basta Flashcards
• A condition in which pathogenic microorganisms penetrate host defenses, enter the tissues, and multiply
infection
Cumulative effects of infection damage
• Disruption of tissues and organs
• Results in disease
pathologic state
Any deviation from health
disease
Factors that cause disease (3)
— Infections
- Genetics
- Aging
- Malfunctions of systems or organs
Disruption of tissues or organs caused by microbes or their products
infectious disease
Large and diverse collection of microbes living on and in the body
Also known as resident or indigenous biota or normal flora
normal biota
We have a lot of microbes in places we used to think were sterile
• All healthy people harbor potentially dangerous pathogens, but in low numbers
The Human Microbiome Project
Human cells contain how many protein encoding genes;
21,000
microbes that inhabit humans contain
8 million
Differences in the gut microbiome have preliminarily been associated with differences in the risk for:
- Crohn’s disease
- Obesity
- Heart disease
— Asthma - Autism
- Diabetes
- moods
Sites Definitively Known to Harbor Normal Microbiota
Skin and adjacent mucous membranes
• Upper respiratory tract
• Gastrointestinal tract, including mouth
• Outer portion of urethra
Influence the development of organs
• Prevent the overgrowth of harmful microorganisms
benefits of normal biota
• The general antagonistic effect “good” microbes have against intruder microorganisms
• Microbes in a steady, established relationship are unlikely to be displaced by incoming microbes
microbial antagonism
Factors That Weaken Host Defenses and Increase Susceptibility to
Infection
• Age: the very young and the very old
Genetic defects in immunity and acquired defects in immunity
(AIDS)
• Pregnancy
Caused by biota already in the body
• Can occur when normal biota is introduced to a site that was previously sterile
endogenous infections
A microbe whose relationship with its host is parasitic
• Results in infection and disease
pathogen
Capable of causing disease in healthy persons with normal immune systems
true pathogens
- The host’s defenses are compromised
- When they become established in a part of the body that is not natural to them
opportunistic pathogens
A system of biosafety categories adopted by the Centers for Disease Control and Prevention (CDC)
• Based on the general degree of pathogenicity and the relative danger in handling these pathogens
biosafety levels
Degree of pathogenicity
virulence
• Any characteristic or structure of the microbe that contributes to toxin production or induction of an injurious host response
virulence factor
: a minimum number of microbes required for an infection to proceed
Infectious dose (ID)
Microbes with a smaller infectious dose have greater virulence
t or f
true
A characteristic route taken by a microbe to initiate infection
• Usually through skin or mucous membranes
portal of entry
Source of the infectious agent:
originating from outside the body
- The environment, another person, or animal
exogenous
Source of the infectious agent:
already existing on or in the body
- Normal biota or a previously silent infection
endogenous
Sites of entry:
• Nicks
• Abrasions
• Punctures, some tiny and inapparent
• Intact skin is a very tough barrier that few microbes can penetrate
t or f
true
• Some infectious agents create their own passageways into the skin using digestive enzymes
t or f
true
• Entry through food, drink, or other ingested substances
• Adapted to survive digestive enzymes and abrupt pH changes
The Gastrointestinal Tract as Portal
Gateways to the respiratory tract:
• Oral cavity
• Nasal cavity
• Pathogens transmitted by sexual means
• Account for 4% of infections worldwide
• 13 million new cases in the United States each year
Sexually transmitted infections (STIs):
Entry points through the skin or mucosa of:
• Penis
• External genitalia
• Vagina
• Cervix
Urethra
• Formed by maternal and fetal tissues
• Separates the blood of the developing fetus from that of the mother
The placenta is an exchange organ:
Common infections of the fetus and neonate:
• Toxoplasmosis
• Other diseases: syphilis, coxsackievirus, varicella-zoster virus,
AIDS, chlamydia
• Rubella
• Cytomegalovirus
• Herpes simplex virus
A process by which microbes gain a more stable foothold on host tissues
• Dependent on binding between specific molecules on both the host and pathogen
• A particular pathogen is limited to only those cells and organisms to which it can bind
• Once attached, a pathogen can invade body compartments
adhesion
Chemical communication between nearby bacteria critical to establishment of infection
quorum sensing
White blood cells that engulf and destroy pathogens by means of enzymes and antimicrobial chemicals
phagocytes
• Virulence factor used by pathogens to avoid phagocytes
• Circumvent some part of the phagocytic process
antiphagocytic factors
Structures, products, or capabilities that allow a pathogen to cause infection in the host
• Adaptations that a microbe uses to invade and establish itself in a host
• Determine the degree of tissue damage that occurs
virulence factors
Secreted by pathogenic bacteria, fungi, protozoa, and worms
• Break down and inflict damage on tissues
• Dissolve host’s defense barriers and promote the spread of microbes into deeper tissues
exoenzymes
A specific chemical product of microbes, plants, and some animals that is poisonous to other organisms
toxin
• Secreted by a living bacterial cell to the infected tissues
exotoxin
• Not actively secreted
• Shed from the outer membrane
• Only found in gram-negative bacteria
endotoxin
is a trait not solely determined by microorganisms
is a consequence of an interplay between microbe and host
pathogenecity
Microbe enters the body and remains confined to a specific tissue:
• Boils
• Fungal skin infections
• Warts
localized infection
When an infection spreads to several sites and tissue fluids, usually in the bloodstream
systemic infection
measles, rubella, chickenpox, AIDS
viral
brucellosis, anthrax, typhoid fever, syphilis
bacterial
Exists when the infectious agent breaks loose from a local infection and is carried to other tissues
focal infection
infection remains localized, toxins are carried through the blood to the target tissue
toxemia
Several agents establish themselves simultaneously at the infection site
mixed infection
gas gangrene, wound infections, dental caries, human bite infections
Polymicrobial diseases:
Initial infection
primary infection
• Occurs when a primary infection is complicated by another infection caused by a different microbe
secondary infection
• Come on rapidly
acute infections
• Progress and persist over a long period of time
chronic infection
Any objective evidence of disease as noted by an observer
• More precise than symptoms
sign
• Subjective evidence of disease as sensed by the patient
symptom
A disease identified or defined by a certain complex of signs and symptoms
syndrome
Earliest symptom of disease
inflammation
- Accumulation of fluid in afflicted tissue
edema
- Walled-off collections of inflammatory cells and microbes in the tissues
• Granulomas and Abscesses
- Swollen lymph nodes
• Lymphadenitis:
Increase in the level of white blood cells
leukocytosis
Decrease in the level of white blood cells
leukopenia
General state in which microbes are multiplying in the blood and are present in large numbers
septicemia
Small numbers of bacteria are present in the blood but not necessarily multiplying
bacteremia
Presence of viruses in the blood,
whether or not they are actively
multiplying
viremia
• Asymptomatic, subclinical, or inapparent infections:
Infections That Go Unnoticed
• Host is infected but does not manifest the disease
• Patient experiences no symptoms or disease and does not seek medical attention
• Most infections are attended by some sort of sign
Asymptomatic, subclinical, or inapparent infections
Avenue for pathogens to exit the host
• Secretion
• Excretion
• Discharge
• Sloughed tissue
portal of exit
Respiratory and Salivary Portals
• Escape media for pathogens that infect the upper and lower respiratory tract:
• Mucus
• Sputum
• Nasal drainage
• Other moist secretions
The outer layer of skin and scalp is constantly being shed into the environment
• Household dust is composed of skin cells
• A single person can shed several billion skin cells a dav
skin scales
Some intestinal pathogens cause irritation in the intestinal mucosa that increases the motility of the bowel
• Resulting diarrhea provides a rapid exit for the pathogen
• Helminth worms release eggs and cysts through the feces
• Feces containing pathogens are a public health problem when allowed to contaminate drinking water or when used to fertilize crops
fecal exit
Blood-feeding animals are common transmitters of pathogens:
Ticks
• Fleas
• A dormant state of an infectious agent
• During this state, a microbe can periodically become active and produce a recurrent disease
• The agents of syphilis, typhoid fever, tuberculosis, and malaria also enter
latency
• Long-term or permanent damage to organs and tissues
• Meningitis can result in deafness, strep throat can lead to rheumatic heart disease, Lyme disease can cause arthritis, and polio can produce paralysis
sequelae
The time from initial contact with the infectious agent to the appearance of first symptoms
incubation period
• When the earliest notable symptoms of infection appear
prodromal period
Infectious agent multiplies at high levels, exhibits its greatest virulence, and becomes well established in its target tissue
acute phase
• Patient responds to infection and symptoms decline
convalescent stage
Primary habitat in the natural world from which a pathogen originates
reservoir
Distinct from a reservoir
• Individual or object from which an infection is acquired
source
Distinct from a reservoir
• Individual or object from which an infection is acquired
source
A person with a cold contaminates a pen, which is then picked up by a healthy person
indirect permission
A sick person sneezing on a healthy
direct transmission
• A person who is fully recovered from his hepatitis but is still shedding hepatitis A virus in his feces uses suboptimal handwashing technique and then contaminates food which a healthy person ingests
human carriers
An individual who inconspicuously shelters a pathogen and can spread it to others without knowing
carrier
• In epidemiology, a live animal that transmits an infectious agent from one host to another
• Majority of _____ are arthropods
vectors
Actively participates in a pathogen’s life cycle, serving as a site in which the pathogen can multiply or complete its life cycle
- Communicates the infectious agent to the human host by biting, aerosol formation, or touch
biological vector
- Not necessary to the life cycle of an infectious agent
— Merely transport the pathogen without being infected
mechanical vector
An infection indigenous to animals but also transmissible to humans
• Human is the dead-end host and does not contribute to the natural persistence of the microbe
• Spread of disease is promoted by close associations of humans with animals
zoonosis
Microbes have adapted to nearly every habitat in the biosphere
• Soil, water, air, the built environment
• Most are saprobic and cause little harm to humans
• Some are opportunists
• A few are regular pathogens
non living reservoir
Animals (other than humans and arthropods):
• Can be directly transmitted to humans
• Can be transmitted to humans via vectors
• Can be transmitted through vehicles such as water
living reservoir
Occurs when an infected host can transmit the infectious agent to another host and establish infection in that host
communicable disease
The agent is highly communicable, especially through direct contact
contagious
Does not arise through transmission of the infectious agent from host to host
non communicable
Disease is spread through a population from one infected individual to another
horizontal transmission
kissing and sex (Epstein-Barr virus, gonorrhea)
direct (contact) transmission
fomites, vehicles, parenteral (via injection into deeper tissues)
indirect transmission
Transmission from parent to offspring via ovum, sperm, placenta, or milk
vector transmission
Any inanimate material commonly used by humans that can transmit infectious agents
vehicle
• An inanimate object that harbors and transmits pathogens
• Not a continuous source of infection
fomite
• Fecal carrier with inadequate personal hygiene contaminates food during handling, and an unsuspecting person ingests it
Oral-fecal route
Indoor air can serve as a support medium for the suspension and dispersal of respiratory pathogens via droplet nuclei and aerosols
air
Dried microscopic residues created when microscopic pellets of mucus and saliva are ejected from the mouth and nose
droplet nuclei
Suspensions of fine dust or moisture particles in the air that contain live pathogens
aerosols
• Infectious diseases that are acquired or develop during a hospital stay or stay in another health-care facility
• Rates of HAls can range from 0.1 to 20% of all admitted patients
Healthcare-Associated Infections
Practices that lower the microbial load in patients, caregivers, and the hospital environment
medical asepsis
• Ensuring all surgical procedures are conducted under sterile conditions
surgical asepsis
• Implements proper practices and procedures throughout the hospital
Infection control officer
• Developed a standard for determining causation of disease that stood the test of scientific scrutiny
Robert Koch
• Essential aim of the study of infection and disease is determining the etiologic agent (causative agent)
Koch’s Postulates to Determine Etiology
- A series of proofs that established classic criteria for etiologic studies
Koch’s postulates
• Effects of diseases on the community
• Involves the study of the frequency and distribution of disease and distribution of disease and other health-related factors in defined populations
epidemiology
• Notifiable diseases
• By law, some diseases must be reported to authorities
• Other diseases are reported on a voluntary basis
reportable diseases
• Responsible for keeping track of infectious diseases nationwide
• Part of the U.S. Public Health Service
• Morbidity and Mortality Report: a weekly notice of diseases published by the CDC
• The CDC shares its statistics on disease with the World Health Organization (WHO) for worldwide tabulation and control
Centers for Diseases Control and Prevention
• Total number of existing cases with respect to the entire population
Prevalence of disease
• Measures the number of new cases over a certain time period
• Also known as case or morbidity rate
Incidence of disease
• Measures the number of deaths in a population due to a certain disease
Mortality rate
One in which the infectious agents came from a single source
point source epidemic
• Result form common exposure to a single source of infection that can occur over a period of time
Common-source epidemic
• Results from an infectious agent that is communicable from person to person and is sustained over time in a population
Propagated epidemic
• Spread of an epidemic across continents
pandemic
The first patient found in an epidemiological investigation
index case
An infectious disease that exhibits a relatively steady frequency over a long time period in a particular geographic locale
endemic
• Occasional cases are reported at irregular intervals in random locales
Sporadic disease
