6A Requirements for Infection Flashcards
name 5 requirements/steps for successful infection
- entry: getting in
- establishment: staying in
- defeat host defenses
- damage the host: release resources
- exit host to transmit to other host
what are portals of entry? name 3 examples
any point at which a pathogen enters
- mucous membranes
- skin
- parenteral route
mucous membranes are in direct contact with ____
external environment
name 3 places mucous membranes are found in the order of most to least common portal of entry
- respiratory tract
- GI tract
- genitourinary tract
name 8 common respiratory pathogens
- adenoviruses: streptococcus pneumoniae, staphylococcus aureus, myobacterium tuberculosis, bordetella pertussis
- influenza
- rubella
- varicella-zoster
name 10 common GI pathogens
- E(scherichia) coli
- clostridium botulinum
- enterococcus faecalis
- shigella spp
- salmonella
- helicobacter pylori
- candida
- poliovirus
- norovirus
what is the portal of entry of sexually transmitted infections?
genitourinary tract
why are urinary tract infections more common in women than men?
- shorter urethra
- proximity to anus
name 8 common genitourinary pathogens
- myobacterium smegmatis
- chlamydia trachomatis
- neisseria gonorrheae
- trichomonas vaginalis
- herpesviruses
- human immunodeficiency virus
- E(scherichia) coli
- candida
what is the cause of 90% of UTIs?
E(scherichia) coli
what is the largest organ OF the body?
skin
what is the impermeable barrier unless broken, where many microorganisms reside?
skin
what does the parenteral route refer to?
breaks in skin that allow passage of microbes
normal flora causing infection are called ____
opportunistic pathogens
opportunistic pathogens entering via the parentral route depend on…
- cuts
- abrasions
- injections
- wounds
- surgical incisions
how do pathogens attach to the surface or cells or tissues?
- use virulence structures such as capsules or fimbraie
- use adhesins to attach to tissues
name an example of an adhesion beginning a process resulting in an accumulation of bacteria called a biofilm
plaque on teeth
(life activities of bacteria plus their presence results in formation of plaque)
how do spirochetes enter tissues?
lengthy process of corkscrewing
some pathogens can double their numbers every ____
20 mins
how do bacteria reproduce?
binary fission
what is passive defense?
using intrinsic features of the pathogen to protect themselves
(eg. cell walls, lipopolysaccharide mem, or extrinsic factors produced from existing resources at expense of host (capsules, M protein))
name an example of a passive defense
bacterial cell walls (peptidoglycans)
name an example of how a pathogen with a gram+ cell wall defends itself
streptococcus spp
- uses M proteins to increase adhesion to host tissue and inhibit phagocytosis
how do pathogens with a gram- cell wall defend themselves?
- very thin but compensate by having outer lipopolysaccharide membrane (endotoxin)
- endotoxin lipid A elicits very powerful immune response
name an example of how acid-fast organisms protect themselves
myobacterium species (tuberculosis, leprae)
- inhibits phagocytosis
- inhibits antibiotics
capsules protect against ____
phagocytosis
what is active defense?
attacking host defenses
- produced by microbes solely for “attack” (eg. toxins & enzymes)
why do pathogens hide inside host cells?
as a way to defeat the host
- protection from host immune response
- viruses are obligate intracellular parasites
what do bacteria use as a transport system?
cell microtubules and microfilaments
name 2 types of damage to a host
- presence and activity of pathogens (eg. pus)
- host defense mechanisms (eg. vomitting, diarrhea, sneezing)
direct damage to the host…
- is obvious
- includes destruction of host cells & tissues
- controlled by host immune response
indirect damage to the host…
involves systemic infection as a result of toxin production by the pathogen
active defense involves the production of ____ which function to…
- extracellular enzymes
- increase protection against host defenses
- enable spread of infection by attacking and killing host defensive cells
name 6 examples of bacterial enzymes
- leukocidins
- hemolysins
- coagulase
- kinase
- hyaluronidase
- collagenase
function of leukocidins
destroy WBCs
function of hemolysins
attack both RBCs and WBCs
function of coagulase
formation of fibrin clots (wall away tissue)
function of kinase
breaks down fibrin and destroys clots
function of hyaluronidase
breaks down CT
function of collagenase
breaks down collagen
name 2 types of bacterial toxins
- exotoxins
- endotoxins
name 3 characteristics of bacterial toxins
- very poisonous
- soluble in aqueous solutions
- easily diffusible into blood & lymph causing distal pathology
outcomes of bacterial toxins
- can be fatal
- S&S: fever, shock, diarrhea, cardiac & neuro trauma, destruction of BVs
characteristics of bacterial endotoxins
- produced by and exported from certain pathogens and then enter host cells
- some of most lethal substances known
- usually an enzymatic protein soluble in blood & lymph
- rapidly diffuse into tissues where they inhibit metabolic function
what are plasmids?
genes coding for toxin production
name 3 types of exotoxins
- cytotoxins
- neurotoxins
- enterotoxins
function of cytotoxins
kill cells
function of neurotoxins
interfere w neurological signaling
(produce exotoxins for affinity for CNS tissue)
function of enterotoxins
affect lining of digestive tract
name 2 examples of cytotoxins
- bacillus anthracic
- corynebacterium diphtheraie
characteristics of bacillus anthracis
- gram+ spore-forming bacillus
- increases vascular permeability in host tissues
- cytotoxin
characteristics of corynebacterium diphtheraie
- gram+ bacillus
- inhibits protein synthesis
- single molecule can kill a host cell (cytotoxin)
name 2 etiologic agents of neurotoxins
- clostridium tetani
- clostridium botulinum
when is antibiotic therapy ineffective for neurotoxins?
once exotoxin has been produced
characteristics of clostridium tetani
- gram+ spore-forming bacillus
- produces toxin “tetanospasm”
- neurotoxin
what are the effects of tetanospasm?
- prevents muscle relaxation
- uncontrollable convulsive muscle contractions
- “lockjaw”
- opisthotonus
tetanus spores require ____
low O2 levels
(area of necrosis surrounding injury, spores germinate)
how do bacteria cause tetanus?
- bacteria do not cause damage to tissue, but produce toxin
- toxin enters presynaptic terminals of LMNs
- travel to CNS
factors affecting mortality in tetanus
- location of lesion
- incubation period
- age (highest in infants & elderly
- death results from exhaustion and respiratory failure
characteristics of clostridium botulinum
- gram+ spore-forming bacillus
- inhibits release of Ach
- flaccid (limp) paralysis of skeletal m
- “botox”
- neurotoxin
pathogenesis of botulism
- begins w cranial n palsy
- develops into descending symmetrical motor paralysis
- may involve diaphragm
- no fever or inflammation
- no obvious sign of infection
progression of botulism
- symmetrical paralysis
- most serious complication = complete respiratory paralysis
- limp/flaccid paralysis
- mortality rates: 10-20%
- nervous system dysfunction
describe the nervous system dysfunction seen in patients with botulism
- ocular (blurred vision, REM)
- laryngeal
- diaphragm
- trunk
- extremities
name 3 categories of botulism
- food poisoning
- infant botulism
- wound contamination
foodborne botulism is classified as and ____
intoxication (not an infection)
manifestation of foodborne botulism
- starts 12-36hrs post-ingestion of toxin
- nausea, dry mouth, occasional diarrhea
pathogenesis of foodborne botulism
- toxin absorbed directly through intestinal tract
- reaches neuromuscular junction via bloodstream
- binds & inhibits release of Ach
- causes muscular paralysis
pathogenesis of infant botulism
- occurs between 3wks to 8mo
- organism introduced upon weaning or raw honey
signs & symptoms of infant botulism
- constipation
- poor muscle tone
- lethargy
- feeding problems
- vision problems
- paralysis
wound botulism
- very rare
- seen in IV drug users
- begins w weakness in extremities used as injection sites
name 2 examples of enterotoxins
- vibrio cholerae
- staphylococcus aureus
characteristics of vibrio cholerae
- gram- vibrio (bacillus)
- causes release of large amount of electrolytes resulting in: lethal diarrhea (‘rice water stools’), vomiting
- enterotoxin
characteristics of staphylococcus aureus
- gram+ coccus
- toxic shock syndrome
- enterotoxin
toxic shock syndrome
- AKA common food poisoning
- excessive loss of electrolyte fluids resulting in hypotensive shock
- caused by staphylococcus aureus
characteristics of bacterial endotoxins
- intrinsic part of gram- bacterial cell wall
- released upon death of bacterium
- released in form of lipid A
what do endotoxins (lipid A) cause?
- chills
- fever
- aches
- muscle weakness
- disseminated intravascular clotting
viral host cell damage is called ____
cytopathogenic effect (CPE)
name 3 ways that viral pathogenic effects can occur
- viral overload
- cytocidal effects (killing of host cells)
- non-cytocidal effects (damage caused by host defenses)
transmission is dependent upon…
organism and system infected
(how it got in is how it gets out)
what are 3 principles of transmission?
- where are pathogens found
- what are the mechanisms of transmission
- how can the chain of transmission be broken
what are reservoirs of infection?
places where pathogens grow and accumulate
what are mechanisms of transmission?
various ways pathogens move from place to place
name 3 potential reservoirs of pathogens
- human
- animals
- non-living
human reservoirs
- sick people: easy to identify
- carriers: those who are infectious but never show signs or symptoms
what are zoonotic diseases?
those infections that may be transmitted from animals to humans
name 8 examples of zoonotic diseases
- anthrax
- brucellosis
- cat scratch fever
- lyme
- plague
- TB
- ringworm
- rocky mountain spotted fever
non-living reservoirs
- include water, food, soil
- fecal-oral transmission
- food spoilage
- soil dwelling bacteria may be transmitted through human activity or animal husbandry
name 3 mechanisms of transmission
- contact
- vehicle
- vector
when does contact transmission occur?
when an uninfected person is exposed to a pathogen via touching or proximity with an infected individual, animal or object
name 3 types of contact transmission
- direct
- indirect
- droplet
direct contact transmission
there is no intermediary between the infected person/animal and uninfected person
indirect contact transmission
occurs through intermediates that are non alive such as tissues, handkerchiefs, towels, bedding, contaminated needles
intermediates that are not alive are called ____
fomites
droplet transmission
spread through aerosolized saliva, mucous, sputum
(i.e. talking, laughing, sneezing)
vehicle transmission
pathogens “ride” via water, food, air
vector transmission
pathogens are transmitted to a healthy person by a carrier known to be associated with a certain disease
what is the most common vector transmitter? name examples.
arthropods
- fleas
- ticks
- body lice
- mosquitoes
- flies
name 2 methods of vector transmission
- biological (eg. insect bite)
- mechanical (eg. insects depositing on food)
name 6 factors affecting disease transmission
- age
- gender
- lifestyle
- occupation
- geography
- general health
the host’s ability to mount a defense is called ____
immunocompetence
damaged host defenses result in…
disease potential
name 7 examples of people considered vulnerable or immunocompromised
- HIV-AIDS
- genetic immunodeficiency diseases
- chemotherapy
- broad-spectrum antibiotics
- premature and neonates
- health care workers
- elderly
Koch’s Postulates
conditions in order to “communicate” disease:
- same pathogen must be present in every case of the disease
- pathogen must be isolated from sick host and purified
- pure pathogen must cause the same disease when given to infect hosts
- pathogen must be re-isolated from newly infected hosts
name the 5 periods of disease development
- incubation period
- prodromal period
- period of illness
- period of decline
- period of convalescence
incubation period
no signs or symptoms
prodromal period
mild symptoms
period of illness
major signs & symptoms
at what period of disease development is the immune response the strongest?
period of illness
period of decline
signs & symptoms wane but highest chance of secondary infection
period of convalescence
recovery
what is epidemiology?
- study of factors and mechanisms involved in frequency and spread of diseases or other health-related problems
- used to study disease and also to design methods for control and prevention
what is prevalence and what is it used for?
- total # of people infected within a population at any given time
- used to measure strength and length of a particular disease
“streaming video”
what is incidence and what is it used for?
- number of new cases contracted within a set population in a specific period
- provides a reliable indication of the spread of a disease
“snapshot”
what is morbidity?
number of people affected by disease during a set period divided by total population
what is mortality?
number of deaths due to a specific disease during a specific period divided by total population
name 3 levels of disease occurrence
endemic
epidemic
pandemic
endemic disease
diseases found constantly within a population
epidemic disease
incidence of disease suddenly higher than expected in a specific region
name 2 types of epidemic disease
common-source
propagated
common source epidemic
- arises from contact with contaminated substances (fecal contamination of water; improperly prepared/stored food)
- affect large numbers of people but once source is identified quickly subside
propagated epidemic
- amplification of number of infected individuals as person-to-person contact occurs
- stay in population for long periods
- more difficult to control until patient zero found
pandemic
diseases that occur in epidemic proportions
name 2 types of epidemiological studies
descriptive
analytical
what are descriptive epidemiological studies concerned with?
- physical aspects of patients and spread of disease
- traces outbreak and identifies first case
what are analytical epidemiological studies concerned with?
- correlation: cause and effect hypothesis
- always uses a control group
what is often the most practical and feasible study to conduct?
observational
observational/descriptive studies
- investigator observes occurrence of condition/disease in population groups that have assigned themselves to a certain exposure
- more natural settings, representative of target pop
- little control, susceptible to distorting influences
cohort study
type of medical research used to investigate the causes of disease, establishing links between risk factors and health outcomes
prospective cohort study
- hypothesis formed about potential cause of disease
- observe a cohort of ppl over time & collect relevant data
- detect changes in health in relation to potential risk factors
disease reporting
health departments of local and state gov’t require reports of certain diseases
what are nationally notifiable diseases?
diseases that must be reported to the CDC
