New Drugs for Multidrug-Resistant Gram-Negative Organisms: Time for Stewardship

Genomic insights into bla AFM-positive carbapenem-resistant Pseudomonas aeruginosa in China

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a global threat; however, the epidemiological characteristics and clinical significance of bla AFM-positive CRPA strains in China remain unclear. In this study, continuous surveillance was conducted from 2018 to 2022 in a hospital in Henan Province, China, and the genomic characteristics of bla AFM-positive CRPA were elucidated. We characterised the genetic features of bla AFM-positive CRPA isolates by antimicrobial susceptibility testing, conjugation assays, whole-genome sequencing, large-scale comparative genomics, and bioinformatic analyses. Among 628 CRPA isolates, one bla AFM-positive multidrug-resistant (MDR) strain, PA19-3158 (ST1123), was identified, with the bla AFM-1 gene located on a novel 518,222 bp megaplasmid. Additionally, big data analysis revealed the genomic characteristics of bla AFM-positive CRPA across China. A total of three different bla AFM gene variants were identified among these isolates, namely bla AFM-1 (44.12%), bla AFM-2 (52.94%), and bla AFM-4 (2.94%). Our findings identified ST463 as the dominant clone among bla AFM-positive CRPA in different regions of China, with some bla AFM-positive CRPA isolates from these regions exhibiting high genetic similarity. Notably, all bla AFM-positive CRPA isolates carried multiple antibiotic resistance genes (ARGs), with approximately 38% co-harboring the carbapenem-resistant gene bla KPC-2 and approximately 47% co-harboring the tigecycline-resistant gene tmexCD-toprJ. Correlation analysis underscored the significant role of mobile genetic elements in facilitating bla AFM gene transfer. These results highlight the critical need for continuous surveillance of bla AFM-positive CRPA in clinical settings to mitigate potential risks.

Pharmacokinetic, Pharmacokinetic/Pharmacodynamic, and Safety Investigations of Cefiderocol in Chinese Healthy Subjects

INTRODUCTION

We aim to evaluate the safety and pharmacokinetic (PK) properties of cefiderocol in Chinese participants, following single and subsequent multiple administrations of 2 g q8h with 3-h intravenous infusion, and to predict its efficacy for the treatment of Gram-negative bacilli (GNB) infection based on PK/pharmacodynamic (PD) analysis.

METHODS

This was an open-label, single-center, single- and multiple-dose phase I study, conducted from September 2022 to October 2022, with 12 eligible healthy Chinese adults (6 men and 6 women). The PK profiles were described by noncompartmental analysis and a two-compartment model using WinNonlin (v.8.1). Monte Carlo simulations (MCS) were performed by R (v.4.3.1) to obtain the probability of target attainment (PTA) as well as the cumulative fraction of response (CFR), based on the previously published data of susceptibility studies for cefiderocol in China.

RESULTS

Both single and multiple doses of 2 g cefiderocol were well tolerated in healthy Chinese subjects, and no severe treatment-emergent adverse events occurred. The maximum plasma concentration of cefiderocol was observed approximately 3 h after administration and the half-life was about 2.6 h, with no accumulation after multiple dosing. It is worth noting that, the PK profiles, including CL, V1, Cmax, Ctrough, and AUC0-τ, were consistent with those of other populations, e.g., Caucasian. PK/PD analysis and MCS suggested that standard dosage regimen of cefiderocol would achieve satisfactory PTA and CFR (exceeding 90%) for Gram-negative pathogens with MICs up to 4 μg/mL, using the proposed fT>MIC target of 75.0%. Consistently, more than 90% of PTA was reached for Enterobacterales, P. aeruginosa, and Acinetobacter spp. with MICs up to 4 μg/mL at their respective 73.3%, 72.2%, and 88.1% fT>MIC targets, with CFR exceeding 95%. Especially for S. maltophilia, both the PTA and CFR reached nearly 100% for those with MICs as high as 8 μg/mL.

CONCLUSIONS

Cefiderocol is well tolerated by Chinese healthy participants at the dosage regimen of 2 g cefiderocol q8h via 3-h infusion, which is expected to achieve satisfactory efficacy in treating GNB infections in China, although further data for model optimization might still be required. To our knowledge, this is the first study to describe the PK properties of cefiderocol in Chinese subjects, and to predict its microbiological efficacy for treating GNB infection in China.

TRIAL REGISTRATION

ChiCTR2300076607.

Rare or Unusual Non-Fermenting Gram-Negative Bacteria: Therapeutic Approach and Antibiotic Treatment Options

Non-fermenting Gram-negative bacteria (NFGNB) are a heterogeneous group of opportunistic pathogens increasingly associated with healthcare-associated infections. While Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia are well known, rarer species such as Burkholderia cepacia complex, Achromobacter spp., Chryseobacterium spp., Elizabethkingia spp., Ralstonia spp., and others pose emerging therapeutic challenges. Their intrinsic and acquired resistance mechanisms limit effective treatment options, making targeted therapy essential. Objectives: This narrative review summarizes the current understanding of rare and unusual NFGNB, their clinical significance, resistance profiles, and evidence-based therapeutic strategies. Methods: A literature review was conducted using PubMed, Scopus, and Web of Science to identify relevant studies on the epidemiology, antimicrobial resistance, and treatment approaches to rare NFGNB. Results: Rare NFGNB exhibits diverse resistance mechanisms, including β-lactamase production, efflux pumps, and porin modifications. Treatment selection depends on species-specific susceptibility patterns, but some cornerstones can be individuated. Novel β-lactam/β-lactamase inhibitors and combination therapy approaches are being explored for multidrug-resistant isolates. However, clinical data remain limited. Conclusions: The increasing incidence of rare NFGNB requires heightened awareness and a tailored therapeutic approach. Given the paucity of clinical guidelines, antimicrobial stewardship and susceptibility-guided treatment are crucial in optimizing patient outcomes.

High prevalence of carbapenem-resistant Pseudomonas aeruginosa and identification of a novel VIM-type metallo-β-lactamase, VIM-92, in clinical isolates from northern China

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has become a serious global health concern due to the limited treatment options. The primary resistance mechanism in CRPA involves the production of metallo-β-lactamases (MBLs), making MBL-producing P. aeruginosa a significant component of CRPA cases. To understand the prevalence of CRPA in hospitals in northern China, we conducted a preliminary screening and identification of CRPA in 143 clinical isolates of P. aeruginosa collected from various departments of a tertiary hospital between 2021 and 2023, analyzing CRPA resistance trends in certain regions of northern China during this period. We identified 71 CRPA isolates that exhibited high carbapenem resistance and phylogenetic tree analysis revealed that ST244 CRPA isolates had widely spread across various departments of the same hospital over three consecutive years. We also identified two VIM-producing isolates, PJK40 and PJK43, both of which carried the same novel VIM-type metallo-β-lactamase, VIM-92, encoded by a newly identified gene, bla VIM-92, closely related to bla VIM-24. bla VIM-92 was embedded in class 1 integrons within the Tn1403 transposon. The bla VIM-92-carrying plasmid, pPJK40, was found to resemble the pJB37 megaplasmid. The expression of VIM-92 and VIM-24 in DH5α and PAO1 revealed similar effects of the MICs of β-lactams, except for aztreonam. The high prevalence of CRPA in clinical settings, and the identification of VIM-92, highlights the urgent need for ongoing surveillance of CRPA and emerging MBL variants in P. aeruginosa.

Direct Klebsiella pneumoniae Carbapenem Resistance and Carbapenemases Genotype Prediction by Al-MOF/TiO2@Au Cubic Heterostructures-Assisted Intact Bacterial Cells Metabolic Analysis

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections pose a significant threat to human health. Fast and accurate prediction of K. pneumoniae carbapenem resistance and carbapenemase genotype is critical for guiding antibiotic treatment and reducing mortality rates. In this study, we present a novel method using Al-MOF/TiO2@Au cubic heterostructures for the metabolic analysis of intact bacterial cells, enabling rapid diagnosis of CRKP and its carbapenemases genotype. The Al-MOF/TiO2@Au cubic composites display strong light absorption and high surface area, facilitating the in situ effective extraction of metabolic fingerprints from intact bacterial cells. Utilizing this method, we rapidly and sensitively extracted metabolic fingerprints from 169 clinical isolates of K. pneumoniae obtained from patients. Machine learning analysis of the metabolic fingerprint changes successfully distinguishes CRKP from the sensitive strains, achieving the high area under the curve (AUC) values of 1.00 in both training and testing sets based on the 254 m/z features, respectively. Additionally, this platform enables rapid carbapenemase genotype discrimination of CRKP for precision antibiotic therapy. Our strategy holds great potential for swift diagnosis of CRKP and carbapenemase genotype discrimination, guiding effective management of CRKP bacterial infections in both hospital and community settings.

Comparison of Different Methods for Assaying the In Vitro Activity of Cefiderocol against Carbapenem-Resistant Pseudomonas aeruginosa Strains: Influence of Bacterial Inoculum

Carbapenem-resistant Pseudomonas aeruginosa infections represent a critical public health concern, highlighting the need for the development of effective antibiotics. Cefiderocol demonstrated potent in vitro activity against Pseudomonas aeruginosa, particularly in strains that are resistant to other drugs. However, concerns regarding the emergence of drug-resistant strains persist. This study, conducted with 109 carbapenem-resistant Pseudomonas aeruginosa strains from the Spanish Hospital (Dr. Balmis, Alicante). The study evaluated susceptibility to cefiderocol in comparison to alternative antibiotics and including their susceptibility to bacterial inoculum, while assessing various testing methods. Our findings revealed high susceptibility to cefiderocol against carbapenem-resistant strains, with only 2 of 109 strains exhibiting resistance. Comparative analysis demonstrated superiority of cefiderocol towards alternative antibiotics. Both the E-test and disk-diffusion methods showed 100% concordance with the microdilution method in classifying strains as susceptible or resistant. However, 4.6% (5/109) of disc zone diameters fell within the technical uncertainty zone, so the E-test technique was found to be more useful in routine clinical practice. Additionally, escalating bacterial inoculum correlated with decreases in vitro activity, so this parameter should be adjusted very carefully in in vivo studies. This study underscores cefiderocol's potential as a therapeutic option for carbapenem-resistant Pseudomonas aeruginosa infections. However, the emergence of drug-resistant strains emphasizes the critical need for a wise use of antibiotics and a continuous monitoring of resistance to antibiotics. Based on our in vitro data, further investigation concerning the impact of bacterial inoculum on drug efficacy is warranted in order to detect resistance mechanisms and optimize treatment strategies, thereby mitigating the risk of resistance.

Effectiveness of novel β-lactams for Pseudomonas aeruginosa infection: A systematic review and meta-analysis

BACKGROUND

Novel β-lactams have in vitro activity against Pseudomonas aeruginosa (PA), but their clinical performances and the selection criteria for practical use are still not clear. We aimed to evaluate the efficacy of novel β-lactams for PA infection in various sites and to compare the efficacy of each agent.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science for randomized controlled trials that used novel β-lactams to treat PA infection. The primary outcomes were clinical cure and favorable microbiological response. Subgroup analyses were performed based on drug type, drug resistance of pathogens, and site of infection. Network meta-analysis was carried out within a Bayesian framework.

RESULTS

In all studies combined (16 randomized controlled trials), novel β-lactams indicated comparable performance to other treatment regimens in both outcome measures (relative risk = 1.04; 95% confidence interval 0.94-1.15; P = .43) (relative risk = 0.97; 95% confidence interval 0.81-1.17; P = .76). Subgroup analyses showed that the efficacy of ceftolozane-tazobactam (TOL-TAZ), ceftazidime-avibactam (CAZ-AVI), imipenem-cilastatin-relebactam, and cefiderocol had no apparent differences compared to control groups among different infection sites, drug types and drug resistance of PA. In network meta-analysis, the results showed no statistically significant differences between TOL-TAZ, CAZ-AVI, and cefiderocol.

CONCLUSIONS

TOL-TAZ, CAZ-AVI, imipenem-cilastatin-relebactam, and cefiderocol are not inferior to other agents in the treatment of PA infection. Their efficacy is also comparable between TOL-TAZ, CAZ-AVI, and cefiderocol.

Comparison of ERIC carbapenem-resistant Enterobacteriaceae test, BD Phoenix CPO detect panel, and NG-test CARBA 5 for the detection of main carbapenemase types of carbapenem-resistant Enterobacterales

BACKGROUND

This study aimed to assess the performance of three commercial panels, the ERIC Carbapenem-Resistant Enterobacteriaceae Test (ERIC CRE test), the NG-Test CARBA 5 (NG CARBA 5), and the BD Phoenix CPO Detect Panel (CPO panel), for the detection of main types of carbapenemases among carbapenem-resistant Enterobacterales (CRE).

METHODS

We collected 502 isolates of carbapenem-resistant Enterobacterales (CRE) demonstrating intermediate or resistant profiles to at least one carbapenem antibiotic (ertapenem, imipenem, meropenem, or doripenem). Carbapenemase genes and their specific types were identified through multiplex PCR and sequencing methods. Subsequently, the ERIC CRE test, CPO panel, and NG CARBA 5 assay were conducted on these isolates, and the results were compared with those obtained from multiplex PCR.

RESULTS

The results indicated that the ERIC CRE test exhibited an overall sensitivity and specificity of 98.1% and 93.6%, respectively, which were comparable to 99.1% and 90.6% for the NG CARBA 5. However, the CPO panel demonstrated a sensitivity of only 56.2% in identifying Ambler classes, exhibiting the poorest sensitivity for class A. Moreover, while the ERIC CRE test outperformed the NG CARBA 5 in identifying multi-gene isolates with multiple carbapenemase-encoding genes, the CPO panel failed to accurately classify these isolates.

CONCLUSIONS

Our findings support the utilization of the ERIC CRE test as one of the methods for detecting carbapenemases in clinical laboratories. Nonetheless, further optimization is imperative for the CPO panel to enhance its accuracy in determining carbapenemase classification and address limitations in detecting multi-gene isolates.

Pharmacokinetics and Nephrotoxicity of Polymyxin MRX-8 in Rats: A Novel Agent against Resistant Gram-Negative Bacteria

MRX-8 is a novel polymyxin for carbapenem-resistant Gram-negative infections that has been recently evaluated in Phase I clinical trials. Herein, its pharmacokinetics (PK) and nephrotoxicity in rats are reported for the first time. This study aimed at pre-clinical PK and safety assessments. An LC-MS/MS method was developed to determine concentrations of MRX-8 and its major deacylation metabolite, MRX-8039, in rat plasma. Animals were administered a single dose of MRX-8 (2, 4, 6, and 8 mg/kg) or comparator polymyxin B (PMB) (4 and 8 mg/kg) to compare the kidney injury known for the polymyxin drug class. Nephrotoxicity was evaluated using serum creatinine, blood urea nitrogen (BUN) biomarkers, and renal histopathology. In rats, MRX-8 displayed linear PK within the range of 2-8 mg/kg, with approximately 4% of MRX-8 converted to MRX-8039. MRX-8 induced only mild increases in serum creatinine and BUN levels, with an apparent decrease in nephrotoxicity within 24 h, in contrast to PMB, which exhibited a significant and more persistent toxicity. Additional nephrotoxicity biomarkers (plasma NGAL and urinary NGAL, KIM-1, and TIMP-1) have confirmed attenuated MRX-8 kidney injury. Histopathology has revealed significantly greater cellular/tissue toxicity for PMB as compared to MRX-8 (variances of p = 0.008 and p = 0.048 vs. saline control, respectively). Thus, MRX-8 induces a mild and reversible kidney injury in rats compared to PMB. These data support a continued evaluation of the novel polymyxin in human trials.

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

OBJECTIVE

This study aimed to indicate whether a declined plasma concentration of valproic acid (VPA) induced by co-administration of meropenem (MEPM) could affect the antiepileptic efficacy of VPA.

METHODS

We retrospectively reviewed data of hospitalized patients who were diagnosed with status epilepticus or epilepsy between 2010 and 2019. Patients co-administered VPA and MEPM during hospitalization were screened and assigned to the exposure group, while those co-administerd VPA and other broad-spectrum antibiotics were allocated to the control group.

RESULTS

The exposure group and control group included 50 and 11 patients, respectively. With a similar dosage of VPA, the plasma concentration of VPA significantly decreased during co-administration (24.6 ± 4.3 μg/mL) compared with that before co-administration (88.8 ± 13.6 μg/mL, p < 0.0001), and it was partly recovered with the termination of co-administration (39.8 ± 13.2 μg/mL, p = 0.163) in the exposure group. The inverse probability of treatment weighting estimated the treatment efficacy via changes in seizure frequency, seizure duration, and concomitant use of antiepileptic drugs, which were not significantly different between the exposure and control groups. In the exposure group, there was no significant differences in seizure frequency between the periods of before-during and before-after (p = 0.074 and 0.153, respectively). Seizure duration during VPA-MEPM co-administration was not significantly different from that before co-administration (p = 0.291).

CONCLUSIONS

In this study, the reduced plasma concentration of VPA induced by the co-administration of MEPM did not affect the antiepileptic efficacy of VPA. This conclusion should be interpreted with caution, and more research is warranted.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2000034567. Registered on 10 July 2020.

New advances in management and treatment of cardiac implantable electronic devices infections

Cardiac implantable electronic devices (CIED) are increasingly used worldwide, and infection of these devices remains one of the most feared complications.CIED infections (CDIs) represent a challenge for physicians and the healthcare system in general as they require prolonged hospitalization and antibiotic treatment and are burdened by high mortality and high costs, so management of CDIs must be multidisciplinary.The exact incidence of CDIs is difficult to define, considering that it is influenced by various factors mainly represented by the implanted device and the type of procedure. Risk factors for CDIs could be divided into three categories: device related, patient related, and procedural related and the etiology is mainly sustained by Gram-positive bacteria; however, other etiologies cannot be underestimated. As a matter of fact, the two cornerstones in the treatment of these infections are device removal and antimicrobial treatment. Finally, therapeutic drug monitoring and PK/PD correlations should be encouraged in all patients with CDIs receiving antibiotic therapy and may result in a better clinical outcome and a reduction in antibiotic resistance and economic costs.In this narrative review, we look at what is new in the management of these difficult-to-treat infections.

Emergence of carbapenem resistant gram-negative pathogens with high rate of colistin resistance in Egypt: A cross sectional study to assess resistance trends during the COVID-19 pandemic

The current study investigated the temporal phenotypic and genotypic antimicrobial resistance (AMR) trends among multi-drug resistant and carbapenem-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa recovered from Egyptian clinical settings between 2020 and 2021. Bacterial identification and antimicrobial sensitivity of 111 clinical isolates against a panel of antibiotics were performed. Molecular screening for antibiotic resistance determinants along with integrons and associated gene cassettes was implemented. An alarming rate (98.2%) of these isolates were found to be phenotypically resistant to carbapenem. Although 23.9 % K. pneumoniae isolates were phenotypically resistant to colistin, no mobile colistin resistance (mcr) genes were detected. Among carbapenem-resistant isolates, blaNDM and blaOXA-48-like were the most prevalent genetic determinants and were significantly overrepresented among K. pneumoniae. Furthermore, 84.78% of K. pneumoniae isolates co-produced these two carbapenemase genes. The plasmid-mediated quinolone resistance genes (qnrS and qnrB) were detected among the bacterial species and were significantly more prevalent among K. pneumoniae. Moreover, Class 1 integron was detected in 82% of the bacterial isolates. This study alarmingly reveals elevated resistance to last-resort antibiotics such as carbapenems as well as colistin which impose a considerable burden in the health care settings in Egypt. Our future work will implement high throughput sequencing-based antimicrobial resistance surveillance analysis for characterization of novel AMR determinants. This information could be applied as a step forward to establish a robust antibiotic stewardship program in Egyptian clinical settings, thereby addressing the rising challenges of AMR.

Cefiderocol: early clinical experience for multi-drug resistant gram-negative infections

Multi-drug resistant gram-negative bacteria present a significant global health threat. Cefiderocol (CFDC), a siderophore cephalosporin, has shown potential in combating this threat, but with the currently available data, its role in therapy remains poorly defined. This multi-center, retrospective cohort study evaluated the real-world application of CFDC across six U.S. medical centers from January 2018 to May 2023. Patients aged ≥18 years and who had received ≥72 hours of CFDC were included. The primary outcome was a composite of clinical success: survival at 30 days, absence of symptomatic microbiologic recurrence at 30 days following CFDC treatment initiation, and resolution of signs and symptoms. Secondary outcomes included time to CFDC therapy and on-treatment non-susceptibility to CFDC. A total of 112 patients were included, with median (interquartile range [IQR]) APACHE II scores of 15 (19-18). Clinical success was observed in 68.8% of patients, with a mortality rate of 16.1% and comparable success rates across patients infected with carbapenem-resistant gram-negative infections. The most common isolated organisms were Pseudomonas aeruginosa (61/112, 54.5%, of which 55/61 were carbapenem-resistant) and carbapenem-resistant Acinetobacter baumannii (32/112, 28.6%). Median (IQR) time to CFDC therapy was 77 (14-141) hours. Two patients experienced a non-anaphylactic rash as an adverse drug reaction. On-treatment non-susceptibility to CFDC was found in six patients, notably due to P. aeruginosa and A. baumannii.IMPORTANCECFDC was safe and clinically effective as a monotherapy or in combination in treating a variety of carbapenem-resistant gram-negative infections. Further prospective studies are warranted to confirm these findings.

Quinolone-3-amidoalkanol: A New Class of Potent and Broad-Spectrum Antimicrobial Agent

Herein, we describe 39 novel quinolone compounds bearing a hydrophilic amine chain and varied substituted benzyloxy units. These compounds demonstrate broad-spectrum activities against acid-fast bacterium, Gram-positive and -negative bacteria, fungi, and leishmania parasite. Compound 30 maintained antitubercular activity against moxifloxacin-, isoniazid-, and rifampicin-resistant Mycobacterium tuberculosis, while 37 exhibited low micromolar activities (<1 μg/mL) against World Health Organization (WHO) critical pathogens: Cryptococcus neoformans, Acinetobacter baumannii, and Pseudomonas aeruginosa. Compounds in this study are metabolically robust, demonstrating % remnant of >98% after 30 min in the presence of human, rat, and mouse liver microsomes. Several compounds thus reported here are promising leads for the treatment of diseases caused by infectious agents.

Omadacycline for treatment of acute bacterial infections: a meta-analysis of phase II/III trials

OBJECTIVE

This study aims to assess the clinical efficacy and safety of omadacycline for the treatment of acute bacterial infections.

METHODS

A search of PubMed, Embase, Cochrane Library, and Clinical Trials was conducted up to July 1, 2022. We included only randomized controlled trials (RCTs), in which omadacycline and other antibiotics were evaluated for treating acute bacterial infections in adults. The primary outcomes were clinical response and microbiological response, whereas the secondary outcome was the risk of adverse events (AEs).

RESULTS

A total of seven RCTs involving 2841 patients with acute bacterial infection were included. Overall, our study illustrated that the clinical cure ratio of omadacycline was similar to the comparators in the treatment of acute bacterial infections (OR = 1.18, 95%CI = 0.96, 1.46, I² = 29%). Omadacycline had a microbiological eradication rate similar to comparators in the treatment of acute bacterial infections (OR = 1.02, 95%CI = 0.81, 1.29, I² = 42%). No statistical differences were observed between omadacycline and the comparators in terms of infection caused by Staphylococcus aureus (OR = 1.14, 95%CI = 0.80, 1.63, I² = 0%), methicillin-resistant S. aureus (MRSA, OR = 1.28, 95%CI = 0.73, 2.24, I² = 0%), methicillin-susceptible S. aureus (MSSA, OR = 1.12, 95%CI = 0.69, 1.81, I² = 0%), and Enterococcus faecalis (OR = 2.47, 95%CI = 0.36, 16.97, I² = 7%). A significant difference was found between omadacycline and the comparators for the risk of any AEs and treatment related AEs. The risk of discontinuation of the study drug due to an AEs was lower for omadacycline than for the comparators.

CONCLUSION

Omadacycline is as good as comparators in terms of efficacy and tolerance in the treatment of acute bacterial infections in adult patients. Thus, omadacycline is an appropriate option for antibiotic therapy in adult patients with acute bacterial infections.

Neutralizing Carbapenem Resistance by Co-Administering Meropenem with Novel β-Lactam-Metallo-β-Lactamase Inhibitors

Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an urgent global need for clinical metallo-β-lactamase inhibitors (MBLIs) has become dire. To address this problem, this study evaluated BP2, a novel beta-lactam-derived β-lactamase inhibitor, co-administered with meropenem. According to the antimicrobial susceptibility results, BP2 potentiates the synergistic activity of meropenem to a minimum inhibitory concentration (MIC) of ≤1 mg/L. In addition, BP2 is bactericidal over 24 h and safe to administer at the selected concentrations. Enzyme inhibition kinetics showed that BP2 had an apparent inhibitory constant (K_iapp) of 35.3 µM and 30.9 µM against New Delhi Metallo-β-lactamase (NDM-1) and Verona Integron-encoded Metallo-β-lactamase (VIM-2), respectively. BP2 did not interact with glyoxylase II enzyme up to 500 µM, indicating specific (MBL) binding. In a murine infection model, BP2 co-administered with meropenem was efficacious, observed by the >3 log₁₀ reduction in K. pneumoniae NDM cfu/thigh. Given the promising pre-clinical results, BP2 is a suitable candidate for further research and development as an (MBLI).

Direct prediction of carbapenem-resistant, carbapenemase-producing, and colistin-resistant Klebsiella pneumoniae isolates from routine MALDI-TOF mass spectra using machine learning and outcome evaluation

The objective of this study was to develop a rapid prediction method for carbapenem-resistant Klebsiella pneumoniae (CRKP) and colistin-resistant K. pneumoniae (ColRKP) based on routine MALDI-TOF mass spectrometry (MS) results in order to formulate a suitable and rapid treatment strategy. In total, 830 CRKP and 1,462 carbapenem-susceptible K. pneumoniae (CSKP) isolates were collected; 54 ColRKP isolates and 1,592 colistin-intermediate K. pneumoniae (ColIKP) isolates were also included. Routine MALDI-TOF MS, antimicrobial susceptibility testing, NG-Test CARBA 5, and resistance gene detection were followed by machine learning (ML). Using the ML model, the accuracy and area under the curve for differentiating CRKP and CSKP were 0.8869 and 0.9551, and those for ColRKP and ColIKP were 0.8361 and 0.8447, respectively. The most important MS features of CRKP and ColRKP were m/z 4520-4529 and m/z 4170-4179, respectively. Of the CRKP isolates, MS m/z 4520-4529 was a potential biomarker for distinguishing KPC from OXA, NDM, IMP, and VIM. Of the 34 patients who received preliminary CRKP ML prediction results (by texting), 24 (70.6%) were confirmed to have CRKP infection. The mortality rate was lower in patients who received antibiotic regimen adjustment based on the preliminary ML prediction (4/14, 28.6%). In conclusion, the proposed model can provide rapid results for differentiating CRKP and CSKP, as well as ColRKP and ColIKP. The combination of ML-based CRKP with preliminary reporting of results can help physicians alter the regimen approximately 24 h earlier, resulting in improved survival of patients with timely antibiotic intervention.

Off-label use versus formal recommendations of conventional and novel antibiotics for the treatment of infections caused by multidrug-resistant bacteria

The infections caused by multidrug- and extensively drug-resistant (MDR, XDR) bacteria, including Gram-positive cocci (GPC, including methicillin-resistant Staphylococcus aureus, MDR-Streptococcus pneumoniae and vancomycin-resistant enterococci) and Gram-negative bacilli (GNB, including carbapenem-resistant [CR] Enterobacterales, CR-Pseudomonas aeruginosa and XDR/CR-Acinetobacter baumannii complex) can be quite challenging for physicians with respect to treatment decisions. Apart from complicated urinary tract and intra-abdominal infections (cUTIs, cIAIs), bloodstream infections and pneumonia, these difficult-to-treat bacteria also cause infections at miscellaneous sites (bones, joints, native/prosthetic valves and skin structures, etc.). Antibiotics like dalbavancin, oritavancin, telavancin and daptomycin are currently approved for the treatment of acute bacterial skin and skin structural infections (ABSSSIs) caused by GPC. Additionally, ceftaroline, linezolid and tigecycline have been formally approved for the treatment of community-acquired pneumonia and ABSSSI. Cefiderocol and meropenem-vaborbactam are currently approved for the treatment of cUTIs caused by XDR-GNB. The spectra of ceftazidime-avibactam and imipenem/cilastatin-relebactam are broader than that of ceftolozane-tazobactam, but these three antibiotics are currently approved for the treatment of hospital-acquired pneumonia, cIAIs and cUTIs caused by MDR-GNB. Clinical investigations of other novel antibiotics (including cefepime-zidebactam, aztreonam-avibactam and sulbactam-durlobactam) for the treatment of various infections are ongoing. Nevertheless, evidence for adequate antibiotic regimens against osteomyelitis, arthritis and infective endocarditis due to several GPC and MDR-GNB is still mostly lacking. A comprehensive review of PubMed publications was undertaken and the formal indications and off-label use of important conventional and novel antibiotics against MDR/XDR-GPC and GNB isolates cultured from miscellaneous sites are presented in this paper.

Antimicrobial stewardship programs in the Intensive Care Unit in patients with infections caused by multidrug-resistant Gram-negative bacilli

Antimicrobial stewardship programs (ASPs) have been shown to be effective and safe, contributing to reducing and adjusting antimicrobial use in clinical practice. Such programs not only reduce antibiotic selection pressure and therefore the selection of multidrug-resistant strains, but also reduce the potential deleterious effects for individual patients and even improve the prognosis by adjusting the choice of drug and dosage, and lessening the risk of adverse effects and interactions. Gram-negative bacilli (GNB), particularly multidrug-resistant strains (MDR-GNB), represent the main infectious problem in the Intensive Care Unit (ICU), and are therefore a target for ASPs. The present review provides an update on the relationship between ASPs and MDR-GNB.

"CORE" a new assay for rapid identification of Klebsiella pneumoniae COlistin REsistant strains by MALDI-TOF MS in positive-ion mode

Due to the global spread of pan resistant organisms, colistin is actually considered as one of the last resort antibiotics against MDR and XDR bacterial infections. The emergence of colistin resistant strains has been observed worldwide in Gram-negative bacteria, such as Enterobacteriaceae and especially in K. pneumoniae, in association with increased morbidity and mortality. This landscape implies the exploration of novel assays able to target colistin resistant strains rapidly. In this study, we developed and evaluated a new MALDI-TOF MS assay in positive-ion mode that allows quantitative or qualitative discrimination between colistin susceptible (18) or resistant (32) K. pneumoniae strains in 3 h by using the "Autof MS 1000" mass spectrometer. The proposed assay, if integrated in the diagnostic workflow, may be of help for the antimicrobial stewardship and the control of the spread of K. pneumoniae colistin resistant isolates in hospital settings.

Use of Ginger Essential Oil with Cephalosporin antibiotics as Beta-Lactamase inhibitors in pharmaceutical design to fight Escherichia coli UTI

This research aimed to investigate multi-target inhibitors against the Beta-Lactamases protein of urinary tract infections (UTI) Escherichia coli, which is considered the main virulence factor of this bacterium. Drug design is regarded as a new approach to drug discovery and industry. The combination of Ginger Essential Oil (GEO) and Cefepime (FEP) showed effective results against Beta-Lactamase enzymes of UTI E.coli, 512 FEP+ 100% GEO and 1024 FEP + 100% GEO for (20 mm and 26 mm) inhibition zone respectively. The present study concluded that the isolates of E.coli of UTI from Iraqi hospitals were MDR and XDR, and their virulence was due to the presence of blaTEM genes. In silico screening, servers have been used to design an inhibitor model for Beta-Lactamases from the natural product of GEO. Cefepime and Ginger's essential oil showed a strong synergistic effect on these bacteria. Keywords: Escherichia coli; ESBLs; Ginger Essential Oil; Cefepime; UTI

Antimicrobial treatment of monomicrobial phenotypic carbapenem-resistant Klebsiella pneumoniae bacteremia: Two are better than one

BACKGROUNDS

Infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) are emerging worldwide. The optimal treatment for CRKP infections is challenging for clinicians because therapeutic agents are greatly limited.

MATERIAL AND METHODS

A retrospective study of CRKP monomicrobial bacteremia was conducted at a medical center between 2010 and 2016. The use of at least one or more drugs with in vitro activity against the blood isolates was defined as appropriate combination therapy. The logistic regression model and propensity score analysis was used to assess clinical effects of therapeutic strategies. The 30-day crude mortality was the primary end point.

RESULTS

Two hundred and three patients were eligible and the 30-day mortality rate was 37.9% (77 patients). As compared with monotherapy, empirical (11.6 vs. 57.3%, p < .001) or definitive (26.5% vs. 48.6%, p = .001) combination antibiotic therapy showed a lower 30-day mortality rate independently. The propensity score analysis showed that those receiving combination therapy had less clinical (p ≤ .001) or microbiological failure (p = .003) and a lower 30-day mortality rate (p < .001). Among various regimens of definitive therapy, the 30-day mortality rate was the lowest among patients with appropriate combination therapy 23.6%, (p < .001; by log rank test). The primary outcome was similar in those with definitive carbapenem-containing and carbapenem-sparing combination regimens (p = .81). The presence or absence of carbapenemase production did not affect the mortality rate (p = .26).

CONCLUSION

Combination therapy, regardless of carbapenem-containing or carbapenem-sparing regimens, was associated with a favorable outcome.

The Potential of Antibiotics and Nanomaterial Combinations as Therapeutic Strategies in the Management of Multidrug-Resistant Infections: A Review

Antibiotic resistance has become a major public health concern around the world. This is exacerbated by the non-discovery of novel drugs, the development of resistance mechanisms in most of the clinical isolates of bacteria, as well as recurring infections, hindering disease treatment efficacy. In vitro data has shown that antibiotic combinations can be effective when microorganisms are resistant to individual drugs. Recently, advances in the direction of combination therapy for the treatment of multidrug-resistant (MDR) bacterial infections have embraced antibiotic combinations and the use of nanoparticles conjugated with antibiotics. Nanoparticles (NPs) can penetrate the cellular membrane of disease-causing organisms and obstruct essential molecular pathways, showing unique antibacterial mechanisms. Combined with the optimal drugs, NPs have established synergy and may assist in regulating the general threat of emergent bacterial resistance. This review comprises a general overview of antibiotic combinations strategies for the treatment of microbial infections. The potential of antibiotic combinations with NPs as new entrants in the antimicrobial therapy domain is discussed.

Update on the Management of Surgical Site Infections

Surgical site infections are an increasingly important issue in nosocomial infections. The progressive increase in antibiotic resistance, the ever-increasing number of interventions and the ever-increasing complexity of patients due to their comorbidities amplify this problem. In this perspective, it is necessary to consider all the risk factors and all the current preventive and prophylactic measures which are available. At the same time, given multiresistant microorganisms, it is essential to consider all the possible current therapeutic interventions. Therefore, our review aims to evaluate all the current aspects regarding the management of surgical site infections.

Plasmid-Borne AFM Alleles in Pseudomonas aeruginosa Clinical Isolates from China

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a pathogen of global concern due to the fact that therapeutic drugs are limited. Metallo-β-lactamase (MBL)-producing P. aeruginosa has become a critical part of CRPA. Alcaligenes faecalis metallo-β-lactamase (AFM) is a newly identified subclass B1b MBL. In this study, 487 P. aeruginosa strains isolated from patients and the environment in an intensive care unit were screened for AFM alleles. Five AFM-producing strains were identified, including four AFM-2-producing strains (ST262) and one AFM-4-producing strain (ST671). AFM-2-producing strains were isolated from rectal and throat swabs, and AFM-4-producing strains were isolated from the water sink. The bla_AFM-2 carrying plasmids belonged to the IncP-2 type, while the bla_AFM-4 carrying plasmid pAR19438 was a pSTY-like megaplasmid. Plasmid pAR19438 was acquired bla_AFM-4 by the integration of the Tn1403-like transposon. All bla_AFM genes were embedded in an ISCR29-bla_AFM unit core module flanked by class 1 integrons. The core module of bla_AFM-2 was ISCR29-ΔgroL-bla_AFM-2-ble_MBL-ΔtrpF-ΔISCR, while the core module of bla_AFM-4 was ISCR29-ΔgroL-bla_AFM-2-ble_MBL-ΔtrpF-ISCR-msrB-msrA-yfcG-corA-ΔISCR. The flanking sequences of ISCR29-bla_AFM units also differed. The expression of AFM-2 and AFM-4 in DH5α and PAO1 illustrated the same effect for the evaluation of the MICs of β-lactams, except for aztreonam. Identification of AFM-4 underscores that the quick spread and emerging development of mutants of MBLs require continuous surveillance in P. aeruginosa. IMPORTANCE Acquiring metallo-β-lactamase genes is one of the important carbapenem resistance mechanisms of P. aeruginosa. Alcaligenes faecalis metallo-β-lactamase is a newly identified metallo-β-lactamase, the prevalence and genetic context of which need to be explored. In this study, we identified AFM-producing P. aeruginosa strains among clinical isolates and found a new mutant of AFM, AFM-4. The bla_AFM-4 carrying plasmid pAR19438 was a pSTY-like megaplasmid, unlike the plasmids encoding other bla_AFM alleles. The genetic context of bla_AFM-4 was also different. However, AFM-2 and AFM-4 had the same impacts on antibiotic susceptibility. The presence and transmission of AFM alleles in P. aeruginosa pose a challenge to clinical practice.

Meropenem/Vaborbactam and Cefiderocol as Combination or Monotherapy to Treat Multi-Drug Resistant Gram-Negative Infections: A Regional Cross-Sectional Survey from Piedmont Infectious Disease Unit Network (PIDUN)

Meropenem/vaborbactam (MV) and cefiderocol were recently approved by the Food and Drug Administration and European Medicines Agency and are among the most promising antibacterial in treatment regimens against multi-drug resistant (MDR) gram-negative bacilli. A survey with close-ended questions was proposed to infectious disease (ID) and intensive care unit (ICU) physicians of Piedmont and Valle d'Aosta Region's hospitals. The aim was to collect data about habits and prescriptions of cefiderocol and MV. Twenty-three physicians (11 ID specialists and 12 anesthesiologists) in 13 Italian hospitals took part in the survey. Both cefiderocol and MV were mostly used as target therapy after a previous treatment failure and after ID specialist consult. The most frequent MDR pathogen in hospitals was Klebsiella pneumoniae carbapenemase-producing bacteria (KPC), followed by P. aeruginosa and A. baumannii. MDRs were more frequently isolated in ICU. In conclusion, cefiderocol was used in empiric regimens when A.baumannii was suspected, while MV was more used in suspect of KPC. MV and cefiderocol can be the first option in empiric treatment for critically ill patients in settings with high risk of MDR. The treatment should then be followed by rapid de-escalation when microbiological results are available.

In vitro susceptibilities of isolates of potentially naturally inducible chromosomal AmpC-producing metallo-β-lactamase-negative carbapenem-resistant Enterobacterales species to ceftazidime-avibactam: Data from the Antimicrobial Testing Leadership and Surveillance Programme, 2012-2019

In total, 74,570 potentially naturally inducible chromosomal AmpC-producing (PNIC-AmpC) Enterobacterales isolates included in the Antimicrobial Testing Leadership and Surveillance Programme were obtained worldwide from 2012 to 2019 (22,503 from 2012 to 2014 and 52,067 from 2015 to 2019). One hundred seventeen and 711 isolates obtained in 2012-2014 and 2015-2019, respectively, were carbapenem-resistant Enterobacterales (PNIC-AmpC-CRE). The minimum inhibitory concentrations of ceftazidime-avibactam for these isolates against were determined using the broth microdilution method. Genes encoding different Ambler classes of β-lactamases were investigated using multiplex PCR. After 97 isolates harboring genes encoding metallo-β-lactamases (MβL) were excluded, 731 PNIC-AmpC MβL-negative CRE isolates (101 from 2012 to 2014 and 630 from 2015 to 2019) were included in this study. Enterobacter cloacae complex species, Escherichia coli, and Citrobacter freundii complex species accounted for 36.3% (n = 265), 30.4% (n = 222), and 11.8% (n = 86), respectively, followed by Providencia species (n = 72), Serratia species (n = 52), and Klebsiella aerogenes (n = 34). The resistance rates to ceftazidime-avibactam for the overall PNIC-AmpC MβL-negative CRE isolates differed markedly between the two periods (35.6% vs. 63.3%, P < 0.001). Similar trends were observed for the MβL-negative-CR-E. cloacae complex species (47.4% vs. 65.2%; P = 0.046) and MβL-negative-CR-E. coli (16.2% vs. 63.8%; P < 0.001) but not for MβL-negative-CR-C. freundii complex species (40% vs. 62%; P = 0.153). Amongst the PNIC-AmpC MβL-negative CRE isolates, resistance rates to ceftazidime-avibactam worsened. Caution should be taken when empirically prescribing ceftazidime-avibactam for infections caused by PNIC-AmpC-CRE before susceptibility data are available.

Global Threat of Carbapenem-Resistant Gram-Negative Bacteria

Infections caused by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria (GNB), including carbapenem-resistant (CR) Enterobacterales (CRE; harboring mainly bla_KPC, bla_NDM, and bla_OXA-48-like genes), CR- or MDR/XDR-Pseudomonas aeruginosa (production of VIM, IMP, or NDM carbapenemases combined with porin alteration), and Acinetobacter baumannii complex (producing mainly OXA-23, OXA-58-like carbapenemases), have gradually worsened and become a major challenge to public health because of limited antibiotic choice and high case-fatality rates. Diverse MDR/XDR-GNB isolates have been predominantly cultured from inpatients and hospital equipment/settings, but CRE has also been identified in community settings and long-term care facilities. Several CRE outbreaks cost hospitals and healthcare institutions huge economic burdens for disinfection and containment of their disseminations. Parenteral polymyxin B/E has been observed to have a poor pharmacokinetic profile for the treatment of CR- and XDR-GNB. It has been determined that tigecycline is suitable for the treatment of bloodstream infections owing to GNB, with a minimum inhibitory concentration of ≤ 0.5 mg/L. Ceftazidime-avibactam is a last-resort antibiotic against GNB of Ambler class A/C/D enzyme-producers and a majority of CR-P. aeruginosa isolates. Furthermore, ceftolozane-tazobactam is shown to exhibit excellent in vitro activity against CR- and XDR-P. aeruginosa isolates. Several pharmaceuticals have devoted to exploring novel antibiotics to combat these troublesome XDR-GNBs. Nevertheless, only few antibiotics are shown to be effective in vitro against CR/XDR-A. baumannii complex isolates. In this era of antibiotic pipelines, strict implementation of antibiotic stewardship is as important as in-time isolation cohorts in limiting the spread of CR/XDR-GNB and alleviating the worsening trends of resistance.

Human Serum Proteins and Susceptibility of Acinetobacter baumannii to Cefiderocol: Role of Iron Transport

Cefiderocol, a recently introduced antibiotic, has a chemical structure that includes a cephalosporin that targets cell wall synthesis and a chlorocatechol siderophore moiety that facilitates cell penetration by active iron transporters. Analysis of the effect that human serum, human serum albumin, and human pleural fluid had on growing Acinetobacter baumannii showed that genes related to iron uptake were down-regulated. At the same time, β-lactamase genes were expressed at higher levels. The minimum inhibitory concentrations of this antimicrobial in A. baumannii cells growing in the presence of human serum, human serum albumin, or human pleural fluid were higher than those measured when these fluids were absent from the culture medium. These results correlate with increased expression levels of β-lactamase genes and the down-regulation of iron uptake-related genes in cultures containing human serum, human serum albumin, or human pleural fluid. These modifications in gene expression could explain the less-than-ideal clinical response observed in patients with pulmonary or bloodstream A. baumannii infections. The exposure of the infecting cells to the host's fluids could cause reduced cefiderocol transport capabilities and increased resistance to β-lactams. The regulation of genes that could impact the A. baumannii susceptibility to cefiderocol, or other antibacterials, is an understudied phenomenon that merits further investigation.

Ceftazidime/Avibactam and Other Commonly Used Antibiotics Activity Against Enterobacterales and Pseudomonas aeruginosa Isolated in Poland in 2015–2019

Purpose

Infections caused by resistant Gram-negative bacteria are becoming increasingly common and now pose a serious public health threat worldwide, because they are difficult to treat due to few treatment options and they are associated with high morbidity and mortality. The combination of ceftazidime with the beta-lactamase inhibitor avibactam – seems to be the right choice in this situation. The aim of the study was to evaluate the activity of ceftazidime/avibactam and other commonly used antibiotics against Enterobacterales and Pseudomonas aeruginosa strains isolated within last years in Poland.

Patients and Methods

This study analyzed the antibiotic susceptibility of 1607 Enterobacterales isolates and 543 nonfermenting P. aeruginosa strains collected between 2015 and 2019 in 4 medical laboratories participating in the ATLAS (Antimicrobial Testing Leadership And Surveillance) program in Poland. Unduplicated clinically significant Enterobacterales and P. aeruginosa strains were collected from patients with respiratory, skin and musculoskeletal, genitourinary, abdominal, bloodstream or other infections (ear, eye).

Results

The ceftazidime/avibactam combination demonstrates the highest activity against Enterobacterales (98.9%), in both adults and children, including strains presenting MDR (multidrug-resistant) (97.5%) and ESBL (extended spectrum β-lactamase) (96.3%) phenotypes. The activity of ceftazidime/avibactam increased to 100% when only MBL (metallo-β-lactamase)-negative subset of Enterobacterales was considered. This combination also achieved the second highest activity result (89.3%) after colistin in P. aeruginosa, including isolates of MDR (65.9%) and carbapenem-resistant (CR) phenotypes (54.8%). When MBL-positive isolates were excluded, susceptibility rate of P. aeruginosa increased to 94.7%. It is worth to note that susceptibility of the examined P. aeruginosa strains to ceftazidime/avibactam was very high in children (93.3%), especially in a pediatric intensive care unit (94.2%).

Conclusion

Enterobacterales and P. aeruginosa included in this analysis presented high susceptibility rates to ceftazidime/avibactam. Ceftazidime/avibactam showed the highest activity against Enterobacterales strains among all antibiotics studied, both for the total population as well as for MDR phenotype and ESBL phenotype. Ceftazidime/avibactam also achieved the second highest activity result against P. aeruginosa strains (including MDR and CR phenotypes). These results are much higher when excluding MBL-positive isolates that exhibit intrinsic resistance to ceftazidime/avibactam.

Nitroxoline and its derivatives are potent inhibitors of metallo-β-lactamases

Carbapenemases such as metallo-β-lactamases (MBLs) are spreading among Gram-negative bacterial pathogens. Infections due to these multidrug-resistant bacteria constitute a major global health challenge. Therapeutic strategies against carbapenemase producing bacteria include β-lactamase inhibitor combinations. Nitroxoline is a broad-spectrum antibiotic with restricted indication for urinary tract infections. In this study, we report on nitroxoline as an inhibitor of MBLs. We investigate the structure-activity relationships of nitroxoline derivatives considering in vitro MBL inhibitory potency in a fluorescence based assay using purified recombinant MBLs, NDM-1 and VIM-1. We investigated the most potent nitroxoline derivative in combination with imipenem against clinical isolates as well as transformants producing MBL by broth microdilution and time-kill kinetics. Our findings demonstrate that nitroxoline derivatives are potent MBL inhibitors and in combination with imipenem overcome MBL-mediated carbapenem resistance.

Development and Research Progress of Anti-Drug Resistant Bacteria Drugs

Bacterial resistance has become increasingly serious because of the widespread use and abuse of antibiotics. In particular, the emergence of multidrug-resistant bacteria has posed a serious threat to human public health and attracted the attention of the World Health Organization (WHO) and the governments of various countries. Therefore, the establishment of measures against bacterial resistance and the discovery of new antibacterial drugs are increasingly urgent to better contain the emergence of bacterial resistance and provide a reference for the development of new antibacterial drugs. In this review, we discuss some antibiotic drugs that have been approved for clinical use and a partial summary of the meaningful research results of anti-drug resistant bacterial drugs in different fields, including the antibiotic drugs approved by the FDA from 2015 to 2020, the potential drugs against drug-resistant bacteria, the new molecules synthesized by chemical modification, combination therapy, drug repurposing, immunotherapy and other therapies.

Multicenter surveillance of in vitro activities of cefepime-zidebactam, cefepime-enmetazobactam, omadacycline, eravacycline, and comparator antibiotics against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex causing bloodstream infection in Taiwan, 2020

OBJECTIVES

: To determine the in vitro activities of novel and comparator antibiotics against gram-negative bacteria (GNB) in Taiwan.

METHODS

: Isolates of Escherichia coli (n = 335), Klebsiella pneumoniae (n = 316; 144 isolates with hyperviscosity characteristics), Pseudomonas aeruginosa (n = 271), Acinetobacter baumannii complex species (n = 187), and non-typhoidal Salmonella species (n = 226), Shigella species (n = 13) from miscellaneous culture sources were collected in 2020 in Taiwan. The MICs of the isolates to test antibiotics were determined using the broth microdilution method. GeneXpert was used to detect genes encoding carbapenemases among the carbapenem-non-susceptible (NS) Enterobacterales isolates.

RESULTS

: The MIC values of the cefepime-enmetazobactam combination against extended-spectrum β-lactamase-producing E. coli and K. pneumoniae isolates (MIC₉₀ ≤ 0.5 mg/L), bla_KPC-harboring E. coli isolates (0.25 mg/L; n = 2), and 80% of bla_OXA-48-like gene-harboring K. pneumoniae isolates (≤2 mg/L) were low. The MIC ranges of the cefepime-zidebactam against carbapenemase-producing Enterobacterales isolates (irrespective of the carbapenemase type [MIC₉₀ ≤ 4 mg/L]) and carbapenem-NS or ceftolozane-tazobactam-NS P. aeruginosa isolates (MIC₉₀ value, 8 mg/L) were significantly lower than those of the cefepime-enmetazobactam.

CONCLUSIONS

: The efficacy of novel antibiotics against important drug-resistant GNB must be monitored and validated during the clinical treatment of patients.

β-Glucan Induces Distinct and Protective Innate Immune Memory in Differentiated Macrophages

Bacterial infections are a common and deadly threat to vulnerable patients. Alternative strategies to fight infection are needed. β-Glucan, an immunomodulator derived from the fungal cell wall, provokes resistance to infection by inducing trained immunity, a phenomenon that persists for weeks to months. Given the durability of trained immunity, it is unclear which leukocyte populations sustain this effect. Macrophages have a life span that surpasses the duration of trained immunity. Thus, we sought to define the contribution of differentiated macrophages to trained immunity. Our results show that β-glucan protects mice from Pseudomonas aeruginosa infection by augmenting recruitment of innate leukocytes to the site of infection and facilitating local clearance of bacteria, an effect that persists for more than 7 d. Adoptive transfer of macrophages, trained using β-glucan, into naive mice conferred a comparable level of protection. Trained mouse bone marrow-derived macrophages assumed an antimicrobial phenotype characterized by enhanced phagocytosis and reactive oxygen species production in parallel with sustained enhancements in glycolytic and oxidative metabolism, increased mitochondrial mass, and membrane potential. β-Glucan induced broad transcriptomic changes in macrophages consistent with early activation of the inflammatory response, followed by sustained alterations in transcripts associated with metabolism, cellular differentiation, and antimicrobial function. Trained macrophages constitutively secreted CCL chemokines and robustly produced proinflammatory cytokines and chemokines in response to LPS challenge. Induction of the trained phenotype was independent of the classic β-glucan receptors Dectin-1 and TLR-2. These findings provide evidence that β-glucan induces enhanced protection from infection by driving trained immunity in macrophages.

Current and future perspectives in the treatment of multidrug-resistant Gram-negative infections

Microbial resistance is a serious threat to human health worldwide. Among the World Health Organisation's list of priority resistant bacteria, three are listed as critical-the highest level of concern-and all three are Gram-negative. Gram-negative resistance has spread worldwide via a variety of mechanisms, the most problematic being via AmpC enzymes, extended-spectrum β-lactamases, and carbapenemases. A combination of older drugs, many with high levels of toxicity, and newer agents are being used to combat multidrug resistance, with varying degrees of success. This review discusses the current treatments for multidrug-resistant Gram-negative bacteria, including new agents, older compounds, and new combinations of both, and some new treatment targets that are currently under investigation.

Bacterial infections in lung transplantation

Lung transplantation has lower survival rates compared to other than other solid organ transplants (SOT) due to higher rates of infection and rejection-related complications, and bacterial infections (BI) are the most frequent infectious complications. Excess morbidity and mortality are not only a direct consequence of these BI, but so are subsequent loss of allograft tolerance, rejection, and chronic lung allograft dysfunction due to bronchiolitis obliterans syndrome (BOS). A wide variety of pathogens can cause infections in lung transplant recipients (LTRs), including a number of nosocomial pathogens and other multidrug-resistant (MDR) pathogens. Although pneumonia and intrathoracic infections predominate, LTRs are at risk of a number of types of infections. Risk factors include altered anatomy and function of airways, impaired immunity, the microbial flora of the donor and recipient, underlying medical conditions, and genetic factors. Further work on immune monitoring has the potential to improve outcomes. The infecting agents can be derived from the donor lung, pre-existing recipient flora, or acquired from the environment over time. Certain infections may preclude lung transplantation, but this varies from center to center, and more recent studies suggest fewer patients should be disqualified. New molecular methods allow microbiome studies of the lung, gut, and other sites that may further our knowledge of how airway colonization can result in infection and allograft loss. Surveillance, early diagnosis, and aggressive antimicrobial therapy of BI is critical in LTRs. Antibiotic resistance is a major barrier to successful management of these infections. The availability of new agents for MDR Gram-negatives may improve outcomes. Other new therapies, such as bacteriophage therapy, show promise for the future. Finally, it is important to prevent infections through peri-transplant prophylaxis, vaccination, and infection control measures.

The Next-Generation β-Lactamase Inhibitor Taniborbactam Restores the Morphological Effects of Cefepime in KPC-Producing Escherichia coli

Gram-negative bacteria producing carbapenemases are resistant to a variety of β-lactam antibiotics and pose a significant health risk. Given the dearth of new antibiotics, combinations of new broad-spectrum β-lactamase inhibitors (BLIs) with approved β-lactams have provided treatment options for resistant bacterial infections. Taniborbactam (formerly VNRX-5133) is an investigational BLI that is effective against both serine- and metallo-β-lactamases, including the serine carbapenemase KPC. In the current study, we assessed the effectiveness of taniborbactam to restore antibacterial activity of cefepime against KPC-3-producing Escherichia coli by inhibiting the KPC-3-dependent hydrolysis of cefepime. Time-lapse microscopy revealed that cells treated with greater than 1× MIC of cefepime (128 μg/ml) and cefepime-taniborbactam (4 μg/ml cefepime and 4 μg/ml taniborbactam) exhibited significant elongation, whereas cells treated with taniborbactam alone did not owing to a lack of standalone antibacterial activity of the BLI. The elongated cells also had frequent cellular voids thought to be formed by attempted cell divisions and pinching of the cytoplasmic membrane. Additionally, the effect of taniborbactam continued even after its removal from the growth medium. Pretreatment with 4 μg/ml taniborbactam helped to restore the antibacterial action of cefepime by neutralizing the effect of the KPC-3 β-lactamase. IMPORTANCE β-lactam (BL) antibiotics are the most prescribed antimicrobial class. The efficacy of β-lactams is threatened by the production of β-lactamase enzymes, the predominant resistance mechanism impacting these agents in Gram-negative bacterial pathogens. This study visualizes the effects of a combination treatment of taniborbactam, a broad spectrum β-lactamase inhibitor (BLI), and the BL antibiotic cefepime on a carbapenemase-producing E. coli strain. While this treatment has been described in the context of other cephalosporin-resistant bacteria, this is the first description of a microscopic evaluation of a KPC-3-producing strain of E. coli challenged by this BL-BLI combination. Live-cell microscopy analysis of cells treated with taniborbactam and cefepime demonstrated the antimicrobial effects on cellular morphology and highlighted the long-lasting inhibition of β-lactamases by taniborbactam even after it was removed from the medium. This research speaks to the importance of taniborbactam in fighting BL-mediated antibiotic resistance.

Cefiderocol: A Review in Serious Gram-Negative Bacterial Infections

Intravenous cefiderocol (Fetroja®; Fetcroja®) is the first siderophore cephalosporin approved for the treatment of adults with serious Gram-negative bacterial infections. Cefiderocol is stable against all four Ambler classes of β-lactamases (including metallo-β-lactamases) and exhibits excellent in vitro activity against many clinically relevant Gram-negative pathogens, including multidrug resistant strains. In randomized, double-blind clinical trials, cefiderocol was noninferior to imipenem/cilastatin for the treatment of complicated urinary tract infections (cUTI) and to meropenem for nosocomial pneumonia. Furthermore, in a pathogen-focused clinical trial in patients with carbapenem-resistant (CR) infections, cefiderocol showed comparable efficacy to best available therapy (BAT), albeit all-cause mortality rate was higher in the cefiderocol arm, the cause of which has not been established. Cefiderocol had a good tolerability and safety profile in clinical trials. Thus cefiderocol is a novel, emerging, useful addition to the current treatment options for adults with susceptible Gram-negative bacterial infections (including cUTI and nosocomial pneumonia) for whom there are limited treatment options.

Old and New Beta-Lactamase Inhibitors: Molecular Structure, Mechanism of Action, and Clinical Use

The β-lactams have a central place in the antibacterial armamentarium, but the increasing resistance to these drugs, especially among Gram-negative bacteria, is becoming one of the major threats to public health worldwide. Treatment options are limited, and only a small number of novel antibiotics are in development. However, one of the responses to this threat is the combination of β-lactam antibiotics with β-lactamase inhibitors, which are successfully used in the clinic for overcoming resistance by inhibiting β-lactamases. The existing inhibitors inactivate most of class A and C serine β-lactamases, but several of class D and B (metallo-β-lactamase) are resistant. The present review provides the status and knowledge concerning current β-lactamase inhibitors and an update on research efforts to identify and develop new and more efficient β-lactamase inhibitors.

Antibiotic-Resistant Infections and Treatment Challenges in the Immunocompromised Host: An Update

This article reviews antibiotic resistance and treatment of bacterial infections in the growing number of patients who are immunocompromised: solid organ transplant recipients, the neutropenic host, and persons with human immunodeficiency virus and AIDS. Specific mechanisms of resistance in both gram-negative and gram-positive bacteria, as well as newer treatment options are addressed elsewhere and are only briefly discussed in the context of the immunocompromised host.

Cost-effectiveness of ceftazidime/avibactam for infections due to carbapenem-resistant bacteria in Peru

Objectives

The objective of this study was to analyse the cost-effectiveness (C-E) of ceftazidime/avibactam (CAZ/AVI)-based therapy versus colistin (COL)-based therapy for pneumonia and bacteraemia caused by carbapenem-resistant enterobacteria (CRE) adjusted to Peruvian context.

Methods

A Markov decision model was extrapolated from literature to evaluate the clinical and economic consequences of CAZ/AVI-based therapy compared to COL-based therapy for a hypothetical cohort of patients with CRE pneumonia or bacteraemia according to Peruvian context. It was adopted a 5-year time horizon and a Markov-cycle length of 1 year. All patients in the model were assigned to CRE pneumonia or bacteraemia state and may transit through four different health states: home-care, long-term care without dialysis, long-term care with dialysis or death.

Key findings

Intervention with CAZ/AVI becomes progressively more cost-effective from a threshold of S/ 24,000 or US$ 6666 (equivalent to 1 Gross Domestic Product-per cápita [GDP-pc]). The model simulation allowed to calculate an average total cost of S/ 2’971,582 (US$ 825,440) for CAZ/AVI against S/2’056,488 (US$ 571.247) for COL treatment, yielding an incremental cost of S/ 915,094 (US$ 254,193). The cost/QALY for CAZ/AVI treatment against COL therapy approaches to S/23,154 (US$ 6432), something less than 1 annual GDP-pc. There were additional benefits associated with CAZ/AVI in the 5-year horizon, such as: 21 deaths avoided, 86 hospital days avoided, 1 CRF5 avoided and a NMB of S/6649 (US$ 1847).

Conclusions

The present transferability model demonstrates the C-E of CAZ/AVI over COL for the treatment of bacteraemia and CRE pneumonia according to peruvian payment thresholds.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Impact of an Evidence-Based Antibiotic Protocol on Common Gram-Negative Bacteria's Antibiotic Resistance in a Cardiac Surgical Intensive Care Unit

Background Based on the analysis of infections and antibiotic usage in the years 2013 and 2014, an evidence-based antibiotic protocol was developed and implemented in our cardiac surgical intensive care unit (CSICU). This study intends to study the impact of this new protocol on the sensitivity profiles of common gram-negative bacteria in our CSICU.

Methods The medical records of patients who underwent cardiac surgery at our center, between January 2017 and December 2018, were reviewed and the incidence of different hospital-acquired bacteria and their antibiotic sensitivity profiles were recorded. The antibiotic-sensitivity profiles of common gram-negative bacteria, for the years 2017 and 2018, were compared with the published data of 2013 and 2014 from our department.

Results There was a significant decrease in the incidence of Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa resistant to carbapenems during 2017 and 2018. The incidence of colistin-resistant A. baumannii and P. aeruginosa also decreased significantly in 2017 and 2018. A significant increase in the proportion of amikacin resistant A. baumannii and E. coli and A. baumannii resistant to B lactam/B lactamase inhibitors also occurred.

Conclusion Antibiotic stewardship can reverse the antibiotic resistance of common gram-negative bacteria in the ICU.

Antibiotic Resistant Bloodstream Infections in Pediatric Patients Receiving Chemotherapy or Hematopoietic Stem Cell Transplant: Factors Associated with Development of Resistance, Intensive Care Admission and Mortality

Bloodstream infections (BSI) are a severe complication of antineoplastic chemotherapy or hematopoietic stem cell transplantation (HSCT), especially in the presence of antibiotic resistance (AR). A multinational, multicenter retrospective study in patients aged ≤ 18 years, treated with chemotherapy or HSCT from 2015 to 2017 was implemented to analyze AR among non-common skin commensals BSI. Risk factors associated with AR, intensive care unit (ICU) admission and mortality were analyzed by multilevel mixed effects or standard logistic regressions. A total of 1291 BSIs with 1379 strains were reported in 1031 patients. Among Gram-negatives more than 20% were resistant to ceftazidime, cefepime, piperacillin-tazobactam and ciprofloxacin while 9% was resistant to meropenem. Methicillin-resistance was observed in 17% of S. aureus and vancomycin resistance in 40% of E. faecium. Previous exposure to antibiotics, especially to carbapenems, was significantly associated with resistant Gram-negative BSI while previous colonization with methicillin-resistant S. aureus was associated with BSI due to this pathogen. Hematological malignancies, neutropenia and Gram-negatives resistant to >3 antibiotics were significantly associated with higher risk of ICU admission. Underlying disease in relapse/progression, previous exposure to antibiotics, and need of ICU admission were significantly associated with mortality. Center-level variation showed a greater impact on AR, while patient-level variation had more effect on ICU admission and mortality. Previous exposure to antibiotics or colonization by resistant pathogens can be the cause of AR BSI. Resistant Gram-negatives are significantly associated with ICU admission and mortality, with a significant role for the treating center too. The significant evidence of center-level variations on AR, ICU admission and mortality, stress the need for careful local antibiotic stewardship and infection control programs.

In Vitro Activity of Cefepime-Zidebactam, Ceftazidime-Avibactam, and Other Comparators against Clinical Isolates of Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii: Results from China Antimicrobial Surveillance Network (CHINET) in 2018

This study evaluated the in vitro activity of cefepime-zidebactam in comparison with that of ceftazidime-avibactam and other comparators against clinically significant Gram-negative bacillus isolates. A total of 3,400 nonduplicate Gram-negative clinical isolates were collected from 45 medical centers across China in the CHINET Program in 2018, including Enterobacterales (n = 2,228), Pseudomonas aeruginosa (n = 657), and Acinetobacter baumannii (n = 515). The activities of cefepime-zidebactam and 20 comparators were determined by broth microdilution as recommended by the Clinical and Laboratory Standards Institute. Cefepime-zidebactam demonstrated potent activity against almost all Enterobacterales (MIC_50/90, 0.125/1 mg/liter) and good activity against P. aeruginosa (MIC_50/90, 2/8 mg/liter). Among the 373 carbapenem-resistant Enterobacteriaceae isolates, 57.3% (213/373) and 15.3% (57/373) were positive for bla _KPC-2 and bla _NDM, respectively. Cefepime-zidebactam showed a MIC of ≤2 mg/liter for 92.0% (196/213) of bla _KPC-2 producers and 79.7% (47/59) of bla _NDM producers. Ceftazidime-avibactam showed good in vitro activity against Enterobacterales (MIC_50/90, 0.25/2 mg/liter; 94.0% susceptible) and P. aeruginosa (MIC_50/90, 4/16 mg/liter; 86.9% susceptible). Ceftazidime-avibactam was active against 9.1% of carbapenem-resistant Escherichia coli isolates (63.6% were bla _NDM producers) and 84.6% of Klebsiella pneumoniae isolates (74.3% were bla _KPC producers). Most (90.1%) bla _KPC-2 producers were susceptible to ceftazidime-avibactam. Cefepime-zidebactam demonstrated limited activity (MIC_50/90, 16/32 mg/liter) against the 515 A. baumannii isolates (79.2% were carbapenem resistant), and ceftazidime-avibactam was less active (MIC_50/90, 64/>64 mg/liter). Cefepime-zidebactam was highly active against clinical isolates of Enterobacterales and P. aeruginosa, including bla _KPC-2-positive Enterobacterales and bla _NDM-positive Enterobacterales and carbapenem-resistant P. aeruginosa And ceftazidime-avibactam was highly active against bla _KPC-2-positive Enterobacterales and carbapenem-resistant P. aeruginosa.

ANT2681: SAR Studies Leading to the Identification of a Metallo-β-lactamase Inhibitor with Potential for Clinical Use in Combination with Meropenem for the Treatment of Infections Caused by NDM-Producing Enterobacteriaceae

The clinical effectiveness of the important β-lactam class of antibiotics is under threat by the emergence of resistance, mostly due to the production of acquired serine- (SBL) and metallo-β-lactamase (MBL) enzymes. To address this resistance issue, multiple β-lactam/β-lactamase inhibitor combinations have been successfully introduced into the clinic over the past several decades. However, all of those combinations contain SBL inhibitors and, as yet, there are no MBL inhibitors in clinical use. Consequently, there exists an unaddressed yet growing healthcare problem due to the rise in recent years of highly resistant strains which produce New Delhi metallo (NDM)-type metallo-carbapenemases. Previously, we reported the characterization of an advanced MBL inhibitor lead compound, ANT431. Herein, we discuss the completion of a lead optimization campaign culminating in the discovery of the preclinical candidate ANT2681, a potent NDM inhibitor with strong potential for clinical development.

Naturally-Occurring Alkaloids of Plant Origin as Potential Antimicrobials against Antibiotic-Resistant Infections

Antibiotic resistance is now considered a worldwide problem that puts public health at risk. The onset of bacterial strains resistant to conventional antibiotics and the scarcity of new drugs have prompted scientific research to re-evaluate natural products as molecules with high biological and chemical potential. A class of natural compounds of significant importance is represented by alkaloids derived from higher plants. In this review, we have collected data obtained from various research groups on the antimicrobial activities of these alkaloids against conventional antibiotic-resistant strains. In addition, the structure–function relationship was described and commented on, highlighting the high potential of alkaloids as antimicrobials.

Novel β-Lactam/β-Lactamase inhibitor combinations vs alternative antibiotics in the treatment of complicated urinary tract infections: A meta-analysis of randomized controlled trials

OBJECTIVES

This meta-analysis assessed the efficacy and safety of novel β-lactam/β-lactamase inhibitor combinations in the treatment of complicated urinary tract infection (cUTI)/acute pyelonephritis (APN).

METHODS

PubMed, Web of Science, EBSCO (Elton B. Stephens Co.), Cochrane Library, Ovid MEDLINE, and Embase databases were accessed until November 21, 2019. In this meta-analysis, only randomized controlled trials comparing the treatment efficacy of novel β-lactam/β-lactamase inhibitor combinations with other antibiotics for cUTI/APN in adult patients were included. The outcomes included the clinical and microbiological responses, and risk of adverse events (AEs).

RESULTS

Overall, the experimental group treated with a novel β-lactam/β-lactamase inhibitor combination and the control group comprised 1346 and 1376 patients, respectively. No significant difference in the clinical response rate at test-of-cure was observed between the novel β-lactam/β-lactamase inhibitor combination and comparators among the microbiological modified intent-to-treat population (89.1% vs 88.3%, OR, 1.04; 95% confidence interval [CI], 0.76-1.42; I = 28%) and the microbiologically evaluable population (95.2% vs 94.7%, OR, 1.12; 95% CI, 0.68-1.84; I = 0%). Additionally, the novel β-lactam/β-lactamase inhibitor combination was associated with a better microbiological response at test-of-cure than the comparators among the microbiological modified intent-to-treat population (74.4% vs 68.5%, OR, 1.34; 95% CI, 1.04-1.72; I = 45%) and microbiologically evaluable population (80.1% vs 72.5%, OR, 1.49; 95% CI, 1.06-2.10; I = 58%). Finally, the risk of AEs associated with the novel β-lactam/β-lactamase inhibitor combination was similar to that associated with the comparators (treatment-emergent adverse events [TEAE], OR, 1.04; 95% CI, 0.87-1.23; I = 19%; serious AEs, OR, 1.21; 95% CI, 0.82-1.76; I = 0%; treatment discontinuation for drug-related TEAE, OR, 077; 95% CI, 0.38-1.56, I = 5%). The all-cause mortality did not differ between the novel β-lactam/β-lactamase inhibitor combination and comparators (OR, 1.19; 95% CI, 0.37-3.81; I = 0%).

CONCLUSIONS

The clinical and microbiological responses of novel β-lactam/β-lactamase inhibitor combinations in the treatment of cUTI/APN are similar to those of other available antibiotics. These combinations also share a safety profile similar to that of other antibiotics.