Emergence of Ceftazidime/Avibactam and Tigecycline Resistance in Carbapenem-Resistant Klebsiella pneumoniae Due to In-Host Microevolution

Epidemiology of carbapenem-resistant Klebsiella pneumoniae in China and the evolving trends of predominant clone ST11: a multicentre, genome-based study

OBJECTIVES

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major nosocomial infectious pathogen with rapidly increasing prevalence. The genomic epidemiological characteristics of CRKP nationwide, especially the evolving trends within the predominant clones, should be evaluated clearly.

METHODS

We collected 3415 K. pneumoniae strains from 28 hospitals across China. Antimicrobial susceptibility testing and WGS were performed. Subsequent genomic analyses, including sequence typing, K-locus (KL) identification, antimicrobial resistance gene screening, and virulence score assessment were performed. The phylogenetic relationship of clonal group 11 was determined based on core-genome analysis, and the presence of the pLVPK-like virulence plasmid in ST11 isolates was confirmed using plasmid core-gene analysis. Additionally, the trends of the ST11 lineage with different KL types on a global scale were investigated using Beast2.

RESULTS

Of the K. pneumoniae strains, 708 were identified as CRKP isolates (20.7%), of which 97.7% were MDR. ST11 was the predominant clone, and KPC-2 was the prevalent carbapenemase in China, although the prevalence of specific clones and carbapenemases varied by geographic region. Among ST11 isolates, KL47 and KL64 were the predominant KL types, and KL64 gradually replaced KL47, with a higher percentage of KL64 isolates harbouring the pLVPK-like plasmid. Global genome data showed a significant increase in the effective population size of KL64 over the last 5 years.

CONCLUSIONS

The prevalence of CRKP was very high in certain regions in China. The increasing convergence of virulence and resistance, particularly in ST11-KL64 isolates, should be given more attention and further investigation.

A large-scale surveillance revealed that KPC variants mediated ceftazidime-avibactam resistance in clinically isolated Klebsiella pneumoniae

To monitor the resistance rate and gain a deeper understanding of the resistance mechanisms, we conducted over a 2-year surveillance focusing on the Klebsiella pneumoniae associated with the clinical usage of ceftazidime-avibactam (CZA) in a teaching hospital. A total of 4,641 K. pneumoniae isolates were screened to identify the CZA resistance through antimicrobial susceptibility testing. Comprehensive analyses, including homology analysis, conjugation experiments, clone assays, and whole genome sequencing, were furtherly performed on the CZA-resistant strains. In total, four CZA-resistant K. pneumoniae (CZA-R-Kp) strains were separated from four patients, in which three of them received CZA treatment during the hospitalization, accounting for a 4% (3/75) resistance development rate of K. pneumoniae under CZA stress. All CZA-R-Kp isolates were found to possess variants of blaKPC-2. The identified mutations included blaKPC-33, blaKPC-86, and a novel variant designated as blaKPC-129, all of which were located in the Ω loop of the KPC enzyme. These mutations were found to impact the amino acid sequence and spatial structure of the enzyme's active center, consequently affecting KPC carbapenemase activity. This study underscores the importance of active surveillance to monitor the emergence of resistance to CZA, highlighting the need for ongoing research to develop effective strategies for combating antimicrobial resistance. Understanding the mechanisms behind resistance is crucial in maintaining the efficacy of CZA, a vital tool in the battle against multidrug-resistant infections.IMPORTANCEAs an effective drug for the treatment of carbapenem-resistant Klebsiella pneumoniae, ceftazidime-avibactam (CZA) began to develop resistance in recent years and showed an increasing trend. In order to effectively monitor the resistance rate of CZA and understand its resistance mechanism, we monitored K. pneumoniae for more than 2 years to find CZA-resistant strains. Through comprehensive analysis of the selected CZA-resistant strains, it was found that all the CZA-resistant strains had mutation, which could affect the activity of KPC carbapenemase. This study highlights the importance of proactive surveillance to monitor the emergence of CZA resistance, which highlights the need for ongoing research to develop effective strategies to combat antimicrobial resistance. Understanding the mechanisms behind resistance is critical to maintaining the effectiveness of CZA, an important tool in the fight against multidrug-resistant infections.

Retrospective Tertiary Care-Based Cohort Study on Clinical Characteristics and Outcomes of Ceftazidime-Avibactam-Resistant Carbapenem-Resistant Klebsiella pneumoniae Infections

Introduction

The advent of ceftazidime-avibactam (CAZ-AVI)-resistant carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates has been steadily documented in recent years. We aimed to identify risk factors of CAZ-AVI-resistant CRKP infection and assess clinical outcomes of patients.

Methods

The study retrospectively examined the clinical and microbiological data of patients with ceftazidime avibactam susceptible and ceftazidime avibactam-resistant Klebsiella pneumonia carbapenem-resistant enterobacteriaceae infection to identify risk factors, clinical features, and outcomes using multivariate logistic regression analysis.

Results

A total of 152 patients with CRKP infection were enrolled in this study. Patients with CAZ-AVI-resistant CRKP isolates (20/34 = 58.8%) had prior exposure to carbapenems (p=0.003) and had more tracheostomies (16/34 = 47.1%) (p=0.001). Only 8/28 (28.6%) patients with CAZ-AVI susceptible CRKP isolates died amongst those administered ceftazidime-avibactam compared to 49/90 (54.4%) who did not receive the same (p=0.016). 1/9 (11.1%) patients with CAZ-AVI-resistant CRKP isolates who received colistin died compared to 13/25 (52%) who did not receive colistin (p=0.03). There was no association between presence of CAZ-AVI-resistant CRKP isolates and overall mortality (odds ratio: 0.7; 95% CI: 0.3, 1.6), and no independent predictors of risk factors to overall mortality in the group with CAZ-AVI-resistant CRKP isolates were noted.

Conclusion

Early advent of CAZ-AVI resistance in CRE isolates highlights the dynamic necessity of routine CAZ-AVI resistance laboratory testing and antimicrobial stewardship programmes focusing on the utilization of all antibiotics. Consolidating the hospital infection control of tracheostomies may help to prevent CAZ resistance in CRKP. Colistin may aid in decreasing of mortality rates among patients with CAZ-AVI CRKP isolates.

Plasmid-encoded gene duplications of extended-spectrum β-lactamases in clinical bacterial isolates

Introduction

The emergence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is an urgent and alarming One Health problem. This study aimed to investigate duplications of plasmid-encoded ESBL genes and their impact on antimicrobial resistance (AMR) phenotypes in clinical and screening isolates.

Methods

Multi-drug-resistant bacteria from hospitalized patients were collected during routine clinical surveillance from January 2022 to June 2023, and their antimicrobial susceptibility patterns were determined. Genotypes were extracted from long-read whole-genome sequencing data. Furthermore, plasmids and other mobile genetic elements associated with ESBL genes were characterized, and the ESBL genes were correlated to ceftazidime minimal inhibitory concentration (MIC).

Results

In total, we identified four cases of plasmid-encoded ESBL gene duplications that match four genetically similar plasmids during the 18-month surveillance period: five Escherichia coli and three Klebsiella pneumoniae isolates. As the ESBL genes were part of transposable elements, the surrounding sequence regions were duplicated as well. In-depth analysis revealed insertion sequence (IS)-mediated transposition mechanisms. Isolates with duplicated ESBL genes exhibited a higher MIC for ceftazidime in comparison to isolates with a single gene copy (3-256 vs. 1.5-32 mg/L, respectively).

Conclusion

ESBL gene duplications led to an increased phenotypic resistance against ceftazidime. Our data suggest that ESBL gene duplications by an IS-mediated transposition are a relevant mechanism for how AMR develops in the clinical setting and is part of the microevolution of plasmids.

Genome sequencing unveils blaKPC-2-harboring plasmids as drivers of enhanced resistance and virulence in nosocomial Klebsiella pneumoniae

The threat posed by Klebsiella pneumoniae in healthcare settings has worsened due to the evolutionary advantages conferred by blaKPC-2-harboring plasmids (pKPC-2). However, the specific evolutionary pathway of nosocomial K. pneumoniae carrying pKPC-2 and its transmission between patients and healthcare environments are not yet well understood. Between 1 August and 31 December 2019, 237 ST11 KPC-2-producing-carbapenem-resistant K. pneumoniae (CRKP) (KPC-2-CRKP) were collected from patient or ward environments in an intensive care unit and subjected to Illumina sequencing, of which 32 strains were additionally selected for Nanopore sequencing to obtain complete plasmid sequences. Bioinformatics analysis, conjugation experiments, antimicrobial susceptibility tests, and virulence assays were performed to identify the evolutionary characteristics of pKPC-2. The pKPC-2 plasmids were divided into three subgroups with distinct evolutionary events, including Tn3-mediated plasmid homologous recombination, IS26-mediated horizontal gene transfer, and dynamic duplications of antibiotic resistance genes (ARGs). Surprisingly, the incidence rates of multicopy blaKPC-2, blaSHV-12, and blaCTX-M-65 were quite high (ranging from 27.43% to 67.01%), and strains negative for extended-spectrum β-lactamase tended to develop multicopy blaKPC-2. Notably, the presence of multicopy blaSHV-12 reduced sensitivity to ceftazidime/avibactam (CZA), and the relative expression level of blaSHV-12 in the CZA-resistant group was 6.12 times higher than that in the sensitive group. Furthermore, a novel hybrid pKPC-2 was identified, presenting enhanced virulence levels and decreased susceptibility to CZA. This study emphasizes the notable prevalence of multicopy ARGs and provides a comprehensive insight into the intricate and diverse evolutionary pathways of resistant plasmids that disseminate among patients and healthcare environments.IMPORTANCEThis study is based on a CRKP screening program between patients and ward environments in an intensive care unit, describing the pKPC-2 (blaKPC-2-harboring plasmids) population structure and evolutionary characteristics in clinical settings. Long-read sequencing was performed in genetically closely related strains, enabling the high-resolution analysis of evolution pathway between or within pKPC-2 subgroups. We revealed the extremely high rates of multicopy antibiotic resistance genes (ARGs) in clinical settings and its effect on resistance profile toward novel β-lactam/β-lactamase inhibitor combinations, which belongs to the last line treatment choices toward CRKP infection. A novel hybrid pKPC-2 carrying CRKP with enhanced resistance and virulence level was captured during its clonal spread between patients and ward environment. These evidences highlight the threat of pKPC-2 to CRKP treatment and control. Thus, surveillance and timely disinfection in clinical settings should be practiced to prevent transmission of CRKP carrying threatful pKPC-2. And rational use of antibiotics should be called for to prevent inducing of pKPC-2 evolution, especially the multicopy ARGs.

In vitro Activity of Cefepime/Avibactam Against Carbapenem Resistant Klebsiella pneumoniae and Integrative Metabolomics-Proteomics Approach for Resistance Mechanism: A Single-Center Study

Purpose

We aimed to evaluate the in vitro antibacterial effects of combination of cefepime/avibactam against carbapenem-resistant Klebsiella pneumonia (CRKP) and explore the resistance mechanism of FEP/AVI.

Patients and Methods

This study explored the in vitro antibacterial activities of ceftazidime/avibactam (CAZ/AVI) and cefepime/avibactam (FEP/AVI) against 40 and 76 CRKP clinical isolates. Proteomics and metabolomics were employed to investigate the resistance mechanisms of CRKP to FEP/AVI.

Results

FEP/AVI (MIC50/MIC90 0.5/4-64/4 μg/mL, resistance rate 17.1%) showed better antibacterial activity against CRKP than CAZ/AVI (MIC50/MIC90 4/4-128/4 μg/mL, resistance rate 20%) in vitro. Bioinformatics analysis showed that the differentially expressed proteins (DEPs) were enriched in alanine, aspartate and glutamate metabolism, and ribosome. Remarkably, transcriptional and translational activity-related pathways were inhibited in FEP/AVI resistant CRKP. Overlap analysis suggested that H-NS might play an important role in resistance to FEP/AVI in CRKP. The mRNA levels of DEPs-related genes (adhE, gltB, purA, ftsI and hns) showed the same trends as DEPs in FEP/AVI susceptible and resistant strains. FEP/AVI resistant isolates demonstrated stronger biofilm formation capacity than susceptible isolates. Metabolomics results showed that disturbed metabolites were mainly lipids, and adenine was decreased in FEP/AVI resistant CRKP.

Conclusion

These results indicated that H-NS, GltB and SpoT may directly or indirectly promote biofilm formation of CRKP and led to FEP/AVI resistance, but inhibited ribosomal function. Our study provides a mechanistic insight into the acquisition of resistance to FEP/AVI in Klebsiella pneumoniae.

Preference of Bacterial Rhamnosyltransferases for 6-Deoxysugars Reveals a Strategy To Deplete O-Antigens

Bacteria synthesize hundreds of bacteria-specific or "rare" sugars that are absent in mammalian cells and enriched in 6-deoxy monosaccharides such as l-rhamnose (l-Rha). Across bacteria, l-Rha is incorporated into glycans by rhamnosyltransferases (RTs) that couple nucleotide sugar substrates (donors) to target biomolecules (acceptors). Since l-Rha is required for the biosynthesis of bacterial glycans involved in survival or host infection, RTs represent potential antibiotic or antivirulence targets. However, purified RTs and their unique bacterial sugar substrates have been difficult to obtain. Here, we use synthetic nucleotide rare sugar and glycolipid analogs to examine substrate recognition by three RTs that produce cell envelope components in diverse species, including a known pathogen. We find that bacterial RTs prefer pyrimidine nucleotide-linked 6-deoxysugars, not those containing a C6-hydroxyl, as donors. While glycolipid acceptors must contain a lipid, isoprenoid chain length, and stereochemistry can vary. Based on these observations, we demonstrate that a 6-deoxysugar transition state analog inhibits an RT in vitro and reduces levels of RT-dependent O-antigen polysaccharides in Gram-negative cells. As O-antigens are virulence factors, bacteria-specific sugar transferase inhibition represents a novel strategy to prevent bacterial infections.

In vivo adaptive antimicrobial resistance in Klebsiella pneumoniae during antibiotic therapy

Klebsiella pneumoniae is one of the leading pathogens contributing to antimicrobial resistance. The emergence of carbapenem-resistant K. pneumoniae (CRKP) has put the use of clinical antimicrobial agents in a dilemma. In particular, CRKP exhibiting resistance to ceftazidime/avibactam, tigecycline and colistin have raised great clinical concern, as these are the last-resort antibiotics for the treatment of CRKP infections. Within-host evolution is a survival strategy closely related to the emergence of antimicrobial resistance, while little attention has been paid to the in vivo genetic process of conversion from antibiotic-susceptible to resistant K. pneumoniae. Here we have a literature review regarding the in vivo evolution of resistance to carbapenems, ceftazidime/avibactam, tigecycline, and colistin in K. pneumoniae during antibacterial therapy, and summarized the detailed resistance mechanisms. In general, acquiring blaKPC and blaNDM harboring-plasmid, specific mutations in blaKPC, and porin genes, such as ompK35 and ompK36, upregulation of blaKPC, contribute to the development of carbapenem and ceftazidime/avibactam resistance in vivo. Overexpression of efflux pumps, acquiring plasmid-carrying tet (A) variants, and ribosomal protein change can lead to the adaptive evolution of tigecycline resistance. Specific mutations in chromosomes result in the cationic substitution of the phosphate groups of lipid A, thus contributing to colistin resistance. The resistant plasmid might be acquired from the co-infecting or co-colonizing strains, and the internal environment and antibiotic selection pressure contribute to the emergence of resistant mutants. The internal environment within the human host could serve as an important source of resistant K. pneumoniae strains.

Identification of KPC-112 from an ST15 Klebsiella pneumoniae Strain Conferring Resistance to Ceftazidime-Avibactam

Ceftazidime-avibactam is an effective antibiotic combination of a β-lactam and a β-lactamase inhibitor against Klebsiella pneumoniae-carbapenemase (KPC)-producing Enterobacterales. Despite a relatively low resistance rate, reports of resistance to ceftazidime-avibactam mainly caused by the mutations in KPC have increased in recent years. Here, we report a ceftazidime-avibactam-resistant and carbapenem-susceptible Klebsiella pneumoniae strain carrying a novel KPC variant, KPC-112, which differs from KPC-2 by 4-amino-acid deletions at Ambler positions 166L/167E and 242G/243T. The isolate was identified as K. pneumoniae by a Vitek mass spectrometer (bioMérieux, France). The MICs of antimicrobial agents were determined using broth microdilution susceptibility method. The result showed that the isolate was resistant to ceftazidime-avibactam (MIC = >128 mg/L) but susceptible to imipenem (MIC = 0.5 mg/L), meropenem (MIC = 1 mg/L), and tigecycline (MIC = 2 mg/L). The carbapenemase genes were confirmed by PCR-based sequencing. Plasmid transformation assay showed that the bla_KPC-112-positive transformant increased MICs of ceftazidime-avibactam, ceftazidime, and cefepime by at least 256-fold, 128-fold, and 128-fold, respectively, compared with the recipient Escherichia coli DH5α. According to the whole-genome sequencing analysis, many common resistance genes were identified, including bla_KPC-112, bla_OXA-1, bla_CTX-M-15, bla_TEM-1B, bla_SHV-28, aac(6')Ib-cr, aac(3)-IId, qnrS1, catA2, catB4, and fosA6, and mutations of GyrA (GyrA-83F and GyrA-87A) and ParC (ParC-80I) were also found. Overall, our study highlights the importance of monitoring susceptibility during ceftazidime-avibactam treatment and accurate detection of KPC variants. IMPORTANCE Carbapenem-resistant Enterobacterales (CRE) are one of the most serious antimicrobial resistance problems in the world, listed as an "urgent" threat by the U.S. Centers for Disease Control and Prevention. Among CRE, K. pneumoniae-carbapenemase-producing Klebsiella pneumoniae (KPC-KP) has become a significant health threat due to its rapid transmissibility and high mortality. With the wider clinical use of ceftazidime-avibactam, reports of resistance have increased in recent years even though the overall resistance rate remains relatively low. Among the reported resistance mechanisms are mainly mutations derived from the bla_KPC-2 or bla_KPC-3 gene. Here, we describe the characterization of a ceftazidime-avibactam-resistant bla_KPC-112-positive K. pneumoniae clinical isolate for the first time. A number of Enterobacteriaceae isolates producing these kinds of KPC variants might be missed by conventional antimicrobial susceptibility testing (AST) methods and lead to irrational drug use. So, this study of KPC-112 will help to establish the diversity of KPCs and remind researchers of the challenge of drug resistance and detection brought by the KPC variants.

Emergence of Ceftazidime-Avibactam Resistance and Decreased Virulence in Carbapenem-Resistant ST11 Klebsiella pneumoniae During Antibiotics Treatment

INTRODUCTION

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to human public health. Ceftazidime-avibactam (CZA) is currently one of the few effective antibiotics for carbapenem-resistant Enterobacteriaceae (CRE).

METHODS AND RESULTS

Here, we analyzed two longitudinal Klebsiella pneumoniae clinical isolates (FK8578, FK8695) that were isolated from an ICU patient during antimicrobial treatment. Broth microdilution method, whole-genome sequencing (WGS) and comparative genomic analysis were used to elucidate the dynamics and mechanisms of antibiotic resistance. String test, quantification of capsule, biofilm inhibition test and Galleria mellonella (G. mellonella) infection model were used to explore the changes in virulence of the two clinical isolates. During antibiotic treatment, CRKP FK8578 underwent a series of drug resistance and virulence changes, including CZA resistance, carbapenem susceptibility and virulence attenuation. The results of WGS showed that mutation of bla KPC-2 to bla KPC-33 was responsible for the change of drug resistance phenotype between FK8578 and FK8695. pLVPK-like virulence plasmid without siderophore synthesis operon was identified in the two strains. On the other hand, the loss of hypermucoviscosity phenotype in the FK8695 strain may be related to a single nucleotide deletion of the rmpA gene, which would further lead to a decrease in virulence. Virulence results showed that compared with FK8578, FK8695 was negative in the string test, with decreased capsular production, smaller amounts of biofilm formation and higher survival rate of G. mellonella.

CONCLUSION

This is the first report of CZA resistance and decreased virulence in ST11 CRKP strains during antimicrobial treatment. It is urgent to monitor CZA resistance and timely adjust anti-infective treatment strategies.

Emergence of a Novel NDM-5-Producing Sequence Type 4523 Klebsiella pneumoniae Strain Causing Bloodstream Infection in China

Klebsiella pneumoniae is a significant infectious pathogen that causes bloodstream infections. This study aimed to genetically characterize a novel sequence type 4523 (ST4523) multidrug-resistant (MDR) K. pneumoniae strain recovered from the blood of a 79-year-old Chinese female patient with severe pneumonia and chronic obstructive pulmonary disease who ultimately died of the infection. The susceptibility testing results showed that strain 18SHX180 is nonsusceptible to cephalosporin, carbapenems, combinations of β-lactam and β-lactamase inhibitors, levofloxacin, and colistin and is only susceptible to amikacin. The phylogenetic structure showed that strain 18SHX180 belongs to a novel sequence type, ST4523, and capsule serotype K111. ST4523 is closely related to ST11, the most dominant clone of clinical carbapenem-resistant K. pneumoniae in China. ST4523 has 2 single-base variants in mdh and phoE. 18SHX180 showed medium virulence in Galleria mellonella and a mouse intraperitoneal infection model. PacBio Sequel and Illumina sequencing were performed to analyze the genetic characterization of 18SHX180, which contains 2 plasmids (pSHX180-NDM5 and pSHX180-1). pSHX180-NDM5 exhibits 86% coverage and 100% identity with 3 blaNDM-5-carrying plasmids and contains an additional region coding for the frmRAB operon, which permits bacteria to sense and detoxify formaldehyde. pSHX180-1 is responsible for the MDR phenotype: it carries 11 categories of genes for antimicrobial resistance [aadA16, aph(3″)-Ib, aph(6)-Id, blaSHV-182, blaTEM-1A, qacE, aac(6')-Ib-cr, mph(A), floR, qnrB6, arr-3, sul, sul2], all of which are associated with transposons and integrons located in three accessory resistance regions. The novel ST4523 K. pneumoniae strain could threaten the control of antimicrobial resistance, and its discovery calls attention to the genetic evolution of bacteria. IMPORTANCE Klebsiella pneumoniae is a significant infectious pathogen causing bloodstream infections. Due to the dissemination of carbapenemase genes, the incidence of carbapenem-resistant K. pneumoniae (CRKP) has increased, with high morbidity and mortality rates in immunocompromised patients. Here, we reported a novel ST4523 blaNDM-5-bearing CRKP strain initially recovered from a 79-year-old female who died of both a lower respiratory tract infection and bloodstream infection. We also describe the genetic and phenotypic characteristics of this strain. This study provides important insights into the genetic evolution of ST11 K. pneumoniae.