Molecular characterization of carbapenem-resistant Klebsiella pneumoniae isolates with focus on antimicrobial resistance

Delving into Macrolide Binding Affinities and Associated Structural Modulations in Erythromycin Esterase C: Insights into the Venus Flytrap Mechanism

Since their inception in antibacterial therapy, macrolide-based antibiotics have significantly shaped the evolutionary pathways of pathogenic bacteria, driving them to develop diverse antimicrobial resistance (AMR) mechanisms. Among these, macrolide esterase, commonly referred to as erythromycin esterase, emerged as a critical defense mechanism, enabling bacteria to detoxify macrolides by hydrolyzing the macrolactone ring within the bacterial cell. In this study, we delve into the intricate interactions and conformational dynamics of erythromycin esterase C (EreC), a key member of the Ere enzyme family. We have focused on three FDA-approved and widely prescribed macrolides─erythromycin, clarithromycin, and azithromycin─by employing classical molecular dynamics, absolute binding free energy calculations, and 2D well-tempered metadynamics simulations to explore their interactions with EreC. To estimate the absolute binding free energies, we have used the recently developed and robust "Streamlined Alchemical Free Energy Perturbation (SAFEP)" protocol. The results from our molecular dynamics simulations and advanced analyses portrayed the crucial role of hydrophobic interactions within the macrolide binding cleft of EreC, along with the significant influence of the minor lobe in facilitating overall structural fluctuation. In silico alanine scanning identified top three hydrophobic residues, i.e., PHE248, MET333, and PHE344, responsible for macrolide binding inside that cleft. According to the free energy calculations, azithromycin and clarithromycin showed greater binding affinities toward EreC than the parent macrolide erythromycin. Moreover, 2D metadynamics simulations along with graph theory-based eigenvector centrality analyses revealed a metastable "semiopen" state during the hypothesized "active loop closure" of the EreC protein triggered by subtle conformational changes of an important histidine residue, HIS289, upon macrolide capture, drawing a fascinating parallel to the renowned "Venus flytrap" mechanism.

Risk Factors for Multidrug Resistance in Patients Infected with Carbapenem-Resistant Klebsiella pneumoniae: A Nomogram

Purpose

Our aim was to determine the risk factors for multidrug resistance in patients with carbapenem-resistant Klebsiella pneumoniae (CRKP).

Methods

The information of 196 patients with Klebsiella pneumoniae infection was collected. The patients were subsequently assigned to the carbapenem-resistant, multidrug-resistant, and non-multidrug-resistant groups. The risk factors for multidrug resistance in CRKP patients were assessed via least absolute shrinkage and selection operator and logistic regression analyses. Moreover, a nomogram was constructed dependent on the identified risk factors, and calibration and decision curves were plotted to detect its accuracy.

Results

Length of stay (LOS) [odds ratio (OR) and 95% confidence interval (CI): 4.558 (1.157-17.961), P = 0.030], intensive care unit (ICU) stay within 30 days [OR and 95% CI: 12.643 (3.780-42.293), P < 0.001], Glasgow Coma Scale (GCS) score [OR and 95% CI: 13.569 (2.738-67.236), P = 0.001], fungal infection [OR and 95% CI: 6.398 (1.969-20.785), P = 0.002], and cardiovascular disease (CVD) [OR and 95% CI: 3.871 (1.293-11.592), P = 0.016] were identified as risk factors for multidrug resistance in CRKP patients. The concordance index (C-index) of the constructed nomogram was 0.950 (95% CI: 0.945-0.955). Moreover, decision curve analysis elucidated the nomogram utilization across a wide range of probability thresholds, ranging from 1% to 100%. Finally, internal validation using random data validated the robustness of the predictive model, yielding a C-index of 0.937.

Conclusion

The LOS, ICU stay within 30 days, GCS score, fungal infection, and CVD were recognized as risk factors for multidrug resistance in CRKP patients. The constructed nomogram could accurately predict multidrug-resistant CRKP infections in patients.

Clinical and genomic characterization of carbapenem-resistant Enterobacterales bloodstream infections in patients with hematologic malignancies

Background

Carbapenem-resistant Enterobacterales (CRE) bloodstream infections (BSIs) pose a significant risk to patients with hematologic malignancies, yet the distinct features and outcomes of these infections are not thoroughly understood.

Methods

This retrospective study examined the characteristics and clinical outcomes of patients with Enterobacterales BSIs at the Hematology Department of Fujian Medical University Union Hospital from 2018 to 2022. Whole-genome sequencing was conducted on 45 consecutive CRE BSI isolates during this period.

Results

A total of 301 patients with Enterobacterales BSIs were included, with 65 (21.6%) cases of CRE and 236 (78.4%) cases of carbapenem-susceptible Enterobacterales (CSE). CRE infections accounted for 16.9% to 26.9% of all Enterobacterales BSIs, and carbapenem-resistant Klebsiella pneumoniae (CRKP) was the predominant strain. The most frequent sequence type (ST) and carbapenemase among CRKP were ST11 (68.6%) and blaKPC-2 (80.0%), respectively. Perianal infections, multiple infection foci, and a history of multiple hospitalizations, ICU stays, and prior CRE infections were identified as risk factors for CRE BSIs. Patients in the CRE group experienced significantly higher proportions of infection-related septic shock (43.1% vs. 19.9%, P < 0.0003) and 30-day all-cause mortality (56.9% vs. 24.6%, P < 0.0001) compared to those in the CSE group. Patient's age and disease subtypes, strain subtypes, and antimicrobial treatment regimens significantly influenced survival in patients with CRE BSIs.

Conclusions

CRE BSIs are a frequent complication in patients with hematological malignancies undergoing treatment and are associated with poor survival rates. A comprehensive understanding of risk factors and ongoing surveillance of prevalent strains are essential for the effective management of these infections.

Development of a quadruple qRT-PCR assay for simultaneous identification of hypervirulent and carbapenem-resistant Klebsiella pneumoniae

IMPORTANCE

Globally, the increasing number of hypervirulent Klebsiella pneumoniae (hvKp) and carbapenem-resistant Kp (CR-Kp) infections poses a huge public health challenge with high morbidity and mortality. Worrisomely, due to the mobility of elements carrying virulence and drug-resistance genes, the increasing prevalence of CR-hvKp has also been found with an overwhelming mortality rate in recent years. However, the current detection methods for hvKp and CR-Kp have many disadvantages, such as long turnaround time, complex operation, low sensitivity, and specificity. Herein, a more sensitive, rapid, single-reaction, and multiplex quantitative real-time PCR was developed and validated to differentiate the circulating lineages of Kp with excellent performance in sensitivity and specificity, providing a useful tool for the differential diagnosis and the surveillance of the circulating Kp.

Survival of clinical and environmental carbapenem-resistant Klebsiella pneumoniae ST147 in surface water

Carbapenem-resistant Klebsiella pneumoniae represents a healthcare threat, already disseminated in the environment. This study aimed to compare the behaviour of a clinical and an environmental K. pneumoniae strain (multilocus sequence type ST147) harbouring the gene blaKPC-3 in water. The abundance of the genes phoE (specific for K. pneumoniae) and blaKPC-3 was monitored by quantitative PCR in urban runoff water and sterile ultra-pure water microcosms, aiming to assess survival, blaKPC-3 persistence, and the effect of the native water microbiota. In sterile ultra-pure water, the abundance of cultivable K. pneumoniae and blaKPC-3 gene did not change over the incubation period (8 days). In contrast, in urban runoff, the K. pneumoniae and the genes phoE and blaKPC genes decreased by up to 3 log-units. These results suggest that K. pneumoniae were outcompeted by the native microbiota of the urban runoff water and that the decay of blaKPC-3 gene was due to host death, rather than to gene loss. The study highlights that although native microbiota is essential to hamper the persistence of non-native bacteria, carbapenemase producing K. pneumoniae can survive in urban runoff water for at least one week.

Draft genome sequence of Enterobacter cloacae ST473 harbouring blaCMH-3 isolated from a human patient diagnosed with recurrent bacteriuria in Nigeria

Enterobacter cloacae is among the most frequently isolated species described in clinical infections and is commonly associated with a multidrug resistance (MDR) phenotype. We present the draft genome sequence of a MDR E. cloacae isolated in Nigeria from the urine sample of an adult male outpatient diagnosed with symptomatic recurrent bacteriuria. The isolate was found to be resistant to ceftriaxone, cefotaxime, cefepime and levofloxacin. Genome analysis revealed the presence of the beta-lactamase chromosomal gene blaCMH-3, which may be responsible for the antibiotic resistance observed in the recurrent E. cloacae urinary tract infection.

Genomic and functional characterization of carbapenem-resistant Klebsiella pneumoniae from hospital wastewater

BACKGROUND

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) attracted extensive attention. Information on CRKP from hospital wastewater (HWW) is limited. The aims of this study were to investigate the genomic characteristics and to evaluate the survivability characteristics of 11 CRKP from HWW in a Chinese teaching hospital in Fujian province.

RESULTS

A total of 11 CRKP from HWW were recovered in this study. All CRKP from HWW were resistant to most antibiotics. Comparative genetic analysis demonstrated that all CRKP isolates were clustered into the three distinct phylogenetic clades and clade 2 and clade 3 were mixtures of samples collected from both HWW and clinical settings. Varieties of resistance genes, virulence genes and plasmid replicon types were detected in CRKP from HWW. In vitro transfer of bla_KPC-2 was successful for 3 bla_KPC-2-positive CRKP from HWW with high conjugation frequency. Our study demonstrated that the genetic environments of bla_KPC-2 shared core structure with ISKpn27-bla_KPC-2-ISKpn6. Group analysis showed that CRKP from HWW had a lower survivability in serum compared to clinical CRKP (p < 005); and CRKP from HWW had no significant difference in survivability in HWW compared to clinical CRKP (p > 005).

CONCLUSIONS

We analyzed the genomic and survivability characteristics of CRKP from HWW in a Chinese teaching hospital. These genomes represent a significant addition of genomic data from the genus and could serve as a valuable resource for future genomic studies about CRKP from HWW.

Genomic Analysis Revealed the International and Domestic Transmission of Carbapenem-Resistant Klebsiella pneumoniae in Chinese Pediatric Patients

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a severe threat to public health worldwide. Based on the genomic analysis of 198 CRKP isolates collected at Shanghai Children's Medical Center over the last 8 years (2013 to 2021), we reported the clinical risk, genetic diversity, and prevalence of antimicrobial resistance (AMR) of CRKP in pediatric patients at the genomic level. We found that the blaNDM genes were the predominant carbapenemase genes, followed by blaKPC-2 and blaIMP. All of the carbapenemases were disseminated mainly by four main types of plasmids, among which one plasmid was associated with a higher risk of bloodstream infections. Notably, we tracked disease outbreaks caused by recent introductions of ST14 CRKP from southeast Asia or western countries, and we reported frequent, repetitive introductions of ST11 from other domestic hospitals that were associated interhospital movement of the patients. The cocirculation of K. pneumoniae and AMR plasmids in hospitals highlights the importance of genome sequencing for monitoring and controlling CRKP infections. IMPORTANCE Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection in pediatric patients differs from that in adults patients in terms of both genetic and phenotypic features, which remain to be elucidated. We present a summary of prevalent CRKP isolates from Chinese pediatric patients over 8 years, demonstrating the prevalence and clinical importance of New Delhi metallo-β-lactamase genes in pediatric patients, mainly describing the genomic features of two predominant CRKP clones (ST11 and ST14) in Chinese children, and identifying four carbapenemase-encoding plasmids that contribute to the transmission of most carbapenemase genes in hospitals. Overall, our research provides valuable information about the international and domestic transmission of CRKP isolates that are prevalent in Chinese children and shows the urgent need for genome sequencing-based surveillance systems for monitoring the transmission of CRKP.

High-Molecular-Weight Plasmids Carrying Carbapenemase Genes blaNDM-1, blaKPC-2, and blaOXA-48 Coexisting in Clinical Klebsiella pneumoniae Strains of ST39

BACKGROUND

Klebsiella pneumoniae, a member of the ESKAPE group of bacterial pathogens, has developed multi-antimicrobial resistance (AMR), including resistance to carbapenems, which has increased alarmingly due to the acquisition of carbapenemase genes located on specific plasmids.

METHODS

Four clinical K. pneumoniae isolates were collected from four patients of a neuro-intensive care unit in Moscow, Russia, during the point prevalence survey. The AMR phenotype was estimated using the Vitec-2 instrument, and whole genome sequencing (WGS) was done using Illumina and Nanopore technologies.

RESULTS

All strains were resistant to beta-lactams, nitrofurans, fluoroquinolones, sulfonamides, aminoglycosides, and tetracyclines. WGS analysis revealed that all strains were closely related to K. pneumoniae ST39, capsular type K-23, with 99.99% chromosome identity. The novelty of the study is the description of the strains carrying simultaneously three large plasmids of the IncHI1B, IncC, and IncFIB groups carrying the carbapenemase genes of three types, bla_OXA-48, bla_NDM-1, and bla_KPC-2, respectively. The first of them, highly identical in all strains, was a hybrid plasmid that combined two regions of the resistance genes (bla_OXA-48 and bla_TEM-1 + bla_CTX-M-15 + bla_OXA-1 + catB + qnrS1 + int1) and a region of the virulence genes (iucABCD, iutA, terC, and rmpA2::IS110).

CONCLUSION

The spread of K. pneumoniae strains carrying multiple plasmids conferring resistance even to last-resort antibiotics is of great clinical concern.

Prediction of genome-wide imipenem resistance features in Klebsiella pneumoniae using machine learning

Introduction. The resistance rate of Klebsiella pneumoniae (K. pneumoniae) to imipenem is increasing year by year, and the imipenem resistance mechanism of K. pneumoniae is complex. Therefore, it is urgent to develop new strategies to explore the resistance mechanism of imipenem for its effective and accurate use in clinical practice.Hypothesis/Gap sStatement. Machine learning could identify resistance features and biological process that influence microbial resistance from whole-genome sequencing (WGS) data.Aims. This work aimed to predict imipenem resistance genetic features in K. pneumoniae from whole-genome k-mer features, and analyse their function for understanding its resistance mechanism.Methods. This study analysed WGS data of K. pneumoniae combined with resistance phenotype for imipenem, and established K. pneumoniae to imipenem genotype-phenotype model to predict resistance features using chi-squared test and random forest. An external clinical dataset was used to verify prediction power of resistance features. The potential genes were identified through alignment the resistance features with the K. pneumoniae reference genome using blastn, the functions of potential genes were further analysed to explore its resistance-related signalling pathways with GO and KEGG analysis, the resistance sequence patterns were screened using streme software. Finally, the resistance features were combined and modelled through four machine-learning algorithms (logistic regression, SVM, GBDT and XGBoost) to evaluate their phenotype prediction ability.Results. A total of 16 670 imipenem resistance features were predicted from genotype-phenotype model. The 30 potential genes were identified by annotating the resistance features and corresponded to known antibiotic-related genes (mdtM, dedA, rne, etc.). GO and KEGG pathway analyses indicated the possible association of imipenem resistance with metabolism process and cell membrane. CRYCAGCDN and CGRDAAAN were found from the imipenem resistance features, which were widely presented in the reported β-lactam resistance genes (bla _SHV, bla _CTX-M, bla _TEM, etc.), and YCYAGCMCAST with metabolic functions (organic substance metabolic process, nitrogen compound metabolic process and cellular metabolic process) was identified from the top 50 resistance features. The 25 resistance genes in the training dataset included 19 genes in the external dataset, which verified the accuracy of prediction. The area under curve values of logistics regression, SVM, GBDT and XGBoost were 0.965, 0.966, 0.969 and 0.969, respectively, indicating that the imipenem resistance features have a strong prediction power.Conclusion. Machine-learning methods could effectively predict the imipenem resistance feature in K. pneumoniae, and provide resistance sequence profiles for predicting resistance phenotype and exploring potential resistance mechanisms. It provides an important insight into the potential therapeutic strategies of K. pneumoniae resistance to imipenem, and speed up the application of machine learning in routine diagnosis.

Antimicrobial Resistance Patterns, Sequence Types, Virulence and Carbapenemase Genes of Carbapenem-Resistant Klebsiella pneumoniae Clinical Isolates from a Tertiary Care Teaching Hospital in Zunyi, China

Purpose

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has seriously threatened public health worldwide. This study aimed to investigate the antimicrobial resistance patterns, sequence types (STs), virulence and carbapenemase genes of CRKP isolates from patients in Zunyi, China.

Methods

CRKP isolates were collected from the First People's Hospital of Zunyi between January 2018 and December 2020. Antimicrobial susceptibility was determined using a VITEK^®2 analyzer and confirmed using either the broth dilution method, Kirby-Bauer method, or E-test assays. Carbapenemase production was examined using a modified carbapenem inactivation method. STs of the studied isolates were determined by multilocus sequence typing, and the presence of carbapenemase and virulence genes was examined using polymerase chain reaction assays.

Results

In total, 94 CRKP isolates were collected. All studied isolates produced carbapenemase, and the most common carbapenemase gene was New Delhi metallo-β-lactamase (NDM; 72.3%), followed by Klebsiella pneumoniae carbapenemase (KPC; 24.5%), and Verona integron-encoded metallo-β-lactamase (VIM; 3.2%). Of the studied isolates, 74.3% exhibited multidrug-resistant (MDR) phenotype, and 25.7% were either pandrug-resistant (PDR) or extensively drug-resistant (XDR) phenotypes. The most prevalent sequence type was ST2407 (37.2%), followed by ST76 (21.3%) and ST11 (11.7%). The NDM gene was present in 97.1% of ST2407 isolates and 90.0% of ST76 isolates, whereas the KPC gene was present in 90.9% of ST11 isolates. The majority of the isolates carried wabG, uge, and fimH virulence genes, with prevalence rates of 94.7%, 92.6%, and 94.7%, respectively.

Conclusion

This study describes NDM-producing ST2407 and ST76, as well as KPC-producing ST11, as the major clonal types of CRKP isolates in Zunyi, China. All CRKP isolates were resistant to multiple types of antibiotics, and the majority of isolates carried carbapenemase and virulence genes. Clonal spread of NDM-producing CRKP ST2407 and ST76, and KPC-producing CRKP ST11 should be strictly monitored.

Molecular and Clinical Characteristics of Carbapenem-Resistant Klebsiella pneumoniae Isolates at a Tertiary Hospital in Wuhan, China

Background

Carbapenem resistant Klebsiella pneumoniae (CRKP) is an independent risk factor for nosocomial infection which poses a serious threat to human health. How to prevent and suppress CRKP infection and explore its drug resistance mechanisms have become a huge challenge and possesses immediate significance.

Methods

A total of 45 CRKP strains isolated from hospitalized patients in Zhongnan Hospital of Wuhan University were collected from August 2018-December 2020. The strain's identification and antimicrobial susceptibility tests were performed using the VITEK 2 automated identification instrument. Single molecule DNA sequencing of 45 CRKP isolates was performed by the third generation high-throughput sequencing technology.

Results

The results were analyzed by multi locus sequence typing (MLST) and phylogenetic analysis. Antimicrobial susceptibility showed that 45 CRKP isolates were multi-drug resistant strains, and the resistance rates to common antibiotics were as high as 68%. Whole genome sequencing results showed that the CRKP strains carried multiple drug resistance genes and virulence factors. MLST analysis found two different sequence types (ST), of which 44 were ST11 and 1 was ST1049.

Conclusion

Through whole genome sequencing (WGS), we found multiple drug-resistant genes and virulence factors, and there was obvious dominant microbiota. The source was mainly related to nosocomial infection. The ST11-KPC Klebsiella pneumoniae was the main type, which was consistent with the most common type in China. We identified several dominant microbiotas which may serve as a target in the clinical prevention and treatment of severe bacterial infections. Our finding may have a role for guiding clinical antibiotic choosing.

Characteristics of Carbapenem-resistant Klebsiella pneumoniae in sewage from a tertiary hospital in Jilin Province, China

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is a serious problem in hospitals worldwide. We monitored a tertiary hospital in Changchun, Jilin Province, China, and found that CRKP was the major species among the carbapenem-resistant isolates in sewage. Subsequently, we evaluated the drug susceptibility, resistance genes, virulence genes, outer pore membrane protein-related genes (OmpK35 & OmpK 36), multi-locus sequence typing and replicons, biofilm formation capabilities, and resistance to chlorine-containing disinfectants among KP isolates. Identification of drug sensitivity, multiple resistance profiles were observed including 77 (82.80%) multidrug resistant (MDR), 16 (17.20%) extensive drug resistant (XDR). Some antibiotic resistance genes were detected, the most prevalent carbapenemase gene was blaKPC, and 16 resistance genes were associated with other antibiotics. In addition, 3 (3.23%) CRKP isolates demonstrated loss of OmpK-35 and 2 (2.15%) demonstrated loss of OmpK-36. In the detection of multi-locus sequence typing (MLST), 11 ST11 isolates carried virulence genes. The most common replicon type was IncFII. Biofilm-forming capabilities were demonstrated by 68.8% of the isolates, all of which were resistant to chlorine-containing disinfectants. The results of the study showed that antibiotic-resistant isolates, especially CRKP, could resist disinfectants in hospital wastewater, and improper treatment of hospital wastewater may lead to the spread of drug-resistant bacteria and their genes. Thus, these bacteria must be eliminated before being discharged into the municipal sewage system.

Genotyping and molecular investigation of plasmid-mediated carbapenem resistant clinical Klebsiella pneumoniae isolates in Egypt

Klebsiella pneumoniae is a multidrug-resistant nosocomial pathogen. Carbapenem resistance is mediated mainly by enzymes carried on transmissible plasmids causing their dissemination among other members of Enterobacteriaceae. This study aimed to molecularly detect carbapenem resistance genes in K. pneumoniae clinical isolates, genotype them using ERIC-PCR, and investigate plasmid transformation of resistant genes by using ERIC-PCR and sequencing.

Methods

Antimicrobial resistance of sixty carbapenem-resistant K. pneumoniae strains was evaluated by using the disc diffusion method. Five carbapenemases' genes were amplified by conventional PCR. Genotyping was performed using ERIC-PCR. Gene transformation was performed for the five genes to sensitive isolates. Wild and transformed isolates were genetically investigated using ERIC-PCR and sequencing.

Results

Carbapenem resistance in our isolates was associated with high resistance to all tested antibiotics. The 60 K. pneumoniae isolates were divided into 6 resistor types. The prevalence of KPC, IMP, VIM, NDM, and OXA-48 genes were 17%, 63%, 93%, 85% and 100%, respectively. Dendrogram analysis showed 57 distinct patterns, arranged in three clusters. The five genes were transformed successfully into sensitive isolates. ERIC profiles of wild and transformed isolates showed cluster A contained all the wild isolates, and cluster B contained all transformed isolates. Genetic sequences of the 5 genes reflected high genetic similarity with the GenBank reference genes before plasmid transformation; however, a distinguishable decrease of genetic similarity was observed after transformation.

Conclusion

Plasmid-mediated carbapenem resistance in K. pneumoniae and its dissemination among different strains is a real threat to public health.

Genetic and Phenotypic Characteristics of Carbapenem-Resistant Klebsiella pneumoniae Isolates from a Tertiary Hospital in Beijing

Objective

Klebsiella pneumoniae is a common multidrug-resistant pathogen that jeopardizes the health of hospitalized patients. We aimed to study the phenotypic and genotypic characteristics of carbapenem-resistant K. pneumoniae (CRKP) isolates from a hospital in Beijing.

Methods

Twenty-four CRKP clinical isolates were collected within a half-year to investigate antimicrobial resistance and genomic characteristics. Illumina and Nanopore sequencing were performed to assemble and annotate genomes.

Results

All strains were multi-drug resistant. Twenty-two strains carried the bla _KPC-2 gene and two harbored bla _NDM-5. Multilocus sequence type(MLST) analysis identified five sequence types; most isolates belonged to ST11. Three strains were isolated from the same patient; each carried a different plasmid replicon, either IncFII _(pHN7A8), IncX, or IncFIB _(K).

Conclusion

This study furthers the understanding of CRKP antimicrobial resistance genotypes, and may facilitate the control of nosocomial infections caused by antimicrobial-resistant pathogens.

Risk Factors and Molecular Mechanism of Polymyxin B Resistance in Carbapenem-Resistant Klebsiella pneumoniae Isolates from a Tertiary Hospital in Fujian, China

Background

The emergence of polymyxin B resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) causes clinical treatment to be more difficult. We aimed to investigate the risk factors and resistance mechanisms in the polymyxin resistant CRKP (PR-CRKP) strains.

Methods

From January 2021 to January 2022, 239 CRKP strains were selected, all of which were analyzed using antimicrobial susceptibility testing and clinical data. Polymerase chain reaction (PCR) was performed for the detection of resistance genes. RT-qPCR was used to quantify transcriptional levels of polymyxin resistance genes. Risk factors for polymyxin B resistant isolates were identified by logistic regression analysis.

Results

The resistance rate of polymyxin B was 5.02%. In all CRKP strains, 41.84% came from the ICU. The percentage of carbapenemase producing strains was 93.72%. The main carbapenem resistance gene was bla_KPC (90.79%). In the 12 strains of PR-CRKP screened, pmrB and pmrK were overexpressed in all samples which were linked with polymyxin B resistance. Multivariate analysis showed that coronary heart disease may be an independent risk factor predisposing patients to polymyxin B resistance.

Conclusion

We determine the multifaceted mechanism and risk factors of polymyxin B resistance in CRKP. Polymyxin resistance is a complex and changing problem, and more research is required.

Recent Advances in Nanotechnology for the Management of Klebsiella pneumoniae-Related Infections

Klebsiella pneumoniae is an important human pathogen that causes diseases such as urinary tract infections, pneumonia, bloodstream infections, bacteremia, and sepsis. The rise of multidrug-resistant strains has severely limited the available treatments for K. pneumoniae infections. On the other hand, K. pneumoniae activity (and related infections) urgently requires improved management strategies. A growing number of medical applications are using nanotechnology, which uses materials with atomic or molecular dimensions, to diagnose, eliminate, or reduce the activity of different infections. In this review, we start with the traditional treatment and detection method for K. pneumoniae and then concentrate on selected studies (2015-2022) that investigated the application of nanoparticles separately and in combination with other techniques against K. pneumoniae.

Epidemiology of carbapenem-resistant Klebsiella pneumoniae ST15 of producing KPC-2, SHV-106 and CTX-M-15 in Anhui, China

Background:

It is well known that carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a more problematic public health issue due to its widespread spread worldwide. In China, ST11-type CRKP is the most prevalent CRKP, but ST15-type CRKP, a recently prevalent high-risk clone, has emerged widely throughout China, posing a serious public health risk. Therefore, we conducted an epidemiological of an outbreak of ST15 CRKP of producing CTX-M-15, KPC-2 and SHV-106 in a tertiary hospital in Anhui, China, to Understanding the potential risks of the current STT15 CRKP outbreak.

Results:

From July 2021 to December 2021, 13 ST15 CRKP isolates were identified by collecting non-repeated clinical multidrug-resistant isolates, with all capsular typing of serotype KL19. All ST15 CRKP isolates were resistant to cephalosporins, carbapenems and quinolones, but were sensitive to amikacin, tigecycline and polymyxin B. In addition, isolates carried bla_SHV−106 (100%), bla_KPC−2 (69%), bla_CTX−M−15 (69%), bla_TEM−1B (69%), bla_OXA−1 (62%) and bla_LAP−2 (8%), as well as iron chelators (iutA, ybt, fyuA, ent, fepA, irp1, irp2, 100%) were detected. In phenotyping experiments, all ST15 CRKP exhibited lower growth rates than NTUH-K2044, and all ST15 CRKP did not exhibit mucoviscositty characteristics. However, in the Galleria mellonella infection model, isolates 21081212, 21081241 and 21091216 were more lethal than the hypervirulent isolates NTUH-K2044. Sequencing results showed that the genetic environment surrounding the genes bla_SHV−106, bla_KPC−2, bla_CTX−M−15, bla_OXA−1 and bla_TEM−1B were all identical in the ST15 CRKP isolates. Phylogenetic analysis showed that 13 ST15 CRKP isolates were divided into three subgroups, and when placed in global analysis, 10 of them were highly homologous to isolates from Jiangsu, two were highly homologous to isolates from Zhejiang, and one was homologous to an isolate from an unlabelled region.

Conclusion:

Our research shows that ST15 CRKP, which carries multiple β-lactamases genes and siderophores-encoding genes, may be evolving to hypervirulence and may have spread widely in localised areas. Therefore, environmental surveillance and clinical infection control in hospitals should be strengthened to prevent further spread of ST15 CRKP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02672-1.

Nanopore Electrochemistry for Pathogen Detection

Pathogen infections have seriously threatened human health, and there is an urgent demand for rapid and efficient pathogen identification to provide instructions in clinical diagnosis and therapeutic intervention. Recently, nanopore technology, a rapidly maturing technology which delivers ultrasensitive sensing and high throughput in real-time and at low cost, has achieved success in pathogen detection. Furthermore, the remarkable development of nanopore sequencing, for example, the MinION sequencer from Oxford Nanopore Technologies (ONT) as a competitive sequencing technology, has facilitated the rapid analysis of disease-related microbiomes at the whole-genome level and on a large scale. Here, we highlighted recent advances in nanopore approaches for pathogen detection at the single-molecule level. We also overviewed the applications of nanopore sequencing in pathogenic bacteria identification and diagnosis. In the end, we discussed the challenges and future developments of nanopore technology as promising tools for the management of infections, which may be helpful to aid understanding as well as decision-making.

Differential Overlap in Human and Animal Fecal Microbiomes and Resistomes in Rural versus Urban Bangladesh

While the development of antibiotic resistance in animal gut microbiomes and subsequent transmission to humans has been demonstrated in intensive farming environments and high-income countries, evidence of zoonotic exchange of antibiotic resistance in LMIC communities is lacking. This research provides genomic evidence of overlap of antibiotic resistance genes between humans and animals, especially in urban communities, and highlights chickens as important reservoirs of antibiotic resistance.

Coexistence of tmexCD-toprJ, blaNDM-1, and blaIMP-4 in One Plasmid Carried by Clinical Klebsiella spp

In clinical practice, carbapenems and tigecycline are considered significant options for treating infections caused by multidrug-resistant Klebsiella spp. The continual evolution of resistance mechanisms to carbapenems and tigecycline is shattering the present condition. Meanwhile, convergence of the two resistance mechanisms in a single strain has been reported repeatedly, posing a significant threat to public health and safety. In this study, two carbapenem- and tigecycline-resistant Klebsiella species were obtained from patients and investigated using antimicrobial susceptibility testing, conjugation assay, whole-genome sequencing, and bioinformatics analysis. In Klebsiella variicola FK2020ZBJ35, an untransferable multidrug IncFIB(Mar)/IncHI1B-like plasmid carrying tmexCD2-toprJ2, blaIMP-4, and blaNDM-1 was discovered, as was a similar plasmid carrying tmexCD1-toprJ1 and blaIMP-4 in Klebsiella quasipneumoniae 2019SCSN059. Genetic context analysis found that two distinct tmexCD-toprJ variants were detected in comparable mobile units with genetic array int-int-hp-hp-tnfxB-tmexCD-toprJ and integrated into separate genetic locations. blaIMP-4 and blaNDM-1 were carried by an integron In1377 and a truncated Tn3000, respectively. These findings revealed that the carbapenem and tigecycline resistance genes carried by the two strains were located on mobile elements and might potentially transmit horizontally to additional strains. Furthermore, our findings showed that IncFIB(Mar)/IncHI1B-like plasmids represent a significant reservoir of essential resistance genes that warrants continued monitoring. IMPORTANCE Tigecycline is an essential antibiotic that is used to treat infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP). The emergence of high-level tigecycline-resistant CRKP poses a serious hazard to human health. This work screened two tigecycline-resistant CRKP strains from clinical patients and found a type of plasmid that encoded carbapenemase and TmexCD-ToprJ in Klebsiella. Importantly, one plasmid cocarried tmexCD-toprJ, blaNDM-1, and blaIMP-4, hinting that this plasmid could be a critical vector for superbug development. Furthermore, we discovered that the carbapenem and tigecycline resistance genes are located in mobile units by genetic structure analysis. Our research tracks the formation of clinically super-resistant Gram-negative bacteria.

Complete Genome Sequence of Weissella cibaria NH9449 and Comprehensive Comparative-Genomic Analysis: Genomic Diversity and Versatility Trait Revealed

Lactic acid bacteria (LAB) in the genus Weissella spp. contain traits in their genome that confer versatility. In particular, Weissella cibaria encodes several beneficial genes that are useful in biotechnological applications. The complete genome of W. cibaria NH9449 was sequenced and an in silico comparative analysis was performed to gain insight into the genomic diversity among members of the genus Weissella. A total of 219 Weissella genomes were used in a bioinformatics analysis of pan-genomes, phylogenetics, self-defense mechanisms, virulence factors, antimicrobial resistance, and carbohydrate-active enzymes. These investigations showed that the strain NH9449 encodes several restriction-modification-related genes and a CRISPR-Cas region in its genome. The identification of carbohydrate-active enzyme-encoding genes indicated that this strain could be beneficial in biotechnological applications. The comparative genomic analysis reveals the very high genomic diversity in this genus, and some marked differences in genetic variation and genes among Weissella species. The calculated average amino acid identity (AAI) and phylogenetic analysis of core and accessory genes shows the possible existence of three new species in this genus. These new genomic insights into Weissella species and their biological functions could be useful in the food industry and other applications.

Epidemiology of Plasmids in Escherichia coli and Klebsiella pneumoniae with Acquired Extended Spectrum Beta-Lactamase Genes Isolated from Chronic Wounds in Ghana

Little information is available on the local epidemiology of mobile genetic elements such as plasmids harboring acquired beta-lactamase genes in Western African Ghana. In the present study, we screened for plasmids in three Escherichia coli and four Klebsiella pneumoniae isolates expressing extended spectrum beta-lactamases (ESBL) mediated by the bla_CTX-M-15 gene from chronically infected wounds of Ghanaian patients. Bacterial isolates were subjected to combined short-read and long-read sequencing to obtain the sequences of their respective plasmids. In the bla_CTX-M-15-gene-carrying plasmids of the four ESBL-positive K. pneumoniae isolates, IncFIB/IncFII (n = 3) and FIA (n = 1) sequences were detected, while in the bla_CTX-M-15-gene-carrying plasmids of the three ESBL-positive E. coli isolates, IncFIA/IncFIB (n = 2) and IncFIB (n = 1) sequences were found. The three IncFIB/IncFII sequence-containing plasmids were almost identical to a K. pneumoniae plasmid reported from France. They belonged to the clonal lineages ST17, ST36 and ST39 of K. pneumoniae, suggesting transversal spread of this obviously evolutionary successful plasmid in Ghana. Other resistance gene-encoding plasmids observed in the assessed Enterobacterales harbored IncFIA/IncR and IncFII sequences. International spread was confirmed by the high genetic similarity to resistance-mediating plasmids published from Asia, Australia, Europe and Northern America, including a bla_CTX-M-15-gene-carrying plasmid isolated from a wild bird in Germany. In conclusion, the study contributed to the scarcely available information on the epidemiology of third-generation cephalosporine resistance-mediating plasmids in Ghana. Furthermore, the global spread of resistance-mediating plasmids provided hints on the evolutionary success of individual resistance-harboring plasmids by transversal spread among K. pneumoniae lineages in Ghana.

Comparing Long-Read Assemblers to Explore the Potential of a Sustainable Low-Cost, Low-Infrastructure Approach to Sequence Antimicrobial Resistant Bacteria With Oxford Nanopore Sequencing

Long-read sequencing (LRS) can resolve repetitive regions, a limitation of short read (SR) data. Reduced cost and instrument size has led to a steady increase in LRS across diagnostics and research. Here, we re-basecalled FAST5 data sequenced between 2018 and 2021 and analyzed the data in relation to gDNA across a large dataset (n = 200) spanning a wide GC content (25-67%). We examined whether re-basecalled data would improve the hybrid assembly, and, for a smaller cohort, compared long read (LR) assemblies in the context of antimicrobial resistance (AMR) genes and mobile genetic elements. We included a cost analysis when comparing SR and LR instruments. We compared the R9 and R10 chemistries and reported not only a larger yield but increased read quality with R9 flow cells. There were often discrepancies with ARG presence/absence and/or variant detection in LR assemblies. Flye-based assemblies were generally efficient at detecting the presence of ARG on both the chromosome and plasmids. Raven performed more quickly but inconsistently recovered small plasmids, notably a ∼15-kb Col-like plasmid harboring bla KPC . Canu assemblies were the most fragmented, with genome sizes larger than expected. LR assemblies failed to consistently determine multiple copies of the same ARG as identified by the Unicycler reference. Even with improvements to ONT chemistry and basecalling, long-read assemblies can lead to misinterpretation of data. If LR data are currently being relied upon, it is necessary to perform multiple assemblies, although this is resource (computing) intensive and not yet readily available/useable.

Carbapenemase Production and Epidemiological Characteristics of Carbapenem-Resistant Klebsiella pneumoniae in Western Chongqing, China

Background

This study aimed to determine the molecular characteristics of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates in a hospital in western Chongqing, southwestern China.

Methods

A total of 127 unique CRKP isolates were collected from the Yongchuan Hospital of Chongqing Medical University, identified using a VITEK-2 compact system, and subjected to microbroth dilution to determine the minimal inhibitory concentration. Enterobacteriaceae intergenic repeat consensus polymerase chain reaction and multilocus sequence typing were used to analyze the homology among the isolates. Genetic information, including resistance and virulence genes, was assessed using polymerase chain reaction. The genomic features of the CRKP carrying gene bla_KPC-2 were detected using whole-genome sequencing.

Results

ST11 was the dominant sequence type in the homology comparison. The resistance rate to ceftazidime-avibactam in children was much higher than that in adults as was the detection rate of the resistance gene bla_NDM (p < 0.0001). Virulence genes such as mrkD (97.6%), uge (96.9%), kpn (96.9%), and fim-H (84.3%) had high detection rates. IncF (57.5%) was the major replicon plasmid detected, and sequencing showed that the CRKP063 genome contained two plasmids. The plasmid carrying bla_KPC-2, which mediates carbapenem resistance, was located on the 359,625 base pair plasmid IncFII, together with virulence factors, plasmid replication protein (rep B), stabilizing protein (par A), and type IV secretion system (T4SS) proteins that mediate plasmid conjugation transfer.

Conclusion

Our study aids in understanding the prevalence of CRKP in this hospital and the significant differences between children and adults, thus providing new ideas for clinical empirical use of antibiotics.

Microbial Characteristics and Genomic Analysis of an ST11 Carbapenem-Resistant Klebsiella pneumoniae Strain Carrying blaKPC−2 Conjugative Drug-Resistant Plasmid

Background

The sequence type 11 (ST11) carbapenem-resistant Klebsiella pneumoniae (CRKP) carrying blaKPC−2 has been widespread all over the world, and it has been reported frequently in China. The blaKPC−2 located on the mobile genetic element brings tremendous pressure to control the spread and outbreak of resistant bacteria. Whole-genome sequencing (WGS) technology can comprehensively and in-depth display the molecular characteristics of drug-resistant bacteria, providing a basis for evaluating the genetic diversity within the CRKP genome.

Methods

The ST11 CRKP in this study was collected in the intensive care unit of a major teaching hospital. PCR and Sanger sequencing confirmed the existence of blaKPC−2. The AST-GN card and the microbroth dilution test were used for antimicrobial susceptibility testing. The transferability of plasmid was verified by a conjugation test. The whole genome is sequenced using the Illumina HiSeq short-read and Oxford Nanopore long-read sequencing technology.

Results

The studied strain was named CRKP63, which is a multi-drug resistance bacteria, which carries blaKPC−2 and blaSHV−182. Its genome consists of a circular chromosome of 5,374,207 bp and an IncFII plasmid named pKPC-063001 of 359,625 bp. In the drug-resistant plasmid pKPC-063001, the key carbapenem resistance gene blaKPC−2 was located in the genetic context with insertion sequence ISKpn27 upstream and ISKpn6 downstream and bracketed by IS26. The three copies of the IS26–ISKpn27–blaKPC−2–ISKpn6–IS26 unit were present in tandem. blaKPC−2 can be transferred horizontally between other species by conjugation, the complete type IV secretion system (T4SS) structure helps to improve the adaptability of bacteria to the external environment, strengthen the existence of drug-resistant bacteria, and accelerate the spread of drug resistance.

Conclusion

High-throughput sequencing has discovered the different surrounding environments of blaKPC−2, which provides a new idea for further revealing the transmission and inheritance of blaKPC−2 at the molecular level. In order to control the further spread and prevalence of drug-resistant bacteria, we should pay close attention to the changes in the genetic environment of blaKPC−2 and further study the transcription and expression of T4SS.

Co-occurrence of genes encoding carbapenemase, ESBL, pAmpC, and Non-β-Lactam resistance among Klebsiella pneumonia and E. coli clinical isolates in Tunisia

This study aimed to investigate the molecular mechanisms of carbapenem and colistin resistance in K. pneumoniae and E. coli isolates obtained from hospitalized patients in Carthagene International Hospital of Tunis. A total of 25 K. pneumoniae and 2 E. coli clinical isolates with reduced susceptibility to carbapenems were recovered. Susceptibility testing and phenotypic screening tests were carried out. ESBL, AmpC, carbapenemase, and other antibiotic resistance genes were sought by PCR-sequencing. The presence of plasmid-mediated colistin resistance genes (mcr-1-8) was examined by PCR and the nucleotide sequence of the mgrB gene was determined. The analysis of plasmid content was performed by PCR-Based Replicon Typing (PBRT). The clonality of isolates was assessed by PFGE and multilocus sequence typing (MLST). All of the isolates produced carbapenemase activity. They showed a great variation in the distribution of ESBL, AmpC, carbapenemase, and other plasmid-mediated resistance determinants. K. pneumoniae isolates carried bla_NDM-1 (n=11), bla_OXA-48 (n=11), bla_NDM-1 + bla_OXA-48 (n=1), bla_NDM-1 + bla_VIM-1 (n=1), bla_OXA-204 (n=1), along with bla_CTX-M , bla_OXA , bla_TEM , bla_CMY , bla_DHA and bla_SHV genes variants on conjugative plasmid of IncL/M, IncR, IncFII_K , IncFIB, and IncHI1 types. Three sequence types ST101, ST307, and ST15 were identified. The mgrB alteration g109a (G37S) was detected in a single colistin-resistant, NDM-1 and OXA-48-coproducing K. pneumoniae isolate. The two E. coli isolates belonged to ST95, co-produced NDM-1 and CTX-M-15, and harbored plasmid of IncFII and IncFIB types. To our knowledge, this is the first report in Tunisia of NDM-1, OXA-48, and CTX-M-15 coexistence in colistin-resistant K. pneumoniae ST15.

Efficacy of Ceftazidime-Avibactam Versus Polymyxin B and Risk Factors Affecting Clinical Outcomes in Patients With Carbapenem-Resistant Klebsiella pneumoniae Infections a Retrospective Study

Background: The worldwide outbreak of carbapenem-resistant Klebsiella pneumoniae (CRKP) has become an urgent public health problem. High mortality and lack of effective treatments further pose new challenges to control this infection. However, studies about the evaluation of available antibiotics for CRKP infection are limited. The present study aimed to compare the efficacy of polymyxin B versus ceftazidime-avibactam (CAZ/AVI) in Chinese patients with CRKP infections and to identify risk factors affecting 7-day bacterial eradication and 28-day all-cause mortality. Methods: From January 8, 2018, to July 6, 2020, a total of 115 adult CRKP infected patients from two tertiary teaching hospitals in Shanghai, China were enrolled based on the inclusion and exclusion criteria. By reviewing electronic medical records of these patients, demographic and clinical data were extracted. The selected patients were divided into polymyxin B and CAZ/AVI groups according to primary antibiotic exposure to compare therapeutic effects. Binary logistic and cox's regression analysis were performed to identify risk factors for 7-day bacterial eradication and all-cause mortality. Results: One hundred and five patients were treated with polymyxin B (67.8%) or CAZ/AVI (32.2%). Patients in the CAZ/AVI group had significantly lower rates of 28-day mortality (8.1 vs 29.5%, p = 0.013), higher microbiological eradication and 28-day clinical success. Multivariate analysis showed that Charlson comorbidity index (≥3) and prior antibiotic use within 90 days were independent risk factors for poor microbiological eradication. Cox's regression analysis indicated that the length of hospitalization after CRKP infection and baseline creatinine clearance negatively affected 28-day mortality. Conclusion: CAZ/AVI was more effective than polymyxin B and appeared to be a promising drug for CRKP infection, especially for critically ill patients.

Rapid detection of KPC-producing Klebsiella pneumoniae in China based on MALDI-TOF MS

Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) represent a serious threat to public health and their timely detection is essential for patient management and the prevention of nosocomial infections. Here, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to rapidly identify dominant KPC-Kp in China, by using an automated detection of a KPC-specific peak (at 4521 m/z) by a genetic algorithm using ClinProTools software. Whole-genome sequencing (WGS) was used to understand the genetic environment of the bla_KPC-2 gene. In this study, we analyzed 235 K. pneumoniae Chinese clinical isolates, of which 175 (93 KPC-positive isolates and 82 KPC-negative isolates) isolates were used to build a model to select a KPC-specific peak, and another 60 isolates for external validation. In addition, all the spectra were visually inspected by the FlexAnalysis software to evaluate the accuracy of the automated detection. The results showed a 4521 m/z peak found in all bla_KPC-2-positive isolates but absent in bla_KPC-2-negative isolates. Interestingly, all KPC-Kp belonged to ST11, the dominant clone in China. WGS analysis of a representative isolate showed that the genetic environment of KPC-2 was IS26-ISKpn27-bla_KPC-2-ΔISKpn6-Tn1721, similar to the KPC-2 genetic environment of ST11 KPC-Kp previously reported in China. Therefore, the 4521 m/z peak is closely related to ST11 KPC-Kp. In summary, we used MALDI-TOF MS to quickly detect KPC-Kp in the process of routine bacterial identification without increasing costs or requiring further knowledge, which has broad application prospects in drug resistance analysis and infection control.

Pathogenic Characteristics and Risk Factors for ESKAPE Pathogens Infection in Burn Patients

Objective

This study aimed to determine the clinical manifestations, antimicrobial resistance, molecular characteristics, and risk factors for ESKAPE pathogens infection in burn patients.

Methods

A retrospective study of 187 burn patients infected with ESKAPE pathogens was conducted at the Department of Plastic and Burn Surgery of the Affiliated Hospital of Southwest Medical University (Luzhou, China) from October 2018 to June 2021. All strains were identified using a MicroScan WalkAway 96 Plus System, and antimicrobial susceptibilities were determined using the VITEK system or the disk diffusion method. The antimicrobial resistance genes of multi-drug resistant ESKAPE (MDR-ESKAPE) were detected by polymerase chain reaction (PCR). The multivariable logistic regression analysis was used to estimate the risk factors for ESKAPE infection and MDR-ESKAPE infection.

Results

A total of 255 strains were isolated in various types of clinical specimens from 187 burn patients, of which 47.5% were ESKAPE pathogens (121/255). Among these, MDR-ESKAPE pathogens accounted for 55% (67/121). Additionally, aph3ʹIII, mecA, bla_SHV, bla_TEM, bla_PDC, and bla_SHV were the most prevalent genes detected in Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp., respectively. The independent risk factors for ESKAPE infection were total body surface area (TBSA) >30–50% (odds ratio [OR] = 10.428; 95% confidence interval [CI], 2.047 to 53.108), TBSA >50% (OR = 15.534; 95% CI, 1.489 to 162.021), and parenteral nutrition (OR = 3.597; 95% CI, 1.098 to 11.787). No independent risk factors were found for MDR-ESKAPE infection.

Conclusion

Clinical staff should be alert to the risk of nosocomial infection with ESKAPE pathogens in burn patients receiving parenteral nutrition and under TBSA >30%. Full attention should also be paid to the ESKAPE resistance, strict adherence to infection control protocols for the rational use of antimicrobial agents, and enhanced clinical standardization of antimicrobial agents management.

Molecular Analysis and Antimicrobial Resistance Pattern of Tigecycline-Non-Susceptible K. pneumoniae Isolated from a Tertiary Care Hospital of East Asia

Introduction

Tigecycline is one of the last resorts for carbapenem-resistant K. pneumoniae (CRKP) infections. Indeed, tigecycline-non-susceptible K. pneumoniae (TNSKP) strains are increasingly treated with the use of tigecycline. In this study, we attempted to better understand their epidemiological trends and characteristics. K. pneumoniae were collected from 2017 to 2020 at the First Affiliated Hospital of Nanchang University.

Methods

Thirty-four TNSKP strains were selected during the study period, all of which were analyzed using antimicrobial susceptibility testing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). PCR and DNA sequencing were performed for the detection of β-lactamase genes and carbapenemase genes, and the mutation analysis of tet(A), tet(X), tet(L), tet(M), rpsJ, ramR, and oqxR, which are related to tigecycline resistance. Virulence gene and capsular genotype testing were conducted to identify whether the TNSKP strains were hypervirulent Klebsiella pneumoniae.

Results

An epidemiology analysis showed that Klebsiella pneumoniae carbapenemase-2 (KPC-2) was the predominant carbapenemase in tigecycline non-susceptible carbapenem-resistant K. pneumoniae (TNSCRKP) (96.7%), and the dominant clone type was ST11-K14K64 (82.4%). Among them, 55.9% (19/34) of strains were from each department of ICU, particularly EICU and neurosurgery ICU. In order to further understand the molecular mechanisms of the TNSKP, a polymerase chain reaction of the resistant determinants was carried out. The results detected many tigecycline-resistant genes, such as tet(A) (97.1%), tet(X) (17.6%), rpsJ (97.1%), and ramR (8.8%).

Conclusion

As the results of this study reveal, we should take effective measures to control the increase in TNSKP.

Molecular Epidemiological Analysis of ST11-K64 Extensively Drug-Resistant Klebsiella pneumoniae Infections Outbreak in Intensive Care and Neurosurgery Units Based on Whole-Genome Sequencing

Klebsiella pneumoniae (Kp) is the primary causative bacteria for nosocomial infections and hospital outbreaks. In particular, extensively drug-resistant K. pneumoniae (XDRKp) causes severe clinical infections in hospitalized patients. Here, we used pulsed-field gel electrophoresis (PFGE), drug susceptibility tests, and the whole-genome sequencing (WGS) technology to examine genetic relatedness and phenotypic traits of the strains isolated during an outbreak period. Based on PFGE, a distinct clones cluster comprised of eight XDRKp was observed. These strains were confirmed as ST11-K64 via multiple-locus sequence typing database of Kp. The strains also had genes related to the regulation of biofilm biosynthesis (type 1 & 3 fimbriae, type IV pili biosynthesis, RcsAB, and type VI secretion system) and multiple drug resistance (β-lactamase and aminoglycoside antibiotic resistance). WGS data based on core-single nucleotide polymorphisms and epidemiological investigation showed that the neurosurgery unit was likely the source of the outbreak, the strain was likely to have been transmitted to the ICU through patients. In addition, the two highly probable transmission routes were in the ICU (exposure through shared hospital beds) and the neurosurgery units (all cases were treated by the same rehabilitation physician and were most likely infected during the physical therapy). Notably, the bed mattress had played a crucial transmission role of this outbreak, served as a pathogen reservoir.

Shift in the Dominant Sequence Type of Carbapenem-Resistant Klebsiella pneumoniae Bloodstream Infection from ST11 to ST15 at a Medical Center in Northeast China, 2015-2020

Objective

To investigate the clinical characteristics and molecular epidemiology of carbapenem-resistant Klebsiella pneumoniae (CRKP) bloodstream infection at a medical center in northeast China, especially after coronavirus disease (COVID-19) pandemic.

Methods

Fifty-one patients were diagnosed with CRKP bloodstream infection between January 2015 and December 2020, among which 42 isolates were available for further study. Species identification and antibiotic susceptibilities were tested with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and VITEK 2 systems. Carbapenemase genes, virulence genes and MLST genes were detected by polymerase chain reaction. Moreover, the string test and serum killing assay were performed to evaluate the virulence of the CRKP isolates.

Results

During the six-year period, the detection rate of CRKP in bloodstream infection showed an increasing trend, with the intensive care unit, hematology and respiratory medicine wards mainly affected. Molecular epidemiology analyses showed that KPC-2 was the dominant carbapenemase gene. In addition, the dominant sequence type (ST) of CRKP shifted from ST11 to ST15 strains, which were all sensitive to amikacin in contrast to the ST11 stains. Furthermore, ST15 CRKP strains were positive for the KfuB virulence gene and more resistant to serum killing compared to the ST11 CRKP strains. Nonetheless, the mortality rate of patients infected with ST11 and ST15 CRKP did not show any significant differences.

Conclusion

A shift in the dominant sequence type of CRKP bloodstream infections from ST11 to ST15 was observed during the years 2015–2020. Compared to ST11, the ST15 CRKP strains showed amikacin sensitivity, positivity for KfuB gene, and serum resistance, which may indicate stronger virulence.

Genetic factors related to the widespread dissemination of ST11 extensively drug-resistant carbapenemase-producing Klebsiella pneumoniae strains within hospital

Background

Carbapenemase-producing Klebsiella pneumoniae (CP-Kp) poses distinct clinical challenges due to extensively drug resistant (XDR) phenotype, and sequence type (ST) 11 is the most dominant bla_KPC-2-bearing CP-Kp clone in China. The purpose of this current retrospective study was to explore the genetic factors associated with the success of XDR CP-Kp ST11 strains circulated in the intensive care unit (ICU) of a Chinese tertiary hospital.

Methods

Six ST11 XDR CP-Kp strains were identified between May and December 2014 and validated by minimum inhibitory concentration examination, polymerase chain reaction, and pyrosequencing. The six ST11 XDR CP-Kp, as well as three multi-drug resistant (MDR) and four susceptible strains, were sequenced using single-molecule real-time method. Comprehensively structural and functional analysis based on comparative genomics was performed to identify genomic characteristics of the XDR ST11 CP-Kp strains.

Results

We found that ST11 XDR bla_KPC-2-bearing CP-Kp strains isolated from inpatients spread in the ICU of the hospital. Functionally, genes associated with information storage and processing of the ST11 XDR CP-Kp strains were more abundant than those of MDR and susceptible strains, especially genes correlative with mobile genetic elements (MGEs) such as transposons and prophages. Structurally, eleven large-scale genetic regions taken for the unique genome in these ST11 XDR CP-Kp strains were identified as MGEs including transposons, integrons, prophages, genomic islands, and integrative and conjugative elements. Three of them were located on plasmids and eight on chromosomes; five of them were with antimicrobial resistance genes and eight with adaptation associated genes. Notably, a new bla_KPC-2-bearing ΔΔTn1721-bla_KPC-2 transposon, probably transposed and truncated from ΔTn1721-bla_KPC-2 by IS903D and ISKpn8, was identified in all six ST11 XDR CP-Kp strains.

Conclusion

Our findings suggested that together with clonal spread, MGEs identified uniquely in the ST11 XDR CP-Kp strains might contribute to their formidable adaptability, which facilitated their widespread dissemination in hospital.

Detection of a New Resistance-Mediating Plasmid Chimera in a blaOXA-48-Positive Klebsiella pneumoniae Strain at a German University Hospital

Mobile genetic elements, such as plasmids, facilitate the spread of antibiotic resistance genes in Enterobacterales. In line with this, we investigated the plasmid-resistome of seven bla_OXA-48 gene-carrying Klebsiella pneumoniae isolates, which were isolated between 2013 and 2014 at the University Medical Center in Göttingen, Germany. All isolates were subjected to complete genome sequencing including the reconstruction of entire plasmid sequences. In addition, phenotypic resistance testing was conducted. The seven isolates comprised both disease-associated isolates and colonizers isolated from five patients. They fell into two clusters of three sequence type (ST)101 and two ST11 isolates, respectively; and ST15 and ST23 singletons. The seven isolates harbored various plasmids of the incompatibility (Inc) groups IncF, IncL/M, IncN, IncR, and a novel plasmid chimera. All bla_OXA-48 genes were encoded on the IncL/M plasmids. Of note, distinct phenotypical resistance patterns associated with different sets of resistance genes encoded by IncL/M and IncR plasmids were observed among isolates of the ST101 cluster in spite of high phylogenetic relatedness of the bacterial chromosomes, suggesting nosocomial transmission. This highlights the importance of plasmid uptake and plasmid recombination events for the fast generation of resistance variability after clonal transmission. In conclusion, this study contributes a piece in the puzzle of molecular epidemiology of resistance gene-carrying plasmids in K. pneumoniae in Germany.

Genetic Basis of Antimicrobial Resistant Gram-Negative Bacteria Isolated From Bloodstream in Brazil

Multidrug-resistant microorganisms are a well-known global problem, and gram-negative bacilli are top-ranking. When these pathogens are associated with bloodstream infections (BSI), outcomes become even worse. Here we applied whole-genome sequencing to access information about clonal distribution, resistance mechanism diversity and other molecular aspects of gram-negative bacilli (GNB) isolated from bloodstream infections in Brazil. It was possible to highlight international high-risk clones circulating in the Brazilian territory, such as CC258 for Klebsiella pneumoniae, ST79 for Acinetobacter baumannii and ST233 for Pseudomonas aeruginosa. Important associations can be made such as a negative correlation between CRISPR-Cas and K. pneumoniae CC258, while the genes bla_TEM, bla_KPC and bla_CTX−M are highly associated with this clone. Specific relationships between A. baumannii clones and bla_OXA−51 variants were also observed. All P. aeruginosa ST233 isolates showed the genes bla_VIM and bla_OXA486. In addition, some trends could be identified, where a new P. aeruginosa MDR clone (ST3079), a novel A. baumannii clonal profile circulating in Brazil (ST848), and important resistance associations in the form of bla_VIM−2 and bla_IMP−56 being found together in one ST233 strain, stand out. Such findings may help to develop approaches to deal with BSI and even other nosocomial infections caused by these important GNB.

Correlation between antimicrobial resistance and biofilm formation capability among Klebsiella pneumoniae strains isolated from hospitalized patients in Iran

BACKGROUND

Klebsiella pneumoniae is a common cause of nosocomial infections. Antibiotic resistance and ability to form biofilm, as two key virulence factors of K. pneumoniae, are involved in the persistence of infections. The purpose of this study was to investigate the correlation between antimicrobial resistance and biofilm formation capability among K. pneumoniae strains isolated from hospitalized patients in Iran.

METHODS

Over a 10-month period, a total of 100 non-duplicate K. pneumoniae strains were collected. Antibiotic susceptibility was determined by Kirby-Bauer disk diffusion method according to CLSI. Biofilm production was assessed by tissue culture plate method. Finally, polymerase chain reaction was conducted to detect four families of carbapenemase: blaIMP, blaVIM, blaNDM, blaOXA-48; biofilm formation associated genes: treC, wza, luxS; and K. pneumoniae confirming gene: rpoB.

RESULTS

Most of the isolates were resistant to trimethoprim-sulfamethoxazole (52 %), cefotaxime (51 %), cefepime (43 %), and ceftriaxone (43 %). Among all the 100 isolates, 67 were multidrug-resistant (MDR), and 11 were extensively drug-resistant (XDR). The prevalence of the blaVIM, blaIMP, blaNDM, and blaOXA-48 genes were 7 , 11 , 5 , and 28 %, respectively. The results of biofilm formation in the tissue culture plate assay indicated that 75 (75 %) strains could produce biofilm and only 25 (25 %) isolates were not able to form biofilm. Among these isolates, 25 % formed fully established biofilms, 19 % were categorized as moderately biofilm-producing, 31 % formed weak biofilms, and 25 % were non-biofilm-producers. The antimicrobial resistance among biofilm former strains was found to be significantly higher than that of non-biofilm former strains (p < 0.05). Molecular distribution of biofilm formation genes revealed that 98 , 96 , and 34 % of the isolates carried luxS, treC, and wza genes, respectively.

CONCLUSIONS

The rise of antibiotic resistance among biofilm-producer strains demonstrates a serious concern about limited treatment options in the hospital settings. All of the data suggest that fundamental actions and introduction of novel strategies for controlling of K. pneumoniae biofilm-related infections is essential.

Komodo-dragon cathelicidin-inspired peptides are antibacterial against carbapenem-resistant Klebsiella pneumoniae

Introduction.The rise of carbapenem-resistant enterobacteriaceae (CRE) is a growing crisis that requires development of novel therapeutics.

Hypothesis.To this end, cationic antimicrobial peptides (CAMPs) represent a possible source of new potential therapeutics to treat difficult pathogens such as carbapenem-resistantKlebsiella pneumoniae(CRKP), which has gained resistance to many if not all currently approved antibiotics, making treatment difficult.

Aim.To examine the anti-CRKP antimicrobial activity of the predicted cathelicidins derived fromVaranus komodoensis(Komodo dragon) as well as synthetic antimicrobial peptides that we created.

Methodology.We determined the minimum inhibitory concentrations of the peptides against CRKP. We also characterized the abilities of these peptides to disrupt the hyperpolarization of the bacterial membrane as well as their ability to form pores in the membrane.

Results.We did not observe significant anti-CRKP activity for the predicted native Komodo cathelicidin peptides. We found that the novel peptides DRGN-6,-7 and -8 displayed significant antimicrobial activity against CRKP with MICs of 4–8 µg ml−1. DRGN-6 peptide was the most effective peptide against CRKP. Unfortunately, these peptides showed higher than desired levels of hemolysis, althoughin vivotesting in the waxwormGalleria mellonellashowed no mortality associated with treatment by the peptide; however, CRKP-infected waxworms treated with peptide did not show an improvement in survival.

Conclusion.Given the challenges of treating CRKP, identification of peptides with activity against it represents a promising avenue for further research. Given DRGN-6′s similar level of activity to colistin, DRGN-6 is a promising template for the development of novel antimicrobial peptide-based therapeutics.

NDM-1 Carbapenemase-Producing Enterobacteriaceae are Highly Susceptible to Ceragenins CSA-13, CSA-44, and CSA-131

Background and Purpose

Treatment of infections caused by NDM-1 carbapenemase-producing Enterobacteriaceae (CPE) represents one of the major challenges of modern medicine. In order to address this issue, we tested ceragenins (CSAs – cationic steroid antimicrobials) as promising agents to eradicate various NDM-1-producing Gram-negative enteric rods.

Materials and Methods

Susceptibility to CSA-13, CSA-44, and CSA-131 of four reference NDM-1 carbapenemase-producing strains, ie, Escherichia coli BAA-2471, Enterobacter cloacae BAA-2468, Klebsiella pneumoniae subsp. pneumoniae BAA-2472, and K. pneumoniae BAA-2473 was assessed by MIC/MBC testing of planktonic cells as well as biofilm formation/disruption assays. To define the mechanism of CSAs bactericidal activity, their ability to induce generation of reactive oxygen species (ROS), permeabilization of the inner and outer membranes, and their mechanical and adhesive properties upon CSA addition were examined. Additionally, hemolytic assays were performed to assess CSAs hemocompatibility.

Results

All tested CSAs exert substantial bactericidal activity against NDM-1-producing bacteria. Moreover, CSAs significantly prevent biofilm formation as well as reduce the mass of developed biofilms. The mechanism of CSA action comprises both increased permeability of the outer and inner membrane, which is associated with an extensive ROS generation. Additionally, atomic force microscopy (AFM) analysis has shown morphological alterations in bacterial cells and the reduction of stiffness and adhesion properties. Importantly, CSAs are characterized by low hemolytic activity at concentrations that are bactericidal.

Conclusion

Development of ceragenins should be viewed as one of the valid strategies to provide new treatment options against infections associated with CPE. The studies presented herein demonstrate that NDM-1-positive bacteria are more susceptible to ceragenins than to conventional antibiotics. In effect, CSA-13, CSA-44, and CSA-131 may be favorable for prevention and decrease of global burden of CPE.

Virulence evolution, molecular mechanisms of resistance and prevalence of ST11 carbapenem-resistant Klebsiella pneumoniae in China: A review over the last 10 years

Sequence type 11 (ST11) carbapenem-resistant Klebsiella pneumoniae (CRKP) has become the dominant clone in China. In this review, we trace the prevalence of ST11 CRKP in the China Antimicrobial Surveillance Network (CHINET), the key antimicrobial resistance mechanisms and virulence evolution. The recent emergence of ST11 carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) strains in China due to the acquisition of a pLVPK-like virulence plasmid, which may cause severe infections in relatively healthy individuals that are difficult to treat with current antibiotics, has attracted worldwide attention. There is a very close linkage among IncF plasmids, NTE_KPC and ST11 K. pneumoniae in China. Hybrid conjugative virulence plasmids are demonstrated to readily convert a ST11 CRKP strain to a CR-hvKP strain via conjugation. Understanding the molecular evolutionary mechanisms of resistance and virulence-bearing plasmids as well as the prevalence of ST11 CRKP in China allows improved tracking and control of such organisms.

High Prevalence of 16S rRNA Methyltransferase Genes in Carbapenem-Resistant Klebsiella pneumoniae Clinical Isolates Associated with Bloodstream Infections in 11 Chinese Teaching Hospitals

Objective

The 16S rRNA methylase-mediated high-level resistance to aminoglycosides has become a great concern. The purpose of the study was to investigate the occurrence of 16S rRNA methyltransferase (RMTase) genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) clinical isolates associated with bloodstream infections (BSIs) in China.

Methods

From July 2015 to December 2018, a total of 137 unique CRKP clinical isolates associated with BSIs were collected from 11 Chinese teaching hospitals. PCR and DNA sequencing were used to identify 16S RMTase genes. Whole-genome sequencing (WGS) was performed on all CRKP clinical isolates. Relevant information was extracted from WGS data (antibiotic resistance determinants, K-type and wzi allelic types). All 16S RMTase-producing CRKP clinical isolates were characterized by antimicrobial susceptibility testing, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE).

Results

In this study, 137 CRKPs were found to harbor at least one carbapenemase gene. Among 137 CRKPs, 78 (56.9%, 78/137) were positive for 16S RMTase genes (5 for armA, 70 for rmtB, 3 for both armA and rmtB) and highly resistant to gentamicin and amikacin (MICs ≥256 mg/L). Seventy-five isolates harboring 16S RMTase genes also produced ESBLs. In this study, 5 sequence types (STs) and 6 capsule serotypes were found among 78 isolates positive for 16S RMTases genes, while 14 STs and 6 capsule serotypes were found among 59 isolates negative for 16S RMTases genes. Compared with the isolates negative for 16S RMTases genes, the STs and capsular serotypes of 16S RMTases-positive strains are more concentrated. Among 78 16S RMTases-positive strains, the most prevalent clone type is ST11-PFGE-B-KL64-wzi64 (62.8%, 49/78), which mainly carries the rmtB and bla_KPC genes and is distributed in 7 provinces in China.

Conclusion

A high prevalence of 16S RMTase genes was found among CRKP clinical isolates associated with BSIs from Chinese teaching hospitals, which was attributed to the dissemination of the ST11-PFGE-B-KL64-wzi64 clone.