Molecular diversity of bla genes in Klebsiella pneumoniae and Escherichia coli isolates
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Dissertation presented to obtain a Ph.D. degree in Biology, speciality Microbiology, by Universidade Nova de Lisboa, Faculdade de Ciencias e TecnologiaCite
Aztreonam
Enterobacter cloacae
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Klebsiella infections
Molecular Epidemiology
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In this study, we sought to determine the prevalence of the plasmid-mediated quinolone resistance (PMQR) genes aac(6')-Ib-cr, qepA, and oqxAB in extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates in South Korea. In total, 104 isolates (63 E. coli and 41 K. pneumoniae) were collected. We found that 23 of the 63 (36.5%) E. coli and nine of the 41 (22.0%) K. pneumoniae isolates were positive for aac(6')-Ib-cr. No isolate was positive for qepA, while transferable oqxAB was detected only in 10 (24.4%) K. pneumoniae isolates. Among the 32 aac(6')-Ib-cr-positive isolates, 30 (93.8%) were positive for both aac(6')-Ib-cr and bla(CTX-M) (CTX-M-15, -14, and -57). Our results suggest that PMQR determinants are highly prevalent in ESBL-producing E. coli and K. pneumoniae isolates in Korea.
Quinolone
Beta-lactamase
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We describe in vivo selection of a Klebsiella pneumoniae strain with diminished imipenem susceptibility attributable to plasmid-encoded ACC-1 beta-lactamase production and loss of a 36-kDa major outer membrane protein, together with transfer of this plasmid from K. pneumoniae to Escherichia coli in a Tunisian infant.
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The aim of this study was to investigate the prevalences of plasmid-mediated AmpC beta-lactamases (PABLs) in isolates of Escherichia coli and Klebsiella spp. from a university hospital in China. A total of 1,935 consecutive nonrepeat clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca were collected between January 2003 and July 2005. The isolates with cefoxitin zone diameters less than 18 mm (screen positive) were selected for PCR of the bla(AmpC) genes and sequencing. Fifty-four (2.79%) isolates harbored PABLs, as demonstrated by PCR and isoelectric focusing. Sequence analysis revealed the presence of bla(DHA-1) and bla(CMY-2) genes. The Southern blot hybridization studies confirmed that bla(CMY-2) and bla(DHA-1) were located on plasmids. Based on species, PABLs were detected in 4.29% (29 isolates of DHA-1 and 1 isolate of CMY-2) of K. pneumoniae, 1.91% (11 isolates of DHA-1 and 12 isolates of CMY-2) of E. coli, and 3.03% (1 isolate of DHA-1) of K. oxytoca isolates. In contrast to our anticipation, the occurrence rate of DHA-1-producing K. pneumonia significantly decreased (P < 0.01), from 7.54% in 2003 to 2.72% in 2004. The results of random amplified polymorphic DNA analysis indicate that the prevalences of DHA-1-producing K. pneumoniae and CMY-2-producing E. coli strains were not due to epidemic strains. In conclusion, DHA-1 was the most prevalent acquired AmpC beta-lactamase in this collection of isolates from a medical center in China, and DHA-1-producing K. pneumoniae was the most prevalent bacterium harboring a PABL. To the best of our knowledge, this is the first report of CMY-2-type AmpC beta-lactamases in the Chinese mainland.
Klebsiella oxytoca
Klebsiella pneumonia
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Objective To study the expression and resistance of plasmid-mediated AmpC gene in continuous isolates from Escherichia coli and Klebsiella pneumoniae. Methods The DHA and ATC-1 types of AmpC enzymes in continuous isolates from Escherichia coli and Klebsiella pneumoniae were detected by polymerase chain reaction(PCR). Results In 68 isolates Escherichia coli, there are 4 isolates, whose ATC-1 types were positive, and the DHA types were all negative. In 44 isolates Klebsiella pneumoniae, there are 4 isolates, whose DHA types were positive, and ATC-1 types were all negative. Conclusions Plasmid-mediated AmpC lactamase gene can be transferred to allogenic and xenogenic bacteria by conversion and conjugation. So they should be under careful surveillance.
Klebsiella
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ObjectivesTo characterize the location and genetic environments of qnr, aac(6′)-Ib-cr and qepA genes related to quinolone resistance in 19 Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca strains.
Klebsiella oxytoca
Klebsiella
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Nocosomial pathogen Klebsiella pneumoniae is a gram - negative bacterium that carries multiple antimicrobial resistant genes. Conjugative method was used for investigating of gene transfer from clinical carbapenem-resistant K. pneumoniae isolates to a recipient E. coli J53 in vitro. Multiplex PCR & Real-time PCR was used for detection of transferable genes among these strains. Transconjugants showed resistance to multiple antibiotics due to the presence of ESBLs & AmpC -lactamase as well as carbapenemase encoding genes. This is the great concern in Vietnam because resistant E. coli may become part of the normal gut flora and thereby a notable source of infections among sick and healthy persons in healthcare settings and in the community.
Carbapenem
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Two hundred ninety isolates of Escherichia coli were investigated for the production of extended-spectrum beta-lactamases (ESBLs). Fourteen (4.8%) of the 290 strains were found to produce ESBLs. Each of the 14 strains produced one or two ESBLs, as follows: 10 strains produced TEM-52, 1 strain produced SHV-2a, 1 strain produced SHV-12, 1 strain produced a CMY-1-like enzyme, and 1 strain expressed SHV-2a and a CMY-1-like enzyme. Another two strains for which the MICs of ceftazidime and cefoxitin were high, were probable AmpC enzyme hyperproducers. Because of the high prevalence of TEM-52 in E. coli isolates, we further investigated the TEM-type ESBLs produced by Klebsiella pneumoniae in order to observe the distribution of TEM-52 enzymes among Enterobacteriaceae in Korea. All TEM enzymes produced by 12 strains of K. pneumoniae were identified as TEM-52. To evaluate the genetic relatedness among the organisms, ribotyping of TEM-52-producing E. coli and K. pneumoniae was performed. The ribotyping profiles of the organisms showed similar but clearly different patterns. In conclusion, TEM-52 is the most prevalent TEM-type ESBL in Korea.
Ribotyping
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Klebsiella
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Multilocus sequence typing
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