Essentials Host-Microorganism Interactions Flashcards
HUMAN AND MICROBE INTERACTIONS:
acquiring a microorganism from another human serving as the reservoir
Direct transmission
HUMAN AND MICROBE INTERACTIONS:
can occur when microorganisms from one individual contaminate a vehicle of transmission, such as water (e.g., cholera), that is then ingested by another person.
Indirect Transmission
animals, insects, other humans
Vectors
water, food, air, medical devices, various other inanimate objects
Vehicles
HUMAN AND MICROBE INTERACTIONS:
Hospital-acquired, health care-associated, or long-term care-associated infections historically are referred to as
Nosocomial infections
ANIMALS AS MICROBIAL RESERVOIRS:
WHEN A HUMAN INFECTION RESULTS FROM SUCH AN ENCOUNTER
ZOONOTIC INFECTION
SKIN SERVES AS A PHYSICAL AND CHEMICAL BARRIER TO MICROORGANISMS:
microorganisms that inhabit many surfaces of the human body
*Colonizers *Normal flora
*Normal microbiota, *Human microbiome
SKIN SERVES AS A PHYSICAL AND CHEMICAL BARRIER TO MICROORGANISMS:
they are able to survive, but do not multiply, on the surface and are frequently shed with the host cells.
Transient colonizers
SKIN SERVES AS A PHYSICAL AND CHEMICAL BARRIER TO MICROORGANISMS:
not only survive but also thrive and multiply; their presence is more persistent.
Resident microbiota
PATHOGENS, AND THE CHARACTERISTICS THAT ENABLE THEM TO CAUSE DISEASE
VIRULENCE FACTORS
THE ORGANISM’S ABILITY TO CAUSE DISEASE
PATHOGENICITY
THE MEASURE OR DEGREE OF PATHOGENICITY OF AN ORGANISM
VIRULENCE
THE ORGANISM IS VERY LIKELY TO CAUSE DISEASE
HIGH PATHOGENICITY
THE ORGANISM IS MUCH LESS LIKELY TO CAUSE INFECTION
LOW PATHOGENICITY
ORGANISMS THAT CAUSE INFECTION WHEN ONE OR MORE OF THE HOST’S DEFENSE MECHANISMS ARE DISRUPTED OR MALFUNCTION
OPPORTUNISTIC PATHOGENS
ORGANISMS THAT CAUSE INFECTION WHEN ONE OR MORE OF THE HOST’S DEFENSE MECHANISMS ARE DISRUPTED OR MALFUNCTION AND THE INFECTIONS THEY CAUSE IS CALLED
OPPORTUNISTIC INFECTIONS
Microbial Virulence Factors
- Attachment
- Invasion
- Survival against inflammation
- Survival against the immune system
- Microbial toxins
- Biofilm formation
MICROBIAL VIRULENCE FACTORS:
ONCE SURFACE ATTACHMENT HAS BEEN SECURED, MICROBIAL INVASION INTO SUBSURFACE TISSUES AND ORGANS (I.E., INFECTION) IS ACCOMPLISHED BY DISRUPTION OF THE SKIN AND MUCOSAL SURFACES BY SEVERAL MECHANISMS OR BY THE DIRECT ACTION OF AN ORGANISM’S VIRULENCE FACTORS
INVASION
MICROBIAL VIRULENCE FACTORS:
AVOID PHAGOCYTOSIS BY PRODUCING A LARGE CAPSULE THAT INHIBITS THE PHAGOCYTIC PROCESS
SURVIVAL AGAINST INFLAMMATION
MICROBIAL VIRULENCE FACTORS:
TOXINS ARE BIOCHEMICALLY ACTIVE SUBSTANCES RELEASED BY MICROORGANISMS THAT HAVE A PARTICULAR EFFECT ON HOST CELLS
MICROBIAL TOXINS
MICROBIAL VIRULENCE FACTORS:
MICROORGANISMS TYPICALLY EXIST AS A GROUP OR COMMUNITY OF ORGANISMS CAPABLE OF ADHERING TO
BIOFILM FORMATION
Bacterial Toxins:
*General toxin common to almost all gram-negative bacteria
*Composed of the lipopolysaccharide portion of cell envelope
*Released when a gram-negative bacterial cell is destroyed
Endotoxins
Bacterial Toxins:
*Most commonly associated with gram-positive bacteria
*Produced and released by living bacteria; do not require
bacterial death for release
*Specific toxins target specific host cells; the type of toxin varies with the bacterial species
*Some kill host cells and help spread bacteria in tissues (e.g., enzymes that destroy key biochemical tissue components or specifically destroy host cell membrane)
*Some destroy or interfere with specific intracellular activities (e.g., interruption of protein synthesis, interruption of internal cell signals, or interruption of the neuromuscular system)
Exotoxins
OUTCOME OF INFECTIOUS DISEASES:
INFECTIOUS PROCESSES THAT DEVELOP QUICKLY
ACUTE INFECTIONS
OUTCOME OF INFECTIOUS DISEASES:
DEVELOP AND PROGRESS SLOWLY, SOMETIMES OVER A PERIOD OF YEARS
CHRONIC INFECTIONS
SOME PATHOGENS, PARTICULARLY CERTAIN VIRUSES, CAN BE CLINICALLY SILENT INSIDE THE BODY WITHOUT ANY NOTICEABLE EFFECT ON THE HOST BEFORE SUDDENLY CAUSING A SEVERE AND ACUTE INFECTION. DURING THE SILENT PHASE, THE INFECTION IS SAID TO BE
Latent
PREVENTION OF INFECTIOUS DISEASES:
ONE OF THE MOST EFFECTIVE METHODS IS _________, ALSO REFERRED TO AS ___________
VACCINATION, IMMUNIZATION
THE TWO BASIC APPROACHES TO IMMUNIZATION
ACTIVE IMMUNIZATION AND PASSIVE IMMUNIZATION
MODIFIED ANTIGENS FROM PATHOGENIC MICROORGANISMS ARE INTRODUCED INTO THE BODY AND CAUSE AN IMMUNE RESPONSE
ACTIVE IMMUNIZATION
ANTIBODIES AGAINST A PARTICULAR PATHOGEN THAT HAVE BEEN PRODUCED IN ONE HOST ARE TRANSFERRED TO A SECOND HOST, WHERE THEY PROVIDE TEMPORARY PROTECTION
PASSIVE IMMUNIZATION
THE PASSAGE OF MATERNAL ANTIBODIES TO THE NEWBORN IS A KEY EXAMPLE OF _________
NATURAL PASSIVE IMMUNIZATION
THE ADMINISTRATION OF ANTIBIOTICS WHEN THE RISK OF DEVELOPING AN INFECTION IS HIGH, IS ANOTHER COMMON MEDICAL INTERVENTION FOR PREVENTING INFECTION
PROPHYLACTIC ANTIMICROBIAL THERAPY
A person who harbors the etiologic agent but shows no apparent signs or symptoms of infection or disease
Carrier
A single source or reservoir from which an etiologic agent responsible for an epidemic or outbreak originates
Common source
The number of new diseases or infected persons in a population
Disease incidence
The percentage of diseased persons in
a given population at a particular time
Disease prevalence
A disease constantly present at some rate of occurrence in a particular location
Endemic
A larger-than-normal number of diseased or infected individuals in a particular location
Epidemic
A microorganism responsible for causing intection or infectious disease
Etiologic agent
Infections acquired as a result of a medical procedure, such as insertion of a central line, catheter, or ventilator, or as a result of participation or admission into a health care facility
Health care-associated infection
An individual’s microbiologic environment, present in or on the human host
Microbiome
The means by which etiologic agents are brought in contact with the human host (e.g., infected blood, contaminated water, insect bite)
Mode of transmission
The state of disease and its associated effects on the host
Morbidity
The incidence of a particular disease state
Morbidity rate
Death resulting from disease
Mortality
The incidence in which a disease results in death
Mortality rate
Infection for which the etiologic agent was acquired in a hospital or long-term health care center or facility
Nosocomial infection
A larger than normal number of diseased or infected individuals that occurs over a relatively short period
Outbreak
An epidemic that spans the world
Pandemic
The origin of the etiologic agent or location from which it disseminates (e.g., water, food, insects, animals, other humans
Reservoir
Laboratory-based characterization of etiologic agents designed to establish their relatedness to one another during a particular outbreak or epidemic
Strain typing:
Any type of epidemiologic investigation that involves data collection for characterizing circumstances. surrounding the incidence or prevalence of a particular disease or infection
Surveillance
A living entity (animal, insect, or plant) that transmits
the etiologic agent
Vector
A nonliving entity that is contaminated with the etiologic agent and as such is the mode of transmission for that agent
Vehicle
