1,721,006 research outputs found
High specificity of cphA-encoded metallo-β-lactamase from Aeromonas hydrophila AEO36 for carbapenems and its contribution to β-lactam resistance
Full text linkThe Aeromonas hydrophila AE036 chromosome contains a cphA gene encoding a metallo-beta-lactamase highly active against carbapenem antibiotics. This enzyme was induced in strain AE036 to the same extent by both benzylpenicillin and imipenem. When the cphA gene was inserted into plasmid pACYC184, used to transform Escherichia coli DH5 alpha, the MICs of imipenem, meropenem, and penem HRE664 for recombinant clone DH5 alpha(pAA20R), expressing the Aeromonas metallo-beta-lactamase, were significantly increased, but those of penicillins and cephalosporins were not. When the metallo-beta-lactamase purified from E. coli DH5 alpha(pAA20R) was assayed with several beta-lactam substrates, it hydrolyzed carbapenems but not penicillins or cephalosporins efficiently. These results demonstrate that this metallo-beta-lactamase possesses an unusual spectrum of activity compared with all the other class B enzymes identified so far, being active on penems and carbapenems only. This enzyme may thus contribute to the development of resistance to penems and carbapenems but not other beta-lactams
Potent inhibitory activity of taniborbactam towards NDM-1 and NDM-1Q119X mutants, and in vitro activity of cefepime/taniborbactam against MBLs producing Enterobacterales
No full textObjective: This study aimed to investigate the in vitro activity of taniborbactam (VNRX-5133), a novel broad-spectrum bicyclic boronate, against NDM-1 and Q119E, Q119K, Q119C, Q119F, Q119V, and Q119Y NDM-1 variants, which showed an increased activity towards some β-lactams, including cefepime. Methods: Inhibition kinetic assays were spectrophotometrically performed using cefepime (50 μM) as the reporter substrate and 80 nM of each enzyme. Taniborbactam behaves as a competitive inhibitor towards NDM-1 and NDM-1 Q119 variants with lower Ki values (range 3–16 nM). The phenotypic profile was assessed in both Enterobacterales clinical isolates and engineered Escherichia coli BL21(DE3) strains by conventional broth microdilution procedures according to the Clinical and Laboratory Standards Institute (CLSI). Results: Taniborbactam at a fixed concentration of 4 mg/L was able to restore activity of cefepime in 24 of 26 Enterobacterales clinical isolates harbouring metallo-β-lactamases with MIC50/MIC90 values of 14 mg/L. Cefepime MICs were drastically reduced in all clinical isolates and in NDM-1 and Q119X producing Escherichia coli BL21(DE3). Taniborbactam was unable to restore susceptibility to cefepime in two IMP variants producing clinical isolates. Conclusion: The inhibition level of NDM enzymes provided by taniborbactam protects the antibacterial activity of cefepime from this important metallo-β-lactamase
A new metallo-beta-lactamase gene (blaIMP-22) harboured in class 1 integron from Pseudomonas fluorescens
No full textItalian survey on comparative levofloxacin susceptibility in 334 clinical isolates of Pseudomonas aeruginosa
No full textA national survey on susceptibility patterns of 334 Pseudomonas aeruginosa isolates from intensive care units and hematology and oncology wards from 13 Italian hospitals compared the in vitro activity of levofloxacin, an injectable oral fluoroquinolone, to those of ciprofloxacin, ofloxacin, ceftazidime, imipenem, amikacin, and gentamicin. Amikacin and imipenem had the best susceptibility profiles. The activity of levofloxacin was superior to those of the other quinolones and was comparable to that of ceftazidime. The effect of levofloxacin in vitro on P. aeruginosa clinical isolates suggests that further clinical investigations are warranted
QnrB9 in association with TEM-116 extended-spectrum beta-lactamase in Citrobacter freundii isolated from sewage effluent: first report from Italy
No full textThe aim of the present study was to investigate the mechanism of quinolone and β-lactam resistance in an isolate of Citrobacter freundii PC2/08 collected from sewage effluent from L'Aquila, Italy. qnrB-9 and bla TEM-116 were co-expressed in a large plasmid identified in C. freundi PC2/08 strain. Compared to TEM-1, TEM-116 showed two single mutations: V84I and A184V. The plPC2/08 plasmid conferred resistance to several β-lactams and fluoroquinolones. Tazobactam could be considered a good inhibitor whereas clavulanic acid was unable to restore susceptibility to amoxicillin. The QnrB-9 element seems to confer the same level of resistance to levofloxacin and ciprofloxacin with minimum inhibitory concentration (MIC) values of 4 mg/L for either. In this study, we confirm the common association of plasmid-mediated quinolone resistance with extended-spectrum β-lactamase (ESβL) production. This is the first finding in Italy of qnrB9 and TEM-116 in a non-clinical or animal strain. © E.S.I.F.T. srl
Whole-Genome Sequencing of ST2 A. baumannii Causing Bloodstream Infections in COVID-19 Patients
No full textA total of 43 A. baumannii strains, isolated from 43 patients affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and by bacterial sepsis, were analyzed by antimicrobial susceptibility testing. All strains were resistant to almost three different classes of antibiotics, including carbapenems and colistin. The whole-genome sequencing (WGS) of eight selected A. baumannii isolates showed the presence of different insertion sequences (ISs), such as ISAba13, ISAba26, IS26, ISVsa3, ISEc29, IS6100 and IS17, giving to A. baumannii a high ability to capture and mobilize antibiotic resistance genes. Resistance to carbapenems is mainly mediated by the presence of OXA-23, OXA-66 and OXA-82 oxacillinases belonging to OXA-51-like enzymes. The presence of AmpC cephalosporinase, ADC-25, was identified in all A. baumannii. The pathogenicity of A. baumannii was exacerbated by the presence of several virulence factors. The multi-locus sequence typing (MLST) analysis showed that all strains belong to sequence type 2 (ST) international clone
First Report from Italy of bla(VIM-1) and bla(TEM-1) Genes in Pseudomonas putida and Acinetobacter baumannii Isolated from Wastewater
No full textBiochemical characterization of laboratory mutants of the TEM-60 extended-spectrum beta-lactamase
No full textThree mutants of the extended-spectrum β-lactamase TEM-60, the P51L, K104E, and S164R mutants, were constructed by site-directed mutagenesis. The kinetic parameters of the mutated enzymes and interactions of inhibitors were significantly different from those of TEM-60, revealing that the L51P mutation plays an important role in enzyme activity and stability in the TEM-60 background
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