Term | Definition |
Virulence | An operational term that rests on the interaction between microbial factors and the defenses of the host |
Opportunistic pathogen | Organisms of normally low virulence (i.e., not usually capable of causing disease in a normal individual) may become dangerous pathogens when immunity is compromised |
Reservoir | A habitat where etiologic agents normally reside and multiply |
Source | The place from which an organism is transmitted to the host |
Endogenous | Part of the flora normally colonizing the skin or mucous membranes |
Exogenous | Acquired from the environment |
Endogenous normal flora | Organisms that are capable of colonizing the normal host for long period of time without causing disease |
Portal of entry | Original site of contact |
Adhesins | Specific molecules on the organisms that are responsible for attachment (e.g., glycoproteins that can bind to cellular surface receptors or to extracellular matrix materials) (i.e., bacterial attachment factors) |
Peptidoglycan | A network of poysaccharide chains cross-linked by short peptides |
Pilus (fimbria) | One of the most prominent types of bacterial adhesins |
Epidemiology | The study of the distribution and determinants of diseases of infectious origin and other etiologies, injuries, and other health states in populations, and the use of this information to prevent or control health problems and to improve health |
Chain of transmission | The agent, a source for the agent, a route of exit from the reservoir or source host (e.g., the respiratory or gastrointestinal tracts), a suitable mode from the source to the new susceptible host, and a route of entry into the new susceptible host |
Vertical transmission | From mother to fetus or newborn prior to or during delivery |
Horizontal transmission | Spread between individuals within the population at risk |
Direct contact transmisison | Involves physical contact (e..g, through shaking of hands, kissing, or sexual intercourse) between the infected host and the susceptible |
Indirect contact transmission | May involve contaminated vehicles (fomites), such as shared eating utensils, toys in a child care facility, or improperly sterilized surgical equipment or non-disposable needles and syringes |