Radiosynthesis, quality control, biodistribution, and infection-imaging study of a new 99mTc-labeled ertapenem radiopharmaceutical
Syed Ali Raza NaqviTania JabbarMaha A. AlharbiAsma NoureenNada K. AlharbiTauqir A. SheraziAnum ShahzadiAhmed Ezzat AhmedMuhammad Shahzad AfzalMuhammad Babar Imran
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Ertapenem is a member of carbapenem antibiotics used for the treatment of moderate-to-severe intra-abdominal, urinary tract, acute pelvic, and post-surgical gynecologic infections. The antibacterial activity of ertapenem is mediated through binding to penicillin-binding proteins which results in inhibiting the cross-linking of the peptidoglycan layer of the bacterial cell wall. Therefore, ertapenem can be labeled with technetium-99m ( 99m Tc), a gamma emitter radionuclide, for the diagnosis of deep-seated bacterial infections, such as urinary tract, intra-abdominal, osteomyelitis, and post-surgical gynecologic infections. The labeling procedure was carried out by varying the reaction conditions, such as the amount of the ligand and reducing agent, pH, reaction time and temperature, and radioactivity. At optimized reaction conditions more than 93% 99m Tc–ertapenem radioconjugate was obtained. 99m Tc–ertapenem was found 90% intact in saline medium up to 6 h, while 88% intact in human blood serum up to 3 h. Biodistribution study showed target-to-non-target ratios of 2.91 ± 0.19, 2.39 ± 0.31, and 1.23 ± 0.22 in S. aureus , E. coli , and turpentine oil-infected rat models, respectively. The SPECT scintigraphy showed high uptake of 99m Tc–ertapenem in bacterial-infected abscesses, and low counts were recorded in normal and turpentine oil-inflamed tissues. In conclusion, 99m Tc–ertapenem can be a potent infection-imaging agent, which can diagnosis deep-seated bacterial infections at early stage but need further pre-clinical evaluation in variety of infection models.Keywords:
Ertapenem
Biodistribution
Carbapenem
The evolution of multidrug resistance in Acinetobacter spp. increases the risk of our best antibiotics losing their efficacy. From a clinical perspective, the carbapenem-hydrolyzing class D β-lactamase subfamily present in Acinetobacter spp. is particularly concerning because of its ability to confer resistance to carbapenems. The kinetic profiles of class D β-lactamases exhibit variability in carbapenem hydrolysis, suggesting functional differences. To better understand the structure-function relationship between the carbapenem-hydrolyzing class D β-lactamase OXA-24/40 found in Acinetobacter baumannii and carbapenem substrates, we analyzed steady-state kinetics with the carbapenem antibiotics meropenem and ertapenem and determined the structures of complexes of OXA-24/40 bound to imipenem, meropenem, doripenem, and ertapenem, as well as the expanded-spectrum cephalosporin cefotaxime, using X-ray crystallography. We show that OXA-24/40 exhibits a preference for ertapenem compared with meropenem, imipenem, and doripenem, with an increase in catalytic efficiency of up to fourfold. We suggest that superposition of the nine OXA-24/40 complexes will better inform future inhibitor design efforts by providing insight into the complicated and varying ways in which carbapenems are selected and bound by class D β-lactamases.
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Acinetobacter baumannii
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The emergence of carbapenem-resistant organisms posed considerable threat to global health while only limited treatment options are available and led to efforts to discover a novel way to treat them. To evaluate in vitro synergistic activity of meropenem plus ertapenem, a total of 203 carbapenem-resistant strains, collected from 12 provinces and municipalities in China, were examined with a dual carbapenem combination therapy. The statistical software R was used for analysis. Two hundred and one (201) of carbapenem-resistant strains mainly produced four types of carbapenemase: KPC-2 (n = 142, 69.95%), OXA-232 (n = 7, 3.45%), NDM (n = 38, 18.72%; 36 NDM-1, 1 NDM-4, 1 NDM-5), and IMP (n = 15, 7.39%; 1 IMP-26, 10 IMP-30, 4 IMP-4). Fifty-one out of two hundred and three (51/203 or 25.12%) of the examined strains showed a synergistic effect for the meropenem plus ertapenem combination throughout the checkerboard method, while only three isolates showed potential clinically relevant synergy (3/203, 1.48%). An additive effect was observed in 55/203 (27.09%) of the examined strains. Ninety-seven of the examined isolates (47.78%) showed fractional inhibitory concentration (FIC) greater or equal to 2 (indicating antagonism). The synergistic activity of meropenem plus ertapenem combination suggests this combination can be a possible way to treat the infection caused by the carbapenem-resistant organisms, especially for IMP or NDM producer with a lesser minimum inhibitory concentration (MIC) and the infected individual who was not recommended to use colistin or tigecycline.
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Both ertapenem and other carbapenems, including imipenem, meropenem, and doripenem, are recommended in the treatment of extended-spectrum-β-lactamase (ESBL)-producing Enterobacterales infection. However, whether ertapenem is as effective as other carbapenems for ESBL-producing Enterobacterales remains unclear. Therefore, this meta-analysis was conducted to compare the clinical efficacy of ertapenem versus other carbapenems in the treatment of ESBL-producing Enterobacterales infection.PubMed, Web of Science, and Cochrane Library were searched from their inception to 29 November 2022. Only studies comparing ertapenem and other carbapenems in the treatment of patients with ESBL-producing Enterobacterales infections were included.A total of six studies meeting selection criteria were identified. Overall, ertapenem was associated with a significantly lower 30-d mortality when compared with other carbapenems (10.7% [46/431] vs. 17.7% [104/586]; risk ratio [RR], 0.61; 95% CI: 0.40-0.91). The ertapenem group exhibited a significantly shorter length of hospital stay than the other carbapenem groups (mean differences, -6.02 d; 95% CI, -9.39 to -2.64). No significant differences were noted between ertapenem and other carbapenem groups in terms of rates of clinical cure or improvement (RR, 1.11; 95% CI: 0.97-1.25) and microbiological eradication (RR, 1.01; 95% CI: 0.97-1.06).Ertapenem could be as effective as other carbapenems in the treatment of patients with ESBL-producing Enterobacterales infections.
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β-Lactam antimicrobials have been widely prescribed to treat serious infections for nearly 60 years owing to their excellent efficacy, safety and tolerability profiles. Among the many different structurally dis- tinct classes of β-lactams, the carbapenem class, while sharing these general β-lactam features, is regarded as the class that is most potent and that has the widest spectrum of antimicrobial activity. At the time that the carbapenems were last reviewed in this journal, 1 imipenem and meropenem were the only carbapenems that were available in the majority of the world. Since then ertapenem (formerly MK-0826), a new long-acting, parenteral carbapenem (Figure 1), has received regulatory approval in the United States (November 2001) and the European Union (April 2002). The introduction of ertapenem should make us reconsider how we think of the carbapenems. Ertapenem is sufficiently different in some key attributes from imipenem and meropenem that we can no longer consider all available carbapenems as if they were a homogeneous class. In order to consider the appropriate role of ertapenem in the current antimicrobial armamentarium, this article reviews the key attributes of ertapenem and the other carbapenems and proposes a classification scheme for the carbapenem class; imipenem and mero- penem will be discussed first. 1,2
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OXA-232 is an OXA-48-group class D β-lactamase that hydrolyzes expanded-spectrum cephalosporins and carbapenems at low levels. Clinical strains producing OXA-232 are sometimes susceptible to carbapenems, making it difficult to identify them in the clinical microbiology laboratory. We describe the development of carbapenem resistance in sequential clinical isolates of Raoultella ornithinolytica carrying blaOXA-232 in a hospitalized patient, where the ertapenem MIC increased from 0.5 μg/ml to 512 μg/ml and the meropenem MIC increased from 0.125 μg/ml to 32 μg/ml during the course of ertapenem therapy. Whole-genome sequencing (WGS) analysis identified loss-of-function mutations in ompC and ompF in carbapenem-resistant isolates that were not present in the initial carbapenem-susceptible isolate. Complementation of a carbapenem-resistant isolate with an intact ompF gene resulted in 16- to 32-fold reductions in carbapenem MICs, whereas complementation with intact ompC resulted in a 2-fold reduction in carbapenem MICs. Additionally, blaOXA-232 expression increased 2.9-fold in a carbapenem-resistant isolate. Rapid development of high-level carbapenem resistance in initially carbapenem-susceptible OXA-232-producing R. ornithinolytica under selective pressure from carbapenem therapy highlights the diagnostic challenges in detecting Enterobacteriaceae strains producing this inefficient carbapenemase.
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This study aimed to analyse the in vitro activity of dual combinations of carbapenems against Klebsiella pneumoniae producing the main carbapenemase types. MIC values of the carbapenems, imipenem, meropenem, ertapenem and doripenem were determined alone and in dual combinations for 20 clinical K. pneumoniae isolates producing representative carbapenemases, i.e. OXA-48 (n = 6), NDM-1 (n = 4), NDM-1 + OXA-48 (n = 2) and KPC-2 (n = 8). MICs were also determined for Escherichia coli recombinant strains with or without permeability defects producing NDM-1, OXA-48 or KPC-2. In vitro synergy combination testing was performed using the microdilution and chequerboard techniques. Fractional inhibitory concentration indexes were calculated to determine whether the combinations were synergistic, indifferent or antagonistic. All carbapenemase producers were resistant to the tested carbapenems, with most isolates showing MICs of carbapenems >32 mg/L. None of the combinations was antagonistic. For KPC producers, synergistic combinations were observed with imipenem/ertapenem (5/8 isolates), imipenem/doripenem (4/8), imipenem/doripenem (4/8), meropenem/doripenem (3/8) and ertapenem/doripenem (3/8), while no synergy was observed with meropenem/ertapenem. For OXA-48 producers, synergies were observed with imipenem/ertapenem and with imipenem/meropenem for both isolates tested. Notably, combining imipenem with a non-carbapenem β-lactam (cefalotin) did not give any synergistic result. No synergy was observed for all NDM-1 and NDM-1+OXA-48 producers. Time–kill assays confirmed most of the data obtained by chequerboard testing. The data strongly support the hypothesis that dual carbapenem combinations might be effective against serine-β-lactamase producers (KPC, OXA-48). The imipenem-containing combinations appeared to be the most efficient.
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Right from the breakthrough of carbapenems since 1976, many schemes on synthesis, structure-activity relationship (SAR), and biological activities have been carried out, and several carbapenems have been developed, including parentally active carbapenems like imipenem, doripenem, biapenem, meropenem, ertapenem, panipenem, razupenem, tomopenem, and cilastatin, whereas orally active carbapenems like GV-118819, GV-104326, CS-834, L-084, DZ-2640, CL 191, 121, L-646, 591, S-4661, ER-35768, MK-826. Prodrugs of carbapenem with increased bioavailability include temopenem, tebipenem, sanfetrinem, LK-157, and CP 5484. Merck, Glaxo Welcome Research Group, Johnson & Johnson, Sankyo Group and Dai-ichi Group, and Wyeth-Ayerst Group were among the businesses that produced carbapenems. In this review Witting reaction, Mitsunobu reaction, Dieckmann reaction, palladium-catalyzed hydrogenolysis, E. coli-based cloned synthesis, as well as biosynthetic enzymes such as carbapenem synthetase (carA), carboxymethylproline synthase (carB), carbapenem synthase (carC) are included. Carbapenems are biologically mainly active in the infections like urinary tract infections, bloodstream infections, tuberculosis, intra-abdominal infections, and pathogens like anaerobes, gram-positive and gram-negative bacteria.
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