A resurgence of β-lactamase inhibitor combinations effective against multidrug-resistant Gram-negative pathogens

Transmission Dynamics and Novel Treatments of High Risk Carbapenem-Resistant Klebsiella pneumoniae: The Lens of One Health

The rise of antibiotic resistance and the dwindling antimicrobial pipeline have emerged as significant threats to public health. The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a global threat, with limited options available for targeted therapy. The CRKP has experienced various changes and discoveries in recent years regarding its frequency, transmission traits, and mechanisms of resistance. In this comprehensive review, we present an in-depth analysis of the global epidemiology of K. pneumoniae, elucidate resistance mechanisms underlying its spread, explore evolutionary dynamics concerning carbapenem-resistant hypervirulent strains as well as KL64 strains of K. pneumoniae, and discuss recent therapeutic advancements and effective control strategies while providing insights into future directions. By going through up-to-date reports, we found that the ST11 KL64 CRKP subclone with high risk demonstrated significant potential for expansion and survival benefits, likely due to genetic influences. In addition, it should be noted that phage and nanoparticle treatments still pose significant risks for resistance development; hence, innovative infection prevention and control initiatives rooted in One Health principles are advocated as effective measures against K. pneumoniae transmission. In the future, further imperative research is warranted to comprehend bacterial resistance mechanisms by focusing particularly on microbiome studies' application and implementation of the One Health strategy.

Approachable Synthetic Methodologies for Second-Generation β-Lactamase Inhibitors: A Review

Some antibiotics that are frequently employed are β-lactams. In light of the hydrolytic process of β-lactamase, found in Gram-negative bacteria, inhibitors of β-lactamase (BLIs) have been produced. Examples of first-generation β-lactamase inhibitors include sulbactam, clavulanic acid, and tazobactam. Many kinds of bacteria immune to inhibitors have appeared, and none cover all the β-lactamase classes. Various methods have been utilized to develop second-generation β-lactamase inhibitors possessing new structures and facilitate the formation of diazabicyclooctane (DBO), cyclic boronate, metallo-, and dual-nature β-lactamase inhibitors. This review describes numerous promising second-generation β-lactamase inhibitors, including vaborbactam, avibactam, and cyclic boronate serine-β-lactamase inhibitors. Furthermore, it covers developments and methods for synthesizing MβL (metallo-β-lactamase inhibitors), which are clinically effective, as well as the various dual-nature-based inhibitors of β-lactamases that have been developed. Several combinations are still only used in preclinical or clinical research, although only a few are currently used in clinics. This review comprises materials on the research progress of BLIs over the last five years. It highlights the ongoing need to produce new and unique BLIs to counter the appearance of multidrug-resistant bacteria. At present, second-generation BLIs represent an efficient and successful strategy.

Structural insight into the subclass B1 metallo-β-lactamase AFM-1

The emergence of drug-resistant bacteria, facilitated by metallo-beta-lactamases (MBLs), presents a significant obstacle to the effective use of antibiotics in the management of clinical drug-resistant bacterial infections. AFM-1 is a MBL derived from Alcaligenes faecalis and shares 86% homology with the NDM-1 family. Both AFM-1 and NDM-1 demonstrate the ability to hydrolyze ampicillin and other β-lactam antibiotics, however, their substrate affinities vary, and the specific reason for this variation remains unknown. We present the high-resolution structure of AFM-1. The active center of AFM-1 binds two zinc ions, and the conformation of the key amino acid residues in the active center is in accordance with that of NDM-1. However, the substrate-binding pocket of AFM-1 is considerably smaller than that of NDM-1. Additionally, the mutation of amino acid residues in the Loop3 region, as compared to NDM-1, results in the formation of a dense hydrophobic patch comprised of hydrophobic amino acid residues in this area, which facilitates substrate binding. Our findings lay the foundation for understanding the molecular mechanism of AFM-1 with a high affinity for substrates and provide a novel theoretical foundation for addressing the issue of drug resistance caused by B1 MBLs.

In vitro pharmacokinetics/pharmacodynamics of FL058 (a novel beta-lactamase inhibitor) combined with meropenem against carbapenemase-producing Enterobacterales

Objective: FL058 is a novel beta-lactamase inhibitor with a broad spectrum of activity and a favorable safety profile. The objective of this study was to evaluate pharmacokinetic/pharmacodynamic (PK/PD) relationships for the combination of FL058 and meropenem in an in vitro infection model. Methods: By simulating human concentration-time profiles in the in vitro model, meropenem combined with FL058 when administered 1 g/0.5 g, 1 g/1 g, 2 g/1 g, and 2 g/2 g q8h by 3-h infusion achieved approximately 2- and 4-log10 kill to KPC/OXA-producing Klebsiella pneumoniae and Escherichia coli; the combination therapy could not inhibit NDM-producing K. pneumoniae but could maintain NDM-producing E. coli around a baseline. Results: The PK/PD indexes that best described the bacterial killing from baseline in log10 CFU/mL at 24 h were the percent time of free drug above the minimal inhibitory concentration (MIC) (%fT > MIC, MIC with FL058 at 4 mg/L) for meropenem and the percent time of free drug above 1 mg/L (%fT > 1 mg/L) for FL058. The targets for achieving a static effect and the 1- and 2-log10 kill were 74, 83, and 99 for %fT > MIC of meropenem and 40, 48, and 64 for %fT > 1 mg/L of FL058, respectively. The PK/PD index of %fT > 1 mg/L can provide a basis for evaluating clinical dosing regimens for FL058 combined with meropenem. Conclusion: FL058 combined with meropenem might be a potential treatment for KPC- and/or OXA-48-producing Enterobacterales infection.

Worldwide trend discovery of structural and functional relationship of metallo-β-lactamase for structure-based drug design: A bibliometric evaluation and patent analysis

Metallo-β-lactamase (MBL) is an enzyme produced by clinically important bacteria that can inactivate many commonly used antibiotics, making them a significant concern in treating bacterial infections and the risk of having high antibiotic resistance issues among the community. This review presents a bibliometric and patent analysis of MBL worldwide research trend based on the Scopus and World Intellectual Property Organization databases in 2013-2022. Based on the keywords related to MBL in the article title, abstract, and keywords, 592 research articles were retrieved for further analysis using various tools such as Microsoft Excel to determine the frequency analysis, VOSviewer for bibliometric networks visualization, and Harzing's Publish or Perish for citation metrics analysis. Standard bibliometric parameters were analysed to evaluate the field's research trend, such as the growth of publications, topographical distribution, top subject area, most relevant journal, top cited documents, most relevant authors, and keyword trend analysis. Within 10 years, MBL discovery has shown a steady and continuous growth of interest among the community of researchers. United States of America, China, and the United Kingdom are the top 3 countries contribute high productivity to the field. The patent analysis also shows several impactful filed patents, indicating the significance of development research on the structural and functional relationship of MBL for an effective structure-based drug design (SBDD). Developing new MBL inhibitors using SBDD could help address the research gap and provide new successful therapeutic options for treating MBL-producing bacterial infections.

Dissecting bloodstream infections in febrile neutropenic patients with hematological malignancies, a decade-long single center retrospective observational study (2009-2019)

BACKGROUND

The use of ill-suited antibiotics is a significant risk factor behind the increase in the mortality, morbidity, and economic burden for patients who are under treatment for hematological malignancy (HM) and bloodstream infections (BSI). Such unfitting treatment choices intensify the evolution of resistant variants which is a public health concern due to possible healthcare-associated infection spread to the general population. Hence, this study aims to evaluate antibiograms of patients with BSI and risk factors associated with septicemia.

METHODS

A total of 1166 febrile neutropenia episodes (FNE) among 513 patients with HM from the National Center for Cancer Care and Research (NCCCR), Qatar, during 2009-2019 were used for this study. The socio-demographic, clinical, microbial, and anti-microbial data retrieved from the patient's health records were used.

RESULTS

We analyzed the sensitivity of gram-negative and gram-positive bacilli reported in HM-FN-BSI patients. Out of the total 512 microorganisms isolated, 416 (81%) were gram-negative bacteria (GNB), 76 (15%) were gram-positive bacteria (GPB) and 20 (4%) were fungi. Furthermore, in 416 GNB, 298 (71.6%) were Enterobacteriaceae sp. among which 121 (41%) were ESBL (Extended Spectrum Beta-Lactamase) resistant to Cephalosporine third generation and Piperacillin-Tazobactam, 54 (18%) were Carbapenem-resistant or multidrug-resistant organism (MDRO). It's noteworthy that the predominant infectious agents in our hospital include E. coli, Klebsiella species, and P. aeruginosa. Throughout the study period, the mortality rate due to BSI was 23%. Risk factors that show a significant correlation with death are age, disease status, mono or polymicrobial BSI and septic shock.

CONCLUSION

Decision pertaining to the usage of antimicrobials for HM-FN-BSI patients is a critical task that relies on the latest pattern of prevalence, treatment resistance, and clinical outcomes. Analysis of the antibiogram of HM-FN-BSI patients in Qatar calls for a reconsideration of currently followed empirical antibiotic therapy towards better infection control and antimicrobial stewardship.

Repurposing FDA approved drug molecules against A B C classes of β-lactamases: a computational biology and molecular dynamics simulations study

β-lactamase are the main resistance factor for β-lactam antibiotics in Gram-negative bacteria. Since β-lactam antibiotics are being utilised as an antimicrobial agents extensively for the past 70 years, a large number of β-lactam-inactivating β-lactamases have been produced by bacteria. Here, we employed a structure-based drug discovery approach to identify and assess the efficacy of a potential medication that might block the β-lactamases which hydrolyse antibiotics. The FDA-approved medications were subjected to virtual screening, molecular docking, molecular dynamics simulations, density functional theory, and covalent docking against the β-lactamases. We identified diosmin, hidrosmin, monoxuritin and solasulfone as β-lactamase inhibitors which are authorised for therapeutic use in humans. These medications interact in a remarkable variety of non-covalent ways with the conserved residues in the substrate-binding pocket of the β-lactamases. Diosmin has been identified as an inhibitor that binds covalently to the NDM-1 a class B metallo-betalactamase. After experimental validation and clinical demonstration, this study offers adequate evidence for the therapeutic use of these drugs for controlling multidrug resistance.Communicated by Ramaswamy H. Sarma.

Comparative efficacy and safety of non-polymyxin antibiotics against nosocomial pneumonia, complicated intra-abdominal infection, or complicated urinary tract infection: A network meta-analysis of randomised clinical trials

OBJECTIVES

The increasing epidemic of infections caused by drug-resistant Gram-negative bacteria has led to the development of several antibiotic therapies. Owing to the scarcity of head-to-head comparisons of current and emerging antibiotics, the present network meta-analysis aimed to compare the efficacy and safety of antibiotics in patients with nosocomial pneumonia, complicated intra-abdominal infection, or complicated urinary tract infection.

METHODS

Two independent researchers systematically searched databases up to August 2022 and included 26 randomised controlled trials that fulfilled the inclusion criteria. The protocol was registered in the Prospective Register of Systematic Reviews, PROSPERO (CRD42021237798). The frequentist random effects model (R version 3.5.1, netmeta package) was utilized. The DerSimonian-Laird random effects model was used to estimate heterogeneity. The calculated P-score was applied to rank the interventions. Additionally, inconsistencies, publication bias, and subgroup effects were assessed in the present study to avoid bias.

RESULTS

There was no significant difference among included antibiotics in terms of clinical response and mortality, probably because most antibiotic trials were designed to be non-inferior. In terms of P-score ranking, carbapenems may be the recommended choice considering both adverse events and clinical responses. On the other hand, for carbapenem-sparing options, ceftolozane-tazobactam was the preferred antibiotic for nosocomial pneumonia; eravacycline, for complicated intra-abdominal infection; and cefiderocol, for complicated urinary tract infection.

CONCLUSION

Carbapenems may be preferable options in terms of safety and efficacy for the treatment of Gram-negative bacterial complicated infections. However, to preserve the effectiveness of carbapenems, it is important to consider carbapenem-sparing regimens.

Efficacy of Novel Combinations of Antibiotics against Multidrug-Resistant-New Delhi Metallo-Beta-Lactamase-Producing Strains of Enterobacterales

The emergence of multidrug-resistance (MDR)-New Delhi metallo-beta-lactamase (NDM)-producing microorganisms-has become a serious concern for treating such infections. Therefore, we investigated the effective antimicrobial combinations against multidrug-resistant New Delhi metallo-beta-lactamase-producing strains of Enterobacterales. The tests were carried out using the 2D(two-dimensional) checkerboard method. Of 7 antimicrobials, i.e., doripenem (DRP), streptomycin (STR), cefoxitin (FOX), imipenem (IPM), cefotaxime (CTX), meropenem (MER), and gentamicin (GEN), 19 different combinations were used, and out of them, three combinations showed synergistic effects against 31 highly drug-resistant strains carrying bla_NDM and other associated resistance markers. Changes in the minimum inhibitory concentration (MIC) values were interpreted using the test fractional inhibitory concentration index (FIC Index). The FIC Index values of these combinations were found in the range of 0.1562 to 0.5, which shows synergy, whereas no synergism was observed in the remaining antimicrobial combinations. We conclude that these antibiotic combinations can be analyzed in in vivo and pharmacological studies to establish an effective therapeutic approach.

Serotypes, Antimicrobial Resistance Profiles, and Virulence Factors of Salmonella Isolates in Chinese Edible Frogs (Hoplobatrachus rugulosus) Collected from Wet Markets in Hong Kong

Salmonella is an important agent of gastrointestinal disease in humans. While livestock, such as cattle, poultry, and pigs, are well-recognised animal reservoirs of Salmonella, there is a lack of data on Salmonella in edible frogs, even though frog meat is a popular food worldwide. In this study, 103 live edible Chinese frogs (Hoplobatrachus rugulosus) were collected from wet markets throughout Hong Kong. After euthanasia, faeces or cloacal swabs were examined for Salmonella. Overall, Salmonella spp. were isolated from 67 (65%, CI: 0.554-0.736) of the samples. The serotypes included S. Saintpaul (33%), S. Newport (24%), S. Bareilly (7%), S. Braenderup (4%), S. Hvittingfoss (4%), S. Stanley (10%), and S. Wandsworth (16%). Many isolates were phylogenetically related. A high number of genes encoding for resistance to clinically relevant antimicrobials, and a high number of virulence determinants, were identified. Antimicrobial susceptibility testing (AST) identified multidrug resistance (MDR) in 21% of the isolates. Resistance to ampicillin, ciprofloxacin, nalidixic acid, and tetracycline was common. These results demonstrate that a high percentage of live frogs sold for human consumption in wet markets are carriers of multidrug-resistant Salmonella. Public health recommendations for handling edible frogs should be considered, to mitigate the risk of Salmonella transmission to humans.

β-Lactam potentiators to re-sensitize resistant pathogens: Discovery, development, clinical use and the way forward

β-lactam antibiotics are one of the most widely used and diverse classes of antimicrobial agents for treating both Gram-negative and Gram-positive bacterial infections. The β-lactam antibiotics, which include penicillins, cephalosporins, monobactams and carbapenems, exert their antibacterial activity by inhibiting the bacterial cell wall synthesis and have a global positive impact in treating serious bacterial infections. Today, β-lactam antibiotics are the most frequently prescribed antimicrobial across the globe. However, due to the widespread use and misapplication of β-lactam antibiotics in fields such as human medicine and animal agriculture, resistance to this superlative drug class has emerged in the majority of clinically important bacterial pathogens. This heightened antibiotic resistance prompted researchers to explore novel strategies to restore the activity of β-lactam antibiotics, which led to the discovery of β-lactamase inhibitors (BLIs) and other β-lactam potentiators. Although there are several successful β-lactam-β-lactamase inhibitor combinations in use, the emergence of novel resistance mechanisms and variants of β-lactamases have put the quest of new β-lactam potentiators beyond precedence. This review summarizes the success stories of β-lactamase inhibitors in use, prospective β-lactam potentiators in various phases of clinical trials and the different strategies used to identify novel β-lactam potentiators. Furthermore, this review discusses the various challenges in taking these β-lactam potentiators from bench to bedside and expounds other mechanisms that could be investigated to reduce the global antimicrobial resistance (AMR) burden.

Recent Approaches for Downplaying Antibiotic Resistance: Molecular Mechanisms

Antimicrobial resistance (AMR) is a ubiquitous public health menace. AMR emergence causes complications in treating infections contributing to an upsurge in the mortality rate. The epidemic of AMR in sync with a high utilization rate of antimicrobial drugs signifies an alarming situation for the fleet recovery of both animals and humans. The emergence of resistant species calls for new treatments and therapeutics. Current records propose that health drug dependency, veterinary medicine, agricultural application, and vaccination reluctance are the primary etymology of AMR gene emergence and spread. Recently, several encouraging avenues have been presented to contest resistance, such as antivirulent therapy, passive immunization, antimicrobial peptides, vaccines, phage therapy, and botanical and liposomal nanoparticles. Most of these therapies are used as cutting-edge methodologies to downplay antibacterial drugs to subdue the resistance pressure, which is a featured motive of discussion in this review article. AMR can fade away through the potential use of current cutting-edge therapeutics, advancement in antimicrobial susceptibility testing, new diagnostic testing, prompt clinical response, and probing of new pharmacodynamic properties of antimicrobials. It also needs to promote future research on contemporary methods to maintain host homeostasis after infections caused by AMR. Referable to the microbial ability to break resistance, there is a great ultimatum for using not only appropriate and advanced antimicrobial drugs but also other neoteric diverse cutting-edge therapeutics.

A Visualized Mortality Prediction Score Model in Hematological Malignancies Patients with Carbapenem-Resistant Organisms Bloodstream Infection

Background

Bloodstream infection (BSI) due to carbapenem-resistant organisms (CROs) has emerged as a worldwide problem associated with high mortality. This study aimed to evaluate the risk factors associated with mortality in HM patients with CROs BSI and to establish a scoring model for early mortality prediction.

Methods

We conducted a retrospective cohort study at our hematological department from January 2018 to December 2021, including all HM patients with CROs BSI. The outcome measured was death within 30-day of BSI onset. Survivor and non-survivor subgroups were compared to identify predictors of mortality. Univariate and multivariate Cox regression analyses were used to identify prognostic risk factors and develop a nomogram.

Results

In total, 150 HM patients were included in the study showing an overall 30-day mortality rate of 56%. Klebsiella pneumonia was the dominant episode. Cox regression analysis showed that pre-infection length of stay was >14 days (score 41), Pitt score >4 (score 100), mucositis (score 41), CAR (The ratio of C-reactive protein to albumin) >8.8 (score 57), early definitive therapy (score 44), and long-duration (score 78) were positive independent risk predictors associated with 30-day mortality, all of which were selected into the nomogram. Furthermore, all patients were divided into the high-risk group (≥160 points) or the low-risk group based on the prediction score model. The mortality of the high-risk group was 8 times more than the low-risk group. Kaplan-Meier analysis showed that empirical polymyxin B therapy was associated with a lower 30-day mortality rate, which was identified as a good prognostic factor in the high-risk group. In comparison, empirical carbapenems and tigecycline were poor prognostic factors in a low-risk group.

Conclusion

Our score model can accurately predict 30-day mortality in HM patients with CROs BSI. Early administration of CROs-targeted therapy in the high-risk group is strongly recommended to decrease mortality.

Fighting antibiotic resistance-strategies and (pre)clinical developments to find new antibacterials

Antibacterial resistance is one of the greatest threats to human health. The development of new therapeutics against bacterial pathogens has slowed drastically since the approvals of the first antibiotics in the early and mid-20^th century. Most of the currently investigated drug leads are modifications of approved antibacterials, many of which are derived from natural products. In this review, we highlight the challenges, advancements and current standing of the clinical and preclinical antibacterial research pipeline. Additionally, we present novel strategies for rejuvenating the discovery process and advocate for renewed and enthusiastic investment in the antibacterial discovery pipeline.

The role of adjuvants in overcoming antibacterial resistance due to enzymatic drug modification

Antibacterial resistance is a prominent issue with monotherapy often leading to treatment failure in serious infections. Many mechanisms can lead to antibacterial resistance including deactivation of antibacterial agents by bacterial enzymes. Enzymatic drug modification confers resistance to β-lactams, aminoglycosides, chloramphenicol, macrolides, isoniazid, rifamycins, fosfomycin and lincosamides. Novel enzyme inhibitor adjuvants have been developed in an attempt to overcome resistance to these agents, only a few of which have so far reached the market. This review discusses the different enzymatic processes that lead to deactivation of antibacterial agents and provides an update on the current and potential enzyme inhibitors that may restore bacterial susceptibility.

Clinical carbapenem-resistant Klebsiella pneumoniae isolates simultaneously harboring blaNDM-1, blaOXA types and qnrS genes from the Kingdom of Bahrain: Resistance profile and genetic environment

The prevalence of Carbapenem-resistant Klebsiella pneumoniae (CRKP) is currently increasing worldwide, prompting WHO to classify it as an urgent public health threat. CRKP is considered a difficult to treat organism owing to limited therapeutic options. In this study, a total of 24 CRKP clinical isolates were randomly collected from Salmaniya Medical Complex, Bahrain. Bacterial identification and antibiotic susceptibility testing were performed, on MALDI-TOF and VITEK-2 compact, respectively. The isolates were screened for carbapenem resistance markers (bla_NDM,bla_OXA-23,bla_OXA-48 and bla_OXA-51) and plasmid-mediated quinolone resistance genes (qnrA, qnrB, and qnrS) by monoplex PCR. On the other hand, only colistin-resistant isolates (n=12) were screened for MCR-1, MCR-2 and MCR-3 genes by monoplex PCR. Moreover, the Genetic environment of bla_NDM, integrons analysis, and molecular characterization of plasmids was also performed. Antibiotic susceptibility revealed that all the isolates (100%) were resistant to ceftolozane/tazobactam, piperacillin/tazobactam, 96% resistant to ceftazidime, trimethoprim/sulfamethoxazole, 92% resistant to meropenem, gentamicin and cefepime, 88% resistant to ciprofloxacin, imipenem, and 37% resistant to amikacin. Ceftazidime/avibactam showed the least resistance (12%). 75% (n=12/16) were resistant to colistin and 44% (n=7/16) showed intermediate susceptibility to tigecycline. The detection of resistant determinants showed that the majority (95.8%) of CRKP harbored bla_NDM-1, followed by bla_OXA-48 (91.6%) bla_OXA-51 (45.8%), and bla_OXA-23 (41.6%). Sequencing of the bla_NDM amplicons revealed the presence of bla_NDM-1. Alarmingly, 100% of isolates showed the presence of qnrS. These predominant genes were distributed in various combinations wherein the majority were bla_NDM-1 + bla_OXA-51+ qnrS + bla_OXA-48 (n =10, 41.7%), bla_NDM-1 + bla_OXA-23+ qnrS + bla_OXA-48 (n=8, 33.3%), among others. In conclusion, the resistance rate to most antibiotics is very high in our region, including colistin and tigecycline, and the genetic environment of CRKP is complex with the carriage of multiple resistance markers. Resistance to ceftazidime/avibactam is uncommon and hence can be used as a valuable option for empirical therapy. Molecular data on resistance markers and the genetic environment of CRKP is lacking from this geographical region; this would be the first report addressing the subject matter. Surveillance and strict infection control strategies should be reinforced in clinical settings to curb the emergence and spread of such isolates.

Mutation of PA4292 in Pseudomonas aeruginosa Increases β-Lactam Resistance through Upregulating Pyocyanin Production

Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is increasingly reported worldwide and usually causes infections with high mortality rates. Aztreonam/avibactam is a β-lactam/β-lactamase inhibitor (BLBLI) combination that is under clinical trials. The advantage of aztreonam/avibactam over the currently used BLBLIs lies in its effectiveness against MBL-producing pathogens, making it one of the few drugs that can be used to treat infections caused by MBL-producing P. aeruginosa. However, the molecular mechanisms underlying aztreonam/avibactam resistance development remain unexplored. Here, in this study, we performed an in vitro evolution assay by using a previously identified MBL-producing P. aeruginosa clinical isolate, NKPa-71, and found mutations in a novel gene, PA4292, in the aztreonam/avibactam-resistant mutants. By mutation of PA4292 in the reference strain PA14, we verified the role of PA4292 in the resistance to aztreonam/avibactam and β-lactams. Transcriptomic analyses revealed upregulation of pyocyanin biosynthesis genes among the most overexpressed in the PA4292 mutant. We further demonstrated that pyocyanin overproduction in the PA4292 mutant increased the bacterial resistance to β-lactams by reducing drug influx. These data revealed a novel mechanism that might lead to the development of resistance to aztreonam/avibactam and β-lactams.

Recent Developments to Cope the Antibacterial Resistance via β-Lactamase Inhibition

Antibacterial resistance towards the β-lactam (BL) drugs is now ubiquitous, and there is a major global health concern associated with the emergence of new β-lactamases (BLAs) as the primary cause of resistance. In addition to the development of new antibacterial drugs, β-lactamase inhibition is an alternative modality that can be implemented to tackle this resistance channel. This strategy has successfully revitalized the efficacy of a number of otherwise obsolete BLs since the discovery of the first β-lactamase inhibitor (BLI), clavulanic acid. Over the years, β-lactamase inhibition research has grown, leading to the introduction of new synthetic inhibitors, and a few are currently in clinical trials. Of note, the 1, 6-diazabicyclo [3,2,1]octan-7-one (DBO) scaffold gained the attention of researchers around the world, which finally culminated in the approval of two BLIs, avibactam and relebactam, which can successfully inhibit Ambler class A, C, and D β-lactamases. Boronic acids have shown promise in coping with Ambler class B β-lactamases in recent research, in addition to classes A, C, and D with the clinical use of vaborbactam. This review focuses on the further developments in the synthetic strategies using DBO as well as boronic acid derivatives. In addition, various other potential serine- and metallo- β-lactamases inhibitors that have been developed in last few years are discussed briefly as well. Furthermore, binding interactions of the representative inhibitors have been discussed based on the crystal structure data of inhibitor-enzyme complex, published in the literature.

Extraintestinal Pathogenic Escherichia coli: Beta-Lactam Antibiotic and Heavy Metal Resistance

Multiple-antibiotic-resistant (MAR) extra-intestinal pathogenic Escherichia coli (ExPEC) represents one of the most frequent causes of human nosocomial and community-acquired infections, whose eradication is of major concern for clinicians. ExPECs may inhabit indefinitely as commensal the gut of humans and other animals; from the intestine, they may move to colonize other tissues, where they are responsible for a number of diseases, including recurrent and uncomplicated UTIs, sepsis and neonatal meningitis. In the pre-antibiotic era, heavy metals were largely used as chemotherapeutics and/or as antimicrobials in human and animal healthcare. As with antibiotics, the global incidence of heavy metal tolerance in commensal, as well as in ExPEC, has increased following the ban in several countries of antibiotics as promoters of animal growth. Furthermore, it is believed that extensive bacterial exposure to heavy metals present in soil and water might have favored the increase in heavy-metal-tolerant microorganisms. The isolation of ExPEC strains with combined resistance to both antibiotics and heavy metals has become quite common and, remarkably, it has been recently shown that heavy metal resistance genes may co-select antibiotic-resistance genes. Despite their clinical relevance, the mechanisms underlining the development and spread of heavy metal tolerance have not been fully elucidated. The aim of this review is to present data regarding the development and spread of resistance to first-line antibiotics, such as beta-lactams, as well as tolerance to heavy metals in ExPEC strains.

Traceless Staudinger Ligation To Introduce Chemical Diversity on β-Lactamase Inhibitors of Second Generation

We explored the traceless Staudinger ligation for the functionalization of the C2 position of second generation β-lactamase inhibitors based on a diazabicyclooctane (DBO) scaffold. Our strategy is based on the synthesis of phosphine phenol esters and their ligation to an azido-containing precursor. Biological evaluation showed that this route provided access to a DBO that proved to be superior to commercial relebactam for inhibition of two of the five β-lactamases that were tested.

High-Throughput Crystallography Reveals Boron-Containing Inhibitors of a Penicillin-Binding Protein with Di- and Tricovalent Binding Modes

The effectiveness of β-lactam antibiotics is increasingly compromised by β-lactamases. Boron-containing inhibitors are potent serine-β-lactamase inhibitors, but the interactions of boron-based compounds with the penicillin-binding protein (PBP) β-lactam targets have not been extensively studied. We used high-throughput X-ray crystallography to explore reactions of a boron-containing fragment set with the Pseudomonas aeruginosa PBP3 (PaPBP3). Multiple crystal structures reveal that boronic acids react with PBPs to give tricovalently linked complexes bonded to Ser294, Ser349, and Lys484 of PaPBP3; benzoxaboroles react with PaPBP3 via reaction with two nucleophilic serines (Ser294 and Ser349) to give dicovalently linked complexes; and vaborbactam reacts to give a monocovalently linked complex. Modifications of the benzoxaborole scaffold resulted in a moderately potent inhibition of PaPBP3, though no antibacterial activity was observed. Overall, the results further evidence the potential for the development of new classes of boron-based antibiotics, which are not compromised by β-lactamase-driven resistance.

Imipenem-Relebactam Susceptibility and Genotypic Characteristics of Carbapenem-Resistant Enterobacterales (CRE) Identified during Population-Based Surveillance

Laboratories submit all carbapenem-resistant Enterobacter, Escherichia coli, and Klebsiella species to the Alameda County Public Health Department (ACPHD). ACPHD evaluated 75 isolates submitted during nine months for susceptibility to imipenem-relebactam (I-R) and identified β-lactamase genes using whole genome sequencing. Of 60 (80%) isolates susceptible to I-R, 8 (13%) had detectable carbapenemase genes, including four KPC, two NDM, and two OXA-48-like; we described the relationship between the presence of β-lactamase resistance genes and susceptibility to I-R.

Recent research and development of NDM-1 inhibitors

Bacteria carrying New Delhi metallo-β-lactamase-1 (New Delhi metallo-β-lactamase, NDM-1) resistance gene is a new type of "superbug", which can hydrolyze almost all β-lactam antibiotics, rapidly spread among the same species and even spread among different species. NDM-1 belongs to the class B1 broad-spectrum enzyme of β-lactamase. The two positively charged zinc ions in the active center have electrostatic interaction with the hydroxyl ions in them to seize the hydrogen atom near the water molecule to form a bridging ring water molecule, which strengthens its nucleophilicity and attacks the carbonyl group on the lactam ring; thus, catalyzing the hydrolysis of β-lactam antibiotics. Since NDM-1 has an open active site and unique electrostatic structure, it essentially provides a wider range of substrate specificity. Due to its flexible hydrolysis mechanism and more and more variants also aggravate the threat of drug-resistant bacteria infection, there is still no effective inhibitor in clinic, which is a serious threat to human health and public health safety. The electron-rich substituents of NDM-1 inhibitors coordinate with two positively charged zinc ions in the active center of the enzyme through ion-dipole interaction to produce NDM-1 inhibitory activity. In this review, the research progress of NDM-1 enzyme and its inhibitors in the past 5 years was reviewed. The crystal structure, active center structure, surrounding important amino acid residues, newly discovered inhibitors and their action mechanism are classified and summarized in detail, which can be used as a reference for the development of effective drugs against drug-resistant bacteria targeting NDM-1.

Cranberry-Derived Proanthocyanidins Potentiate β-Lactam Antibiotics against Resistant Bacteria

The emergence and spread of extended-spectrum β-lactamases (ESBLs), metallo-β-lactamases (MBLs), or variant low-affinity penicillin-binding proteins (PBPs) pose a major threat to our ability to treat bacterial infection using β-lactam antibiotics. Although combinations of β-lactamase inhibitors with β-lactam agents have been clinically successful, there are no MBL inhibitors in current therapeutic use. Furthermore, recent clinical use of new-generation cephalosporins targeting PBP2a, an altered PBP, has led to the emergence of resistance to these antimicrobial agents. Previous work shows that natural polyphenols such as cranberry-extracted proanthocyanidins (cPAC) can potentiate non-β-lactam antibiotics against Gram-negative bacteria. This study extends beyond previous work by investigating the in vitro effect of cPAC in overcoming ESBL-, MBL-, and PBP2a-mediated β-lactam resistance. The results show that cPAC exhibit variable potentiation of different β-lactams against β-lactam-resistant Enterobacteriaceae clinical isolates as well as ESBL- and MBL-producing E. coli We also discovered that cPAC have broad-spectrum inhibitory properties in vitro on the activity of different classes of β-lactamases, including CTX-M3 ESBL and IMP-1 MBL. Furthermore, we observe that cPAC selectively potentiate oxacillin and carbenicillin against methicillin-resistant but not methicillin-sensitive staphylococci, suggesting that cPAC also interfere with PBP2a-mediated resistance. This study motivates the need for future work to identify the most bioactive compounds in cPAC and to evaluate their antibiotic-potentiating efficacy in vivoIMPORTANCE The emergence of β-lactam-resistant Enterobacteriaceae and staphylococci compromises the effectiveness of β-lactam-based therapy. By acquisition of ESBLs, MBLs, or PBPs, it is highly likely that bacteria may become completely resistant to the most effective β-lactam agents in the near future. In this study, we described a natural extract rich in proanthocyanidins which exerts adjuvant properties by interfering with two different resistance mechanisms. By their broad-spectrum inhibitory ability, cranberry-extracted proanthocyanidins could have the potential to enhance the effectiveness of existing β-lactam agents.

In Vitro Activity of a Novel Siderophore-Cephalosporin LCB10-0200 (GT-1), and LCB10-0200/Avibactam, against Carbapenem-Resistant Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa Strains at a Tertiary Hospital in Korea

The siderophore-antibiotic conjugate LCB10-0200 (a.k.a. GT-1) has been developed to combat multidrug-resistant Gram-negative bacteria. In this study, the in vitro activity of LCB10-0200 and LCB10-0200/avibactam (AVI) has been investigated against carbapenem-resistant Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Minimal inhibitory concentrations (MICs) of LCB10-0200, LCB10-0200/AVI, aztreonam, aztreonam/AVI, ceftazidime, ceftazidime/AVI, and meropenem were measured using the agar dilution method. Whole genome sequencing was performed using Illumina and the resistome was analyzed. LCB10-0200 displayed stronger activity than the comparator drugs in meropenem-resistant E. coli and K. pneumoniae, and the addition of AVI enhanced the LCB10-0200 activity to MIC ≤ 0.12 mg/L for 90.5% of isolates. In contrast, whereas LCB10-0200 alone showed potent activity against meropenem-resistant A. baumannii and P. aeruginosa at MIC ≤ 4 mg/L for 84.3% of isolates, the combination with AVI did not improve its activity. LCB10-0200/AVI was active against CTX-M-, SHV-, CMY-, and KPC- producing E. coli and K. pneumoniae, while LCB10-0200 alone was active against ADC-, OXA-, and VIM- producing A. baumannii and P. aeruginosa. Both LCB10-0200 and LCB10-0200/AVI displayed low activity against IMP- and NDM- producing strains. LCB10-0200 alone exhibited strong activity against selected strains. The addition of AVI significantly increased LCB10-0200 activity against carbapenem-resistant E. coli, K. pneumoniae.

Prevalence and hazardous impact of pharmaceutical and personal care products and antibiotics in environment: A review on emerging contaminants

Antibiotic resistance is a global health emergency linked to unrestrained use of pharmaceutical and personal care products (PPCPs) as prophylactic agent and therapeutic purposes across various industries. Occurrence of pharmaceuticals are identified in ground water, surface water, soils, and wastewater treatment plants (WWTPs) in ng/L to μg/L concentration range. The prevalence of organic compounds including antimicrobial agents, hormones, antibiotics, preservatives, disinfectants, synthetic musks etc. in environment have posed serious health concerns. The aim of this review is to elucidate the major sources accountable for emergence of antibiotic resistance. For this purpose, variety of introductory sources and fate of PPCPs in aquatic environment including human and veterinary wastes, aquaculture and agriculture related wastes, and other anthropogenic activities have been discussed. Furthermore, genetic and enzymatic factors responsible for transfer and appearance of antibiotic resistance genes are presented. Ecotoxicity of PPCPs has been studied in environment in order to present risk imposed to human and ecological health. As per published literature reports, the removal of antibiotics and related traces being difficult, couples the possibility of emergence of antibiotic resistance and hence sustainability in global water resources. Therefore, research on environmental behavior and control strategies should be conducted along with assessing their chronic toxicity to identify potential human and ecological risks.

Recent advances in antibacterial agents

Antimicrobial resistance is a global challenge and the effectiveness of old antibiotics is decreasing. Discovery and development of antibacterial agents have been accelerated to replenish the arsenal of antibiotics which is limited and shrinking. In recent years, significant advances have achieved in the antibacterial area, including new compounds of known classes and new compounds with new mechanisms. This review summarizes these advances and provides perspective on future directions of antibacterial agents.

New β-Lactam-β-Lactamase Inhibitor Combinations

The limited armamentarium against drug-resistant Gram-negative bacilli has led to the development of several novel β-lactam-β-lactamase inhibitor combinations (BLBLIs). In this review, we summarize their spectrum of in vitro activities, mechanisms of resistance, and pharmacokinetic-pharmacodynamic (PK-PD) characteristics. A summary of available clinical data is provided per drug. Four approved BLBLIs are discussed in detail. All are options for treating multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa Ceftazidime-avibactam is a potential drug for treating Enterobacterales producing extended-spectrum β-lactamase (ESBL), Klebsiella pneumoniae carbapenemase (KPC), AmpC, and some class D β-lactamases (OXA-48) in addition to carbapenem-resistant Pseudomonas aeruginosa Ceftolozane-tazobactam is a treatment option mainly for carbapenem-resistant P. aeruginosa (non-carbapenemase producing), with some activity against ESBL-producing Enterobacterales Meropenem-vaborbactam has emerged as treatment option for Enterobacterales producing ESBL, KPC, or AmpC, with similar activity as meropenem against P. aeruginosa Imipenem-relebactam has documented activity against Enterobacterales producing ESBL, KPC, and AmpC, with the combination having some additional activity against P. aeruginosa relative to imipenem. None of these drugs present in vitro activity against Enterobacterales or P. aeruginosa producing metallo-β-lactamase (MBL) or against carbapenemase-producing Acinetobacter baumannii Clinical data regarding the use of these drugs to treat MDR bacteria are limited and rely mostly on nonrandomized studies. An overview on eight BLBLIs in development is also provided. These drugs provide various levels of in vitro coverage of carbapenem-resistant Enterobacterales, with several drugs presenting in vitro activity against MBLs (cefepime-zidebactam, aztreonam-avibactam, meropenem-nacubactam, and cefepime-taniborbactam). Among these drugs, some also present in vitro activity against carbapenem-resistant P. aeruginosa (cefepime-zidebactam and cefepime-taniborbactam) and A. baumannii (cefepime-zidebactam and sulbactam-durlobactam).

Discovery of an Orally Available Diazabicyclooctane Inhibitor (ETX0282) of Class A, C, and D Serine β-Lactamases

Multidrug resistant Gram-negative bacterial infections are an increasing public health threat due to rapidly rising resistance toward β-lactam antibiotics. The hydrolytic enzymes called β-lactamases are responsible for a large proportion of the resistance phenotype. β-Lactamase inhibitors (BLIs) can be administered in combination with β-lactam antibiotics to negate the action of the β-lactamases, thereby restoring activity of the β-lactam. Newly developed BLIs offer some advantage over older BLIs in terms of enzymatic spectrum but are limited to the intravenous route of administration. Reported here is a novel, orally bioavailable diazabicyclooctane (DBO) β-lactamase inhibitor. This new DBO, ETX1317, contains an endocyclic carbon-carbon double bond and a fluoroacetate activating group and exhibits broad spectrum activity against class A, C, and D serine β-lactamases. The ester prodrug of ETX1317, ETX0282, is orally bioavailable and, in combination with cefpodoxime proxetil, is currently in development as an oral therapy for multidrug resistant and carbapenem-resistant Enterobacterales infections.

Evolving trends of New Delhi Metallo-betalactamse (NDM) variants: A threat to antimicrobial resistance

The rapid emergence of carbapenemase producing Gram-negative bacterial strains exhibit broad-spectrum β-lactam resistance, especially New Delhi metallo-β-lactamase (NDM-1). It is a major public health threat as it catalyses the hydrolysis of a vast variety of β-lactam antibiotics, including carbapenems, which is the last choice for physicians to treat infections. NDM-1 and its variants are continuously spreading worldwide, in spite of constant efforts to control. Its clinical treatment remains challenging due to continuous evolution of new variants. A thorough structural study of all variants is required to develop new and effective inhibitors. This review focuses on the dissemination, position of substitution and carbapenemases activity of all the 28 NDM variants so far reported.

The role of new β-lactamase inhibitors in gram-negative infections

PURPOSE OF REVIEW

In recent years, traditional β-lactams have dramatically reduced their effectiveness against gram-negative bacteria mainly because of their ability to express multiple β-lactamase or carabapenemases that are not hydrolyzed by the old β-lactam inhibitors (BLIs) such as clavulanic acid, tazobactam, and sulbactam. New BLIs molecules have been developed to face the need of compounds that are active against multidrug or pandrug resistant gram-negative pathogens. The aim of this review is to summarize the new generation of BLIs and β-lactams combinations.

RECENT FINDINGS

A number of new molecules with activity against Ambler class A (e.g., extended-spectrum β-lactamases, serine carbapenemases), class C (e.g., AmpC), or class D (e.g., oxacillinase-48) have been recently approved in combination with old β-lactams for the treatment of multidrug-resistant bacteria, and other agents are under investigation. These new compounds include diazabicyclooctanones non-β-lactam inhibitors (e.g., avibactam, relebactam, nacubactam) and boronic acid inhibitors (e.g., vaborbactam).

SUMMARY

Newly approved and investigational new BLIs are expected to offer many advantages for the management of patients with multidrug-resistant gram-negative pathogens. Promising characteristics of new compounds include high activity against multi drug resistance gram-negative bacteria and a favorable safety profile.

Detection of Carbapenem-Resistance Genes in Klebsiella Species Recovered from Selected Environmental Niches in the Eastern Cape Province, South Africa

Carbapenemase-producing Enterobacteriaceae (CPE) have been heavily linked to hospital acquired infections (HAI) thereby leading to futility of antibiotics in treating infections and this have complicated public health problems. There is little knowledge about carbapenemase-producing Klebsiella spp. (CPK) in South Africa. This study aimed at determining the occurrence of CPK in different samples collected from selected environmental niches (hospitals, wastewater treatment plants, rivers, farms) in three district municipalities located in the Eastern Cape Province, South Africa. Molecular identification and characterization of the presumptive isolates were determined using polymerase chain reaction (PCR) and isolates that exhibited phenotypic carbapenem resistance were further screened for the possibility of harbouring antimicrobial resistance genes. One hundred (43%) of the 234 confirmed Klebsiella spp. isolates harboured carbapenem-resistance genes; 10 isolates harboured blaOXA-48-like; 17 harboured blaKPC; and 73 isolates harboured blaNDM-1. The emergence of blaKPC, blaOXA-48-like, and blaNDM-1 carbapenem-resistance genes in Klebsiella species associated with environmental sources is of great concern to public health.

PEG-8 Laurate Fermentation of Staphylococcus epidermidis Reduces the Required Dose of Clindamycin Against Cutibacterium acnes

The probiotic activity of skin Staphylococcus epidermidis (S. epidermidis) bacteria can elicit diverse biological functions via the fermentation of various carbon sources. Here, we found that polyethylene glycol (PEG)-8 Laurate, a carbon-rich molecule, can selectively induce the fermentation of S. epidermidis, not Cutibacterium acnes (C. acnes), a bacterium associated with acne vulgaris. The PEG-8 Laurate fermentation of S. epidermidis remarkably diminished the growth of C. acnes and the C. acnes-induced production of pro-inflammatory macrophage-inflammatory protein 2 (MIP-2) cytokines in mice. Fermentation media enhanced the anti-C. acnes activity of a low dose (0.1%) clindamycin, a prescription antibiotic commonly used to treat acne vulgaris, in terms of the suppression of C. acnes colonization and MIP-2 production. Furthermore, PEG-8 Laurate fermentation of S. epidermidis boosted the activity of 0.1% clindamycin to reduce the sizes of C. acnes colonies. Our results demonstrated, for the first time, that the PEG-8 Laurate fermentation of S. epidermidis displayed the adjuvant effect on promoting the efficacy of low-dose clindamycin against C. acnes. Targeting C. acnes by lowering the required doses of antibiotics may avoid the risk of creating drug-resistant C. acnes and maintain the bacterial homeostasis in the skin microbiome, leading to a novel modality for the antibiotic treatment of acne vulgaris.

Profile of Enterobacteria Resistant to Beta-Lactams

A serious emerging problem worldwide is increased antimicrobial resistance. Acquisition of coding genes for evasion methods of antimicrobial drug mechanisms characterizes acquired resistance. This phenomenon has been observed in Enterobacteriaceae family. Treatment for bacterial infections is performed with antibiotics, of which the most used are beta-lactams. The aim of this study was to correlate antimicrobial resistance profiles in Enterobacteriaceae by phenotypic methods and molecular identification of 14 beta-lactamase coding genes. In this study, 70 exclusive isolates from Brazil were used, half of which were collected in veterinary clinics or hospitals Phenotypic methodologies were used and real-time PCR was the molecular methodology used, through the Sybr Green system. Regargding the results found in the tests it was observed that 74.28% were resistant to ampicillin, 62.85% were resistant to amoxicillin associated with clavalunate. The mechanism of resistance that presented the highest expression was ESBL (17.14%). The genes studied that were detected in a greater number of species were blaGIM and blaSIM (66.66% of the samples) and the one that was amplified in a smaller number of samples was blaVIM (16.66%). Therefore, high and worrying levels of antimicrobial resistance have been found in enterobacteria, and a way to minimize the accelerated emergence of their resistance includes developing or improving techniques that generate diagnoses with high efficiency and speed.

Antibiotic resistance breakers: current approaches and future directions

Infections of antibiotic-resistant pathogens pose an ever-increasing threat to mankind. The investigation of novel approaches for tackling the antimicrobial resistance crisis must be part of any global response to this problem if an untimely reversion to the pre-penicillin era of medicine is to be avoided. One such promising avenue of research involves so-called antibiotic resistance breakers (ARBs), capable of re-sensitising resistant bacteria to antibiotics. Although some ARBs have previously been employed in the clinical setting, such as the β-lactam inhibitors, we posit that the broader field of ARB research can yet yield a greater diversity of more effective therapeutic agents than have been previously achieved. This review introduces the area of ARB research, summarises the current state of ARB development with emphasis on the various major classes of ARBs currently being investigated and their modes of action, and offers a perspective on the future direction of the field.

Activity of Cefiderocol Against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii Endemic to Medical Centers in New York City

Therapeutic options for the treatment of infections owing to multidrug-resistant Gram-negative pathogens are often limited. Cefiderocol is a novel siderophore cephalosporin with activity against Gram-negative pathogens, including many multidrug-resistant strains. The activity of cefiderocol was examined against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii that included (1) a recent surveillance collection of clinical isolates, (2) a collection of carbapenem-resistant isolates from a previous surveillance study, and (3) a collection of well-characterized isolates. Susceptibility testing for cefiderocol was performed with iron-depleted cation-adjusted Mueller-Hinton broth. Cefiderocol minimum inhibitory concentrations (MICs) were correlated with resistance mechanisms in the well-characterized isolates. For the Enterobacterales, including a collection of KPC-possessing Klebsiella pneumoniae, cefiderocol MICs were all ≤4 mg/L. Cefiderocol MICs were two- to fourfold higher in cephalosporin-resistant isolates. For K. pneumoniae, MICs did not correlate with expression of genes encoding porins or efflux systems. For P. aeruginosa, >99% of isolates were inhibited by ≤4 mg/L, including the collection of carbapenem-resistant isolates. For P. aeruginosa, cefiderocol activity was not affected by expression of ampC, oprD, or several efflux systems. All the surveillance isolates of A. baumannii, and 88% of the collection of carbapenem-resistant isolates, had cefiderocol MICs ≤4 mg/L. MICs were twofold higher in A. baummannii isolates with proven extended-spectrum beta-lactamases, and cefiderocol activity did not correlate with expression of efflux systems. Cefiderocol demonstrated potent activity against important nosocomial pathogens. Continued development of this agent as a therapeutic option against multidrug-resistant bacteria should be encouraged.

The Evolution and Ecology of Bacterial Warfare

Bacteria have evolved a wide range of mechanisms to harm and kill their competitors, including chemical, mechanical and biological weapons. Here we review the incredible diversity of bacterial weapon systems, which comprise antibiotics, toxic proteins, mechanical weapons that stab and pierce, viruses, and more. The evolution of bacterial weapons is shaped by many factors, including cell density and nutrient abundance, and how strains are arranged in space. Bacteria also employ a diverse range of combat behaviours, including pre-emptive attacks, suicidal attacks, and reciprocation (tit-for-tat). However, why bacteria carry so many weapons, and why they are so often used, remains poorly understood. By comparison with animals, we argue that the way that bacteria live - often in dense and genetically diverse communities - is likely to be key to their aggression as it encourages them to dig in and fight alongside their clonemates. The intensity of bacterial aggression is such that it can strongly affect communities, via complex coevolutionary and eco-evolutionary dynamics, which influence species over space and time. Bacterial warfare is a fascinating topic for ecology and evolution, as well as one of increasing relevance. Understanding how bacteria win wars is important for the goal of manipulating the human microbiome and other important microbial systems.

New strategies and structural considerations in development of therapeutics for carbapenem-resistant Enterobacteriaceae

Antimicrobial resistance poses a significant threat to our ability to treat infections. Especially concerning is the emergence of carbapenem-resistant Enterobacteriaceae (CRE). In the new 2019 United States Centers for Disease Control and Prevention Antibiotic Resistance Report, CRE remain in the most urgent antimicrobial resistance threat category. There is good reason for this concerning designation. In particular, the combination of several resistance elements in CRE can make these pathogens untreatable or effectively untreatable with our current armamentarium of anti-infective agents. This article reviews recently approved agents with activity against CRE and a range of modalities in the pipeline, from early academic investigation to those in clinical trials, with a focus on structural aspects of new antibiotics. Another article in this series addresses the need to incentive pharmaceutical companies to invest in CRE antimicrobial development and to encourage hospitals to make these agents available in their formularies. This article will also consider the need for change in requirements for antimicrobial susceptibility testing implementation in clinical laboratories to address practical roadblocks that impede our efforts to provide even existing CRE antibiotics to our patients.

Reconciling the Potentially Irreconcilable? Genotypic and Phenotypic Amoxicillin-Clavulanate Resistance in Escherichia coli

Resistance to amoxicillin-clavulanate, a widely used beta-lactam/beta-lactamase inhibitor combination antibiotic, is rising globally, and yet susceptibility testing remains challenging. To test whether whole-genome sequencing (WGS) could provide a more reliable assessment of susceptibility than traditional methods, we predicted resistance from WGS for 976 Escherichia coli bloodstream infection isolates from Oxfordshire, United Kingdom, comparing against phenotypes from the BD Phoenix (calibrated against EUCAST guidelines).

Resistance to amoxicillin-clavulanate, a widely used beta-lactam/beta-lactamase inhibitor combination antibiotic, is rising globally, and yet susceptibility testing remains challenging. To test whether whole-genome sequencing (WGS) could provide a more reliable assessment of susceptibility than traditional methods, we predicted resistance from WGS for 976 Escherichia coli bloodstream infection isolates from Oxfordshire, United Kingdom, comparing against phenotypes from the BD Phoenix (calibrated against EUCAST guidelines). A total of 339/976 (35%) isolates were amoxicillin-clavulanate resistant. Predictions based solely on beta-lactamase presence/absence performed poorly (sensitivity, 23% [78/339]) but improved when genetic features associated with penicillinase hyperproduction (e.g., promoter mutations and copy number estimates) were considered (sensitivity, 82% [277/339]; P < 0.0001). Most discrepancies occurred in isolates with MICs within ±1 doubling dilution of the breakpoint. We investigated two potential causes: the phenotypic reference and the binary resistant/susceptible classification. We performed reference standard, replicated phenotyping in a random stratified subsample of 261/976 (27%) isolates using agar dilution, following both EUCAST and CLSI guidelines, which use different clavulanate concentrations. As well as disagreeing with each other, neither agar dilution phenotype aligned perfectly with genetic features. A random-effects model investigating associations between genetic features and MICs showed that some genetic features had small, variable and additive effects, resulting in variable resistance classification. Using model fixed-effects to predict MICs for the non-agar dilution isolates, predicted MICs were in essential agreement (±1 doubling dilution) with observed (BD Phoenix) MICs for 691/715 (97%) isolates. This suggests amoxicillin-clavulanate resistance in E. coli is quantitative, rather than qualitative, explaining the poorly reproducible binary (resistant/susceptible) phenotypes and suboptimal concordance between different phenotypic methods and with WGS-based predictions.

VNRX-5133 (Taniborbactam), a Broad-Spectrum Inhibitor of Serine- and Metallo-β-Lactamases, Restores Activity of Cefepime in Enterobacterales and Pseudomonas aeruginosa

As shifts in the epidemiology of β-lactamase-mediated resistance continue, carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) are the most urgent threats. Although approved β-lactam (BL)-β-lactamase inhibitor (BLI) combinations address widespread serine β-lactamases (SBLs), such as CTX-M-15, none provide broad coverage against either clinically important serine-β-lactamases (KPC, OXA-48) or clinically important metallo-β-lactamases (MBLs; e.g., NDM-1). VNRX-5133 (taniborbactam) is a new cyclic boronate BLI that is in clinical development combined with cefepime for the treatment of infections caused by β-lactamase-producing CRE and CRPA. Taniborbactam is the first BLI with direct inhibitory activity against Ambler class A, B, C, and D enzymes. From biochemical and structural analyses, taniborbactam exploits substrate mimicry while employing distinct mechanisms to inhibit both SBLs and MBLs. It is a reversible covalent inhibitor of SBLs with slow dissociation and a prolonged active-site residence time (half-life, 30 to 105 min), while in MBLs, it behaves as a competitive inhibitor, with inhibitor constant (K_i ) values ranging from 0.019 to 0.081 μM. Inhibition is achieved by mimicking the transition state structure and exploiting interactions with highly conserved active-site residues. In microbiological testing, taniborbactam restored cefepime activity in 33/34 engineered Escherichia coli strains overproducing individual enzymes covering Ambler classes A, B, C, and D, providing up to a 1,024-fold shift in the MIC. Addition of taniborbactam restored the antibacterial activity of cefepime against all 102 Enterobacterales clinical isolates tested and 38/41 P. aeruginosa clinical isolates tested with MIC₉₀s of 1 and 4 μg/ml, respectively, representing ≥256- and ≥32-fold improvements, respectively, in antibacterial activity over that of cefepime alone. The data demonstrate the potent, broad-spectrum rescue of cefepime activity by taniborbactam against clinical isolates of CRE and CRPA.

Activity of Meropenem with a Novel Broader-Spectrum β-Lactamase Inhibitor, WCK 4234, against Gram-Negative Pathogens Endemic to New York City

WCK 4234 is a novel diazabicyclooctane with potent inhibitory activity against class A and D carbapenemases and class C enzymes. We examined the in vitro activity of meropenem plus WCK 4234 (4 or 8 μg/ml) against Gram-negative pathogens from New York City. Three groups of isolates were analyzed: a contemporary collection of isolates, a collection of known carbapenem-resistant isolates, and a collection of isolates with defined resistance mechanisms. From the contemporary collection, we found (i) that all Enterobacteriaceae were susceptible to meropenem plus WCK 4234, (ii) that susceptibility rates for Acinetobacter baumannii were 56.5% for meropenem alone, 82.6% with 4 μg/ml WCK 4234, and 95.7% with 8 μg/ml WCK 4234, and (iii) that WCK 4234 had a modest effect on susceptibility of Pseudomonas aeruginosa Against a collection of carbapenem-resistant isolates, the addition of WCK 4234 to meropenem (i) restored meropenem susceptibility against Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates, (ii) improved susceptibility against A. baumannii, and (iii) had a negligible effect against P. aeruginosa When tested against isolates with defined mechanisms of resistance, MICs of meropenem plus WCK 4234 were higher for K. pneumoniae with bla _KPC albeit well below the susceptibility breakpoint; efflux systems or porins did not correlate with susceptibility. For A. baumannii, MICs of meropenem plus WCK 4234 did not correlate with efflux systems, outer membrane protein, bla _ampC, or bla _oxa-51; however, MICs were higher in isolates with extended-spectrum β-lactamases (ESBLs). For P. aeruginosa, isolates with relatively higher MICs of meropenem plus WCK 4234 had increased expression of ampC WCK 4234 is a potent β-lactamase inhibitor that, when combined with meropenem, displays promising activity against multidrug-resistant pathogens.

Extended spectrum β-lactamase producing enterobacteriaceae: carbapenem sparing options

Introduction: Carbapenems have an important place in our antibiotic armamentarium and have been trusted to effectively treat infections caused by ESBL-producing Enterobacteriaceae for many years. However, the utility of carbapenems has been compromised by the emergence of resistance especially in Enterobacteriaceae. Therefore, carbapenem-sparing alternative antibiotics are of extreme importance in clinical practice.Areas covered: We reviewed studies addressing currently available antibiotic options used as both empiric and definitive therapy for the treatment of infections due to ESBL-producing Enterobacteriaceae published in the PubMed/MEDLINE, Web of Science and Scopus databases without any date restriction. Current treatment alternatives included beta-lactam/beta-lactamase inhibitor combinations, cefepime, cephamycins, fluoroquinolones, aminoglycosides, fosfomycin, pivmecillinam, temocillin and, various oral alternative agents. We also summarized the clinical and molecular epidemiology, early prediction methods and impact of initial empirical therapy and de-escalation approach for ESBL-producing Enterobacteriaceae infections.Expert opinion: The current literature would endorse the carbapenem utilization for patients with severe and high inoculum-high risk infections. However, for milder infections particularly for urinary tract infections, various carbapenem-sparing antibiotics can be considered in selected cases. For infections including easily drainable intra-abdominal infections and catheter-related infections in which catheter removal is readily available more reliable data are needed to recommend non-carbapenem antibiotics confidently.

Selection of mutants with resistance or diminished susceptibility to ceftazidime/avibactam from ESBL- and AmpC-producing Enterobacteriaceae

Introduction

Difficult Gram-negative infections are increasingly treated with new β-lactamase inhibitor combinations, e.g. ceftazidime/avibactam. Disturbingly, mutations in KPC carbapenemases can confer ceftazidime/avibactam resistance, which is sometimes selected during therapy. We explored whether this risk extended to AmpC and ESBL enzymes.

Methods

Mutants were selected by plating AmpC-derepressed strains, ESBL producers and ceftazidime-susceptible controls on agar containing ceftazidime + avibactam (1 or 4 mg/L). MICs were determined by CLSI agar dilution; WGS was by Illumina methodology.

Results

Using 2× MIC of ceftazidime + 1 mg/L avibactam, mutants were selected from all strain types at frequencies of 10-7-10-9. Rates diminished to <10-9 with 4 mg/L avibactam or higher MIC multiples, except with AmpC-derepressed Enterobacteriaceae. Characterized mutants (n = 10; MICs 4-64 mg/L) of AmpC-derepressed strains had modifications in ampC, variously giving Arg168Pro/His, Gly176Arg/Asp, Asn366Tyr or small deletions around positions 309-314. Mutants of ESBL producers (n = 19; MICs 0.5-16 mg/L) mostly had changes affecting permeability, efflux or β-lactamase quantity; only one had an altered β-lactamase, with an Asp182Tyr substitution in CTX-M-15, raising the ceftazidime/avibactam MIC, but abrogating other cephalosporin resistance. Mutants of ceftazidime-susceptible strains were not sequenced, but phenotypes suggested altered drug accumulation or, for Enterobacter cloacae only, AmpC derepression. In further experiments, avibactam reduced, but did not abolish, selection of AmpC-derepressed Enterobacteriaceae by ceftazidime.

Conclusions

Most mutants of AmpC-derepressed Enterobacteriaceae had structural mutations in ampC; those of ESBL producers mostly had genetic modifications outside β-lactamase genes, commonly affecting uptake, efflux, or β-lactamase quantity. The clinical significance of these observations remains to be determined.

The ideal patient profile for new beta-lactam/beta-lactamase inhibitors

PURPOSE OF REVIEW

The worldwide spread of extended-spectrum beta-lactamase (ESBL)-producing bacteria, the overuse of carbapenems, the emergence of carbapenemase-producing organisms and the growing importance of multidrug-resistant and/or extended drug-resistant strains have totally changed prescribers' habits, leading to very few treatment options in many cases. Beta-lactam/beta-lactamase inhibitor (BLBLI) combinations should be considered as an alternative to carbapenems for treating ESBL-producing bacteria and Pseudomonas aeruginosa infections. The purpose of this study was to provide insight concerning the patients who would constitute ideal candidates to receive these new BLBLI combinations.

RECENT FINDINGS

Ceftolozane/tazobactam and ceftazidime/avibactam are the first drugs constituting the use of new beta-lactamase inhibitors. Ceftolozane/tazobactam is the drug of choice for treating MDR/XDR P. aeruginosa infections. Ceftazidime/avibactam is the best drug available for treating KPC and OXA-48 carbapenemase-producing Enterobacteriaceae. Ceftolozane/tazobactam and ceftazidime/avibactam are both carbapenem-sparing agents for treating ESBL-producing Enterobacteriaceae. The role of carbapenem/inhibitors remains to be clarified.

SUMMARY

Each BLBLI combination has distinctive specificities and limitations that need to be investigated cautiously. Randomized trials will play a key role in defining the best strategies. Infection control measures and prompt diagnosis remain fundamental to prevent dissemination of MDR pathogens in healthcare settings and to optimize early antimicrobial treatment.

Successful treatment of KPC-MDR septic shock with ceftazidime-avibactam in a pediatric critically ill patient

Ceftazidime–avibactam is a combination agent consisting of the β-lactamase inhibitor avibactam and the broad-spectrum cephalosporin ceftazidime. There are no published case reports or studies evaluating the use of CAZ-AVI in pediatric critically ill patients. We report a case of a successful treatment of septic shock due to Klebsiella pneumonie (KP) in a 14-years-old boy (body weight 50 kg) admitted in intensive care unit (ICU).

New antibiotics for ventilator-associated pneumonia

PURPOSE OF REVIEW

Ventilator-associated pneumonia (VAP) caused by multidrug-resistant (MDR) bacteria represents a global emerging problem. Delayed prescription of an adequate treatment for VAP has been associated with higher morbidity and mortality. New molecules have been developed to face the need of compounds that are active against resistant Gram-positive and Gram-negative pathogens. The aim of this review is to summarize the current scenario of new therapeutic options for the treatment of VAP.

RECENT FINDINGS

A number of new antibiotics with activity against MDR have been recently approved for the treatment of VAP, and other agents are under investigation. In this review, the authors summarize the current therapeutic options for the treatment of VAP that showed promising implications for clinical practice, including new compounds belonging to old antibiotic classes (e.g., ceftolozane/tazobactam, ceftazidime/avibactam meropenem/vaborbactam, imipenem/relebactam, tedizolid, cefiderocol, eravacycline, and plazomicin) and novel chemical classes, such as murepavadin. Nebulized antibiotics that are currently in development for the treatment of pneumonia in mechanically ventilated patients are also presented.

SUMMARY

Newly approved and investigational drugs for the treatment of VAP are expected to offer many advantages for the management of patients with respiratory infections caused by MDR. Promising characteristics of new compounds include high activity against both methicillin-resistant Staphylococcus aureus and MDR Gram-negative bacteria and a favorable safety profile.

Novel and Improved Crystal Structures of H. influenzae, E. coli and P. aeruginosa Penicillin-Binding Protein 3 (PBP3) and N. gonorrhoeae PBP2: Toward a Better Understanding of β-Lactam Target-Mediated Resistance

Even with the emergence of antibiotic resistance, penicillin and the wider family of β-lactams have remained the single most important family of antibiotics. The periplasmic/extra-cytoplasmic targets of penicillin are a family of enzymes with a highly conserved catalytic activity involved in the final stage of bacterial cell wall (peptidoglycan) biosynthesis. Named after their ability to bind penicillin, rather than their catalytic activity, these key targets are called penicillin-binding proteins (PBPs). Resistance is predominantly mediated by reducing the target drug concentration via β-lactamases; however, naturally transformable bacteria have also acquired target-mediated resistance by inter-species recombination. Here we focus on structural based interpretations of amino acid alterations associated with the emergence of resistance within clinical isolates and include new PBP3 structures along with new, and improved, PBP-β-lactam co-structures.

What the Clinical Microbiologist Should Know About Pharmacokinetics/Pharmacodynamics in the Era of Emerging Multidrug Resistance: Focusing on β-Lactam/β-Lactamase Inhibitor Combinations

As a class, β-lactamase inhibitors have proved successful in extending the clinical utility of β-lactam antibiotics by circumventing β-lactamase-mediated resistance. However, the rapid evolution of these β-lactamases calls for a critical reevaluation of the relationships between susceptibility, drug exposures, and bacterial response. The existing paradigm for in vitro susceptibility testing and development of β-lactam/β-lactamase inhibitor combinations may not optimally facilitate clinical use. Thus, alternative approaches for pairing these combinations and evaluating in vitro susceptibility are needed to provide better guidance to clinicians.