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International Journal of Antimicrobial... May 2024To analyse the impact of the most clinically relevant β-lactamases and their interplay with low outer membrane permeability on the activity of cefiderocol,...
Activity of cefiderocol and innovative β-lactam/β-lactamase inhibitor combinations against isogenic strains of Escherichia coli expressing single and double β-lactamases under high and low permeability conditions.
OBJECTIVES
To analyse the impact of the most clinically relevant β-lactamases and their interplay with low outer membrane permeability on the activity of cefiderocol, ceftazidime/avibactam, aztreonam/avibactam, cefepime/enmetazobactam, cefepime/taniborbactam, cefepime/zidebactam, imipenem/relebactam, meropenem/vaborbactam, meropenem/xeruborbactam and meropenem/nacubactam against recombinant Escherichia coli strains.
METHODS
We constructed 82 E. coli laboratory transformants expressing the main β-lactamases circulating in Enterobacterales (70 expressing single β-lactamase and 12 producing double carbapenemase) under high (E. coli TG1) and low (E. coli HB4) permeability conditions. Antimicrobial susceptibility testing was determined by reference broth microdilution.
RESULTS
Aztreonam/avibactam, cefepime/zidebactam, cefiderocol, meropenem/xeruborbactam and meropenem/nacubactam were active against all E. coli TG1 transformants. Imipenem/relebactam, meropenem/vaborbactam, cefepime/taniborbactam and cefepime/enmetazobactam were also highly active, but unstable against most of MBL-producing transformants. Combination of β-lactamases with porin deficiency (E. coli HB4) did not significantly affect the activity of aztreonam/avibactam, cefepime/zidebactam, cefiderocol or meropenem/nacubactam, but limited the effectiveness of the rest of carbapenem- and cefepime-based combinations. Double-carbapenemase production resulted in the loss of activity of most of the compounds tested, an effect particularly evident for those E. coli HB4 transformants in which MBLs were present.
CONCLUSIONS
Our findings highlight the promising activity that cefiderocol and new β-lactam/β-lactamase inhibitors have against recombinant E. coli strains expressing widespread β-lactamases, including when these are combined with low permeability or other enzymes. Aztreonam/avibactam, cefiderocol, cefepime/zidebactam and meropenem/nacubactam will help to mitigate to some extent the urgency of new compounds able to resist MBL action, although NDM enzymes represent a growing challenge against which drug development efforts are still needed.
Topics: Escherichia coli; beta-Lactamases; Cephalosporins; Microbial Sensitivity Tests; beta-Lactamase Inhibitors; Azabicyclo Compounds; Anti-Bacterial Agents; Drug Combinations; Cyclooctanes; Cefiderocol; Ceftazidime; Cefepime; Boronic Acids; Meropenem; Aztreonam; Imipenem; Bacterial Proteins; Heterocyclic Compounds, 1-Ring; Cell Membrane Permeability; Borinic Acids; Carboxylic Acids; Lactams; Triazoles
PubMed: 38513748
DOI: 10.1016/j.ijantimicag.2024.107150 -
The Journal of Antimicrobial... Sep 2023
Topics: Humans; Meropenem; Aztreonam; Klebsiella pneumoniae; Anti-Bacterial Agents; beta-Lactamases; Drug Combinations; Microbial Sensitivity Tests; Klebsiella Infections
PubMed: 37392133
DOI: 10.1093/jac/dkad206 -
International Journal of Antimicrobial... Nov 2023Acquired β-lactamase-encoding genes are typically carried by large plasmids in Gram-negative bacteria, which also commonly carry multi-copy small plasmids. This study...
Acquired β-lactamase-encoding genes are typically carried by large plasmids in Gram-negative bacteria, which also commonly carry multi-copy small plasmids. This study found that mobile genetic elements carrying antimicrobial resistance genes are capable of hijacking small plasmids. This study focused on aztreonam-avibactam (ATM-AVI) as this combination can be used to effectively counter almost all β-lactamases produced by bacteria, and has been recommended against carbapenem-resistant Enterobacterales. A clinical strain (085003) of carbapenem-resistant Escherichia coli was investigated, and mutants (085003R32 and 085003R512) able to grow under 32/4 and 512/4 mg/L of ATM-AVI were obtained as representatives of low- and high-level resistance, respectively, by induction. Comparative genomics showed that 085003R32 and 085003R512 had a single nucleotide mutation of β-lactamase gene bla, encoding a novel CMY with a Thr319Ile substitution, assigned 'CMY-2R'. Cloning and enzyme kinetics were used to verify that CMY-2R conferred ATM-AVI resistance by compromising binding of AVI and subsequent protection of ATM. Mechanisms for the discrepant resistance between 085003R32 and 085003R512 were investigated. Three tandem copies of bla were identified on a self-transmissible IncP1 plasmid of 085003R32 due to IS1294 misrecognizing its end terIS and rolling-circle replication. 085003R512 had only a single copy of bla on the IncP1 plasmid, but possessed anther bla on an already present 4-kb small plasmid. IS1294-mediated mobilization on to this multi-copy small plasmid increased the copy number of bla significantly, rendering higher resistance. This study shows that bacteria can employ multiple approaches to accommodate selection pressures imposed by exposure to varied concentrations of antimicrobial agents.
Topics: Aztreonam; Ceftazidime; Azabicyclo Compounds; Drug Combinations; Plasmids; Escherichia coli; beta-Lactamases; Carbapenems; Anti-Bacterial Agents; Microbial Sensitivity Tests
PubMed: 37769749
DOI: 10.1016/j.ijantimicag.2023.106985 -
Expert Opinion on Therapeutic Patents 2023β-Lactams, which include monobactams, remain the most important class of antibiotics worldwide. Aztreonam, the only monobactam in clinical use, has remarkable activity... (Review)
Review
INTRODUCTION
β-Lactams, which include monobactams, remain the most important class of antibiotics worldwide. Aztreonam, the only monobactam in clinical use, has remarkable activity against many Gram-negative bacteria, but limited activity against some of the most problematic multidrug-resistant (MDR) pathogens, such as MDR and co-expressing extended-spectrum- and metallo-β-lactamases, which can inactivate aztreonam by hydrolysis.
AREAS COVERED
Structurally novel siderophore-conjugated aztreonam derivatives with improved antibacterial properties against several high-priority pathogens are claimed. This invention reports that sidechain extension of aztreonam is tolerated; the coupling of its aminothiazoloxime carboxylic acid part with a siderophore mimetic significantly improved the antibacterial activity against several problematic strains, including MDR isolates with carbapenemase/cephalosporinase activity.
EXPERT OPINION
Finding new strategies to tackle bacterial resistance to β-lactam antibiotics is critical. Considering that β lactams are validated and safe drugs, this research may stimulate the field to develop new ideas in the arena of antimicrobial drug discovery, particularly with respect to siderophore mimetics.
Topics: Humans; Monobactams; Aztreonam; Siderophores; Patents as Topic; Anti-Bacterial Agents; beta-Lactams; beta-Lactamases; Microbial Sensitivity Tests
PubMed: 37902072
DOI: 10.1080/13543776.2023.2262135 -
Antimicrobial Agents and Chemotherapy Dec 2023is the most prevalent cystic fibrosis (CF) pathogen. Several phenotypes are associated with worsened CF clinical outcomes including methicillin-resistance and...
is the most prevalent cystic fibrosis (CF) pathogen. Several phenotypes are associated with worsened CF clinical outcomes including methicillin-resistance and small-colony-variants. The inoculum effect (IE) is characterized by reduced β-lactam susceptibility when assessed at high inoculum. The IE associates with worse outcomes in bacteremia and other high-density infections, and may therefore be relevant to CF. The prevalence of IE amongst a CF cohort (age ≥18 years), followed from 2013 to 2016, was investigated. Yearly methicillin-sensitive (MSSA) isolates were screened at standard (5 × 10 CFU/mL) and high (5 × 10 CFU/mL) inoculum against narrow-spectrum anti-Staphylococcal β-lactams and those with anti-pseudomonal activity common to CF. A ≥ 4-fold increase in minimum inhibitory concentration between standard and high inoculum defined IE. Isolates underwent sequencing and genotyping and were compared against published genomes. Fifty-six percent (99/177) of individuals had MSSA infection. MSSA was observed at ≥10 CFU/mL in 44.8% of entry sputum samples. The prevalence of the IE was 25.0%-cefazolin; 13.5%-cloxacillin; 0%-meropenem; 1.0%-cefepime; 5.2%-ceftazidime; and 34.4%-piperacillin-tazobactam amongst baseline MSSA isolates assessed. A associated with cefazolin IE ( = 0.0011), whereas C associated with piperacillin-tazobactam IE ( < 0.0001). Baseline demographics did not reveal specific risk factors for IE-associated infections, nor were long-term outcomes different. Herein, we observed the IE in CF-derived MSSA disproportionally for cefazolin and piperacillin-tazobactam and this phenotype strongly associated with underlying genotype. The confirmation of CF being a high density infection, and the identification of high prevalence of MSSA with IE in CF supports the need for prospective pulmonary exacerbation treatment studies to understand the impact of this phenotype.
Topics: Adult; Humans; Adolescent; Methicillin; Cefazolin; Staphylococcus aureus; Anti-Bacterial Agents; Prospective Studies; Cystic Fibrosis; Staphylococcal Infections; Monobactams; Piperacillin, Tazobactam Drug Combination; Ceftazidime; beta Lactam Antibiotics; Microbial Sensitivity Tests
PubMed: 37966229
DOI: 10.1128/aac.00136-23 -
International Journal of Antimicrobial... Mar 2024Enterobacterales with carbapenemase-independent resistance to carbapenems are sometimes selected during therapy and, on rare occasions, cause outbreaks. Most have...
Enterobacterales with carbapenemase-independent resistance to carbapenems are sometimes selected during therapy and, on rare occasions, cause outbreaks. Most have extended-spectrum or AmpC β-lactamases, together with changes to permeability or penicillin-binding proteins (PBPs). Newer β-lactam-β-lactamase inhibitor combinations may present useful options for infections due to these organisms. Accordingly, Clinical and Laboratory Standards Institute/European Committee on Antimicrobial Susceptibility Testing broth-microdilution was used to measure the minimum inhibitory concentrations (MICs) of ceftazidime/avibactam and aztreonam/avibactam for 51 carbapenemase-negative Enterobacterales with resistance or reduced susceptibility to carbapenems: genomic sequencing of the least-susceptible organisms was also undertaken. MICs of the two avibactam combinations cross-correlated closely, but with fewer MICs (2/51 vs. 10/51) exceeding 8+4 mg/L in the case of ceftazidime/avibactam. Raised MICs for Escherichia coli were associated with PBP3 inserts together with CMY-42 β-lactamase; correlates among Enterobacter cloacae complex isolates remain elusive, with AmpC and PBP3 sequences found to be species specific. In the case of Klebsiella spp., no MICs exceeding 2 mg/L were seen for either combination. It appears that these avibactam combinations have potential against Enterobacterales with carbapenemase-independent carbapenem resistance or reduced susceptibility, with ceftazidime/avibactam being more reliably active than aztreonam/avibactam.
Topics: Aztreonam; Ceftazidime; beta-Lactamases; Carbapenems; Escherichia coli; Bacterial Proteins; Azabicyclo Compounds
PubMed: 38176458
DOI: 10.1016/j.ijantimicag.2023.107081 -
Drug Development Research Nov 2023Drug addiction as a problem for the health of the individual and the society is the result of a complex process in which there is an interaction between brain nuclei and... (Review)
Review
Drug addiction as a problem for the health of the individual and the society is the result of a complex process in which there is an interaction between brain nuclei and neurotransmitters (such as glutamate). β-lactam antibiotics, due to their enhancing properties on the glutamate transporter glutamate transporter-1, can affect and counteract the addictive mechanisms of drugs through the regulation of extracellular glutamate. Since glutamate is a key neurotransmitter in the development of drug addiction, it seems that β-lactams can be considered as a promising treatment for addiction. However, more research in this field is necessary to identify other mechanisms involved in their effectiveness. This article is a review of the studies conducted on the effect of β-lactam administration in preventing the development of drug addiction, as well as their possible cellular and molecular mechanisms. This review suggests the clinical use of β-lactam antibiotics that have weak antimicrobial properties (such as clavulanic acid) in the treatment of drug dependence.
Topics: Humans; beta-Lactams; Monobactams; Substance-Related Disorders; Anti-Bacterial Agents; Amino Acid Transport System X-AG; Glutamates
PubMed: 37602907
DOI: 10.1002/ddr.22110 -
Microbiology Spectrum Jun 2024This study aimed to assess the efficacy of ceftazidime-avibactam (CZA) in combination with various antimicrobial agents against carbapenem-resistant (CRKP). We...
UNLABELLED
This study aimed to assess the efficacy of ceftazidime-avibactam (CZA) in combination with various antimicrobial agents against carbapenem-resistant (CRKP). We selected 59 clinical CRKP isolates containing distinct drug resistance mechanisms. The minimum inhibitory concentrations (MICs) of meropenem (MEM), colistin (COL), eravacycline (ERA), amikacin (AK), fosfomycin (FOS), and aztreonam (ATM), both individually and in combination with CZA, were tested using the checkerboard method. The interactions of antimicrobial agent combinations were assessed by fractional inhibitory concentration index (FICI) and susceptible breakpoint index (SBPI). The time-kill curve assay was employed to dynamically evaluate the effects of these drugs alone and in combination format. In the checkerboard assay, the combination of CZA+MEM showed the highest level of synergistic effect against both KPC-producing and carbapenemase-non-producing isolates, with synergy rates of 91.3% and 100%, respectively. Following closely was the combination of FOS+CZA . For metallo-beta-lactamases (MBLs) producing strains, ATM+CZA displayed complete synergy, while the combination of MEM+CZA showed a synergy rate of only 57.14% for NDM-producing strains and 91.67% for IMP-producing strains. In the time-kill assay, MEM+CZA also demonstrated significant synergistic effects against the two KPC-2-producing isolates (Y070 and L70), the two carbapenemase-non-producing isolates (Y083 and L093), and the NDM-1-producing strain L13, with reductions in log CFU/mL exceeding 10 compared to the control. Against the IMP-producing strain Y047, ATM+CZA exhibited the highest synergistic effect, resulting in a log CFU/mL reduction of 10.43 compared to the control. The combination of CZA and MEM exhibited good synergistic effects against KPC-producing and non-enzyme-producing strains, followed by the FOS+CZA combination. Among MBL-producing strains, ATM+CZA demonstrated the most pronounced synergistic effect. However, the combinations of CZA with ERA, AK, and COL show irrelevant effects against the tested clinical isolates.
IMPORTANCE
Our study confirmed the efficacy of the combination CZA+MEM against KPC-producing and non-carbapenemase-producing strains. For metalloenzyme-producing strains, CZA+ATM demonstrated the most significant synergy. Additionally, CZA exhibited a notable synergy effect when combined with FOS. These combination therapies present promising new options for the treatment of CRKP infection.
Topics: Azabicyclo Compounds; Klebsiella pneumoniae; Ceftazidime; Drug Combinations; Microbial Sensitivity Tests; Humans; Anti-Bacterial Agents; Klebsiella Infections; Carbapenem-Resistant Enterobacteriaceae; Drug Synergism; beta-Lactamases; Carbapenems; Drug Resistance, Multiple, Bacterial; Bacterial Proteins; Fosfomycin; Aztreonam
PubMed: 38712934
DOI: 10.1128/spectrum.00107-24 -
Nature Communications Jul 2023Penicillin-binding proteins (PBPs) are essential for the formation of the bacterial cell wall. They are also the targets of β-lactam antibiotics. In Enterococcus...
Penicillin-binding proteins (PBPs) are essential for the formation of the bacterial cell wall. They are also the targets of β-lactam antibiotics. In Enterococcus faecium, high levels of resistance to β-lactams are associated with the expression of PBP5, with higher levels of resistance associated with distinct PBP5 variants. To define the molecular mechanism of PBP5-mediated resistance we leveraged biomolecular NMR spectroscopy of PBP5 - due to its size (>70 kDa) a challenging NMR target. Our data show that resistant PBP5 variants show significantly increased dynamics either alone or upon formation of the acyl-enzyme inhibitor complex. Furthermore, these variants also exhibit increased acyl-enzyme hydrolysis. Thus, reducing sidechain bulkiness and expanding surface loops results in increased dynamics that facilitates acyl-enzyme hydrolysis and, via increased β-lactam antibiotic turnover, facilitates β-lactam resistance. Together, these data provide the molecular basis of resistance of clinical E. faecium PBP5 variants, results that are likely applicable to the PBP family.
Topics: Penicillin-Binding Proteins; Anti-Bacterial Agents; Bacterial Proteins; beta-Lactam Resistance; Monobactams; beta-Lactams; Microbial Sensitivity Tests; Hexosyltransferases
PubMed: 37460557
DOI: 10.1038/s41467-023-39966-5 -
International Journal of Antimicrobial... Nov 2023Combination therapy can enhance the activity of available antibiotics against multidrug-resistant Gram-negative bacteria. This study assessed the effects of polymyxin B...
BACKGROUND
Combination therapy can enhance the activity of available antibiotics against multidrug-resistant Gram-negative bacteria. This study assessed the effects of polymyxin B combinations against carbapenemase-producing Klebsiella pneumoniae (K. pneumoniae).
METHODS
Twenty clinical K. pneumoniae strains producing NDM-1 (n = 8), OXA-48-like (n = 10), or both NDM-1 and OXA-48-like (n = 2) carbapenemases were used. Whole-genome sequencing was applied to detect resistance genes (e.g. encoding antibiotic-degrading enzymes) and sequence alterations influencing permeability or efflux. The activity of polymyxin B in combination with aztreonam, fosfomycin, meropenem, minocycline, or rifampicin was investigated in 24-hour time-lapse microscopy experiments. Endpoint samples were spotted on plates with and without polymyxin B at 4 x MIC to assess resistance development. Finally, associations between synergy and bacterial genetic traits were explored.
RESULTS
Synergistic and bactericidal effects were observed with polymyxin B in combination with all other antibiotics: aztreonam (11 of 20 strains), fosfomycin (16 of 20), meropenem (10 of 20), minocycline (18 of 20), and rifampicin (15 of 20). Synergy was found with polymyxin B in combination with fosfomycin, minocycline, or rifampicin against all nine polymyxin-resistant strains. Wildtype mgrB was associated with polymyxin B and aztreonam synergy (P = 0.0499). An absence of arr-2 and arr-3 was associated with synergy of polymyxin B and rifampicin (P = 0.0260). Emergence of populations with reduced polymyxin B susceptibility was most frequently observed with aztreonam and meropenem.
CONCLUSION
Combinations of polymyxin B and minocycline or rifampicin were most active against the tested NDM-1 and OXA-48-like-producing K. pneumoniae. Biologically plausible genotype-phenotype associations were found. Such information might accelerate the search for promising combinations and guide individualised treatment.
Topics: Polymyxin B; Aztreonam; Meropenem; Klebsiella pneumoniae; Minocycline; Fosfomycin; Rifampin; Drug Synergism; Anti-Bacterial Agents; beta-Lactamases; Microbial Sensitivity Tests
PubMed: 37716575
DOI: 10.1016/j.ijantimicag.2023.106967