Micro ch. 10-15

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Biology

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117 Terms

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Goals of antibacterial treatment
- disrupt/prevent bacterial infection without affecting the host too much
- kill micro bacteria
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Ideal drug
- not toxic to host cell
- relatively soluble
- does not lead to antimicrobial resistance
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Three factors needed to be known before therapy
1. identity of microorganism
2. how susceptible is the the microorganism to drugs
3. what is the condition of the person infected?
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Methods for testing antimicrobial susceptibility
Disc diffusion test/ Kirby-Bauer, tube dilution test
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Disc diffusion/ Kirby-Bauer test
looks at region of bacteria diffusion into media, small discs of antibacterial put onto medium, once incubated the "zone of inhibition" surround the disc is measured and compared with a standard of each drug
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Tube dilution test
antimicrobial is diluted serially in tubes of broth and inoculated with a pure culture, once incubated it is examined for growth
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Minimum Inhibitory Concentration
the smallest concentration (highest dilution) of a drug that visibly inhibits growth
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Therapeutic Index
ratio of the dose of the drug that is toxic to humans compared to its minimum effective dose
------> the smaller the ration the greater for potential toxic drug reactions
------> drug with highest TI has the widest margin of safety
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Failure of Antimicrobial treatment due to
1. Delivery of drug (able to reach target site)
2. resistance
3. what if it is polymicrobial?
4. consistent with treatment
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Goal of antimicrobial drugs
- Disrupting, inhibit
- interfere
- destroy
- selectively toxic
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Broad Spectrum drugs
drugs that target a wide range of microbes
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Narrow Spectrum drugs
drugs that target a small range/few microbes
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Drug classifications
1. targets cell wall
2. targets protein synthesis
3. targets folic acid synthesis
4. target cytoplasmic or cell membrane
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Drugs that target cell wall
penicillin, cephalusporins
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Drugs that target protein synthesis
2 types: aminoglycosides, tetracyclines
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Aminoglycosides
insert on sites on the 30S subunit and cause the misreading of mRNA, leads to abnormal proteins
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Tetracyclines
block the attachment of tRNA on the A acceptor site and stop further protein synthesis
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Drugs that target folic acid synthesis
sulfonamides
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Sulfonamides
interferes with folate metabolism by blocking ezymes
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Drugs that target cell membrane
polymyxins
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Polymyxins
interact with membrane phospholipids to break them down
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Biofilm treatment strategies
1. interrupting quorum sensing pathways
2. adding DNAse to antibiotic acids penetration through extracellular debris
3. interpreting devices with antibiotics prior to implantation
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Some antibiotics cause:
biofilms to form at a higher rate than they normally would
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Vaccines prevent
measles, mumps, hepatitus
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Virus diseases that need more effective medication s
aids, influenza, common cold
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Drug resistance
an adaptive response in which microorganisms begin to tolerate an amount of drug that would normally be inhibited
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microbes become resistant to a drug after
1. spontaneous mutations in critical chromosomal genes
2. acquisition of entire new genes or sets of genes via horizontal transfer from another species
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Mechanisms of drug resistance
1. targets the drug: production of lactum ring inactivates penicillin
2. alters its target/shape so antibiotic cannot recognize it
3. efflux pumps: pumps drugs out of bacteria
4. change in enzymatic pathway
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Probiotics
preparations of live micro-bacterium fed to animals and humans to improve intestinal biota
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Prebiotic
nutrients that encourage growth of beneficial microbes of the intestine
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Fecal transplant
treats reoccurent clostridiods difficile infection and ulcerative colitis; transfers feces from healthy via colonoscopy
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Colonization
resident microbiota
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Infection
microbes get past barrier
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Disease
deviation from health
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Infectious disease
pathogenic state
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Contamination
excessive amount of growth
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Pathogen
a microbe whose relationship is with its host parasitic and results in infection and disease
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Pathogenicity
an organism's potential to cause disease
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True pathogens
capable of causing a disease in a healthy organism
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Opportunistic pathogens
has potential to cause harm but relies on compromised immune system
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Virulence
relatively severity of disease by a particular microbe; degree of pathogenicity
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Virulence factor determined by:
1. establish
2. cause
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Virulence factor
a microbes structures or capabilities that allow it to establish itself in a host and cause damage
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Polymicrobial Infections
majority of infections are polymicrobial with contributions from more than one microbe
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Exogenous
microbe introduced from outside
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Endogenous
microbe introduced from inside
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Steps to becoming established
1. portal of Entry
2. attaching to host cell
3. surviving host defense
4. causing disease
5. Vacating the host- portals of exit
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Portal of entry
the route that a microbe takes to enter the tissues of the body to initiate an infection
- pathogens specifically adapted to specific portal of entry but pathogens can enter more than one portal
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Infectious dose
the minimum number of microbes necessary to cause an infection to proceed; microorganisms with smaller infectious doses have greater virulence
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attaching to the host cell
Adhesion: process by which microbes gain a more stable foothold on host tissues
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Causing disease
three ways: directly, indirectly, epigenetic changes
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Directly
actin of exoenzymes, toxins
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Exoenzymes
enzymes secreted by microbe that break down and inflict damages on tissues; dissolves the hosts defense barriers to promote the spread of disease to the other tissue
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Toxins
a specific chemical product of microbes that is poisonous to other organisms
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Toxin types
Neurotoxins: act on nervous system
Enterotoxins: act on intestine
Hemotoxins: lyse red blood cells
Nephrotoxins: damage to kidney
Endotoxins
Exotoxins
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Indirectly
inducing the hosts defense (immune response)
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Epigenetic changes
environmental changes that changes the way the genes work
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Distribution of pathogen
localized infection, systemic infection
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Localized infection
microbe limited to small area
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Systemic infection
agent spread throughout the body
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Causing Disease warning signals
sign
symptom
syndrome
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Sign
objective evidence of disease as noted by an observer
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Symptom
subjective evidence of disease as sensed by the patient
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Syndrome
a disease identified by a certain complex of signals and symptoms
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Portal of exit
specific venue by which pathogens exit; shed through secretion, excretion, discharge, or sloughed tissue
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Major portals of exit
coughing, sneezing
insect bite
skin cells open lesions
urine
feces
removal of blood
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Stages of infection and disease
incubation period
prodromal stage
acute phase
convalescent period
continuation period
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Incubation period
the period from the initial contact with an infectious agent to the appearance of the first symptoms
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Prodromal stage
a short period incubation; indicates onset of disease
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Acute phase
specific signs and symptoms are seen and pathogen is at peak activity
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Convalescent period
phase which either the organism linger after symptoms subside or the symptoms continue after the organism is no longer detectable
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Reservoir
primary habitat in the natural world from which a pathogen originates
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Transmitter
indiviual or object from which an infection is acquired
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Vertical transmission
transmission if ro parent to offspring via the ovum, sperm, or milk
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Horizontal transmission
disease is spread through a population from one infected indiviual to another; 3 types
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3 types of horizontal transmission
direct transmission
indirect transmission
vector transmission
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Formite
form of indirect transmission from an inanimate object
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Vehicle
form of indirect transmission from natural non-living material like air, water, soil, and food
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HAI
infectious diseases acquired or developed during a hospital or health car facility stay
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Factors tied to HAI
patients
collection points
lowered defenses
acquisition
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Successful identification and treatment relies on
1. asceptic
2. sterile
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Asceptic
free from contamination caused by harmful bacteria, viruses, and other
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Phenotypic methods
observing traits an organism is expressing, examining microbe appearance and behavior, immediate direct examination of the specimen
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Phenotypic examination
enzymatic activities
physical conditions
antibiotics
chemical composition
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Phenotypic method that does not require cultivation
direct examination
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Direct examination
microscopy of patient specimens (after staining)
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Phenotypic method that requires cultivation
selective/differential growth
biochemical testing
susceptibility testing
Phage typing
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Selective/differential growth
identifies characteristics such as colony, appearance, motility, gas requirements
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Biochemical testing
growth detects the prescence of microbes of enzymes, creating metabolic fingerprint
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Susceptibility testing
detects a pattern of antimicrobial susceptibility to identify microbe; useful in determining what drugs will be used for treatment, used during pathogen identification
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Phage typing
testing bacterial sensitivity to phages by determining its lyse
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Phenotypic method drawbacks 1
it has to be cultured
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Phenotypic method drawbacks 2
multiple infections
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Phenotypic method drawbacks 3
non-culture
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Phenotypic method drawbacks 4
easy misidentify: can go undetected
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Phenotypic method drawbacks 5
takes longer
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Dichotomous key
flowchart leading to identification; combines results of gram staining, growth on differential media, and enzymatic testing
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Sensitivity
high, low; the levels you can detect and their variations
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Specificity
the ability to target one specific target and that one only
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Immunological methods
involves in vitro testing serum, urine, cerebrospinal fluid, whole tissues, and saliva for the presence of specific antibodies