Antibiotic Resistance I Flashcards Preview

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Flashcards in Antibiotic Resistance I Deck (11):
1

Plasmid

It is an autonomous, self-replicating, extrachromosomal element composed of circular or linear, double- stranded DNA.

2

Conjugative (conjugal) plasmids

They can autonomously transfer themselves from one host to another; therefore, passing antibiotic resistance to other individuals within the species or to individuals in other species or even to individuals in other genera.

3

Non-conjugative (non-conjugal) plasmids

They cannot transfer themselves. However, they can be transferred by a conjugative plasmid.

4

Lytic (productive) infection

After infection, the viral genome replicates and causes the host cell to lyse, which permits progeny viruses to release into the environment.

5

Lysogenic (latent or temperate) infection

After infection, the virus does not replicate, because all the genes necessary for the lytic infection become turned off (repressed). Thus, the lysogenic phage genome, called a prophage, becomes latent. Prophages can either circularize and remain autonomous like plasmids or integrate into and become part of the host chromosome.

6

Transposable Elements

They are genetic units that mediate their own transfer from one location in a genome to another location within the same genome or from one genome to another in same cell

7

Insertion Sequence (IS) Element

An IS element is a segment of DNA about 1000 bp in length that only carries genes for its own transposition. These genes include a site-specific recombinase (an enzyme that recombines DNA) and two distinct nucleotide recognition sequences located at each terminus in inverted order.

8

What is the structure of an IS?

IR - Recombinase - IR

9

Transposon

It consists of a central core of genes bounded by two IS elements. Because they contain two IS elements, they carry the genes necessary for transposition. The core genes can encode for a variety of functions, including resistance to antimicrobial agents, e.g. antibiotics.

10

Conjugal transposon

In a conjugal transposon, the 2 IS elements flank genes that encode antibiotic resistance and conjugal machinery. Thus, these multiply resistant transposons jump from location to location within a given cell, but because they also carry the genes required for conjugation, they also mediate their own transfer to other cells

11

R Plasmid

An R plasmid is a conjugal plasmid that also carries genes that confer resistance to antibiotics. Often, they carry several resistance genes; thus, a cell that carries such an R plasmid is resistant to multiple antibiotics.

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