Related Experiment Video
Updated: Mar 2, 2026
Replication of the Ordered, Nonredundant Library of Pseudomonas aeruginosa strain PA14 Transposon Insertion Mutants
Published on: May 4, 2018
p518, a small floR plasmid from a South American isolate of Actinobacillus pleuropneumoniae
Giarlã Cunha da Silva1, Ciro César Rossi1, Mateus Ferreira Santana1
1Laboratório de Genética Molecular de Bactérias, Departamento de Microbiologia, Instituto de Biotecnologia Aplicada à Agropecuária (BIOAGRO), Universidade Federal de Viçosa, Viçosa, Brazil.
Abstract:
A small (3.9kb) plasmid (p518), conferring resistance to florfenicol (MIC >8microg/mL) and chloramphenicol (MIC >8microg/mL) was isolated from an Actinobacillus pleuropneumoniae clinical isolate from Southeastern Brazil. To date, this is the smallest florfenicol resistance plasmid isolated from a member of the Pasteurellaceae. The complete nucleotide of this plasmid revealed a unique gene arrangement compared to previously reported florfenicol resistance plasmids found in other members of the Pasteurellaceae. In addition to the floR gene and a lysR gene, common to various florfenicol resistance plasmids, p518 also encodes strA and a partial strB sequence. An origin of replication (oriV) similar to that in the broad host range plasmid, pLS88, was identified in p518, and transformation into Escherichia coli MFDpir confirmed the ability to replicate in other species. Mobilisation genes appear to have been lost, with only a partial mobC sequence remaining, and attempts to transfer p518 from a conjugal donor strain (E. coli MFDpir) were not successful, suggesting this plasmid is not mobilisable. Similarly, attempts to transfer p518 into a competent A. pleuropneumoniae strain, MIDG2331, by natural transformation were also not successful. These results suggest that p518 may be only transferred by vertical descent.
Insights
A novel, small plasmid (p518) conferring florfenicol and chloramphenicol resistance was identified in Actinobacillus pleuropneumoniae. This plasmid appears to be exclusively transferred vertically, not through horizontal gene transfer.
Area of Science:
- Veterinary Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Actinobacillus pleuropneumoniae is a significant pathogen in swine, often treated with florfenicol and chloramphenicol.
- Plasmids play a crucial role in the dissemination of antimicrobial resistance genes.
- Understanding plasmid biology is key to combating antimicrobial resistance.
Purpose of the Study:
- To characterize a novel plasmid conferring florfenicol and chloramphenicol resistance.
- To investigate the genetic makeup and transferability of this small plasmid.
- To determine the mechanism of spread for this resistance determinant.
Main Methods:
- Isolation and sequencing of the plasmid (p518) from Actinobacillus pleuropneumoniae.
- Comparative genomic analysis with known florfenicol resistance plasmids.
- Functional assays including transformation into Escherichia coli and conjugation experiments.
- Natural transformation attempts into Actinobacillus pleuropneumoniae.
Main Results:
- Isolation of a 3.9kb plasmid, p518, conferring resistance to florfenicol and chloramphenicol.
- p518 possesses a unique gene arrangement including floR, lysR, strA, and partial strB.
- The plasmid contains an origin of replication enabling replication in E. coli but lacks functional mobilization genes, rendering it non-mobilizable.
- Attempts at conjugal and natural transformation were unsuccessful, indicating limited horizontal transfer.
Conclusions:
- p518 represents the smallest known florfenicol resistance plasmid in Pasteurellaceae.
- Its unique genetic structure and lack of mobilization genes suggest limited horizontal spread.
- Vertical transmission is the likely mechanism for the propagation of p518 within bacterial populations.
Related Concept Videos
01:28Plasmids
01:30Bacterial Phylum Actinobacteria