Detection of extended-spectrum [beta]-lactamase-producing Escherichia coli in human faecal flora in Hong Kong

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Detection of extended-spectrum [beta]-lactamase-producing Escherichia coli in human faecal flora in Hong Kong


Author: Tsang, Ka-lok Grand
Title: Detection of extended-spectrum [beta]-lactamase-producing Escherichia coli in human faecal flora in Hong Kong
Degree: M.Sc.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations
Beta lactamases
Escherichia coli
Department: School of Nursing
Pages: xiv, 135 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record:
Abstract: Objectives This study was conducted to detect the presence of extended-spectrum 帣-lactamase (ESBL)-producing Escherichia coli in the faecal flora of four population groups: general out-patients, hospitalized patients, convalescent patients, and healthy inmates in Hong Kong and to characterize the blaTEM, blaSHV, blaOXA-1, and blaCTX-M genes present in these isolates. Methods One thousand two hundred and eighty-six faeces samples were collected from 1,286 patients and screened at the Enteric Laboratory of Public Health Laboratory Centre between January and July 2004. Three hundred and fourteen non-duplicate E. coli isolates resistant to the third-generation cephalosporins (cefotaxime) were recovered. These isolates were selected for further study on the basis of production of ESBL detected by three different phenotypic test methods. Antibiotic susceptibility testing was also perfornwd to a range of antibiotics using the Vitek 2 instrument in conjunction with the AST-N017 susceptibility test card. The TEM, SHV, OXA-1, and CTX-M genes were detected by PCR assay. Results The faccal carriage rates of ESBL-producing E. coli in general out-patients, hospitalized patients, convalescent patients, and healthy inmates were 19.0%, 19.3%, 33.3%, and 22.5%, respectively. Two hundred and eighty-two of the 314 E. coli isolates recovered were confirmed to be ESBL-producers. The Oxoid CD03 (cefotaxime/clavulanate) combination discs showed the highest performance for the detection of ESBL-producing E. coli. Etest ESBL strips showed good concordant results with the combination discs method whereas the Vitek 2 AST-N017 had the lowest sensitivity in detecting ESBL among the three phenotypic test methods. One false-positive ESBL result was also obtained from the Vitek 2 AES. A total of 280 isolates carried the CTX-M genes, of these, 190 isolates were also positive for one or two of the other three 帣-lactamase genes studied. Moreover, the frequencies of co-resistance to other class of antibiotics were common throughout ESBL-producing E. coli isolates recovered from faecal samples: nalidixic acid, 86.2%; trimethoprim/sulphamethoxazole, 56.0%; ciprofloxacin, 48.6%; tobramycin, 42.9%; gentamicin, 41.5%; nitrofurantoin, 1.1%; and amikacin, 0.7%. Conclusion The overall prevalence of ESBL in isolates of Escherichia coli in Hong Kong was 20.4%. Faecal carriage of ESBL-producing E. coli was found in all four population groups, with the CTX-M type most common. The overuse of extended-spectrum cephalosporins in human as well as livestock could well be the cause of spread of this resistance. Because of the public health implications, including for the treatment of community-acquired urinary tract infections caused by ESBL-producing E. coli, the spread of these CTX-M-producing strains merits further study and close monitoring in the future.

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