Detection of extended-spectrum beta-lactamase producers among enterobacteriaceae species in clinical isolates from a district hospital in Hong Kong

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Detection of extended-spectrum beta-lactamase producers among enterobacteriaceae species in clinical isolates from a district hospital in Hong Kong

 

Author: Chan, Wai-sze
Title: Detection of extended-spectrum beta-lactamase producers among enterobacteriaceae species in clinical isolates from a district hospital in Hong Kong
Degree: M.Sc.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
Beta lactamases.
Enterobacteriaceae.
Department: Dept. of Health Technology and Informatics
Pages: xvi, 81 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2198989
URI: http://theses.lib.polyu.edu.hk/handle/200/194
Abstract: Objectives This study was conducted to evaluate the effectiveness of four types of combined discs in detection of extended-spectrum p-lactamase (ESBL)-producing Enterobacteriaceae in clinical isolates, to choose the most suitable one to use in the routine clinical laboratory, to characterize the distribution of bla^M, W^SHV, blaoxA-\ and blacrx-M in different sites of infection among different species by PCR and to determine the carriage rate of ESBL-producing strains in in-patients and healthy subjects by stool culture. Methods One hundred and fifty-nine non-duplicate clinical isolates of Enterobacteriaceae , consisting of Escherichia coli (78 isolates) , Klebsiella species (21 isolates), Proteus species (21 isolates) , Enierobacter species (6 isolates), Citrobacter species (2 isolates), Providencia species (7 isolates) , Morganalla morganii ( 9 isolates) and Serrutia species ( 8 isolates) and two non-fermentative species, Acinetobacter species (3 isolates) and Pseudomonas species (4 isolates) which displayed resistance or intermediate resistance to either of two cephalosporins, cefuroxime or cefotaxime, were examined for their ESBL-producing ability. These isolates were collected over a six-month period, from February to July of 2006, in the Medical Microbiology Laboratory of Kwong Wah Hospital. Production of ESBL was detected by four types of combined discs cefpodoxime(Cpd)/CA (CD01), ceftazidime(Caz)/CA (CD02), cefotaxime(Ctx)/CA (CD03) and cefpirome(Cep)/CA (CD04). The TEM, SHV, OXA, and CTX-M genes were detected by two sets of PCR assay. Results The overall detection rate of ESBL among the collected strains was 64% (104/159) by combined disc methods and 79.2% (126/159) by PCR. The Oxoid CD03 (cefotaxime/clavulanate) combined disc was most sensitive for the detection of ESBL-producing Enterobacteriaceae species among four types of combined disc. Most strains in this study carried TEM (65.9%) or CTX-M (61.1%) genes. Of these, 38.3% carried both TEM and CTX-M. Overall ESBL carriage rates shown by stool culture were 24.8% and the percentage of in-patients isolates was higher than out-patients. Conclusion CD01 together with CD03 showed a higher sensitivity than using CD02 and CD03 combination for ESBL-producing in clinical isolates. CD04 can further increase the sensitivity of detection of ESBL-production if the strain showed negative results with CD01 or CD03. Presence of AmpC strain may explain why PCR identified more ESBL-producers than the combined discs method. Over use of 3rd generation cephalosporin may be the reason for the high carriage rate of ESBL in fecal specimens. Control the use of cephalosporin is a must to control the spread and increase of ESBL-producing strains.

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