Cefepime: a reappraisal in an era of increasing antimicrobial resistance

Towards optimizing cefepime/tazobactam (WCK 4282) exposure to achieve efficacy against piperacillin/tazobactam-resistant ESBL infections: dose recommendations for various renal functions, including intermittent haemodialysis, in healthy individuals

OBJECTIVES

WCK 4282 is a novel combination of cefepime 2 g and tazobactam 2 g being developed for the treatment of infections caused by piperacillin/tazobactam-resistant ESBL infections. The dosing regimen for cefepime/tazobactam needs to be optimized to generate adequate exposures to treat infections caused by ESBL-producing pathogens resistant to both cefepime and piperacillin/tazobactam.

METHODS

We developed pharmacokinetic population models of cefepime and tazobactam to evaluate the optimal dose adjustments in patients, including those with augmented renal clearance as well as various degrees of renal impairment, and also for those on intermittent haemodialysis. Optimal doses for various degrees of renal function were identified by determining the PTA for a range of MICs. To cover ESBL-producing pathogens with an cefepime/tazobactam MIC of 16 mg/L, a dosing regimen of 2 g q8h infused over 1.5 h resulted in a combined PTA of 99% for the mean murine 1 log10-kill target for the cefepime/tazobactam combination.

RESULTS

We found that to adjust for renal function, doses need to be reduced to 1 g q8h, 500 mg q8h and 500 mg q12h for patients with CLCR of 30-59, 15-29 and 8-14 mL/min (as well as patients with intermittent haemodialysis), respectively. In patients with high to augmented CLR (estimated CLCR 120-180 mL/min), a prolonged 4 h infusion of standard dose is required.

CONCLUSIONS

The suggested dosing regimens will result in exposures of cefepime and tazobactam that would be adequate for infections caused by ESBL-producing pathogens with a cefepime/tazobactam MICs up to 16 mg/L.

Cefepime distribution by microdialysis in peritoneal fluid of rats with or without experimental peritonitis

The aim of this study was to investigate the penetration of cefepime into rat peritoneal fluid by microdialysis and to determine the relationship between unbound drug plasma and tissue concentration in healthy animals and in a sepsis model established through cecal ligation and puncture-induced peritonitis. Probe recovery was performed by dialysis and retrodialysis. Cefepime was administered at a dose of 110 mg/kg intravenously. Samples were collected for about 4 h, and concentrations were determined by liquid chromatography-electrospray ionization-QTOF MS. Tissue penetration was also determined. Probe recovery in vivo was 38.78% ± 3.31% and 38.83% ± 2.74% in the control and peritonitis groups, respectively. Cefepime was rapidly distributed in the peritoneal fluid in both groups. The peritoneal fluid/plasma cefepime ratio was 0.38 and 0.32 for the control and peritonitis groups, respectively. Cefepime concentrations were above the MIC of 4 mg/L for the main enterobacteria. The infection model that was used had no apparent effect on the pharmacokinetics of cefepime in rats. This was the first study to determine free cefepime concentrations in the peritoneal fluid of healthy rats and rats with experimental peritonitis.

Cefepime-Associated Neurotoxicity in a Pediatric Patient With Stage V Chronic Kidney Disease

Background: Studies in adult patients suggest cefepime can cause neurotoxicity, including disorientation, seizures, and coma, particularly when present at high concentrations. Patients with underlying kidney dysfunction or central nervous system anomalies are at particularly high risk. There is a relative paucity of pediatric literature on the neurotoxic effects of cefepime. Case Report: Herein is reported the case of a 2-year-old patient with chronic kidney disease receiving cefepime for Serratia marcescens bacteremia who experienced agitation, tremor, and inconsolability in the setting of an elevated cefepime trough that improved with cefepime discontinuation alone. Conclusions: Pediatric patients with acute and chronic kidney disease are at risk of cefepime-related neurologic changes. Therapeutic drug monitoring for cefepime in patients with kidney dysfunction or baseline neurologic abnormalities may help inform appropriate antimicrobial dosing and avoidance of toxicity.

Extended-Spectrum β-Lactamases (ESBL): Challenges and Opportunities

The rise of antimicrobial resistance, particularly from extended-spectrum β-lactamase producing Enterobacteriaceae (ESBL-E), poses a significant global health challenge as it frequently causes the failure of empirical antibiotic therapy, leading to morbidity and mortality. The E. coli- and K. pneumoniae-derived CTX-M genotype is one of the major types of ESBL. Mobile genetic elements (MGEs) are involved in spreading ESBL genes among the bacterial population. Due to the rapidly evolving nature of ESBL-E, there is a lack of specific standard examination methods. Carbapenem has been considered the drug of first choice against ESBL-E. However, carbapenem-sparing strategies and alternative treatment options are needed due to the emergence of carbapenem resistance. In South Asian countries, the irrational use of antibiotics might have played a significant role in aggravating the problem of ESBL-induced AMR. Superbugs showing resistance to last-resort antibiotics carbapenem and colistin have been reported in South Asian regions, indicating a future bleak picture if no urgent action is taken. To counteract the crisis, we need rapid diagnostic tools along with efficient treatment options. Detailed studies on ESBL and the implementation of the One Health approach including systematic surveillance across the public and animal health sectors are strongly recommended. This review provides an overview of the background, associated risk factors, transmission, and therapy of ESBL with a focus on the current situation and future threat in the developing countries of the South Asian region and beyond.

Understanding resistance acquisition by Pseudomonas aeruginosa and possible pharmacological approaches in palliating its pathogenesis

Pseudomonas aeruginosa can utilize various virulence factors necessary for host infection and persistence. These virulence factors include pyocyanin, proteases, exotoxins, 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), phospholipases, and siderophores that enable the bacteria to cause severe infections in immunocompromised individuals. P. aeruginosa falls into the category of nosocomial pathogens that are typically resistant to available antibiotics and therapeutic approaches. P. aeruginosa bio-film formation is a major concern in hospitals because it can cause chronic infection and increase the risk of mortality. Therefore, the development of new strategies to disrupt biofilm formation and improve antibiotic efficacy for the treatment of P. aeruginosa infections is crucial. Anti-biofilm and anti-quorum sensing (QS) activity can be viewed as an anti-virulence approach to control the infectious nature of P. aeruginosa. Inhibition of QS and biofilm formation can be achieved through pharmacological approaches such as phytochemicals and essential oils, which have shown promising results in laboratory studies. A regulatory protein called LasR plays a key role in QS signaling to coordinate gene expression. Designing an antagonist molecule that mimics the natural autoinducer might be the best approach for LasR inhibition. Here we reviewed the mechanism behind antibiotic resistance and alternative approaches to combat the pathogenicity of P. aeruginosa.

A physiologically based pharmacokinetic model of cefepime to predict its pharmacokinetics in healthy, pediatric and disease populations

The physiologically based pharmacokinetic modeling (PBPK) approach can predict drug pharmacokinetics (PK) by combining changes in blood flow and pathophysiological alterations for developing drug-disease models. Cefepime hydrochloride is a parenteral cephalosporin that is used to treat pneumonia, sepsis, and febrile neutropenia, among other things. The current study sought to identify the factors that impact cefepime pharmacokinetics (PK) following dosing in healthy, diseased (CKD and obese), and pediatric populations. For model construction and simulation, the modeling tool PK-SIM was utilized. Estimating cefepime PK following intravenous (IV) application in healthy subjects served as the primary step in the model-building procedure. The prediction of cefepime PK in chronic kidney disease (CKD) and obese populations were performed after the integration of the relevant pathophysiological changes. Visual predictive checks and a comparison of the observed and predicted values of the PK parameters were used to verify the developed model. The results of the PK parameters were consistent with the reported clinical data in healthy subjects. The developed PBPK model successfully predicted cefepime PK as observed from the ratio of the observed and predicted PK parameters as they were within a two-fold error range.

Optimization of Antimicrobial Stewardship Programs Using Therapeutic Drug Monitoring and Pharmacokinetics-Pharmacodynamics Protocols: A Cost-Benefit Review

PURPOSE

Antimicrobial stewardship programs are important for reducing antimicrobial resistance because they can readjust antibiotic prescriptions to local guidelines, switch intravenous to oral administration, and reduce hospitalization times. Pharmacokinetics-pharmacodynamics (PK-PD) empirically based prescriptions and therapeutic drug monitoring (TDM) programs are essential for antimicrobial stewardship, but there is a need to fit protocols according to cost benefits. The cost benefits can be demonstrated by reducing toxicity and hospital stay, decreasing the amount of drug used per day, and preventing relapses in infection. Our aim was to review the data available on whether PK-PD empirically based prescriptions and TDM could improve the cost benefits of an antimicrobial stewardship program to decrease global hospital expenditures.

METHODS

A narrative review based on PubMed search with the relevant studies of vancomycin, aminoglycosides, beta-lactams, and voriconazole.

RESULTS

TDM protocols demonstrated important cost benefit for patients treated with vancomycin, aminoglycosides, and voriconazole mainly due to reduce toxicities and decreasing the hospital length of stay. In addition, PK-PD strategies that used infusion modifications to meropenem, piperacillin-tazobactam, ceftazidime, and cefepime, such as extended or continuous infusion, demonstrated important cost benefits, mainly due to reducing daily drug needs and lengths of hospital stays.

CONCLUSIONS

TDM protocols and PK-PD empirically based prescriptions improve the cost-benefits and decrease the global hospital expenditures.

Evolution and Emergence of Antibiotic Resistance in Given Ecosystems: Possible Strategies for Addressing the Challenge of Antibiotic Resistance

Antibiotics were once considered the magic bullet for all human infections. However, their success was short-lived, and today, microorganisms have become resistant to almost all known antimicrobials. The most recent decade of the 20th and the beginning of the 21st century have witnessed the emergence and spread of antibiotic resistance (ABR) in different pathogenic microorganisms worldwide. Therefore, this narrative review examined the history of antibiotics and the ecological roles of antibiotics, and their resistance. The evolution of bacterial antibiotic resistance in different environments, including aquatic and terrestrial ecosystems, and modern tools used for the identification were addressed. Finally, the review addressed the ecotoxicological impact of antibiotic-resistant bacteria and public health concerns and concluded with possible strategies for addressing the ABR challenge. The information provided in this review will enhance our understanding of ABR and its implications for human, animal, and environmental health. Understanding the environmental dimension will also strengthen the need to prevent pollution as the factors influencing ABR in this setting are more than just antibiotics but involve others like heavy metals and biocides, usually not considered when studying ABR.

Dynamics of extended-spectrum cephalosporin resistance genes in Escherichia coli from Europe and North America

Extended-spectrum cephalosporins (ESCs) are critically important antimicrobial agents for human and veterinary medicine. ESC resistance (ESC-R) genes have spread worldwide through plasmids and clonal expansion, yet the distribution and dynamics of ESC-R genes in different ecological compartments are poorly understood. Here we use whole genome sequence data of Enterobacterales isolates of human and animal origin from Europe and North America and identify contrasting temporal dynamics. AmpC β-lactamases were initially more dominant in North America in humans and farm animals, only later emerging in Europe. In contrast, specific extended-spectrum β-lactamases (ESBLs) were initially common in animals from Europe and later emerged in North America. This study identifies differences in the relative importance of plasmids and clonal expansion across different compartments for the spread of different ESC-R genes. Understanding the mechanisms of transmission will be critical in the design of interventions to reduce the spread of antimicrobial resistance.

Effect of Cefepime/Enmetazobactam vs Piperacillin/Tazobactam on Clinical Cure and Microbiological Eradication in Patients With Complicated Urinary Tract Infection or Acute Pyelonephritis: A Randomized Clinical Trial

IMPORTANCE

Cefepime/enmetazobactam is a novel β-lactam/β-lactamase inhibitor combination and a potential empirical therapy for resistant gram-negative infections.

OBJECTIVE

To evaluate whether cefepime/enmetazobactam was noninferior to piperacillin/tazobactam for the primary outcome of treatment efficacy in patients with complicated urinary tract infections (UTIs) or acute pyelonephritis.

DESIGN, SETTING, AND PARTICIPANTS

A phase 3, randomized, double-blind, active-controlled, multicenter, noninferiority clinical trial conducted at 90 sites in Europe, North and Central America, South America, and South Africa. Recruitment occurred between September 24, 2018, and November 2, 2019. Final follow-up occurred November 26, 2019. Participants were adult patients aged 18 years or older with a clinical diagnosis of complicated UTI or acute pyelonephritis caused by gram-negative urinary pathogens.

INTERVENTIONS

Eligible patients were randomized to receive either cefepime, 2 g/enmetazobactam, 0.5 g (n = 520), or piperacillin, 4 g/tazobactam, 0.5 g (n = 521), by 2-hour infusion every 8 hours for 7 days (up to 14 days in patients with a positive blood culture at baseline).

MAIN OUTCOMES AND MEASURES

The primary outcome was the proportion of patients in the primary analysis set (patients who received any amount of study drug with a baseline gram-negative pathogen not resistant to either treatment and ≥105 colony-forming units [CFU]/mL in urine culture or the same pathogen present in concurrent blood and urine cultures) who achieved overall treatment success (defined as clinical cure combined with microbiological eradication [<103 CFU/mL in urine] of infection). Two-sided 95% CIs were computed using the stratified Newcombe method. The prespecified noninferiority margin was -10%. If noninferiority was established, a superiority comparison was also prespecified.

RESULTS

Among 1041 patients randomized (mean age, 54.7 years; 573 women [55.0%]), 1034 (99.3%) received study drug and 995 (95.6%) completed the trial. Among the primary analysis set, the primary outcome occurred in 79.1% (273/345) of patients receiving cefepime/enmetazobactam compared with 58.9% (196/333) receiving piperacillin/tazobactam (between-group difference, 21.2% [95% CI, 14.3% to 27.9%]). Treatment-emergent adverse events occurred in 50.0% (258/516) of patients treated with cefepime/enmetazobactam and 44.0% (228/518) with piperacillin/tazobactam; most were mild to moderate in severity (89.9% vs 88.6%, respectively). A total of 1.7% (9/516) of participants who received cefepime/enmetazobactam and 0.8% (4/518) of those who received piperacillin/tazobactam did not complete the assigned therapy due to adverse events.

CONCLUSIONS AND RELEVANCE

Among patients with complicated UTI or acute pyelonephritis caused by gram-negative pathogens, cefepime/enmetazobactam, compared with piperacillin/tazobactam, met criteria for noninferiority as well as superiority with respect to the primary outcome of clinical cure and microbiological eradication. Further research is needed to determine the potential role for cefepime/enmetazobactam in the treatment of complicated UTI and pyelonephritis.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03687255.

Cephalosporin as Potent Urease and Tyrosinase Inhibitor: Exploration through Enzyme Inhibition, Kinetic Mechanism, and Molecular Docking Studies

In present study, eleven cephalosporin drugs were selected to explore their new medically important enzyme targets with inherited safety advantage. To this end, selected drugs with active ingredient, cefpodoxime proxetil, ceftazidime, cefepime, ceftriaxone sodium, cefaclor, cefotaxime sodium, cefixime trihydrate, cephalexin, cefadroxil, cephradine, and cefuroxime, were evaluated and found to have significant activity against urease (IC50 = 0.06 ± 0.004 to 0.37 ± 0.046 mM) and tyrosinase (IC50 = 0.01 ± 0.0005 to 0.12 ± 0.017 mM) enzymes. Urease activity was lower than standard thiourea; however, tyrosinase activity of all drugs outperforms (ranging 6 to 18 times) the positive control: hydroquinone (IC50 = 0.18 ± 0.02 mM). Moreover, the kinetic analysis of the most active drugs, ceftriaxone sodium and cefotaxime sodium, revealed that they bind irreversibly with both the enzymes; however, their mode of action was competitive for urease and mixed-type, preferentially competitive for tyrosinase enzyme. Like in vitro activity, ceftriaxone sodium and cefotaxime sodium docking analysis showed their considerable binding affinity and significant interactions with both urease and tyrosinase enzymes sufficient for downstream signaling responsible for observed enzyme inhibition in vitro, purposing them as potent candidates to control enzyme-rooted obstructions in future.

Genotypic Distribution and Antimicrobial Susceptibilities of Carbapenemase-Producing Enterobacteriaceae Isolated From Rectal and Clinical Samples in Korean University Hospitals Between 2016 and 2019

Background

The emergence of carbapenemase-producing Enterobacteriaceae (CPE) represents a major clinical problem. Recently, the occurrence of CPE has increased globally, but epidemiological patterns vary across region. We report the trends in the genotypic distribution and antimicrobial susceptibility of CPE isolated from rectal and clinical samples during a four-year period.

Methods

Between January 2016 and December 2019, 1,254 nonduplicated CPE isolates were obtained from four university hospitals in Korea. Carbapenemase genotypes were determined by multiplex real-time PCR. Antimicrobial susceptibility was profiled using the Vitek 2 system (bioMérieux, Hazelwood, MO, USA) or MicroScan Walkaway-96 system (Siemens West Sacramento, CA, USA). The proportions of carbapenemase genotypes and nonsusceptibility were analyzed using Pearson’s chi-square test.

Results

Among the 1,254 CPE isolates, 486 (38.8%), 371 (29.6%), 357 (28.5%), 8 (0.6%), 8 (0.6%), and 24 (1.9%) were Klebsiella pneumoniae carbapenemase (KPC), oxacillinase (OXA)-48-like, New Delhi metallo-β-lactamase (NDM), imipenemase (IMP), Verona integron-encoded metallo-β-lactamase (VIM), and multiple producers, respectively. The predominant species was K. pneumoniae (72.6%), followed by Escherichia coli (6.5%). More than 90% of the isolates harboring KPC, NDM, and OXA-48-like were nonsusceptible to cephalosporins, aztreonam, and carbapenems.

Conclusions

The impact of CPE is primarily due to KPC-, NDM-, and OXA-48-like-producing K. pneumoniae isolates. Isolates carrying these carbapenemase are mostly multidrug-resistant. Control strategies based on these genotypic distributions and antimicrobial susceptibilities of CPE isolates are required.

In-Vitro Selection of Ceftazidime/Avibactam Resistance in OXA-48-Like-Expressing Klebsiella pneumoniae: In-Vitro and In-Vivo Fitness, Genetic Basis and Activities of β-Lactam Plus Novel β-Lactamase Inhibitor or β-Lactam Enhancer Combinations

Ceftazidime/avibactam uniquely demonstrates activity against both KPC and OXA-48-like carbapenemase-expressing Enterobacterales. Clinical resistance to ceftazidime/avibactam in KPC-producers was foreseen in in-vitro resistance studies. Herein, we assessed the resistance selection propensity of ceftazidime/avibactam in K. pneumoniae expressing OXA-48-like β-lactamases (n = 10), employing serial transfer approach. Ceftazidime/avibactam MICs (0.25–4 mg/L) increased to 16–256 mg/L after 15 daily-sequential transfers. The whole genome sequence analysis of terminal mutants showed modifications in proteins linked to efflux (AcrB/AcrD/EmrA/Mdt), outer membrane permeability (OmpK36) and/or stress response pathways (CpxA/EnvZ/RpoE). In-vitro growth properties of all the ceftazidime/avibactam-selected mutants were comparable to their respective parents and they retained the ability to cause pulmonary infection in neutropenic mice. Against these mutants, we explored the activities of various combinations of β-lactams (ceftazidime or cefepime) with structurally diverse β-lactamase inhibitors or a β-lactam enhancer, zidebactam. Zidebactam, in combination with either cefepime or ceftazidime, overcame ceftazidime/avibactam resistance (MIC range 0.5–8 mg/L), while cefepime/avibactam was the second best (MIC: 0.5–16 mg/L) in yielding lower MICs. The present work revealed the possibility of ceftazidime/avibactam resistance in OXA-48-like K. pneumoniae through mutations in proteins involved in efflux and/or porins without concomitant fitness cost mandating astute monitoring of ceftazidime/avibactam resistance among OXA-48 genotypes.

Assessment of cefepime toxicodynamics: comprehensive examination of pharmacokinetic/pharmacodynamic targets for cefepime-induced neurotoxicity and evaluation of current dosing guidelines

BACKGROUND

Cefepime-induced neurotoxicity (CIN) is an increasingly reported adverse event; however, the toxicity threshold remains unclear. This study was conducted to provide a comprehensive examination of the most appropriate threshold for CIN, and evaluate the ability of current dosing regimens to attain therapeutic targets.

METHODS

Data of the incidence of CIN and cefepime plasma concentrations were collected retrospectively from patients administered cefepime. Population pharmacokinetic modelling was used to determine daily cefepime trough concentration (C_min), maximum serum concentration and area under the concentration-time curve. The ability of each pharmacokinetic parameter to predict CIN was evaluated using receiver operating characteristic (ROC) curves, from which optimal toxicity thresholds were determined. Pharmacokinetic simulation was used to evaluate the ability of cefepime dosing guidelines to meet established efficacy targets, whilst maintaining exposure below the determined CIN threshold.

RESULTS

In total, 102 cefepime courses were evaluated, with CIN reported in 10. ROC analyses showed that all cefepime pharmacokinetic parameters were strongly predictive of CIN. C_min of 49 mg/L was identified as the optimal toxicity target, based on its predictive ability (0.88, 95% confidence interval 0.758-0.999, P<0.001) and ease of clinical use. Assessment of cefepime dosing regimens predicted that only 29% of simulated patients achieve therapeutic targets, with patients with impaired renal function more likely to exhibit subtherapeutic concentrations (89%), and patients with normal renal function likely to have potentially toxic exposure (64%).

CONCLUSIONS

The findings from this study provide evidence that cefepime exposure is highly predictive of CIN, with C_min of 49 mg/L being the most appropriate toxicity threshold. Further research is required to optimize cefepime dosing in the context of this therapeutic target.

In vivo activity of WCK 4282 (high-dose cefepime/tazobactam) against serine β-lactamase-producing Enterobacterales and Pseudomonas aeruginosa in the neutropenic murine thigh infection model

OBJECTIVES

WCK 4282, high-dose cefepime/tazobactam, possesses potent in vitro activity against Gram-negative organisms including ESBL- and cephalosporinase-harbouring strains. The purpose of this evaluation was to investigate the in vivo activity of human-simulated exposures of WCK 4282 against serine-β-lactamase-harbouring Enterobacterales and Pseudomonas aeruginosa.

METHODS

Nineteen clinical isolates were evaluated (ESBL/cephalosporinase producers, n = 8 Escherichia coli, n = 4 P. aeruginosa; KPC producers, n = 3 Klebsiella pneumoniae, n = 1 Klebsiella aerogenes; OXA-48/181 producers, n = 2 K. pneumoniae, n = 1 E. coli). WCK 4282 MICs ranged from 4 to 32 mg/L compared with 16 to >128 mg/L for cefepime. Thigh-infected neutropenic mice received cefepime, WCK 4282 or sham control over 24 h prior to harvest. Cefepime and tazobactam dosing regimens produced plasma profiles of fAUC, fT>MIC and fCmax similar to human exposure after WCK 4282 2/2 g every 8 h (1.5 h infusion).

RESULTS

Bacterial burdens (log10 cfu/thigh) were 5.81 ± 0.36 at 0 h and 9.29 ± 0.88 at 24 h in untreated controls. WCK 4282 produced potent activity against ESBL/cephalosporinase-producing strains with WCK 4282 MIC ≤16 mg/L; mean changes in log10 cfu/thigh from 0 h were -1.70 ± 0.77 and +1.86 ± 2.03 log10 cfu/thigh for WCK 4282 and cefepime human-simulated regimens, respectively. WCK 4282 produced variable activity against serine-carbapenemase-harbouring isolates. For the KPC-harbouring strains, WCK 4282 produced bacteriostasis with a mean -0.1 ± 0.61 log10 cfu/thigh. Against OXA-48/181-harbouring isolates, WCK 4282 produced a range of change in bacterial burden of -1.23 ± 0.33 to +1.04 ± 0.7 log10 cfu/thigh.

CONCLUSIONS

Human-simulated exposures of WCK 4282 produced in vivo efficacy against ESBL/cephalosporinase-producing, piperacillin/tazobactam- and ceftolozane/tazobactam-non-susceptible Enterobacterales and P. aeruginosa. These findings support further development of this combination as a carbapenem-sparing agent.

Low prevalence of tissue detection of cefepime and daptomycin used as empirical treatment during revision for periprosthetic joint infections: results of a prospective multicenter study

Data demonstrating that antibiotics administered intraoperatively in patients with surgical revision for periprosthetic joint infection achieve concentrations exceeding minimal inhibitory concentrations of the identified bacteria at the surgical site when the new implant is inserted are lacking. We prospectively included patients with periprosthetic joint infection operated with one- or two-stage replacement during which cefepime (2g)-daptomycin (10mg/kg) combination was administered intravenously as intraoperative empirical antibiotic treatment. Three biopsies (two bones and one synovial membrane) were taken from each patient just before the insertion of the new implant. Eighteen adults of median age 68 years were included. Knee was involved in 10 patients (55.6%) and surgery consisted in one-/two-stage replacement in 11/7 patients. A tourniquet was used during the intervention in the 10 patients with knee prosthesis. Among 54 tissue samples, cefepime and daptomycin were detected respectively in 35 (64.8%) and 21 (38.9%) cases (P=0.01). A total of 17 bacteria dominated by staphylococci (n=14) were identified in 10 patients; tissue inhibitory quotient calculated in 51 samples was >1 in 22 cases (43.1%) for cefepime and in 16 cases (31.4%) for daptomycin. The proportion of tissue samples with detectable antibiotic was significantly higher in hip versus knee prosthesis (P=0.03). The present study suggests that intraoperative empirical administration of cefepime-daptomycin combination during septic prosthetic joint replacement results in a high proportion of tissue samples in which at least one of the two antibiotics was not detected or at a low concentration despite satisfactory concomitant blood serum concentrations.

Structure-based identification of small molecules against influenza A virus endonuclease: an in silico and in vitro approach

Influenza viruses are known to cause acute respiratory illness, sometimes leading to high mortality rates. Though there are approved influenza antivirals available, their efficacy has reduced over time, due to the drug resistance crisis. There is a perpetual need for newer and better drugs. Drug screening based on the interaction dynamics with different viral target proteins has been a preferred approach in the antiviral drug discovery process. In this study, the FDA approved drug database was virtually screened with the help of Schrödinger software, to select small molecules exhibiting best interactions with the influenza A virus endonuclease protein. A detailed cytotoxicity profiling was carried out for the two selected compounds, cefepime and dolutegravir, followed by in vitro anti-influenza screening using plaque reduction assay. Cefepime showed no cytotoxicity up to 200 μM, while dolutegravir was non-toxic up to 100 μM in Madin-Darby canine kidney cells. The compounds did not show any reduction in viral plaque numbers indicating no anti-influenza activity. An inefficiency in the translation of the molecular interactions into antiviral activity does not necessarily mean that the molecules were inactive. Nevertheless, testing the molecules for endonuclease inhibition per se can be considered a worthwhile approach.

Drug use evaluation of cefepime at Khartoum North Teaching Hospital in Sudan

BACKGROUND

Cefepime is essentially used for life-threatening infections. Although overutilisation of antibiotics is strongly discouraged around the world, they are still overused in developing countries including Sudan.

OBJECTIVES

This study aims to evaluate the rational use of cefepime at Khartoum North Teaching Hospital-Sudan.

METHODS

A retrospective cross-sectional, hospital-based study was conducted in the internal medicine ward at Khartoum North Teaching Hospital from August/2018 to April/2019. The study covered medical records of adult patients receiving cefepime during the study period. Patient's data were analysed using simple descriptive statistics (frequency and percentage) and inferential statistics (logistic regression) to describe the relationship between dependent and independent variables. P ≤ .05 was considered statistically significant.

RESULTS

Out of 90 patients, only 16.7% of patients were tested for antibiotic sensitivity. Cefepime was prescribed to 50% and 23.3% of patients for the treatment of UTIs/post-dialysis and sepsis, respectively. Although the majority of patients (72.2%) received cefepime with appropriate indication, only 21.1% and 15.6% received the drug with appropriate dose and duration, respectively. Cefepime had been prescribed appropriately in a correct dose, duration, and indications for only 7.8% of patients. The vast majority of patients tested for kidney functions had elevated creatinine levels (96.1%); however, cefepime dose had been adjusted for only 4.1% of them.

CONCLUSION

This study highlighted the irrational use of cefepime regarding inappropriate dose, duration, and inadequate antibiotic sensitivity tests. A lack of attention to dosage adjustment in patients with renal impairment had been observed. Positive clinical outcome was significantly associated with antibiotic sensitivity test.

Third-generation cephalosporin resistance in clinical isolates of Enterobacterales collected between 2016-2018 from USA and Europe: genotypic analysis of β-lactamases and comparative in vitro activity of cefepime/enmetazobactam

OBJECTIVES

This study aimed to investigate third-generation cephalosporin (3GC) resistance determinants [extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases and OXA-type β-lactamases] in contemporary clinical Enterobacterales isolates and to determine the in vitro activity of β-lactams and β-lactam/β-lactamase inhibitor combinations, including the investigational combination of cefepime and the novel β-lactamase inhibitor enmetazobactam.

METHODS

Antibacterial susceptibility of 7168 clinical Enterobacterales isolates obtained between 2016-2018 from North America and Europe was determined according to CLSI guidelines. Phenotypic resistance to the 3GC ceftazidime (MIC ≥ 16 µg/mL) and/or ceftriaxone (MIC ≥ 4 µg/mL) but retaining susceptibility to meropenem (MIC ≤ 1 µg/mL) was determined. β-Lactamase genotyping was performed on clinical isolates with ceftazidime, ceftriaxone, cefepime or meropenem MIC ≥ 1 µg/mL.

RESULTS

Phenotypic resistance to 3GCs occurred in 17.5% of tested isolates, whereas 2.1% of isolates were resistant to the carbapenem meropenem. Within the 3GC-resistant subgroup, 60.1% (n = 752) of isolates encoded an ESBL, 25.6% (n = 321) encoded an AmpC-type β-lactamase and 0.9% (n = 11) encoded an OXA-type β-lactamase. Susceptibility of the subgroup to piperacillin/tazobactam (57.5%) and ceftolozane/tazobactam (71.3%) was <90% based on breakpoints established by the CLSI. Projected susceptibility to cefepime/enmetazobactam was 99.6% when applying the cefepime susceptible, dose-dependent breakpoint of 8 µg/mL. Against ESBL-producing isolates (n = 801) confirmed by genotyping, only susceptibility to meropenem (96.0%) and cefepime/enmetazobactam (99.9%) exceeded 90%.

CONCLUSION

This study describes the antibacterial activity of important therapies against contemporary 3GC-resistant clinical Enterobacterales isolates and supports the development of cefepime/enmetazobactam as a carbapenem-sparing option for ESBL-producing pathogens.

Activity of Imipenem, Meropenem, Cefepime, and Sulbactam in Combination with the β-Lactamase Inhibitor LN-1-255 against Acinetobacter spp

Treatment of infections caused by Acinetobacter spp., particularly A. baumannii, is a major clinical problem due to its high rates of antibiotic resistance. New strategies must be developed; therefore, restoration of β-lactam efficacy through the use of β-lactamase inhibitors is paramount. Activities of the antibiotics imipenem, meropenem, cefepime, and sulbactam in combination with the penicillin-sulfone inhibitor LN-1-255 were tested by microdilution against 148 isolates of Acinetobacter spp. collected in 14 hospitals in Spain in 2020. Relevantly, the MIC90 (i.e., minimum concentration at which 90% of isolates were inhibited) of antibiotics in combination with LN-1-255 decreased 4- to 8-fold for all of the Acinetobacter isolates. Considering only the carbapenem-resistant A. baumannii isolates, which produce carbapenem-hydrolyzing class D β-lactamases, the addition of LN-1-255 decreased the resistance rates from 95.1% to 0% for imipenem, from 100% to 9.8% for meropenem, from 70.7% to 7.3% for cefepime, and sulbactam resistance rates from 9.8% to 0% and intermediate susceptibility rates from 53.7% to 2.4%. The inhibitor also decreased the minimum inhibitory concentrations (MICs) when tested against non-carbapenem-resistant Acinetobacter spp. isolates. In conclusion, combining LN-1-255 with imipenem, meropenem, cefepime, and sulbactam to target A. baumannii, and especially carbapenem-resistant isolates, represents an attractive option that should be developed for the treatment of infections caused by this pathogen.

Discerning the role of polymicrobial biofilms in the ascent, prevalence, and extent of heteroresistance in clinical practice

Antimicrobial therapy is facing a worrisome and underappreciated challenge, the phenomenon of heteroresistance (HR). HR has been gradually documented in clinically relevant pathogens (e.g. Pseudomonas aeruginosa, Staphylococcus aureus, Burkholderia spp., Acinetobacter baumannii, Klebsiella pneumoniae, Candida spp.) towards several drugs and is believed to complicate the clinical picture of chronic infections. This type of infections are typically mediated by polymicrobial biofilms, wherein microorganisms inherently display a wide range of physiological states, distinct metabolic pathways, diverging refractory levels of stress responses, and a complex network of chemical signals exchange. This review aims to provide an overview on the relevance, prevalence, and implications of HR in clinical settings. Firstly, related terminologies (e.g. resistance, tolerance, persistence), sometimes misunderstood and overlapped, were clarified. Factors generating misleading HR definitions were also uncovered. Secondly, the recent HR incidences reported in clinically relevant pathogens towards different antimicrobials were annotated. The potential mechanisms underlying such occurrences were further elucidated. Finally, the link between HR and biofilms was discussed. The focus was to recognize the presence of heterogeneous levels of resistance within most biofilms, as well as the relevance of polymicrobial biofilms in chronic infectious diseases and their role in resistance spreading. These topics were subject of a critical appraisal, gaining insights into the ascending clinical implications of HR in antimicrobial resistance spreading, which could ultimately help designing effective therapeutic options.

Microbial Resistance Movements: An Overview of Global Public Health Threats Posed by Antimicrobial Resistance, and How Best to Counter

Antibiotics changed medical practice by significantly decreasing the morbidity and mortality associated with bacterial infection. However, infectious diseases remain the leading cause of death in the world. There is global concern about the rise in antimicrobial resistance (AMR), which affects both developed and developing countries. AMR is a public health challenge with extensive health, economic, and societal implications. This paper sets AMR in context, starting with the history of antibiotics, including the discovery of penicillin and the golden era of antibiotics, before exploring the problems and challenges we now face due to AMR. Among the factors discussed is the low level of development of new antimicrobials and the irrational prescribing of antibiotics in developed and developing countries. A fundamental problem is the knowledge, attitude, and practice (KAP) regarding antibiotics among medical practitioners, and we explore this aspect in some depth, including a discussion on the KAP among medical students. We conclude with suggestions on how to address this public health threat, including recommendations on training medical students about antibiotics, and strategies to overcome the problems of irrational antibiotic prescribing and AMR.

Resistance to Novel β-Lactam-β-Lactamase Inhibitor Combinations: The "Price of Progress"

Significant advances were made in antibiotic development during the past 5 years. Novel agents were added to the arsenal that target critical priority pathogens, including multidrug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales. Of these, 4 novel β-lactam-β-lactamase inhibitor combinations (ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam) reached clinical approval in the United States. With these additions comes a significant responsibility to reduce the possibility of emergence of resistance. Reports in the rise of resistance toward ceftolozane-tazobactam and ceftazidime-avibactam are alarming. Clinicians and scientists must make every attempt to reverse or halt these setbacks.

Bacterial Genome Wide Association Studies (bGWAS) and Transcriptomics Identifies Cryptic Antimicrobial Resistance Mechanisms in Acinetobacter baumannii

Antimicrobial resistance (AMR) in the nosocomial pathogen, Acinetobacter baumannii, is becoming a serious public health threat. While some mechanisms of AMR have been reported, understanding novel mechanisms of resistance is critical for identifying emerging resistance. One of the first steps in identifying novel AMR mechanisms is performing genotype/phenotype association studies; however, performing these studies is complicated by the plastic nature of the A. baumannii pan-genome. In this study, we compared the antibiograms of 12 antimicrobials associated with multiple drug families for 84 A. baumannii isolates, many isolated in Arizona, USA. in silico screening of these genomes for known AMR mechanisms failed to identify clear correlations for most drugs. We then performed a bacterial genome wide association study (bGWAS) looking for associations between all possible 21-mers; this approach generally failed to identify mechanisms that explained the resistance phenotype. In order to decrease the genomic noise associated with population stratification, we compared four phylogenetically-related pairs of isolates with differing susceptibility profiles. RNA-Sequencing (RNA-Seq) was performed on paired isolates and differentially-expressed genes were identified. In these isolate pairs, five different potential mechanisms were identified, highlighting the difficulty of broad AMR surveillance in this species. To verify and validate differential expression, amplicon sequencing was performed. These results suggest that a diagnostic platform based on gene expression rather than genomics alone may be beneficial in certain surveillance efforts. The implementation of such advanced diagnostics coupled with increased AMR surveillance will potentially improve A. baumannii infection treatment and patient outcomes.

Carbapenem-Sparing Strategies for ESBL Producers: When and How

Extended spectrum β-lactamase (ESBL)-producing bacteria are prevalent worldwide and correlated with hospital infections, but they have been evolving as an increasing cause of community acquired infections. The spread of ESBL constitutes a major threat for public health, and infections with ESBL-producing organisms have been associated with poor outcomes. Established therapeutic options for severe infections caused by ESBL-producing organisms are considered the carbapenems. However, under the pressure of carbapenem overuse and the emergence of resistance, carbapenem-sparing strategies have been implemented. The administration of carbapenem-sparing antibiotics for the treatment of ESBL infections has yielded conflicting results. Herein, the current available knowledge regarding carbapenem-sparing strategies for ESBL producers is reviewed, and the optimal conditions for the “when and how” of carbapenem-sparing agents is discussed. An important point of the review focuses on piperacillin–tazobactam as the agent arousing the most debate. The most available data regarding non-carbapenem β-lactams (i.e., ceftolozane–tazobactam, ceftazidime–avibactam, temocillin, cephamycins and cefepime) are also thoroughly presented as well as non β-lactams (i.e., aminoglycosides, quinolones, tigecycline, eravacycline and fosfomycin).

Heteroresistance to cefepime in Pseudomonas aeruginosa bacteraemia

INTRODUCTION

Heteroresistance to antibiotic agents can lead to diagnostic and therapeutic failures; however, to date, cefepime heteroresistance (FEP-HR) in Pseudomonas aeruginosa (P. aeruginosa) bacteraemia has not been characterised. The primary goal of this study was to investigate the molecular epidemiology, mechanisms and risk factors for cefepime-heteroresistant P. aeruginosa bacteraemia over approximately 6 years in Southwest China.

RESULTS

A high prevalence (57.3%) of heteroresistance to cefepime was observed during the study period, and these FEP-HR isolates were not clonally related. Mechanistic studies revealed that AmpC hyperproduction contributed to the development of this phenomenon. In addition, patients with advanced age, haematological malignancies, central venous catheters, and previous cephalosporin therapy were identified as independent risk factors for acquiring FEP-HR P. aeruginosa bacteraemia. Furthermore, patients infected with FEP-HR were generally at a greater risk for an adverse prognosis compared with those with non-FEP-HR. More importantly, characterisation of three successive P. aeruginosa isolates recovered from the same patient revealed that heteroresistance can act as an intermediate stage during the evolution from susceptibility to full resistance in patients undergoing antibiotic therapy for prolonged periods.

CONCLUSION

These findings emphasised the necessity of antimicrobial stewardship programs in clinical settings, as well as the need for some rapid screening methods for detecting this phenomenon.

Preserving the Dwindling β-lactams-Based Empiric Therapy Options for Gram-Negative Infections in Challenging Resistance Scenario: Lessons Learned and Way Forward

Appropriate empiric therapy reduces mortality and morbidity associated with serious Gram-negative infections. β-lactams (BLs) owing to their safety, efficacy, and coverage spectrum are the most preferred agents for empiric use. Inappropriate use of older penicillins and cephalosporins led to selection and spread of resistant clones. As a result, these valuable agents have lost their reliability compelling clinicians to often use erstwhile last-line therapies such as carbapenems. Excessive carbapenems use imposed collateral damage by selecting difficult-to-treat carbapenem-resistant organisms. Lack of empiric therapeutic options amenable for use in infections caused by contemporary pathogens was realized by the pharmaceutical industry leading to intensive efforts in discovering novel antibiotics. These efforts led to the approval of newer β-lactams and β-lactamase inhibitor (BL-BLI) combination. This review elaborates the past trends in empirical use of BLs and ensuing patterns of resistance emergence in Gram-negatives. Furthermore, a critical appraisal of newer BL-BLIs has been presented to identify the appropriate clinical situations for their use to ensure clinical efficacy coupled with minimal resistance selection. These learning have been derived from past trends of clinical usage of older empiric therapies so that the therapeutic utility of newer agents is preserved for long in light of dwindling global antibiotics pipeline.

Single-Center Investigation of the Pharmacokinetics of WCK 4282 (Cefepime-Tazobactam Combination) in Renal Impairment

WCK 4282 is a combination product of cefepime (FEP) and tazobactam (TAZ) in a 1:1 ratio currently under development for the treatment of multidrug-resistant Gram-negative bacterial infections. We investigated the effect of renal impairment on the pharmacokinetics (PK) and safety of WCK 4282 in 48 subjects with various degrees of renal function. Subjects were categorized on the basis of their Cockcroft-Gault equation-estimated creatinine clearance (CL_CR). We enrolled 6 subjects each into those with mild (CL_CR, 60 to <90 ml/min), moderate (CL_CR, 30 to <60 ml/min), or severe (CL_CR, <30 ml/min) renal impairment and those with end-stage renal disease (ESRD) requiring hemodialysis and 24 healthy control subjects (CL_CR, ≥90 ml/min). Healthy subjects and subjects with mild and moderate renal impairment received a single 90-min infusion of 4 g of WCK 4282 (2 g FEP and 2 g TAZ). Subjects with severe renal impairment and ESRD received 2 g of WCK 4282 (1 g FEP and 1 g TAZ) over 90 min. The plasma exposure of FEP-TAZ increased as renal function decreased. In subjects with mild, moderate, and severe renal impairment and ESRD, the mean exposure (area under the plasma concentration versus time curve from time zero extrapolated to infinity) of FEP and TAZ increased by 1.3- and 1.2-fold, 2.3- and 2.3-fold, 4.7- and 4.0-fold, and 8.5- and 11.6-fold, respectively. The urinary recovery of FEP and TAZ decreased with increasing renal impairment. There were no adverse events reported during the study. The findings suggest that dose adjustments for WCK 4282 will be required according to the degree of renal impairment. A single infusion of WCK 4282 was found to be safe and well tolerated in subjects with normal and impaired renal function. (This study has been registered at ClinicalTrials.gov under identifier NCT02709382.).

Development of Broth Microdilution MIC and Disk Diffusion Antimicrobial Susceptibility Test Quality Control Ranges for the Combination of Cefepime and the Novel β-Lactamase Inhibitor Enmetazobactam

Third-generation cephalosporin resistance among Enterobacteriaceae, mediated by the spread of extended-spectrum β-lactamases (ESBLs), is a very serious medical concern with limited therapeutic options. Enmetazobactam (formerly AAI101) is a novel penicillanic sulfone β-lactamase inhibitor active against a wide range of ESBLs. The combination of enmetazobactam and cefepime has entered phase 3 development in patients with complicated urinary tract infections. Using the Clinical and Laboratory Standards Institute (CLSI) M23 tier 2 study design, broth microdilution MIC and disk diffusion quality control (QC) ranges were determined for cefepime-enmetazobactam. Enmetazobactam was tested at a fixed concentration of 8 μg/ml in the MIC assay, and a cefepime-enmetazobactam disk mass of 30/20 μg was used in the disk diffusion assay. Escherichia coli ATCC 25922, E. coli ATCC 35218, E. coli NCTC 13353, Klebsiella pneumoniae ATCC 700603, and Pseudomonas aeruginosa ATCC 27853 were chosen as reference strains. The CTX-M-15-producing E. coli NCTC 13353 isolate is recommended for routine testing to control for inhibition of ESBL activity by enmetazobactam. Broth microdilution MIC QC ranges spanned 3 to 4 doubling dilutions and contained 99.6% to 100.0% of obtained MIC values for the five reference strains. Disk diffusion yielded inhibition zone diameter QC ranges that spanned 7 mm and encompassed 97.1% to 100.0% of the obtained values. Quality control ranges were approved by the CLSI in 2017 (broth microdilution MIC) and 2019 (disk diffusion). The established QC ranges will ensure that appropriate assay performance criteria are attained using CLSI reference methodology when determining the susceptibility of clinical isolates to cefepime-enmetazobactam.

Liquid chromatography-tandem mass spectrometry for the simultaneous quantitation of enmetazobactam and cefepime in human plasma

A simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous analysis enmetazobactam (also known as AAI101) and cefepime in human plasma. Sample preparation was based on protein precipitation with acetonitrile. Separation was performed on Acquity BEH HILIC column (50 mm × 2.1 mm, 1.7 μm) with a mobile phase containing ammonium formate in water and acetonitrile. The analytes were analyzed with the corresponding isotopically labeled internal standards and were detected in multiple reactions monitoring (MRM) using API 5000 triple-quadrupole mass spectrometer with electrospray (ESI) source operating in positive ion mode. The calibration curves were linear over the selected ranges (r > 0.9970 for both analytes). The intra and inter-assay precision of the Quality Control samples showed CV ≤ 15% and the accuracy was within 85 and 115% in all cases for both compounds. The lower limit of quantification was 0.05 μg/mL for enmetazobactam and 0.5 μg/mL for cefepime.

In Vitro Activity of Cefepime-Enmetazobactam against Gram-Negative Isolates Collected from U.S. and European Hospitals during 2014-2015

Enmetazobactam, formerly AAI101, is a novel penicillanic acid sulfone extended-spectrum β-lactamase (ESBL) inhibitor. The combination of enmetazobactam with cefepime has entered clinical trials to assess safety and efficacy in patients with complicated urinary tract infections. Here, the in vitro activity of cefepime-enmetazobactam was determined for 1,993 clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa collected in the United States and Europe during 2014 and 2015. Enmetazobactam at a fixed concentration of 8 μg/ml lowered the cefepime MIC₉₀ from 16 to 0.12 μg/ml for Escherichia coli, from >64 to 0.5 μg/ml for Klebsiella pneumoniae, from 16 to 1 μg/ml for Enterobacter cloacae, and from 0.5 to 0.25 μg/ml for Enterobacter aerogenes Enmetazobactam did not enhance the potency of cefepime against P. aeruginosa Applying the Clinical and Laboratory Standards Institute susceptible-dose-dependent (SDD) breakpoint of 8 μg/ml to cefepime-enmetazobactam for comparative purposes resulted in cumulative inhibitions of 99.9% for E. coli, 96.4% for K. pneumoniae, 97.0% for E. cloacae, 100% for E. aerogenes, 98.1% for all Enterobacteriaceae assessed, and 82.8% for P. aeruginosa Comparator susceptibilities for all Enterobacteriaceae were 99.7% for ceftazidime-avibactam, 96.2% for meropenem, 90.7% for ceftolozane-tazobactam, 87% for cefepime (SDD breakpoint), 85.7% for piperacillin-tazobactam, and 81.2% for ceftazidime. For the subset of ESBL-producing K. pneumoniae isolates, the addition of 8 μg/ml enmetazobactam to cefepime lowered the MIC₉₀ from >64 to 1 μg/ml, whereas the shift for 8 μg/ml tazobactam was from >64 to 8 μg/ml. Cefepime-enmetazobactam may represent a novel carbapenem-sparing option for empirical treatment of serious Gram-negative infections in settings where ESBL-producing Enterobacteriaceae are expected.

Gradual in vitro Evolution of Cefepime Resistance in an ST131 Escherichia coli Strain Expressing a Plasmid-Encoded CMY-2 β-Lactamase

Background

In a previous report, a clinical ST131 Escherichia coli isolate (Ec-1),producing a plasmid-encoded AmpC β-lactamase CMY-2, evolved in vivo under cefepime (FEP) treatment to the FEP-resistant Ec-2 strain expressing an extended-spectrum β-lactamase CMY-33. To compare factors responsible for in vitro and in vivo FEP resistance, we reproduced in vitro FEP resistance evolution in Ec-1.

Methods

FEP-resistant mutants were generated by subjecting Ec-1 (FEP MIC = 0.125 mg/L) to sub-inhibitory concentrations of FEP. MICs were obtained by broth microdilution or Etest. Strains were sequenced on an Illumina HiSeq platform. Transcriptional levels and plasmid copy numbers were determined by real-time PCR. Outer membrane proteins (OMPs) were extracted and separated by SDS-PAGE. Growth kinetics was evaluated by measuring OD₄₅₀.

Results

The CMY-2 expressed by Ec-1 evolved to a CMY-69 (strain EC-4) by an Ala294Pro substitution after 24 passages. After 30 passages, the FEP MIC increased to 256 mg/L (strain EC-32). SDS PAGE did not reveal any lack of OMPs in the mutant strains. However, bla_CMY transcription levels were up to 14-times higher than in Ec-1, which was partially explained by mutations in the upstream region of repA resulting in a higher copy number of the bla_CMY-harboring IncI1 plasmid. All mutants showed a slight growth defect but no significant difference in relative growth rates compared to Ec-1.

Conclusion

In vitro sub-inhibitory concentrations of FEP resulted in the selection of resistance mutations altering the H-10 helix of the CMY-2 and increasing the plasmid copy number. Appropriate dosing strategies may help preventing resistance evolution during treatments.

Effect of ampC derepression on cefepime MIC in Enterobacterales with chromosomally encoded inducible AmpC β-lactamase

OBJECTIVES

We aimed to evaluate the effect of ampC derepression on the cefepime MIC in different species of Enterobacterales with chromosomally encoded inducible AmpC β-lactamase.

METHODS

We analysed a large number of wild-type/mutant pairs (n = 1030 in total). Cefepime MICs were determined by broth microdilution according to EUCAST recommendations.

RESULTS

ampC derepression led to increases in MIC by up to 10 dilutions, and significant increases by > 2 MIC dilutions were common across species (744/1030 mutants (72.2%) in total). Interestingly, the frequency of cefepime S→I/S→R transitions varied considerably between species: 66.3% in Enterobacter cloacae complex (167/252 mutants), 1.1% in Klebsiella aerogenes (2/180 mutants), 18.1% in Citrobacter freundii complex (50/277 mutants), 36.4% in Hafnia alvei (59/162 mutants), 19.0% in Providencia rettgeri (4/21 mutants), 22.9% in Providencia stuartii (11/48 mutants), 12.3% in Serratia marcescens (7/57 mutants), 20.0% in Serratia liquefaciens (6/30 mutants) and 0% in Morganella morganii (0/3 mutants).

CONCLUSIONS

Our data show that the cefepime MIC is often increased by ampC derepression. However, the risk of S→I/S→R transition is dependent on the species.

Beyond Piperacillin-Tazobactam: Cefepime and AAI101 as a Potent β-Lactam-β-Lactamase Inhibitor Combination

Impeding, as well as reducing, the burden of antimicrobial resistance in Gram-negative pathogens is an urgent public health endeavor. Our current antibiotic armamentarium is dwindling, while major resistance determinants (e.g., extended-spectrum β-lactamases [ESBLs]) continue to evolve and disseminate around the world. One approach to attack this problem is to develop novel therapies that will protect our current agents. AAI101 is a novel penicillanic acid sulfone β-lactamase inhibitor similar in structure to tazobactam, with one important difference. AAI101 possesses a strategically placed methyl group that gives the inhibitor a net neutral charge, enhancing bacterial cell penetration. AAI101 paired with cefepime, also a zwitterion, is in phase III of clinical development for the treatment of serious Gram-negative infections. Here, AAI101 was found to restore the activity of cefepime against class A ESBLs (e.g., CTX-M-15) and demonstrated increased potency compared to that of piperacillin-tazobactam when tested against an established isogenic panel. The enzymological properties of AAI101 further revealed that AAI101 possessed a unique mechanism of β-lactamase inhibition compared to that of tazobactam. Additionally, upon reaction with AAI101, CTX-M-15 was modified to an inactive state. Notably, the in vivo efficacy of cefepime-AAI101 was demonstrated using a mouse septicemia model, indicating the ability of AAI101 to bolster significantly the therapeutic efficacy of cefepime in vivo The combination of AAI101 with cefepime represents a potential carbapenem-sparing treatment regimen for infections suspected to be caused by Enterobacteriaceae expressing ESBLs.

Single-Center Evaluation of the Pharmacokinetics of WCK 5222 (Cefepime-Zidebactam Combination) in Subjects with Renal Impairment

WCK 5222 is a novel β-lactam-β-lactam-enhancer combination of cefepime (FEP) and zidebactam (ZID). ZID is a novel β-lactam enhancer with a dual action of binding to Gram-negative penicillin-binding protein 2 (PBP2) and β-lactamase inhibition. WCK 5222 is being developed as a new therapeutic option for the treatment of complicated multidrug-resistant Gram-negative pathogen infections. We investigated the effect of renal impairment on the pharmacokinetics (PK) and safety of WCK 5222 in 48 subjects based on Cockcroft-Gault-estimated creatinine clearance (CLCR). We enrolled mild (n = 6; CLCR, 60 to <90 ml/min), moderate (n = 6; CLCR, 30 to <60 ml/min), and severe (n = 6; CLCR, <30 ml/min; not on dialysis) impairment, end-stage renal disease (ESRD) on hemodialysis (HD) (n = 6), and matched normal controls (n = 24; CLCR, ≥90 ml/min). Healthy control subjects and mild and moderate renal impairment subjects received a single 60-min intravenous (i.v.) infusion of 3 g WCK 5222 (2 g FEP/1 g ZID); severe renal impairment and HD subjects received a single 60-min i.v. infusion of 1.5 g WCK 5222 (1 g FEP plus 0.5 g ZID). Body and renal clearance decreased, and plasma half-life (t1/2) and the area under the concentration-time curve from time zero extrapolated to infinity (AUC0-∞ [h µg/ml]) increased in a graded relationship with severity of renal impairment for both FEP and ZID. Our findings suggest that dose adjustments for WCK 5222 will be required according to the degree of renal impairment. Overall, WCK 5222 (FEP-ZID) was found to be safe and well tolerated in subjects with normal and impaired renal function. (This study has been registered at ClinicalTrials.gov under identifier NCT02942810.).

In Vivo Efficacy of Humanized WCK 5222 (Cefepime-Zidebactam) Exposures against Carbapenem-Resistant Acinetobacter baumannii in the Neutropenic Thigh Model

Herein, we describe the in vivo efficacy of human-simulated WCK 5222 (cefepime-zidebactam) exposure against carbapenem-resistant Acinetobacter baumannii strains in a neutropenic murine thigh infection model. Five of the six isolates examined expressed OXA-23 or OXA-24. WCK 5222, despite showing MICs of 16 to 64 mg/liter, produced remarkable in vivo activity; human-simulated exposure showed a decline in the bacterial burden for all isolates (mean reduction, -2.09 ± 1.01 log₁₀ CFU/thigh), while a lack of activity was observed with cefepime and zidebactam monotherapies.

Monitoring of cefepime in urine by micellar electrokinetic capillary chromatography with ultraviolet detection and liquid chromatography coupled to mass spectrometry

Cefepime monitoring in urine by micellar electrokinetic capillary chromatography with UV detection and liquid chromatography coupled to mass spectrometry via electrospray ionization is described. For micellar electrokinetic capillary chromatography, sample preparation comprised urine dilution and dodecyl-sulfate protein precipitation at pH 4.5, whereas diluted urines were analyzed in the other assay. Both approaches provided suitable conditions for cefepime analysis in urines of healthy volunteers that were spiked with cefepime. Cefepime monitoring by micellar electrokinetic capillary chromatography in samples from patients taking multiple drugs were prone to interferences, whereas liquid chromatography coupled to mass spectrometry provided clean chromatograms and thus selective detection of cefepime in all samples. The latter assay was used to measure urinary cefepime in a prospective pilot study and to assess cefepime stability in urines at 25, 4, -20 and -70°C. The data suggest that urinary cefepime is stable for at least 72 h at all tested temperatures.

A Randomized Pharmacokinetic and Pharmacodynamic Evaluation of Every 8-Hour and 12-Hour Dosing Strategies of Vancomycin and Cefepime in Neurocritically ill Patients

PURPOSE

Neurocritically ill patients have clinically significant alterations in pharmacokinetic parameters of renally eliminated medications that may result in subtherapeutic plasma and cerebrospinal fluid antibiotic concentrations.

METHODS

We conducted a prospective randomized open-label study of adult neurocritically ill patients treated with vancomycin and cefepime. Vancomycin 15 mg/kg and cefepime 2 g were dosed at every-8- or 12-hour intervals. The primary outcomes were the achievement of pharmacodynamic (PD) targets related to time of unbound drug above minimum inhibitory concentrations (MIC) for 60% or more of the dosing interval (fT > MIC ≥ 60%) for β-lactams and ratio of 24-hour area under the curve (AUC):MIC of 400 or greater for vancomycin.

RESULTS

Twenty patients were included in the study. They were divided equally between the every-12-hour and every-8-hour dosing groups. Patients (mean age 51.8 ± 11 yrs) were primarily male (60%) and white (95%), and most had an admission diagnosis of intracranial hemorrhage (80%). Compared with the every-12-hour group, the every-8-hour vancomycin group achieved target trough concentrations (higher than 15 μg/ml) significantly more frequently at initial measurement (0% vs 80%, p<0.01) and at 7-10 days (0% vs 90%, p=0.045) and achieved PD targets more frequently at increasing MICs. Similarly, compared with every-12-hour dosing, the every-8-hour cefepime dosing strategy significantly increased PD target attainment (fT > MIC ≥ 60%) at an MIC of 8 μg/ml (20% vs 70%, p=0.02).

CONCLUSIONS

This study demonstrated that more frequent dosing of vancomycin and cefepime is required to achieve optimal PD targets in adult neurocritically ill patients. The need for increased total daily doses is potentially secondary to the development of augmented renal clearance.

Antimicrobial susceptibility of common pathogens isolated from postoperative intra-abdominal infections in Japan

The principle of empirical therapy for patients with intra-abdominal infections (IAI) should include antibiotics with activity against Enterobacteriaceae and Bacteroides fragilis group species. Coverage of Pseudomonas aeruginosa, Enterobacter cloacae, and Enterococcus faecalis is also recommended for hospital-associated IAI. A nationwide survey was conducted to investigate the antimicrobial susceptibility of pathogens isolated from postoperative IAI. All 504 isolates were collected at 26 institutions and referred to a central laboratory for susceptibility testing. Lower susceptibility rates to ciprofloxacin and cefepime were demonstrated in Escherichia coli. Among E. coli, 24.1% of strains produced extended-spectrum β-lactamase (ESBL). Carbapenems, piperacillin/tazobactam, cephamycins/oxacephem, aminoglycosides, and tigecycline had high activity against E. coli, including ESBL-producing isolates. Among E. cloacae, low susceptibility rates to ceftazidime were demonstrated, whereas cefepime retained its activity. P. aeruginosa revealed high susceptibility rates to all antimicrobials tested except for imipenem. Among B. fragilis group species, low levels of susceptibility were observed for cefoxitin, moxifloxacin, and clindamycin, and high susceptibility rates were observed for piperacillin/tazobactam, meropenem, and metronidazole. Ampicillin, piperacillin, and glycopeptides had good activity against E. faecalis. Imipenem had the highest activity against E. faecalis among carbapenems. In conclusion, we suggested the empirical use of antimicrobials with the specific intent of covering the main organisms isolated from postoperative IAI. Piperacillin/tazobactam, meropenem, or doripenem, are appropriate in critically ill patients. Combination therapy of cefepime (aztreonam in patients with β-lactam allergy) plus metronidazole plus glycopeptides, imipenem/cilastatin or cephamycins/oxacephem plus ciprofloxacin plus metronidazole are potential therapeutic options.

Pseudomonas Endocarditis with an unstable phenotype: the challenges of isolate characterization and Carbapenem stewardship with a partial review of the literature

Background

Pseudomonas endocarditis is exceedingly rare, especially in patients without predisposing risks. We present such a case that included unexpected switches in antibacterial resistance profiles in two Pseudomonas aeruginosa (PA) strains with the same whole-genome sequence. The case also involved diagnostic and treatment challenges, such as issues with automated testing platforms, choosing the optimal aminoglycoside, minimizing unnecessary carbapenem exposure, and the need for faster, more informative laboratory tests.

Case presentation

On hospital day one (HD-1) a cefepime and piperacillin-tazobactam (FEP-TZP)-susceptible P. aeruginosa was isolated from the bloodstream of a 62-year-old man admitted for evaluation of possible endocarditis and treated with gentamicin and cefepime. On HD-2, his antibiotic regimen was changed to tobramycin and cefepime. On HD-11, he underwent aortic valve replacement, and P. aeruginosa was isolated from the explanted valve. Unexpectedly, it was FEP-TZP-resistant, so cefepime was switched to meropenem. On HD-14, in preparation for whole-genome sequencing (WGS), valve and blood isolates were removed from cryo-storage, re-cultured, and simultaneously tested with the same platforms, reagents, and inoculations previously used. Curiously, the valve isolate was now FEP-TZP-susceptible. WGS revealed that both isolates were phylogenetically identical, differing by a single nucleotide in a chemotaxis-encoding gene. They also contained the same resistance genes (bla_ADC35, aph(3′)-II, bla_OXA-50, catB7, fosA).

Conclusion

Repeated testing on alternate platforms and WGS did not definitively determine the resistance mechanism(s), which in this case, is most likely unstable de-repression of a chromosomal AmpC β-lactamase, porin alterations, or efflux upregulation, with reversion to baseline (non-efflux) transcription. Although sub-culture on specialized media to select for less fit (more resistant) colonies, followed by transcriptome analysis, and multiple sequence alignment, might have revealed the mechanism and better informed the optimal choice of β-lactam, such approaches are neither rapid, nor feasible for hospital laboratories. In this era of escalating drug resistance and dwindling antibiotics, use of the most potent anti-pseudomonals must be balanced with stewardship. Clinicians need access to validated genomic correlates of resistance, and faster, more informative diagnostics. Therefore, we placed these isolates and their sequences in the public domain for inclusion in the Pseudomonas pan-genome and database projects for further countermeasure development.

Influence of borderline cefepime MIC on the outcome of cefepime-susceptible Pseudomonas aeruginosa bacteremia treated with a maximal cefepime dose: a hospital-based retrospective study

BACKGROUND

We assessed the influence of current cefepime minimal inhibitory concentration (MIC) breakpoints and the maximal cefepime dose on treatment outcomes in patients with bacteremia caused by cefepime-susceptible Pseudomonas aeruginosa.

METHODS

Adult patients hospitalized between July 2010 and June 2014 with a positive blood culture for cefepime-susceptible P. aeruginosa and receipt of cefepime as the primary therapy throughout the course were reviewed. Cefepime Etest^® MICs and clinical outcomes for P. aeruginosa bacteremia were reviewed to identify the MIC breakpoint influencing treatment outcomes.

RESULTS

Of the 90 patients enrolled, 49 (54.4%) were male (mean age = 66.8 years). The mean Acute Physiology and Chronic Health Evaluation II score was 22.01. Sixty patients (66.7%) received a maximal cefepime dose, and the 30-day crude mortality rate was 36.7%. MIC₉₀ of cefepime for P. aeruginosa was 8 mg/L. The cumulative survival rate at 30 days revealed that a lower cefepime MIC (<4 mg/L) for P. aeruginosa was associated with a higher survival rate than a higher MIC (≥4 mg/L) (72.6% vs. 23.5%, p < 0.0001). A cefepime MIC of ≥4 mg/L and age were independent risk factors for mortality, whereas the maximal cefepime dose was the independent protective factor. The use of a maximal cefepime dose did not improve the outcomes of patients with P. aeruginosa bacteremia at a MIC of ≥4 mg/L.

CONCLUSIONS

A cefepime MIC of 4 mg/L may predict an unfavorable outcome among patients with serious infections caused by P. aeruginosa, even the MICs still within the CLSI susceptibility breakpoint.

WCK 5222 (Cefepime-Zidebactam) Antimicrobial Activity against Clinical Isolates of Gram-Negative Bacteria Collected Worldwide in 2015

WCK 5222 consists of cefepime combined with zidebactam, a bicyclo-acyl hydrazide β-lactam enhancer antibiotic with a dual action involving binding to Gram-negative bacterial PBP2 and β-lactamase inhibition. We evaluated the in vitro activity of cefepime-zidebactam against 7,876 contemporary (2015) clinical isolates of Enterobacteriaceae (n = 5,946), Pseudomonas aeruginosa (n = 1,291), and Acinetobacter spp. (n = 639) from the United States (n = 2,919), Europe (n = 3,004), the Asia-Pacific (n = 1,370), and Latin America (n = 583). The isolates were tested by a reference broth microdilution method for susceptibility against cefepime-zidebactam (1:1 and 2:1 ratios) and comparator agents. Cefepime-zidebactam was the most active compound tested against Enterobacteriaceae (MIC50/90, ≤0.03/0.12 μg/ml [1:1] and 0.06/0.25 μg/ml [2:1]; 99.9% of isolates were inhibited at ≤4 [1:1] and ≤8 μg/ml [2:1]). Cefepime-zidebactam was active against individual Enterobacteriaceae species (MIC50/90, ≤0.03 to 0.06/≤0.03 to 0.5 μg/ml [1:1]) and retained potent activity against carbapenem-resistant isolates (MIC50/90, 1/4 μg/ml; 99.3% of isolates were inhibited at ≤8 μg/ml [1:1]). Cefepime-zidebactam activity was consistent among geographic regions, and only one isolate showed MIC values of >8 μg/ml (1:1). Cefepime-zidebactam was also very active against P. aeruginosa with MIC50/90 values of 1/4 μg/ml, and 99.5% of isolates were inhibited at ≤8 μg/ml (1:1). The MIC values for cefepime-zidebactam at the 1:1 ratio were generally 2-fold lower than those for cefepime-zidebactam at the 2:1 ratio (MIC50/90, 2/8 μg/ml) and zidebactam alone (MIC50/90, 4/8 μg/ml). Against Acinetobacter spp., cefepime-zidebactam at 1:1 and 2:1 ratios (MIC50/90, 16/32 μg/ml for both) was 4-fold more active than cefepime or ceftazidime. Zidebactam exhibited potent in vitro antimicrobial activity against some organisms. These results support the clinical development of WCK 5222 for the treatment of Gram-negative bacterial infections, including those caused by multidrug-resistant isolates.

Antimicrobial Activity of High-Proportion Cefepime-Tazobactam (WCK 4282) against a Large Number of Gram-Negative Isolates Collected Worldwide in 2014

Cefepime-tazobactam (WCK 4282) is currently under clinical development for use at a dosage of 2 g/2 g every 8 h. A total of 7,981 isolates were collected from 146 medical centers (39 countries) in 2014 as a part of the SENTRY Antimicrobial Surveillance Program, and their susceptibilities to cefepime-tazobactam (with tazobactam at fixed concentrations of 4 and 8 μg/ml) were tested by a reference broth microdilution method. Isolates were mainly from patients with pneumonia (29.5%) and bloodstream infections (26.9%). Cefepime-tazobactam (with tazobactam at a fixed concentration of 8 μg/ml) and cefepime inhibited 96.9 and 87.9% of Enterobacteriaceae strains at ≤8 μg/ml. The activity of cefepime-tazobactam against Enterobacteriaceae strains was comparable to that of meropenem (96.7% of isolates were susceptible) and greater than that of piperacillin-tazobactam (87.7% susceptible). All Enterobacteriaceae species from the United States except Klebsiella pneumoniae had >99.0% of isolates inhibited by cefepime-tazobactam at ≤8/8 μg/ml. The prevalence of the extended-spectrum β-lactamase (ESBL)-screening-positive phenotype was the highest among Escherichia coli isolates in China (66.3%) and among K. pneumoniae isolates (58.0%) in Latin America. Cefepime-tazobactam at ≤8/8 μg/ml inhibited 98.7 and 71.3% of ESBL-screening-positive phenotype E. coli strains and K. pneumoniae strains, respectively. Meropenem showed limited activity against ESBL-screening-positive phenotype K. pneumoniae strains (69.6% susceptible). Cefepime-tazobactam was active against Enterobacter spp. (MIC₅₀ and MIC₉₀, 0.06 and 0.5 μg/ml, respectively), including ceftazidime-nonsusceptible isolates (96.1% of isolates were inhibited by cefepime-tazobactam at ≤8/8 μg/ml). The activity of cefepime-tazobactam against Pseudomonas aeruginosa (82.4 and 91.6% of isolates were inhibited by cefepime-tazobactam at ≤8/8 and ≤16/8 μg/ml, respectively) was comparable to that of meropenem and piperacillin-tazobactam (79.2% susceptible). In summary, cefepime-tazobactam was highly active against P. aeruginosa and Enterobacteriaceae strains, including ESBL-screening-positive phenotype E. coli strains and ceftazidime-nonsusceptible Enterobacter spp. These results support the further clinical development of the cefepime-tazobactam combination.

Updates in the Management of Cephalosporin-Resistant Gram-Negative Bacteria

Resistance to cephalosporins is now common among Gram-negative bacterial infections, including those caused by the Enterobacteriaceae and Pseudomonas aeruginosa, posing a major threat to public health. As resistance to the traditional drugs of choice for these infections, carbapenems, has also become increasingly common, interest in cefepime and piperacillin-tazobactam as carbapenem-sparing alternatives has increased. Additionally, the availability of the novel β-lactam-β-lactamase inhibitor combinations ceftolozane-tazobactam and ceftazidime-avibactam has added to the antimicrobial armamentarium available to treat these multidrug-resistant infections. Here, we review the recent literature on the use of carbapenem-sparing alternatives and highlight the potential utility of novel antimicrobials.