unit 7 micro Flashcards
pathology is
the study of diseases
etiology is
the cause of disease, typically the causative organism
pathogenesis is
the progression of a disese
infection occurs when a person is
colonized with a microbe with NO change in the state of health
disease occurs when a person is
colonized with a microbe with A change in state of health
a pathogen is a
microorganism that can cause a disease
the microbiome is all the
microorganisms associated with a certain species
normal flora (resident microbiota) are
microorganisms that constantly live in/on our bodies
transient flora (transient microbiota) are
microorganisms that are temporarily found in/on our bodies
competitive inhibition is
the mechanism in which our normal flora protects us
occupies all available sites, competes for nutrients, and prevents pathogen
symbiotic relationships are
partnerships or associations between 2 species
mutualism
2 species that benefit from each other (E. coli which obtains nutrients in our intestine, in exchange for making vitamin K)
commensalism
one partner benefits while the other is unaffected (S. epidermidis uses dead skin cells as nutrients)
parasitism
one partner benefits at the cost of the other partner
sign
an objective and measurable deviation from normal structure or functioning of the host (temperature, blood pressure)
symptom
a subjective deviation from normal functioning of the host, and are felt or experienced by the patient (pain, headache)
syndrome
a group of signs or symptoms characteristics of a particular disease (toxic shock syndrome)
asymptomatic/subclinical
a disease with no noticeable signs or symptoms
a communicable infectious disease
is capable of being spread from person to person
a contagious disease is
easily spread from person to person
a zoonotic disease is
a disease that can be transmitted from non-human hosts to humans
a non-communicable infectious disease
is not spread from one person to another
an acute disease is
one where the pathogenic changes occur over a relatively short time and involve a rapid onset of disease conditions (flu)
a chronic disease is
where pathogenic changes occur over longer time spans, with continued replication of the causative pathogen (liver inflammation)
a latent disease is
where the causative pathogen goes dormant for extended periods of time with no active replication (herpes)
the morbidity rate is
the percentage or number of individuals with a disease
the prevalence measures
one aspect of morbidity, which is the number of individuals with a particular illness in a given population at a point in time
the incidence measures
another aspect of morbidity, which is the number of new cases in a period of time
the mortality rate is
the percentage or number of individuals that have died from that disease
a sporadic disease is
one seen only occasionally and usually without geographic concentration (tetanus)
an endemic disease is
one that is constantly present within a particular geographic region (common cold)
an epidemic disease is
one where a larger than expected number of cases occurs in a short time within a geographic region (influenza)
a pandemic disease is
an epidemic that occurs on a worldwide scale (COVID)
incubation period
occurs after the initial entry of the pathogen into the host
prodromal period
patient feels general signs and symptoms of the illness
period of illness
signs and symptoms are the most severe
period of decline
signs and symptoms begin to decrease
the patient is susceptible to secondary infections
period of convalesence
recovery phase, where the patient generally returns to normal functioning
in which stages is the patient contagious
all stages
describe the purpose of koch’s postulates
to determine etiology, or to correlate a specific disease
postulate 1 & exceptions
suspected pathogen must be found in every case of disease and not be found in healthy individuals
normal flora - many people can be colonized with pathogens but not present any signs/symptoms of disease
postulate 2 & exceptions
the suspected pathogen can be isolated and grown in pure culture
not all microbes can be cultured. for example, viruses and some species of bacteria
postulate 3 & exceptions
infected healthy test subject (who was susceptible) must develop the same signs and symptoms as before
ethical issues, especially if the diseases only have human hosts. it would not be appropriate to deliberately infected
not everyone is equally susceptible, due to predisposing factors and strength of immune system
postulate 4 & exceptions
pathogen must be re-isolated and is identical to the pathogen isolated in part 2
some pathogens can cause multiple disease
some diseases are caused by multiple pathogens
pathogenicity is
the ability of a microbial agent to cause a disease
virulence is
the degree to which an organism can cause disease
infectious dose or ID50 is
used to quantify the number of pathogenic cells or virions to cause an active infection in 50% of inoculated animals
** the lower the ID50, the smaller number of cells/virions required to cause an active infection
a reservoir is
a living organism or nonliving site that allows pathogens to replicate and survive over long periods of time, such as:
humans = if they do not display any symptoms, then they are referred to as carriers
animals = zoonoses
nonliving sites include water, air, food
transmission:
contact transmission - direct:
through actions such as kissing, touching, sex, or droplet sprays
can include contact between mucus membranes, can be site-specific
indirect contact:
involves the use inanimate objects called fomite that become contaminated (towels, doorknob)
vehicle transmission
transmission of pathogens through vehicles such as food/water, usually because of poor sanitation methods
or transmission of pathogens through air (airborne), due to aerosols where dust and fine particles can travel long distances
vector transmission
mechanical occurs when an animal carries a pathogen from one host to another without being infected itself
biological occurs when the pathogen reproduces within a biological vector that transmits the pathogen from one host to another
includes arthropod vectors (mosquitoes) & non-arthropod vectors (mammals)
stages of pathogenesis:
portal of entry
the anatomic site of entry
skin = where the pathogen enters or causes infection
mucus membranes = includes respiratory tract, GI
parenteral = where the pathogen enters through a wound in the skin (cut) or due to invasive procedures (IV)
stages of pathogenesis:
portal of exit
pathogens typically exit the body the way it entered
describe mechanisms for adherence
bacteria: fimbriae, capsule, adhesions
viruses: spikes, fibres
helminths: hooks, suckers
ways pathogens penetrate host: endocytosis
where cells are forced to uptake the pathogen; this can be done through the production of proteins called invasins
ways pathogens penetrate host: phagocytosis
where specific white blood cells will actively consume pathogens, but rather than being digested, the pathogens take over and replicate inside phagocytes
mechanisms pathogens developed to avoid host’s defenses
- cell structure such as capsule, or molecules = M protein & mycolic acid, can be used to evade phagocytosis
- enzymes that prevent antibody-mediated killing are called lg proteases
- enzymes that trigger the formation of blood clots, enabling bacteria to hide are called coagulases
- enzymes the dissolve blood clots, allowing bacteria to escape are called kinases
- the alteration of surface proteins to make the pathogen no longer recognizable is called antigenic variation
local infection is
where the pathogen is contained to a small location
systemic infection is
where the pathogen spread throughout the body
sepsis can occur in a systemic infection where
the microbes and/or toxins trigger an inflammation response so severe that the inflammation damages the body more than the infection itself
a primary infection occurs
in a host regardless of the host’s resident microbiota or immune system (common cold)
a secondary or opportunistic infection occurs
in situations that have already compromised the host’s defenses (yeast infection)
glycohydrolases
degrades connective tissue by separating cells, allowing for pathogens to pass deeper in the body
nucleases
degrades webs of DNA, produced by the immune system, to leave a cell and spread to other tissues
phospholipases
degrades cell membranes to escape phagocytosis or lead to lysis of target cells
proteases
digests proteins to amino acids, allowing the pathogen to pass deeper into the body
toxin
produced by microorganisms that can harm cells/tissues or trigger damaging immune responses
toxigenicity
the ability to produce toxins
toxemia
presence of toxins in the blood
production for endo/exo
exotoxins = produced inside some bacteria as part of their metabolism and then secreted
endotoxins = produced as part of a component of the outer membrane of the cell wall (lipid A - part of the lipopolysaccharide) released during cell lysis or multiplication
type of molecule for endo/exo
exotoxins: protein, often enzymes; (heat-labile)
endotoxins: lipid (heat-stable)
type of bacteria for endo/exo
exotoxins: mainly gram-positive, some gram-negative
endotoxins: only gram-negative
relative amount needed to be toxic for endo/exo
exotoxins: small amount
endotoxins: large amount
effects for endo/exo
exotoxins: specific
endotoxins: non-specific
exotoxins: A-B exotoxins
contains an active A component and a binding B component (tetanus toxin)
exotoxins: cytolytic toxins
leads to lysis of host cells (C. difficile)
exotoxins: superantigens
leads to a very intense immune response, leading to a sudden release of cytokines (toxic shock)
endotoxins
no further types, all endotoxin lead to the same general symptoms of fever, muscle aches, nausea but will vary in severity (EHEC)
epidemiology is
the study of geographical location, timing, occurrence and transmission of disease (includes etiology)
observational studies
information is gathered, subjects are not manipulated
types of observational studies
descriptive & analytical epidemiology
descriptive epidemiology
gathers information about a disease outbreak, allowing initial hypotheses to be formed (interviews with patients, examinations)
analytical epidemiology
selects specific groups to form more stronger hypotheses regarding causes of disease outbreaks
-data collected through: retrospective studies gather data from the past, prospective studies follow individuals and monitor their disease state
cohort method
follows or studies a group of people who share a characteristic
case control method
compares people with and without a disease, allowing scientists to determine the factors that can cause a disease
cross-sectional studies
analyze a random group of individuals and compares them to determine prevalence
experimental studies
evaluating hypotheses formed to study connections between diseases and possible causes/treatments
subjects are manipulated through clinical studies
efficacy of drugs, dietary items, physical exercise
use of double-blind studies to decrease bias - neither the subjects nor the researchers know who is a treatment case or not
healthcare-associated (nosocomial) infections
infection acquired at a healthcare facility, but not the initial cause for being in the facility
3 main factors that lead to increased prevalence of HAI
- high prevalence of pathogens: sick patients can be carriers, plus the large variety of pathogens present
- weakened immune systems: patients can be immunocompromised due to illness, medication or have had invasive procedures that allows for pathogen entry
- chain of transmission exists: people can be a direct link, or also fomites can indirectly transmit pathogens
describe top 3 sites of HAI from most to least common; name 3 common pathogens
- surgical site infection (S. aureus, epidermidis) & pneumonia (S. pneumoniae)
- urinary tract infections (E. coli, S. epidermidis & aureus)
- primary bloodstream infections (S. aureus & epidermidis)
universal precautions are
referred to as infection control procedures, meaning treating all blood and body fluids as potentially infectious to decrease transmission, wearing PPE, proper cleaning of all hospital equipment prior to invasive procedures, handwashing to prevent transmission
