Comparative Review of the Carbapenems

Understanding the Functional Dynamics of the TokK Enzyme in Carbapenem Biosynthesis via MD Simulations and QM/MM Calculations

Due to the recent surge in antibiotic resistance, developing novel antibiotics is the demand of the time, and thus, a precise understanding of the catalytic mechanisms of enzymes involved in antibiotic biosynthesis becomes crucial. Here, we present a comprehensive investigation into the catalytic mechanism of TokK, a freshly characterized B12-dependent RSMT enzyme that plays an important role in carbapenem biosynthesis. Using MD simulations, we show how the plasticity of the active site facilitates substrate recognition while the quantum mechanics/molecular mechanics calculations provide a detailed mechanistic understanding of the methyl transfer process, elucidating stereochemical preferences. Notably, we demonstrate the indispensable role of Trp215 in orchestrating the proper orientation of the 5'-dA• radical for efficient substrate methylation, which strongly correlates with the previous findings where the mutation of Trp215 has severely affected the enzyme activity.

Carbapenemase producing Gram negative bacteria: Review of resistance and detection methods

Gram negative bacilli that are carbapenem resistant have emerged and are spreading worldwide. Infections caused by carbapenem resistant isolates posses a significant threat due to their high morbidity and mortality rates. Carbapenemases production by multi-drug resistant pathogens severely restricts treatment choices for illnesses caused by bacteria that are resistant to both carbapenems and majority of β-lactam antibiotics. Various phenotypic and genotypic methods for identification can distinguish between different classes of carbapenemase and identify pathogens that are resistant to carbapenems. The establishment of a quick, accurate and reliable test for identifying the clinical strains that produce the carbapenemase enzyme is essential for optimum diagnosis of microbial pathogens and management of the global rise in the prevalence of carbapenemase producing bacterial strains. The aim of this review was to summarize the mechanisms of carbapenem resistance and to provide an overview of different carbapenemase detection methods for carbapenem resistant Gram negative bacilli.

Ertapenem's therapeutic potential for Mycobacterium avium lung disease in the hollow fibre model

INTRODUCTION

Guideline-based therapy for Mycobacterium avium complex (MAC) pulmonary disease achieves sustained sputum conversion rates in only 43-53% of patients. Repurposing of β-lactam antibiotics such as ertapenem could expedite design of more efficacious regimens, compared to developing new drugs.

METHODS

We performed an ertapenem exposure-response study in the hollow fibre system model of intracellular MAC (HFS-MAC). We recapitulated human-like intrapulmonary concentration-time profiles of eight once-daily intravenous doses of ertapenem over 28 days and performed repetitive sampling for drug concentration-time profiles and MAC burden. The % of time concentration persisted above MIC (%TMIC) mediating either 50% or 80% of maximal effect (E50, EC80) were identified. The EC80 was used as target exposure in a 10 000 subject Monte Carlo experiments for ertapenem doses of 1G, 2G, or 4G administered once versus twice daily.

RESULTS

The ertapenem MIC ranged from 0.5 to 2 mg/L on three occasions. Ertapenem achieved a half-life of 4.04 ± 0.80 h in the HFS-MAC and killed a maximum of 2.17 log10 CFU/mL below day 0. The EC50 was %TMIC of 75.9% (95% confidence interval: 68.43%-86.54%) and the EC80 was %TMIC of 100%. Target attainment probability was >90% for 1G twice daily up to an MIC of 2 mg/L, while for 2G twice daily the susceptibility MIC breakpoint was 4-8 mg/L.

CONCLUSIONS

Ertapenem microbial kill below day 0 burden was better than guideline-based therapy drugs in the HFS-MAC in the past. Ertapenem is a promising drug for novel combination therapies for MAC lung disease.

Surgical prophylaxis in pancreatoduodenectomy: Is cephalosporin still the drug of choice in patients with biliary stents in situ?

BACKGROUND

Universal surgical prophylaxis for pancreatoduodenectomy (PD) is practiced, with cephalosporins recommended in most guidelines. Recent studies suggest piperacillin-tazobactam (PTZ) prophylaxis in biliary-stented patients is superior in preventing surgical site infections (SSIs). This study aims to refine surgical prophylaxis recommendations based on the local microbial profile and evaluate the clinical outcomes of biliary-stented compared with non-stented patients.

METHODS

This was a retrospective study of all consecutive PD patients at Singapore General Hospital between January 2013 to December 2019. The primary outcome was post-operative SSI rates. Secondary outcomes included rates of ceftriaxone-resistant Klebsiella pneumoniae, Escherichia coli, and Enterococcus species from intraoperative bile cultures and 30-day mortality.

RESULTS

There were 130 biliary-stented and 211 non-stented patients included. Majority of biliary-stented patients received ceftriaxone ± metronidazole prophylaxis (83/130, 63.8 %) while 30/130 (23.8 %) received PTZ. Most non-stented patients received ceftriaxone ± metronidazole prophylaxis (163/211, 77.3 %). Between biliary-stented and non-stented patients, post-operative SSIs (40.8 % vs 38.4 %, p = 0.662), and 30-day mortality rates (1.5 % vs 1.4 %, p = 1.000) were comparable. The adjusted odds of post-operative SSIs was significantly lower in biliary-stented patients prescribed PTZ as compared to non-PTZ prophylaxis (0.29, 95 % CI (0.10-0.79), p = 0.015). Ceftriaxone-resistant Klebsiella spp. and/or Escherichia coli (27.6 % vs 3.8 %, p < 0.001) as well as Enterococcus species (46.1 % vs 11.5 %, p < 0.001), were more prevalent in intraoperative bile cultures of biliary-stented patients, while frequencies in non-stented patients were low.

CONCLUSION

PTZ prophylaxis effectively reduced SSIs in stented patients post-pancreatoduodenectomy. Based on the local microbial profile, ceftriaxone prophylaxis may be used for prophylaxis in non-stented patients.

Current state and novel outlook on prevention and treatment of rising antibiotic resistance in urinary tract infections

Antibiotic-resistant bacteria are currently an important public health concern posing a serious threat due to their resistance to the current arsenal of antibiotics. Uropathogens Escherichia coli (UPEC), Proteus mirabilis, Klebsiella pneumoniae and Enterococcus faecalis, antibiotic-resistant gram-negative bacteria, cause serious cases of prolonged UTIs, increasing healthcare costs and potentially even leading to the death of an affected patient. This review discusses current knowledge about the increasing resistance to currently recommended antibiotics for UTI therapy, as well as novel therapeutic options. Traditional antibiotics are still a part of the therapy guidelines for UTIs, although they are often not effective and have serious side effects. Hence, novel drugs are being developed, such as combinations of β-lactam antibiotics with cephalosporins and carbapenems. Siderophoric cephalosporins, such as cefiderocol, have shown potential in the treatment of individuals with significant gram-negative bacterial infections, as well as aminoglycosides, fluoroquinolones and tetracyclines that are also undergoing clinical trials. The use of cranberry and probiotics is another potential curative and preventive method that has shown antimicrobial and anti-inflammatory effects. However, further studies are needed to assess the efficacy and safety of probiotics containing cranberry extract for UTI prevention and treatment. An emerging novel approach for UTI treatment is the use of immuno-prophylactic vaccines, as well as different nanotechnology solutions such as nanoparticles (NP). NP have the potential to be used as delivery systems for drugs to specific targets. Furthermore, nanotechnology could enable the development of nano antibiotics with improved features by the application of different NPs in their structure, such as gold and copper NPs. However, further high-quality research is required for the synthesis and testing of these novel molecules, such as safety evaluation and pharmacovigilance.

Antibiotics, Analgesic Sedatives, and Antiseizure Medications Frequently Used in Critically Ill Neonates: A Narrative Review

Antibiotic, analgesic sedative, and antiseizure medications are among the most commonly used medications in preterm/sick neonates, who are at high risk of nosocomial infections, central nervous system complications, and are exposed to numerous painful/stressful procedures. These severe and potentially life-threatening complications may have serious short- and long-term consequences and should be prevented and/or promptly treated. The reported variability in the medications used in neonates indicates the lack of adequate neonatal studies regarding their effectiveness and safety. Important obstacles contributing to inadequate studies in preterm/sick infants include difficulties in obtaining parental consent, physicians' unwillingness to recruit preterm infants, the off-label use of many medications in neonates, and other scientific and ethical concerns. This review is an update on the use of antimicrobials (antifungals), analgesics (sedatives), and antiseizure medications in neonates, focusing on current evidence or knowledge gaps regarding their pharmacokinetics, indications, safety, dosage, and evidence-based guidelines for their optimal use in neonates. We also address the effects of early antibiotic use on the intestinal microbiome and its association with long-term immune-related diseases, obesity, and neurodevelopment (ND). Recommendations for empirical treatment and the emergence of pathogen resistance to antimicrobials and antifungals are also presented. Finally, future perspectives on the prevention, modification, or reversal of antibiotic resistance are discussed.

In vitro effects of the new oral β-lactamase inhibitor xeruborbactam in combination with oral β-lactams against clinical Mycobacterium abscessus isolates

Non-tuberculosis mycobacteria (NTM), particularly Mycobacterium abscessus subsp. abscessus (M. abscessus), are increasingly being recognized as etiological agents of NTM pulmonary disease. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics, including β-lactams. M. abscessus produces a class A β-lactamase, whose activity is inhibited by cyclic boronic acid β-lactamase inhibitors. We aimed to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid β-lactamase inhibitor, against M. abscessus when combined with five β-lactams (amoxicillin, tebipenem, cefdinir, cefuroxime, and cefoxitin). The drug susceptibilities of 43 M. abscessus clinical isolates obtained from 43 patients between August 2005 and May 2014 were tested. The MIC results for each β-lactam with or without 4 µg/mL xeruborbactam were examined. Xeruborbactam lowered the MIC90 values of tebipenem, amoxicillin, cefuroxime, and cefdinir by 5, ≥4, 3, and 3 dilutions, respectively. The MIC90 values of cefoxitin without xeruborbactam were 32 µg/mL and did not change upon the addition of xeruborbactam. The lowest MIC90 value was obtained for tebipenem with xeruborbactam. Almost all isolates had an MIC of 4 µg/mL; one isolate had an MIC of 2 µg/mL. With respect to the susceptibility to the same family drug, the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%) for tebipenem with xeruborbactam. Combining tebipenem and xeruborbactam could be considered an effective all-oral regimen that benefits outpatient treatment of M. abscessus pulmonary disease.

IMPORTANCE

Mycobacterium abscessus subsp. abscessus (M. abscessus) disease is treated in two phases; injectable drugs for initial followed by others for continuation. There is a need to develop all-oral treatment methods for M. abscessus infection, especially in the continuation phase. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics. This is the first report to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid β-lactamase inhibitor capable of inhibiting the class A β-lactamase produced by M. abscessus, against 43 M. abscessus clinical isolates when combined with five β-lactam antibiotics. Xeruborbactam lowered the MIC90 values of tebipenem by five dilutions, and the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%). We showed that the tebipenem-xeruborbactam combination might be of interest to explore further as a potentially effective oral regimen for outpatient treatment of M. abscessus pulmonary disease.

RATA: A novel class A carbapenemase with broad geographic distribution and potential for global spread

Carbapenem resistance's global proliferation poses a significant public health challenge. The primary resistance mechanism is carbapenemase production. In this study, we discovered a novel carbapenemase, RATA, located on the chromosome of Riemerella anatipestifer isolates. This enzyme shares ≤52 % amino acid sequence identity with other known β-lactamases. Antimicrobial susceptibility tests and kinetic assays demonstrated that RATA could hydrolyze not only penicillins and extended-spectrum cephalosporins but also monobactams, cephamycins, and carbapenems. Furthermore, its activity was readily inhibited by β-lactamase inhibitors. Bioinformatic analysis revealed 46 blaRATA-like genes encoding 27 variants in the NCBI database, involving 21 different species, including pathogens, host-associated bacteria, and environmental isolates. Notably, blaRATA-positive strains were globally distributed and primarily collected from marine environments. Concurrently, taxonomic analysis and GC content analysis indicated that blaRATA orthologue genes were predominantly located on the chromosomes of Flavobacteriaceae and shared a similar GC content as Flavobacteriaceae. Although no explicit mobile genetic elements were identified by genetic environment analysis, blaRATA-2 possessed the ability of horizontal transfer in R. anatipestifer via natural transformation. This work's data suggest that RATA is a new chromosome-encoded class A carbapenemase, and Flavobacteriaceae from marine environments could be the primary reservoir of the blaRATA gene.

Population pharmacokinetics, dosing optimization and clinical outcomes of biapenem in patients with sepsis

Introduction: Biapenem is a carbapenem antibiotic widely used in Asia, can be used for the treatment of adults and children with infections due to susceptible bacteria. Although biapenem is utilized in the treatment of a diverse range of bacterial infections, current pharmacokinetic data in the context of septic populations remain limited. Consequently, our research aims to evaluate the pharmacokinetics and efficacy of biapenem within a septic population to optimize biapenem therapy. Methods: In this study, we characterized the pharmacokinetics of biapenem in septic patients using a population pharmacokinetic (PPK) approach. The clinical PK data to develop the PPK model were obtained from 317 septic patients admitted to Nanjing Drum Tower Hospital between 2018 and 2022. All patients were randomized to the modeling and validation cohorts at a 3:1 ratio, with PPK modeling and validation performed utilizing the NONMEM software. Results: The model found to best describe the available data was a two-compartment PPK model with first-order elimination characterized by the parameters clearance (CL), central volume (V1), peripheral volume (V2), and intercompartmental clearance (Q). A covariate analysis identified that creatinine clearance (CLCR) was a significant covariate influencing biapenem CL, while blood urea nitrogen (BUN) was a significant covariate influencing biapenem Q. Accoding to the clinical outcome analyses, 70% of the time that the free antimicrobial drug concentration exceeds the MIC (fT >MIC) is associated with favourable clinical outcomes. The PPK model was then used to perform Monte Carlo simulations to evaluate the probability of attaining 70% fT >MIC. Conclusions: A final PPK model of biapenem was established for patients with sepsis. The current daily dosage regimen of 1.2 g may insufficient to achieve 70% fT >MIC in septic patients. The dosage regimen of 600 mg every 6 h appears to be the optimal choice.

Assessment of antibiotic-resistant infection risks associated with reclaimed wastewater irrigation in intensive tomato cultivation

Agricultural irrigation using reclaimed urban wastewater (RWW) represents a sustainable practice to meet the ever-increasing water stress in modern societies. However, the occurrence of residual antibiotics and antibiotic resistant bacteria (ARB) in RWW is an important human health concern. This study applied for the first time a novel Simple-Death dose-response model to the field data of Escherichia coli and Pseudomonas spp. collected from three greenhouses for cultivation of tomatoes irrigated with RWW. The model estimates the risk of infection by enteropathogenic E. coli associated with consumption of tomatoes and the risk of eye-infection caused by Pseudomonas aeruginosa in cultivation soil through hand-to-eye contacts. The fraction of antibiotic resistant (AR)-E. coli measured in irrigation water and AR-Pseudomonas spp. in soil was incorporated in the model to estimate the survival of ARB and antibiotic susceptible bacteria in the presence of trace level of antibiotics in human body. The results showed that the risk of E. coli infection through consumption of tomatoes irrigated with RWW is within the WHO and USEPA recommended risk threshold (<10-4); Pseudomonas aeruginosa eye-infection risk is at or below the acceptable risk level. The presence of residual antibiotic in human body reduced the overall risk probabilities of infections but selectively enhanced the survival of ARB in comparison to their susceptible counterparts, which resulted in antibiotic untreatable infection. Therefore, the outcomes of this study call for a new risk threshold for antibiotic untreatable infections and highlight the key importance of adopting work safety measures for better human health protection.

Therapeutic drug monitoring of six contraindicated/co-administered drugs by simple and green RP-HPLC-PDA; application to spiked human plasma

Therapeutic drug monitoring is an important clinical testing of the drugs to monitor their concentrations in plasma in order to guarantee their optimal impact, and to avoid any side effects resulting from drug-drug interactions. A green reversed-phase high-performance liquid chromatographic method using a photodiode array detector (RP-HPLC-PDA) was developed for the simultaneous determination of three carbapenem antibiotics (Imipenem, ertapenem, and meropenem) with the co-formulated drug (cilastatin) and contraindicated drugs (probenecid and warfarin) in spiked human plasma. The separation was achieved at 25 °C using a gradient elution of a mixture of mobile phase A: methanol and mobile phase B: phosphate buffer (pH 3.0). The photodiode array detector was adjusted at 220 nm. Bioanalytical method validation was carried out as per the FDA guidelines, and the method showed good linearity ranges for the six drugs that included their Cmax levels along with low limits of quantification. Based on the results, the method was found to be accurate and precise; with high % recovery and good % RSD, respectively. The method was successfully applied to spiked human plasma, signifying a good potential to be implemented in future TDM studies of these drugs when co-administered together.

Redirecting pantoprazole as a metallo-beta-lactamase inhibitor in carbapenem-resistant Klebsiella pneumoniae

The development of resistance to carbapenems in Klebsiella pneumoniae due to the production of metallo-β-lactamases (MBLs) is a critical public health problem because carbapenems are the last-resort drugs used for treating severe infections of extended-spectrum β-lactamases (ESBLs) producing K. pneumoniae. Restoring the activity of carbapenems by the inhibition of metallo-β-lactamases is a valuable approach to combat carbapenem resistance. In this study, two well-characterized clinical multidrug and carbapenem-resistant K. pneumoniae isolates were used. The sub-inhibitory concentrations of pantoprazole and the well-reported metallo-β-lactamase inhibitor captopril inhibited the hydrolytic activities of metallo-β-lactamases, with pantoprazole having more inhibiting activities. Both drugs, when used in combination with meropenem, exhibited synergistic activities. Pantoprazole could also downregulate the expression of the metallo-β-lactamase genes bla NDM and bla VIM. A docking study revealed that pantoprazole could bind to and chelate zinc ions of New Delhi and Verona integron-encoded MBL (VIM) enzymes with higher affinity than the control drug captopril and with comparable affinity to the natural ligand meropenem, indicating the significant inhibitory activity of pantoprazole against metallo-β-lactamases. In conclusion, pantoprazole can be used in combination with meropenem as a new strategy for treating serious infections caused by metallo-β-lactamases producing K. pneumoniae.

[Clinical practice guidelines for meropenem therapy in neonatal sepsis (2024)]

Meropenem is one of the most widely used special-grade antimicrobial agents in the treatment of neonatal sepsis. However, its irrational use has led to an increasingly severe problem of bacterial multidrug resistance. The guideline was developed following standardized methods and procedures, and provides 12 recommendations specifically addressing 9 clinical issues. The recommendations cover various aspects of meropenem use in neonates, including timing of administration, recommended dosage, extended infusion, monitoring and assessment, antimicrobial adjustment strategies, treatment duration, and treatment strategies for carbapenem-resistant Enterobacteriaceae infections. The aim of the guideline is to provide evidence-based recommendations and guidance for the rational use of meropenem in neonates with sepsis.

Therapeutic drug monitoring of vancomycin and meropenem: Illustration of the impact of inaccurate information in dose administration time

OBJECTIVES

To illustrate the impact of errors in documented dose administration time on therapeutic drug monitoring (TDM)-based target attainment evaluation for vancomycin and meropenem, and to explore the influence of drug and patient characteristics, and TDM sampling strategies.

METHODS

Bedside observations of errors in documented dose administration times were collected. Population pharmacokinetic simulations were performed for vancomycin and meropenem, evaluating different one- and two-sampling strategies for populations with estimated creatinine clearance (CLcr) of 30, 80 or 130 mL/min. The impact of errors was evaluated as the proportion of individuals incorrectly considered to have reached the target.

RESULTS

Of 143 observed dose administrations, 97% of doses were given within ±30 min of the documented time. For vancomycin, a +30 min error was predicted to result in a 0.1-3.9 percentage point increase of cases incorrectly evaluated as reaching area under the concentration-time curve during a 24-hour period (AUC24)/minimum inhibitory concentration (MIC) >400, with the largest increase for patients with augmented renal clearance and peak and trough sampling. For meropenem, a +30 min error resulted in a 1.3-6.4 and 0-20 percentage point increase of cases incorrectly evaluated as reaching 100% T>MIC, and 50% T>MIC, respectively. Overall, mid-dose and trough sampling was most favourable for both antibiotics.

CONCLUSIONS

For vancomycin, simulations indicate that TDM-based target attainment evaluation is robust with respect to the observed errors in dose administration time of ±30 min; however, the errors had a potentially clinically important impact in patients with augmented renal clearance. For meropenem, extra measures to promote correct documentation are warranted when using TDM, as the impact of errors was evident even in patients with normal renal function.

Imipenem-metal complexes: Computational analysis and toxicity studies with wastewater model microorganisms

The occurrence of antibiotic residues in diverse water sources has long been acknowledged as a potential health concern due to the emergence and spread of antibiotic-resistant bacteria and genes. However, there have been limited studies into the presence of antibiotic-metal complexes (AMCs) in real-time wastewater matrices, and their impact on wastewater microbial communities. The present work, in this regard, investigated the stability of Imipenem-metal complexes (Me = Mg (II), Ca (II), Fe (II), Cu (II), and Al (III)) with computational studies, stoichiometry with potentiometric measurements, and their antibacterial activity towards wastewater model microorganisms- Bacillus subtilis (B. subtilis) and Escherichia coli (E. Coli) by Colony Forming Unit (CFU) method. The lower energy of Imipenem-metal complexes than the parent antibiotic- Imipenem, during energy optimization using density functional (DFT) methods, revealed that metal interactions of Imipenem stabilize the drug by minimizing its energy. Further, CFU studies indicated that these complexes display higher antimicrobial activity than parent antibiotics. The electron delocalization over the entire chelated system (AMCs) reduces polarity and increases the lipophilicity of the complexes, thereby facilitating stronger interaction between AMCs and the bacterial cell membrane. Results indicate increased antibacterial activity of Imipenem-metal complexes for both E. coli and B. subtilis. The antibacterial activity, was however, more pronounced in B. subtilis, with >97% growth inhibition for metal complexes of Imipenem (at a Minimum Inhibitory Concentration of 20 nM or 6 ppb (i.e., MIC90)), for both the stoichiometric ratios (metal to ligand) ratios (M: L 1: 1 and 2: 1). All around, with increased stability and toxicity, AMCs are emerging as contaminants of concern and demand immediate attention to devise methods for their removal.

The directed evolution of NDM-1

β-Lactam antibiotics are among the most frequently prescribed therapeutic agents. A common mechanism of resistance toward β-lactam antibiotics is the production of β-lactamases. These enzymes are capable of hydrolyzing the β-lactam bond, rendering the drug inactive. Among the four described classes, the metallo- β-lactamases (MBLs, class B) employ one or two zinc ions in the active site for catalysis. One of the three most clinically relevant MBLs is New Delhi Metallo- β-Lactamase (NDM-1). The current study sought to investigate the in vitro protein evolution of NDM-1 β-lactamase using error-prone polymerase chain reaction. Evaluation revealed that variants were not found to confer higher levels of resistance toward meropenem based on amino acid substitutions. Thus, we postulate that increases in transcription or changes in zinc transport may be clinically more relevant to meropenem resistance than amino acid substitutions.

Investigation of in vitro antimicrobial and cytotoxic effects of gold nanoparticles capped with meropenem and imipenem

Aim: This study aimed to investigate the in vitro antimicrobial effect of gold nanoparticles capped with meropenem and imipenem against various strains and to evaluate the cytotoxic effect of gold nanoparticles on healthy human colon epithelial cells. Materials & methods: Gold nanoparticles were synthesized via the Turkevich method and tested for antimicrobial effects using broth microdilution. Cell culture studies were performed using a cytotoxicity assay with alamarBlue™. Results & conclusion: Nanoparticles (10-20 nm) with antibiotic coating were more effective against Escherichia coli, Proteus spp. and Serratia marcescens than pure antibiotics. They had a cytotoxic effect on cells at high concentrations but were safe at low concentrations.

Carbapenem resistance in Enterobacterales from agricultural, environmental and clinical origins: South Africa in a global context

Carbapenem agents are regarded as last-resort antibiotics, however, bacterial resistance towards carbapenems has been reported in both clinical and agricultural settings worldwide. Carbapenem resistance, defined as the resistance of a bacteria towards one or more carbapenem drugs, can be mediated in either of, or a combination of, three mechanisms-although, the mechanism mediated through the production of carbapenemases (β-lactamases that are able to enzymatically degrade carbapenems) is of most significance. Of particular concern is the occurrence of carbapenemase producing Enterobacterales (CPE), with literature describing a dramatic increase in resistance globally. In South Africa, increases of carbapenemase activity occurring in Enterobacter species, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa have recently been reported. CPE can also be found in agricultural environments, as global studies have documented numerous instances of CPE presence in various animals such as pigs, cattle, seafood, horses and dogs. However, most reports of CPE occurrence in agricultural settings come from Northern America, Europe and some parts of Asia, where more extensive research has been conducted to understand the CPE phenomenon. In comparison to clinical data, there are limited studies investigating the spread of CPE in agricultural settings in Africa, highlighting the importance of monitoring CPE in livestock environments and the food chain. Further research is necessary to uncover the true extent of CPE dissemination in South Africa. This review will discuss the phenomenon of bacterial antibiotic resistance (ABR), the applications of the carbapenem drug and the occurrence of carbapenem resistance globally.

In vitro activity of new combinations of β-lactam and β-lactamase inhibitors against the Mycobacterium tuberculosis complex

As meropenem-clavulanic acid is recommended for the treatment of drug-resistant tuberculosis, the repurposing of new carbapenem combinations may provide new treatment options, including oral alternatives. Therefore, we studied the in vitro activities of meropenem-vaborbactam, meropenem-clavulanic acid, and tebipenem-clavulanic acid. One hundred nine Mycobacterium tuberculosis complex (MTBC) clinical isolates were tested, of which 69 were pan-susceptible and the remaining pyrazinamide- or multidrug-resistant. Broth microdilution MICs were determined using the EUCAST reference method. Meropenem and tebipenem were tested individually and in combination with vaborbactam 8 mg/L and clavulanic-acid 2 and 4 mg/L, respectively. Whole-genome sequencing was performed to explore resistance mechanisms. Clavulanic acid lowered the modal tebipenem MIC approximately 16-fold (from 16 to 1 mg/L). The modal meropenem MIC was reduced twofold by vaborbactam compared with an approximately eightfold decrease by clavulanic acid. The only previously described high-confidence carbapenem resistance mutation, crfA T62A, was shared by a subgroup of lineage 4.3.4.1 isolates and did not correlate with elevated MICs. The presence of a β-lactamase inhibitor reduced the MTBC MICs of tebipenem and meropenem. The resulting MIC distribution was lowest for the orally available drugs tebipenem-clavulanic acid. Whether this in vitro activity translates to similar or greater clinical efficacy of tebipenem-clavulanic acid compared with the currently WHO-endorsed meropenem-clavulanic acid requires clinical studies. IMPORTANCE Repurposing of already approved antibiotics, such as β-lactams in combination with β-lactamase inhibitors, may provide new treatment alternatives for drug-resistant tuberculosis. Meropenem-clavulanic acid was more active in vitro compared to meropenem-vaborbactam. Notably, tebipenem-clavulanic acid showed even better activity, raising the potential of an all-oral treatment option. Clinical data are needed to investigate whether the better in vitro activity of tebipenem-clavulanic acid correlates with greater clinical efficacy compared with the currently WHO-endorsed meropenem-clavulanic acid.

HPLC/UV approach method for the first simultaneous estimation of molnupiravir and ertapenem as a binary mixture in human plasma and dosage form as a regimen for COVID-19 treatments

COVID-19 is a serious virus that can have a lot of effects, one of which is a secondary bacterial infection that can be more life-threatening and even lethal than the initial viral infection. Hence a fast and sensitive HPLC/UV method was developed and validated for the first estimation of a binary mixture of molnupiravir (MOL) and ertapenem (ERT) as a co-administrated medicine for the management of COVID-19 in pharmaceutical dosage forms, and human plasma samples. The drug combination was separated within 5 min via RP-ODS column using isocratic elution with a mobile phase of 0.05 M phosphate buffer (pH 3.5): acetonitrile with a 76: 24% ratio v/v. The presented method provided a linear response ranging from 0.03 to 17.0 and 0.05-20 µg mL-1 with LOD values of 0.009 and 0.008 µg mL-1 for MOL and ERT respectively. The good separation and high sensitivity of the HPLC method provide the determination of the cited drugs in human plasma without matrix interference with a percent of recovery ranging from 94.97 ± 2.05 to 98.44 ± 1.92. Based on the results, this method could be utilized to monitor cited drugs in quality control and therapeutic laboratories.

Synthesis of tetracyclic dibenzo[b,f][1,4]oxazepine-fused β-lactams via visible-light-induced Staudinger annulation

An efficient visible-light-induced Staudinger [2 + 2] annulation reaction between α-diazo ketones and dibenzo[b,f][1,4]oxazepine/thiazepine-imines under catalyst-free conditions has been developed. This protocol provides a facile method to synthesize tetracyclic dibenzo[b,f][1,4]oxazepine/thiazepine-fused β-lactams bearing a quaternary carbon center with a broad substrate scope and high efficiency (37 examples, up to >99% yield).

Emergence of novel tigecycline resistance gene tet(X5) variant in multidrug-resistant Acinetobacter indicus of swine farming environments

Antibiotic-resistant bacteria are emerging all the time, but the continued emergence of novel resistance genes and genetic structures is even more alarming. Tigecycline is currently the important last barrier in the treatment of multidrug-resistant (MDR) infections. tet(X), a resistance gene to tigecycline, is the most prevalent and constantly emerging novel variants. In this research, we characterized two MDR Acinetobacter indicus strains to tigecycline that were identified and analyzed by antimicrobial susceptibility testing, conjugation transfer, whole genome sequencing (WGS) and bioinformatics analysis, and gene function analysis. The results showed that three tet(X) variants were carried in BDT201, including tet(X6) on the chromosome, tet(X3) on the plasmid pBDT201-2, and a novel tet(X5) variant adjacent to the ISAba1 elements on the plasmid pBDT201-3. The novel Tet(X5) variant showed 98.7% amino acid identity with Tet(X5) and was named Tet(X5.4). By expressing tet(X5.4) gene, the tigecycline minimum inhibitory concentration (MIC) values for Escherichia coli JM109 increased 32- fold (from 0.13 to 4 mg/L). BDT2076 contained tigecycline and carbapenems resistance genes, such as tet(X3), blaOXA-58, blaNDM-3, and blaCARB-2. The continuous emergence of MDR bacteria and resistance genes is a global environmental health issue that can not be ignored and therefore needs to pay more urgent attention to it.

Multi-approach methods to predict cryptic carbapenem resistance mechanisms in Klebsiella pneumoniae detected in Central Italy

The rapid emergence of carbapenem-resistant Klebsiella pneumoniae (Kp) strains in diverse environmental niches, even outside of the clinical setting, poses a challenge for the detection and the real-time monitoring of novel antimicrobial resistance trends using molecular and whole genome sequencing-based methods. The aim of our study was to understand cryptic resistance determinants responsible for the phenotypic carbapenem resistance observed in strains circulating in Italy by using a combined approach involving whole genome sequencing (WGS) and genome-wide association study (GWAS). In this study, we collected 303 Kp strains from inside and outside clinical settings between 2018-2022 in the Abruzzo region of Italy. The antimicrobial resistance profile of all isolates was assessed using both phenotypic and bioinformatic methods. We identified 11 strains resistant to carbapenems, which did not carry any known genetic determinants explaining their phenotype. The GWAS results showed that incongruent carbapenem-resistant phenotype was associated specifically with strains with two capsular types, KL13 and KL116 including genes involved in the capsule synthesis, encoding proteins involved in the assembly of the capsule biosynthesis apparatus, capsule-specific sugar synthesis, processing and export, polysaccharide pyruvyl transferase, and lipopolysaccharide biosynthesis protein. These preliminary results confirmed the potential of GWAS in identifying genetic variants present in KL13 and KL116 that could be associated with carbapenem resistance traits in Kp. The implementation of advanced methods, such as GWAS with increased antimicrobial resistance surveillance will potentially improve Kp infection treatment and patient outcomes.

Novel Beta Lactam Antibiotics for the Treatment of Multidrug-Resistant Gram-Negative Infections in Children: A Narrative Review

Infections due to carbapenem-resistant Enterobacterales (CRE) are increasingly prevalent in children and are associated with poor clinical outcomes, especially in critically ill patients. Novel beta lactam antibiotics, including ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, and cefiderocol, have been released in recent years to face the emerging challenge of multidrug-resistant (MDR) Gram-negative bacteria. Nonetheless, several novel agents lack pediatric indications approved by the Food and Drug Administration (FDA) and the European Medicine Agency (EMA), leading to uncertain pediatric-specific treatment strategies and uncertain dosing regimens in the pediatric population. In this narrative review we have summarized the available clinical and pharmacological data, current limitations and future prospects of novel beta lactam antibiotics in the pediatric population.

Optimizing the Use of Beta-Lactam Antibiotics in Clinical Practice: A Test of Time

Despite their limitations, the pharmacokinetics (PK) and pharmacodynamics (PD) indices form the basis for our current understanding regarding antibiotic development, selection, and dose optimization. Application of PK-PD in medicine has been associated with better clinical outcome, suppression of resistance, and optimization of antibiotic consumption. Beta-lactam antibiotics remain the cornerstone for empirical and directed therapy in many patients. The percentage of time of the dosing interval that the free (unbound) drug concentration remains above the minimal inhibitory concentration (MIC) (%fT > MIC) has been considered the PK-PD index that best predicts the relationship between antibiotic exposure and killing for the beta-lactam antibiotics. Time dependence of beta-lactam antibiotics has its origin in the acylation process of the serine active site of penicillin-binding proteins, which subsequently results in bacteriostatic and bactericidal effects during the dosing interval. To enhance the likelihood of target attainment, higher doses, and prolonged infusion strategies, with/or without loading doses, have been applied to compensate for subtherapeutic levels of antibiotics related to PK-PD changes, especially in the early phase of severe sepsis. To minimize resistance and maximize clinical outcome, empirical therapy with a meropenem loading dose followed by high-dose-prolonged infusion should be considered in patients with high inoculum infections presenting as severe (Gram negative) sepsis. Subsequent de-escalation and dosing of beta-lactam antibiotics should be considered as an individualized dynamic process that requires dose adjustments throughout the time course of the disease process mediated by clinical parameters that indirectly assess PK-PD alterations.

Carbapenem prescriptions: Compliance with guidelines in a pediatric hospital

BACKGROUND

This study aimed to describe the use of carbapenems in a pediatric tertiary center and to assess its compliance with national and local guidelines.

METHODS

This retrospective study focused on children who received at least one dose of carbapenems in a tertiary university hospital over a 1-year period (2019). The appropriateness of each prescription was assessed.

RESULTS

In total, 96 prescriptions were collected for 75 patients (median age 3 years [interquartile range, IQR: 0-9]). Most prescriptions were empirical (n = 77, 80%) and mainly concerned nosocomial infections (n = 69, 72%). At least one risk factor for extended-spectrum beta-lactamases was found in 48% (n = 46) of cases. The median duration of treatment with carbapenems was 5 days and it was over 7 days in 38% (n = 36) of cases. The use of carbapenems was considered appropriate in 95% (18/19) and 70% (54/77) of cases when therapy was guided by culture results or was empirical, respectively. De-escalation of carbapenem treatment within 72 h occurred in 31% (n = 30) of cases.

CONCLUSION

The use of carbapenems can be optimized in the pediatric population, even when the initial prescription for a carbapenem is considered appropriate.

Carbapenem Antibiotics Versus Other Antibiotics for Complicated Intra-abdominal Infections: a Systematic Review and Patient-Level Meta-analysis of Randomized Controlled Trials (PROSPERO CRD42018108854)

BACKGROUND

The treatment of complicated intra-abdominal infections remains a challenge. Both optimal medical and surgical therapy (i.e., source control) are needed to achieve low mortality and morbidity. The objective of this systematic review and meta-analysis is to determine the impact of carbapenem antibiotic therapy compared to other antibiotics in complicated intra-abdominal infections (secondary peritonitis) with an emphasis on mortality and postoperative complications.

METHODS

A systematic literature search from PubMed/Medline and Web of Science databases was carried out. The last search was conducted in August 2022. PRISMA guidelines were followed. Pre-defined outcomes were mortality, treatment success, treatment failure, and adverse events.

RESULTS

Ten randomized controlled trials, published from 1983 to 2013 with a total of 2377 patients (1255 patients in the carbapenem antibiotics group and 1122 in the control group), were identified. A meta-analysis comparing patients undergoing carbapenem antibiotic therapy and patients receiving other antibiotics was performed. No significant difference regarding mortality (OR 1.19, 95% CI [0.79; 1.82], p = 0.40), treatment success (OR 1.17, 95% CI [0.72; 1.91], p = 0.53), and treatment failure (OR 0.84, 95% CI [0.48; 1.45], p = 0.52) was observed. Carbapenem therapy was associated with fewer adverse events compared to therapy with other antibiotics (OR 0.79, 95% CI [0.65; 0.97], p = 0.022).

CONCLUSION

There is currently no evidence that carbapenem antibiotics are superior in terms of mortality, and success or failure for the treatment of complicated intra-abdominal infections (secondary peritonitis). The rate of adverse events is lower under carbapenem therapy compared to control antibiotics.

TRIAL REGISTRATION

PROSPERO 2018 CRD42018108854.

Genomic Characterization of Carbapenem-Resistant Bacteria from Beef Cattle Feedlots

Carbapenems are considered a last resort for the treatment of multi-drug-resistant bacterial infections in humans. In this study, we investigated the occurrence of carbapenem-resistant bacteria in feedlots in Alberta, Canada. The presumptive carbapenem-resistant isolates (n = 116) recovered after ertapenem enrichment were subjected to antimicrobial susceptibility testing against 12 different antibiotics, including four carbapenems. Of these, 72% of the isolates (n = 84) showed resistance to ertapenem, while 27% of the isolates (n = 31) were resistant to at least one other carbapenem, with all except one isolate being resistant to at least two other drug classes. Of these 31 isolates, 90% were carbapenemase positive, while a subset of 36 ertapenem-only resistant isolates were carbapenemase negative. The positive isolates belonged to three genera; Pseudomonas, Acinetobacter, and Stenotrophomonas, with the majority being Pseudomonas aeruginosa (n = 20) as identified by 16S rRNA gene sequencing. Whole genome sequencing identified intrinsic carbapenem resistance genes, including blaOXA-50 and its variants (P. aeruginosa), blaOXA-265 (A. haemolyticus), blaOXA-648 (A. lwoffii), blaOXA-278 (A. junii), and blaL1 and blaL2 (S. maltophilia). The acquired carbapenem resistance gene (blaPST-2) was identified in P. saudiphocaensis and P. stutzeri. In a comparative genomic analysis, clinical P. aeruginosa clustered separately from those recovered from bovine feces. In conclusion, despite the use of selective enrichment methods, finding carbapenem-resistant bacteria within a feedlot environment was a rarity.

From Batch to the Semi-Continuous Flow Hydrogenation of pNB, pNZ-Protected Meropenem

Meropenem is currently the most common carbapenem in clinical applications. Industrially, the final synthetic step is characterized by a heterogeneous catalytic hydrogenation in batch mode with hydrogen and Pd/C. The required high-quality standard is very difficult to meet and specific conditions are required to remove both protecting groups [i.e., p-nitrobenzyl (pNB) and p-nitrobenzyloxycarbonyl (pNZ)] simultaneously. The three-phase gas-liquid-solid system makes this step difficult and unsafe. The introduction of new technologies for small-molecule synthesis in recent years has opened up new landscapes in process chemistry. In this context, we have investigated meropenem hydrogenolysis using microwave (MW)-assisted flow chemistry for use as a new technology with industrial prospects. The reaction parameters (catalyst amount, T, P, residence time, flow rate) in the move from the batch process to semi-continuous flow were investigated under mild conditions to determine their influence on the reaction rate. The optimization of the residence time (840 s) and the number of cycles (4) allowed us to develop a novel protocol that halves the reaction time compared to batch production (14 min vs. 30 min) while maintaining the same product quality. The increase in productivity using this semi-continuous flow technique compensates for the slightly lower yield (70% vs. 74%) obtained in batch mode.

A Systematic Review on Antimicrobial Pharmacokinetic Differences between Asian and Non-Asian Adult Populations

While the relevance of inter-ethnic differences to the pharmacokinetic variabilities of antimicrobials has been reported in studies recruiting healthy subjects, differences in antimicrobial pharmacokinetics between Asian and non-Asian patients with severe pathologic conditions require further investigation. For the purpose of describing the potential differences in antimicrobial pharmacokinetics between Asian and non-Asian populations, a systematic review was performed using six journal databases and six theses/dissertation databases (PROSPERO record CRD42018090054). The pharmacokinetic data of healthy volunteers and non-critically ill and critically ill patients were reviewed. Thirty studies on meropenem, imipenem, doripenem, linezolid, and vancomycin were included in the final descriptive summaries. In studies recruiting hospitalised patients, inconsistent differences in the volume of distribution (V_d) and drug clearance (CL) of the studied antimicrobials between Asian and non-Asian patients were observed. Additionally, factors other than ethnicity, such as demographic (e.g., age) or clinical (e.g., sepsis) factors, were suggested to better characterise these pharmacokinetic differences. Inconsistent differences in pharmacokinetic parameters between Asian and non-Asian subjects/patients may suggest that ethnicity is not an important predictor to characterise interindividual pharmacokinetic differences between meropenem, imipenem, doripenem, linezolid, and vancomycin. Therefore, the dosing regimens of these antimicrobials should be adjusted according to patients' demographic or clinical characteristics that can better describe pharmacokinetic differences.

Peripheral Neuropathy Secondary to Ertapenem Administration for Treatment of Infectious Endocarditis

Ertapenem is a widely used broad-spectrum carbapenem antibiotic active against most species of gram-negative and gram-positive aerobes and anaerobes with specific targeting of the Amp C extended-spectrum beta-lactamases. It is advantageous for its once-daily dosing via IM or IV administration and minimal side effect profile for the treatment of community-acquired infections. We report an 80-year-old man presenting with reversible peripheral neuropathy following the administration and subsequent discontinuation of ertapenem for the treatment of acute infectious endocarditis. It is especially notable that our patient had less severe (i.e., stage 3) chronic kidney disease as opposed to current literature which only presents similar findings with more advanced kidney disease (stage 4-5). Upon cessation of ertapenem administration, our patient recovered to his baseline motor and sensory status over a period of four days. We believe there to be value in reporting this case, as well as value in reevaluating the current recommendations for ertapenem dosing in those with kidney compromise.

Phenotypic and Genotypic Correlation of Antimicrobial Susceptibility of Bacteroides fragilis: Lessons Learnt

Background Bacteroides fragilis is an opportunistic pathogen causing severe infections, including bacteremia. There have been increased reports of antimicrobial resistance in B. fragilis. However, phenotypic testing of susceptibility is time consuming and not cost effective for anaerobes. The present study investigates the correlation of phenotypic susceptibility with genotypic markers; to determine if these could be considered for deciding empirical therapy for B. fragilis. Material and methods Bacteroides fragilis isolates from various clinical samples including exudates, tissue, and body fluids were collected between November 2018 and January 2020 in the Department of Clinical Microbiology, Christian Medical College (CMC) Vellore. Species identification was done by Matrix Assisted Laser Desorption Ionization time of flight mass spectrometry (MALDI TOF) according to the manufacturer's instructions. A total number of 51 B. fragilis isolates were tested against metronidazole, clindamycin, piperacillin/tazobactam, and meropenem phenotypically by agar dilution method using Clinical & Laboratory Standards Institute (CLSI) 2019 guidelines and minimum inhibitory concentrations (MIC) were interpretated. The genotypic markers for antimicrobial resistance genes (nim, emrF, and cfiA) were studied by polymerase chain reaction (PCR) assay as per the standard protocol on all isolates to detect resistance genes. Results B. fragilis isolates in this study expressed 45%, 41%, and 16% phenotypic resistance to clindamycin, metronidazole, and meropenem, respectively, with least resistance to piperacillin/tazobactam (6%). Among the metronidazole resistant isolates, 52% harbored nim gene. Nim gene was also present in 76% (23/30) of the metronidazole susceptible isolates. Similarly, cfiA was present in all eight meropenem resistant isolates in addition to 22% (9/41) of the susceptible isolates. All cfiA negative isolates were phenotypically susceptible. Interestingly, 74% (17/23) of the clindamycin resistant isolates were positive for ermF. Conclusions Detection of a limited set of genes does not always correlate with phenotypic resistance to metronidazole and clindamycin due to the reported influence of insertion sequence (IS) elements, efflux, and other genetic determinants. Certainly, the absence of the cfiA gene can be employed to rule out meropenem resistance. However, redundant use of antibiotics such as meropenem along with metronidazole could be avoided for B. fragilis, which might otherwise elevate meropenem resistance. Recommendation of metronidazole requires prior phenotypic testing due to the reported 41% resistance.

Acinetobacter Baumannii Phages: Past, Present and Future

Acinetobacter baumannii (A. baumannii) is one of the most common clinical pathogens and a typical multi-drug resistant (MDR) bacterium. With the increase of drug-resistant A. baumannii infections, it is urgent to find some new treatment strategies, such as phage therapy. In this paper, we described the different drug resistances of A. baumannii and some basic properties of A. baumannii phages, analyzed the interaction between phages and their hosts, and focused on A. baumannii phage therapies. Finally, we discussed the chance and challenge of phage therapy. This paper aims to provide a more comprehensive understanding of A. baumannii phages and theoretical support for the clinical application of A. baumannii phages.

Meropenem Model-Informed Precision Dosing in the Treatment of Critically Ill Patients: Can We Use It?

The number of pharmacokinetic (PK) models of meropenem is increasing. However, the daily role of these PK models in the clinic remains unclear, especially for critically ill patients. Therefore, we evaluated the published meropenem models on real-world ICU data to assess their suitability for use in clinical practice. All models were built in NONMEM and evaluated using prediction and simulation-based diagnostics for the ability to predict the subsequent meropenem concentrations without plasma concentrations (a priori), and with plasma concentrations (a posteriori), for use in therapeutic drug monitoring (TDM). Eighteen PopPK models were included for evaluation. The a priori fit of the models, without the use of plasma concentrations, was poor, with a prediction error (PE)% of the interquartile range (IQR) exceeding the ±30% threshold. The fit improved when one to three concentrations were used to improve model predictions for TDM purposes. Two models were in the acceptable range with an IQR PE% within ±30%, when two or three concentrations were used. The role of PK models to determine the starting dose of meropenem in this population seems limited. However, certain models might be suitable for TDM-based dose adjustment using two to three plasma concentrations.

A Comprehensive Overview of the Antibiotics Approved in the Last Two Decades: Retrospects and Prospects

Due to the overuse of antibiotics, bacterial resistance has markedly increased to become a global problem and a major threat to human health. Fortunately, in recent years, various new antibiotics have been developed through both improvements to traditional antibiotics and the discovery of antibiotics with novel mechanisms with the aim of addressing the decrease in the efficacy of traditional antibiotics. This manuscript reviews the antibiotics that have been approved for marketing in the last 20 years with an emphasis on the antibacterial properties, mechanisms, structure-activity relationships (SARs), and clinical safety of these antibiotics. Furthermore, the current deficiencies, opportunities for improvement, and prospects of antibiotics are thoroughly discussed to provide new insights for the design and development of safer and more potent antibiotics.

Sequential C-H Methylation Catalyzed by the B12 -Dependent SAM Enzyme TokK: Comprehensive Theoretical Study of Selectivities

TokK is a B₁₂ -dependent radical SAM enzyme involved in the biosynthesis of the β-lactam antibiotic asparenomycin A. It can catalyze three methylations on different sp³ -hybridized carbon positions to introduce an isopropyl side chain at the β-lactam ring of pantetheinylated carbapenem. Herein, we report a quantum chemical study of the reaction mechanism of TokK. A stepwise ''push-pull'' radical relay mechanism is proposed for each methylation: a 5'-deoxyadenosine radical first abstracts a hydrogen atom from the substrate in the active site, then methylcobalamin directionally donates a methyl group to the substrate. More importantly, calculations were able to uncover the origin of observed chemoselectivity and stereoselectivity for the first methylation and regioselectivity for the following two methylations. Further detailed distortion/interaction analysis can help to unravel the main factors controlling the selectivities. Our findings of sequential methylations by TokK could have profound implications for studying other B₁₂ -dependent radical SAM enzymes.

Population pharmacokinetics and pharmacodynamics of imipenem in neutropenic adult patients

OBJECTIVE

Imipenem is recommended in patients with chemotherapy-induced febrile neutropenia. Although alterations of antibiotic pharmacokinetic parameters have been reported in such patients, little data is available on imipenem.

METHODS

Prospective, single-center, non-interventional pharmacokinetic cohort study in adults with chemotherapy-induced febrile neutropenia. Critically ill patients were excluded. Imipenem was administered as a 30-min infusion of 1000 mg/8h. Total imipenem plasma concentrations were assayed by high-performance liquid chromatography during neutropenia and just after neutrophil recovery. We estimated population pharmacokinetic parameters of imipenem by non-linear mixed-effect modelling using the SAEM algorithm.

RESULTS

Sixteen patients were included in the study, including nine women (56.3%), median age 37 years (range, 18.3; 78.3). Eight patients had an hematological malignancy (50.0%) and seven had a solid tumor (43.8%). Imipenem pharmacokinetics were best described by a one-compartment model with first-order elimination. Mean values for imipenem were: clearance 14.3L/h and 10.9L/h and volume of distribution 20.7L and 14.5 L during neutropenia and after recovery, respectively. Imipenem plasma area under the curve at steady state was reduced by 23% during neutropenia. However, all patients achieved a pharmacodynamic target of %fT_>MIC ≥ 40% with a regimen of 1000 mg/8 h or 500 mg/6 h, for MICs up to 2 mg/L. The pharmacodynamics profile for a target of %fT > MIC = 100% was however less favorable with 500 mg/6 h or 1000 mg/8 h either during or after neutropenia.

CONCLUSION

Pharmacokinetic/pharmacodynamic goals for imipenem were similar in patients during and after neutropenia, despite reduced plasma exposure.

Valproate-Induced Encephalopathy Presenting at Therapeutic Blood Concentrations: A Case Report and Literature Review

Patients presenting with hyperammonemic encephalopathy are likely to have hepatic encephalopathy. However, valproate (an anticonvulsant and mood stabilizer) can also cause hyperammonemic encephalopathy and belongs on the differential for patients taking it, especially if there are recent contributory medication changes. We present a case report of a 61-year-old woman with valproate-induced hyperammonemic encephalopathy but with an initial valproate level within the therapeutic range (50-100 mcg/dL). After withholding valproate and before additional treatment could be initiated, she became fully alert and oriented. We present a literature review exploring valproate toxicity and treatment. Our case shows that clinical suspicion for valproate-induced hyperammonemic encephalopathy is warranted even if the valproate level is within the therapeutic range.

A fresh pH-responsive imipenem-loaded nanocarrier against Acinetobacter baumannii with a synergetic effect

In recent years, the treatment of Acinetobacter baumannii infections has become a pressing clinical challenge due to its increasing incidence and its serious pathogenic risk. The research and development of new antibacterial agents for A. baumannii have attracted the attention of the scientific community. Therefore, we have constructed a new pH-responsive antibacterial nano-delivery system (Imi@ZIF-8) for the antibacterial treatment of A. baumannii. Due to its pH-sensitive characteristics, the nano-delivery system offers an improved release of the loaded imipenem antibiotic at the acidic infection site. Based on the high loading capacity and positive charge of the modified ZIF-8 nanoparticles, they are excellent carriers and are suitable for imipenem loading. The Imi@ZIF-8 nanosystem features synergistic antibacterial effects, combining ZIF-8 and imipenem to eliminate A. baumannii through different antibacterial mechanisms. When the loaded imipenem concentration reaches 20 µg/mL, Imi@ZIF-8 is highly effective against A. baumannii in vitro. Imi@ZIF-8 not only inhibits the biofilm formation of A. baumannii but also has a potent killing effect. Furthermore, in mice with celiac disease, the Imi@ZIF-8 nanosystem demonstrates excellent therapeutic efficacy against A. baumannii at imipenem concentrations of 10 mg/kg, and it can inhibit inflammatory reaction and local leukocyte infiltration. Due to its biocompatibility and biosafety, this nano-delivery system is a promising therapeutic strategy in the clinical treatment of A. baumannii infections, providing a new direction for the treatment of antibacterial infections.

Efficacy and safety of piperacillin-tazobactam compared with meropenem in treating complicated urinary tract infections including acute pyelonephritis due to extended-spectrum β-lactamase-producing Enterobacteriaceae

Introduction

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae pose a huge threat to human health, especially in the context of complicated urinary tract infections (cUTIs). Carbapenems and piperacillin-tazobactam (PTZ) are two antimicrobial agents commonly used to treat cUTIs.

Methods

A monocentric retrospective cohort study focused on the treatment of cUTIs in adults was conducted from January 2019 to November 2021. Patients with a positive urine culture strain yielding ≥ 103 colony-forming units per milliliter (CFU/mL), and sensitive to PTZ and carbapenems, were included. The primary endpoint was clinical success after antibiotic therapy. The secondary endpoint included rehospitalization and 90-day recurrence of cUTIs caused by ESBL-producing Enterobacteriaceae.

Results

Of the 195 patients included in this study, 110 were treated with PTZ while 85 were administered meropenem. The rate of clinical cure was similar between the PTZ and meropenem groups (80% vs. 78.8%, p = 0.84). However, the PTZ group had a lower duration of total antibiotic use (6 vs. 9; p < 0.01), lower duration of effective antibiotic therapy (6 vs. 8; p < 0.01), and lower duration of hospitalization (16 vs. 22; p < 0.01).

Discussion

In terms of adverse events, the safety of PTZ was higher than that of meropenem in the treatment of cUTIs.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii with Special Reference to Carbapenemases: A Systematic Review

Carbapenemases are β-lactamase enzymes that hydrolyze a variety of β-lactams including carbapenem and belong to different Ambler classes (A, B, D). These enzymes can be encoded by plasmid or chromosomal-mediated genes. The major issues associated with carbapenemases-producing organisms are compromising the activity and increasing the resistance to carbapenems which are the last resort antibiotics used in treating serious infections. The global increase of pathogen, carbapenem-resistant A. baumannii has significantly threatened public health. Thus, there is a pressing need for a better understanding of this pathogen, to know the various carbapenem resistance encoding genes and dissemination of resistance genes from A. baumannii which help in developing strategies to overcome this problem. The horizontal transfer of resistant determinants through mobile genetic elements increases the incidence of multidrug, extensive drug, and Pan-drug resistant A. baumannii. Therefore, the current review aims to know the various mechanisms of carbapenem resistance, categorize and discuss carbapenemases encoding genes and various mobile genetic elements, and the prevalence of carbapenemase genes in recent years in A. baumannii from various geographical regions.

Cerebrospinal fluid concentrations of fluoroquinolones and carbapenems in tuberculosis meningitis

Background: Tuberculosis meningitis (TBM) is the most lethal form of TB. It is difficult to treat in part due to poor or uncertain drug penetration into the central nervous system (CNS). To help fill this knowledge gap, we evaluated the cerebrospinal fluid (CSF) concentrations of fluoroquinolones and carbapenems in patients being treated for TBM. Methods: Serial serum and CSF samples were collected from hospitalized patients being treated for TBM. CSF was collected from routine lumbar punctures between alternating timepoints of 2 and 6 h after drug administration to capture early and late CSF penetration. Rich serum sampling was collected after drug administration on day 28 for non-compartmental analysis. Results: Among 22 patients treated for TBM (8 with confirmed disease), there was high use of fluoroquinolones (levofloxacin, 21; moxifloxacin, 10; ofloxacin, 6) and carbapenems (imipenem, 11; meropenem, 6). Median CSF total concentrations of levofloxacin at 2 and 6 h were 1.34 mg/L and 3.36 mg/L with adjusted CSF/serum ratios of 0.41 and 0.63, respectively. For moxifloxacin, the median CSF total concentrations at 2 and 6 h were 0.78 mg/L and 1.02 mg/L with adjusted CSF/serum ratios of 0.44 and 0.62. Serum and CSF concentrations of moxifloxacin were not affected by rifampin use. Among the 76 CSF samples measured for carbapenem concentrations, 79% were undetectable or below the limit of detection. Conclusion: Fluoroquinolones demonstrated high CSF penetration indicating their potential usefulness for the treatment of TBM. Carbapenems had lower than expected CSF concentrations.

Topographical and Ultrastructural Evaluation of Titanium Plates Coated with PLGA, Chitosan, and/or Meropenem: An In Vitro Study

The present investigation was undertaken to evaluate the topographical and ultrastructural architecture of titanium plates coated with polylactic co-glycolic acid (PLGA), chitosan (CH), and/or meropenem (MEM) with or without Staphylococcus aureus (SA) or Pseudomonas aeruginosa (PA) bacteria. Single-hole segments of 0.4 mm thick, low-profile titanium plates were spray coated using an airbrush with polymeric carriers (PLGA or CH) loaded with MEM, in addition to the negative control group (uncoated titanium plates). The coated plates and the negative control group were subjected to bacterial biofilms through a cultivation process while being slowly stirred at 20 rpm for 24 h. The samples were fixed and processed for scanning electron microscopic study at 5, 10, and 20 k magnification. The data were statistically analyzed to compare within and between the different materials. Coating titanium plates with PLGA or CH with MEM appeared to enhance bacterial inhibition over uncoated plates, hindering biofilm formation and preventing bacterial proliferation. In the staphylococcus aureus group, the highest bacterial count was observed in the uncoated plates, whereas the lowest count was detected in meropenem-PLGA, followed by PLGA, chitosan, meropenem, and meropenem-chitosan, respectively. On the other hand, the Pseudomonas aeruginosa group with the uncoated plates had the highest bacterial count, whereas the lowest bacterial count was found related to CH, followed by PLGA, MP, MC, and MEM, respectively.

Evaluation of In Vitro Activity of Double-Carbapenem Combinations against KPC-2-, OXA-48- and NDM-Producing Escherichia coli and Klebsiella pneumoniae

Double-carbapenem combinations have shown synergistic potential against carbapenemase-producing Enterobacterales, but data remain inconclusive. This study evaluated the activity of double-carbapenem combinations against 51 clinical KPC-2-, OXA-48-, NDM-1, and NDM-5-producing Escherichia coli and Klebsiella pneumoniae and against constructed E. coli strains harboring genes encoding KPC-2, OXA-48, or NDM-1 in an otherwise isogenic background. Two-drug combinations of ertapenem, meropenem, and doripenem were evaluated in 24 h time-lapse microscopy experiments with a subsequent spot assay and in static time-kill experiments. An enhanced effect in time-lapse microscopy experiments at 24 h and synergy in the spot assay was detected with one or more combinations against 4/14 KPC-2-, 17/17 OXA-48-, 2/17 NDM-, and 1/3 NDM-1+OXA-48-producing clinical isolates. Synergy rates were higher against meropenem- and doripenem-susceptible isolates and against OXA-48 producers. NDM production was associated with significantly lower synergy rates in E. coli. In time-kill experiments with constructed KPC-2-, OXA-48- and NDM-1-producing E. coli, 24 h synergy was not observed; however, synergy at earlier time points was found against the KPC-2- and OXA-48-producing constructs. Our findings indicate that the benefit of double-carbapenem combinations against carbapenemase-producing E. coli and K. pneumoniae is limited, especially against isolates that are resistant to the constituent antibiotics and produce NDM.

A nomogram for predicting the risk of mortality in patients with acute pancreatitis and Gram-negative bacilli infection

OBJECTIVE

Gram-negative bacilli (GNB) are common pathogens of infection in severe acute pancreatitis (SAP), and their occurrence increases the mortality of SAP. Early identification of SAP severity and prognosis is of great significance to SAP treatment. This study explored risk factors for mortality in patients with SAP and GNB infection and established a model for early prediction of the risk of death in GNB-infected SAP patients.

METHODS

Patients diagnosed with SAP from January 1, 2016, to March 31, 2022, were included, and their baseline clinical characteristics were collected. Univariate logistic regression analysis was performed to screen for death related variables, and concurrently, a Boruta analysis was performed to identify potentially important clinical features associated with mortality. The intersection of the two results was taken for further multivariate logistic regression analysis. A logistic regression model was constructed according to the independent risk factor of death and then visualized with a nomogram. The performance of the model was further validated in the training and validation cohort.

RESULTS

A total of 151 patients with SAP developed GNB infections. Univariate logistic regression analysis identified 11 variables associated with mortality. The Boruta analysis identified 11 clinical features, and 4 out of 9 clinical variables: platelet counts (odds ratio [OR] 0.99, 95% confidence interval [CI] 0.99-1.00; p = 0.007), hemoglobin (OR 0.96, 95% CI 0.92-1; p = 0.037), septic shock (OR 6.33, 95% CI 1.12-43.47; p = 0.044), and carbapenem resistance (OR 7.99, 95% CI 1.66-52.37; p = 0.016), shared by both analyses were further selected as independent risk factors by multivariate logistic regression analysis. A nomogram was used to visualize the model. The model demonstrated good performance in both training and validation cohorts with recognition sensitivity and specificity of 96% and 80% in the training cohort and 92.8% and 75% in the validation cohort, respectively.

CONCLUSION

The nomogram can accurately predict the mortality risk of patients with SAP and GNB infection. The clinical application of this model allows early identification of the severity and prognosis for patients with SAP and GNB infection and identification of patients requiring urgent management thus allowing rationalization of treatment options and improvements in clinical outcomes.

Epidemiology of carbapenem-resistant Klebsiella pneumoniae ST15 of producing KPC-2, SHV-106 and CTX-M-15 in Anhui, China

Background:

It is well known that carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a more problematic public health issue due to its widespread spread worldwide. In China, ST11-type CRKP is the most prevalent CRKP, but ST15-type CRKP, a recently prevalent high-risk clone, has emerged widely throughout China, posing a serious public health risk. Therefore, we conducted an epidemiological of an outbreak of ST15 CRKP of producing CTX-M-15, KPC-2 and SHV-106 in a tertiary hospital in Anhui, China, to Understanding the potential risks of the current STT15 CRKP outbreak.

Results:

From July 2021 to December 2021, 13 ST15 CRKP isolates were identified by collecting non-repeated clinical multidrug-resistant isolates, with all capsular typing of serotype KL19. All ST15 CRKP isolates were resistant to cephalosporins, carbapenems and quinolones, but were sensitive to amikacin, tigecycline and polymyxin B. In addition, isolates carried bla_SHV−106 (100%), bla_KPC−2 (69%), bla_CTX−M−15 (69%), bla_TEM−1B (69%), bla_OXA−1 (62%) and bla_LAP−2 (8%), as well as iron chelators (iutA, ybt, fyuA, ent, fepA, irp1, irp2, 100%) were detected. In phenotyping experiments, all ST15 CRKP exhibited lower growth rates than NTUH-K2044, and all ST15 CRKP did not exhibit mucoviscositty characteristics. However, in the Galleria mellonella infection model, isolates 21081212, 21081241 and 21091216 were more lethal than the hypervirulent isolates NTUH-K2044. Sequencing results showed that the genetic environment surrounding the genes bla_SHV−106, bla_KPC−2, bla_CTX−M−15, bla_OXA−1 and bla_TEM−1B were all identical in the ST15 CRKP isolates. Phylogenetic analysis showed that 13 ST15 CRKP isolates were divided into three subgroups, and when placed in global analysis, 10 of them were highly homologous to isolates from Jiangsu, two were highly homologous to isolates from Zhejiang, and one was homologous to an isolate from an unlabelled region.

Conclusion:

Our research shows that ST15 CRKP, which carries multiple β-lactamases genes and siderophores-encoding genes, may be evolving to hypervirulence and may have spread widely in localised areas. Therefore, environmental surveillance and clinical infection control in hospitals should be strengthened to prevent further spread of ST15 CRKP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02672-1.