Pharmacological aspects and spectrum of action of ceftazidime-avibactam: a systematic review

Metallo-β-lactamase inhibitors: A continuing challenge for combating antibiotic resistance

β-lactam antibiotics are the most successful and commonly used antibacterial agents, but the emergence of resistance to these drugs has become a global health threat. The expression of β-lactamase enzymes produced by pathogens, which hydrolyze the amide bond of the β-lactam ring, is the major mechanism for bacterial resistance to β-lactams. In particular, among class A, B, C and D β-lactamases, metallo-β-lactamases (MBLs, class B β-lactamases) are considered crucial contributors to resistance in gram-negative bacteria. To combat β-lactamase-mediated resistance, great efforts have been made to develop β-lactamase inhibitors that restore the activity of β-lactams. Some β-lactamase inhibitors, such as diazabicyclooctanes (DBOs) and boronic acid derivatives, have also been approved by the FDA. Inhibitors used in the clinic can inactivate mostly serine-β-lactamases (SBLs, class A, C, and D β-lactamases) but have not been effective against MBLs until now. In order to develop new inhibitors particularly for MBLs, various attempts have been suggested. Based on structural and mechanical studies of MBL enzymes, several MBL inhibitor candidates, including taniborbactam in phase 3 and xeruborbactam in phase 1, have been introduced in recent years. However, designing potent inhibitors that are effective against all subclasses of MBLs is still extremely challenging. This review summarizes not only the types of β-lactamase and mechanisms by which β-lactam antibiotics are inactivated, but also the research finding on β-lactamase inhibitors targeting these enzymes. These detailed information on β-lactamases and their inhibitors could give valuable information for novel β-lactamase inhibitors design.

Antimicrobials: An update on new strategies to diversify treatment for bacterial infections

Ninety-five years after Fleming's discovery of penicillin, a bounty of antibiotic compounds have been discovered, modified, or synthesised. Diversification of target sites, improved stability and altered activity spectra have enabled continued antibiotic efficacy, but overwhelming reliance and misuse has fuelled the global spread of antimicrobial resistance (AMR). An estimated 1.27 million deaths were attributable to antibiotic resistant bacteria in 2019, representing a major threat to modern medicine. Although antibiotics remain at the heart of strategies for treatment and control of bacterial diseases, the threat of AMR has reached catastrophic proportions urgently calling for fresh innovation. The last decade has been peppered with ground-breaking developments in genome sequencing, high throughput screening technologies and machine learning. These advances have opened new doors for bioprospecting for novel antimicrobials. They have also enabled more thorough exploration of complex and polymicrobial infections and interactions with the healthy microbiome. Using models of infection that more closely resemble the infection state in vivo, we are now beginning to measure the impacts of antimicrobial therapy on host/microbiota/pathogen interactions. However new approaches are needed for developing and standardising appropriate methods to measure efficacy of novel antimicrobial combinations in these contexts. A battery of promising new antimicrobials is now in various stages of development including co-administered inhibitors, phages, nanoparticles, immunotherapy, anti-biofilm and anti-virulence agents. These novel therapeutics need multidisciplinary collaboration and new ways of thinking to bring them into large scale clinical use.

Carbapenem-Resistant Enterobacteriaceae in Urinary Tract Infections: From Biological Insights to Emerging Therapeutic Alternatives

Urinary tract infections (UTIs) are the second most frequent type of infection observed in clinical practice. Gram-negative Enterobacteriaceae are common pathogens in UTIs. Excessive antibiotic use in humans and animals, poor infection control, and increased global travel have accelerated the spread of multidrug-resistant strains (MDR). Carbapenem antibiotics are commonly considered the last line of defense against MDR Gram-negative bacteria; however, their efficacy is now threatened by the increasing prevalence of carbapenem-resistant Enterobacteriaceae (CRE). This comprehensive review aims to explore the biological mechanisms underlying carbapenem resistance and to present a focus on therapeutic alternatives currently available for complicated UTIs (cUTIs). A comprehensive bibliographic search was conducted on the PubMed/MEDLINE, Scopus, and Web of Science databases in December 2023. The best evidence on the topic was selected, described, and discussed. Analyzed with particular interest were the clinical trials pivotal to the introduction of new pharmacological treatments in the management of complicated cUTIs. Additional suitable articles were collected by manually cross-referencing the bibliography of previously selected papers. This overview provides a current and comprehensive examination of the treatment options available for CRE infections, offering a valuable resource for understanding this constantly evolving public health challenge.

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.

Management strategies for severe Pseudomonas aeruginosa infections

PURPOSE OF REVIEW

This review focuses on the management of severe Pseudomonas aeruginosa infections in critically ill patients.

RECENT FINDINGS

Pseudomonas aeruginosa is the most common pathogen in intensive care; the main related infections are nosocomial pneumonias, then bloodstream infections. Antimicrobial resistance is common; despite new antibiotics, it is associated with increased mortality, and can lead to a therapeutic deadlock.

SUMMARY

Carbapenem resistance in difficult-to-treat P. aeruginosa (DTR-PA) strains is primarily mediated by loss or reduction of the OprD porin, overexpression of the cephalosporinase AmpC, and/or overexpression of efflux pumps. However, the role of carbapenemases, particularly metallo-β-lactamases, has become more important. Ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam are useful against DTR phenotypes (noncarbapenemase producers). Other new agents, such as aztreonam-ceftazidime-avibactam or cefiderocol, or colistin, might be effective for carbapenemase producers. Regarding nonantibiotic agents, only phages might be considered, pending further clinical trials. Combination therapy does not reduce mortality, but may be necessary for empirical treatment. Short-term treatment of severe P. aeruginosa infections should be preferred when it is expected that the clinical situation resolves rapidly.

Combatting resistance: Understanding multi-drug resistant pathogens in intensive care units

The escalating misuse and excessive utilization of antibiotics have led to the widespread dissemination of drug-resistant bacteria, posing a significant global healthcare crisis. Of particular concern is the increasing prevalence of multi-drug resistant (MDR) opportunistic pathogens in Intensive Care Units (ICUs), which presents a severe threat to public health and contributes to substantial morbidity and mortality. Among them, MDR ESKAPE pathogens account for the vast majority of these opportunistic pathogens. This comprehensive review provides a meticulous analysis of the current prevalence landscape of MDR opportunistic pathogens in ICUs, especially in ESKAPE pathogens, illuminating their resistance mechanisms against commonly employed first-line antibiotics, including polymyxins, carbapenems, and tigecycline. Furthermore, this review explores innovative strategies aimed at preventing and controlling the emergence and spread of resistance. By emphasizing the urgent need for robust measures to combat nosocomial infections caused by MDR opportunistic pathogens in ICUs, this study serves as an invaluable reference for future investigations in the field of antibiotic resistance.

Ceftazidime/Avibactam and Meropenem/Vaborbactam for the Management of Enterobacterales Infections: A Narrative Review, Clinical Considerations, and Expert Opinion

This comprehensive review examines the unique attributes, distinctions, and clinical implications of ceftazidime-avibactam (CAZ-AVI) and meropenem-vaborbactam (MEM-VAB) against difficult-to-treat Enterobacterales infections. Our manuscript explores these antibiotics' pharmacokinetic and pharmacodynamic properties, antimicrobial activities, in vitro susceptibility testing, and clinical data. Moreover, it includes a meticulous examination of comparative clinical and microbiological studies, assessed and presented to provide clarity in making informed treatment choices for clinicians. Finally, we propose an expert opinion from a microbiological and a clinical point of view about their use in appropriate clinical settings. This is the first review aiming to provide healthcare professionals with valuable insights for making informed treatment decisions when combating carbapenem-resistant pathogens.

Pharmacokinetic and Pharmacodynamic Considerations of Novel Antibiotic Agents for Pediatric Infections: A Narrative Review

Background: Currently, the escalation of microbial resistance poses a significant global challenge. Children are more susceptible to develop infections and therefore are prescribed antibiotics more frequently. The overuse and misuse of antibiotics in pediatric patients can play a considerable role in developing microbial resistance. Accordingly, many policies, including research into new antibiotic agents have been recommended to combat microbial resistance. Recent developments in novel antibiotics have shown promising results against multi-drug resistant (MDR) and extensive drug resistance (XDR) pathogens. However, as pediatric patients are typically excluded from the clinical trials of new medications, labeling and information about approved antibiotics should be improved. This study aimed to evaluate antibiotics having been introduced to the market in the last decade focusing on pediatric population. Methods: This study reviewed the published literatures on novel FDA-approved antibiotics released between 2010 and 2022. Results: Finally, seven newly approved antibiotics including ceftaroline fosamil, ceftazidime-avibactam, ceftolozane-tazobactam, ceftobiprole, imipenem-cilastatin-relebactam, meropenem-vaborbactam, and tedizolid were considered in the present review-article. All relevant data extracted from literatures, were discussed in different subtitles of "Pharmacology", "Mechanism of action", "Indication", "Dosage regimen and pharmacokinetic and pharmacodynamic properties", "Dosage adjustment in renal/liver failure", "Resistance pattern", and "Adverse drug events". Conclusion: This study reviewed available data on seven new antibiotic agents and their pharmacodynamic and pharmacokinetic properties, with a particular focus on their use in pediatric patients. The information presented in this review will be useful for healthcare professionals in selecting appropriate antibiotics for pediatric patients and for researchers in achieving the ideal therapeutic regimens.

Inhibition of β-lactamase function by de novo designed peptide

Antimicrobial resistance is a great public health concern that is now described as a "silent pandemic". The global burden of antimicrobial resistance requires new antibacterial treatments, especially for the most challenging multidrug-resistant bacteria. There are various mechanisms by which bacteria develop antimicrobial resistance including expression of β-lactamase enzymes, overexpression of efflux pumps, reduced cell permeability through downregulation of porins required for β-lactam entry, or modifications in penicillin-binding proteins. Inactivation of the β-lactam antibiotics by β-lactamase enzymes is the most common mechanism of bacterial resistance to these agents. Although several effective small-molecule inhibitors of β-lactamases such as clavulanic acid and avibactam are clinically available, they act only on selected class A, C, and some class D enzymes. Currently, none of the clinically approved inhibitors can effectively inhibit Class B metallo-β-lactamases. Additionally, there is increased resistance to these inhibitors reported in several bacteria. The objective of this study is to use the Resonant Recognition Model (RRM), as a novel strategy to inhibit/modulate specific antimicrobial resistance targets. The RRM is a bio-physical approach that analyzes the distribution of energies of free electrons and posits that there is a significant correlation between the spectra of this energy distribution and related protein biological activity. In this study, we have used the RRM concept to evaluate the structure-function properties of a group of 22 β-lactamase proteins and designed 30-mer peptides with the desired RRM spectral periodicities (frequencies) to function as β-lactamase inhibitors. In contrast to the controls, our results indicate 100% inhibition of the class A β-lactamases from Escherichia coli and Enterobacter cloacae. Taken together, the RRM model can likely be utilized as a promising approach to design β-lactamase inhibitors for any specific class. This may open a new direction to combat antimicrobial resistance.

Bloodstream Infection and Gram-Negative Resistance: The Role for Newer Antibiotics

Gram-negative resistance remains a major challenge. Rates of in vitro resistance to commonly utilized antibiotics have skyrocketed over the last decade. Clinicians now encounter multidrug-resistant organisms routinely. Fortunately, newer agents, such as ceftazidime-avibactam, ceftolozone-tazobactam, meropenem-vaborbactam, and cefiderocol, have been developed and are now available for use against these pathogens. Clinical trials with these novel therapies have focused on multiple infection types ranging from complicated urinary tract infections to nosocomial pneumonia. Nonetheless, there remains little information about the efficacy of these drugs for bacteremia. To better appreciate the types and limitations of the evidence supporting the role for these unique molecules in bloodstream infection, one requires an appreciation of the initial clinical trials supporting the regulatory approval of these antibiotics. Furthermore, physicians must understand the subsequent case series and reports specifically focusing on outcomes for patients with bacteremia treated with these drugs. Despite the limitations of the data and reports relating to treatment for bacteremia with these antibiotics, each agent appears to be efficacious and can provide good outcomes in bloodstream infections due to resistant pathogens.

The spread of antibiotic resistance to humans and potential protection strategies

Antibiotic resistance is currently one of the greatest threats to human health. Widespread use and residues of antibiotics in humans, animals, and the environment can exert selective pressure on antibiotic resistance bacteria (ARB) and antibiotic resistance gene (ARG), accelerating the flow of antibiotic resistance. As ARG spreads to the population, the burden of antibiotic resistance in humans increases, which may have potential health effects on people. Therefore, it is critical to mitigate the spread of antibiotic resistance to humans and reduce the load of antibiotic resistance in humans. This review briefly described the information of global antibiotic consumption information and national action plans (NAPs) to combat antibiotic resistance and provided a set of feasible control strategies for the transmission of ARB and ARG to humans in three areas including (a) Reducing the colonization capacity of exogenous ARB, (b) Enhancing human colonization resistance and mitigating the horizontal gene transfer (HGT) of ARG, (c) Reversing ARB antibiotic resistance. With the hope of achieving interdisciplinary one-health prevention and control of bacterial resistance.

What to Do with the New Antibiotics?

Multidrug-resistant Gram-negative bacteria-related infections have become a real public health problem and have exposed the risk of a therapeutic impasse. In recent years, many new antibiotics have been introduced to enrich the therapeutic armamentarium. Among these new molecules, some are mainly of interest for the treatment of the multidrug-resistant infections associated with Pseudomonas aeruginosa (ceftolozane/tazobactam and imipenem/relebactam); others are for carbapenem-resistant infections associated with Enterobacterales (ceftazidime/avibactam, meropenem/vaborbactam); and finally, there are others that are effective on the majority of multidrug-resistant Gram-negative bacilli (cefiderocol). Most international guidelines recommend these new antibiotics in the treatment of microbiologically documented infections. However, given the significant morbidity and mortality of these infections, particularly in the case of inadequate therapy, it is important to consider the place of these antibiotics in probabilistic treatment. Knowledge of the risk factors for multidrug-resistant Gram-negative bacilli (local ecology, prior colonization, failure of prior antibiotic therapy, and source of infection) seems necessary in order to optimize antibiotic prescriptions. In this review, we will assess these different antibiotics according to the epidemiological data.

Evaluation of in-vitro susceptibility of ß-lactam-resistant Gram-negative bacilli to ceftazidime-avibactam and ceftolozane-tazobactam from clinical samples of a general hospital in southern Brazil

BACKGROUND

The spread of carbapenemase- and extended-spectrum β-lactamase (ESBL)-producing gram-negative bacilli (GNB) represent a global public health threat that limits therapeutic options for hospitalized patients. This study aimed to evaluate the in-vitro susceptibility of β-lactam-resistant GNB to ceftazidime-avibactam (C/A) and ceftolozane-tazobactam (C/T), and investigate the molecular determinants of resistance.

METHODS

Overall, 101 clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected from a general hospital in Brazil were analyzed. Susceptibility to the antimicrobial agents was evaluated using an automated method, and the minimum inhibitory concentrations (MIC50/90) of C/A and C/T were determined using Etest®. The β-lactamase-encoding genes were investigated using polymerase chain reaction.

RESULTS

High susceptibility to C/A and C/T was observed among ESBL-producing Enterobacterales (100% and 97.3% for CLSI and 83.8% for BRCAST, respectively) and carbapenem-resistant P. aeruginosa (92.3% and 87.2%, respectively). Carbapenemase-producing Klebsiella pneumoniae exhibited high resistance to C/T (80%- CLSI or 100%- BRCAST) but high susceptibility to C/A (93.4%). All carbapenem-resistant K. pneumoniae isolates were susceptible to C/A, whereas only one isolate was susceptible to C/T. Both antimicrobials were inactive against metallo-β-lactamase-producing K. pneumoniae isolates. Resistance genes were concomitantly identified in 44 (44.9%) isolates, with bla CTX-M and bla SHV being the most common.

CONCLUSIONS

C/A and C/T were active against microorganisms with β-lactam-resistant phenotypes, except when resistance was mediated by metallo-β-lactamases. Most C/A- and C/T-resistant isolates concomitantly carried two or more β-lactamase-encoding genes (62.5% and 77.4%, respectively).

Comparative Evaluation of Vitek 2 and Etest versus Broth Microdilution for Ceftazidime/Avibactam and Ceftolozane/Tazobactam Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa

Ceftazidime/avibactam (CZA) and ceftolozane/tazobactam (C/T) are novel antibiotics with activity against multidrug-resistant Gram-negative pathogens. Nevertheless, resistance to both agents has been reported emphasizing the need for accurate and widely accessible susceptibility testing. In the present study, Vitek 2 and Etest CAZ and C/T MIC results for 100 non-repetitive clinical isolates (83 Enterobacterales and 17 P. aeruginosa, whereof 69 challenge isolates) were compared to the standard broth microdilution (BMD) method. EUCAST breakpoints were used for assessing the categorical (CA) and essential (EA) agreement between the methods along with the corresponding error rates. The Vitek 2 performance was comparable to that of BMD for testing both antimicrobial agents exceeding the ISO requirements (CA 98–99%, EA 96–100%, major errors (MEs) 0–1%, very major error (VMEs) 1%). Likewise, the Etest provided accurate results for CZA and C/T testing against Enterobacterales and P. aeruginosa, respectively (CA 100%, EA 97–100%, MEs 0%, VMEs 0%). On the contrary, EA of 85% and 6% VME rate were found for CZA Etest and P. aeruginosa. Overall, Vitek 2 measurements of CZA and C/T susceptibility correlated closely with the reference BMD, indicating that it can represent a suitable alternative to BMD for susceptibility testing of Enterobacterales and P. aeruginosa. The Etest did not fulfill the ISO performance criteria of EA and VME for CZA and P. aeruginosa. Further studies are needed to assess whether the Etest allows a reliable assessment of CZA and C/T EUCAST MICs.

The primary pharmacology of ceftazidime/avibactam: in vitro translational biology

Previous reviews of ceftazidime/avibactam have focused on in vitro molecular enzymology and microbiology or the clinically associated properties of the combination. Here we take a different approach. We initiate a series of linked reviews that analyse research on the combination that built the primary pharmacology data required to support the clinical and business risk decisions to perform randomized controlled Phase 3 clinical trials, and the additional microbiological research that was added to the above, and the safety and chemical manufacturing and controls data, that constituted successful regulatory licensing applications for ceftazidime/avibactam in multiple countries, including the USA and the EU. The aim of the series is to provide both a source of reference for clinicians and microbiologists to be able to use ceftazidime/avibactam to its best advantage for patients, but also a case study of bringing a novel β-lactamase inhibitor (in combination with an established β-lactam) through the microbiological aspects of clinical development and regulatory applications, updated finally with a review of resistance occurring in patients under treatment. This first article reviews the biochemistry, structural biology and basic microbiology of the combination, showing that avibactam inhibits the great majority of serine-dependent β-lactamases in Enterobacterales and Pseudomonas aeruginosa to restore the in vitro antibacterial activity of ceftazidime. Translation to efficacy against infections in vivo is reviewed in the second co-published article, Nichols et al. (J Antimicrob Chemother 2022; dkac172).

Identification of a KPC Variant Conferring Resistance to Ceftazidime-Avibactam from ST11 Carbapenem-Resistant Klebsiella pneumoniae Strains

A novel Klebsiella pneumoniae carbapenemase (KPC) variant, KPC-93, was identified in two Klebsiella pneumoniae clinical isolates from a patient from China treated with ceftazidime-avibactam. KPC-93 possessed a five-amino-acids insertion (Pro-Asn-Asn-Arg-Ala) between Ambler positions 267 and 268 in KPC-2. Cloning and expression of the blaKPC-93 gene in Escherichia coli, followed by determination of minimum inhibitory concentration (MIC) values and kinetic parameters, showed that KPC-93 exhibited increased resistance to ceftazidime-avibactam, but a drastic decrease in carbapenemase activity. Our data highlight that a KPC variant conferring resistance to ceftazidime-avibactam could be easily induced by ceftazidime-avibactam treatment and that actions are required to control dissemination of these determinants. IMPORTANCE Ceftazidime-avibactam (CZA) is a novel β-lactam/β-lactamase inhibitor combination with activity against serine β-lactamases, including the Ambler class A enzyme KPC. However, during recent years, there have been increasing reports of emergence of new KPC variants that could confer resistance to CZA. This has limited its clinical application. Here, we reported a new KPC variant, KPC-93, that could confer CZA resistance. KPC-93 possessed a five-amino-acids insertion (Pro-Asn-Asn-Arg-Ala) between Ambler positions 267 and 268 in KPC-2. Our findings have revealed the potential risk of blaKPC gene mutations associated with CZA exposure over a short period of time.

Efficacy of Combination Therapies for the Treatment of Multi-Drug Resistant Gram-Negative Bacterial Infections Based on Meta-Analyses

There is increasing evidence regarding the optimal therapeutic strategies for multidrug-resistant (MDR) bacteria that cause common infections and are resistant to existing antibiotics. Combination therapies, such as β-lactam combined with β-lactamase inhibitors or combination antibiotics, is a therapeutic strategy to overcome MDR bacteria. In recent years, the therapeutic options have expanded as certain combination drugs have been approved in more countries. However, only a handful of guidelines support these options, and the recommendations are based on low-quality evidence. This review describes the significance and efficacy of combination therapy as a therapeutic strategy against Gram-negative MDR pathogens based on previously reported meta-analyses.

Impact of silicone oil tamponade on intravitreally injected vancomycin pharmacokinetics in cynomolgus monkey eyes

Intravitreal injections of vancomycin (VCM) and ceftazidime (CAZ) are commonly used to treat infectious endophthalmitis. When patient cases require retinal detachment with silicone oil (SO) tamponade, the antibiotic doses are empirically reduced to 25 %. Currently, there is no scientific evidence for these empirical dose reductions. The purpose of the present study is to determine the quantitative impact that SO tamponades have on intraocular VCM pharmacokinetics. Because of high invasiveness of frequent sampling of intraocular VCM concentrations in human, this pharmacokinetic study was performed in cynomolgus monkey's eyes. Population pharmacokinetic modeling and simulation were performed using 75 different intraocular VCM concentrations obtained from 8 male cynomolgus monkeys. A one-compartment model with a first-order diffusion rate was used as a structural pharmacokinetic model. From the covariate analysis, SO tamponade significantly decreased the volume of distribution while pars plana vitrectomy with lensectomy (PPV) significantly increased the clearance and diffusion rate constants. From the Monte Carlo simulation (n = 1,000), the median time above minimum inhibitory concentration (T_>MIC, a therapeutic effect index) durations of SO and normal eyes at clinical doses of 1,000 µg were 2.6 and 11.0 days, respectively. Using intravitreal injections of VCM with SO tamponade or PPV may reduce the therapeutic effect.

Evaluation of MicroScan WalkAway for Determination of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Susceptibility in Carbapenem-Resistant Gram-Negative Bacilli

We evaluated the performance of ceftazidime-avibactam and ceftolozane-tazobactam MicroScan Neg multidrug-resistant MIC 1 (NMR1) panel for clinical carbapenem-nonsusceptible Gram-negative bacilli isolates. We evaluated 212 clinically significant carbapenem-nonsusceptible Gram-negative bacilli (139 Pseudomonas aeruginosa and 73 KPC-producing Enterobacterales) from 71 Brazilian hospitals (2013 to 2020). Ceftazidime-avibactam and ceftolozane-tazobactam MICs from the panel were compared with a broth microdilution (BMD) test as the reference method. Essential agreement (EA) and categorical agreement (CA) were assessed. For P. aeruginosa, antimicrobial susceptibility testing error rates were calculated using the error-rate bound method. Discrepancies were initially observed with 11 isolates; 4 resolved after retesting, 2 in favor of the NMR1 and 2 in favor of the BMD method. The ceftazidime-avibactam EA (overall and evaluable) was 100% for P. aeruginosa and Enterobacterales. The CA was 100% for Enterobacterales and 98.6% for P. aeruginosa. The ceftolozane-tazobactam EA was 98.6% and 100% (overall and evaluable, respectively), and the CA was 96.4% for P. aeruginosa. For ceftazidime/avibactam, no very major error (VME) was found, and the major error (ME) rate was 4.2% (2/48). For ceftolozane-tazobactam and P. aeruginosa, using the CLSI breakpoints, the minor error (mE) was 11.4%, and no VME or ME was found. While using EUCAST breakpoints, the VME was 11.4% with no ME. The mE becomes ME or VME in the absence of the intermediate category. All categorical errors were also within 1 log of MIC variation, and the adjusted error rate for CLSI/EUCAST was 0% (0/212). The NMR1 panel is an option to test ceftazidime-avibactam for KPC-producing Enterobacterales and carbapenem-nonsusceptible P. aeruginosa. When a MIC of 4 mg/liter for ceftolozane-tazobactam is obtained using this method, an alert could be created, and the results could be confirmed by an alternative method.

Pharmacokinetics and pharmacodynamics of antibiotics in cystic fibrosis: a narrative review

Cystic fibrosis affects several organs, predisposing patients to severe bacterial respiratory infections, including those caused by methicillin-resistant Staphylococcus aureus. Cystic fibrosis is also associated with a wide spectrum of pathological changes that can significantly affect the absorption, distribution, metabolism, and/or elimination of several drugs, including antibacterial agents. Therefore, awareness of the pharmacokinetic derangements in patients with cystic fibrosis is mandatory for the optimisation of antibiotic therapy. This review discusses the basic principles of pharmacokinetics and the pathophysiology of the pharmacokinetics changes associated with cystic fibrosis; it also provides an update of available data for the most widely used antibiotics. Evidence accumulated in the last few years has clearly shown that a significant number of cystic fibrosis patients treated with conventional dosing schemes have sub-therapeutic antibiotic concentrations, increasing their risk of therapeutic failure and/or the emergence of resistant pathogens. Some proposals to optimise antibiotic therapies in this clinical setting based on therapeutic drug monitoring are also discussed.

Emerging Treatment Options for Multi-Drug-Resistant Bacterial Infections

Antimicrobial resistance (AMR) remains one of the top public health issues of global concern. Among the most important strategies for AMR control there is the correct and appropriate use of antibiotics, including those available for the treatment of AMR pathogens. In this article, after briefly reviewing the most important and clinically relevant multi-drug-resistant bacteria and their main resistance mechanisms, we describe the emerging antimicrobial options for both MDR Gram-positive cocci and Gram-negative bacilli, including recently marketed agents, molecules just approved or under evaluation and rediscovered older antibiotics that have regained importance due to their antimicrobial spectrum. Specifically, emerging options for Gram-positive cocci we reviewed include ceftaroline, ceftobiprole, tedizolid, dalbavancin, and fosfomycin. Emerging treatment options for Gram-negative bacilli we considered comprise ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, aztreonam-avibactam, minocycline, fosfomycin, eravacycline, plazomicin, and cefiderocol. An exciting scenario is opening today with the long awaited growing availability of novel molecules for the treatment of AMR bacteria. Knowledge of mechanisms of action and resistance patterns allows physicians to increasingly drive antimicrobial treatment towards a precision medicine approach. Strict adherence to antimicrobial stewardship practices will allow us to preserve the emerging antimicrobials for our future.

Novel Cephalosporins in Septic Subjects and Severe Infections: Present Findings and Future Perspective

In past decade, cephalosporins have developed significantly, and data regarding novel cephalosporins (i.e., ceftobiprole, ceftaroline, ceftolozane/tazobactam, ceftazidime/avibactam, and cefiderocol) within septic and bacteremic subjects are rising. These compounds generally offer very promising in vitro microbiological susceptibility, although the variability among gram-negative and -positive strains of different cohorts is noticed in the literature. We require further pharmacological data to measure the best dose in order to prevent sub-therapeutic drug levels in critically ill patients. These new compounds in theory are the sparing solution in the Enterobacteriales infection group for different antimicrobial classes such as aminoglycosides notably within endovascular and GNB-bacteremias, as well as colistin and carbapenem-sparing strategies, favoring good safety profile molecules. Moreover, new cephalosporins are the basis for the actual indications to open up new and exciting prospects for serious infections in the future. In future, patients will be addressed with the desirable approach to sepsis and serious infections in terms of their clinical situation, inherent features of the host, the sensitivity profile, and local epidemiology, for which evidence of the use of new cephalosporin in the treatment of severe infections will fill the remaining gaps.

1,3-Diazepine: A privileged scaffold in medicinal chemistry

Privileged structures have been widely used as effective templates for drug discovery. While benzo-1,4-diazepine constitutes the first historical example of such a structure, the 1,3 analogue is just as rich in terms of applications in medicinal chemistry. The 1,3-diazepine moiety is present in numerous biological active compounds including natural products, and is used to design compounds displaying a large range of biological activities. It is present in the clinically used anticancer compound pentostatin, in several recent FDA approved β-lactamase inhibitors (e.g., avibactam) and also in coformycin, a natural product known as a ring-expanded purine analogue displaying antiviral and anticancer activities. Several other 1,3-diazepine containing compounds have entered into clinical trials. This heterocyclic structure has been and is still widely used in medicinal chemistry to design enzyme inhibitors, GPCR ligands, and so forth. This review endeavours to highlight the main use of the 1,3-diazepine scaffold and its derivatives, and their applications in medicinal chemistry, drug design, and therapy. We will focus more particularly on the development of enzyme inhibitors incorporating this scaffold, with a strong emphasis on the molecular interactions involved in the inhibition mechanism.

Guía de práctica clínica para la tamización de pacientes con riesgo de colonización por Enterobacterales productores de carbapenemasas y el manejo de infecciones causadas por estas bacterias

Las infecciones por Enterobacterales productores de carbapenemasas (EPC) han aumentado en los últimos años. Colombia se ha convertido en un país endémico para este grupo de microorganismos y las infecciones que causan tienen un impacto importante en términos de morbilidad y mortalidad. La identificación temprana de los portadores de EPC que ingresan como pacientes a las instituciones de salud es necesaria para implementar medidas de aislamiento y control de infecciones adecuadas que limiten la diseminación de este tipo de microorganismos en los hospitales. Además, el tratamiento de estas infecciones es difícil debido a las limitadas alternativas terapéuticas disponibles y la escasez de estudios que demuestren su efectividad en este escenario. Por lo anterior, el objetivo del presente trabajo es desarrollar una guía de práctica clínica (GPC) para la tamización de pacientes con riesgo de colonización por EPC y para el manejo de pacientes con   infecciones, ya sea sospechadas o confirmadas, causadas por este tipo de bacterias, mediante un proceso de adaptación de GPC basado en la metodología ADAPTE. Con este propósito en mente, se hacen recomendaciones informadas en evidencia para realizar la tamización y oportuna identificación de portadores de EPC admitidos en instituciones hospitalarias, así como para el adecuado manejo farmacológico de las infecciones por EPC en este escenario.

Recent molecules in the treatment of severe infections caused by ESBL-producing bacteria

Introduction: The widespread increase in resistance to β-lactam antibiotics in Enterobacterales currently represents one of the main threats to human health worldwide. The primary mechanisms of resistance are the production of β-lactamase enzymes that are able to hydrolyze β-lactams.Areas covered: we summarize the most recent advances regarding the main characteristics and spectrum of activity of new available antibiotics and strategies for the treatment of ESBL-producing Enterobacterales infections.Expert opinion: ESBL-producing strains are recognized as a worldwide challenge in the treatment of both hospital- and community-acquired infections. Data from the literature point out the high mortality associated with severe infections due to ESBL strains, especially in patients who developed severe sepsis or septic shock, together with the importance of the source of infection and indicators of severity, as determinants of the patient's outcome. Carbapenems are currently considered the first-line therapy, although the diffusion of resistant strains is an evolving problem and is mandatory the introduction in clinical practice of new drug regimens and treatment strategies, based on clinical data, local epidemiology, and microbiology. As a possible carbapenem-sparing strategy, ceftolozane-tazobactam and ceftazidime-avibactam appear the best-available carbapenem-sparing therapies. The definitive role of new drugs should be definitively assessed.

Restoring carbapenem efficacy: a novel carbapenem companion targeting metallo-β-lactamases in carbapenem-resistant Enterobacterales

BACKGROUND

The dissemination of MBLs compromises effective use of many β-lactams in the treatment of patients with life-threatening bacterial infections. Predicted global increases in the prevalence of MBL-producing carbapenem-resistant Enterobacterales (CRE) are being realized, yielding infections that are untreatable with existing therapies including newly approved β-lactam/β-lactamase inhibitor combinations. Developing MBL inhibitors (MBLIs) now is essential to address the growing threat that MBL-producing CRE pose to patients.

METHODS

A novel MBLI series was assessed by susceptibility testing and time-kill assays. Target activity and selectivity was evaluated using bacterial NDM, VIM and IMP enzyme assays and human matrix metallopeptidase enzyme assays, respectively, and cytotoxicity was assessed in HepG2 cells. In vivo efficacy of meropenem/MBLI combinations was evaluated in a mouse thigh infection model using an NDM-1-producing Escherichia coli strain.

RESULTS

Combination of MBLIs with carbapenems reduced MICs for NDM/IMP/VIM-producing Enterobacterales by up to 128-fold compared with the carbapenems alone. Supplementation of meropenem with the promising compound 272 reduced the MIC90 from 128 to 0.25 mg/L in a panel of MBL-producing CRE clinical isolates (n = 115). Compound 272 restored the bactericidal activity of meropenem and was non-cytotoxic, potentiating the antimicrobial action of meropenem through specific inhibition of NDM, IMP and VIM. In vivo efficacy was achieved in a mouse thigh infection model with meropenem/272 dosed subcutaneously.

CONCLUSIONS

We have developed a series of rationally designed MBLIs that restore activity of carbapenems against NDM/IMP/VIM-producing Enterobacterales. This series warrants further development towards a novel combination therapy that combats antibiotic-resistant organisms, which pose a critical threat to human health.

Safety considerations of current drug treatment strategies for nosocomial pneumonia

Introduction: Nosocomial pneumonia unfortunately remains a frequent event for which appropriate antibiotic treatment is central to improving outcomes. Physicians must choose an early and appropriate empirical treatment, basing their decision on the safety profile and possible side effects. Areas covered: In this review, we analyzed the safety profiles of the most common antimicrobials for treating nosocomial pneumonia. Beta-lactams are used most often for these infections, with a high percentage (6% to 25%) of patients reporting allergy or hypersensitivity reactions; however, exhaustive evaluation is key because it seems possible to de-label as many as 90% by proper assessment. Combinations including a beta-lactam are recommended in patients with risk factors for drug-resistant microorganisms and septic shock. Although aminoglycosides are safe for 3-5 days of therapy, renal function should be monitored. Fluoroquinolones must also be used with care given the risk of collagen degradation and cardiovascular events, mainly aneurysm or aortic dissection. Linezolid or vancomycin are both viable for the treatment of methicillin-resistant Staphylococcus aureus, but linezolid seems to be the superior option. Antibiotic stewardships programs must be developed for each center. Expert opinion: Choosing the most appropriate antimicrobial based on information from national and international guidelines, local microbiology data, and stewardship programs may reduce the use of broad-spectrum antibiotics. Daily assessment for the emergence of adverse events related to antimicrobial use is essential.

Emerging Strategies to Combat β-Lactamase Producing ESKAPE Pathogens

Since the discovery of penicillin by Alexander Fleming in 1929 as a therapeutic agent against staphylococci, β-lactam antibiotics (BLAs) remained the most successful antibiotic classes against the majority of bacterial strains, reaching a percentage of 65% of all medical prescriptions. Unfortunately, the emergence and diversification of β-lactamases pose indefinite health issues, limiting the clinical effectiveness of all current BLAs. One solution is to develop β-lactamase inhibitors (BLIs) capable of restoring the activity of β-lactam drugs. In this review, we will briefly present the older and new BLAs classes, their mechanisms of action, and an update of the BLIs capable of restoring the activity of β-lactam drugs against ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. Subsequently, we will discuss several promising alternative approaches such as bacteriophages, antimicrobial peptides, nanoparticles, CRISPR (clustered regularly interspaced short palindromic repeats) cas technology, or vaccination developed to limit antimicrobial resistance in this endless fight against Gram-negative pathogens.

New cephalosporins for the treatment of pneumonia in internal medicine wards

The burden of hospital admission for pneumonia in internal medicine wards may not be underestimated; otherwise, cases of pneumonia are a frequent indication for antimicrobial prescriptions. Community- and hospital-acquired pneumonia are characterized by high healthcare costs, morbidity and non-negligible rates of fatality. The overcoming prevalence of resistant gram-negative and positive bacteria (e.g., methicillin-resistant Staphylococcus aureus, penicillin and ceftriaxone-resistant Streptococcus pneumoniae, extended-spectrum β-lactamases and carbapenemases producing Enterobacteriaceae) has made the most of the first-line agents ineffective for treating lower respiratory tract infections. A broad-spectrum of activity, favourable pulmonary penetration, harmlessness and avoiding in some cases a combination therapy, characterise new cephalosporins such as ceftolozane/tazobactam, ceftobiprole, ceftazidime/avibactam and ceftaroline. We aimed to summarise the role and place in therapy of new cephalosporins in community- and hospital-acquired pneumonia within the setting of internal medicine wards. The “universal pneumonia antibiotic strategy” is no longer acceptable for treating lung infections. Antimicrobial therapy should be individualized considering local antimicrobial resistance and epidemiology, the stage of the illness and potential host factors predisposing to a high risk for specific pathogens.

Ceftazidime-related urinary calculi in a young boy: a case report

Certain drugs can cause kidney stones but as far as we are aware, ceftazidime-related urinary calculi have not been previously reported. We report here a case of an 8-year-old boy who developed hydronephrosis secondary to urinary calculi after receiving ceftazidime 2.0 g by intravenous infusion daily for two weeks. Previously, his left kidney showed no signs of disease. A retrograde double J ureteral stent was inserted, ceftazidime terminated, fluids increased and urine alkalised. On day 25, the patient showed no signs of kidney stones or hydronephrosis. Clinicians should be aware of the possibility of ceftazidime-related urinary calculi particularly if patients are receiving long-term treatment.

Make Sure You Have a Safety Net: Updates in the Prevention and Management of Infectious Complications in Stem Cell Transplant Recipients

Hematopoietic stem cell transplant recipients are at increased risk of infection and immune dysregulation due to reception of cytotoxic chemotherapy; development of graft versus host disease, which necessitates treatment with immunosuppressive medications; and placement of invasive catheters. The prevention and management of infections in these vulnerable hosts is of utmost importance and a key “safety net” in stem cell transplantation. In this review, we provide updates on the prevention and management of CMV infection; invasive fungal infections; bacterial infections; Clostridium difficile infection; and EBV, HHV-6, adenovirus and BK infections. We discuss novel drugs, such as letermovir, isavuconazole, meropenem-vaborbactam and bezlotoxumab; weigh the pros and cons of using fluoroquinolone prophylaxis during neutropenia after stem cell transplantation; and provide updates on important viral infections after hematopoietic stem cell transplant (HSCT). Optimizing the prevention and management of infectious diseases by using the best available evidence will contribute to better outcomes for stem cell transplant recipients, and provide the best possible “safety net” for these immunocompromised hosts.

The Role of the Ω-Loop in Regulation of the Catalytic Activity of TEM-Type β-Lactamases

Bacterial resistance to β-lactams, the most commonly used class of antibiotics, poses a global challenge. This resistance is caused by the production of bacterial enzymes that are termed β-lactamases (βLs). The evolution of serine-class A β-lactamases from penicillin-binding proteins (PBPs) is related to the formation of the Ω-loop at the entrance to the enzyme’s active site. In this loop, the Glu166 residue plays a key role in the two-step catalytic cycle of hydrolysis. This residue in TEM–type β-lactamases, together with Asn170, is involved in the formation of a hydrogen bonding network with a water molecule, leading to the deacylation of the acyl–enzyme complex and the hydrolysis of the β-lactam ring of the antibiotic. The activity exhibited by the Ω-loop is attributed to the positioning of its N-terminal residues near the catalytically important residues of the active site. The structure of the Ω-loop of TEM-type β-lactamases is characterized by low mutability, a stable topology, and structural flexibility. All of the revealed features of the Ω-loop, as well as the mechanisms related to its involvement in catalysis, make it a potential target for novel allosteric inhibitors of β-lactamases.

In-hospital management of acute complicated urinary tract infections

Upper tract urinary tract infections that require hospitalization have been the focus of national recommendations in 2018 by the French society of infectious diseases (Spilf). We here propose to discuss several complex-challenging situations: severe infection with sepsis, pyelonephritis in the pregnant woman, management of infections involving multiresistant bacteria and infection in polycystic kidney disease.

The latest advances in β-lactam/β-lactamase inhibitor combinations for the treatment of Gram-negative bacterial infections

Introduction: Antimicrobial resistance in Gram-negative pathogens is a significant threat to global health. β-Lactams (BL) are one of the safest and most-prescribed classes of antibiotics on the market today. The acquisition of β-lactamases, especially those which hydrolyze carbapenems, is eroding the efficacy of BLs for the treatment of serious infections. During the past decade, significant advances were made in the development of novel BL-β-lactamase inhibitor (BLI) combinations to target β-lactamase-mediated resistant Gram-negatives.Areas covered: The latest progress in 20 different approved, developing, and preclinical BL-BLI combinations to target serine β-lactamases produced by Gram-negatives are reviewed based on primary literature, conference abstracts (when available), and US clinical trial searches within the last 5 years. The majority of the compounds that are discussed are being evaluated as part of a BL-BLI combination.Expert opinion: The current trajectory in BLI development is promising; however, a significant challenge resides in the selection of an appropriate BL partner as well as the development of resistance linked to the BL partner. In addition, dosing regimens for these BL-BLI combinations need to be critically evaluated. A revolution in bacterial diagnostics is essential to aid clinicians in the appropriate selection of novel BL-BLI combinations for the treatment of serious infections.

Pharmacokinetic and pharmacodynamic considerations of cephalosporin use in children

Introduction: Cephalosporins are a major class of antibiotics, frequently used in children because of their remarkable antibacterial activity and excellent safety profile. Time above the minimal inhibitory concentration of the non-protein-bound fraction (fT>MIC) is the pharmacokinetic/pharmacodynamic parameter that correlates with the therapeutic efficacy. In the pediatric population, the inter-individual variability in cephalosporin pharmacokinetics is large because of maturational changes. However, the prescription of cephalosporins promotes emergence of Enterobacteriaceae producing broad-spectrum ß-lactamases.Areas covered: Here we describe in vitro activities and the main pharmacokinetic characteristics of cephalosporins in children. On the basis of these characteristics, we propose an estimation of the fT>MIC for each molecule as a tool to help optimize the use of cephalosporins. We also provide an inventory of the clinical use of cephalosporins and present prospects for the development of new molecules or associations to address the emergence of resistant strains.Expert opinion: Cephalosporins represent a heterogeneous group of antibiotics with various pharmacokinetics and in vitro antimicrobial activity that the clinician needs to master to optimize their use. However, their broad use plays a role in the emergence of broad-spectrum ß-lactamase-producing strains and must thus be restricted to probabilistic broad-spectrum therapy and situations without therapeutic alternatives.

Carbapenemases in Enterobacteriaceae: Detection and Antimicrobial Therapy

Carbapenem-resistant Enterobacteriaceae (CRE) have spread rapidly around the world in the past few years, posing great challenges to human health. The plasmid-mediated horizontal transmission of carbapenem-resistance genes is the main cause of the surge in the prevalence of CRE. Therefore, the timely and accurate detection of CRE, especially carbapenemase-producing Enterobacteriaceae, is very important for the clinical prevention and treatment of these infections. A variety of methods for the rapid detection of CRE phenotypes and genotypes have been developed for use in clinical microbiology laboratories. To overcome the lack of efficient antibiotics, CRE infections are often treated with combination therapies. Moreover, novel drugs and emerging strategies appeared successively and in various stages of development. In this article, we summarized the global distribution of various carbapenemases. And we focused on summarizing and comparing the advantages and limitations of the detection methods and the therapeutic strategies of CRE primarily.

β-Lactamases and β-Lactamase Inhibitors in the 21st Century

The β-lactams retain a central place in the antibacterial armamentarium. In Gram-negative bacteria, β-lactamase enzymes that hydrolyze the amide bond of the four-membered β-lactam ring are the primary resistance mechanism, with multiple enzymes disseminating on mobile genetic elements across opportunistic pathogens such as Enterobacteriaceae (e.g., Escherichia coli) and non-fermenting organisms (e.g., Pseudomonas aeruginosa). β-Lactamases divide into four classes; the active-site serine β-lactamases (classes A, C and D) and the zinc-dependent or metallo-β-lactamases (MBLs; class B). Here we review recent advances in mechanistic understanding of each class, focusing upon how growing numbers of crystal structures, in particular for β-lactam complexes, and methods such as neutron diffraction and molecular simulations, have improved understanding of the biochemistry of β-lactam breakdown. A second focus is β-lactamase interactions with carbapenems, as carbapenem-resistant bacteria are of grave clinical concern and carbapenem-hydrolyzing enzymes such as KPC (class A) NDM (class B) and OXA-48 (class D) are proliferating worldwide. An overview is provided of the changing landscape of β-lactamase inhibitors, exemplified by the introduction to the clinic of combinations of β-lactams with diazabicyclooctanone and cyclic boronate serine β-lactamase inhibitors, and of progress and strategies toward clinically useful MBL inhibitors. Despite the long history of β-lactamase research, we contend that issues including continuing unresolved questions around mechanism; opportunities afforded by new technologies such as serial femtosecond crystallography; the need for new inhibitors, particularly for MBLs; the likely impact of new β-lactam:inhibitor combinations and the continuing clinical importance of β-lactams mean that this remains a rewarding research area.

Scaffold hopping computational approach for searching novel β-lactamase inhibitors

We present a novel computational ligand-based virtual screening approach with scaffold hopping capabilities for the identification of novel inhibitors of β-lactamases which confer bacterial resistance to β-lactam antibiotics. The structures of known β-lactamase inhibitors were used as query ligands, and a virtual in silico screening a database of 8 million drug-like compounds was performed in order to select the ligands with similar shape and charge distribution. A set of numerical descriptors was used such as chirality, eigen spectrum of matrices of interatomic distances and connectivity together with higher order moment invariants that showed their efficiency in the field of pattern recognition but have not yet been employed in drug discovery. The developed scaffold-hopping approach was applied for the discovery of analogues of four allosteric inhibitors of serine β-lactamases. After a virtual in silico screening, the effect of two selected ligands on the activity of TEM type β-lactamase was studied experimentally. New non-β-lactam inhibitors were found that showed more effective inhibition of β-lactamases compared to query ligands.

Retrospective Observational Study from a Chinese Network of the Impact of Combination Therapy versus Monotherapy on Mortality from Carbapenem-Resistant Enterobacteriaceae Bacteremia

Data for a total of 164 bloodstream infection cases due to carbapenem-resistant Enterobacteriaceae (CRE) from 2013 to 2017 were retrospectively collected from 36 tertiary hospitals in 19 provinces in China to evaluate the outcomes and risk factors for mortality by univariable and multivariable analysis. The most frequent infecting species was Klebsiella pneumoniae (69.5%, 114/164). The overall in-hospital and 14-day mortality rates were 32.9% (54/164) and 31.1% (42/135), respectively. Multivariable analysis revealed that septic shock (adjusted odds ratio [aOR], 6.339; 95% confidence interval [CI], 1.586 to 25.332; P = 0.009), the Pitt bacteremia score (aOR, 1.300; 95% CI, 1.009 to 1.676; P = 0.042), and the Charlson comorbidity index (aOR, 1.392; 95% CI, 1.104 to 1.755; P = 0.005) were independently associated with a hazard effect on mortality. Combination therapy, especially tigecycline-based combination therapy, resulted in relatively low rates of in-hospital mortality and failure in clearance of CRE infection. Survival analysis revealed that appropriate therapy was associated with a lower 14-day mortality rate than inappropriate therapy (including nonactive therapy; P = 0.022), that combination therapy was superior to monotherapy (P = 0.036), that metallo-β-lactamase producers were associated with a lower 14-day mortality than strains without carbapenemases or KPC-2 producers (P = 0.009), and that strains with MICs of >8 mg/liter for meropenem were associated with a higher 14-day mortality rate than those with MICs of ≤8 mg/liter (P = 0.037). Collectively, the severity of illness, meropenem MICs of >8 mg/liter, and carbapenemase-producing types were associated with the clinical outcome. Early detection of the carbapenemase type and initiation of appropriate combination therapy within 96 h might be helpful for improving survival.

Evaluation of the efficacy and safety of ceftazidime/avibactam in the treatment of Gram-negative bacterial infections: a systematic review and meta-analysis

Data on the efficacy and safety of ceftazidime/avibactam (CAZ-AVI) are limited. A systematic review and meta-analysis was conducted to clarify the role of CAZ-AVI for patients with serious Gram-negative bacterial infections. The PubMed, EMBASE and Cochrane Library databases were searched for randomised controlled trials (RCTs) and cohort studies involving CAZ-AVI. Summary risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using a fixed- or random-effects model. Twelve articles (4951 patients) were included, consisting of nine RCTs and three observational studies comparing CAZ-AVI with other regimens, e.g. carbapenems or colistin. CAZ-AVI showed a comparable clinical response (RR = 0.99, 95% CI 0.96-1.02; I2 = 0%) and non-inferior bacterial eradication (RR = 1.04, 95% CI 0.93-1.17; I2 = 79.1%) to carbapenems. No significant difference was detected between groups regarding mortality and adverse events. Moreover, subgroup analyses demonstrated that CAZ-AVI improved the clinical response (RR = 1.61, 95% CI 1.13-2.29) with reduced mortality (RR = 0.29, 95% CI 0.13-0.63) in patients infected by carbapenem-resistant Enterobacteriaceae versus comparators. Likewise, CAZ-AVI improved the clinical cure rate of bloodstream infections (RR = 2.11, 95% CI 1.54-2.88). An improved ability of CAZ-AVI in microbiological eradication was also detected in patients with complicated urinary tract infections (RR = 1.13, 95% CI 1.05-1.21). CAZ-AVI exhibited comparable efficacy and safety with carbapenems. Therefore, this agent might be a potential powerful agent for patients with serious Gram-negative bacterial infections.