Overview

This dissertation, Extended-spectrum Beta-lactamases in Fecal Isolates of Escherichia Coli From Human and Food Animals by Rongshuai, Duan, 段榮帥, 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 of thesis entitled Extended-spectrum beta-lactamases in fecal isolates of Escherichia coli from human and food animals Submitted by Duan Rong Shuai for the Degree of Master of Philosophy at the University of Hong Kong in August 2005 Background: The world-wide dissemination of extended-spectrum -lactamases (ESBLs)-producing Escherichia coli is a serious health concern. It has been suggested that food chain may be involved in the spread of ESBLs. However, such researches on ESBLs in strains of animal origin are still limited and the importance of food chain transmission of antibiotic resistance remains unclear. Objectives: A study was conducted to characterize the carriage of extended-spectrum -lactamases (ESBLs)-producing E. coli in fecal samples of healthy human and food animals in Hong Kong. Methods: 734 fecal samples were obtained from food animals, including cattle, pigs, chicken, ducks, geese and pigeons in slaughterhouses or wholesale markets and 53 fecal samples were obtained from healthy volunteers over a five-month period in 2002. Antibiotic-containing medium was used for selective isolation of potentially ESBL-producing E. coli. Isolates with ESBL phenotypes, together with 6 ESBL positive isolates collected in the same period from another study, were characterized by molecular methods. Results: Of 734 samples of food animals analyzed, six (2%) from pigs, three (3.1%) from cattle and one (3%) from pigeon had E. coli strains with ESBL phenotype, whereas two (3.7%) from healthy volunteers were ESBL positive. The ESBL content for the ten isolates of animal origin include CTX-M-3 (n = 4), CTX-M-13 (n = 3), CTX-M-14 (n = 2) and CTX-M-24 (n = 1). In contrast, only CTX-M-9 (n = 1) and CTX-M-14 (n =7) were identified in the isolates from humans. In five out of the ten isolates from animals, the bla gene was found to be transferred to E. coli (J53 or CTX-M -7 -3 JP995) recipients with frequencies of 10 to 10 per donor cells and the gene was confirmed to be encoded on transferable plasmids by southern blotting (60 or 90 kb). Similarly, five out of the eight isolates from humans were conjugative with -5 -4 frequencies that ranged from 10 to 10 per donor cell. The four CTX-M-3 producing isolates from pigs, the three CTX-M-13 producing isolates from cattle, and two CTX-M-14 producing isolates from human were clonally related, respectively. However, no clonal spread was identified among isolates from different sources. Furthermore, no transmission of plasmids was found between human and animals. Conclusion: This study revealed for the first time bla genes among E. coli in CTX-M animals sold for food in Hong Kong. The findings imply that bacteria of animal origins may serve as reservoirs of some ESBL genes. (Word count = 394) DOI: 10.5353/th_b3530164 Subjects: Beta lactamasesEscherichia coli - Genetics

Full Product Details

9781361102367

Table of Contents

Reviews

Author Information

Tab Content 6

Customer Reviews

Recent Reviews

Countries Available