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EOS Principles of diseases > bacterial genetics > Flashcards

bacterial genetics Flashcards

1
Q

what are mutation?

A
  • mutations are permanent alterations in DNA

- account for evolutionary changes in microbes & for alterations that produce different strains in species

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2
Q

Spontaneous mutations vs induced mutations

A

spontaneous mutations

  • arise during the replication of DNA
  • due to error in the base pairing of nucleotides in the old & new strands of DNA

induced mutations
- produced by mutagens which increase mutation rate

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3
Q

point mutations vs frame shift mutations

A

point mutations
- effect a single based

frameshift mutations

  • nucleotide is either deleted or inserted into the DNA
  • can affect more than one base
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4
Q

what does recombination involve?

A
  • combining genes from 2 different cells to greatly increase the genetic diversity of organisms
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5
Q

what are the 4 mechanisms of recombination?

A
  • transformation
  • transduction
  • conjunction
  • insertion sequences & transposable elements
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6
Q

describe the transformation mechanism of recombination

A
  • transformation is the ability of a bacteria to bind & translocate DNA fragments or plasmids & incorporate them into their chromosome
  • does not occur very often naturally
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7
Q

describe the transduction mechanism of recombination

A

transduction involves gene transfer from a donor to a recipient via a bacteriophage (a virus that infects bacteria)

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8
Q

what are the 2 types of bacteriophages

A
  1. lytic phage - when virus particles replicate within cell, it results in lysis
  2. lysogenic phage - viral genome is inserted into chromosome & replicates along with the host
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9
Q

what is a prophage?

A
  • is phage DNA in the quiescent/dormant state
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10
Q

describe the conjunction mechanism of recombination

A
  • conjunction involves gene transfer from a donor to a recipient by direct physical contact between cells
  • done cell has a F factor (sex pilus)
  • recipient cell lacks an F factor
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11
Q

what are plasmids?

A
  • plasmids are small extrachromosomal circular pieces of DNA that replicate independently of the chromosome
  • not essential for growth but carry useful genes for virulence factors, resistance, replication or conjunction
  • plasmid transfer occurs within & between species
  • plasmids can integrate occasionally with chromosomal DNA
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12
Q

describe conjugative plasmids (F-plasmids & R-plasmids)

A
  • F-plasmids have the capacity for horizontal gene transfer by containing a sex pilus to transfer genetic material to another bacteria
  • R-plasmids - refresh to plasmids encoding antimicrobial resistance
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13
Q

what are transposable genetic elements in regards to as a mechanism for recombination

A
  • transposable genetic elements are segments of DNA that have the capacity to move from one location to another (jumping genes)
  • includes: insertion sequences, transposons, integrative conjugative elements and genetic cassettes
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14
Q

what are insertion sequences?

A
  • sequences that carry no known genes except those that are required for transposition (transfer of a segment of DNA from one site to another in genome)
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15
Q

what are transposons?

A
  • special DNA segments that can move from one location in the genome to another
  • cause rearrangement of the genome
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16
Q

what are integrative conjugative elements (ICE)?

A
  • are self transmissible mobile genetic elements
  • transfer via conjugation
  • integrate & replicate within host chromosome
  • contain accessory genes for gene cassettes with antimicrobial resistance & virulence factors
17
Q

what are integrons?

A
  • integrons are DNA elements which capture & expression circular DNA elements (gene cassettes)
  • widely distributed in environment
18
Q

what is antimicrobial resistance?

A
  • is the relative or complete lack of effect of an antimicrobial agent against a previously susceptible microbe
  • an increase in MIC occurs (minimum inhibitory concentration)
19
Q

how can antimicrobial resistance develop?

A
  • a new mutation in a gene that determines sensitivity or resistance
  • gene transfer
20
Q

cross resistance vs multiple resistance?

A

cross resistance

  • is when a microbe uses a single mechanism for resistance
  • so closely related antibiotics are rendered ineffective

multiple resistance

  • is when a microbe uses multiple mechanisms for resistance
  • unrelated antibiotics are rendered ineffective
  • when microbes acquire multiple plasmids
21
Q

how can antibiotics create selection pressures that favour antimicrobial resistance?

A
  • antibiotics do not induce mutations but they can create environments that favour survival of mutant resistant microbes
  • kill of bacteria that are not resistance
  • resistant bacteria that survive multiply & become dominant
22
Q

what are the different mechanisms bacteria can use to be resistant to certain antibiotics?

A
  1. using an alternative metabolic pathway
  2. producing an enzyme that destroys the antibiotic
  3. altering permeability to later influx or efflux of antibiotic
  4. modifying the antibiotic target site on bacteria
23
Q

what are the 3 types of resistance? and how do they occur?

A
  1. natural or intrinsic resistance
    - occurs naturally to all members of a specific bacterial taxonomic group
    - due to structural or biochemical characteristic that naturally occurs in the wild-type of microbe species
  2. mutation resistance
    - occurs by a spontaneous chromosomal mutation
  3. extra-chromosomal or acquired resistance
    - occurs by transformation, transduction & conjunction
24
Q

what is co-selection?

A
  • occurs when a single antimicrobial provides selection pressures for the persistence & transfer of multi-drug resistance in bacteria that have a single plasmid with multiple antibiotic resistant genes
25
Q

what is the mutant preventing concentration (MPC)?

A
  • is the minimum concentration of antibiotic required to prevent the expansion of first step spontaneously generated antibiotic resistant mutants in a large population of bacteria
  • is used for determining the optimal dosing regime to minima the formation of resistant mutants
26
Q

what factors promote antimicrobial resistance?

A
  • exposure to sub-optimum levels of antimicrobial agent
  • exposure to microbes carrying resistant genes
  • inappropriate use of antimicrobials
27
Q

what are 4 strategies for the control of antimicrobial resistance?

A
  1. Prescribing guidelines - AVA code of practice
  2. better infection control (eg biosecurity measures)
  3. better vaccines
  4. alternatives to antibiotics (probiotics)

EOS Principles of diseases (12 decks)

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