Meropenem Research Articles

Critical resistance to carbapenem and aminoglycosides in Pseudomonas aeruginosa: spread of blaNDM/16S methylase armA harboring isolates with intrinsic resistance mechanisms in Kerman, Iran

BackgroundCarbapenem-resistant Pseudomonas aeruginosa (CRPA) is one of the main Gram-negative bacterium causes of infections in hospital settings, and the spread of them is a significant challenge to public health.MethodsA total of 30 non-duplicate isolates of CRPA were collected. Antibacterial susceptibility of isolates to antibiotic agents, AmpC β-lactamase production, and biofilm formation were determined. Minimum biofilm inhibitory concentrations (MBIC) of isolates to cefepime (FEP), imipenem (IPM), ceftazidime (CAZ), and meropenem (MEM) were evaluated with/without cloxacillin (CLX). The carbapenemase and 16 S rRNA methylase genes were identified by PCR, and the transcription levels of oprD, ampC, and mexA genes were determined by quantitative real-time PCR (qPCR). ERIC-PCR was used to detect genetic relationships among isolates.ResultsAll isolates were multidrug resistant (MDR) and strong biofilm producers. The resistance genes including blaNDM, blaIMP, blaVIM, blaSIM, blaGES, and armA were detected in 21 (70%), 6 (20%), 3 (10%), 2 (6.6%), 1 (3.3%), and 17 (56.6%) of the isolates, respectively. CLX at 500 and 1000 µg/mL significantly reduced the level of MIC to MEM, IPM, CAZ, and FEP, also at 2000 µg/mL significantly reduced the level of MBIC to MEM, IPM, CAZ, and FEP. In all isolates, the transcription levels of oprD were significantly downregulated as well as significantly increased for ampC and mexA. ERIC-PCR typing results divided 30 isolates into four clusters A to D.ConclusionIn this study, we reported the spread of different clones of CRPA harboring co-existence of various carbapenemase genes with armA 16 S rRNA methylase for the first time in Kerman, Iran. Also, our isolates had several mechanisms of resistance to carbapenems as well as ability biofilm formation along with resistance to aminoglycosides, the further spread of which could cause serious challenges in our hospital settings. Therefore, serious monitoring is necessary to reduce their prevalence.

Detection of carbapenem-resistant gram-negative bacilli in Japan using the fully automated bacterial testing device RAISUS S4

ObjectiveWe investigated a rapid detection method for carbapenemase-producing gram-negative bacilli (CP-GNR) using meropenem (MEPM) to assess the efficiency of the antimicrobial susceptibility testing. MethodsWe used the function that can monitor the growth curve with the resistant bacteria monitoring function (RAISUS S4). Rapid detection of CP-GNR was performed using RAISUS S4 in two types of antimicrobial susceptibility testing, the RAISUS 18-hour method (18-h method) and RAISUS rapid method (rapid method) for Enterobacterales (F-GNR) and non-fermenting Gram-negative bacilli (NF-GNR). ResultsWhen F-GNR were based on MEPM MIC ≥ 0.25 μg/mL, CP-GNR were detected with a sensitivity of 100% (58/58) for the 18-h method and 98.3% (57/58) for the rapid method; the shortest detection times were 5.3 and 4.0 h, respectively. When NF-GNR were based on MEPM MIC > 8 μg/mL, it was possible to detect CP-GNR with 100% sensitivity (58/58) in both methods. Furthermore, in the analysis using the 18-h method for monitoring resistant bacteria, when ≥ 2 µg/mL was used as the screening concentration for F-GNR, approximately 50% of the resistant genotypes, NDM, GES, and KPC, were detected in approximately 7 h. However, detecting the IMP and VIM took 11–12 h. ConclusionsThe 18-h and rapid methods with RAISUS S4 were highly correlated with the results of the microdilution method of CLSI, and CP-GNR detection was rapid using a function that can monitor the growth curve with RAISUS S4.

Colistin, doxycycline and Labetalol-meropenem combination are the most active against XDR-Carbapenem-resistant Acinetobacter baumannii: Role of a novel transferrable plasmid conferring carbapenem resistance

This study aimed to evaluate the antimicrobial susceptibility and combination of a beta-blocker, labetalol (LAB) and meropenem (MEM) on Carbapenem-resistant (CR) A. baumannii clinical isolates. A total of 43 CR- A. baumannii were isolated of which 37 (86.6 %) and 28 (65 %) exhibited MDR and XDR phenotypes, respectively. Colistin and doxycycline still retain their activities in 93.1 % and 72.1 % of the isolates, respectively. Combining MEM with LAB at 0.25 mg /mL, decreased MIC values in 91.4 % (32/35) however, at 0.5 mg /mL, it decreased MIC value and restored susceptibility to MEM in 100 % and 91.4 % of the tested isolates, respectively. A novel transferable plasmid pAcbGIM3 harboring aph-3′, blaoxa-58,blaGIM3 and blaCTX-M3 and eight mobile genetic elements were successfully isolated from a pan-drug resistant (PDR) isolate. In conclusion, LAB-MEM is a promising combination and should be clinically examined. This is the first report of a transmissible plasmid harboring blaGIM3 gene in Egypt.

Reversion of KPC-114 to KPC-2 in ceftazidime-avibactam- resistant/meropenem-susceptible Klebsiella pneumoniae ST11 is related to low mutation rates.

Klebsiella pneumoniae strains that produce Klebsiella pneumoniae Carbapenemase (KPC) variants displaying resistance to ceftazidime-avibactam (CZA) often remain susceptible to meropenem (MEM), suggesting a potential therapeutic use of this carbapenem antibiotic. However, in vitro studies indicate that these sorts of strains can mutate becoming MEM-resistant, raising concerns about the effectiveness of carbapenems as treatment option. We have studied mutation rates occurring from the reversion of MEM-susceptible KPC-114 to MEM-resistant KPC-2, in CZA-resistant K. pneumoniae belonging to ST11. Two-step fluctuation assays (FAs) were conducted. In brief, initial cultures of KPC-114-producing K. pneumoniae showing 1 µg/mL MEM MIC were spread on Mueller-Hinton agar plates containing 2-8 µg/mL MEM. A second step of FA, at 4-16 µg/mL MEM was performed from a mutant colony obtained at 2 µg/mL MEM. Mutation rates were calculated using maximum likelihood estimation. Parental and mutant strains were sequenced by Illumina NextSeq, and mutations were predicted by variant-calling analysis. At 8 µg/mL MEM, mutants derived from parental CZA-resistant (MIC ≥ 64 µg/mL)/MEM-susceptible (MIC = 1 µg/mL) KPC-114-positive K. pneumoniae exhibited an accumulative mutation rate of 3.05 × 10-19 mutations/cell/generation, whereas at 16 µg/mL MEM an accumulative mutation rate of 1.33 × 10-19 mutations/cell/generation resulted in the reversion of KPC-114 (S181_P182 deletion) to KPC-2. These findings highlight that the reversion of MEM-susceptible KPC-114 to MEM-resistant KPC-2, in CZA-resistant K. pneumoniae ST11 is related to low mutation rates suggesting a low risk of therapeutic failure. In vivo investigations are necessary to confirm the clinical potential of MEM against CZA-resistant KPC variants.IMPORTANCEThe emergence of ceftazidime-avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae is a major concern due to the limited therapeutic options. Strikingly, KPC mutations mediating CZA resistance are generally associated with meropenem susceptibility, suggesting a potential therapeutic use of this carbapenem antibiotic. However, the reversion of meropenem-susceptible to meropenem-resistant could be expected. Therefore, knowing the mutation rate related to this genetic event is essential to estimate the potential use of meropenem against CZA-resistant KPC-producing K. pneumoniae. In this study, we demonstrate, in vitro, that under high concentrations of meropenem, reversion of KPC-114 to KPC-2 in CZA-resistant/meropenem-susceptible K. pneumoniae belonging to the global high-risk ST11 is related to low mutation rates.

The interaction of the azetidine thiazole side chain with the active site loop (ASL) 3 drives the evolution of IMP metallo-β-lactamase against tebipenem.

Imipenemase (IMP) metallo-β-lactamases (MBLs) hydrolyze almost all available β-lactams including carbapenems and are not inhibited by any commercially available β-lactamase inhibitor. Tebipenem (TP) pivoxil is the first orally available carbapenem and possesses a unique bicyclic azetidine thiazole moiety located at the R2 position. TP has potent in vitro activity against Enterobacterales producing extended-spectrum and/or AmpC β-lactamases. Thus far, the activity of TP against IMP-producing strains is understudied. To address this knowledge gap, we explored the structure activity relationships of IMP MBLs by investigating whether IMP-6, IMP-10, IMP-25, and IMP-78 [MBLs with expanded hydrolytic activity against meropenem (MEM)] would demonstrate enhanced activity against TP. Most of the Escherichia coli DH10B strains expressing IMP-1 variants displayed a ≥twofold MIC difference between TP and MEM, while those expressing VIM or NDM variants demonstrated comparable MICs. Catalytic efficiency (kcat/KM) values for the TP hydrolysis by IMP-1, IMP-6, IMP-10, IMP-25, and IMP-78 were significantly lower than those obtained for MEM. Molecular dynamic simulations reveal that V67F and S262G substitutions (found in IMP-78) reposition active site loop 3, ASL-3, to better accommodate the bicyclic azetidine thiazole side chain, allowing microbiological/catalytic activity to approach that of comparison MBLs used in this study. These findings suggest that modifying the R2 side chain of carbapenems can significantly impact hydrolytic stability. Furthermore, changes in conformational dynamics due to single amino acid substitutions should be used to inform drug design of novel carbapenems.

Visualized and pH-responsive hydrogel antibacterial coating for ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is a common healthcare-acquired infection often arising during artificial ventilation using endotracheal intubation (ETT), which offers a platform for bacterial colonization and biofilm development. In particular, the effects of prolonged COVID-19 on the respiratory system. Herein, we developed an antimicrobial coating (FK-MEM@CMCO-CS) capable of visualizing pH changes based on bacterial infection and releasing meropenem (MEM) and FK13-a1 in a controlled manner. Using a simple dip-coating process with controlled loading, chitosan was cross-linked with sodium carboxymethyl cellulose oxidation (CMCO) and coated onto PVC-based ETT to form a hydrogel coating. Subsequently, the coated segments were immersed in an indicator solution containing bromothymol blue (BTB), MEM, and FK13-a1 to fabricate the FK-MEM@CMCO-CS coating. In vitro studies have shown that MEM and FK13-a1 can be released from coatings in a pH-responsive manner. Moreover, anti-biofilm and antibacterial adhesion results showed that FK-MEM@CMCO-CS coating significantly inhibited biofilm formation and prevented their colonization of the coating surface. In the VAP rat model, the coating inhibited bacterial growth, reduced lung inflammation, and had good biocompatibility. The coating can be applied to the entire ETT and has the potential for industrial production.

The impact of meropenem shortage and post-prescription review and feedback on broad-spectrum antimicrobial use: An interrupted time-series analysis

Meropenem (MEPM) holds significance in treating severe infections and drug-resistant bacteria. There are concerns that antimicrobial shortages may lead to the use of alternative antimicrobials that are less effective and safer. We have responded to the MEPM shortage with post-prescription monitoring and feedback (PPRF) with no restrictions on MEPM initiation. We aimed to assess the impact of the MEPM shortage and the PPRF on broad-spectrum antimicrobial use and mortality. This retrospective study was conducted in a single hospital in Japan. The period from October 2021 to August 2022 was defined as the period before the MEPM shortage, and the period from September 2022 to March 2023 was defined as the period during the MEPM shortage. To support the appropriate use of antimicrobials during MEPM shortages, the antimicrobial stewardship team (AST) developed a list of alternatives to MEPM. An interrupted time series analysis was used to assess changes in use and mortality among patients receiving broad-spectrum antimicrobials over the study period. The shortage of MEPM and PPRF temporarily increased the use of alternative cefepime; however, the subsequent change in days of therapy and days of coverage of broad-spectrum antimicrobials suggests a decrease in the use of these antimicrobials. Despite these shifts, the mortality rates remained stable, suggesting that the response to the shortage did not adversely affect treatment outcomes. In the context of antimicrobial shortages, AST support plays an important role in enabling physicians to make optimal use of antimicrobials.

Direct prediction of antimicrobial resistance in Pseudomonas aeruginosa by metagenomic next-generation sequencing.

Pseudomonas aeruginosa has strong drug resistance and can tolerate a variety of antibiotics, which is a major problem in the management of antibiotic-resistant infections. Direct prediction of multi-drug resistance (MDR) resistance phenotypes of P. aeruginosa isolates and clinical samples by genotype is helpful for timely antibiotic treatment. In the study, whole genome sequencing (WGS) data of 494 P. aeruginosa isolates were used to screen key anti-microbial resistance (AMR)-associated genes related to imipenem (IPM), meropenem (MEM), piperacillin/tazobactam (TZP), and levofloxacin (LVFX) resistance in P. aeruginosa by comparing genes with copy number differences between resistance and sensitive strains. Subsequently, for the direct prediction of the resistance of P. aeruginosa to four antibiotics by the AMR-associated features screened, we collected 74 P. aeruginosa positive sputum samples to sequence by metagenomics next-generation sequencing (mNGS), of which 1 sample with low quality was eliminated. Then, we constructed the resistance prediction model. We identified 93, 88, 80, 140 AMR-associated features for IPM, MEM, TZP, and LVFX resistance in P. aeruginosa. The relative abundance of AMR-associated genes was obtained by matching mNGS and WGS data. The top 20 features with importance degree for IPM, MEM, TZP, and LVFX resistance were used to model, respectively. Then, we used the random forest algorithm to construct resistance prediction models of P. aeruginosa, in which the areas under the curves of the IPM, MEM, TZP, and LVFX resistance prediction models were all greater than 0.8, suggesting these resistance prediction models had good performance. In summary, mNGS can predict the resistance of P. aeruginosa by directly detecting AMR-associated genes, which provides a reference for rapid clinical detection of drug resistance of pathogenic bacteria.

In vitro and in vivo activities of KSP-1007, a broad-spectrum inhibitor of serine- and metallo-β-lactamases, in combination with meropenem against carbapenem-resistant Gram-negative bacteria.

KSP-1007 is a novel bicyclic boronate-based broad-spectrum β-lactamase inhibitor and is being developed in combination with meropenem (MEM) for the treatment of infections caused by carbapenem-resistant Gram-negative bacteria, a global health concern, and here, we describe its characteristics. KSP-1007 exhibited low apparent inhibition constant (Ki app) values against all classes of β-lactamase, including imipenemase types and oxacillinase types from Acinetobacter baumannii. Against 207 Enterobacterales and 55 A. baumannii, including carbapenemase producers, KSP-1007 at fixed concentrations of 4, 8, and 16 µg/mL dose-dependently potentiated the in vitro activity of MEM in broth microdilution MIC testing. The MIC90 of MEM/KSP-1007 at 8 µg/mL against Enterobacterales was lower than those of MEM/vaborbactam, ceftazidime/avibactam, imipenem/relebactam, and colistin and similar to those of aztreonam/avibactam, cefiderocol, and tigecycline. The in vitro activity of MEM/KSP-1007 at ≥4 µg/mL against Enterobacterales harboring metallo-β-lactamase was superior to that of cefepime/taniborbactam. MEM/KSP-1007 showed excellent activity against Escherichia coli with PBP3 mutations and New Delhi metallo-β-lactamase compared to aztreonam/avibactam, cefepime/taniborbactam, and cefiderocol. MEM/KSP-1007 at 8 µg/mL showed greater efficacy against A. baumannii than these comparators except for cefiderocol, tigecycline, and colistin. A 2-fold reduction in MEM MIC against 96 Pseudomonas aeruginosa was observed in combination with KSP-1007. MEM/KSP-1007 demonstrated bactericidal activity against carbapenemase-producing Enterobacterales, A. baumannii, and P. aeruginosa based on minimum bactericidal concentration/MIC ratios of ≤4. KSP-1007 enhanced the in vivo activity of MEM against carbapenemase-producing Enterobacterales, A. baumannii, and P. aeruginosa in murine systemic, complicated urinary tract, and thigh infection models. Collectively, MEM/KSP-1007 has a good profile for treating carbapenem-resistant Gram-negative bacterial infections.

Antimicrobial combination effects against multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa strains: A cross-sectional study.

Emergence of multidrug resistance in non-fermenting Gram-negative bacilli is a threat to public health. Combination therapy is a strategy for the treatment of antibiotic-resistant infections. In this cross-sectional study, a total of 63 nonduplicate clinical isolates of Acinetobacter baumannii and Pseudomonas aeruginosawere collected from various specimens. Identification of bacterial isolates was performed by phenotypic and molecular tests. Antibiotic susceptibility patterns and detection of β-lactamase genes were determined using the broth microdilution and polymerase chain reaction (PCR) techniques, respectively. Then, the combined effects analysis was determined by the checkerboard method. Based on the status of resistance to carbapenems (imipenem and meropenem), 25 isolates of each genus were selected for further investigation. For A. baumannii, bla OXA-23, bla OXA-58, and bla OXA-48 genes were positive in 21 (84%), 17 (68%), and 11 (44%) of isolates, respectively. In P. aeruginosa isolates, bla VIM was the most common gene (44%) and other genes including bla IMP, bla NDM, and bla OXA-23 were found in nine (36%), six (24%), and three (12%) isolates, respectively. Meropenem (MER)-tigecycline (TIG) had a significant synergistic effect against 20 (80%) A. baumannii (pvalue < 0.001). This combination was also efficient against 5 (20%) P. aeruginosa isolates. Moreover, the other combination, tigecycline-amikacin (TIG-AMK) was effective against 10 (40%) A. baumannii isolates. The combination of colistin (COL) and MER showed a significant synergistic effect against 21 (84%) A. baumannii (pvalue < 0.001) and 17 (68%) P. aeruginosa isolates (pvalue < 0.001). The MER-TIG and COL-MER combinations are promising options against resistant bacteria. Our study could be helpful for the development of a new treatment recommendation.

3-O-Substituted Quercetin: an Antibiotic-Potentiating Agent against Multidrug-Resistant Gram-Negative Enterobacteriaceae through Simultaneous Inhibition of Efflux Pump and Broad-Spectrum Carbapenemases.

The discovery of safe and efficient inhibitors against efflux pumps as well as metallo-β-lactamases (MBL) is one of the main challenges in the development of multidrug-resistant (MDR) reversal agents which can be utilized in the treatment of carbapenem-resistant Gram-negative bacteria. In this study, we have identified that introduction of an ethylene-linked sterically demanding group at the 3-OH position of the previously reported MDR reversal agent di-F-Q endows the resulting compounds with hereto unknown multitarget inhibitory activity against both efflux pumps and broad-spectrum β-lactamases including difficult-to-inhibit MBLs. A molecular docking study of the multitarget inhibitors against efflux pump, as well as various classes of β-lactamases, revealed that the 3-O-alkyl substituents occupy the novel binding sites in efflux pumps as well as carbapenemases. Not surprisingly, the multitarget inhibitors rescued the antibiotic activity of a carbapenem antibiotic, meropenem (MEM), in NDM-1 (New Delhi Metallo-β-lactamase-1)-producing carbapenem-resistant Enterobacteriaceae (CRE), and they reduced MICs of MEM more than four-fold (synergistic effect) in 8-9 out of 14 clinical strains. The antibiotic-potentiating activity of the multitarget inhibitors was also demonstrated in CRE-infected mouse model. Taken together, these results suggest that combining inhibitory activity against two critical targets in MDR Gram-negative bacteria, efflux pumps, and β-lactamases, in one molecule is possible, and the multitarget inhibitors may provide new avenues for the discovery of safe and efficient MDR reversal agents.

Reliability of a Screening Method Using Antibiotic Disks to Detect Carbapenemases in Glucose-Nonfermenting Gram-Negative Microorganisms From Clinical Samples of a Regional Hospital in Southeastern Spain.

Infections by glucose-nonfermenting gram-negative bacilli (NFGNB) pose a major public health problem due to multiresistance to beta-lactam antibiotics, especially plasmid-borne carbapenemases. Their detection by microbiology laboratories is challenging, and there is a need for easy-to-use and reliable diagnostic techniques. Our objective was to evaluate an in-house screening method to presumptively detect carbapenemases in NFGNB in a simple and clinically useful manner. The study included 175 NFGNB isolates from urinary, respiratory, and rectal samples. In a triple assay, isolates were incubated at 37°C for 24 h on three solid-culture media: MacConkey II Agar, 5% Sheep Blood Columbia Agar and Mueller Hinton II Agar; meropenem (MEM) and cefepime (FEP) disks were employed for screening. Studies were then performed on the inhibition halo diameter, scanning effects, and the appearance of mutant colonies, which were compared with those observed using the colorimetric Neo-Rapid CARB Kit and immunochromatography (NG5-Test Carba and K-Set for OXA-23). Receiver operating characteristic curves were constructed for these data. Carbapenemases were expressed by 79/175 (45.1%): 19 Pseudomonas aeruginosa and 60 Acinetobacter baumannii. Optimal inhibition halo diameter cutoffs to detect this resistance on 5% sheep blood agar were as follows: 6 mm (MEM) and 6.5 mm (FEP) for P. aeruginosa (in the absence of scanning effects and mutations) and 10.5 mm (MEM) and 16 mm (FEP) for A. baumannii (even in the presence of scanning effects). The combined utilization of MEM and FEP antibiotic disks in 5% sheep blood agar, measuring their inhibition haloes, offers an effective method to predict the presence of carbapenemases as resistance mechanism in P. aeruginosa and A. baumannii.

Effect modification of dosing strategy (AUC or trough) on AKI associated with vancomycin in combination with piperacillin/tazobactam or cefepime and meropenem.

Piperacillin-tazobactam (TZP), cefepime (FEP), or meropenem (MEM) and vancomycin (VAN) are commonly used in combination for sepsis. Studies have shown an increased risk of acute kidney injury (AKI) with TZP and VAN compared to FEP or MEM. VAN guidelines recommend area under the curve (AUC) monitoring over trough (Tr) to minimize the risk of AKI. We investigated the association of AKI and MAKE-30 with the two VAN monitoring strategies when used in combination with TZP or FEP/MEM. Adult patients between 2015 and 2019 with VAN > 72 hours were included. Patients with AKI prior to or within 48 hours of VAN or baseline CrCl of ≤30 mL/min were excluded. Four cohorts were defined: FEP/MEM/Tr, FEP/MEM/AUC, TZP/Tr, and TZP/AUC. A Cox Proportional Hazard Model was used to model AKI as a function of the incidence rate of at-risk days, testing monitoring strategy as a treatment effect modification. Multivariable logistic regression was used to model MAKE-30. Overall incidence of AKI was 18.6%; FEP/MEM/Tr = 115 (14.6%), FEP/MEM/AUC = 52 (14.9%), TZP/Tr = 189 (26%), and TZP/AUC = 96 (17.1%) (P < 0.001). Both drug group [(TZP; P = 0.0085)] and monitoring strategy [(Tr; P = 0.0007)] were highly associated with the development of AKI; however, the effect was not modified with interaction term [(TZP*Tr); 0.085)]. The odds of developing MAKE-30 were not different between any group and FEP/MEM/AUC. The effect of VAN/TZP on the development of AKI was not modified by the VAN monitoring strategy (AUC vs trough). MAKE-30 outcomes were not different among the four cohorts.

Assessing the impact of meropenem exposure on ceftolozane/tazobactam-resistance development in Pseudomonas aeruginosa using in vitro serial passage.

Patients infected with difficult-to-treat Pseudomonas aeruginosa are likely to receive meropenem (MEM) empirically before escalation to ceftolozane/tazobactam (C/T). We assessed whether pre-exposure to MEM affected C/T resistance development on C/T exposure. Nine clinical P. aeruginosa isolates were exposed to MEM 16 mg/L for 72 h. Then, isolates were serially passaged in the presence of C/T (concentration of 10 mg/L) for 72 h as two groups: an MEM-exposed group inoculated with MEM pre-exposed isolates and a non-MEM control group. At 24 h intervals, samples were plated on drug-free and drug-containing agar (C/T concentration 16/8 mg/L) and incubated to quantify bacterial densities (log10 cfu/mL). Growth on C/T agar indicated resistance development, and resistant population was calculated by dividing the cfu/mL on C/T plates by the cfu/mL on drug-free agar. At 72 h, resistant populations were detected in 6/9 isolates. In five isolates, MEM exposure significantly increased the prevalence of ceftolozane/tazobactam-resistance development; the percentages of resistance population were 100%, 100%, 53.5%, 31% and 3% for the MEM-exposed versus 0%, 0%, 2%, 0.35% and ≤0.0003% in the unexposed groups. One isolate had a similar resistant population at 72 h between the two groups. The remaining isolates showed no development of resistance, regardless of previous MEM exposure. MEM exposure may pre-dispose to C/T resistance development and thus limit the therapeutic utility of this β-lactam/β-lactamase inhibitor. Resistance may be a result of stress exposure or molecular-level mutations conferring cross-resistance. Further in vivo studies are needed to assess clinical implications of these findings.

The Triple Combination of Meropenem, Avibactam, and a Metallo-β-Lactamase Inhibitor Optimizes Antibacterial Coverage Against Different β-Lactamase Producers

This work explores the potential of a triple combination of meropenem (MEM), a novel metallo-β-lactamase (MBL) inhibitor (indole-2-carboxylate 58 (InC58)), and a serine-β-lactamase (SBL) inhibitor (avibactam (AVI)) for broad-spectrum activity against carbapenemase-producing bacteria. A diverse panel comprising MBL- and SBL-producing strains was used for susceptibility testing of the triple combination using the agar dilution method. The frequency of resistance (FoR) to MEM combined with InC58 was investigated. Mutants were sequenced and tested for cross resistance, fitness, and the stability of the resistance phenotype. Compared with the double combinations of MEM plus an SBL or MBL inhibitor, the triple combination extended the spectrum of activity to most of the isolates bearing SBLs (oxacillinase-48 (OXA-48) and Klebsiella pneumoniae carbapenemase-2 (KPC-2)) and MBLs (New Delhi metallo-β-lactamases (NDMs)), although it was not effective against Verona integron-encoded metallo-β-lactamase (VIM)-carrying Pseudomonas aeruginosa (P. aeruginosa) and OXA-23-carrying Acinetobacter baumannii (A. baumannii). The FoR to MEM plus InC58 ranged from 2.22 × 10−7 to 1.13 × 10−6. The resistance correlated with mutations to ompC and comR, affecting porin C and copper permeability, respectively. The mutants manifested a fitness cost, a decreased level of resistance during passage without antibiotic pressure, and cross resistance to another carbapenem (imipenem) and a β-lactamase inhibitor (taniborbactam). In conclusion, compared with the dual combinations, the triple combination of MEM with InC58 and AVI showed a much wider spectrum of activity against different carbapenemase-producing bacteria, revealing a new strategy to combat β-lactamase-mediated antimicrobial resistance.

Carbapenem non-susceptibility overcalling by BD phoenix NMIC-500 panel

We aimed to assess the accuracy of BD Phoenix for determining carbapenem susceptibility because we observed a decline in carbapenem susceptibility rate from the biannual cumulative data, after we transitioned to the BD Phoenix form Vitek 2 system.Between October 2021 and May 2022, we collected 82 non-duplicated Enterobacterales showing non-susceptible to at least one of the three carbapenems by BD Phoenix. We performed the broth microdilution (BMD) and disk diffusion (DD) according to the CLSI guideline.Compared to BMD, the categorical agreements for ertapenem (ERT), imipenem (IPM) and meropenem (MEPM) was 58.8%, 56.8% and 91.5% for BD Phoenix and it was 85.4%, 89.0%, and 97.6%, respectively, for DD (p value; 0.0001 for ERT and IPM, p value; 0.17 for MEPM). The major errors/minor errors for ERT, IPM, and MEPM were 14.0%/31.7%, 2.94%/40.7%, and 2.56%/6.10%, respectively for BD Phoenix, compared to 0%/14.6%, 0%/9.8%, and 0%/2.5%, for DD. While errors in the BD Phoenix showed tendency towards resistance, those in DD displayed no tendency towards either resistance or susceptibility. With DD, 21 out of the 27 isolates showing susceptible/intermediate/susceptible pattern (ERT/IPM/MEPM) and 13 out of the 16 isolates showing intermediate/susceptible/susceptible pattern (ERT/IPM/MEPM), were correctly categorized by DD. However, for 22 isolates showing resistant/susceptible/susceptible pattern (ERT/IPM/MEPM), only 13 isolates were correctly categorized by DD.In conclusion, to mitigate the risk of overcalling carbapenem non-susceptibility with BD Phoenix, it will be helpful to perform a complementary test using DD and to provide comments on the DD results to clinicians.

Effect of a Declined Plasma Concentration of Valproic Acid Induced by Meropenem on the Antiepileptic Efficacy of Valproic Acid.

This study aimed to indicate whether a declined plasma concentration of valproic acid (VPA) induced by co-administration of meropenem (MEPM) could affect the antiepileptic efficacy of VPA. We retrospectively reviewed data of hospitalized patients who were diagnosed with status epilepticus or epilepsy between 2010 and 2019. Patients co-administered VPA and MEPM during hospitalization were screened and assigned to the exposure group, while those co-administerd VPA and other broad-spectrum antibiotics were allocated to the control group. The exposure group and control group included 50 and 11 patients, respectively. With a similar dosage of VPA, the plasma concentration of VPA significantly decreased during co-administration (24.6 ± 4.3 μg/mL) compared with that before co-administration (88.8 ± 13.6 μg/mL, p < 0.0001), and it was partly recovered with the termination of co-administration (39.8 ± 13.2 μg/mL, p = 0.163) in the exposure group. The inverse probability of treatment weighting estimated the treatment efficacy via changes in seizure frequency, seizure duration, and concomitant use of antiepileptic drugs, which were not significantly different between the exposure and control groups. In the exposure group, there was no significant differences in seizure frequency between the periods of before-during and before-after (p = 0.074 and 0.153, respectively). Seizure duration during VPA-MEPM co-administration was not significantly different from that before co-administration (p = 0.291). In this study, the reduced plasma concentration of VPA induced by the co-administration of MEPM did not affect the antiepileptic efficacy of VPA. This conclusion should be interpreted with caution, and more research is warranted. Chinese Clinical Trial Registry: ChiCTR2000034567. Registered on 10 July 2020.

Relationship between Target Time above Minimum Inhibitory Concentration Achievement Rate of Meropenem Using Monte Carlo Simulation and In-Hospital Survival in Patients with Pseudomonas aeruginosa Bacteremia.

Pseudomonas aeruginosa bacteremia is associated with a high mortality rate, and meropenem (MEPM) is commonly used to treat it. However, the relationship between the time above the minimum inhibitory concentration (fT>MIC) of MEPM and its therapeutic efficacy in P. aeruginosa bacteremia has not been explored. This study aimed to investigate this relationship by defining the target % fT>MIC of MEPM as 75%. The retrospective study spanned 14 years and included hospitalized patients treated with MEPM for P. aeruginosa bacteremia. Monte Carlo simulation was used to calculate the probability of target attainment (PTA) for each patient, and the threshold for a PTA of 75% fT>MIC associated with in-hospital survival was determined using receiver operating characteristic (ROC) curves. The ROC curve-derived PTA associated with improved in-hospital survival was 65.0%, a significant finding in multivariate logistic regression analysis adjusted for patient background factors (odds ratio: 20.49, 95% confidence interval: 3.02-245.23, p = 0.005). This result suggests a dosing regimen that achieves a PTA of at least 65% when the target fT>MIC of MEPM for treating P. aeruginosa bacteremia is defined as 75%.

Ethambutol and meropenem/clavulanate synergy promotes enhanced extracellular and intracellular killing of Mycobacterium tuberculosis.

Increasing evidence supports the repositioning of beta-lactams for tuberculosis (TB) therapy, but further research on their interaction with conventional anti-TB agents is still warranted. Moreover, the complex cell envelope of Mycobacterium tuberculosis (Mtb) may pose an additional obstacle to beta-lactam diffusion. In this context, we aimed to identify synergies between beta-lactams and anti-TB drugs ethambutol (EMB) and isoniazid (INH) by assessing antimicrobial effects, intracellular activity, and immune responses. Checkerboard assays with H37Rv and eight clinical isolates, including four drug-resistant strains, exposed that only treatments containing EMB and beta-lactams achieved synergistic effects. Meanwhile, the standard EMB and INH association failed to produce any synergy. In Mtb-infected THP-1 macrophages, combinations of EMB with increasing meropenem (MEM) concentrations consistently displayed superior killing activities over the individual antibiotics. Flow cytometry with BODIPY FL vancomycin, which binds directly to the peptidoglycan (PG), confirmed an increased exposure of this layer after co-treatment. This was reinforced by the high IL-1β secretion levels found in infected macrophages after incubation with MEM concentrations above 5 mg/L, indicating an exposure of the host innate response sensors to pathogen-associated molecular patterns in the PG. Our findings show that the proposed impaired access of beta-lactams to periplasmic transpeptidases is counteracted by concomitant administration with EMB. The efficiency of this combination may be attributed to the synchronized inhibition of arabinogalactan and PG synthesis, two key cell wall components. Given that beta-lactams exhibit a time-dependent bactericidal activity, a more effective pathogen recognition and killing prompted by this association may be highly beneficial to optimize TB regimens containing carbapenems.IMPORTANCEAddressing drug-resistant tuberculosis with existing therapies is challenging and the treatment success rate is lower when compared to drug-susceptible infection. This study demonstrates that pairing beta-lactams with ethambutol (EMB) significantly improves their efficacy against Mycobacterium tuberculosis (Mtb). The presence of EMB enhances beta-lactam access through the cell wall, which may translate into a prolonged contact between the drug and its targets at a concentration that effectively kills the pathogen. Importantly, we showed that the effects of the EMB and meropenem (MEM)/clavulanate combination were maintained intracellularly. These results are of high significance considering that the time above the minimum inhibitory concentration is the main determinant of beta-lactam efficacy. Moreover, a correlation was established between incubation with higher MEM concentrations during macrophage infection and increased IL-1β secretion. This finding unveils a previously overlooked aspect of carbapenem repurposing against tuberculosis, as certain Mtb strains suppress the secretion of this key pro-inflammatory cytokine to evade host surveillance.

A Real-World Study on the Clinical Characteristics, Outcomes, and Relationship between Antibiotic Exposure and Clostridioides difficile Infection.

Clostridioides difficile is a Gram-positive bacteria that causes nosocomial infections, significantly impacting public health. In the present study, we aimed to describe the clinical characteristics, outcomes, and relationship between antibiotic exposure and Clostridioides difficile infection (CDI) in patients based on reports from two databases. Thus, we conducted a retrospective study of patients diagnosed with CDI from Sibiu County Clinical Emergency Hospital (SCCEH), Romania, followed by a descriptive analysis based on spontaneous reports submitted to the EudraVigilance (EV) database. From 1 January to 31 December 2022, we included 111 hospitalized patients with CDI from SCCEH. Moreover, 249 individual case safety reports (ICSRs) from EVs were analyzed. According to the data collected from SCCEH, CDI was most frequently reported in patients aged 65-85 years (66.7%) and in females (55%). In total, 71.2% of all patients showed positive medical progress. Most cases were reported in the internal medicine (n = 30, 27%), general surgery (n = 26, 23.4%), and infectious disease (n = 22, 19.8%) departments. Patients were most frequently exposed to ceftriaxone (CFT) and meropenem (MER). Also, in the EV database, most CDI-related ADRs were reported for CFT, PIP/TAZ (piperacillin/tazobactam), MER, and CPX (ciprofloxacin). Understanding the association between previous antibiotic exposure and the risk of CDI may help update antibiotic stewardship protocols and reduce the incidence of CDI by lowering exposure to high-risk antibiotics.