scholarly journals Characterization of OXA-25, OXA-26, and OXA-27, Molecular Class D β-Lactamases Associated with Carbapenem Resistance in Clinical Isolates of Acinetobacter baumannii

2001 ◽  
Vol 45 (2) ◽  
pp. 583-588 ◽  
Author(s):  
Mariya Afzal-Shah ◽  
Neil Woodford ◽  
David M. Livermore
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Acinetobacter Baumannii ◽  
Sequence Data ◽  
Carbapenem Resistance ◽  
Hydrolytic Activity ◽  
Amino Acid Homology ◽  
Class D ◽  
Weak Activity

ABSTRACT Carbapenem resistance in Acinetobacter spp. is increasingly being associated with OXA-type β-lactamases with weak hydrolytic activity against imipenem and meropenem. Such enzymes were characterized from Acinetobacter isolates collected in Belgium, Kuwait, Singapore, and Spain. The isolates from Spain and Belgium had novel class D β-lactamases that were active against carbapenems. These were designated OXA-25 and OXA-26, respectively, and had >98% amino acid homology with each other and with the OXA-24 enzyme recently described by others from an Acinetobacterisolate collected elsewhere in Spain. The isolate from Singapore had OXA-27 β-lactamase, another novel class D type with only 60% homology to OXA-24, -25, and -26, but with 99% homology to OXA-23 (ARI-1), described previously from an Acinetobacter baumannii isolate collected in Scotland. Sequence data were not obtained for the carbapenem-hydrolyzing OXA enzyme from the isolate from Kuwait; nevertheless, the enzyme was phenotypically similar to OXA-25 and -26. The enzymes OXA-23, -24, -25, -26, and -27 retained the STFK and SXV motifs typical of class D β-lactamases, but the YGN motif was altered to FGN. The KTG motif was retained by OXA-27 and -23 but was replaced by KSG in OXA-24, -25, and -26. OXA-25 and -26 enzymes were strongly active against oxacillin, but unusually for an OXA-type β-lactamase, OXA-27 had apparently weak activity, although measurement was complicated by biphasic kinetics. None of the new enzymes was transmissible to Escherichia coli recipients. Many Acinetobacter isolates are multiresistant to other antibiotics, and the emergence of class D enzymes with carbapenem-hydrolyzing activity is a disturbing development for antimicrobial chemotherapy.

scholarly journals TEM-109 (CMT-5), a Natural Complex Mutant of TEM-1 β-Lactamase Combining the Amino Acid Substitutions of TEM-6 and TEM-33 (IRT-5)

2005 ◽  
Vol 49 (11) ◽  
pp. 4443-4447 ◽  
Author(s):  
F. Robin ◽  
J. Delmas ◽  
C. Chanal ◽  
D. Sirot ◽  
J. Sirot ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Protein Sequence ◽  
Hydrolytic Activity ◽  
Conjugative Plasmid ◽  
Amino Acid Substitutions ◽  
Resistance Phenotype ◽  
Natural Complex ◽  
Synergy Test

ABSTRACT Escherichia coli CF349 exhibited a complex β-lactam resistance phenotype, including resistance to amoxicillin and ticarcillin alone and in combination with clavulanate and to some extended-spectrum cephalosporins. The double-disk synergy test was positive. CF349 harbored an 85-kb conjugative plasmid which encoded a β-lactamase of pI 5.9. The corresponding bla gene was identified by PCR and sequencing as a bla TEM gene. The deduced protein sequence revealed a new complex mutant of TEM-1 β-lactamase designated TEM-109 (CMT-5). TEM-109 contained both the substitutions Glu104Lys and Arg164His of the expanded-spectrum β-lactamase (ESBL) TEM-6 and Met69Leu of the inhibitor-resistant TEM-33 (IRT-5). TEM-109 exhibited hydrolytic activity against ceftazidime similar to that of TEM-6 (k cat, 56 s−1 and 105 s−1, respectively; Km values, 226 and 247 μM, respectively). The 50% inhibitory concentrations of clavulanate and tazobactam (0.13 μM and 0.27 μM, respectively) were 5- to 10-fold higher for TEM-109 than for TEM-6 (0.01 and 0.06 μM, respectively) but were almost 10-fold lower than those for TEM-33. The characterization of this novel CMT, which exhibits a low level of resistance to inhibitors, highlights the emergence of this new ESBL type.

Characterization of two plasmid-encoded cefotaximases found in clinical Escherichia coli isolates: CTX-M-65 and a novel enzyme, CTX-M-87

2009 ◽  
Vol 58 (6) ◽  
pp. 811-815 ◽  
Author(s):  
Jun Yin ◽  
Jun Cheng ◽  
Zhen Sun ◽  
Ying Ye ◽  
Yu-Feng Gao ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Catalytic Activity ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Hydrolytic Activity ◽  
E Coli ◽  
High Affinity ◽  
Extended Spectrum ◽  
M 14

Three clinical strains of Escherichia coli (p168, p517 and p667) were collected in 2006 from three hospitals in Anhui Province (China). PCR and DNA sequencing revealed that E. coli p168 carried a novel extended-spectrum β-lactamase (ESBL), which was designated CTX-M-87. The extended-spectrum β-lactamase which was carried by E. coli p517 and E. coli p667 was previously named CTX-M-65. The deduced amino acid sequence of CTX-M-87, with pI 9.1, differed from that of CTX-M-14 by the substitutions Ala77→Val and Pro167→Leu. Like CTX-M-14, CTX-M-87 had a more potent hydrolytic activity against cefotaxime than against ceftazidime and had high affinity for cefuroxime and cefotaxime. These data show that mutations at position 167 in CTX-M do not always affect catalytic activity and substrate preference.

scholarly journals OXA-58, a Novel Class D β-Lactamase Involved in Resistance to Carbapenems in Acinetobacter baumannii

2005 ◽  
Vol 49 (1) ◽  
pp. 202-208 ◽  
Author(s):  
Laurent Poirel ◽  
Sophie Marqué ◽  
Claire Héritier ◽  
Christine Segonds ◽  
Gérard Chabanon ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acinetobacter Baumannii ◽  
Reference Strain ◽  
Carbapenem Resistance ◽  
Amino Acid Identity ◽  
Cloning And Expression ◽  
Acid Identity ◽  
Carbapenem Resistant ◽  
Class D ◽  
Insertion Elements

ABSTRACT A carbapenem-resistant Acinetobacter baumannii strain was isolated in Toulouse, France, in 2003. Cloning and expression in Escherichia coli identified the carbapenem-hydrolyzing β-lactamase OXA-58, which is weakly related (less than 50% amino acid identity) to other oxacillinases. It hydrolyzed penicillins, oxacillin, and imipenem but not expanded-spectrum cephalosporins. The bla OXA-58 gene was located on a ca. 30-kb non-self-transferable plasmid. After electrotransformation in the A. baumannii CIP7010T reference strain, it conferred reduced susceptibility to carbapenems. The bla OXA-58 gene was bracketed by two novel ISAba3-like insertion elements. This study describes a newly characterized β-lactamase that may contribute to carbapenem resistance in A. baumannii.

scholarly journals OXA-235, a Novel Class D β-Lactamase Involved in Resistance to Carbapenems in Acinetobacter baumannii

2013 ◽  
Vol 57 (5) ◽  
pp. 2121-2126 ◽  
Author(s):  
Paul G. Higgins ◽  
Francisco J. Pérez-Llarena ◽  
Esther Zander ◽  
Ana Fernández ◽  
Germán Bou ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acinetobacter Baumannii ◽  
Carbapenem Resistance ◽  
The United States ◽  
Amino Acid Sequences ◽  
Insertion Sequences ◽  
Content Type ◽  
Resistance Determinants ◽  
Class D ◽  
Amino Acid Variants

ABSTRACTWe investigated the mechanism of carbapenem resistance in 10Acinetobacter baumanniistrains isolated from the United States and Mexico between 2005 and 2009. The detection of known metallo-β-lactamase or carbapenem-hydrolyzing oxacillinase (OXA) genes by PCR was negative. The presence of plasmid-encoded carbapenem resistance genes was investigated by transformation ofA. baumanniiATCC 17978. Shotgun cloning experiments and sequencing were performed, followed by the expression of a novel β-lactamase inA. baumannii. Three novel OXA enzymes were identified, OXA-235 in 8 isolates and the amino acid variants OXA-236 (Glu173-Val) and OXA-237 (Asp208-Gly) in 1 isolate each. The deduced amino acid sequences shared 85% identity with OXA-134, 54% to 57% identities with the acquired OXA-23, OXA-24, OXA-58, and OXA-143, and 56% identity with the intrinsic OXA-51 and, thus, represent a novel subclass of OXA. The expression of OXA-235 inA. baumanniiled to reduced carbapenem susceptibility, while cephalosporin MICs were unaffected. Genetic analysis revealed thatblaOXA-235,blaOXA-236, andblaOXA-237were bracketed between two ISAba1insertion sequences. In addition, the presence of these acquired β-lactamase genes might result from a transposition-mediated mechanism. This highlights the propensity ofA. baumanniito acquire multiple carbapenem resistance determinants.

scholarly journals Characterization of a Nosocomial Outbreak Caused by a Multiresistant Acinetobacter baumannii Strain with a Carbapenem-Hydrolyzing Enzyme: High-Level Carbapenem Resistance inA. baumannii Is Not Due Solely to the Presence of β-Lactamases

2000 ◽  
Vol 38 (9) ◽  
pp. 3299-3305 ◽  
Author(s):  
Germán Bou ◽  
Gonzalo Cerveró ◽  
M. Angeles Domínguez ◽  
Carmen Quereda ◽  
Jesús Martínez-Beltrán
Keyword(s):  
Acinetobacter Baumannii ◽  
Carbapenem Resistance ◽  
Pulsed Field Gel Electrophoresis ◽  
Nosocomial Outbreak ◽  
Chromosomal Dna ◽  
Penicillin Binding Proteins ◽  
Class D ◽  
High Level ◽  
Genotype A

From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid, Spain, were determined to be either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs, 128 to 256 μg/ml). A wide antibiotic multiresistance profile was observed with IMRAB strains. For typing IMRAB isolates, pulsed-field gel electrophoresis was used. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during, and after the outbreak were included in this study. The molecular-typing results showed that the outbreak was caused by a single IMRAB strain (genotype A). By cloning experiments we identified a class D β-lactamase (OXA-24) encoded in the chromosomal DNA of this IMRAB strain which showed carbapenem hydrolysis. Moreover, the outer membrane profile of the IMRAB strain showed a reduction in the expression of two porins at 22 and 33 kDa when compared with genetically related IMSAB isolates. In addition no efflux mechanisms were identified in the IMRAB strains. In summary, we report here the molecular characterization of a nosocomial outbreak caused by one multiresistant A. baumannii epidemic strain that harbors a carbapenem-hydrolyzing enzyme. Although alterations in the penicillin-binding proteins cannot be ruled out, the reduction in the expression of two porins and the presence of this OXA-derived β-lactamase are involved in the carbapenem resistance of the epidemic nosocomial IMRAB strain.

Expression and characterization of an α-glucosidase from Thermoanaerobacter ethanolicus JW200 with potential for industrial application

Biologia ◽  
2009 ◽  
Vol 64 (6) ◽  
Author(s):  
Yue-Hong Wang ◽  
Yu Jiang ◽  
Zuo-Ying Duan ◽  
Wei-Lan Shao ◽  
Hua-Zhong Li
Keyword(s):  
Escherichia Coli ◽  
Heat Shock ◽  
Optimal Condition ◽  
Industrial Application ◽  
Conversion Rate ◽  
Hydrolytic Activity ◽  
Thermoanaerobacter Ethanolicus ◽  
Transglycosylation Activity

AbstractIn this study, a new α-glucosidase gene from Thermoanaerobacter ethanolicus JW200 was cloned and expressed in Escherichia coli by a novel heat-shock vector pHsh. The recombinant α-glucosidase exhibited its maximum hydrolytic activity at 70°C and pH 5.0∼5.5. With p-nitrophenyl-α-D-glucoside as a substrate and under the optimal condition (70°C, pH 5.5), K m and V max of the enzyme was 1.72 mM and 39 U/mg, respectively. The purified α-glucosidase could hydrolyze oligosaccharides with both α-1,4 and α-1,6 linkages. The enzyme also had strong transglycosylation activity when maltose was used as sugar donor. The transglucosylation products towards maltose are isomaltose, maltotriose, panose, isomaltotriose and tetrasaccharides. The enzyme could convert 400 g/L maltose to oligosaccharides with a conversion rate of 52%, and 83% of the oligosaccharides formed were prebiotic isomaltooligosaccharides (containing isomaltose, panose and isomaltotriose).

Heterologous expression and characterization of l-amino acid deaminases from Proteus mirabilis in Escherichia coli

2008 ◽  
Vol 136 ◽  
pp. S300 ◽  
Author(s):  
Jin-Oh Baek ◽  
Jeong-Woo Seo ◽  
Ohsuk Kwon ◽  
Su-Il Seong ◽  
Ik-Hwan Kim ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Heterologous Expression ◽  
Proteus Mirabilis

scholarly journals Characterization of the 6'-N-aminoglycoside acetyltransferase gene aac(6')-Im [corrected] associated with a sulI-type integron.

1997 ◽  
Vol 41 (2) ◽  
pp. 314-318 ◽  
Author(s):  
E Hannecart-Pokorni ◽  
F Depuydt ◽  
L de wit ◽  
E van Bossuyt ◽  
J Content ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Resistance Gene ◽  
Citrobacter Freundii ◽  
Gram Negative ◽  
Gene Environment ◽  
Insert Region ◽  
Klebsiella Spp

The amikacin resistance gene aac(6')-Im [corrected] from Citrobacter freundii Cf155 encoding an aminoglycoside 6'-N-acetyltransferase was characterized. The gene was identified as a coding sequence of 521 bp located down-stream from the 5' conserved segment of an integron. The sequence of this aac(6')-Im [corrected] gene corresponded to a protein of 173 amino acids which possessed 64.2% identity in a 165-amino-acid overlap with the aac(6')-Ia gene product (F.C. Tenover, D. Filpula, K.L. Phillips, and J. J. Plorde, J. Bacteriol. 170:471-473, 1988). By using PCR, the aac(6')-Im [corrected] gene could be detected in 8 of 86 gram-negative clinical isolates from two Belgian hospitals, including isolates of Citrobacter, Klebsiella spp., and Escherichia coli. PCR mapping of the aac(6')-Im [corrected] gene environment in these isolates indicated that the gene was located within a sulI-type integron; the insert region is 1,700 bases long and includes two genes cassettes, the second being ant (3")-Ib.

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