TABLE 1.

Commonly Used Terms, Definitions and Abbreviations^a

Term	Abbreviation	Definition as used in this review
Antimicrobial		An antimicrobial substance is one that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans and destroys viruses
Bioburden		The number of microorganisms with which an object is contaminated
Biofilm		An aggregate of microorganisms in which cells are stuck to each other or to a surface or to both. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance. The cells of a microorganism growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which by contrast, are single cells that may float or swim in a liquid medium
Coagulase-negative Staphylococci	CNS	Coagulase is an enzyme produced by Staphylococcus aureus, which converts fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of Staphylococcus isolates. Coagulase negativity excludes S. aureus
Colony forming unit	CFU	A measure of viable bacterial or fungal numbers. Unlike direct microscopic counts where all cells, dead and living, are counted, CFU measures viable cells
Commensal (microorganisms)		A class of relationship between two organisms where one organism benefits but the other is unaffected
Daily wear	DW	Contact lenses wearing modality where lenses are removed nightly
Extended wear	EW	Contact lenses wearing modality where lenses are worn continuously, typically at least 6 nights and up to 29 nights
Gram-negative bacteria	Gram−	Those bacteria that do not retain crystal violet dye in the Gram staining protocol based on the structure of their cell walls. The pathogenic capability of Gram-negative bacteria is often associated with certain components of their cell walls, in particular the lipopolysaccharide (also known as LPS or endotoxin) layer
Gram-positive bacteria	Gram+	Those bacteria that are stained dark blue or violet by Gram staining. Gram+ organisms are able to retain the crystal violet stain because of the high amount of thick peptidoglycan in the cell wall
Normal microbiota		Organisms on the human host that are expected to be present and that under normal circumstances do not cause disease, but instead may participate in maintaining health
Pathogenic organisms		Organisms that have the capability of causing infectious diseases

^aAdapted from Wikipedia.⁹⁹