Reynolds, LJ; (2017) The identification and characterisation of novel antimicrobial resistance genes from human and animal metagenomes. Doctoral thesis , UCL (University College London).

Preview

Text Liam Reynolds PhD Thesis.pdf.Signaature removed.pdf Download (5MB) | Preview

Abstract

Antimicrobial resistance genes are harboured by bacteria in the human oral cavity and ruminant faeces and they are shed in particularly high abundances in calf faeces. Furthermore, bacteriocin (antimicrobial peptide) producing bacteria have been isolated from these environments. In recent times bacteriocins have received much attention as potential alternatives to antibiotics. Human saliva and calf faeces harbour ‘yet-to-be cultured bacteria’ that can only be studied by analysing their DNA. To this end, two metagenomic libraries were created from human saliva and calf faeces metagenomic DNA with the aim of identifying novel antimicrobial resistance and bacteriocin genes. Screening these libraries for tetracycline resistance identified two tetracycline resistant clones. Clone PS9 was also tigecycline resistant and contained a 7,765 bp insert that encoded two half-ABC transporter genes; subcloning of these genes showed that they were responsible for the observed resistance phenotype. As the ABC transporter conferred resistance only to tetracyclines and its putative amino acid sequence showed <80 % identity to known tetracycline resistance proteins, it was named TetAB(60). Clone TT31 contained a 14,226 bp insert. 7, 216 bp of the insert had 97 % nucleotide identity to Tn916 and contained part of tet(M) and a full length tet(L) gene. This gene organisation has not been described in Tn916-like elements and it may represent a novel Tn916-like element. The human saliva library was also screened for antiseptic resistance revealing a CTAB resistant clone. Random transposon mutagenesis of the 19.1 Kb insert and subcloning of a UDP-glucose 4-epimerase revealed it to be solely required for the observed resistance. This study identified novel tetracycline, tigecycline and CTAB resistance genes from the human saliva metagenome, demonstrating the importance of this environment as a source of resistance genes that may compromise the effectiveness of these antibiotics and antimicrobials. Additionally, this work highlights the relevance of house-keeping genes to the development of antimicrobial resistance.

Download activity - last month

Export as JSONCSVXML

Download activity - last 12 months

Export as CSVXMLJSON

Downloads by country - last 12 months

Export as JSONCSVXML

Archive Staff Only

View Item