KPC-31 expressed in a ceftazidime/avibactam-resistant Klebsiella pneumoniae is associated with relevant detection issues

Evaluation of the Vitek® Reveal™ system for rapid antimicrobial susceptibility testing of Gram-negative pathogens, including ESBL, CRE and CRAB, from positive blood cultures

Blood culture (BC) remains the reference diagnostic tool for bloodstream infections but is hampered by long turn-around time (TAT). This study evaluated the Vitek® Reveal™ (VR) system for rapid antimicrobial susceptibility testing (AST) with 72 cases of monomicrobial BCs (55 Enterobacterales, 12 Pseudomonas aeruginosa and 5 Acinetobacter baumannii), including isolates producing carbapenemases and/or extended-spectrum β-lactamases. VR returned AST results with a mean TAT of 5.4 h. Compared to a conventional workflow based on broth microdilution, VR exhibited essential agreement (EA) and category agreement (CA) >90 % in most cases, except with meropenem for Enterobacterales (CA, 85.5 %), piperacillin/tazobactam for P. aeruginosa (EA, 83.3 %), and trimethoprim/sulfamethoxazole for A. baumannii (CA and EA, 80 %). Bias exhibited an underestimation trend with ceftazidime/avibactam (-78.9 %) and ceftazidime (-50 %) for Enterobacterales and P. aeruginosa, respectively. Overall, VR appears an interesting tool to decrease TAT of the BC workflow, although further evaluation with some antibiotic-pathogen combinations would be warranted.

Identification of a Novel KPC Variant, KPC-204, Conferring Resistance to Both Carbapenems and Ceftazidime-Avibactam in an ST11 Klebsiella pneumoniae Strain

This study describes KPC-204, a novel variant of Klebsiella pneumoniae carbapenemase, characterized by a Lys-Asp-Asp (KDD) amino acid insertion at Ambler position 269 deviates from KPC-2. This variant was identified in an ST11-type clinical isolate of carbapenem-resistant Klebsiella pneumoniae from China. Notably, KPC-204 exhibits resistance to both ceftazidime-avibactam and carbapenems. Genetic analysis revealed that blaKPC-204 was located on a highly mobile IncFII/IncR plasmid within a complex genetic structure that facilitates its spread. Functional analysis, achieved through cloning into E. coli DH5α, validates KPC-204's contribution to increased resistance to ceftazidime-avibactam. The kinetic parameters showed that KPC-204 exhibited similar affinity to KPC-2 toward ceftazidime and reduced sensitivity to avibactam. Docking simulations revealed a weaker interaction between KPC-204 and avibactam compared to KPC-2. Mating experiments demonstrated the resistance's transmissibility. This investigation underscores the evolving diversity of KPC variants affecting ceftazidime-avibactam resistance, highlighting the necessity for continuous monitoring.

First report of KPC variants conferring ceftazidime-avibactam resistance in Colombia: introducing KPC-197

Resistance to ceftazidime-avibactam (CZA) due to Klebsiella pneumoniae carbapenemase (KPC) variants is increasing worldwide. We characterized two CZA-resistant clinical Klebsiella pneumoniae strains by antimicrobial susceptibility test, conjugation assays, and WGS. Isolates belonged to ST258 and ST45, and produced a KPC-31 and a novel variant KPC-197, respectively. The novel KPC variant presents a deletion of two amino acids on the Ω-loop (del_168-169_EL) and an insertion of two amino acids in position 274 (Ins_274_DS). Continued surveillance of KPC variants conferring CZA resistance in Colombia is warranted.

IMPORTANCE

Latin America and the Caribbean is an endemic region for carbapenemases. Increasingly high rates of Klebsiella pneumoniae carbapenemase (KPC) have established ceftazidime-avibactam (CZA) as an essential antimicrobial for the treatment of infections due to MDR Gram-negative pathogens. Although other countries in the region have reported the emergence of CZA-resistant KPC variants, this is the first description of such enzymes in Colombia. This finding warrants active surveillance, as dissemination of these variants could have devastating public health consequences.

Simultaneous post-neurosurgical ventriculitis and bacteraemia by two different strains of KPC-producing K. pneumoniae successfully treated with meropenem/vaborbactam and high dose of fosfomycin

OBJECTIVE

A case of post-neurosurgical ventriculitis caused by a KPC-producing Klebsiella pneumoniae (KPC-Kp) with a ceftazidime/avibactam-resistant, meropenem-susceptible phenotype is reported.

METHODS AND RESULTS

The patient had a concomitant bloodstream infection with a wild-type KPC-Kp with a ceftazidime/avibactam-susceptible, meropenem-resistant phenotype. Prolonged treatment with intravenous fosfomycin and meropenem/vaborbactam achieved clinical success. Therapeutic drug monitoring performed during the first days of treatment showed for the first time that vaborbactam efficiently penetrates cerebrospinal fluid. In contrast, meropenem was undetectable in cerebrospinal fluid at each sampling, suggesting that additional doses of meropenem may be required to appropriately prescribe meropenem/vaborbactam for central nervous system infections. Plasma and cerebrospinal fluid levels of fosfomycin were adequate, confirming the potential of this agent possibly even in the fight against multidrug-resistant organisms.

CONCLUSIONS

This case highlights the need for therapeutic drug monitoring as a crucial tool for optimizing treatment in complicated cases where the pharmacokinetic behaviour of antibiotics is difficult to predict.

A novel KPC-166 in ceftazidime/avibactam resistant ST307 Klebsiella pneumoniae causing an outbreak in intensive care COVID Unit, Italy

INTRODUCTION

Aim of the study was the molecular characterization of 21 ceftazidime/avibactam resistant (CZA-R) Klebsiella pneumoniae strains, collected in the period October 2021-March 2022 from an Intensive Care COVID Unit in a Northern Italian Hospital.

METHODS

After growth on selective/chromogenic culture media and susceptibility tests assessment, resistance genes content was ascertained for all the isolates by the HybriSpot 12 multiplexing, PCR and Whole-Genome Sequencing (WGS). Clonality was assessed by PFGE and MLST according to the Pasteur scheme. A SNPs-based phylogenetic tree was obtained comparing representative isolates and global genomes. The blaKPC gene horizontal transmission was evaluated by conjugation experiments. blaKPC-166 was cloned in a pCR2.1 vector and transformed in chemically competent TOP10 cells.

RESULTS

Sixteen inpatients resulted positive for colonization and/or infection by KPC-producing K. pneumoniae (KPC-Kp) strains. The 21 CZA-R KPC-Kp isolates obtained showed MDR phenotype; susceptibility to meropenem was always retained. All the CZA-R KPC-Kp presented a novel blaKPC variant, named blaKPC-166, showing a single nucleotide substitution (T811C) compared to the blaKPC-94; but related to blaKPC-2.

TWO DIFFERENT PULSOTYPES WERE DETECTED

A in 18/21 and B in 1/21 cases, two strains from the same patient being untypable by PFGE. Interestingly, the outbreak was sustained by the high-risk clone ST307, although the ST22, ST6342, ST6418 and ST6811 have also been identified and associated to KPC-166. Worryingly, blaKPC-166 could be transferred horizontally and, after cloning, it conferred resistance to CZA.

DISCUSSION

This novel variant confers CZA-resistance and carbapenems susceptibility restoration. As KPC-166 was found expressed by multiple Kp clones, greater efforts should be made to prevent the further dissemination of such strains in Italian clinical settings.

Rapid Detection of Ceftazidime/Avibactam Susceptibility/Resistance in Enterobacterales by Rapid CAZ/AVI NP Test

We developed a novel culture-based test, the Rapid CAZ/AVI NP test, for rapid identification of ceftazidime/avibactam susceptibility/resistance in Enterobacterales. This test is based on glucose metabolization upon bacterial growth in the presence of a defined concentration of ceftazidime/avibactam (128/53 μg/mL). Bacterial growth is visually detectable by a red to yellow color change of red phenol, a pH indicator. A total of 101 well characterized enterobacterial isolates were used to evaluate the test performance. This test showed positive percent agreement of 100% and negative percent agreement of 98.5% with overall percent agreement of 99%, by comparison with the MIC gradient strip test (Etest) taken as the reference standard method. The Rapid CAZ/AVI NP test had only 1.5% major errors and 0% extremely major errors. This test is rapid (result within 2 hours 45 minutes), reliable, affordable, easily interpretable, and easy to implement in clinical microbiology laboratories without requiring any specific equipment.

Carbapenem-resistant Klebsiella pneumoniae: the role of plasmids in emergence, dissemination, and evolution of a major clinical challenge

INTRODUCTION

Klebsiella pneumoniae is a major agent of healthcare-associated infections and a cause of some community-acquired infections, including severe bacteremic infections associated with metastatic abscesses in liver and other organs. Clinical relevance is compounded by its outstanding propensity to evolve antibiotic resistance. In particular, the emergence and dissemination of carbapenem resistance in K. pneumoniae has posed a major challenge due to the few residual treatment options, which have only recently been expanded by some new agents. The epidemiological success of carbapenem-resistant K. pneumoniae (CR-Kp) is mainly linked with clonal lineages that produce carbapenem-hydrolyzing enzymes (carbapenemases) encoded by plasmids.

AREAS COVERED

Here, we provide an updated overview on the mechanisms underlying the emergence and dissemination of CR-Kp, focusing on the role that plasmids have played in this phenomenon and in the co-evolution of resistance and virulence in K. pneumoniae.

EXPERT OPINION

CR-Kp have disseminated on a global scale, representing one of the most important contemporary public health issues. These strains are almost invariably associated with complex multi-drug resistance (MDR) phenotypes, which can also include recently approved antibiotics. The heterogeneity of the molecular bases responsible for these phenotypes poses significant hurdles for therapeutic and diagnostic purposes.

Klebsiella pneumoniae carbapenemase variant 44 acquires ceftazidime-avibactam resistance by altering the conformation of active-site loops

Klebsiella pneumoniae carbapenemase 2 (KPC-2) is an important source of drug resistance as it can hydrolyze and inactivate virtually all β-lactam antibiotics. KPC-2 is potently inhibited by avibactam via formation of a reversible carbamyl linkage of the inhibitor with the catalytic serine of the enzyme. However, the use of avibactam in combination with ceftazidime (CAZ-AVI) has led to the emergence of CAZ-AVI-resistant variants of KPC-2 in clinical settings. One such variant, KPC-44, bears a 15 amino acid duplication in one of the active-site loops (270-loop). Here, we show that the KPC-44 variant exhibits higher catalytic efficiency in hydrolyzing ceftazidime, lower efficiency toward imipenem and meropenem, and a similar efficiency in hydrolyzing ampicillin, than the WT KPC-2 enzyme. In addition, the KPC-44 variant enzyme exhibits 12-fold lower AVI carbamylation efficiency than the KPC-2 enzyme. An X-ray crystal structure of KPC-44 showed that the 15 amino acid duplication results in an extended and partially disordered 270-loop and also changes the conformation of the adjacent 240-loop, which in turn has altered interactions with the active-site omega loop. Furthermore, a structure of KPC-44 with avibactam revealed that formation of the covalent complex results in further disorder in the 270-loop, suggesting that rearrangement of the 270-loop of KPC-44 facilitates AVI carbamylation. These results suggest that the duplication of 15 amino acids in the KPC-44 enzyme leads to resistance to CAZ-AVI by modulating the stability and conformation of the 270-, 240-, and omega-loops.

Klebsiella pneumoniae carbapenemase variants: the new threat to global public health

Klebsiella pneumoniae carbapenemase (KPC) variants, which refer to the substitution, insertion, or deletion of amino acid sequence compared to wild blaKPC type, have reduced utility of ceftazidime-avibactam (CZA), a pioneer antimicrobial agent in treating carbapenem-resistant Enterobacterales infections. So far, more than 150 blaKPC variants have been reported worldwide, and most of the new variants were discovered in the past 3 years, which calls for public alarm. The KPC variant protein enhances the affinity to ceftazidime and weakens the affinity to avibactam by changing the KPC structure, thereby mediating bacterial resistance to CZA. At present, there are still no guidelines or expert consensus to make recommendations for the diagnosis and treatment of infections caused by KPC variants. In addition, meropenem-vaborbactam, imipenem-relebactam, and other new β-lactam-β-lactamase inhibitor combinations have little discussion on KPC variants. This review aims to discuss the clinical characteristics, risk factors, epidemiological characteristics, antimicrobial susceptibility profiles, methods for detecting blaKPC variants, treatment options, and future perspectives of blaKPC variants worldwide to alert this new great public health threat.

Treatment and diagnosis of severe KPC-producing Klebsiella pneumoniae infections: a perspective on what has changed over last decades

Antimicrobial resistance is a global health threat. Among Gram-negative bacteria, resistance to carbapenems, a class of β-lactam antibiotics, is usually a proxy for difficult-to-treat resistance, since carbapenem-resistant organisms are often resistant to many classes of antibiotics. Carbapenem resistance in the Gram-negative pathogen Klebsiella pneumoniae is mostly due to the production of carbapenemases, enzymes able to hydrolyze carbapenems, and K. pneumoniae carbapenemase (KPC)-type enzymes are overall the most prevalent carbapenemases in K. pneumoniae. In the last decade, the management of severe infections due to KPC-producing K. pneumoniae (KPC-Kp) in humans has presented many peculiar challenges to clinicians worldwide. In this perspective, we discuss how the treatment of severe KPC-Kp infections has evolved over the last decades, guided by the accumulating evidence from clinical studies, and how recent advances in diagnostics have allowed to anticipate identification of KPC-Kp in infected patients.KEY MESSAGESIn the last decade, the management of severe infections due to KPC-Kp has presented many peculiar challenges to clinicians worldwideFollowing the introduction in clinical practice of novel β-lactam/β-lactamase inhibitor combinations and novel β-lactams active against KPC-producing bacteria, the management of severe KPC-Kp infections has witnessed a remarkable evolutionTreatment of severe KPC-Kp infections is a highly dynamic process, in which the wise use of novel antimicrobials should be accompanied by a continuous refinement based on evolving clinical evidence and laboratory diagnostics.

Clinical Characteristics and Outcome of Ceftazidime/Avibactam-Resistant Klebsiella pneumoniae Carbapenemase-Producing Klebsiella pneumoniae Infections: A Retrospective, Observational, 2-Center Clinical Study

Background

Recently, Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) with resistance to ceftazidime/avibactam (CZA-R) has been described, including KPC variants that restore carbapenem susceptibility. The aim of the study was to analyze the clinical characteristics and outcomes of infections caused by CZA-R KPC-Kp.

Methods

From 2019 to 2021, a retrospective 2-center study including patients with infections due to CZA-R KPC-Kp hospitalized at 2 academic hospitals in Rome was conducted. Demographic and clinical characteristics were collected. Principal outcome was 30-day all-cause mortality. Statistical analyses were performed with Stata-IC17 software.

Results

Overall, 59 patients were included (mean age, 64.4 ± 14.6 years; mean Charlson comorbidity index score, 4.5 ± 2.7). Thirty-four patients (57.6%) had infections caused by CZA-R and meropenem (MEM)-susceptible strains. A previous CZA therapy was observed in 40 patients (67.8%), mostly in patients with MEM-susceptible KPC variant (79.4% vs 52%, P = .026). Primary bacteremia was observed in 28.8%, followed by urinary tract infections and pneumonia. At infection onset, septic shock was present in 15 subjects (25.4%). After adjustment for confounders, only the presence of septic shock was independently associated with mortality (P = .006).

Conclusions

Infections due to CZA-R KPC-Kp often occur in patients who had previously received CZA, especially in the presence of strains susceptible to MEM. Nevertheless, one-third of patients had never received CZA before KPC-Kp CZA-R. Since the major driver for mortality was infection severity, understanding the optimal therapy in patients with KPC-Kp CZA-R infections is of crucial importance.

Laboratory automation, informatics, and artificial intelligence: current and future perspectives in clinical microbiology

Clinical diagnostic laboratories produce one product-information-and for this to be valuable, the information must be clinically relevant, accurate, and timely. Although diagnostic information can clearly improve patient outcomes and decrease healthcare costs, technological challenges and laboratory workflow practices affect the timeliness and clinical value of diagnostics. This article will examine how prioritizing laboratory practices in a patient-oriented approach can be used to optimize technology advances for improved patient care.

Resistance to Ceftazidime/Avibactam in Klebsiella pneumoniae KPC-Producing Isolates: A Real-Life Observational Study

Background: Ceftazidime/avibactam (CAZ-AVI) resistance amongst Enterobacterales is worryingly increasing worldwide. Objectives: The aim of this study was to collect and describe real-life data on CAZ-AVI-resistant Klebsiella pneumoniae (KP) isolates in our University Hospital, with the ultimate goal of evaluating possible risk factors related to the acquisition of resistance. Methods: This is a retrospective observational study, including unique Klebsiella pneumoniae (KP) isolates resistant to CAZ-AVI (CAZ-AVI-R) and producing only KPC, collected from July 2019 to August 2021 at Policlinico Tor Vergata, Rome, Italy. The pathogen's list was obtained from the microbiology laboratory; clinical charts of the corresponding patients were reviewed to collect demographic and clinical data. Subjects treated as outpatients or hospitalized for <48 h were excluded. Patients were then divided into two groups: S group, if they had a prior isolate of CAZ-AVI-susceptible KP-KPC, and R group, if the first documented isolate of KP-KPC was resistant to CAZ-AVI. Results: Forty-six unique isolates corresponding to 46 patients were included in the study. The majority of patients (60.9%) were hospitalized in an intensive care unit, 32.6% in internal medicine wards and 6.5% in surgical wards. A total of 15 (32.6%) isolates were collected from rectal swabs, representing a colonization. Amongst clinically relevant infections, pneumonia and urinary tract infections were the most commonly found (5/46, 10.9% each). Half of the patients received CAZ-AVI prior to isolation of the KP-KPC CAZ-AVI-R (23/46). This percentage was significantly higher in patients in the S group compared to patients in the R group (69.3% S group vs. 25% R group, p = 0.003). No differences between the two groups were documented in the use of renal replacement therapy or in the infection site. The clinically relevant CAZ-AVI-R KP infections (22/46, 47.8%) were all treated with a combination therapy, 65% including colistin and 55% including CAZ-AVI, with an overall clinical success of 38.1%. Conclusions: Prior use of CAZ-AVI was associated with the emergence of drug resistance.

The primary pharmacology of ceftazidime/avibactam: resistance in vitro

This article reviews resistance to ceftazidime/avibactam as an aspect of its primary pharmacology, linked thematically with recent reviews of the basic in vitro and in vivo translational biology of the combination (J Antimicrob Chemother 2022; 77: 2321-40 and 2341-52). In Enterobacterales or Pseudomonas aeruginosa, single-step exposures to 8×  MIC of ceftazidime/avibactam yielded frequencies of resistance from <∼0.5 × 10-9 to 2-8 × 10-9, depending on the host strain and the β-lactamase harboured. β-Lactamase structural gene mutations mostly affected the avibactam binding site through changes in the Ω-loop: e.g. Asp179Tyr (D179Y) in KPC-2. Other mutations included ones proposed to reduce the permeability to ceftazidime and/or avibactam through changes in outer membrane structure, up-regulated efflux, or both. The existence, or otherwise, of cross-resistance between ceftazidime/avibactam and other antibacterial agents was also reviewed as a key element of the preclinical primary pharmacology of the new agent. Cross-resistance between ceftazidime/avibactam and other β-lactam-based antibacterial agents was caused by MBLs. Mechanism-based cross-resistance was not observed between ceftazidime/avibactam and fluoroquinolones, aminoglycosides or colistin. A low level of general co-resistance to ceftazidime/avibactam was observed in MDR Enterobacterales and P. aeruginosa. For example, among 2821 MDR Klebsiella spp., 3.4% were resistant to ceftazidime/avibactam, in contrast to 0.07% of 8177 non-MDR isolates. Much of this was caused by possession of MBLs. Among 1151 MDR, XDR and pandrug-resistant isolates of P. aeruginosa from the USA, 11.1% were resistant to ceftazidime/avibactam, in contrast to 3.0% of 7452 unselected isolates. In this case, the decreased proportion susceptible was not due to MBLs.

Ceftazidime-Avibactam (C/A) Resistant, Meropenem Sensitive KPC-Producing Klebsiella pneumoniae in ICU Setting: We Are What We Are Treated with?

The continuous spread of carbapenem-resistant Klebsiella pneumoniae (CP-Kp) strains presents a severe challenge to the healthcare system due to limited therapeutic options and high mortality. Since its availability, ceftazidime/avibactam (C/A) has become a first-line option against KPC-Kp, but C/A-resistant strains have been reported increasingly, especially with pneumonia or prior suboptimal blood exposure to C/A treatment. A retrospective, observational study was conducted with all patients admitted to the Intensive Care Unit (ICU) dedicated to COVID-19 patients at the City of Health & Sciences in Turin, between 1 May 2021 and 31 January 2022, with the primary endpoint to study strains with resistance to C/A, and secondly to describe the characteristics of this population, with or without previous exposure to C/A. Seventeen patients with colonization or invasive infection due to Klebsiella pneumoniae, C/A resistance, and susceptibility to meropenem (MIC = 2 µg/L) were included; the bla_KPC genotype was detected in all isolates revealing D179Y mutation in the bla_KPC-2 (bla_KPC-33) gene. Cluster analysis showed that 16 out of the 17 C/A-resistant KPC-Kp isolates belonged to a single clone. Thirteen strains (76.5%) were isolated in a 60-day period. Only some patients had a previous infection with non-mutant KPC at other sites (5; 29.4%). Eight patients (47.1%) underwent previous large-spectrum antibiotic treatment, and four patients (23.5%) had prior treatment with C/A. The secondary spread of the D179Y mutation in the bla_KPC-2 during the COVID-19 pandemic needs to be addressed constantly by an interdisciplinary interaction between microbiologists, infection control personnel, clinicians, and infectious diseases consultants to properly diagnose and treat patients.

Outbreak of Klebsiella pneumoniae ST11 Resistant To Ceftazidime-Avibactam Producing KPC-31 and the Novel Variant KPC-115 during COVID-19 Pandemic in Argentina

We describe an outbreak of Klebsiella pneumoniae sequence type 11 (ST11) producing KPC variants resistant to ceftazidime-avibactam. Six patients hospitalized in the intensive care unit (mostly due to critical COVID pneumonia) presented infection or colonization by this bacterium. They had several comorbidities and required mechanical ventilation, central venous catheters, and urinary catheters. All 6 patients had a history of fecal colonization with KPC-producing Enterobacterales (KPC-E). Three of them had previous episodes of infection with ceftazidime-avibactam-susceptible KPC-producing K. pneumoniae, which were treated with ceftazidime-avibactam. Several phenotypic methods failed to detect carbapenemase production in these 6 ceftazidime-avibactam-resistant isolates, and they showed in vitro susceptibility to imipenem and meropenem. All of them rendered positive results for blaKPC by PCR, and amplicon sequencing identified blaKPC-31 variant in 5 isolates and a novel variant, named blaKPC-115, in the other. Moreover, matrix-assisted laser desorption ionization-time of flight mass spectrometry was able to detect KPC in all isolates. Ceftazidime-avibactam-resistant isolates, as well as those recovered from previous infection episodes (KPC-3-producing K. pneumoniae, ceftazidime-avibactam susceptible), displayed a unique pulse type and belonged to ST11. Based on whole-genome sequencing results of selected isolates, less than 7 single-nucleotide polymorphisms were identified among them, which was indicative of the presence of a unique clone. Both in vivo selection and horizontal transmission seemed to have occurred in our hospital. Detection of these strains is challenging for the laboratory. History of previous KPC-E infections or colonization and systematic testing for resistance to ceftazidime-avibactam might help raise awareness of this possibility. IMPORTANCE Klebsiella pneumoniae is one of the main bacteria that cause infections in health care settings. This pathogen has developed a high level of resistance to many antibiotics. Some K. pneumoniae isolates can produce an enzyme known as carbapenemase KPC, making carbapenems (considered the last line for therapy) not effective to treat their infections. The combination ceftazidime-avibactam, approved by FDA in 2015, is useful to treat infections caused by KPC-producing K. pneumoniae. This study describes the emergence, in one hospital in Argentina, of K. pneumoniae isolates that produce KPC variants (KPC-31 and KPC-115) resistant to ceftazidime-avibactam. The ceftazidime-avibactam-resistant bacteria were isolated in inpatients, including some that previously received this combination as treatment. Transmission of this strain to other patients also occurred in the studied period. Detection of these bacteria is challenging for the laboratory. The knowledge and awareness of the emergence of this pathogen in our region are highly valuable.

An interventional quasi-experimental study to evaluate the impact of a rapid screening strategy in improving control of nosocomial extended-spectrum beta-lactamase-producing Enterobacterales and carbapenemase-producing organisms in critically ill patients

Introduction

Rapid molecular tests could accelerate the control of extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE) and carbapenemase-producing organisms (CPO) in intensive care units (ICUs).

Objective and methods

This interventional 12-month cohort study compared a loop-mediated isothermal amplification (LAMP) assay performed directly on rectal swabs with culturing methods (control period, 6 months), during routine ICU screening. Contact precautions (CP) were implemented for CPO or non-E. coli ESBL-producing Enterobacterales (nEcESBL-PE) carriers. Using survival analysis, we compared the time intervals from admission to discontinuation of unnecessary preemptive CP among patients at-risk and the time intervals from screening to implementation of CP among newly identified carriers. We also compared diagnostic performances, and nEcESBL-PE/CPO acquisition rates. This study is registered, ISRCTN 23588440.

Results

We included 1043 patients. During the intervention and control phases, 92/147 (62.6%) and 47/86 (54.7%) of patients at-risk screened at admission were candidates for early discontinuation of preemptive CP. The LAMP assay had a positive predictive value (PPV) of 44.0% and a negative predictive value (NPV) of 99.9% for CPO, and 55.6% PPV and 98.2% NPV for nEcESBL-PE. Due to result notification and interpretation challenges, the median time from admission to discontinuation of preemptive CP increased during the interventional period from 80.5 (95% CI 71.5–132.1) to 88.3 (95% CI 57.7–103.7) hours (p = 0.47). Due to the poor PPV, we had to stop using the LAMP assay to implement CP. No difference was observed regarding the incidence of nEcESBL-PE and CPO acquisition.

Conclusion

A rapid screening strategy with LAMP assays performed directly on rectal swabs had no benefit for infection control in a low-endemicity setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04027-8.

Klebsiella pneumoniae Carbapenemase Variants Resistant to Ceftazidime-Avibactam: an Evolutionary Overview

First variants of the Klebsiella pneumoniae carbapenemase (KPC), KPC-2 and KPC-3, have encountered a worldwide success, particularly in K. pneumoniae isolates. These beta-lactamases conferred resistance to most beta-lactams including carbapenems but remained susceptible to new beta-lactam/beta-lactamase inhibitors, such as ceftazidime-avibactam. After the marketing of ceftazidime-avibactam, numerous variants of KPC resistant to this association have been described among isolates recovered from clinical samples or derived from experimental studies. In KPC variants resistant to ceftazidime-avibactam, point mutations, insertions and/or deletions have been described in various hot spots. Deciphering the impact of these mutations is crucial, not only from a therapeutic point of view, but also to follow the evolution in time and space of KPC variants resistant to ceftazidime-avibactam. In this review, we describe the mutational landscape of the KPC beta-lactamase toward ceftazidime-avibactam resistance based on a multidisciplinary approach including epidemiology, microbiology, enzymology, and thermodynamics. We show that resistance is associated with three hot spots, with a high representation of insertions and deletions compared with other class A beta-lactamases. Moreover, extension of resistance to ceftazidime-avibactam is associated with a trade-off in the resistance to other beta-lactams and a decrease in enzyme stability. Nevertheless, the high natural stability of KPC could underlay the propensity of this enzyme to acquire in vivo mutations conferring resistance to ceftazidime-avibactam (CAZavi), particularly via insertions and deletions.

Implementation of Chromatic Super CAZ/AVI® medium for active surveillance of ceftazidime-avibactam resistance: preventing the loop from becoming a spiral

Acquired resistance towards ceftazidime-avibactam (CAZ-AVI) is increasingly reported. Several mechanisms can be involved, but mutations in the Ω-loop region of β-lactamases are the most described. Herein, we assessed the implementation of Chromatic Super CAZ/AVI^® medium in rectal swab surveillance cultures in a geographic area with endemic distribution of KPC-producing Klebsiella pneumoniae. Routine rectal swabs collected from the intensive care unit (ICU) and non-ICU patients were screened for carbapenemase-producing Enterobacterales (CPE), carbapenem-resistant Gram-negative organisms (CR-GN) and CAZ-AVI-resistant organisms by Chromatic CRE and Super CAZ/AVI^® media. Among the 1839 patients screened, 146 (7.9%) were found to be colonized by one or more CPE and/or CR-GN isolates during hospitalization. Overall, among colonized patients the most common bacteria encountered were KPC-producing Enterobacterales (n = 60; 41.1%), carbapenem-resistant Pseudomonas aeruginosa (n = 41; 28.1%) and carbapenem-resistant A. baumannii (n = 34; 23.3%). Among patients colonized by KPC-producing Enterobacterales, thirty-five (58.3%) had CAZ-AVI-resistant strains. A 30.5% rate of faecal carriage of CAZ-AVI-resistant KPC-producing K. pneumoniae, substantially higher than that of susceptible isolates (2.8%), was observed in the COVID-19 ICU. Prevalence of faecal carriage of metallo-β-lactamase-producing organisms was low (0.5% and 0.2% for Enterobacterales and P. aeruginosa, respectively). Chromatic Super CAZ/AVI^® medium showed 100% sensitivity in detecting CPE or CR-GN isolates resistant to CAZ-AVI regardless of both MIC values and carbapenemase content. Specificity was 86.8%. The Chromatic Super CAZ/AVI^® medium might be implemented in rectal swab surveillance cultures for identification of patients carrying CAZ-AVI-resistant organisms to contain the spread of these difficult-to-treat pathogens.

Update of clinical application in ceftazidime-avibactam for multidrug-resistant Gram-negative bacteria infections

PURPOSE

Multidrug-resistant Gram-negative bacteria (MDR-GNB) have become a major global public health threat. Ceftazidime-avibactam (CAZ-AVI) is a newer combination of β-lactam/β-lactamase inhibitor, with activity against carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA). The aim of this review is to describe the recent real-world experience of CAZ-AVI for the infections due to MDR-GNB.

METHODS

We searched PubMed, Embase and Google Scholar for clinical application in CAZ-AVI for MDR-GNB infections. Reference lists were reviewed and synthesized for narrative review.

RESULTS

MDRGNB infections are associated with higher mortality significantly comparing to drug-susceptible bacterial infections. Fortunately, CAZ-AVI shows significant benefits for infections due to KPC or OXA-48 CRE, comparing to colistin, carbapenem, aminoglycoside and other older agents, even in those with immunocompromised status. The efficacy of CAZ-AVI varies in different infection sites due to CRE, which is lower in pneumonia. Early use is associated with improved clinical outcomes. Noteworthy, when adopted as salvage therapy, CAZ-AVI is still superior to other GNB active antibiotics. CAZ-AVI plus aztreonam is recommended as the first line of MBL-CRE infections. However, for infections caused by KPC- and OXA-48-producing isolates, further investigations are needed to demonstrate the benefit of combination therapy. Besides CRE, CAZ-AVI is also active to MDR-PA. However, the development of resistance in CRE and MDR-PA against CAZ-AVI is alarming, and more investigations and studies are needed to prevent, diagnose, and treat infections due to CAZ-AVI-resistant pathogens.

CONCLUSIONS

CAZ-AVI appears to be a valuable therapeutic option in MDR-GNB infections. Using CAZ-AVI appropriately to improve efficacy and decrease the emergence of resistance is important.

Resistance mechanisms in Gram-negative bacteria

Enterobacterales resistant to carbapenems or producing extended-spectrum β-lactamases (ESBL) and non-fermenters resistant to carbapenems present resistance to many of the antimicrobials commonly used in clinical practice, and have been recognized by the World Health Organization as a critical priority for the development of new antimicrobials. In this review, the main mechanisms of resistance of Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia to β-lactams, quinolones, aminoglycosides and polymyxins will be addressed. Updated information will be presented on the importance in resistance of antimicrobial modification mechanisms (including class C or extended-spectrum β-lactamases, carbapenemases and aminoglycoside-modifying enzymes), permeability alterations due to porin or lipopolysaccharide expression disorders, production of active efflux pumps, target alterations or protection, and expression of two-component systems.

The Rapid Emergence of Ceftazidime-Avibactam Resistance Mediated by KPC Variants in Carbapenem-Resistant Klebsiella pneumoniae in Zhejiang Province, China

Ceftazidime-avibactam (CAV) is a new treatment option against carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. However, the rapid emergence of CAV resistance mediated by KPC variants has posed a severe threat to healthcare after its clinical application. The characteristics of CAV resistance in CRKP strains needs to be determined in China. A total of 477 CRKP isolates were collected from 46 hospitals in Zhejiang Province from 2018 to 2021. The results demonstrated that CAV had a potent activity against 94.5% of all CRKP (451/477, 95% CI: 93.0–96.1%) and 86.0% of CRKP strains carrying bla_KPC genes (410/477, 95% CI: 83.5–88.4%). A total of 26 CAV-resistant strains were found. Among these strains, sixteen harbored metallo-β lactamases, and two carried KPC-2 carbapenemase and mutated ompK35 and ompK36. Eight CRKP strains encoded KPC-33 or KPC-93, belonging to ST11, among which seven strains were detected in patients hospitalized in 2021 after exposure to CAV and one strain was associated with intra-hospital spread. CAV is a potent agent in vitro against CRKP strains. The rapid development of CAV resistance mediated by various KPC variants after a short period of CAV treatment has increased and brought difficulties in treating infections caused by CRKP strains, especially those belonging to ST11. The surveillance of bacterial resistance against CAV is highly recommended due to the steep development of CAV resistance and rapid evolution of KPC enzymes.

Resistance to Ceftazidime/Avibactam, Meropenem/Vaborbactam and Imipenem/Relebactam in Gram-Negative MDR Bacilli: Molecular Mechanisms and Susceptibility Testing

Multidrug resistance (MDR) represents a serious global threat due to the rapid global spread and limited antimicrobial options for treatment of difficult-to-treat (DTR) infections sustained by MDR pathogens. Recently, novel β-lactams/β-lactamase inhibitor combinations (βL-βLICs) have been developed for the treatment of DTR infections due to MDR Gram-negative pathogens. Although novel βL-βLICs exhibited promising in vitro and in vivo activities against MDR pathogens, emerging resistances to these novel molecules have recently been reported. Resistance to novel βL-βLICs is due to several mechanisms including porin deficiencies, increasing carbapenemase expression and/or enzyme mutations. In this review, we summarized the main mechanisms related to the resistance to ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam in MDR Gram-negative micro-organisms. We focused on antimicrobial activities and resistance traits with particular regard to molecular mechanisms related to resistance to novel βL-βLICs. Lastly, we described and discussed the main detection methods for antimicrobial susceptibility testing of such molecules. With increasing reports of resistance to novel βL-βLICs, continuous attention should be maintained on the monitoring of the phenotypic traits of MDR pathogens, into the characterization of related mechanisms, and on the emergence of cross-resistance to these novel antimicrobials.

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

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

Impact of ceftazidime-avibactam treatment in the emergence of novel KPC variants in ST307-Klebsiella pneumoniae high-risk clone and consequences for their routine detection

Emergence of Klebsiella pneumoniae (Kp) isolates carrying novel bla_KPC variants conferring ceftazidime-avibactam (CAZ/AVI) resistance is being increasingly reported. We evaluated the accuracy of phenotypic methods commonly used in routine clinical laboratories in the detection of novel KPC enzymes. Additionally, we characterized by WGS the KPC-ST307-Kp isolates recovered in our hospital before and after CAZ/AVI therapy. Rectal colonization or infection by carbapenem-resistant KPC-3-Kp isolates (imipenem MIC 16 mg/L, meropenem MIC 8->16 mg/L) and CAZ/AVI-susceptible (CAZ/AVI MIC 1-2 mg/L) were first detected in three ICU patients admitted between March-2020 and July-2020. KPC-Kp isolates with increased CAZ/AVI MICs (8-32 mg/L) and carbapenem susceptibility (imipenem and meropenem MIC <1 mg/L) were recovered within 6-24 days after CAZ/AVI treatment. WGS confirmed that all KPC-Kp isolates belonged to the ST307 high-risk clone and carried identical antimicrobial resistance genes and virulence factors. The presence of the novel bla_KPC-46, bla_KPC-66 and bla_KPC-92 genes was confirmed in the Kp isolates with increased CAZ/AVI MICs and restored carbapenem activity. KPC production was confirmed by immunochromatography, the eazyplex®-Superbug-CRE system and the Xpert® Carba-R assay in all KPC-Kp isolates, but not in any isolate using chromogenic agar plates for carbapenemase producers (ChromID-CARBA), the KPC/MBL/OXA-48 Confirm Kit and the β-CARBA test. Nevertheless, all grew in chromogenic agar plates for ESBL producers (ChromID-ESBL). We report the failure of the most common phenotypic methods used for the detection of novel KPC carbapenemases but not of rapid molecular or immunochromatography assays thus highlighting their relevance in microbiology laboratories.

Evaluation of Revogene® Carba C assay for the rapid detection of carbapenemase genes in gram-negative pathogens

The rapid detection of carbapenemase-producing microorganisms is crucial for clinical and infection control purposes. Here we evaluated Revogene®Carba C assay on 154 carbapenemase-producing and -nonproducing Gram-negatives. Up to 8 samples per 70 minutes were processed by Revogene®Carba C assay which showed excellent performances with 100% sensitivity, 99.5% specificity,100% NPV, and 97.8% positive predictive value.

KPC-39-Mediated Resistance to Ceftazidime-Avibactam in a Klebsiella pneumoniae ST307 Clinical Isolate

Resistance to the ceftazidime (CAZ)-avibactam (AVI) combination is increasingly being reported. Here, we report a CAZ-AVI-resistant Klebsiella pneumoniae strain belonging to the high-risk sequence type 307 (ST307) clone and producing Klebsiella pneumoniae carbapenemase 39 (KPC-39), a single-amino-acid variant of KPC-3 (A172T). Cloning experiments, steady-state kinetic parameters, and molecular dynamics simulations revealed a loss of carbapenemase activity and increased affinity for CAZ. KPC-39 was identified in a patient without prior exposure to CAZ-AVI, suggesting silent dissemination in European health care settings.

Ceftazidime/Avibactam-Resistant Klebsiella pneumoniae subsp. pneumoniae Isolates in a Tertiary Italian Hospital: Identification of a New Mutation of the Carbapenemase Type 3 (KPC-3) Gene Conferring Ceftazidime/Avibactam Resistance

Several Klebsiella pneumoniae carpabenemase (KPC) gene mutations are associated with ceftazidime/avibactam (CAZ-AVI) resistance. Here, we describe four Klebsiella pneumoniae subsp. pneumoniae CAZ-AVI-resistant clinical isolates, collected at the University Hospital of Tor Vergata, Rome, Italy, from July 2019 to February 2020. These resistant strains were characterized as KPC-3, having the transition from cytosine to thymine (CAC-TAC) at nucleotide position 814, with histidine that replaces tyrosine (H272Y). In addition, two different types of KPC gene mutations were detected. The first one, common to three strains, was the D179Y (G532T), associated with CAZ-AVI resistance. The second mutation, found only in one strain, is a new mutation of the KPC-3 gene: a transversion from thymine to adenine (CTG-CAG) at nucleotide position 553. This mutation causes a KPC variant in which glutamine replaces leucine (Q168L). None of the isolates were detected by a rapid immunochromatographic assay for detection of carbapenemase (NG Biotech, Guipry, France) and were unable to grow on a selective chromogenic medium Carba SMART (bioMerieux, Firenze, Italy). Thus, they escaped common tests used for the prompt detection of Klebsiella pneumoniae KPC-producing.

Ceftazidime/avibactam resistance is associated with different mechanisms in KPC-producing Klebsiella pneumoniae strains

This study focused on Klebsiella pneumoniae isolates that were resistant or had low susceptibility to a combination of ceftazidime/avibactam. We aimed to investigate the mechanisms underlying this resistance. A total of 24 multi-drug resistant isolates of K. pneumoniae were included in the study. The phenotypic determination of carbapenemase presence was based on the CARBA NP test. NG-Test CARBA 5 was also performed, and it showed KPC production in 22 out 24 strains. The molecular characterisation of blaKPC carbapenemase gene, ESBL genes (blaCTX-M, blaTEM, and blaSHV) and porin genes ompK35/36 was performed using the PCR. Finally, ILLUMINA sequencing was performed to determine the presence of genetic mutations.Various types of mutations in the KPC sequence, leading to ceftazidime/avibactam resistance, were detected in the analysed resistant strains. We observed that KPC-31 harboured the D179Y mutation, the deletion of the amino acids 167-168, and the mutation of T243M associated with ceftazidime/avibactam resistance. The isolates that did not present carbapenemase alterations were found to have other mechanisms such as mutations in the porins. The mutations both on the KPC-3 enzyme and in the porins confirmed, that diverse mechanisms confer resistance to ceftazidime/avibactam in K. pneumoniae.

Ceftazidime-avibactam: are we safe from class A carbapenemase producers' infections?

Recently, new combinations of β-lactams and β-lactamase inhibitors became available, including ceftazidime-avibactam, and increased the ability to treat infections caused by carbapenem-resistant Enterobacterales (CRE). Despite the reduced time of clinical use, isolates expressing resistance to ceftazidime-avibactam have been reported, even during treatment or in patients with no previous contact with this drug. Here, we detailed review data on global ceftazidime-avibactam susceptibility, the mechanisms involved in resistance, and the molecular epidemiology of resistant isolates. Ceftazidime-avibactam susceptibility remains high (≥ 98.4%) among Enterobacterales worldwide, being lower among extended-spectrum β-lactamase (ESBL) producers and CRE. Alterations in class A β-lactamases are the major mechanism involved in ceftazidime-avibactam resistance, and mutations are mainly, but not exclusively, located in the Ω loop of these enzymes. Modifications in Klebsiella pneumoniae carbapenemase (KPC) 3 and KPC-2 have been observed by many authors, generating variants with different mutations, insertions, and/or deletions. Among these, the most commonly described is Asp179Tyr, both in KPC-3 (KPC-31 variant) and in KPC-2 (KPC-33 variant). Changes in membrane permeability and overexpression of efflux systems may also be associated with ceftazidime-avibactam resistance. Although several clones have been reported, ST258 with Asp179Tyr deserves special attention. Surveillance studies and rationale use are essential to retaining the activity of this and other antimicrobials against class A CRE.

Increased gene expression and copy number of mutated blaKPC lead to high-level ceftazidime/avibactam resistance in Klebsiella pneumoniae

Background

Resistance to ceftazidime-avibactam was reported, and it is important to investigate the mechanisms of ceftazidime/avibactam resistance in K. pneumoniae with mutations in bla_KPC.

Results

We report the mutated bla_KPC is not the only mechanism related to CZA resistance, and investigate the role of outer porin defects, efflux pump, and relative gene expression and copy number of bla_KPC and ompk35/36. Four ceftazidime/avibactam-sensitive isolates detected wild type bla_KPC-2, while 4 ceftazidime/avibactam-resistant isolates detected mutated bla_KPC (bla_KPC-51, bla_KPC-52, and bla_KPC-33). Compared with other ceftazidime/avibactam-resistant isolates with the minimal inhibitory concentration of ceftazidime/avibactam ranging 128–256 mg/L, the relative gene expression and copy number of bla_KPC was increased in the isolate which carried bla_KPC-51 and also showed the highest minimal inhibitory concentration of ceftazidime/avibactam at 2048 mg/L. The truncated Ompk35 contributes rare to ceftazidime/avibactam resistance in our isolates. No significant difference in minimal inhibitory concentration of ceftazidime/avibactam was observed after the addition of PABN.

Conclusions

Increased gene expression and copy number of mutated bla_KPC can cause high-level ceftazidime/avibactam resistance.

Evolutionary Trajectories toward Ceftazidime-Avibactam Resistance in Klebsiella pneumoniae Clinical Isolates

From January 2019 to April 2020, 32 KPC-producing, ceftazidime-avibactam (CZA) resistant Klebsiella pneumoniae strains were isolated in a university hospital in Rome, Italy. These strains belonged to the ST512, ST101 and ST307 high-risk clones. Nine different CZA-resistant KPC-3 protein variants were identified, five of them never previously reported (KPC-66 to KPC-70). Among them, KPC-31, KPC-39, KPC-49, KPC-66, KP-68, KPC-69 and KPC-70 showed amino acid substitutions, insertions and deletions in the Ω loop of the protein. KPC-29 has the duplication, while the novel KPC-67 has the triplication of the KDD triplet in the 270-loop of the protein. Genomics performed on contemporary resistant and susceptible clones underlined that those novel mutations emerged in bla_KPC-3 genes located on conserved plasmids: in ST512, all bla_KPC-3 mutant genes were located in pKpQIL plasmids, while the three novel bla_KPC-3 mutants identified in ST101 were on FIIk-FIA(HI1)-R plasmids. Selection also promoted multiplication of the carbapenemase gene copy number by transposition, recombination, and fusion of resident plasmids. When expressed in Escherichia coli recipient cells cloned in the high-copy number pTOPO vector, the Ω loop mutated variants showed CZA-resistant phenotype associated with susceptibility to carbapenems, while KPC variants with insertions in the 270-loop showed residual activity on carbapenems. The investigation of CZA-resistance mechanisms offered the unique opportunity to study vertical, horizontal, and oblique evolutionary trajectories of K. pneumoniae high-risk clones.

Carbapenemase detection by NG-Test CARBA 5-a rapid immunochromatographic assay in carbapenem-resistant Enterobacterales diagnosis

Background

The global spread of carbapenem-resistant Enterobacterales (CRE) represents a serious public health concern as these organisms are associated with limited treatment options, high mortality rate and rapid transmissibility. The identification of carbapenemase remains a challenge in microbiological laboratories as no single method is perfect when considering cost, carbapenemase coverage, accuracy, handling complexity and TATs together.

Methods

NG-Test CARBA 5 assay and modified carbapenem inactivation method in conjunction with EDTA carbapenem inactivation method (mCIM/eCIM) were challenged with a collection of 299 molecularly characterized CRE isolates in China in order to evaluate the performance in detecting five major carbapenemases (bla_KPC, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48) among Enterobacterales.

Results

NG-Test CARBA 5 detected all KPC-, NDM-, VIM- and OXA-48-producing isolates perfectly with a weak false-positive signal for NDM in an IMP-4 producer, which makes the specificity for NDM decreases to 99.6%. The overall specificity/sensitivity were 99.9%/100% for NG-Test CARBA 5. mCIM/eCIM achieved high specificity of 100%/100% and sensitivity of 99.6%/97.4%, with one S. marcescens isolate harboring VIM-2 undetected.

Conclusions

Both NG-Test CARBA 5 and mCIM/eCIM showed excellent results in the tested carbapenemase (bla_KPC, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48) detection compared with molecular genotypic test. As every assay has its own limitations, suitable methods should be combined for the establishment of the CRE diagnostic pathways.

Resistance to ceftazidime/avibactam in infections and colonisations by KPC-producing Enterobacterales: a systematic review of observational clinical studies

OBJECTIVES

Ceftazidime/avibactam (CAZ-AVI), approved in 2015, is an important first-line option for Klebsiella pneumoniae carbapenemase-producing Enterobacterales (KPC-E). Although still uncommon, resistance to CAZ-AVI has emerged and may represent a serious cause of concern.

METHODS

We performed a systematic literature review of clinical and microbiological features of infections and colonisations by CAZ-AVI-resistant KPC-E, focused on the in vivo emergence of CAZ-AVI resistance in different clinical scenarios.

RESULTS

Twenty-three papers were retrieved accounting for 42 patients and 57 isolates, mostly belonging to K. pneumoniae ST258 harbouring D179Y substitution in the KPC enzyme. The USA, Greece and Italy accounted for 80% of cases. In one-third of isolates resistance was not associated with previous CAZ-AVI exposure. Moreover, 20% of the strains were colistin-resistant and 80% were extended-spectrum β-lactamase (ESBL)-producers. The majority of infected patients had severe underlying diseases (39% cancer, 22% solid-organ transplantation) and 37% died. The abdomen, lung and blood were the most involved infection sites. Infections by CAZ-AVI-resistant strains were mainly treated with combination therapy (85% of cases), with meropenem being the most common (65%) followed by tigecycline (30%), gentamicin (25%), colistin (25%) and fosfomycin (10%). Despite the emergence of resistance, 35% of patients received CAZ-AVI.

CONCLUSION

Taken together, these data highlight the need for prompt susceptibility testing including CAZ-AVI for Enterobacterales, at least in critical areas. Resistance to CAZ-AVI is an urgent issue to monitor in order to improve both empirical and targeted CAZ-AVI use as well as the management of patients with infections caused by CAZ-AVI-resistant strains.

KPC-53, a KPC-3 Variant of Clinical Origin Associated with Reduced Susceptibility to Ceftazidime-Avibactam

This study reports on the characterization of a Klebsiella pneumoniae clinical isolate showing high-level resistance to ceftazidime-avibactam associated with the production of KPC-53, a KPC-3 variant exhibiting a Leu167Glu168 duplication in the Ω-loop and a loss of carbapenemase activity. Whole-genome sequencing (WGS) revealed the presence of two copies of bla _KPC-53, located on a pKpQIL-like plasmid and on a plasmid prophage of the Siphoviridae family, respectively. The present findings provide new insights into the mechanisms of resistance to ceftazidime-avibactam.

RESIST-5 O.O.K.N.V. and NG-Test Carba 5 assays for the rapid detection of carbapenemase-producing Enterobacterales from positive blood cultures: a comparative study

We prospectively compared the performance of RESIST-5 O.O.K.N.V. and NG-Test Carba 5 assays directly from blood cultures spiked with 130 characterized Enterobacterales isolates. Overall, both assays yielded 100% sensitivity to detect KPC-type carbapenemases and OXA-48-like carbapenemases. Both assays failed to detect KPC-31 and KPC-33, D179Y point mutation variants of KPC-3 and KPC-2, that are deprived of carbapenemase activity and confer resistance to ceftazidime-avibactam. On blood culture bacterial pellets, NDM- and VIM-type carbapenemases were detected in 50.0% and 52.2%, respectively, by RESIST-5 O.O.K.N.V. vs 100% by NG-Test Carba 5. The sensitivity of RESIST-5 O.O.K.N.V. improved to 100% and 95.6%, respectively, by performing the assay on 4-h early subculture.

Improvement of the Immunochromatographic NG-Test Carba 5 Assay for the Detection of IMP Variants Previously Undetected

Here, we evaluated the immunochromatographic assay NG-Test Carba 5v2 (NG-Biotech), with improved IMP variant detection on 31 IMP producers, representing the different branches of the IMP phylogeny, including 32 OXA-48, 19 KPC, 12 VIM, 14 NDM, and 13 multiple carbapenemase producers (CPs), 13 CPs that were not targeted, and 13 carbapenemase-negative isolates. All tested IMP variants were accurately detected without impairing detection of the other carbapenemases. Thus, NG-Test Carba 5v2 is now well adapted to countries with high IMP prevalence and to the epidemiology of CP-Pseudomonas aeruginosa, where IMPs are most frequently detected.

Rapid microbiological tests for bloodstream infections due to multidrug resistant Gram-negative bacteria: therapeutic implications

BACKGROUND

Treating severe infections due to multidrug-resistant Gram-negative bacteria (MDR-GNB) is one of the most important challenges for clinicians worldwide, partly because resistance may remain unrecognized until identification of the causative agent and/or antimicrobial susceptibility testing (AST). Recently, some novel rapid test for identification and/or AST of MDR-GNB from positive blood cultures or the blood of patients with bloodstream infections (BSIs) have become available.

OBJECTIVES

The objective of this narrative review is to discuss the advantages and limitations of different rapid tests for identification and/or AST of MDR-GNB from positive blood cultures or the blood of patients with BSI, as well as the available evidence on their possible role to improve therapeutic decisions and antimicrobial stewardship.

SOURCES

Inductive PubMed search for publications relevant to the topic.

CONTENT

The present review is structured in the following way: (a) rapid tests on positive blood cultures; (b) rapid tests directly on whole blood; (c) therapeutic implications.

IMPLICATIONS

Novel molecular and phenotypic rapid tests for identification and AST show the potential for favourably influencing patients' outcomes and results of antimicrobial stewardship interventions by reducing both the time to effective treatment and the misuse of antibiotics, although the interpretation about their impact on actual therapeutic decisions and patients' outcomes is still complex. Factors such as feasibility and personnel availability, as well as the detailed knowledge of the local microbiological epidemiology, need to be considered very carefully when implementing novel rapid tests in laboratory workflows and algorithms. Providing high-level, comparable evidence on the clinical impact of rapid identification and AST is becoming of paramount importance for MDR-GNB infections, since in the near future rapid identification of specific resistance mechanisms could be crucial for guiding rapid, effective, and targeted therapy against specific resistance mechanisms.

CTX-M-33, a CTX-M-15 derivative conferring reduced susceptibility to carbapenems

CTX-M-type extended-spectrum ß-lactamases (ESBL) are widespread among Enterobacterales worldwide. The most common variant is CTX-M-15 hydrolyzing ceftazidime at high rate, but sparing carbapenems. We identified here CTX-M-33, a point mutant derivative of CTX-M-15 (Asp to Ser substitution at Ambler position 109), exhibiting a low carbapenemase activity. ß-Lactamase CTX-M-33 was identified in a Klebsiella pneumoniae isolate belonging to ST405, lacking the outer membrane protein OmpK36, that was resistant to broad-spectrum cephalosporins and ß-lactam/ß-lactamase inhibitor combinations, and displayed a decreased susceptibility to carbapenems. Comparative hydrolytic activity assays showed that CTX-M-33 hydrolyzed ceftazidime at a lower level than CTX-M-15, but significantly hydrolyzed meropenem. In addition, CTX-M-33 showed higher Mutant Prevention Concentration values and wider mutant selection window in presence of meropenem, in accordance with its observed hydrolytic properties. We identified here the very first CTX-M enzyme possessing a weak carbapenemase activity, that may correspond to an emerging phenomenon when considering its possibility to evolve from the widespread ESBL CTX-M-15.