Sparing carbapenem usage

A high-resolution genomic and phenotypic analysis of resistance evolution of an Escherichia coli strain from a critically unwell patient treated with piperacillin/tazobactam

Introduction. Resistance to the β-lactam/β-lactamase inhibitor (BL/BLI) combination antibiotic piperacillin/tazobactam (TZP) predominantly occurs via β-lactamase enzymes, also leading to resistance to third-generation cephalosporins (3GCs). However, if β-lactamases inactive against 3GCs and inhibited by tazobactam are expressed at high levels, leading to enzyme hyperproduction, the surplus enzyme escapes inhibition by tazobactam and inactivates the antibiotic piperacillin.Hypothesis/Gap statement. Understanding this mechanism is clinically relevant, as enzyme hyperproduction can emerge upon antibiotic administration, resulting in treatment failure despite initial resistance profiles supporting TZP use.Aim. Our aim was to determine whether this was a case of within-patient evolution and by what mechanism or an acquisition of a second unrelated, more resistant, strain.Methodology. Whole-genome sequencing was performed on the isolate to determine the genetic basis of resistance. We also assessed the impact of TZP exposure on the amplification of the bla TEM-1 gene and monitored the stability of gene copy number over 5 days in the absence of antibiotic pressure. In addition, we determined the MICs of ceftriaxone and TZP, with TZP MIC contextualized in relation to gene copy number and resistance levels.Results. We report the identification of an Escherichia coli isolate that developed resistance to TZP during patient treatment but maintained sensitivity to ceftriaxone. We show that TZP resistance evolved via IS26-mediated duplication of a bla TEM-1 containing transposable unit on a plasmid, resulting in hyperproduction of TEM-1 β-lactamase, and that ten copies of bla TEM-1 induce resistance greater than 32 times the MIC. Furthermore, under experimental conditions, exposure to TZP further increases amplification of bla TEM-1, whereas, in the absence of TZP, gene copy number of IS26 and bla TEM-1 remains stable over 5 days, despite a 48,205 bp genome size increase compared to the pre-amplification isolate. We additionally detect phenotypic changes that might indicate host adaptation potentially linked to the additional genes that are amplified.Conclusion. Our analysis advances the understanding of infections caused by isolates evolving β-lactamase hyperproduction, which represents a complex problem in both detection and treatment. As 40% of antibiotics active against WHO priority pathogens in the pre-clinical pipeline are BL/BLI combinations, further investigations are of urgent concern.

Preserving the antimicrobial arsenal: exploring alternatives to carbapenems in ESBL battles within the southeast of Ireland

Introduction. Carbapenems are usually employed as first-line antimicrobials against bacteria harbouring extended-spectrum beta-lactamases (ESBLs). These enzymes confer resistance often to multiple classes of antimicrobials.Hypothesis/Gap Statement. This indiscriminate use of carbapenems and the inevitable development of carbapenem resistance have prompted the need for carbapenem-sparing strategies.Methodology. The non-carbapenem antimicrobial susceptibility patterns of 60 ESBL-producing Enterobacterales (ESBL-PE) isolates responsible for bloodstream infections, in 2022-2023 inclusive, processed at our institution were reviewed.Results. The non-carbapenem antimicrobial susceptibility patterns of 60 ESBL-PE isolates from bloodstream infections during the study period were determined. Escherichia coli was the most common species isolated (87%, n=52), with the majority of cases (73.3%, n=44) originating from a presumed urinary source. Temocillin (TMC), mecillinam (MEC), cefiderocol (FDC), amikacin and fosfomycin (FOS) displayed excellent activity against all ESBL-PE isolates tested, with susceptibility rates of≥85%. Ciprofloxacin and amoxicillin-clavulanic acid were the least efficacious agents, with susceptibility rates≤20%.Conclusions. TMC, MEC, FDC and FOS offer promising alternatives to carbapenems, demonstrating efficacy against ESBL-PE. The use of these agents not only broadens the therapeutic arsenal against ESBL-PE but also mitigates the potential for escalating carbapenem resistance, especially in regions where the incidence of carbapenem resistance is increasing.

Carbapenem Usage in the Initial Antibiotic Therapy of Sepsis in Japanese Intensive Care Units

Background Achieving a balance between the utilization and limitation of carbapenems for initial sepsis therapy is imperative, yet documentation on the use of carbapenems in sepsis treatment is limited. This study aimed to ascertain the prevalence of carbapenem use in Japanese intensive care units (ICUs) and evaluate the association between its use in the initial antibiotic therapy for sepsis and patient prognosis.  Methods This study is a post hoc descriptive analysis of the Focused Outcome Research on Emergency Care for Acute Respiratory Distress Syndrome, Sepsis, and Trauma (FORECAST), a multicenter, prospective cohort study conducted in 59 ICUs in Japan from January 2016 to March 2017. This study described the rate of carbapenem use overall and in each ICU and assessed the association between carbapenem use and in-hospital mortality by generalized linear mixed effect model adjusting for patient characteristics as fixed effect confounders and the hospitals as random effect confounders. Results Out of 1140 participants, 627(55.0%) received and 513 (45.0%) did not receive carbapenems following the diagnosis of severe sepsis or septic shock. Patient severity was similar in both groups in terms of Sepsis-related Organ Failure Assessment (SOFA; 9 and 8) and Acute Physiology and Chronic Health Evaluation II (APACHE II; 23 and 22) scores. Among 48 of the 59 ICUs that registered more than three patients in the FORECAST registry, the median carbapenem utilization rate stood at 55.2% (minimum: 20.0%, maximum: 100.0%, IQR: 43.6%-67.2%). Hospital mortality rates were 25.6% and 20.5% in carbapenem recipients and non-recipients, respectively. A correlation between initial carbapenem use and increased in-hospital mortality was discerned in the unadjusted model (difference of 5.2%), but this association was not evident in the adjusted model (difference of 1.2%; 95%CI: -4.3,6.6; p=0.66). Conclusions Initial antibiotic therapy with carbapenems was noted in over half of the sepsis patients in Japanese ICUs. In-hospital mortality was not associated with the use of carbapenems.

Effects of meropenem supply restriction: A multicenter retrospective study

BACKGROUND

In Japan, the supply of one generic meropenem product was restricted from August 2022 to March 2023.

OBJECTIVE

To determine the effects of meropenem (MEPM) restriction.

METHODS

We conducted a multicenter retrospective study comparing antimicrobial use, bacteremia mortality, and drug-resistant bacteria detected before the restriction of MEPM (control period), from September 2021 to February 2022, and after the restriction of MEPM (MEPM supply restriction period), from September 2022 to February 2023, in five institutions.

RESULTS

The number of carbapenem days of therapy (DOTs) were decreased in all five institutions. Fourth-generation cephalosporin DOTs increased in all facilities, and piperacillin/tazobactam DOTs increased in four facilities. The 30-day and 90-day mortality rates were significantly higher during the MEPM supply restriction period than those during the control period. Moreover, survival time was significantly shorter during the MEPM supply restriction period than that during the control period. Multivariable analysis revealed that MEPM supply restriction, age >80 years, Pitt Bacteremia Score ≥4, platelet count <10 × 104/μL, serum albumin level <2.5 g/dL, and methicillin-resistant Staphylococcus aureus bloodstream infection were independent risk factors for 30-day mortality. The detection rates of carbapenem-resistant Pseudomonas aeruginosa and Enterobacteriaceae did not differ significantly between the two periods.

CONCLUSIONS

MEPM supply restriction decreased the use of carbapenems and increased the use of other broad-spectrum antimicrobial agents, which worsened the prognosis of bacteremia. Overall, carbapenems are important drugs for the treatment of infectious diseases and are difficult to replace in unforeseen situations such as drug supply outages.

Activity of ceftolozane/tazobactam and comparators against gram-negative bacilli: Results from the Study for Monitoring Antimicrobial Resistance Trends (SMART - Brazil), 2018‒2021

Increased spread of antimicrobial resistance by Gram-Negative Bacilli (GNB) poses a global challenge, with exacerbated burden post-pandemic. The aim of this study was to investigate the in vitro activity of ceftolozane/tazobactam and its comparators against the frequently identified GNB isolated from patients admitted to Brazilian medical sites between the year 2018‒2019 and 2020‒2021. The impact of pandemic on antimicrobial resistance and presence of β-lactamase genes were also evaluated. Antimicrobial susceptibility testing and molecular characterization of ß-lactamase encoding genes using Polymerase Chain Reaction (PCR) and DNA sequencing were carried out from GNB isolated mostly from intra-abdominal, respiratory, and urinary tract infections and interpreted following BrCAST/EUCAST guidelines. A total of 3994 GNB isolates were evaluated which mostly included E. coli, K. pneumoniae and P. aeruginosa. Ceftolozane/tazobactam remained highly active against E. coli isolates during both 2018‒2019 (96.0 %) and 2020‒2021 (98.5 %). Among K. pneumoniae, ceftolozane/tazobactam (47.6 % and 43.0 % susceptible during 2018‒2019 and 2020‒2021, respectively) showed poor activity due to blaKPC-2. Colistin and ceftolozane/tazobactam were the most active β-lactam agents tested against P. aeruginosa in 2018‒2019 (99.3 % and 88.8 %) and 2020‒2021 (100 % and 92.8 %), including ceftazidime and meropenem resistant isolates. β-lactamase encoding gene characterization was carried out and both carbapenemases and Extended-Spectrum β-Lactamase (ESBL) producers were found in E. coli, K. pneumoniae and P. aeruginosa isolates. Ceftolozane/tazobactam documented remarkable in vitro activity against E. coli and P. aeruginosa isolates in Brazil, both pre- and post-pandemic periods and could constitute an effective therapeutic option for the treatment of urinary tract infections, intra-abdominal infections, and respiratory tract infections.

Policy options for sustainable access to off-patent antibiotics in Europe

Securing sustainable access to existing antibiotics optimises agent choice for individual treatments and is crucial to curb antibiotic resistance. Access to antibiotics is often restricted in many countries, due to general market unavailability or episodic shortages. This article outlines key policy options to maintain availability of existing antibiotics and enhance antibiotic supply chain resilience focusing on the perspectives of European Union (EU) and European Economic Area (EEA) institutions and member states.

Efficacy of carbapenems and alternative antimicrobials for treating complicated urinary tract infections caused by third-generation cephalosporin-resistant gram-negative bacteria: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Specific data concerning the efficacy of alternative antibiotics for carbapenems against complicated urinary tract infections (cUTIs) attributed to antimicrobial-resistant (AMR) uropathogens are lacking.

OBJECTIVES

This study aimed to assess the efficacy of carbapenems and non-carbapenem antibiotics in the clinical outcomes of cUTIs caused by AMR uropathogens.

METHODS

In this systematic review and meta-analysis, databases, including MEDLINE/PubMed, the Cochrane Library, Embase and ClinicalTrials.gov, were searched. The study eligibility criteria were research articles conducted as randomised controlled trials that evaluated the composite outcomes of cUTIs. Participants were adult patients with cUTIs caused by gram-negative uropathogens resistant to third-generation cephalosporins. The intervention involved a non-carbapenem class of antimicrobial agents with in vitro activities against gram-negative uropathogens resistant to third-generation cephalosporins. Two independent researchers assessed the risk-of-bias using the second version of the Cochrane risk-of-bias tool for randomised trials. The treatment effects on each outcome were estimated as a risk ratio (RR) with a 95 % confidence interval (CI) using the random-effects model. Heterogeneity was assessed using the Cochrane Q-test and I2 statistics.

RESULTS

Through database searches, 955 articles were retrieved. After screening the titles and abstracts, 52 articles were screened in full text. Finally, 12 studies met the inclusion criteria. No significant differences in efficacy were observed between alternative antibiotics and carbapenems (composite outcome, RR, 0.96; 95 % CI, 0.63-1.49; I2 = 21 %; low certainty of evidence).

CONCLUSIONS

Alternative antibiotics had clinical efficacy similar to that of carbapenems for treating patients with cUTI caused by gram-negative uropathogens resistant to third-generation cephalosporins.

Private benefit of β-lactamase dictates selection dynamics of combination antibiotic treatment

β-lactam antibiotics have been prescribed for most bacterial infections since their discovery. However, resistance to β-lactams, mediated by β-lactamase (Bla) enzymes such as extended spectrum β-lactamases (ESBLs), has become widespread. Bla inhibitors can restore the efficacy of β-lactams against resistant bacteria, an approach which preserves existing antibiotics despite declining industry investment. However, the effects of combination treatment on selection for β-lactam resistance are not well understood. Bla production confers both private benefits for resistant cells and public benefits which faster-growing sensitive cells can also exploit. These benefits may be differentially impacted by Bla inhibitors, leading to non-intuitive selection dynamics. In this study, we demonstrate strain-to-strain variation in effective combination doses, with complex growth dynamics in mixed populations. Using modeling, we derive a criterion for the selection outcome of combination treatment, dependent on the burden and effective private benefit of Bla production. We then use engineered strains and natural isolates to show that strong private benefits of Bla are associated with increased selection for resistance. Finally, we demonstrate that this parameter can be coarsely estimated using high-throughput phenotyping of clonal populations. Our analysis shows that quantifying the phenotypic responses of bacteria to combination treatment can facilitate resistance-minimizing optimization of treatment.

Impact of an antimicrobial stewardship programme on antibiotic utilization and resistance burden in patients with acute leukaemia: an 11-year longitudinal cohort study using interrupted time-series analysis

BACKGROUND

Antimicrobial resistance (AMR), driven by inappropriate and overuse of antibiotics, poses a significant threat, especially to patients with acute leukaemia.

OBJECTIVES

To evaluate the impact of antimicrobial stewardship programmes (ASPs) on antibiotic use and analyse temporal changes in bloodstream infections (BSI) caused by AMR organisms.

METHODS

We performed a retrospective, interventional, longitudinal cohort study spanning an 11-year period. ASPs included optimizing antibiotic use, enhancing tracking and reporting systems and delineating leadership and accountability. A segmented regression model of interrupted time series was used to evaluate the trend of antibiotic consumption and BSI with AMR organisms after the interventions.

RESULTS

A total of 3296 BSI episodes with 454 419 days of therapy (DOT) from 7754 patients were obtained. ASPs were significantly associated with an immediate reduction [-70.03 DOT/1000 patient-days (PD), P = 0.036] and a decreasing trend (-11.65 DOT/1000 PD per quarter, P < 0.001) in overall antibiotic use. The increasing incidence of BSI with AMR before ASP intervention was notably curbed and revealed a decreasing trend (slope change: -0.06 BSI/1000 PD per quarter, P = 0.002). The decreasing trend was more significant for Enterobacterales: ciprofloxacin-resistant and ESBL-producing isolates showed a slope change of -0.06 BSI/1000 PD and -0.08 BSI/1000 PD per quarter, respectively (all P < 0.05). However, Pseudomonas aeruginosa BSI increased.

CONCLUSIONS

Multidimensional ASPs effectively reduced both the immediate and trends in overall antibiotic usage even in patients with acute leukaemia. Additionally, there was a notable decrease in the incidence of BSI caused by AMR organisms, particularly among Enterobacterales.

Navigating fluoroquinolone resistance in Gram-negative bacteria: a comprehensive evaluation

Since the introduction of quinolone and fluoroquinolone antibiotics to treat bacterial infections in the 1960s, there has been a pronounced increase in the number of bacterial species that have developed resistance to fluoroquinolone treatment. In 2017, the World Health Organization established a priority list of the most critical Gram-negative resistant pathogens. These included Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. In the last three decades, investigations into the mechanisms of fluoroquinolone resistance have revealed that mutations in the target enzymes of fluoroquinolones, DNA gyrase or topoisomerase IV, are the most prevalent mechanism conferring high levels of resistance. Alterations to porins and efflux pumps that facilitate fluoroquinolone permeation and extrusion across the bacterial cell membrane also contribute to the development of resistance. However, there is a growing observation of novel mutants with newer generations of fluoroquinolones, highlighting the need for novel treatments. Currently, steady progress has been made in the development of novel antimicrobial agents that target DNA gyrase or topoisomerase IV through different avenues than current fluoroquinolones to prevent target-mediated resistance. Therefore, an updated review of the current understanding of fluoroquinolone resistance within the literature is imperative to aid in future investigations.

Relationship between carbapenem use and major diagnostic category in curative care beds: Analysis of a 2020 Japanese national administrative database

Excessive carbapenem use has contributed to the spread of carbapenem-resistant bacteria. In response, Japan's revised National Action Plan on Antimicrobial Resistance (AMR) 2023-2027 set the goal of a 20 % reduction in carbapenem use. The aim of this study is to reveal the circumstances associated with carbapenem use in diagnosis procedure combination (DPC) community hospitals and fee-for-service hospitals, which account for the majority of the hospitals in Japan. We analyzed publicly available data from the Survey of Discharged Patients conducted by the Ministry of Health, Labour and Welfare in 2020. We used multiple regression analysis to identify the factors associated with carbapenem use in small- to medium-sized hospitals. Considerable carbapenem use was observed in small- to medium-sized hospitals. There was a large difference in carbapenem use among curative care beds in both DPC community hospitals and non-DPC hospitals. Linear regression models showed the significant association of several major diagnostic categories (MDCs) with carbapenem use. In particular, rates of MDC No.02 (eye) and 05 (circulatory system) were potentially associated with excessive or inappropriate carbapenem use. A notable and novel study finding was that there was a large difference in carbapenem consumption as the number of curative care beds increased in both DPC community hospitals and non-DPC hospitals. This may contribute to the identification of carbapenem overuse and toward achieving the goal of the National Action Plan on AMR 2023-2027. Furthermore, identifying factors associated with carbapenem use helps in understanding disease-specific prescribing practices and detecting potential overuse.

Evaluation of temocillin efficacy against KPC-2-producing Klebsiella pneumoniae isolates in a hollow-fibre infection model

BACKGROUND

Temocillin is an old antimicrobial that is resistant to hydrolysis by ESBLs but has variable activity against carbapenemase-producing Enterobacteriaceae. The current EUCAST susceptibility breakpoints for Enterobacterales are set at ≤16 mg/L (susceptible with increased exposure) based on a dose of 2 g q8h, but there is limited information on the efficacy of this dose against temocillin-susceptible carbapenemase-producing Klebsiella pneumoniae isolates.

OBJECTIVES

To evaluate the efficacy of this dose using a hollow-fibre infection model (HFIM) against six KPC-2-producing clinical isolates of K. pneumoniae.

METHODS

The isolates were characterized by WGS and temocillin susceptibility was determined using standard and high inoculum temocillin. Mutant frequencies were estimated and temocillin activity was tested in time-kill assays and in the HFIM. At standard conditions, three of the isolates were classified as susceptible (MIC ≤ 16 mg/L) and three as resistant (MIC > 16 mg/L). The HFIM was performed over 3 days to mimic human-like pharmacokinetics of 2 g q8h. Bacterial counts were performed by plating on Mueller-Hinton agar (MHA) and MHA containing 64 mg/L temocillin to detect resistant subpopulations.

RESULTS

All isolates showed a reduction in bacterial population of at least 3 log cfu/mL within the first 8 h of simulated treatment in the hollow-fibre assay. Regrowth was observed for the three resistant isolates and one of the susceptible ones. The MIC value for these isolates was higher by at least two dilutions compared with their initial values.

CONCLUSIONS

These data suggest that an optimized pharmacokinetic regimen may be of clinical interest for the treatment of KPC-2-producing K. pneumoniae susceptible to temocillin. These data showed activity of temocillin against KPC-2-producing K. pneumoniae susceptible to temocillin; however, a dose of 2g q8h administered over 30 min may be inadequate to prevent the emergence of resistant variants.

Efficacy of noncarbapenem therapy for the treatment of ceftriaxone-resistant Enterobacterales outside the urinary tract

Objective

To determine the safety of noncarbapenem versus carbapenem antibiotics for treatment of adults with documented infection caused by ceftriaxone-resistant infections outside the urinary tract.

Design

Retrospective cohort of adult patients with a documented infection caused by an extended-spectrum β-lactamase (ESBL)-producing organism isolated between January 2018 and October 2021.

Setting

An academic tertiary-care center.

Patients

Adult patients with a documented infection caused by an ESBL-producing organism outside the urinary tract.

Methods

The primary outcome was a composite of treatment failure defined as 30-day mortality, 30-day readmission, microbiological recurrence, and/or clinical worsening requiring antibiotic change. Secondary outcomes included differentiation of primary composite components and postantibiotic Clostridioides difficile infection (CDI).

Results

This study included 130 patients. The primary source of infections were bloodstream (67.7%) and caused by Escherichia coli (81.5%). Overall, 101 patients received carbapenem therapy and 29 received noncarbapenem therapy (NCT). NCT was comprised of mainly fluoroquinolones (18 of 29) followed by cefepime (7 of 29). Patients receiving NCT had shorter hospital stays (median, 7 days vs 9 days) and were more often discharged on antibiotics (79.3% vs 50.5%). We did not detect a significant difference in the primary composite outcome of treatment failure for carbapenem (23.8%) versus noncarbapenem treatment (24.2%; P = .967). Secondary outcomes included a numerically higher 30-day mortality rate in the noncarbapenem group compared to the carbapenem group: 4 (13.8%) of 29 versus 4 (3.9%) of 101. We did not detect a difference in rates of CDI.

Conclusion

Noncarbapenem therapy may play a role for certain patients with infections caused by ESBL-producing organisms.

Clinical Outcomes of Third-Generation Cephalosporin Definitive Therapy for Bloodstream Infections Due to Enterobacterales with Potential AmpC Induction: A Single-Center Retrospective Study

The recommended therapy for severe infections caused by AmpC-inducible Enterobacterales (AmpC-E) typically involves cefepime or carbapenems. In an era of emerging resistance to these antimicrobials, we aim to assess the impact of third-generation cephalosporins (3GCs) vs. alternative antibiotics on clinical outcomes in bloodstream infections (BSIs) due to AmpC-E. We retrospectively included hospitalized adult patients with BSIs caused by 3GC-susceptible AmpC-E between 2012 and 2022, comparing the outcomes of 3GC and non-3GC definitive therapies. The primary outcome was overall treatment failure (OTF), encompassing 90-day all-cause mortality, 90-day reinfection, and 90-day readmission. Secondary outcomes comprised components of the OTF, in-hospital all-cause mortality, and length-of-stay. Within a total cohort of 353 patients, OTF occurred in 46.5% and 41.5% in the 3GC- and non-3GC-therapy groups, respectively (p = 0.36). The 3GC-therapy group exhibited a longer length-of-stay (38 vs. 21 days, p = 0.0003) and higher in-hospital mortality (23.3% vs. 13.4%, p = 0.019). However, the 90-day mortality, 90-day reinfection, and 90-day readmission were comparable between the therapy groups. Subgroup analyses involving high-risk AmpC-E and 3GC vs. standard-of-care yielded similar conclusions. Overall, our findings suggest that 3GC definitive therapy may not result in poorer clinical outcomes for the treatment of BSIs caused by AmpC-E.

Do Pathogenic Escherichia coli Isolated from Gallus gallus in South Africa Carry Co-Resistance Toward Colistin and Carbapenem Antimicrobials?

Colistin and carbapenems are critically important antimicrobials often used as a last resort to manage multidrug-resistant bacterial infections in humans. With limited alternatives, resistance to these antimicrobials is of concern as organisms could potentially spread horizontally rendering treatments ineffective. The aim of this study was to investigate co-resistance to colistin and carbapenems among Escherichia coli isolated from poultry in South Africa. Forty-six E. coli strains obtained from clinical cases of breeder and broiler chickens were used. In addition to other antibiotics, all the isolates were tested against colistin and carbapenems using broth microdilution. Multiplex polymerase chain reactions were used to investigate the presence of colistin (mcr-1 to 5) and carbapenem (blaOXA-48, blaNDM-1, and blaVIM) resistance genes. Isolates exhibiting colistin resistance (>2 μg/mL) underwent a whole-genome sequencing analysis. Resistance to colistin (10.9%) and cefepime (6.5%) was noted with all colistin-resistant strains harboring the mcr-1 gene. None of the E. coli isolates were resistant to carbapenems nor carried the other resistant genes (mcr-2 to 5, blaOXA-48, blaNDM-1, and blaVIM). The mcr-1-positive strains belonged to sequence types ST117 and ST156 and carried virulence genes ompA, aslA, fdeC, fimH, iroN, iutA, tsh, pic, ast A and set 1A/1B. In conclusion, clinical E. coli strains from chickens in this study possessed mobile resistance genes for colistin and several other clinically relevant antimicrobials but not carbapenems. Additionally, they belonged to sequence types in addition to carrying virulence factors often associated with human extraintestinal pathogenic E. coli infections. Thus, the potential risk of transmitting these strains to humans cannot be underestimated especially if sick birds are dispatched into the thriving poorly regulated Cornish hen industry. The need for routine veterinary surveillance and monitoring of antimicrobial resistance, antimicrobial use and the importance of strengthening regulations guiding the informal poultry sector remains important.

Cefepime vs carbapenems for treating third-generation cephalosporin-resistant AmpC β-lactamase-hyperproducing Enterobacterales bloodstream infections: a multicenter retrospective study

OBJECTIVES

AmpC β-lactamase-hyperproducing Enterobacterales (ABLHE) bloodstream infections (BSI) are emerging and leading to therapeutic challenges worldwide. Prescriptions of carbapenems may lead to the emergence of resistance. This study aimed to compare cefepime with carbapenems for the treatment of third-generation cephalosporin-resistant ABLHE BSI.

METHODS

This retrospective multicenter study included patients with ABLHE BSI from two tertiary hospitals in France, between July 2017 and July 2022. Non-AmpC-producing Enterobacterales, extended-spectrum β-lactamase, and carbapenemase-producing Enterobacterales were excluded. Cefepime was prescribed only in case of minimal inhibitory concentration ≤1 mg/l. The primary outcome was 30-day in-hospital mortality from the date of index blood culture. Secondary outcomes were infection recurrence and treatment toxicity. An inverse probability of treatment weighting approach was used to balance the baseline characteristics between the two groups.

RESULTS

We analyzed 164 BSI, which included 77 in the cefepime group and 87 in the carbapenem group. In the weighted cohort, the 30-day mortality rates were similar between the cefepime group (23.3%) and the carbapenem group (19.6%) with a relative risk of 1.19 (95% confidence interval, 0.61-2.33 P = 0.614). No significant difference in recurrence or toxicity was found between the two groups.

CONCLUSION

This study adds evidence in favor of the use of cefepime for treating third-generation cephalosporin-resistant ABLHE BSI in case of minimal inhibitory concentration ≤ 1 mg/l, which could spare carbapenems.

Risk of relapse and readmission among hospitalized adults with carbapenem non-susceptible gram-negative infections

BACKGROUND

Infections caused by carbapenem-nonsusceptible gram-negative (C-NS) pathogens are associated with increased mortality and high treatment costs. Identification of potentially modifiable factors that may improve patient outcomes is important for better management of C-NS GN infections.

METHODS

This was a retrospective study of hospitalized adults with electronic health record evidence of complicated urinary tract infection (cUTI), bacterial pneumonia (BP), complicated intra-abdominal infection (cIAI), or bacteremia (BAC) due to C-NS GN organisms from January 2013 to March 2018. Treatment patterns and clinical characteristics during the index hospitalization were analyzed descriptively and stratified by infection site(s). The effect of patient characteristics on index infection relapse during the postdischarge period and on readmission with 30 days was modeled using logistic regression.

RESULTS

The study included 2,862 hospitalized patients with C-NS GN infections. Index infection sites were 38.4% cUTI ± BAC, 21.5% BP ± BAC, 18.7% cUTI + BP ± BAC, 14.7% any cIAI, and 6.7% BAC only. The majority of patients (83.6%) received an antibiotic during their index hospitalization; among these, the most common classes given were penicillins (52.9%), fluoroquinolones (50.7%), and carbapenems (38.9%). During the postdischarge period, 21.7% of patients had a relapse of the index infection and 63.9% of patients were readmitted to the hospital. Factors associated with increased adjusted odds ratio (OR) for relapse or readmission included Charlson comorbidity score of ≥3 relative to 0 (relapse: OR [95% CI] = 1.34 [1.01-1.76], p = .040; readmission: OR [95% CI] 1.92 [1.50-2.46], p < .001), preindex immunocompromised status (relapse: OR [95% CI] 1.37 [1.05-1.79], p = .019; readmission: OR [95% CI] = 1.60 [1.27-2.02], p < .001), and preindex carbapenem use (relapse: OR [95% CI] = 1.35 [1.07-1.72], p = .013; readmission: OR [95% CI] = 1.25 [1.00-1.57], p = .048).

CONCLUSIONS

Adverse postdischarge outcomes were common among hospitalized patients with C-NS GN infections and were significantly associated with previous carbapenem use and patient clinical characteristics such as higher comorbidity burden and immunocompromised status. Adoption of antimicrobial stewardship and consideration of individual patient risk factors in making treatment decisions may help improve clinical outcomes.

Efficacy of carbapenems versus alternative antimicrobials for treating complicated urinary tract infections caused by antimicrobial-resistant Gram-negative bacteria: protocol for a systematic review and meta-analysis

INTRODUCTION

Complicated urinary tract infections (cUTIs) are associated with poor prognosis. The widespread infection of multidrug-resistant Gram-negative uropathogens such as extended-spectrum beta-lactamase-producing bacteria has limited the efficacy of antibiotics used for treating cUTI. Considering the existence of antimicrobial-resistant (AMR) uropathogens, carbapenem is the last-resort antibiotic for cUTI. Given that carbapenem overuse has facilitated the spread of carbapenem-resistant Gram-negative bacteria, carbapenem dependence should be urgently reduced. However, improvement on the clinical outcomes of alternative antibiotics against cUTI caused by AMR uropathogens has not yet been systematically evaluated. Thus, this systematic review and meta-analysis aims to explore and compare the clinical outcomes of cUTI caused by AMR uropathogens between carbapenem and non-carbapenem antibiotics.

METHODS AND ANALYSIS

The study inclusion criteria will be considered based on the PICO model consisting the following elements: population-adult patients with cUTIs caused by Gram-negative uropathogens; intervention-non-carbapenem class of antimicrobial agents with in vitro activities against Gram-negative uropathogens; comparison-treatment of carbapenem class antibiotics; outcome-a clinical and microbiological cure. Relevant articles published until December 2022 will be systematically searched in February 2023, using electronic databases such as PubMed, the Cochrane Library, EMBASE and ClinicalTrials.gov. Two independent reviewers will screen the select literature and then assess the full-text article to meet the inclusion criteria. The risk of bias will be assessed using the Cochrane risk-of-bias assessment tool. The treatment effects of antibiotics will be estimated as a risk ratio with a 95% CI, using the random-effects model.

ETHICS AND DISSEMINATION

This protocol and systematic review will not include direct patient data; thus, informed consent will be waived. The results of this study will be published in an international peer-reviewed journal for wider information dissemination.

PROSPERO REGISTRATION NUMBER

CRD42022356064.

Antimicrobial Stewardship Program for Patients in the Hematological Department Receiving Carbapenem Therapy: A Single-Center and Interrupted Time Series Analysis

As antibiotic resistance has become a global problem, the intervention of an antimicrobial stewardship team (AST) is warranted. In hematological disorders, infectious complications are crucial owing to abnormal neutrophil function and decreased cell-mediated immunity. Despite the widespread implementation of AST intervention, the effectiveness of stewardship practices for immunocompromised patients remains uncertain. We determined the effect of AST interventions on carbapenem therapy in the department of hematology. Patients admitted to the department and undergoing carbapenem therapy were enrolled. We compared carbapenem use between the pre-AST (April 2016-March 2018) and post-AST (April 2018-March 2021) periods. Factors associated with long-term carbapenem therapy were investigated. Overall, 515 episodes of carbapenem therapy in 264 patients in the department were evaluated. According to the interrupted time series analysis, the number of days of therapy decreased with AST intervention (β = -0.263, p = 0.011). In multivariate analysis, predictive factors associated with long-term carbapenem therapy (>8 days) were outpatient onset, chronic obstructive pulmonary disease, acute myeloid leukemia, multiple myeloma, and infection with resistant bacteria (such as extended spectrum β-lactamases and AmpC) (95% confidence interval, 1.030-2.818, 1.067-66.667, 1.057-2.782, 0.168-0.742, and 1.382-5.750, respectively). The AST intervention reduced carbapenem use in patients with hematological disorders.

Evaluation and Analysis of the Rationality of Clinical Use of Carbapenems in Surgical Departments of a Tertiary Hospital in Southwest China

Purpose

With the increasing frequency and intensity of carbapenem consumption, carbapenem-resistant organisms (CRO) have become a focus of anti-infection research. This study aimed to evaluate the rationality of the clinical use of carbapenems among inpatients in the surgical departments of a tertiary hospital in southwest China.

Patients and methods

A point-score system was established for evaluation based on the clinical practices in surgical departments and selected carbapenem prescriptions from June 2020 to June 2021 for hepatobiliary surgery, gastrointestinal surgery, and neurosurgery in the study hospital. Prescriptions with a total score ≥ 270 were defined as rational. Descriptive statistics were used to describe the characteristics and rationality of the prescriptions. The chi-square test, Mann-Whitney U-test, and Kruskal-Wallis H-test were used to compare characteristics between rational and irrational prescriptions. Linear regression analysis was used to determine the factors affecting the rationality of carbapenem prescriptions.

Results

According to 192 carbapenem prescription records, the median age of patients was 62 years [IQR, 48.0-73.0], and 20% of patients had abdominal infections, 10% had lung infections, 14% had intracranial infections, and 3% had urinary tract infections. 56% of carbapenem prescriptions were irrational. Compared with rational carbapenem prescriptions, irrational prescriptions had a higher proportion of those with inappropriate indications (49% vs 0%, p < 0.05), incorrect variety selection (15% vs 0%, p<0.05), and unreasonable assessment of etiology and efficacy (46% vs 8%, p < 0.05). Linear regression analysis suggested that the diagnosis of cholecystitis (standardized regression coefficient=0.183, p<0.05) and replaced medication (standardized regression coefficient = 0.154, p<0.05) influenced the rationality of carbapenem prescriptions.

Conclusion

Our study shows that the irrational use of carbapenems deserves attention, especially in surgical departments. Interventions for carbapenem use that are based on evaluation criteria should be developed to reduce the emergence and spread of carbapenem-resistant bacteria.

Association between Carbapenem Consumption and Clinical Outcomes in an In-Hospital Setting: Analysis of a Japanese Nationwide Administrative Database in 2020

This study aimed to clarify the relationship between carbapenem consumption and clinical outcome using the diagnosis procedure combination (DPC) payment system database (2020) published by the Ministry of Health, Labour, and Welfare of Japan. This study divided 5316 medical facilities subject to aggregation into five facilities and calculated the median values, including facility characteristics, clinical outcomes, and carbapenem consumption. Next, a correlation analysis was performed between carbapenem consumption and clinical outcome, as well as a multiple regression analysis between carbapenem consumption as the dependent variable and clinical outcome, bed size, and proportion of patients by disease as independent variables. Additionally, three clinical outcomes available from the DPC payment system database were selected, including cure, readmission within 4 weeks, and the average length of stay. This study revealed no relationship between carbapenem consumption and clinical outcome in university hospitals and university hospital-equivalent community hospitals; however, a relationship was suggested in the community, DPC-prepared, and non-DPC hospitals. University hospitals and university hospital-equivalent community hospitals with a high consumption of carbapenems may need to reconsider the classification because of the limited number of facilities in this classification.

Criteria Restricting Inappropriate Meropenem Empiricism (CRIME): a quasi-experimental carbapenem restriction pilot at a large academic medical centre

The broad-spectrum activity of carbapenems makes them appealing for empirical use; however, they are associated with development of Clostridioides difficile infection (CDI) and multidrug resistance. Selective carbapenem use is vital in maintaining their effectiveness. We examined the impact of meropenem restriction criteria on utilisation and patient outcomes. This quasi-experimental study was conducted at a single academic medical centre after medication use evaluation found frequent inappropriate meropenem utilisation. Antimicrobial stewardship-led restriction criteria were developed and implemented in February 2022. Investigators aimed to determine how restriction criteria affected meropenem utilisation across 8 weeks in the pre- (February-April 2020) versus post-implementation period (February-April 2022). The primary outcome was inappropriateness of meropenem utilisation. Secondary outcomes included days of therapy per 1000 patient-days (DOT/1000 PD), hospital length of stay (LOS), CDI Standardized Infection Ratio (SIR), and acquisition cost. Across the 8-week timeframes, reductions in inappropriate meropenem use (64.5% vs. 12.8%; P < 0.001), duration of therapy [5.8 (3.2-7.3) vs. 2.4 (1.0-5.5) days; P < 0.001] and utilisation (30.5 vs. 8.3 DOT/1000 PD; P < 0.001) pre- versus post-implementation were observed. Total meropenem orders decreased by 65% (P < 0.001). Median hospital LOS also decreased between periods [11.9 (7.8-20.4) vs. 9.2 (5.4-15.2) days], although not statistically significant (P = 0.051). There was no difference in CDI SIR (0.1 vs. 0.1; P = 0.99). Projected annual cost savings were ∼US$57 300. Implementation of antimicrobial stewardship-initiated restriction criteria can reduce inappropriate meropenem utilisation, overall number of orders, and total duration of therapy.

Impact of Hospital Environmental Cleaning with a Potassium Peroxymonosulphate-Based Environmental Disinfectant and Antimicrobial Stewardship on the Reduction of Hospital-Onset Clostridioides difficile Infections

BACKGROUND

A 1% potassium peroxymonosulphate-based environmental disinfectant (PPED) produces sodium hypochlorite when combined with sodium chloride, which functions as a disinfectant. However, little is known about the impact of hospital cleaning with PPED on hospital-onset Clostridioides difficile infection (HO-CDI).

AIM

To reduce HO-CDI, we promote antimicrobial stewardship and hospital ward cleaning with PPED. This study was conducted to evaluate their impact.

METHODS

We began a promotion of post-prescription review with feedback for broad-spectrum antimicrobials and hospital ward cleaning with PPED. We reviewed the ratio of HO-CDI, PPED consumption, and days of therapy (DOT) of broad-spectrum antimicrobials between July 2014 and March 2018, dividing this time into the pre-promotion (July 2014 to June 2015) and post-promotion periods (July 2015 to March 2018).

FINDINGS

Using interrupted time series analysis, an immediate significant change in HO-CDI was observed after intervention (P = 0.03), although a downward trend was not observed over this period (P = 0.19). Trends in PPED consumption significantly changed over this period (P = 0.02). DOT of carbapenems decreased immediately after the intervention began (P < 0.01). A Poisson regression analysis showed that PPED consumption and DOT of carbapenems were independent factors affecting HO-CDI (P = 0.039 and 0.016, respectively).

CONCLUSION

We revealed that DOT of carbapenems and use of PPED were associated with the HO-CDI ratio and that both interventions reduced the rate of HO-CDI. This is the first report on the impact of hospital ward cleaning with PPED on the reduction of HO-CDI.

Comparative genomic analysis of ESBL-producing Escherichia coli from faecal carriage and febrile urinary tract infection in children: a prospective multicentre study

Background

The reliability of ESBL-producing Escherichia coli (ESBL-Ec) faecal carriage monitoring to guide probabilistic treatment of febrile urinary tract infection (FUTI) in children remains unclear.

Objectives

To compare the genomic characteristics of ESBL-Ec isolates from faecal carriage and FUTI to assess their correlation and identify a FUTI-associated virulence profile.

Methods

We conducted a prospective multicentre hospital and ambulatory-based study. We analysed the genotypes and virulence factors of both faecal and FUTI ESBL-Ec by whole genome sequencing. Correlations were assessed by non-parametric Spearman coefficient and virulence factors were assessed by chi-squared tests with Bonferroni correction.

Results

We included 218 ESBL-Ec causing FUTI and 154 ESBL-Ec faecal carriage isolates. The most frequent ST was ST131 (44%) in both collections. We found high correlation between carriage and ESBL-Ec FUTI regarding genes/alleles (rho = 0.88, P < 0.0001) and combinations of virulence genes, MLST and serotypes (rho = 0.90, P < 0.0001, rho = 0.99, P = 0.0003, rho = 0.97, P = 0.005 respectively). Beside this strong correlation, we found five genes that were significantly associated with FUTI (papC, papGII, hlyC, hek and traJ). The strongest association with FUTI was found with adhesin gene allele papGII (54% in FUTI versus 16% in carriage) and for papGII and gene traJ alone or in combination (63% versus 24%).

Conclusions

The genomic profile of ESBL-Ec causing FUTI in children strongly correlates with faecal carriage isolates except for a few genes. The presence of papGII and/or traJ in a previously identified carriage strain could be used as a marker of uropathogenicity and may guide the empirical antimicrobial choice in subsequent FUTI.

The impact of public health interventions on the future prevalence of ESBL-producing Klebsiella pneumoniae: a population based mathematical modelling study

Background

Future prevalence of colonization with extended-spectrum betalactamase (ESBL-) producing K. pneumoniae in humans and the potential of public health interventions against the spread of these resistant bacteria remain uncertain.

Methods

Based on antimicrobial consumption and susceptibility data recorded during > 13 years in a Swiss region, we developed a mathematical model to assess the comparative effect of different interventions on the prevalence of colonization.

Results

Simulated prevalence stabilized in the near future when rates of antimicrobial consumption and in-hospital transmission were assumed to remain stable (2025 prevalence: 6.8% (95CI%:5.4–8.8%) in hospitals, 3.5% (2.5–5.0%) in the community versus 6.1% (5.0–7.5%) and 3.2% (2.3–4.2%) in 2019, respectively). When overall antimicrobial consumption was set to decrease by 50%, 2025 prevalence declined by 75% in hospitals and by 64% in the community. A 50% decline in in-hospital transmission rate led to a reduction in 2025 prevalence of 31% in hospitals and no reduction in the community. The best model fit estimated that 49% (6–100%) of observed colonizations could be attributable to sources other than human-to-human transmission within the geographical setting.

Conclusions

Projections suggests that overall antimicrobial consumption will be, by far, the most powerful driver of prevalence and that a large fraction of colonizations could be attributed to non-local transmissions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07441-z.

Piperacillin/tazobactam-resistant, cephalosporin-susceptible Escherichia coli bloodstream infections are driven by multiple acquisition of resistance across diverse sequence types

Resistance to piperacillin/tazobactam (TZP) in Escherichia coli has predominantly been associated with mechanisms that confer resistance to third-generation cephalosporins. Recent reports have identified E. coli strains with phenotypic resistance to piperacillin/tazobactam but susceptibility to third-generation cephalosporins (TZP-R/3GC-S). In this study we sought to determine the genetic diversity of this phenotype in E. coli (n=58) isolated between 2014–2017 at a single tertiary hospital in Liverpool, UK, as well as the associated resistance mechanisms. We compare our findings to a UK-wide collection of invasive E. coli isolates (n=1509) with publicly available phenotypic and genotypic data. These data sets included the TZP-R/3GC-S phenotype (n=68), and piperacillin/tazobactam and third-generation cephalosporin-susceptible (TZP-S/3GC-S, n=1271) phenotypes. The TZP-R/3GC-S phenotype was displayed in a broad range of sequence types, which was mirrored in the same phenotype from the UK-wide collection, and the overall diversity of invasive E. coli isolates. The TZP-R/3GC-S isolates contained a diverse range of plasmids, indicating multiple acquisition events of TZP resistance mechanisms rather than clonal expansion of a particular plasmid or sequence type. The putative resistance mechanisms were equally diverse, including hyperproduction of TEM-1, either via strong promoters or gene amplification, carriage of inhibitor-resistant β-lactamases, and an S133G bla_CTX-M-15 mutation detected for the first time in clinical isolates. Several of these mechanisms were present at a lower abundance in the TZP-S/3GC-S isolates from the UK-wide collection, but without the associated phenotypic resistance to TZP. Eleven (19%) of the isolates had no putative mechanism identified from the genomic data. Our findings highlight the complexity of this cryptic phenotype and the need for continued phenotypic monitoring, as well as further investigation to improve detection and prediction of the TZP-R/3GC-S phenotype from genomic data.

Evaluation of Carbapenem Use Before and After Implementation of an Antimicrobial Stewardship-Led Carbapenem-Sparing Strategy in a Lebanese Tertiary Hospital: A Retrospective Study

Purpose

The use of carbapenem before and after implementation of an antimicrobial stewardship-led carbapenem-sparing strategy at a tertiary care center in Lebanon was evaluated.

Methods

A retrospective, observational chart review was performed on all hospitalized pediatric and adult patients who received carbapenem therapy during January 2019 and January 2020. Patients who started their regimen before January or received carbapenems for less than 24 hours were excluded. Primary outcomes included the appropriateness of physician prescribing patterns and pharmacists’ interventions, as well as appropriateness and response rates of the latter. Secondary outcomes included the carbapenem defined daily dose (DDD) and days of therapy (DOT). Descriptive statistics were used in the analysis and a p-value < 0.05 was considered to be statistically significant.

Results

A total of 157 and 150 patients charts were reviewed in January 2019 and January 2020, respectively. There was no difference in baseline characteristics except for inpatient services and rates of isolated multidrug-resistant organisms. When comparing the two timelines, the appropriateness of physicians’ prescribing patterns increased in terms of empirical therapy, targeted therapy, and duration of therapy but the results were not statistically significant. Pharmacists’ interventions significantly increased with regards to the duration of therapy (p= <0.001), dose adjustment (p<0.001), de-escalation to a narrower spectrum antibiotic (p=0.007), and use of extended infusion (p=0.042). The DDD and DOT were higher for ertapenem and lower for anti-pseudomonal carbapenems in January 2020.

Conclusion

The carbapenem-sparing strategy adopted by the antimicrobial stewardship program contributed to an increase in the number of interventions made by pharmacists on carbapenem therapy, including their appropriateness, and response rate. Despite an improvement in the physician-prescribing patterns, more awareness and education may be needed to achieve a better impact.

Comparison of Antibiotic Use between the First Two Waves of COVID-19 in an Intensive Care Unit at a London Tertiary Centre: reducing broad-spectrum antimicrobial use did not adversely affect mortality

BACKGROUND

The COVID-19 pandemic increased the use of broad-spectrum antibiotics due to diagnostic uncertainty, particularly in critical care. Multiprofessional communication became more difficult, weakening stewardship activities.

AIM

To determine changes in bacterial co-/secondary infections and antibiotics used in COVID-19 patients in critical care, and mortality rates, between the first and second waves.

METHODS

Prospective audit comparing bacterial co-/secondary infections and their treatment during the first two waves of the pandemic in a single centre teaching hospital ICU. Data on demographics, daily antibiotic use, clinical outcomes, and culture results in patients diagnosed with COVID-19 infection were collected over 11 months.

FINDINGS

From 9/3/20 to 2/9/20 (Wave 1), there were 156 patients and between 3/9/20 and 1/2/21 (Wave 2) there were 235 patients with COVID-19 infection admitted to intensive care. No significant difference was seen in mortality or positive blood culture rates between the two waves. The proportion of patients receiving antimicrobial therapy (93.0% vs 81.7%; p<0.01), and the duration of meropenem use (median (interquartile range): 5 (2-7) vs 3 (2-5) days; p=0.01) was lower in Wave 2. However, the number of patients with respiratory isolates of Pseudomonas aeruginosa (4/156 vs 21/235; p<0.01) and bacteraemia from a respiratory source (3/156 vs 20/235 p<0.01) increased in Wave 2, associated with an outbreak of infection. There was no significant difference between waves with respect to isolation of other pathogens.

CONCLUSIONS

Reduced broad spectrum antimicrobial use in the second wave of COVID-19 compared with the first wave was not associated with significant change in mortality.

Severe secondary peritonitis: impact of inappropriate initial antimicrobial therapy on prognosis and potential carbapenem-sparing

BACKGROUND

Initiation of antimicrobial therapy (IAT) with broad-spectrum antibiotics is usual in Intensive Care Unit (ICU) patients with secondary peritonitis. Carbapenems are widely proposed by recent guidelines contrasting with current antibiotic stewardship policies of carbapenem-sparing. However, prognosis of inappropriate IAT remains unclear in these patients and broad-spectrum antibiotics are probably overused. We aimed to assess the role of inappropriate IAT in ICU patients with secondary peritonitis and the use of carbapenems in our IAT regimens.

METHODS

We performed a retrospective analysis during a six-year period including 131 ICU patients with secondary peritonitis. We collected data concerning comorbidities, source and severity of peritonitis, management of IAT, peritoneal samples and outcome.

RESULTS

Forty-one patients presented with community acquired peritonitis (CAP) and 90 with postoperative peritonitis (POP). Thirty-seven (28.2%) patients died during ICU stay. IAT was inappropriate in 35 (26.7%) patients. Inappropriate IAT was not associated with reduced survival with respectively 26 (27%) deaths when IAT was adequate and 11 (31.4%) deaths when IAT was inadequate (P=0.87). Inappropriate IAT was not associated with the need of re-operation and duration of ICU stay. Carbapenems were delivered in 29 patients but were only necessary for eight patients without alternative treatment.

CONCLUSIONS

In our study, inappropriate IAT was not associated with a worse prognosis and carbapenems were overused. Extensive delivery of carbapenems proposed by recent guidelines could be reconsidered in the management of these patients.

[A Study of Outcome Measures and Establishment of Benchmarks for Antimicrobial Stewardship Programs]

Over the past few decades, the effectiveness of antibiotics has been diminished owing to the emergence of antimicrobial resistance resulting from the overuse of antibiotics. Antimicrobial stewardship aims to improve the appropriateness of antibiotic use to reduce antimicrobial resistance and benefit patients. Antimicrobial stewardship requires structural prerequisites for implementing antimicrobial stewardship programs (ASPs), such as the presence of a multidisciplinary antimicrobial stewardship team (AST), to ensure appropriate antimicrobial use at healthcare facilities. However, manpower shortage for ASTs in most Japanese hospitals has resulted in limited implementation of ASPs. Our study provided a directive for promotion of comprehensive ASPs including various outcome measures. Our findings would provide useful benchmarks for hospitals planning to implement ASPs in Japan as well as around the world. This review provides a framework for evaluating the outcome measures and benchmarks of ASPs based on our study.

Sigmoid Emax Modeling To Define the Fixed Concentration of Enmetazobactam for MIC Testing in Combination with Cefepime

The use of carbapenem antibiotics to treat infections caused by Enterobacterales expressing increasingly aggressive extended-spectrum β-lactamases (ESBLs) has contributed to the emergence of carbapenem resistance. Enmetazobactam is a novel ESBL inhibitor being developed in combination with cefepime as a carbapenem-sparing option for infections caused by ESBL-producing Enterobacterales. Cefepime-enmetazobactam checkerboard MIC profiles were obtained for a challenge panel of cefepime-resistant ESBL-producing clinical isolates of Klebsiella pneumoniae. Sigmoid maximum effect (E_max) modeling described cefepime MICs as a function of enmetazobactam concentration with no bias. A concentration of 8 μg/ml enmetazobactam proved sufficient to restore >95% of cefepime antibacterial activity in vitro against >95% of isolates tested. These results support a fixed concentration of 8 μg/ml of enmetazobactam for MIC testing.

Evaluating and Mitigating Risk of Acute Kidney Injury with the Combination of Vancomycin and Piperacillin-Tazobactam in Children

The antibiotic combination of vancomycin (VAN) and piperacillin-tazobactam (PTZ) has been associated with an increased risk of acute kidney injury (AKI) in both adult and pediatric patients. In this review, we highlight some of the limitations of existing pediatric studies evaluating the combination of VAN/PTZ, focusing on AKI risk in specific pediatric patient populations. We also review the variability in defining AKI in children and provide guidance to clinicians for use of prospective surveillance and stewardship in mitigating the risk of AKI in pediatric patients treated with combination of VAN/PTZ. Based on review of available pediatric studies, if the combination of VAN/PTZ is selected as an empirical antibiotic combination, it should be used in those at low risk for AKI and should be used with extreme caution in patients with additional nephrotoxic risks. Systems should be in place to monitor the use of VAN/PTZ and associated renal function in those receiving this antibiotic combination.

Multispecies Outbreak of Verona Integron-Encoded Metallo-ß-Lactamase-Producing Multidrug Resistant Bacteria Driven by a Promiscuous Incompatibility Group A/C2 Plasmid

BACKGROUND

Antibiotic resistance is often spread through bacterial populations via conjugative plasmids. However, plasmid transfer is not well recognized in clinical settings because of technical limitations, and health care-associated infections are usually caused by clonal transmission of a single pathogen. In 2015, multiple species of carbapenem-resistant Enterobacteriaceae (CRE), all producing a rare carbapenemase, were identified among patients in an intensive care unit. This observation suggested a large, previously unrecognized plasmid transmission chain and prompted our investigation.

METHODS

Electronic medical record reviews, infection control observations, and environmental sampling completed the epidemiologic outbreak investigation. A laboratory analysis, conducted on patient and environmental isolates, included long-read whole-genome sequencing to fully elucidate plasmid DNA structures. Bioinformatics analyses were applied to infer plasmid transmission chains and results were subsequently confirmed using plasmid conjugation experiments.

RESULTS

We identified 14 Verona integron-encoded metallo-ß-lactamase (VIM)-producing CRE in 12 patients, and 1 additional isolate was obtained from a patient room sink drain. Whole-genome sequencing identified the horizontal transfer of blaVIM-1, a rare carbapenem resistance mechanism in the United States, via a promiscuous incompatibility group A/C2 plasmid that spread among 5 bacterial species isolated from patients and the environment.

CONCLUSIONS

This investigation represents the largest known outbreak of VIM-producing CRE in the United States to date, which comprises numerous bacterial species and strains. We present evidence of in-hospital plasmid transmission, as well as environmental contamination. Our findings demonstrate the potential for 2 types of hospital-acquired infection outbreaks: those due to clonal expansion and those due to the spread of conjugative plasmids encoding antibiotic resistance across species.

Impact of a Telehealth-Based Antimicrobial Stewardship Program in a Community Hospital Health System

BACKGROUND

Data on antimicrobial stewardship programs (ASPs) facilitated via telehealth in the community hospital setting are limited.

METHODS

A telehealth-based ASP was implemented in 2 community hospitals (285 and 176 beds). Local pharmacists without residency or prior antimicrobial stewardship training were trained to conduct prospective audit and feedback. For approximately 60 minutes 3 times weekly at the 285-bed hospital and 2 times weekly at the 176-bed hospital, infectious diseases (ID) physicians remotely reviewed patients on broad-spectrum antibiotics and those admitted with lower respiratory tract infections and skin and soft tissue infections with local pharmacists. Recommendations for ASP interventions made by ID physicians were relayed to primary teams and tracked by local pharmacists. Antimicrobial utilization was collected in days of therapy (DOT) per 1000 patient-days (PD) for a 12-month baseline and 6-month intervention period, and analyzed with segmented linear regression analysis. Local ID consultations were tracked and antimicrobial cost savings were estimated.

RESULTS

During the 6-month intervention period, 1419 recommendations were made, of which 1262 (88.9%) were accepted. Compared to the baseline period, broad-spectrum antibiotic utilization decreased by 24.4% (342.1 vs 258.7 DOT/1000 PD; P < .001) during the intervention period. ID consultations increased by 40.2% (15.4 consultations per 1000 PD vs 21.5 consultations per 1000 PD; P = .001). Estimated annualized savings on antimicrobial expenditures were $142 629.83.

CONCLUSIONS

An intense ASP model, facilitated in the community hospital setting via telehealth, led to reduced broad-spectrum antimicrobial utilization, increased ID consultations, and reduced antimicrobial expenditures.

Detection of mobile colistin-resistance gene variants (mcr-1 and mcr-2) in urinary tract pathogens in Bangladesh: the last resort of infectious disease management colistin efficacy is under threat

Background: Currently, colistin-resistant pathogens emerged has become a global health concern. This study assessed the distribution of mcr-1 to mcr-5 variants with the phenotypic colistin-resistance in bacterial isolates from urinary tract infection (UTI) patients in Bangladesh.Methods: A cross-sectional study was conducted between April 2017 and March 2018 to enroll uncomplicated UTI patients, and 142 urine samples were analyzed. Uropathogens were identified using the API-20E biochemical panel and 16s rRNA gene sequencing. Polymerase chain reactions detected the mcr gene variants in the UTI isolates. The phenotypic colistin-susceptibility was determined by the Kirby-Bauer disc-diffusion method and the minimal inhibitory concentration (MIC) measurement.Results: The combined carriage of mcr-1 and mcr-2 genes in 11.4% (14/123) of urinary tract pathogens. The mcr-positive pathogens include five Escherichia coli, three Klebsiella pneumoniae, three Pseudomonas putida, two Enterobacter cloacae, and one Enterobacter hormaechei. The mcr-positive variant showed significantly higher phenotypic colistin resistance with MIC between >16 µg/mL and >128 µg/mL (p< 0.001). Over 85% of colistin-resistant isolates showed MDR phenomena.Conclusions: The emergence of the clinical MDR pathogens with resistance to a highly selective drug may lead to a lack of treatment options for the infectious diseases and spread of infection to the unaffected cohorts.

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.

In Vivo Activity of WCK 4282 (High-Dose Cefepime/Tazobactam) against Serine-β-Lactamase-Producing Enterobacterales and Pseudomonas aeruginosa in the Neutropenic Murine Lung Infection Model

WCK 4282 (cefepime 2 g-tazobactam 2 g) maximizes systemic exposure of tazobactam and restores cefepime activity against various extended-spectrum β-lactamase (ESBL)- and cephalosporinase-producing strains in vitro We describe clinical WCK 4282 exposure efficacies against various serine β-lactamase-producing Enterobacterales and Pseudomonas aeruginosa isolates in a murine pneumonia model. Clinical cefepime-resistant isolates (17 Enterobacterales and 2 P. aeruginosa) were utilized. Isolates expressed ESBLs, cephalosporinases, and/or serine carbapenemases (KPC and OXA-48-like). WCK 4282 MICs were 4 to 32 μg/ml. For in vivo experiments, lungs of neutropenic mice were inoculated using standard inoculum (10⁷ log₁₀ CFU/ml). Serine carbapenemase-producing isolates were also assessed using a low inoculum (1:5 dilution). Treatment mice received a human-simulated regimen (HSR) of cefepime, meropenem (control for serine carbapenemase expression with low inoculum experiments), or WCK 4282 human-simulated regimens. Efficacy was assessed as change in log₁₀ CFU/lungs at 24 h compared with 0-h controls. At standard inoculum, the mean 0-h bacterial burden was 6.65 ± 0.23 log₁₀ CFU/lungs, and it increased at 24 h by 2.48 ± 0.60 log₁₀ CFU/lungs among untreated controls. Initial bacterial burdens of lower inocula ranged from 5.81 ± 0.12 to 6.39 ± 0.13 log₁₀ CFU/lungs. At standard and/or low inocula, cefepime and meropenem provided minimal activity. WCK 4282 produced a >1 log₁₀ reduction against 9/9 ESBL-/cephalosporinase-producing strains. WCK 4282 provided variable activity among mice infected with standard or lower inocula of OXA-48-like-producers. WCK 4282 exposures provided 0.53 ± 1.07 log₁₀ CFU/lungs growth against KPC producers at a standard inoculum versus bacteriostasis (-0.15 ± 0.54 change in log₁₀ CFU/lungs) at a low inoculum. WCK 4282 produced potent in vivo activity against ESBL- and cephalosporinase-producing Enterobacterales and P. aeruginosa isolates and potential activity against OXA-48-like-producing Enterobacterales isolates in a neutropenic pneumonia model.

Risk factors for carbapenem-resistant Gram-negative bacterial infections: a systematic review

BACKGROUND

Rapid and widespread increases in carbapenem resistance (CR) necessitate identification of risk factors to guide appropriate interventions.

OBJECTIVES

We aimed to identify risk factors for CR Gram-negative infection through a systematic literature review.

DATA SOURCES

We searched MEDLINE (via OvidSP and PubMed) and Embase (via OvidSP) databases and the Cochrane Central Register of Controlled Trials.

STUDY ELIGIBILITY CRITERIA

Prospective or retrospective cohort and case-control studies reporting quantitative data on risk factors associated with infections due to CR Gram-negative pathogens in hospitalized patients were eligible.

PARTICIPANTS

Studies included hospitalized patients with CR infection caused by Gram-negative bacterial pathogens (Enterobacterales and non-fermenters).

METHODS

Searches were conducted in January 2018/December 2019 to identify studies published since 2007. Risk factor data were extracted and grouped by factor. The primary metric was proportion of studies reporting a significant association with CR infection for each factor.

RESULTS

In total, 92 studies were identified. Risk factors most frequently reported as significantly associated with CR infection (>10 studies) were previous antibiotic use (91.1%; 72/79 studies); previous carbapenem use (82.6%; 57/69); previous colonization (72.7%; 8/11); mechanical ventilation (66.7%; 36/54); previous intensive care unit stay (64.4%; 38/59); dialysis (61.1%; 11/18); catheter (58.0%; 40/69); length of stay in hospital (54.5%; 30/55); comorbidities (52.7%; 39/74); APACHE II (51.7%; 15/29); and intubation (51.4%; 18/35). Risk factors were mostly consistent across different species and sites of infection.

CONCLUSIONS

Several variables, particularly previous antibiotic use, are strong risk factors for CR infection. Interventions to mitigate against CR infection should target these factors.

KPC-2 β-lactamase enables carbapenem antibiotic resistance through fast deacylation of the covalent intermediate

Serine active-site β-lactamases hydrolyze β-lactam antibiotics through the formation of a covalent acyl-enzyme intermediate followed by deacylation via an activated water molecule. Carbapenem antibiotics are poorly hydrolyzed by most β-lactamases owing to slow hydrolysis of the acyl-enzyme intermediate. However, the emergence of the KPC-2 carbapenemase has resulted in widespread resistance to these drugs, suggesting it operates more efficiently. Here, we investigated the unusual features of KPC-2 that enable this resistance. We show that KPC-2 has a 20,000-fold increased deacylation rate compared with the common TEM-1 β-lactamase. Furthermore, kinetic analysis of active site alanine mutants indicates that carbapenem hydrolysis is a concerted effort involving multiple residues. Substitution of Asn170 greatly decreases the deacylation rate, but this residue is conserved in both KPC-2 and non-carbapenemase β-lactamases, suggesting it promotes carbapenem hydrolysis only in the context of KPC-2. X-ray structure determination of the N170A enzyme in complex with hydrolyzed imipenem suggests Asn170 may prevent the inactivation of the deacylating water by the 6α-hydroxyethyl substituent of carbapenems. In addition, the Thr235 residue, which interacts with the C3 carboxylate of carbapenems, also contributes strongly to the deacylation reaction. In contrast, mutation of the Arg220 and Thr237 residues decreases the acylation rate and, paradoxically, improves binding affinity for carbapenems. Thus, the role of these residues may be ground state destabilization of the enzyme-substrate complex or, alternatively, to ensure proper alignment of the substrate with key catalytic residues to facilitate acylation. These findings suggest modifications of the carbapenem scaffold to avoid hydrolysis by KPC-2 β-lactamase.

Evaluating the appropriateness of carbapenem and piperacillin-tazobactam prescribing in a tertiary care hospital in Saudi Arabia

Background

Antimicrobial resistance (AMR) is presently considered an emergent major global public health concern and excessive and/or inappropriate use of broad-spectrum antimicrobials contribute to the development of AMR.

Objective

To evaluate the appropriateness of carbapenems and piperacillin-tazobactam use in a tertiary care hospital.

Methods

A retrospective, observational, cross-sectional, drug-utilization study was conducted. The study included all adult hospitalized patients who had received at least one dose of the antimicrobials during their admission for the period between 1 January 2016 and 31 December 2017. The appropriateness of antimicrobial therapy was evaluated according to the Infectious Diseases Society of America (IDSA) guidelines with the consideration of the institutional antibiogram.

Results

Overall, 2731 patients received 5005 courses with one of the antimicrobials, for a total of 5045.9 defined daily doses (DDD) of imipenem-cilastatin, 6492.3 of meropenem and 15,595 of piperacillin-tazobactam (4.93, 6.34 and 15.24 DDD/100 bed days, respectively). The mean age of the patients who received either antimicrobial was 55.5 ± 20.3 years, with a 14-day average length of hospital stay. About half (52%) of the prescriptions were written for patients treated in the medical ward. Pneumonia (26.6%) and sepsis (24.9%) were the most common indication for the initiation of antimicrobial therapy. Of the assessed prescriptions, only 2787 (56.5%) were prescribed appropriately, with 2142 (43.5%) deemed inappropriate. The three most common reasons for inappropriate prescription were: the spectrum of activity was too broad (44.6%), followed by antimicrobial use without culture request (32.4%), and failure of suitable antimicrobial de-escalation (19.9%).

Conclusions

The study indicates that the overall rate of inappropriateness was high, emphasizing the need to develop initiatives to effectively improve broad-spectrum antimicrobial prescribing.

Post-Prescription Review with Threat of Infectious Disease Consultation and Sustained Reduction in Meropenem Use Over Four Years

BACKGROUND

Following a meropenem shortage, we implemented a post-prescription review with feedback (PPRF) in November 2015 with mandatory infectious disease (ID) consultation for all meropenem and imipenem courses > 72 hours. Providers were made aware of the policy via an electronic alert at the time of ordering.

METHODS

A retrospective study was conducted at the University of Washington Medical Center (UWMC) and Harborview Medical Center (HMC) to evaluate the impact of the policy on antimicrobial consumption and clinical outcomes pre- and post-intervention during a 6-year period. Antimicrobial use was tracked using days of therapy (DOT) per 1,000 patient-days, and data were analyzed by an interrupted time series.

RESULTS

There were 4,066 and 2,552 patients in the pre- and post-intervention periods, respectively. Meropenem and imipenem use remained steady until the intervention, when a marked reduction in DOT/1,000 patient-days occurred at both hospitals (UWMC: percentage change -72.1%, (95% CI -76.6, -66.9), P & 0.001; HMC: percentage change -43.6%, (95% CI -59.9, -20.7), P = 0.001). Notably, although the intervention did not address antibiotic use until 72 hours after initiation, there was a significant decline in meropenem and imipenem initiation ("first starts") in the post-intervention period, with a 64.9% reduction (95% CI 58.7, 70.2; P &0.001) at UWMC and 44.7% reduction (95% CI 28.1, 57.4; P & 0.001) at HMC.

CONCLUSIONS

Mandatory ID consultation and PPRF for meropenem and imipenem beyond 72 hours resulted in a significant and sustained reduction in the use of these antibiotics and notably impacted their up-front usage.

Carbapenem-sparing strategy: carbapenemase, treatment, and stewardship

PURPOSE OF REVIEW

describing the current role of carbapenems and carbapenem-sparing strategies in the setting of antimicrobial stewardship programs.

RECENT FINDINGS

sparing carbapenems with other drugs appears to be an interesting perspective for a variety of reasons in the current context of the multidrug-resistant (MDR) pandemic. Specific algorithms should also be precisely investigated to define better how to spare carbapenems within empiric and targeted regimens, with combination treatment or monotherapies, aiming at the best use of the new drugs and improving de-escalation as soon as possible for most of the patients.

SUMMARY

stewardship programs may be useful in reducing probable misuse and overuse of antibiotics, which has probably contributed to the emergence of carbapenem-resistant bacteria worldwide. The proposal of carbapenem-sparing strategies has then generated substantial scientific debate and, overall, the concept of sparing these drugs is well advocated together with judicious use of novel drugs, appropriate measures of infection control and prevention as well as in stewardship programs to curb the spread of MDR and XDR-strains in healthcare facilities.

Gut microbiome signatures of nursing home residents carrying Enterobacteria producing extended-spectrum β-lactamases

BACKGROUND

The prevalence of extended beta-lactamase producing Enterobacteriaceae (ESBL-E) has been constantly increasing over the last few decades. These microorganisms that have acquired broad antibiotic resistance are now common human pathogens. Changes in the gut microbiome, induced by antibiotics or other drugs, enable expansion of these microorganisms, but the mechanisms are not yet fully understood.

OBJECTIVES

The main objective was to identify specific bacteria and functional pathways and genes characterizing the gut microbiome of nursing home residents carrying ESBL-E, using metagenomics.

SUBJECTS AND METHODS

We included 144 residents living in two different nursing homes. All fecal samples were screened for ESBL-E and gut microbiome was characterized using shallow shotgun metagenomic DNA sequencing.

RESULTS

Ten nursing home residents were colonized by ESBL-E, namely Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae species, and were compared to non-carriers. We found that ESBL-E carriers had an alteration in within-sample diversity. Using a bootstrap algorithm, we found that the gut microbiome of ESBL-E carriers was depleted in butyrate-producing species, enriched in succinate-producing species and enriched in pathways involved in intracellular pH homeostasis compared to non-carriers individuals. Several energy metabolism pathways were overrepresented in ESBL-E carriers suggesting a greater ability to metabolize multiple microbiota and mucus layer-derived nutrients.

CONCLUSIONS

The gut microbiome of ESBL-E carriers in nursing homes harbors specific taxonomic and functional characteristics, conferring an environment that enables Enterobacteriaceae expansion. Here we describe new functional features associated with ESBL-E carriage that could help us to elucidate the complex interactions leading to colonization persistence in the human gut microbiota.

Multidrug Resistance (MDR) and Collateral Sensitivity in Bacteria, with Special Attention to Genetic and Evolutionary Aspects and to the Perspectives of Antimicrobial Peptides-A Review

Antibiotic poly-resistance (multidrug-, extreme-, and pan-drug resistance) is controlled by adaptive evolution. Darwinian and Lamarckian interpretations of resistance evolution are discussed. Arguments for, and against, pessimistic forecasts on a fatal “post-antibiotic era” are evaluated. In commensal niches, the appearance of a new antibiotic resistance often reduces fitness, but compensatory mutations may counteract this tendency. The appearance of new antibiotic resistance is frequently accompanied by a collateral sensitivity to other resistances. Organisms with an expanding open pan-genome, such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, can withstand an increased number of resistances by exploiting their evolutionary plasticity and disseminating clonally or poly-clonally. Multidrug-resistant pathogen clones can become predominant under antibiotic stress conditions but, under the influence of negative frequency-dependent selection, are prevented from rising to dominance in a population in a commensal niche. Antimicrobial peptides have a great potential to combat multidrug resistance, since antibiotic-resistant bacteria have shown a high frequency of collateral sensitivity to antimicrobial peptides. In addition, the mobility patterns of antibiotic resistance, and antimicrobial peptide resistance, genes are completely different. The integron trade in commensal niches is fortunately limited by the species-specificity of resistance genes. Hence, we theorize that the suggested post-antibiotic era has not yet come, and indeed might never come.

Optimal Management of Complicated Infections in the Pediatric Patient: The Role and Utility of Ceftazidime/Avibactam

Antimicrobial resistance poses a substantial threat to global public health. The pursuit of new antibiotics has decreased and very few options have been investigated for the treatment of complicated multidrug-resistant Gram-negative (MDR-GN) infections in adult population and even less in pediatric patients. Ceftazidime-avibactam (CAZ-AVI) is novel cephalosporin/β-lactamase inhibitor (BL-BLI) combination with broad antibacterial spectrum. The aim of this review is to describe the current and future role CAZ-AVI in the pediatric population with suspected or confirmed MDR-GN infections.

Pharmacokinetics-Pharmacodynamics of Enmetazobactam Combined with Cefepime in a Neutropenic Murine Thigh Infection Model

Third-generation cephalosporin (3GC)-resistant Enterobacteriaceae are classified as critical priority pathogens, with extended-spectrum β-lactamases (ESBLs) as principal resistance determinants. Enmetazobactam (formerly AAI101) is a novel ESBL inhibitor developed in combination with cefepime for empirical treatment of serious Gram-negative infections in settings where ESBLs are prevalent. Cefepime-enmetazobactam has been investigated in a phase 3 trial in patients with complicated urinary tract infections or acute pyelonephritis. This study examined pharmacokinetic-pharmacodynamic (PK-PD) relationships of enmetazobactam, in combination with cefepime, for ESBL-producing isolates of Klebsiella pneumoniae in 26-h murine neutropenic thigh infection models. Enmetazobactam dose fractionation identified the time above a free threshold concentration (fT > C_T ) as the PK-PD index predictive of efficacy. Nine ESBL-producing isolates of K. pneumoniae, resistant to cefepime and piperacillin-tazobactam, were included in enmetazobactam dose-ranging studies. The isolates encoded CTX-M-type, SHV-12, DHA-1, and OXA-48 β-lactamases and covered a cefepime-enmetazobactam MIC range from 0.06 to 2 μg/ml. Enmetazobactam restored the efficacy of cefepime against all isolates tested. Sigmoid curve fitting across the combined set of isolates identified enmetazobactam PK-PD targets for stasis and for a 1-log₁₀ bioburden reduction of 8% and 44% fT > 2 μg/ml, respectively, with a concomitant cefepime PK-PD target of 40 to 60% fT > cefepime-enmetazobactam MIC. These findings support clinical dose selection and breakpoint setting for cefepime-enmetazobactam.

Antimicrobial activity of cephalosporin-beta-lactamase inhibitor combinations against drug-susceptible and drug-resistant Pseudomonas aeruginosa strains

Objectives

We conducted this study to test the susceptibility of P. aeruginosa to the routinely used drugs and to the two recently available antimicrobial agents, ceftazidime-avibactam and ceftolozane-tazobactam.

Methods

We isolated the non-replicate strains of P. aeruginosa from inpatients between December 2018 and April 2019. The VITEK® MS system was used for phenotypic identification and VITEK 2 for initial antimicrobial susceptibility testing. We supplemented these tests with determination of the minimum inhibitory concentration (MIC) of four antimicrobials; imipenem, meropenem, ceftazidime-avibactam and ceftolozane-tazobactam. The standards of the Clinical and Laboratory Standards Institute were followed.

Results

A total of 67 strains of P. aeruginosa, including 38 multidrug-resistant strains, were obtained from various specimens. Susceptibility to various tested aminoglycosides and fluoroquinolones was maintained in 49.3–56.7% and 40.0–43.3% of the total isolates. Amongst β-lactams, the strains were susceptible to the following agents in an ascending order: ceftazidime (32.8%), cefepime (37.3%), imipenem (36.0%), piperacillin-tazobactam (39.0%), meropenem (44.8%), ceftazidime-avibactam (61.2%) and ceftolozane-tazobactam (62.7%). The susceptibility rates of the multidrug-resistant strains to both ceftazidime-avibactam and ceftolozane-tazobactam were less than 35%. High levels of resistance to the new agents (MIC > 256 ug/ml) were detected in 21 and 22 isolates.

Conclusion

Our study shows limitation in the empirical use of ceftazidime-avibactam and ceftolozane-tazobactam as therapeutics in serious infections. Moreover, our data highlights the need for prompt antimicrobial susceptibility testing to guide their clinical usage.