Micro Block 2 Flashcards
Define genome
entire complement of genes on all chromosomes found in an organism (hereditary info)
Define gene
What 3 functions is genetic code translated for?
segment of DNA containing the genetic code for a functional product.
structural, catalytic or regulatory functions
How is the genetic code carried?
As a sequence of nucleotide molecules in the nucleic acid macromolecule
Define genotype
total genetic makeup w/ potential properties
Define phenotype
the actual expressed properties of an organism
Define transcription
transfer of genetic code on DNA gene to mRNA by DNA dependent RNA polymerase
Define translation
the synthesis of a new polypeptide at the ribosomes by linking aa in sequence specified by mRNA
Define constitutive genes
Constantly expressed (transcribed and translated into functional units) accounts for 60-80% of genes
Define inducible genes
Genes that can be “turned on”
Define repressible genes
Genes that can be “turned off”
Define operon
Related genes that are regulated as a group/series
Define mutation
Changes (substitution or deletion) in the sequence of DNA bases which changes the genetic code
what are the molecular components of a nucleotide?
5 C sugar (ribose or deoxyribose)
N base- binds to 1’ prime of the 5C
P group- bound to 5’ C
What are the nitrogenous bases?
Purines- Adenine Guanine
Pyrimidine- Thymine Cytosine (Uracil)
A->T(U)
G->C
State the major structural components and characteristics of DNA
2 strands of paired nucleotides attached to deoxyribose
strand- long chain of nucleotides
Strand direction- end on which no P is bound to 3’ C, end with P bound ONLY to 5’ C is the 5’ end
Antiparallel- strands run in opposite directions (3’ nucleotide binds to 5’ nucleotide counter part)
Describe the steps of DNA replication
1- replication fork formation. DNA unwinding by helicase, DNA gyrase and topoisomerase by breaking H bonds between bases/strand.
2- DNA polymerase binds to DNA and inserts complementary nucleotides (always added to exposed 3’ end, strands grow in 5’ to 3’ direction) while also editing for error
3- leading strand has 3’ exposed/leading into replication fork. New strand grows towards replication fork and is continuously replicated.
- Lagging strand (discontinuous) has 5’ end exposed facing replication fork. RNA primer and polymerase are needed to initiate strand growth if nucleotide is missing 3’ binding site. DNA polymerase takes over for RNA primer down to the last/final nucleotide. DNA ligase takes over and inserts missing nucleotide to bind newly formed strand w/ existing strand.
- New double strand re-winds, parental strand unwinds to expose more nucleotides.
Entire process is semiconservative, each helix consists of one newly synthesized nucleotide and one original/parent nucleotide
What are the major components/characteristics of RNA?
Large, single stranded molecule of nucleotides (m,t,rRNA), U replaces T
Function of mRNA
Carries genetic code from DNA to ribosome
Function of RNA codon?
3 nucleotides on mRNA that specify AA to be placed in sequence on polypeptide.
3 nucleotides = 1 codon
1 codon = 1 aa
Function of tRNA?
transports aa to developing peptide chains
Function of Anticodon?
Site on tRNA that binds w/ mRNA codon (carries 3 bases that complement the codons).
Specifies which aa will be carried by tRNA.
Function of rRNA?
facilitator for mRNA and tRNA functions
What is the purpose of transcription?
transfer of genetic code on DNA into mRNA strand by means of DNA dependent RNA polymerase
What are the 4 steps of transcription?
1- DNA helix unwinds
2- RNA polymerase binds w/ DNA @ promoter site
3- Complementary RNA nucleotides joined in sequence by RNA polymerase
4- process ends when RNA polymerase reaches termination region. New single-stranded mRNA releases, DNA rewinds.
What is the purpose of Translation?
synthesis of polypeptide at ribosome through aa linkage specified by mRNA.
What are the 4 steps of translation?
1- mRNA attaches to ribosome start codon
2- tRNA w/ complimentary anticodon matches to mRNA codon, brings first aa into place.
3- aa acids linked together and rRNA releases.
4- polypeptide chain released when reading frame reaches stop codon.
What are the major genes/sites of an operon? How does it function?
Repressor gene- codes for repressor protein that binds to “operator” region
Promoter site- region of chromosomes RNA polymerase binds to during transcription.
Operator site- region that controls RNA polymerase access to operon genes (repressor protein binding site)
Genes of Operon- adjacent genes that direct synthesis of proteins with related functions and are regulated as a unit.
What molecular event permits/prevents the transcription of the structural genes of an operon?
repressor gene- codes for “repressor” protein to bind to “operator” region
promoter site- region of chrom that RNA polymerase binds to during transcription
operator site- region of chrom that controls (permits/blocks) RNA polymerase to structural genes of operon, this is where repressor site does/n’t
Define inducible operon
genes expressed only when favorable environmental conditions exist- unblocks operator site
Define repressible operon
genes expressed except when certain environmental conditions exist- absence of products causes site to be blocked
What are the mutations and what molecular changes occur?
Base- single based replaced, changes codon. Results in improper aa in protein
Frameshift- insertion/deletion of bases shifting codon reading frame of mRNA in ribosome, usually results in missense mutation/different nonfunctional or incomplete protein
What are the 3 types of base substitution mutations?
Silent- no protein change
Missense- different aa in protein, not highly significant
Nonsense- RNA polymerase stopped from reading code, results in incomplete, nonfunctional protein
What are 3 factors that can lead to a mutation?
Spontaneous- once in 10^6 million replications
Chemical- nitrous acid, base analogs (improper pairing), ABX
Radiation- Gamma ray, X-ray, ultra violet
Characteristics of Plasmid
- small circular self-replicating DNA in bacteria
- separate from chrom DNA
- genes not essential for growth
- genes code for ABX resistance
- focus of genetic enginerring
Characteristics of Lysogeny
integration of bacteriophage DNA into bacterial chrom where it replicates w/ bacterial chrom.
viral gene codes for ABX resistance or disease causing factors
produces new bacteriophage upon separation from bacterial DNA
Characteristics of Conjugation
transfer of genetic material between donor and recipient w/ direct cell-to-cell contact
utilizes sex pillus to transfer DNA
Copy of DNA strand/plasmid is transferred to recipient cell
Characteristics of Transformation
direct uptake of DNA from one bacterium to another as “naked” DNA in solution. Usually follows cell breakdown and release of DNA after cell death
Results in new characteristics for the recipient cell
Characteristics of Transduction
transfer of DNA from donor to recipient bacterium using a virus as the vehicle (host DNA/plasmid accidentally enclosed in bacterial virus)
Results in new characteristics for recipient cell, bacteriophage is not functional
Define sterilization
physical procedure/chemical agents to destroy ALL microbial forms including bacterial spores (kills or removes microbes)
Define disinfection
physical procedures/chemical agents to destroy, inhibit, neutralize or remove AT LEAST MOST, but not all, of potentially infectious microbes on a surface
Define antimicrobic
a chemical substance of natural, semisynthetic, or synthetic origin that inhibits or kills microorganisms and which can be used to treat or control infection.
Define selective toxicity
the antibiotic will affect only the target organism (microbe) without harming the host (patient)
Define infectious
microbes capable of causing disease
Define contaminant
microbes present at given time/place and are undesireable
Define nosocomial
Hospital Acquired Infection
Infections that develop during a hospital stay, were not present at time of admission
Define the BSLs
1- no known infection causing potential
2- most commonly encountered in clinical samples, not highly transmissible
Includes HIV
3- unusual/highly transmissible (TB, Brucella) especially respiratory route
4-Highly infectious/exotic microbes/toxins that have no vaccine/effective treatment
Define antisepsis
Use of chemical agents on skin/living tissue.
Eliminates/inhibits microbes (no sporicidal action implied).
Application of a mild disinfectant
Rank the types of microbes according to their resistance to killing by sterilization/disinfection methods
Bacterial endospores Mycobacterium Protozoan cysts Non-enveloped small viruses Vegetative bacteria Fungi Enveloped viruses
How does microbial death rate and effectiveness affect the choice method/procedure of sterilization/disinfection?
Death isn’t instant, microbes become dysfunctional and die over a period of time.
Vegetative cells die more rapidly than spores.
How does microbial population composition (especially spores) affect the choice/effectiveness of sterilization/disinfection method?
Larger colony req’s longer exposure time
How does concentration of antimicrobial and duration of exposure affect the effectiveness of sterilization/disinfection method?
More concentrated the chemical or intense and agent is, more rapid the microbe destruction.
70% ethanol is more effective than 95% ethanol
How does the presence of protective/neutralizing matter affect the choice and effectiveness of sterilization/disinfection method?
Organic matter protects/inactivates chemical disinfectants
Organic matter protects microbes from heating/chemical disinfectants
Describe the general modes of action of microbial control methods
Damage to cell wall- blocks synth/breaks down (ABX, lysozyme, detergents)
Disrupts cytoplasmic mem- loss of membrane integrity/permeability (surfactants, heat).
Inhibits protein synth/nucleic acids- interferes w/ gene translation preventing protein synth (ABX, radiation, formaldehyde)
Alters function of protein/nucleic acid- alters bonds of secondary/tertiary structures. Inactivates/denatures enzymes/nucleic acids
Describe the methods of physical control
Cold temps-
1: refrigeration: slows metabolic processes, doesn’t kill
2- freezer: -70*C stops metabolic actions but doesn’t kill
Heat- kills by disrupting membrane functions, denatures proteins, inactivates nucleic acid. H bonds in protein broken.
Dependent on temp, duration and humidity.
Moist heat- more effective than dry heat.
Characteristics of dry heat, steam heat and incineration
Dry- 160-180C x 2 hrs
Liquids can’t be processed, organic compounds may denature +160C
Used for thermostable non-liquid items
Steam- 121C x 15min
High pressure of autoclave counteracts vaporization so liquids can be heated to 121C @ 15lbs of pressure- DOESN”T KILL
Incineration @ 1800*F reduces waste to ash, can process 1000kg/hr
List characteristics of radiation disinfection
Ionizing- (Gamma) alters proteins/nucleic acids. Used for pharmaceuticals, medical/dental supplies and non-heat resistant items
Non-ionizing: Electron Beam
Alters nucleic acid, decons packages (postal service)
Ionizing radiation- electron beam
alters nucleic acid
decon packages (postal service)
Non-ionizing radiation- UV
Causes nucleic acid mutations
Optimum wave length- 240-280 nm (254 optimum)
Low penetration power, reqs contact and lengthy exposure time (10sec-30min)
Describe the characteristics of filtration disinfection
Membrane Microscope filters- cellulose acetate and cellulose nitrate membrane w/ pores to trap microbes (.22 micron, used for sterilization of thermolabile liquids)
HEPA filtration- glass and polymer fibers that remove 99.97% of particles 0.3um and larger.
Included N95 and PAPR filters
Methods of chemical control of microbes
High-Level Disinfectants- microbicidal and sporocidal, some may be sterilants.
Intermediate-Level Disinfectants- most common, effective agains vegetative baceria and MAY be effective against fungi/virus, few are sporicidal, few are antiseptics.
Low-Level Disinfectant- usually bactericidal, not sporicidal or tuberculocidal, often not fungicidal or virucidal.
Soap- moderately effective disinfectant by mechanical removal of microbes w/ 15sec wash
Mechanism of action of antimicrobics
ABX/antimicrobic- Inhibits/kills microbes and can be used to treat/control infections
Selective toxicity- ABX only effects target microbe w/out harming host (side effects expected and accepted).
Inhibit cell Wall Synth- Inhibit protein synth- Inhibit cell membrane function- Inhibit nucleic acid synth- Inhibit bacterial metabolism-
List the types of cell wall inhibitor antimicrobics, state the MOA and use/limitations of each
1-Beta-lactam ABX- Beta-lactam ring (O=C-N) by altering side chains causes difference in antimicrobic properties (Penicillins- ampicillin, methicillin, carbecillin, piperacillin; Cephalosporins- cephalothin, cefotoxin, ceftazadime)
Inhibit peptidoglycan synthesis by inhibiting crosslink formation between polymers
Beta-lactam antibiotics bind to Penicillin Binding Proteins (enzymes that synth peptidoglycan)
2- Vancomycin- bind to cross-link peptide, peptidoglycan polymer can’t elongate
3- Bacitracin- blocks phospholipid carrier that carries subunits of peptidoglycan across membrane to cell wall
4- Isoniazid- inhibits formation of mycolic acid in cell wall of mycobacterium (TB)
Explain the mechanism of action of beta-lactam antimicrobics
Beta-lactam ring (O=C-N) by altering side chains causes difference in antimicrobic properties (Penicillins- ampicillin, methicillin, carbecillin, piperacillin; Cephalosporins- cephalothin, cefotoxin, ceftazadime)
*Gram neg effectiveness
State the MOAs of inhibitors of protein synthesis
Chloramphenicol- binds to 50S portion, inhibits peptide bond formation
Tetracycline- interferes w/ tRNA->mRNA binding
Aminoglycosides- Bind to 30S causing inaccurate reading of mRNA
Erythromycin- Binds to 50S preventing translocation (ribosomal movement along mRNA)
What is the general MOA of inhibitors of nucleic acid synthesis and name 4 examples
competetive inhibition of essential nucleic acid precursor or binds essential enzyme (DNA gyrase)
How does rifampin inhibit NA synth?
inhibs transcription by binding to RNA polymerase, inhibits initiation of mRNA synthesis
How does quiolones inhibit NA synth?
inihibs DNA gyrase (prevents DNA coiling so it can’t/won’t fit into bacterial cell)
Q= nalidixic acid
Flouroquinoles-
How does nucleoside analogues inhibit NA synth?
antiviral antimicrobics that inhibit DNA or RNA synthesis by using nucleic acid analogues to alter composition and inactivate DNA/RNA (Acyclovir, Ribavirin, Zidovudine)
Name the antibicrobics which inhibit bacterial metabolism and explain MOA
Sulfonamides- inhibits folic acid synthesis by competing for precursor molecules
Trimethoprim- competitively interferes w/ folic acid production by inhibiting metabolic enzyme
Azoles- (fluconazole): antifungal, inhibits synthesis of ergosterol which is a key structural molecule of fungal cell membranes
Name the antimicrobes which inhibit membrane function and explain the MOA
detergent like; disrupts integrity of cytoplasmic membrane, allows nucleotides and proteins to escape
Polymyxims- + against Gram-Negs, limited by nephrotoxicity= EXTERNAL USE
Amphotericin B- (polyene): antifungal that binds w/ ergosterol in fungal membrane, is somewhat toxic
Name the point of action for various antiviral meds
Viral absorption- blocked by IgG
Uncoating- blocked by amantadine (Influenza A)
Early protein synth- blocked by fomivirsen (CMV)
Nucleic acid synth- purine, pyrimadine analogs; reverse transcriptase inhibitors
Late protein synth- blocked by methimiazole (variola, protease inhibitors)
Packaging and assembly- blocked by rifampin (vacciniaa)
Viral release- blocked by neuraminidase inhibitors
What is the table of antimicrobes including site, MOA and significant limitations
j
What is the MOA of Flucytosine, 5-flurocytosine?
incorporates itself into fungal RNA and interferes w/ DNA and protein synthesis
What general types of laboratory procedures are typically performed to recover and identify bacteria from a clinical specimen?
Isolation: dilutes specimen for isolation/identification
Pure Culture: single bacteria w/ maintained isolation (req’d for biochemical testing)
Streaking: 4 quadrants
Subculture: technique for purity (picking a colony)
What general types of laboratory procedures are typically performed to recover and identify fungi from a clinical specimen?
Yeasts-
Cultivation: blood agar plate/other special media similar to bacteria, 2-7 days
Identification: microscopy, biochemical tests, antigen tests
Molds=
Cultivation: media w/ ABX (sabouraud w/ abx). Mycelium visible w/in 1-4wks
Identification: direct microscopic exam of specimen/culture/ few biochemical tests, few antigen tests
What general types of laboratory procedures are typically performed to recover and identify viruses from a clinical specimen?
Cultivation: grow in living tissues/cells, 2-21 days
Identification: antibody detection, antigen detection, gene probes
List the most commonly used primary bacterial culture media, and state the nutritional or diagnostic type
Nutrient: general nutrition for most common bacteria
Enriched- general nutrients plus enrichments for common/fastidious bacteria
Selective- contains ingredients to restrict microbe growth (abx, inhibitory chemicals)
Differential-: ingredients that offer visual proof of chemical reactions (pH changes, H2S production, metabolism of specific chemicals)
List characteristics and use of Blood Agar Plate?
- sheeps blood
- moderately enriched to differentiate hemolytic pattern
- grows almost all bactera (except N. Gonorrhoeae, H. influenzae and others that req SCA
- gives observation of blood cell hemolysis (alpha, beta, gamma
- can be made selective w/ abx addition
List characteristics and use of Supplemented Chocolate Agar
- highly enriched to grow most medically significant bacteria but lacks visual display of colony characteristics
- can be made selective media w/ abx additions (TM medium- inhibs most bacteria but allows growth of Neisseria species growth)
List characteristics and use of MacConkey Agar
Selective and differential for Gram-neg bacilli
Contains inhibitors for Gram-Pos cocci/baccili and gram neg cocci
Differentiates based off of utilization of ingredients and pH changes
XLD, HEK, Salmonella-Shigella, EMB
List characteristics and use of broth media (liquid)
Used for blood culture
may/not be selective
What are the characteristics that are observed/interpreted about bacterial colonies on agar plates?
takes 18-24hrs
>1mm-+4mm and smooth, rough or wrinkled
natural pigment or due to pH indicator
hemolysis (blood agar only)- Alpha: green zone, Beta: clear zone, Gamma: no change in RBCs around colony
What lab tests are used for identifying bacteria at the genus and species level?
Gram stain
culture characteristics
biochemical tests
Time: 6-48hrs, TB can take 2wks or more
What lab tests are required to identify viruses and what are the time periods?
cultivation- living tissue, 2-21 days
identification- antibody detection, antigen detection, gene probes
What lab tests are required to identify a fungus at the genus/species level? What are the time periods?
Yeasts:
Cultivation- growth on blood agar, 2-7 days
Identification- microscopy, biochemical tests, antigen tests
Molds:
Cultivation- media w/ ABX (Sabouraud w/ ABX) Mycelial masses visible in 1-4wks
Identification- microscopy, few biochemical test, few antigen
What is the basic principle of an immunodiagnostic test?
a
What is the difference between immunodiagnostics test results w/ non-reactive, good binding and cross reactive. Which is better and why?
b
Define/explain Sensitiviy of immunodiagnosis tests
ability to detect very low Ag levels
Kits designed to ensure true-positives, low false-positives are included
Expressed as Limit of Detection and 2 Percent Accuracy
High sensitivity used as initial screening and presumptive tests
Define/explain the Specificity of immunodiagnostic tests
ability to detect correct Ag or Ab while not reacting with incorrect Ag or Ab
Distinguish cross-reactive and false-positive results from true positives
What are the general procedures of immunoassay tests, summarize key steps
a
What are the various ways immunodiagnostic test results are made detectible/visible?
b
What are the characteristics of immunodiagnsotic tests like agglutination and ELISA?
c
What are the basic steps and principle of gene amplification? Draw and label
1-Heat applied to DNA sample and denatures proteins
2-Primers anneal to desired site on single DNA strand
3-DNA polymerase enzymes from Thermus aquaticus causes DNA to be synthesized
4-Results in 2 new copies of DNA
5-Process repeated (thermal cycling) until desired number of strands is reached
Define amplified/amplification
increased number of copies of significant microbial gene sequences for detection (polymerase chain reaction- PCR)
What are the major components of the bright-field light microscope?
Base Arm Substage Stage Body Lighting System
What are the typical objective lenses?
What is the total magnification of objects viewed through each lens?
Low- 10x
High/dry- 40-45x
Oil- 90-100x
Eye piece- 10x
Low= 100x High= 450x Oil= 1000x
Describe the match up of lens w/ lighting w/ type of microbe being observed
Gram stain- oil
KOH prep molds- low
wet mount preps- low or high, no oil
What is the purpose and principle of the Gram stain?
Enables viewing of microbes by microscopy (unstained= invisible) and enables differentiation based on morphologic and staining differences
What is the sequential steps of the Gram stain?
Smear prep- smear specimen, air dry w/out heat, flood w/ methanol x 1min
Stain:
Primary stain (crystal violet) x 1 min, rinse w/ tap
Mordant (Grams idoine) x 1 min, rinse w/ tap
Decolorizer (acetone and alcohol) x 2-5sec, rinse w/ tap
Counterstain (Safranin) x 30-60sec, rinse w/ tap and dry
Examine- start w/ low power, change to oil
Interpretation- reported in 30-60min
positive- blue-violet
negative- pink-red
Report stain reaction, cell shape and arrangement
What is the principle and general procedure for wet mount microscopic examinations?
direct examination of an unfixed specimen (observation in natural state)
place specimen on slide and cover
observe w/ low/high dry power and reduced light
KOH- 10% KOH dissolves epithelial cells allowing fungal cells to become clearer (performed w/in 10min of collection)
Yeast cells w/ capsules in CSF need India ink for visualization
Saline wet prep of vaginal exudate will show yeast cells and motile Trichomonas organisms
What is the overall purpose of anitmicrobic agents?
a
Define susceptible?
Define resistant?
Define intermediate?
Susceptible- microbe is inhibited/killed by max safe dose/concentration of a antimicrobic (candidate for using in treatment)
Resistant- microbe is not inhibited (can tolerate) by the max safe dosage, this drug should not be used for treatment
Intermediate- (susceptible dose dependent), microbe may be inhibited by high dosage very near the resistant point. Usually interpreted as resistant, antibiotic may be used under careful situations/controlled conditions.
Describe the principle of the disc diffusion AST?
How are they reported?
How are the susceptible/resistant results determined?
Determine which antimicrobes are effective against a particular bacterium at the “breakpoint” concentration of each ABX
reported?
Measurement of size of inhibition zone of growth converts size in “mm” to susceptible, intermediate or resistant
Describe the principle of the MIC AST?
How are the results reported?
What is the criteria for differentiating between a result of susceptible/resistant?
determines the minimum concentration of each antimicrobic agent that is effective against a bacterial pathogen.
results?
Susceptible- ABX concentration of 2 x MIC
Resistant- ABX concentration of 2x can not be achieved even WITH max safe dosage.
Define symbiosis
close association and interaction of two dissimilar organisms
Define normal flora
microbes that are normally/consistently found in the body
Define commensalism
association between organisms where one benefits and the other neither benefits or is harmed
Define mutualism
both microbe and host derive benefits
Define Opportunism
disease trait of the resident flora only when normal homeostasis is altered
Define parasitism
microbe lives in/on host at expense of host
Define vector
2 examples?
carrier of microbe from host to host
Insects/animals
Inanimate objects
Define infectious diseases
growth and spread of a pathogen in a host resulting in host injury
What are the two traits of a infectious disease
Pathogen- microbe capable of causing disease by invading tissue/producing toxins
Virulence- degree of pathgenecity
How is virulence broken down/measured?
Infectivity- how easily microbe survive normal host defenses
Severity- damage it causes to the infected host
What are the types of Host-Microbe relationships
Symbiosis Normal flora Commensalism Mutualism Opportunism Parasitism Vector Infectious disease
4 times/examples of altered host-microbe relationship that would alter Opportunism
Prolonged ABX
Injury/surgery
Immunological compromise
Hormonal/chemical changes
Define fomite
inanimate articles that could potentially act as vectors
What are the 4 modes of transmission?
Direct contact
Inhalation- particles
Ingestion
Parenteral- arthropod/animal vector, needles
What are some of the microbial virulence factors?
Attachment/Establishment factors Antiphagocytic factors Invasive enzymes Exotoxins Endotoxins Genetic Alterations Special antimicrobial resistance
Define portal of entry
enables establishment of infection
Organism must enter correct portion of body, overcome local defenses, find right/best environment for growth
Define Attachment methods
this is REQUIRED to establish infection
Fimbrae- attachment to specific receptor/tissue
Surface chemicals- dissolve cell coverings and aid chemical attachment
Adhesive Matrix- production of biofilms: provides bacterial protection from environment
What are the factors that influence Attachment and Establishment
POE
Attachment
Quantity
Quorom-sensing regulators
Define Qurom-sensing Regulators
chemicals that
1- restrain disease causing action until sufficient quantity of microbe is present
2- “activate” disease causing process at once
4 examples of Antiphagocytic factors
Capsule- slipper/slimy anti-phagocytic defense
Leukocidin- (staph, strep, bacilli) cause WBC destruction
Coagulase- (staph aureus) causes fibrin clot formation around microbe
Survival- (mycobacteria, gonococcus, listeria) resistance to destruction w/in phagocytosis process
List the 8 Invasive enzymes
1-Collagenase- breaks down collagen
2-Lecithinase- destroys RBC membranes
3-Hyaluronidase (staph, strep, clostridium) breaks down H. acid in membranes
4-Fibrinolysin/Streptokinase- lyses fibrin in clots preventing microbe isolation
5-Hemolysis- (staph,strep,perfringens) dissolves RBC membranes
6- Lipase- digests lipids allowing microbe entrance
7- Proteases- digests proteins (IgA, protective chemicals) allowing mass entrance
8- Super Ags- exacerbated immune/inflammatory responses
Describe characteristics of Exotoxins and list examples
Proteins excreted from cell
Specific/widespread effect on body
Highly potent
Elicit effective Abs
Tetanus neurotoxin- involuntary contractions
Staph. enterotoxin- diarrhea, vomiting
Cholera- diarrhea
Diphtheria- interferes w/ protein synth in bronchi/heart, increases mucus production/fibrous blockage in resp tract
Strep. erythrogenic toxin
Describe Endotoxin including biological effects and mechanism
Lipid A- LPS of Gram-neg cell walls, released upon cell disintegration
Binds to CD14 and TLR4 on macrophages/B cells
Stim synth and release of IL-1, TNF, IL-6 causing fever, pain, hypotension
Not very potent, high quantity in blood req’d
Poor protection/Abs
Gram-neg bacillus
How does gain of genetic material by microbes affect virulence? Give examples
Plasmid- Extrachrom. DNA: exotoxin, ABX resistance, invasive enzymes. Transmitted->daughter cells, can be passed during conjugation
Lysogeny- viral DNA incorporated into bacteria DNA
Codes for exotoxins and invasive enzymes. Transmitted->daughter cells
Recombination- genetic material incorporates from organism->organism. Different Ags produced, increased ABX resistance
How do bacteria gain ABX resistance?
Mutated genes- 1 in 10bill
Plasmid encoded genes
Lysogenic virus
Presence of a ABX resistant bacterium in community/hospital leads to ?
Survival of mutant
Increased # of mutant population
Problems increase and spread to new geographical locations
How do bacteria gain beta-lactamase resistance?
Plasmid encoded gene that produces enzyme that inactivates beta lactam antimicrobics
Usually carried by Enterobacteriaceae, Staph, N. Gonorrhoeae, Haemophilus influenza
Characteristics of MRSA
Methicillin-Resistant Staph. Aureus
Mutated (chromosome) mecA gene- encodes low affinity penicillin binding protein (PBP2a)
Resistant to all beta-lactam ABX (regardless of in vitro lab results)
Characteristics of Carbapenem-Resistant Enterobacteriaceae (CRE)
Mutated gene for membrane porins and PBP trans-peptides
Carried by plasmids
Results in loss of drug diffusion into periplasm
Loss of cross-linking activity of PBP
What are the Non-Specific Host Resistance factors?
Physical/mechanical/chemical barriers
Phagocytosis
Inflammation
Examples of physical/mechanical/chemical barriers of Non-Specific Resistance
Skin Mucous membranes Cilia- resp tract Peristalsis Normal flora
Acid pH Bile salts Lysozymes- tears, saliva Normal flora antimicrobials Interferon
What are the 3 steps in the inflammation response?
Develops after mechanical injury or exposure
1- Inc capillary permeability/phagocytic leukocytes
2- Neutrophils/macrophages conduct phagocytosis
3- Fibrin clot forms over site
What are the types of specific Host Resistance factors?
Cell Mediated Immunity- Ag causes release of lymphokines which enhance phagocytosis
Abs/Complement- opsonization
