scholarly journals Assembly of an in vitro synthesized Escherichia coli outer membrane porin into its stable trimeric configuration.

1990 ◽  
Vol 265 (8) ◽  
pp. 4646-4651
Author(s):  
H de Cock ◽  
R Hendriks ◽  
T de Vrije ◽  
J Tommassen
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Outer Membrane Porin

scholarly journals 610. Meropenem-vaborbactam (MV) In Vitro Activity Against Carbapenem-Resistant Klebsiella pneumoniae (CRKP) Isolates with Outer Membrane Porin Gene Mutations

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S285-S285 ◽  
Author(s):  
Mohamad Yasmin ◽  
Steven Marshall ◽  
Michael Jacobs ◽  
Daniel D Rhoads ◽  
Laura J Rojas ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Gene Mutations ◽  
Underlying Mechanism ◽  
Clinical Isolates ◽  
Historical Cohort ◽  
Carbapenem Resistant ◽  
Outer Membrane Porin ◽  
Tract Infections

Abstract Background Vaborbactam is a cyclic boronic acid β-lactamase inhibitor (BLI) developed to potently inhibit Ambler class A&C enzymes, including KPC carbapenemases. Metallo-β-lactamases (MBL) and some Class D oxacillinases (OXA) are not inactivated by vaborbactam. Meropenem-vaborbactam (MV) was recently approved for the treatment of carbapenem-resistant Enterobacteriaceae complicated urinary tract infections. Recent studies have identified outer membrane porin (Ompk35 and -36) mutations in Klebsiella pneumoniae (KP) as a mechanism of decreased susceptibility to MV. We evaluated the activity of MV against a historical cohort of KP clinical isolates with these porin gene mutations. Methods WGS of carbapenem-resistant KP clinical isolates was performed and those harboring mutations in Ompk35 or Ompk36 were selected for testing. Strain KP ATCC BAA-1705 was used as a positive control. Meropenem and MV minimum inhibitory concentrations (MIC) were determined by broth microdilution (BMD) in custom 96-well plates (ThermoFisher Scientific) with a constant 8 µg/mL vaborbactam concentration. The MIC of ceftazidime–avibactam (CZA) was determined by standard BMD reference methods and interpreted according to CLSI criteria. Results A total of 105 KP isolates with either partial or complete mutations in outer membrane porin genes were included in the analysis. All isolates were resistant to Meropenem. The median MV MIC was 0.03 µg/mL (range, 0.015 to >16 µg/mL). Eleven isolates (10.4%) were resistant to MV. Sixteen additional isolates (16.1%) demonstrated higher than expected MV MICs ranging from 1 to 4 µg/mL. Only 1/11 resistant isolates harbored a gene for MBL production. Gene mutations in blaKPC were not detected. See Table 1 for characteristics of resistant isolates. Conclusion Resistance and decreased susceptibility to MV is demonstrated in a historical cohort of KP clinical isolates dating back to 2013. WGS reliably identifies porin variants secondary to gene mutations in Ompk35 and Ompk36 as the underlying mechanism of decreased susceptibility. CZA appears to retain activity against these isolates. Caution should be exercised regarding the empiric use of MV against increasingly resistant KP as a result of non-β-lactamase-mediated mechanisms. Disclosures All authors: No reported disclosures.

scholarly journals In Vitro Activity of Imipenem and Colistin against a Carbapenem-ResistantKlebsiella pneumoniaeIsolate Coproducing SHV-31, CMY-2, and DHA-1

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Hung-Jen Tang ◽  
Yee-Huang Ku ◽  
Mei-Feng Lee ◽  
Yin-Ching Chuang ◽  
Wen-Liang Yu
Keyword(s):  
Outer Membrane ◽  
Multidrug Resistant ◽  
In Vitro Activity ◽  
Carbapenem Resistant ◽  
Hip Infection ◽  
Outer Membrane Porin ◽  
The Common ◽  
Inoculum Effect ◽  
Time Kill

We investigated the synergism of colistin and imipenem against a multidrug-resistantK. pneumoniaeisolate which was recovered from a severe hip infection. PCR and DNA sequencing were used to characterize the outer membrane porin genes and the resistance genes mediating the commonβ-lactamases and carbapenemases. Synergism was evaluated by time-kill studies. TheblaSHV-31,blaCMY-2, andblaDHA-1were detected. Outer membrane porin genes analysis revealed loss ofompK36and frame-shift mutation ofompK35. The common carbapenemase genes were not found. Time-kill studies demonstrated that a combination of 1x MIC of colistin (2 mg/L) and 1x MIC of imipenem (8 mg/L) was synergistic and bactericidal but with inoculum effect. Bactericidal activity without inoculum effect was observed by concentration of 2x MIC of colistin alone or plus 2x MIC of imipenem. In conclusion, colistin plus imipenem could be an alternative option to treat carbapenem-resistantK. pneumoniaeinfections.

Overexpression of parathion hydrolase in Escherichia coli stimulates the synthesis of outer membrane porin OmpF

2006 ◽  
Vol 86 (3) ◽  
pp. 146-150 ◽  
Author(s):  
Dayananda Siddavattam ◽  
Elisha R. Raju ◽  
P.V. Emmanuel Paul ◽  
Mike Merrick
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Outer Membrane Porin ◽  
Parathion Hydrolase

scholarly journals Localized adherence by enteropathogenic Escherichia coli is an inducible phenotype associated with the expression of new outer membrane proteins.

1991 ◽  
Vol 174 (5) ◽  
pp. 1167-1177 ◽  
Author(s):  
J Vuopio-Varkila ◽  
G K Schoolnik
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
De Novo ◽  
Outer Membrane Proteins ◽  
Temporal Correlation ◽  
Enteropathogenic Escherichia Coli ◽  
E Coli

Enteropathogenic Escherichia coli grow as discrete colonies on the mucous membranes of the small intestine. A similar pattern can be demonstrated in vitro; termed localized adherence (LA), it is characterized by the presence of circumscribed clusters of bacteria attached to the surfaces of cultured epithelial cells. The LA phenotype was studied using B171, an O111:NM enteropathogenic E. coli (EPEC) strain, and HEp-2 cell monolayers. LA could be detected 30-60 min after exposure of HEp-2 cells to B171. However, bacteria transferred from infected HEp-2 cells to fresh monolayers exhibited LA within 15 min, indicating that LA is an inducible phenotype. Induction of the LA phenotype was found to be associated with de novo protein synthesis and changes in the outer membrane proteins, including the production of a new 18.5-kD polypeptide. A partial NH2-terminal amino acid sequence of this polypeptide was obtained and showed it to be identical through residue 12 to the recently described bundle-forming pilus subunit of EPEC. Expression of the 18.5-kD polypeptide required the 57-megadalton enteropathogenic E. coli adherence plasmid previously shown to be required for the LA phenotype in vitro and full virulence in vivo. This observation, the correspondence of the 18.5-kD polypeptide to an EPEC-specific pilus protein, and the temporal correlation of its expression with the development of the LA phenotype suggest that it may contribute to the EPEC colonial mode of growth.

scholarly journals Repression of the Inner Membrane Lipoprotein NlpA by Rns in Enterotoxigenic Escherichia coli

2006 ◽  
Vol 189 (5) ◽  
pp. 1627-1632 ◽  
Author(s):  
Maria D. Bodero ◽  
M. Carolina Pilonieta ◽  
George P. Munson
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Enterotoxigenic Escherichia Coli ◽  
Start Codon ◽  
Inner Membrane ◽  
E Coli ◽  
Inner Membrane Protein

ABSTRACT The expression of the inner membrane protein NlpA is repressed by the enterotoxigenic Escherichia coli (ETEC) virulence regulator Rns, a member of the AraC/XylS family. The Rns homologs CfaD from ETEC and AggR from enteroaggregative E. coli also repress expression of nlpA. In vitro DNase I and potassium permanganate footprinting revealed that Rns binds to a site overlapping the start codon of nlpA, preventing RNA polymerase from forming an open complex at nlpAp. A second Rns binding site between positions −152 and −195 relative to the nlpA transcription start site is not required for repression. NlpA is not essential for growth of E. coli under laboratory conditions, but it does contribute to the biogenesis of outer membrane vesicles. As outer membrane vesicles have been shown to contain ETEC heat-labile toxin, the repression of nlpA may be an indirect mechanism through which the virulence regulators Rns and CfaD limit the release of toxin.

scholarly journals In vitro Optimization of Ceftazidime/Avibactam for KPC-Producing Klebsiella pneumoniae

2021 ◽  
Vol 12 ◽  
Author(s):  
Yanqin Huang ◽  
Tiffany Wu ◽  
Omar Perez ◽  
Amisha P. Rana ◽  
Liang Chen ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Bactericidal Activity ◽  
Base Pair ◽  
Treatment Approach ◽  
Bacterial Regrowth ◽  
Base Pair Deletion ◽  
Outer Membrane Porin ◽  
Time Kill

Ceftazidime/avibactam is an important treatment option for infections caused by Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp), however, resistance can emerge during treatment. The objective of the study was to define the ceftazidime/avibactam concentrations required to suppress bacterial regrowth in ceftazidime/avibactam susceptible isolates and identify active therapies against ceftazidime/avibactam-resistant KPC-Kp. Time-kill assays were performed against twelve ST258 KPC-Kp isolates that harbored blaKPC–2 or blaKPC–3. Nine KPC-Kp isolates (KPC-Kp 5A, 6A, 7A, 8A, 9A, 24A, 25A, 26A, and 27A) were susceptible to ceftazidime/avibactam, two (KPC-Kp 6B and 7B) were ceftazidime/avibactam resistant and meropenem susceptible, and one (KPC-Kp 1244) was resistant to both ceftazidime/avibactam and meropenem. Sequencing of the blaKPC genes revealed mutations in KPC-Kp 6B (D179Y substitution) and 7B (novel 21 base pair deletion) that both affected the Ω-loop encoding portion of the gene. Time-kill assays showed that against ceftazidime/avibactam-susceptible KPC-Kp, ceftazidime/avibactam concentrations ≥40/7.5 mg/L caused mean 5.42 log10CFU/mL killing and suppressed regrowth. However, regrowth occurred for some KPC-Kp isolates with a ceftazidime/avibactam concentration of 20/3.75 mg/L. Against ceftazidime/avibactam-resistant and meropenem-susceptible KPC-Kp 6B and 7B, bactericidal activity and synergy was observed for ceftazidime/avibactam in combination with meropenem ≤3.125 mg/L, while meropenem concentrations ≥50 mg/L were bactericidal as monotherapy. In contrast, clinically achievable concentrations of ceftazidime/avibactam were bactericidal against KPC-Kp 1244, which was ceftazidime/avibactam-resistant and meropenem-resistant due to outer membrane porin mutations and elevated blaKPC expression. Achieving high ceftazidime/avibactam concentrations may help to suppress bacterial regrowth in the presence of ceftazidime/avibactam. The optimal treatment approach for ceftazidime/avibactam-resistant KPC-Kp likely depends on the mechanism of resistance. Additional studies are warranted to confirm these findings.

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