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postgraduate thesis: Epidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong Kong

TitleEpidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong Kong
Authors
Advisors
Advisor(s):Ho, PLTse, H
Issue Date2011
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Yeung, M. [楊敏翹]. (2011). Epidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong Kong. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4732623
AbstractDissemination of CTX-M type extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) is a serious health issue in Hong Kong. However, research knowledge concerning its dissemination mechanism and plasmid characteristics over time in health care setting is still limited. This study was conducted to characterize ESBL-producing E. coli from blood culture isolates and the epidemiology of the plasmids harboring CTX-M-14 collected from a healthcare region in Hong Kong from two periods of time. A total of 167 ESBL-producing E. coli in blood culture specimens were retrieved from period 1 (1996 - 1999, n = 50) and period 2 (2007 - 2008, n = 117). Antimicrobial susceptibilities were defined by disk diffusion method according to CLSI. Phylogenetic groups and CTX-M enzymes were detected among all the ESBL-producers. Clonal relatedness of the hosts was analyzed by pulsed-field gel electrophoresis and multi-locus sequence typing. A subset of 65 CTX-M-14-producing isolates was undergone for further plasmid characterization. Conjugation, PCR-based replicon typing, S1-PFGE, southern-blot hybridization, and genetic environment PCRs were performed. Plasmid PCR-restriction fragment length polymorphism (pRFLP), F-allele replicon sequence typing and variable region PCRs were studied in 54 F-plasmids obtained. Results showed that over half of the ESBL-positive isolates were non-susceptible to ciprofloxacin, cotrimoxazole and gentamicin. A surprisingly high number of CTX-M-type ESBL was carried by 98.2% (164/167) of the isolates. CTX-M-9 group (89.8%, 150/167) and CTX-M-14 (103/109) were predominantly found among both periods. Overall, nearly half (41.3%, 69/167) of the isolates belonged to 5 major clones. Clonal types undetermined-ST68 (n = 18) and O102-ST405 (n = 15) were dominant in period 1 while clonal types O25b-ST131 (n = 30), O15-ST69 (n = 5) and O12-ST12 (n = 3) emerged in period 2. Among a subset of 65 CTX-M-14 plasmids, most of them were transferable (84.6%, 55/65) with high frequency, similar plasmid sizes and genetic environment ISEcp1-blaCTX-M-14-IS903 (90.8%, 59/65). Replicon types of the CTX-M-14 encoding plasmids were FII (n = 48) or FII ± FIA/FIB types (n = 6), I1-I (n = 3), B/O (n = 2), K (n = 1) and undetermined (n = 4). Subtyping of 54 IncF plasmids by replicon sequence typing, pRFLP and PCR for marker genes (yac, malB, eitA, eitC and parAB) showed that 79.6% (43/54) of the plasmid subset exhibited identical or highly similar results with the completely sequenced plasmid, pHK01 (E. coli isolated from urine sample of a patient in Hong Kong, 2004). These 43 plasmids were originated from both period 1 (n = 11) and period 2 (n = 32). These pHK01-like plasmids were found to have spread to the major clones (ST68, ST405 and ST131) and multiple singleton isolates of all four phylogenetic groups. In conclusion, this study demonstrated the widespread dissemination of pHK01-like CTX-M-14 encoding plasmids among isolates of diverse genetic lineages over a decade. The dissemination was probably due to both clonal expansion and horizontal gene transfer of pHK01-like IncF plasmid.
DegreeMaster of Philosophy
SubjectBeta lactamases.
Escherichia coli - Genetics.
Dept/ProgramMicrobiology

 

DC FieldValueLanguage
dc.contributor.advisorHo, PL-
dc.contributor.advisorTse, H-
dc.contributor.authorYeung, Man-kiu.-
dc.contributor.author楊敏翹.-
dc.date.issued2011-
dc.identifier.citationYeung, M. [楊敏翹]. (2011). Epidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong Kong. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4732623-
dc.description.abstractDissemination of CTX-M type extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) is a serious health issue in Hong Kong. However, research knowledge concerning its dissemination mechanism and plasmid characteristics over time in health care setting is still limited. This study was conducted to characterize ESBL-producing E. coli from blood culture isolates and the epidemiology of the plasmids harboring CTX-M-14 collected from a healthcare region in Hong Kong from two periods of time. A total of 167 ESBL-producing E. coli in blood culture specimens were retrieved from period 1 (1996 - 1999, n = 50) and period 2 (2007 - 2008, n = 117). Antimicrobial susceptibilities were defined by disk diffusion method according to CLSI. Phylogenetic groups and CTX-M enzymes were detected among all the ESBL-producers. Clonal relatedness of the hosts was analyzed by pulsed-field gel electrophoresis and multi-locus sequence typing. A subset of 65 CTX-M-14-producing isolates was undergone for further plasmid characterization. Conjugation, PCR-based replicon typing, S1-PFGE, southern-blot hybridization, and genetic environment PCRs were performed. Plasmid PCR-restriction fragment length polymorphism (pRFLP), F-allele replicon sequence typing and variable region PCRs were studied in 54 F-plasmids obtained. Results showed that over half of the ESBL-positive isolates were non-susceptible to ciprofloxacin, cotrimoxazole and gentamicin. A surprisingly high number of CTX-M-type ESBL was carried by 98.2% (164/167) of the isolates. CTX-M-9 group (89.8%, 150/167) and CTX-M-14 (103/109) were predominantly found among both periods. Overall, nearly half (41.3%, 69/167) of the isolates belonged to 5 major clones. Clonal types undetermined-ST68 (n = 18) and O102-ST405 (n = 15) were dominant in period 1 while clonal types O25b-ST131 (n = 30), O15-ST69 (n = 5) and O12-ST12 (n = 3) emerged in period 2. Among a subset of 65 CTX-M-14 plasmids, most of them were transferable (84.6%, 55/65) with high frequency, similar plasmid sizes and genetic environment ISEcp1-blaCTX-M-14-IS903 (90.8%, 59/65). Replicon types of the CTX-M-14 encoding plasmids were FII (n = 48) or FII ± FIA/FIB types (n = 6), I1-I (n = 3), B/O (n = 2), K (n = 1) and undetermined (n = 4). Subtyping of 54 IncF plasmids by replicon sequence typing, pRFLP and PCR for marker genes (yac, malB, eitA, eitC and parAB) showed that 79.6% (43/54) of the plasmid subset exhibited identical or highly similar results with the completely sequenced plasmid, pHK01 (E. coli isolated from urine sample of a patient in Hong Kong, 2004). These 43 plasmids were originated from both period 1 (n = 11) and period 2 (n = 32). These pHK01-like plasmids were found to have spread to the major clones (ST68, ST405 and ST131) and multiple singleton isolates of all four phylogenetic groups. In conclusion, this study demonstrated the widespread dissemination of pHK01-like CTX-M-14 encoding plasmids among isolates of diverse genetic lineages over a decade. The dissemination was probably due to both clonal expansion and horizontal gene transfer of pHK01-like IncF plasmid.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B47326232-
dc.subject.lcshBeta lactamases.-
dc.subject.lcshEscherichia coli - Genetics.-
dc.titleEpidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong Kong-
dc.typePG_Thesis-
dc.identifier.hkulb4732623-
dc.description.thesisnameMaster of Philosophy-
dc.description.thesislevelMaster-
dc.description.thesisdisciplineMicrobiology-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b4732623-
dc.date.hkucongregation2012-

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