MICRO FINAL! Flashcards
infection
colonization or invasion of the body by pathogens
disease
infection that results in any change from a normal state of health
etiology or etiology agent
cause of an infectious disease
pathogenesis
manner in which a disease develops in the host
primary (true) pathogen
causes disease in healthy individuals with normal immune defenses
secondary (opportunistic) pathogen
cause disease in immunocompromised individuals or when displaced
Two types of secondary pathogens?
- saprophytes in the environment
2. one’s own normal flora
normal flora also known as?
indigenous flora, normal microbiota, resident flora
the human body begins to be colonized by normal flora?
during and immediately after birth
local infection
microbes, its enzymes or toxins confined to a particular body site(target tissue)
focal infection
microbes disseminate from focus of infection, but target a specific body site
systemic infection
microbes or toxins disseminate throughout the body to several sites/organs via blood/lymph
synergism or mixed infection
microbes work together to digest host target tissue
asymptomatic
infection that produces no noticeable symptoms, but microbes are active and host acts as carrier
primary infection
acute infection that causes initial illness
acute infection
infection that has rapid onset and is short lived
secondary infection
opportunistic infection that occurs during or following another already existing primary infection
chronic infection
infection develops slowly, body reaction is less severe but disease is continual or recurrent for long periods
subacute infection
infection that is intermediate between an acute and a chronic infection
latent
infection in which microbes remain dormant in tissues for years without symptoms, but are periodically reactivated
nosocomial infection
infectious disease acquired through a stay in the hospital or other health care facility
teratogenic
birth defects caused by infectious agent or other agents(smoke,alcohol) that cross the placenta
sequela
a condition, pathologic effect such as arthritis as a consequence of an infectious disease
incubation period
time interval between initial contact with pathogen and 1st signs and symptoms of disease(1 or 2 weeks)
prodromal period
short period following incubation period in which symptoms are mild.
ex: aches, fatigue,koplik spots
period of illness
stage when disease is acute and patient exhibits signs and symptoms
ex. fever,chills,gi disturbances, myalgia
period of decline
signs and symptoms of the disease subside, lasts 1 to several days and patient is vulnerable to secondary infection
period of convalesence
period of recovery when patient regains his strength and body returns to a healthy state
signs
objective and measurable, noticed by observer
ex: fever, rash, increase WBC, decrease antibodies
symptoms
subjective, felt by patient
-ex: aches, pain, nausea, fatigue
reservoir
a host or environment that supports the survival, multiplication and spread of pathogens
*reservoir and host are not always the same. for example HAV reservoir is “humans” but its source is “food”
Reservoirs of infectious agents
- Humans
- Animals
- Environment
Humans
act as active or passive carriers to transmit infectious agents human to human directly or indirectly.
- types of human carriers: asymptomatic, incubating, convalescent, chronic or latent carriers.
- how humans can act as passive carriers: bed pans and eating utensils
Animals
large animals or arthropod/insect/zoonotic infection transmit pathogen animal to human
- biological vector: animals that actively participate in pathogens life cycle
ex: mosquito-malaria - mechanical vector: animals body part transmits pathogens to human thru food or other means
ex. bacillary dysentery
Environment
-vehicles/contaminated materials such as air, water,soil,food,fomites,media, blood etc..
fomite
any contaminated object
ex. door knob,penny,syringe,towel
communicable disease
microbial disease spread from one host to another via direct or indirect contact
non-communicable disease
microbial disease NOT spread from one host to another
means of direct contact transmission
- horizontal
- vertical
- biological vector
- droplet
horizontal
transmission occurs when one host physically contacts another host via touching, kissing, sex
vertical
transmission is when an infectious agent is transmitted from parent to offspring via placenta or breast milk
biological vector transmission
arthropod
ex: mosquito bites infected host and transmits agents to another host
droplet tranmission
one host sprays respiratory secretions(mucus, saliva, sputum) on another host
indirect contact transmission
- fomite
- food borne
- water borne
- other media
- droplet nuclei
- aerosol
fomite transmission
an infected host contaminated an object
ex: doorknob=uninfected host touches it
food borne transmission
food such as custard, contaminated with feces or urine is eaten
water-borne transmission
infectious agent in water
ex. cholera is deposited w/ feces and ingested
other media transmission
examples: iv fluid, blood,serum,milk
droplet nuclei transmission( a type of air borne transmission)
-contaminated fine moisture droplets or dust particles that remain suspended in indoor air for long periods
epidemiology
the study of frequency and spread of disease in a defined community or population
prevalence
refers to the number of old or new cases(% of a population) having a disease over a given time period
incidence
refers to the number of new cases contracting a disease over specific period of time
epidemic
a disease introduced from the outside that affects a large number of people in a community simultaneously, many exhibit symptoms
ex: tuberculosis
endemic
a disease prevailing continuously in a community, few exhibit symptoms
ex: common cold
pandemic
a disease that spreads across continents
-worldwide ex: AIDS
sporadic
a disease in which a few isolated cases occur in widespread locations
-ex: tetanus in US
portal of entry
routes through which pathogens/microbes enter the body skin or mucous membranes
various portals of entry
- resp route
- fecal oral route
- tranplacental route
- intact skin
- genitourinary route
- parenteral route
resp route
contaminated moisture droplets or dust particles are inhaled through the rest. route.
ex. =measles
fecal-oral route
food or water contaminated w/ feces or urine is ingested through the fecal-oral route
ex. cholera, HAV
transplacental route
infectious agents are transmitted from mother to infant through the placenta or birth canal via tranplacental route
ex: rubella, HIV, toxoplasmosis, syphillis
intact skin
microbes gain direct access to sterile tissues beneath the skin through hair follicles of sweat glands via the intact skin route.
-ex staphylococcal skin infections such as fununcles
genitourinary route
sexual contact allows microbes to enter the body through the genitourinary route
ex: HIV, HBV, HPV
parenteral route
microbes gain direct accèss to tissue beneath the skin or MMs through an injury or wound
ex: impetigo, cellulitis
STORCH
an acronym that represents the most common transplacental infections of the fetus and neonate
virulence
the degree of pathogenicity or the ability of the microbe to invade that host and or produce toxins
virulence factors
properties possessed by microbe(esp bacteria) that allow it to attach, invade and evade host barriers to disease
4 main categories of virulence factors:
- numbers of invading microbes or amount of toxin
- surface components on microbes
- exoenzyme
- toxin
numbers of invading microbes or amount of toxin
- lethal dose 50(LD50)=minimum amount of toxin to cause death in at least 50% of inoculated lab animals or a human population
- infectious dose 50(ID50)= minimum number of microbes to cause death in at least 50% of inoculated lab animals or a human population
- the lower the number of invading microbes or dose of toxin, the greater the virulence of the microbe
surface components on microbes
- allow microbes to attach and enter host cells or evade host defenses such as phagocytes(macrophages, neutrophils), cytotoxic T cells, antibodies, NK cells or complement
- bacterial capsule, fimbriae, flagella, or cell wall M protein
- protozoan=flagella or cillia
- Helminth=hooks or suckers
- viral spikes
- abscesses(staph) or granulomas(TB)
Exoenzyme
- enzyme/protein products produced inside bacterial cells and released to outside body fluids
1. coagulase: cause fibrin to clot(coagulates blood plasma)
2. kinase: breaks down fibrin clots(aid in spread of bacteria)
3. Hyaluronidase: breaks down Hyaluronic acid in CT
4. Collagenase: breaks down collagen in muscle(aids spread of bacterium)
5. Mucinase: ingests mucus coating on MMs
6. IGA protease: cleaves and destroys IGA Abs(prevent MM adhesion)
Toxin
poisonous substances produced by certain microbes and released into body fluids
- conditions associated with bacterial toxins in the body
1. toxemia=refers to toxins in the blood
2. septcemia=refers to persistant pathogens or toxin in the blood
3. Bacteriemia=refers to transient bacteria in the blood
4. Viremia=refers to viruses in the blood
5. intoxication=ingestion of toxins in food
6. sepsis: refers to a systemic inflammatory response due to microbes or toxins in blood spreading from focus of infection
two types of toxins produced or found in bacteria:
exotoxins and endotoxins
exotoxins
soluble proteins produced inside bacterial cells(mainly g+) and released to body fluids
cytotoxin are exotoxins that kill a variety of host cells, certain exotoxins and give examples of each.
1.A-B toxins: B part binds host cells, A, active enzyme inhibits protein synthesis and destroys host cells
ex: diptheria toxin
- Membrane Disrupting Toxins: disrupts host membranes and lyse/kill host cells. ex. diphtheria toxin
- Superantigens: Toxin non-specifically binds TH cells which release cytokines—> destructive immune response
ex. STAPH TSST-1 toxin
endotoxin(lipid A)
released upon G- CW lysis/death by macrophages, and induce macrophages to secrete large amounts of cytokines in host body fluids at toxic levels, leading to destructive/damaging immune response
list some important damaging immune responses in the human host that are due to endotoxins
- hemorraging under the skin
- DIC
- pyrogenic response
- endotoxic/septic shock
Microbial diseases of the skin
- Diptheroids
- Staphylococci
- Malassezia Furfur
