Navigating treatment approaches for presumed ESBL-producing infections

Real-Time TDM-Guided Optimal Joint PK/PD Target Attainment of Continuous Infusion Piperacillin-Tazobactam Monotherapy Is an Effective Carbapenem-Sparing Strategy for Treating Non-Severe ESBL-Producing Enterobacterales Secondary Bloodstream Infections: Findings from a Prospective Pilot Study

(1) Objectives: To assess the impact of optimal joint pharmacokinetic/pharmacodynamic (PK/PD) target attainment of continuous infusion (CI) piperacillin-tazobactam monotherapy on the microbiological outcome of documented ESBL-producing Enterobacterlaes secondary bloodstream infections (BSIs). (2) Methods: Patients hospitalized in the period January 2022-October 2023, having a documented secondary BSI caused by ESBL-producing Enterobacterales, and being eligible for definitive targeted CI piperacillin-tazobactam monotherapy according to specific pre-defined inclusion criteria (i.e., absence of septic shock at onset; favorable clinical evolution in the first 48 h after starting treatment; low-intermediate risk primary infection source) were prospectively enrolled. A real-time therapeutic drug monitoring (TDM)-guided expert clinical pharmacological advice (ECPA) program was adopted for optimizing (PK/PD) target attainment of CI piperacillin-tazobactam monotherapy. Steady-state plasma concentrations (Css) of both piperacillin and tazobactam were measured, and the free fractions (f) were calculated based on theoretical protein binding. The joint PK/PD target attainment was considered optimal whenever the piperacillin fCss/MIC ratio was >4 and the tazobactam fCss/target concentration (CT) ratio was >1 (quasi-optimal or suboptimal if only one or neither of the two thresholds were achieved, respectively). Univariate analysis was carried out for assessing variables potentially associated with failure in achieving the optimal joint PK/PD target of piperacillin-tazobactam and microbiological eradication. (3) Results: Overall, 35 patients (median age 79 years; male 51.4%) were prospectively included. Secondary BSIs resulted from urinary tract infections as a primary source in 77.2% of cases. The joint PK/PD target attainment was optimal in as many as 97.1% of patients (34/35). Microbiological eradication occurred in 91.4% of cases (32/35). Attaining the quasi-optimal/suboptimal joint PK/PD target of CI piperacillin-tazobactam showed a trend toward a higher risk of microbiological failure (33.3% vs. 0.0%; p = 0.08) (4) Conclusions: Real-time TDM-guided optimal joint PK/PD target attainment of CI piperacillin-tazobactam monotherapy may represent a valuable and effective carbapenem-sparing strategy when dealing with non-severe ESBL-producing Enterobacterales secondary BSIs.

Evaluation of Piperacillin-Tazobactam Testing against Enterobacterales by the Phoenix, MicroScan, and Vitek2 Tests Using Updated Clinical and Laboratory Standards Institute Breakpoints

In 2022, the Clinical and Laboratory Standards Institute (CLSI) updated piperacillin-tazobactam (TZP) breakpoints for Enterobacterales, based on substantial data suggesting that historical breakpoints did not predict treatment outcomes for TZP. The U.S. Food and Drug Administration (FDA) has not yet adopted these breakpoints, meaning commercial manufacturers of antimicrobial susceptibility testing devices cannot obtain FDA clearance for the revised breakpoints. We evaluated the Phoenix (BD, Sparks, MD), MicroScan (Beckman Coulter, Sacramento, CA), and Vitek2 (bioMérieux, Durham, NC) TZP MICs compared to reference broth microdilution for a collection of 284 Enterobacterales isolates. Phoenix (n = 167 isolates) demonstrated 84.4% categorical agreement (CA), with 4.2% very major errors (VMEs) and 1.8% major errors (MEs) by CLSI breakpoints. In contrast, CA was 85.0% with 4.3% VMEs and 0.8% MEs for the Phoenix with FDA breakpoints. MicroScan (n = 55 isolates) demonstrated 80.0% CA, 36.4% VMEs, and 4.8% MEs by CLSI breakpoints and 81.8% CA, 44.4% VMEs, and 0.0% MEs by FDA breakpoints. Vitek2 (n = 62 isolates) demonstrated 95.2% CA, 6.3% VMEs, and 0.0% MEs by CLSI and 96.8% CA, 0.0% VMEs, and 2.2% MEs by FDA breakpoints. Overall, the performance of the test systems was not substantially different using CLSI breakpoints off-label than using on-label FDA breakpoints. However, limitations were noted with higher-than-desired VME rates (all three systems) and lower-than-desired CA (MicroScan and Phoenix). Laboratories should consider adoption of the revised CLSI breakpoints with automated test systems but be aware that some performance challenges exist for testing TZP on automated systems, regardless of breakpoints applied.

Evaluation of Piperacillin-Tazobactam ETEST for the Detection of OXA-1 Resistance Mechanism among Escherichia coli and Klebsiella pneumoniae

Globally, piperacillin-tazobactam resistance among Escherichia coli and Klebsiella pneumoniae is driven by OXA-1 beta-lactamases. Expression of bla_OXA-1 yields piperacillin-tazobactam MICs of 8 to 16 μg/mL, which straddle the susceptible/susceptible-dose dependent breakpoint set by the Clinical and Laboratory Standards Institute in 2022. Variability of the reference broth microdilution method (BMD) was evaluated by manufacturing BMD panels using 2 brands of piperacillin, 2 brands of tazobactam and 2 brands of cation-adjusted Mueller-Hinton broth. In addition, ETEST, which harbors an intermediate dilution of 12 μg/mL was evaluated for the ability to differentiate isolates with and without bla_OXA-1. A collection of 200 E. coli and K. pneumoniae, of which 82 harbored a bla_OXA-1 gene, were tested. BMD variability was on average 1.3-fold, within the accepted 2-fold variability of MICs. However, categorical agreement (CA) between BMD reads was 74.0% for all isolates and 63.4% for those with a bla_OXA-1 gene and 81.3% for those without bla_OXA-1 detected (P = 0.004, Pearson's Chi Square). ETEST overall CA with the BMD mode was 68.0% and essential agreement (EA) was 80.5%. For isolates with bla_OXA-1, CA was 50.0% and EA was 69.5%, versus 80.5% and 88.1%, respectively, for isolates without bla_OXA-1 (P < 0.0001 for both comparisons). All ETEST errors were major errors (false resistance) compared to BMD mode. However, the negative predictive value of the ETEST for the presence of bla_OXA-1 was 94.1%, compared to only 74.2% negative predictive value for BMD. Clinicians and microbiologists should be aware of the challenges associated with testing piperacillin-tazobactam in regions where bla_OXA-1 is prevalent.

Controversies over the management of infections caused by Amp-C- and ESBL-producing Enterobacterales : what questions remain for future studies?

PURPOSE OF REVIEW

The continuous rise in infections caused by third-generation cephalosporin-resistant Enterobacterales (e.g. extended-spectrum beta-lactamase- or AmpC-producing Enterobacterales ) is a major health concern. Carbapenems are regarded as the antibiotics of choice for the treatment of these infections. However, their indiscriminant use is not without consequences, and has contributed to the emergence of carbapenem-resistant Enterobacterales .In this review, we discuss the available evidence supporting the use of other betalactams, nonbetalactams and the new betalactams/beta-lactamase inhibitors (BLA/BLI) to treat these infections. We also analyze unresolved issues in this field.

RECENT FINDINGS

Piperacillin tazobactam (PTZ) was classically recommended as a carbapenem-sparing agent. However, data have emerged against its use and it is now a controversial recommendation. IDSA, European and British guidelines reject the empirical use of PTZ for these pathogens, reserving its use for rare clinical situations.Other issues that continue to generate debate are the use of extended infusion (3 h) PTZ, the use of older antibiotics, a shortened course of carbapenems and reserving the new BLA/BLI for these infections.

SUMMARY

New treatment strategies should be based on clinical evidence, local epidemiology and the microbiological activity of these drugs.

Temporal, Spatial, and Genomic Analyses of Enterobacteriaceae Clinical Antimicrobial Resistance in Companion Animals Reveals Phenotypes and Genotypes of One Health Concern

Background

Antimicrobial resistance (AMR) is a globally important one health threat. The impact of resistant infections on companion animals, and the potential public health implications of such infections, has not been widely explored, largely due to an absence of structured population-level data.

Objectives

We aimed to efficiently capture and repurpose antimicrobial susceptibility test (AST) results data from several veterinary diagnostic laboratories (VDLs) across the United Kingdom to facilitate national companion animal clinical AMR surveillance. We also sought to harness and genotypically characterize isolates of potential AMR importance from these laboratories.

Methods

We summarized AST results for 29,330 canine and 8,279 feline Enterobacteriaceae isolates originating from companion animal clinical practice, performed between April 2016 and July 2018 from four VDLs, with submissions from 2,237 United Kingdom veterinary practice sites.

Results

Escherichia coli (E. coli) was the most commonly isolated Enterobacteriaceae in dogs (69.4% of AST results, 95% confidence interval, CI, 68.7-70.0) and cats (90.5%, CI 89.8-91.3). Multi-drug resistance was reported in 14.1% (CI 13.5-14.8) of canine and 12.0% (CI 11.1-12.9) of feline E. coli isolates. Referral practices were associated with increased E. coli 3rd generation ≤ cephalosporin resistance odds (dogs: odds ratio 2.0, CI 1.2-3.4). We selected 95 E. coli isolates for whole genome analyses, of which seven belonged to sequence type 131, also carrying the plasmid-associated extended spectrum β-lactamase gene bla _{CTX-M- 15}. The plasmid-mediated colistin resistance gene mcr-9 was also identified for the first time in companion animals.

Conclusions

Linking clinical AMR data with genotypic characterization represents an efficient means of identifying important resistance trends in companion animals on a national scale.

Extended-spectrum β-lactamases: an update on their characteristics, epidemiology and detection

Extended-spectrum β-lactamase (ESBL)-producing Gram-negative pathogens are a major cause of resistance to expanded-spectrum β-lactam antibiotics. Since their discovery in the early 1980s, they have spread worldwide and an are now endemic in Enterobacterales isolated from both hospital-associated and community-acquired infections. As a result, they are a global public health concern. In the past, TEM- and SHV-type ESBLs were the predominant families of ESBLs. Today CTX-M-type enzymes are the most commonly found ESBL type with the CTX-M-15 variant dominating worldwide, followed in prevalence by CTX-M-14, and CTX-M-27 is emerging in certain parts of the world. The genes encoding ESBLs are often found on plasmids and harboured within transposons or insertion sequences, which has enabled their spread. In addition, the population of ESBL-producing Escherichia coli is dominated globally by a highly virulent and successful clone belonging to ST131. Today, there are many diagnostic tools available to the clinical microbiology laboratory and include both phenotypic and genotypic tests to detect β-lactamases. Unfortunately, when ESBLs are not identified in a timely manner, appropriate antimicrobial therapy is frequently delayed, resulting in poor clinical outcomes. Several analyses of clinical trials have shown mixed results with regards to whether a carbapenem must be used to treat serious infections caused by ESBLs or whether some of the older β-lactam-β-lactamase combinations such as piperacillin/tazobactam are appropriate. Some of the newer combinations such as ceftazidime/avibactam have demonstrated efficacy in patients. ESBL-producing Gram-negative pathogens will continue to be major contributor to antimicrobial resistance worldwide. It is essential that we remain vigilant about identifying them both in patient isolates and through surveillance studies.