound or an injury, a localized pathological change in a bodily organ or tissue, or an infected or diseased patch of skin.

Mechanical ventilation
The use of a mechanical device (machine) to inflate and deflate the lungs.

Methicillin-Resistant Staphylococcus Aureus (MRSA) 
Bacteria that cause conditions such as furunculosis, pyemia, osteomyelitis, suppuration of wounds, and food poisoning. The patient is kept in isolation to stop the spread of this infection.  (see "Superbug")

Microbes
Living material too small to see.  Some microbes cause disease in humans, plants, and animals. Others are essential for a healthy life, and we could not exist without them. Four common groups of microbes are bacteria, viruses, fungi, yeasts.  Some people refer to disease-causing microbes as "bugs."

Micro-organisms 
Living cells so small that most can be seen only with a microscope.   Microscopic organisms include bacteria, viruses, fungi, plants, and animals.

Microscopic 
Too small to be seen with the naked eye.

Necrotizing fasciitis 
A dangerous infection of soft-tissue that starts just below the skin and spreads along the flat layers of fibrous tissue that separate different layers of tissue.

Nosocomial 
A term that comes from two Greek words: "nosus" meaning "disease" + "komeion" meaning "to take care of." Hence, "nosocomial" applies to any disease contracted by a patient while under medical care. "Nosocomial" is synonymous with "hospital-acquired."

Organisms 
Individual living things.

Parasites 
Plants or animals that live, grow, and feed on or within another living organism.

Pathogens 
Disease-causing organisms.

Staphylococcus 
Parasitic bacteria, usually occurring in clusters, that cause boils and other infections.

Sterile
Free from live bacteria or other microorganisms.

Sterilization
A process that removes or destroys all forms of microbial life including bacterial spores.  Also see cleaning and sterilization.  

Superbug
An informal term for a bacterium that has become resistant to antibiotics usually used to treat it, as methicillin-resistant Staphylococcus aureus (MRSA) or any multiresistant bacterium.

Tracheostomy
A surgical operation to create an opening into the windpipe (the trachea). The opening itself can also be called a tracheostomy.  A tracheostomy may be needed:
• In an emergency to permit a person to breathe who has severe narrowing or blockage (obstruction) of their upper airway.
• For surgery on patients who have to have the larynx (voice box) removed because of cancer.
• For patients who require long-term support with a breathing machine (ventilator).

Vancomycin-resistant enterococci (VRE)
A form of intestinal bacteria which is not sensitive to the antibiotic, vanomycin.  

Ventilator
A machine which mechanically assists patients in the exchange of oxygen and carbon dioxide (sometimes referred to as artificial respiration).

Virus
A strand of DNA or RNA in a protein coat that must get inside a living cell to grow and reproduce. It causes many types of illness; for example, varicella virus causes chickenpox, and the human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS). Viruses are not responsive to antibiotics.

Yeasts
The most common yeast infection is thrush. This is due to a yeast called Candida which thrives in moist airless, warm areas of the body.