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Epidemiology of CTX-M type extended-spectrum beta-lactamases in escherichia coli isolates from human and animalsLo, Wai-u., 羅慧瑜. January 2011 (has links)
published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy
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Epidemiology of CTX-M type extended-spectrum beta-lactamase-producing escherichia coli among blood culture isolates in Hong KongYeung, Man-kiu., 楊敏翹. January 2011 (has links)
Dissemination 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. / published_or_final_version / Microbiology / Master / Master of Philosophy
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F exclusion of bacteriophage T7Cheng, Xiaogang 28 August 2008 (has links)
Not available / text
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Functional and structural studies of protein inhibitors of RNase E activity that globally modulate mRNA abundance in Escherichia coliGao, Junjun 28 August 2008 (has links)
Not available / text
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Characterization and engineering of the twin-arginine translocation pathway of Escherichia coliErcek, Danielle Tullman 28 August 2008 (has links)
Not available / text
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Prevalence and characterization of Escherichia coli O157:H7 isolates from meat and meat products sold in Amathole District, Eastern Cape Province of South AfricaAbongo, BO, Momba, MNB 01 October 2008 (has links)
a b s t r a c t
Meat and meat products have been implicated in outbreaks of Escherichia coli O157:H7 in most parts of
the world. In the Amathole District Municipality of the Eastern Cape Province of South Africa, a large
number of households consume meat and meat products daily, although the microbiological quality of
these types of food is questionable. The present study investigated the prevalence of E. coli O157:H7
isolated from selected meat and meat products (45 samples each of biltong, cold meat, mincemeat, and
polony) sold in this area. Strains of E. coli O157:H7 were isolated by enrichment culture and confirmed by
polymerase chain reaction (PCR). Also investigated were the antibiogram profiles of the E. coli O157:H7
isolates. Five (2.8%) out of 180 meat and meat products examined were positive for E. coli O157:H7 that
carried the fliCH7, rfbEO157, and eaeA genes. Two of the E. coli O157:H7 isolates were resistant against all
the eight antibiotics tested. To prevent E. coli O157:H7 infections, meat and meat products such as
biltong, cold meat, mincemeat and polony should be properly handled, and packed in sterile polyvinyl
wrappers.
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Bioorganic and biochemical studies of cyclopropane fatty acid synthase from Escherichia coliPaschal, Beth Martell, 1975- 26 July 2011 (has links)
Not available / text
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Extended-spectrum beta-lactamases in fecal isolates of Escherichia coli from human and food animalsDuan, Rongshuai., 段榮帥. January 2005 (has links)
published_or_final_version / abstract / Microbiology / Master / Master of Philosophy
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Heterologous expression and localization of cryptic haloacid dehalogenase Chd1 of Burkholderia cepacia MBA4施國雄, Sze, Johnny. January 2001 (has links)
published_or_final_version / Botany / Master / Master of Philosophy
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EARLY EVENTS IN DNA METABOLISM FOLLOWING INFECTION OF ESCHERICHIA COLI BY BACTERIOPHAGE-T4Scofield, Margaret Sisson, 1947- January 1973 (has links)
No description available.
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