Overview

This dissertation, Antimicrobial Resistance in Escherichia Coli Isolated From Food Animals and Humans by Chun-wai, Wong, 黃振威, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract Abstract of thesis entitled Antimicrobial resistance in Escherichia coli isolated from food animals and humans Submitted by Wong Chun Wai for the Degree of Master of Philosophy at the University of Hong Kong in August 2007 Background Antibiotics are commonly used in food animals for growth promotion purpose and thus create a selective pressure on food animal isolates. It has caused a great concern to society because this emerging problem can potentially lead to the increased occurrence of antibiotic-resistant bacteria of human significance. The spread of antibiotic resistance genes between food animal and human isolates can be mediated by mobile genetic elements including plasmids, transposons, integrons, and gene cassettes integrated into integrons. However, research gap concerning the potential transfer of mobile genetic elements between food animal and human isolates is still not fully understood and only few studies have suggested the widespread problem of integrons in both populations. Objective The aim of the current study is to determine whether there is a potential transfer of antibiotic resistance genes between bacterial isolates from food animals and humans. Methods A total of 174 ciprofloxacin-resistant E. coli isolates were obtained from food animals and humans. All isolates were tested by PCR analysis for detection of aminoglycoside resistance genes (aacC2 & aacC4), quinolone resistance gene (qnr), sulphonamide resistance genes (sul1 & sul2), and integrase genes of class 1 and 2 integrons (intl1 and intl2, respectively). To characterize the antibiotic resistance gene cassettes of class 1 integron, the variable region was amplified and determined by nucleotide sequencing and restriction fragment length polymorphism. Those isolates with aacC2 or bla resistance genes were randomly selected for subsequent nucleotide TEM sequencing. Conjugal transfer and plasmid incompatibility replicon typing were performed to characterize the aacC2 and CTX-M-14 ESBL-producing resistance plasmids. Results Class 1 integron was found in 63% (109 out of 174) of the isolates and was widely distributed among human and food animal isolates. The cassette array dfrA17-aadA5 was most prevalent (39%) among the animal and human isolates. Among 11 unique cassette arrays, seven were shared by isolates from humans and animals. Replicon typing of plasmids carrying aacC2 genes indicates a diverse background (IncF, IncFIB, IncFIA, IncN, IncI1-Iγ). A 140 kb IncF/FIB plasmid was found to share between human and animal isolates. Plasmids carrying bla were found to CTX-M-14 belong to IncF (n = 14), IncF/FIB (n = 2), IncI1-Iγ (n = 5), IncF/I1-Iγ (n = 1) and other groups. Two CTX-M-14 encoding plasmids with sizes 60 (IncF) and 100 kb (IncI1-Iγ) were shared between animal and human isolates. Both populations also harbored the same allele of aacC2 and bla molecular variants. This study reports TEM-1b on the first detection of two new aacC2 molecular variants that have been designated AAC(3)-IId and AAC(3)-IIe. Isolates carrying aacC2 resistance gene had heterogenous PFGE patterns. Conclusion This study shows that mobile genetic elements play important roles in animal-human dissemination of antimicrobial resistance. The circulation of resistance genes affecting multiple antibiotic classes among huma

Full Product Details

9781374664524

Table of Contents

Reviews

Author Information

Tab Content 6

Customer Reviews

Recent Reviews

Countries Available