Unique genes identified in the epidemic extremely drug-resistant KPC-producing Klebsiella pneumoniae sequence type 258

Global prevalence and transmission of the mcr-9 in Salmonella: A genomic study with insights from Salmonella enterica serovar Thompson isolated from poultry food in China

The plasmid-mediated mcr-9 gene has been widely detected in Salmonella across multiple countries and regions, raising significant concerns for food safety and public health. To investigate the transmission dynamics of mcr-9 in Salmonella, we conducted a comprehensive genomic epidemiological study and explored the potential mechanisms of mcr-9 transmission in poultry-derived S. Thompson in China. This study analyzed 126 mcr-9-positive Salmonella isolates from food in China and genomic data of 1,487 publicly available mcr-9-positive Salmonella collected over the past 40 years from 32 countries and various sources. Two variants, mcr-9.1 and mcr-9.2, were detected, with mcr-9.1 being the most prevalent subtype globally. S. Typhimurium/I 4,[5],12:i:- (23.1 %, 372/1,613) was the dominant lineage of the total collection, followed by S. Saintpaul (15.9 %, 256/1,613), S. Heidelberg (11.4 %, 184/1,613), and S. Thompson (8.6 %, 139/1,613). S. Typhimurium/I 4,[5],12:i:- was widely distributed in North America and Europe, primarily prevalent in humans and swine, whereas S. Thompson was predominantly found in China, mainly prevalent in poultry-related foods and humans. Conjugation experiments were performed on 116 S. Thompson strains from 126 Salmonella isolates. The results showed that 85.3 % (99/116) of the mcr-9-positive plasmids were transferable. The IncHI2-IncHI2A plasmids from three representative donors demonstrated the ability to transfer at varying frequencies to seven Salmonella recipients of different serotypes including Typhimurium, Thompson, Enteritidis, Indiana, Rissen, London, and Derby. Chicken juice matrix significantly increased the proportion of mcr-9-positive S. Thompson conjugants. The inability of mcr-9-positive IncHI2-IncHI2A plasmids to transfer via conjugation may be due to the integration of the plasmid into the chromosome. In addition, the deletion of IS1B-cfdB-fucO-frmR-uvrA-fghA-gloA-frmA-uvrB-flhD-smc-copG-IS26 gene region was observed in the non-conjugative mcr-9-positive plasmids. These findings underscore the importance of ongoing surveillance of mcr-9-positive multidrug-resistant S. Thompson for food safety in China.

Molecular characteristics and antimicrobial resistance profiles of Carbapenem-Resistant Klebsiella pneumoniae isolates at a tertiary hospital in Nanning, China

PURPOSE

Carbapenem resistant Klebsiella pneumoniae is associated with nosocomial infections and can cause high mortality, which poses great threat to human health. This study was aimed at investigating the molecular epidemiology and antimicrobial resistance profiles of carbapenem resistant Klebsiella pneumoniae isolates and providing clues for management and control of carbapenem resistant Klebsiella pneumoniae infections.

METHODS

A total of 2324 Klebsiella pneumoniae strains were isolated from the First Affiliated Hospital of Guangxi Medical University from June 2018 to October 2020, and 103 carbapenem resistant Klebsiella pneumoniae strains from inpatients were collected, and the specimens mainly came from the sputum, urine, secretions, and blood. The antimicrobial susceptibility tests were performed using the VITEK 2 Compact system or the Kirby-Bauer disk-diffusion method. The resistance genes were detected by polymerase chain reaction and sequencing. The homology analysis of carbapenem resistant Klebsiella pneumoniae strains was performed by multilocus sequence typing.

RESULTS

Antimicrobial susceptibility results showed that the 103 carbapenem resistant Klebsiella pneumoniae strains were resistant to most common antibiotics. Resistance genes detection showed that the carbapenem resistant Klebsiella pneumoniae isolates mainly carried metallo-beta-lactamase, and the predominant gene was NDM-1. The homology analysis found that the major ST type were ST11, follow by ST15 and ST17.

CONCLUSION

The carbapenem resistant Klebsiella pneumoniae isolates in our study shown resistance to most common antibiotics. Of the 103 carbapenem resistant Klebsiella pneumoniae strains, 91 strains (88.35%) carried carbapenemases genes, and NDM was the predominant carbapenemase gene detected. ST11 was the major ST typing of carbapenem resistant Klebsiella pneumoniae in our hospital. Our finding may play a role in control and management of the carbapenem resistant Klebsiella pneumoniae infections and guiding clinical antibiotic therapy. In addition, metallo-beta-lactamase should be served as a key target to be monitored in carbapenem resistant Klebsiella pneumoniae infection.

Molecular epidemiology, risk factors, and outcomes of carbapenem-resistant Klebsiella pneumoniae infection in a tertiary hospital in eastern China: for a retrospective study conducted over 4 years

Objectives

Carbapenem-resistant Klebsiella pneumoniae (CRKP) have been extensively disseminated worldwide, resulting in increased mortality. We performed a retrospective analysis of the epidemiology and risk factors for the outcome of CRKP infection in a general teaching hospital in China.

Methods

A molecular and clinical study was conducted for 98 CRKP in a tertiary hospital from January 2013 to December 2016. Carbapenemase gene detection, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. Logistic regression was also used to identify the risk factors associated with 30-day mortality.

Results

The production of KPC carbapenemase was the main resistant mechanism, and KPC carbapenemase increased annually with a significant difference. However, the molecular outcome revealed the dominance and diversity in CRKP with 24 sequence types (STs) and 59 PFGE types (PTs). The ST11 CRKP strains, which showed a significant increasing trend year by year, were documented as predominant in our study. Additionally, the predominant ST11 CRKP corresponding to PT10 and PT15 continued to exhibit their characteristic patterns. Importantly, the newly identified PT09 and PT16 strains, corresponding to the ST11 lineage, were only discovered in 2016. Meanwhile, factors affecting 30-day mortality and ST11 proportionality with CRKP infection were assessed, and ST11, appropriate empirical treatment, and hospital stays were found to be independently associated with 30-day mortality.

Conclusion

The ST11 CRKP strains played a dominant role in the process; however, the homology of these strains was polymorphic, and the advantage clusters were subject to changes through evolution. Furthermore, in addition to appropriate empirical treatment and hospital stays, ST11 CRKP was independently associated with 30-day mortality. To the best of our knowledge, this association was reported for the first time.

Multidrug-resistant Klebsiella pneumoniae: a retrospective study in Manaus, Brazil

Klebsiella pneumoniae is an opportunistic pathogen that can cause several infections, mainly in hospitalised or immunocompromised individuals. The spread of K. pneumoniae emerging virulent and multidrug-resistant clones is a worldwide concern and its identification is crucial to control these strains especially in hospitals. This article reports data related to multi-resistant K. pneumoniae strains, isolated from inpatients in the city of Manaus, Brazil, harbouring virulence and antimicrobial-resistance genes, including high-risk international clones belonging to clonal group (CG) 258. Twenty-one strains isolated from different patients admitted to four hospitals in the city of Manaus, located in the state of Amazonas, Northern Brazil (Amazon Rainforest region) were evaluated. The majority of strains (61.9% n = 13) were classified as multidrug-resistant (MDR), and five strains (23.8%) as extensively drug-resistant (XDR). Several virulence and antimicrobial-resistance genes were found among the strains and eight strains (38.1%) presented the hyper-mucoviscous phenotype. MLST analysis demonstrated a great diversity of STs among the strains, totaling 12 different STs (ST11, ST23, ST198, ST277, ST307, ST340, ST378, ST462, ST502, ST3991, ST3993 and ST5209). Three of these (ST11, ST23 and ST340) belong to CG258.

Characteristics in the whole-genome sequence of Klebsiella pneumoniae ST147 from Turkey

The study aimed to analyze antibiotic resistance determinants in a carbapenem-resistant Klebsiella pneumoniae by whole-genome sequencing (WGS). K. pneumoniae was isolated from a urine sample and it was characterized by 16S rDNA sequencing in Turkey. This strain was named as Kpn Rize-53-TR. Antimicrobial susceptibility testing was performed for seventeen antibiotics by VITEK-2 and the result was confirmed by MIC. The whole genome of isolate was sequenced by Illumina and was analysed by bioinformatic tools for MLST, replicon types, and antimicrobial resistance genes. The whole genome data was submitted to NCBI. The isolate was found to be resistant to all tested β-lactam antibiotics and the highest MIC values were found for piperacillin, piperacillin/tazobactam (≥128). No resistance to colistin and moderate susceptibility to amikacin and tetracycline was observed. The isolate carried 12 resistance genes belonging to 10 resistance classes; ere(A), fosA, oqxB, cmlA1, aac(a)-IIa, bla KPC-2, bla TEM-1A, bla SHV-67, bla CTX-M-15, bla OXA-1-2-9. Mutations were detected in gyrA (83Y) and parC (80I) genes. Clonal subtype of the isolate was ST147, and it had wzi420 and wzc38 alleles. Its serotype was O3/O3a. The bla KPC-2 was firstly found in both ST147 clonal group in Turkey and in serotype O3/O3a in the world. By plasmid replicon typing, five plasmids IncFII(K), Col(BS512), IncR, IncFIA(HI1) and IncFIB(pQil) were determined in Kpn Rize-53-TR and bla KPC-2 was located on IncFII(K) plasmid. The presence of bla KPC-2 on the plasmid with other resistance genes accelerates its own spread together with other resistance genes.

Emergence of New Non-Clonal Group 258 High-Risk Clones among Klebsiella pneumoniae Carbapenemase-Producing K. pneumoniae Isolates, France

The worldwide spread of Klebsiella pneumoniae carbapenemase–producing Klebsiella pneumoniae (KPC-Kp) isolates was reported to be caused by dissemination of 1 clonal complex (i.e., clonal group [CG] 258, which includes sequence types [STs] 258 and 512). We conducted whole-genome sequencing and epidemiologic analysis of all KPC-Kp isolates in France in 2018 and found that new successful high-risk clones of ST147, ST307, ST231, and ST383 are now the main drivers of bla_KPC genes. The bla_KPC genes were mostly carried by Tn4401a and Tn4401d structures and a new non–Tn4401 element. Our epidemiologic investigations showed that the emergence of these non-CG258 KPC-Kp isolates in France was linked to dissemination of these clones from Portugal. Thus, KPC-Kp epidemiology has changed in Europe, at least in several non–KPC-endemic countries of western Europe, such as France and Portugal, where CG258 is not the most prevalent clone.

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.

IMP-38-Producing High-Risk Sequence Type 307 Klebsiella pneumoniae Strains from a Neonatal Unit in China

An emerging multidrug-resistant Klebsiella pneumoniae high-risk clone of sequence type 307 (ST307) has been increasingly reported worldwide. Here, we described the genomic characteristics of an IMP-38-producing ST307 K. pneumoniae strain and investigated the prevalence of blaIMP-38 among carbapenem-resistant Klebsiella pneumoniae isolates from a tertiary care hospital in central China. A total of 14 IMP-38-producing ST307 K. pneumoniae strains were identified from 2013 to 2016, with 13 strains isolated from patients with neonatal sepsis in the neonatal ward. PacBio and Illumina whole-genome sequencing analysis performed on a representative IMP-38-producing K. pneumoniae strain, WCGKP294, showed that it contained a circular chromosome and two plasmids. Carbapenemase gene blaIMP-38 is colocated with blaCTX-M-3 in transposon Tn6382 on an IncHI5 plasmid (pWCGKP294-2). WCGKP294 harbors another IncFIB plasmid, pWCGKP294-1, carrying three copies of tandem-repeated IS26-blaSHV-2A-deoR-ygbJ-ygbK-fucA-IS26 composite transposon elements. Phylogenetic analysis placed WCGKP294 in the global ST307 cluster, distant from the U.S. (Texas) and South Africa clusters. Nevertheless, WCGKP294 does not contain the chromosomal fluoroquinolone resistance-associated mutations and IncFIIK/IncFIBK plasmid-associated blaCTX-M-15 gene that are frequently found in other global ST307 strains.IMPORTANCE We described the genome and resistome characterization of a carbapenem-resistant Klebsiella pneumoniae ST307 strain carrying blaIMP-38 in China. This report highlights that the high-risk ST307 clone continues to acquire different antimicrobial resistance genes, posing significant challenges to clinical practice, and should be closely monitored.

Fatty Acid Methyl Ester (FAME) Profiling Identifies Carbapenemase-Producing Klebsiella pneumoniae Belonging to Clonal Complex 258

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the most extensively antibiotic-resistant pathogens encountered in the clinical setting today. A few studies to-date suggest that CRKP and carbapenem-susceptible K. pneumoniae (CSKP) differ from one another not only with respect to their underlying genetics, but also their transcriptomic and metabolomic fingerprints. Within this context, we characterize the fatty acid methyl ester (FAME) profiles of these pathogens in vitro. Specifically, we evaluated the FAME profiles of six Klebsiella pneumoniae carbapenemase (KPC)-producing isolates belonging to the CC258 lineage (KPC+/258+), six KPC-producing isolates belonging to non-CC258 lineages (KPC+/258−), and six non-KPC-producing isolates belonging to non-CC258 lineages (KPC−/258−). We utilized a single-step sample preparation method to simultaneously lyse bacterial cells and transesterify the lipid fraction, and identified 14 unique FAMEs using gas chromatography-mass spectrometry. The machine learning algorithm Random Forest identified four FAMEs that were highly discriminatory between CC258 and non-CC258 isolates (9(Z)-octadecenoate, 2-phenylacetate, pentadecanoate, and hexadecanoate), of which three were also significantly different in relative abundance between these two groups. These findings suggest that distinct differences exist between CC258 and non-CC258 K. pneumoniae isolates with respect to the metabolism of both fatty acids and amino acids, a hypothesis that is supported by previously-acquired transcriptomic data.

The Acinetobacter baumannii Mla system and glycerophospholipid transport to the outer membrane

The outer membrane (OM) of Gram-negative bacteria serves as a selective permeability barrier that allows entry of essential nutrients while excluding toxic compounds, including antibiotics. The OM is asymmetric and contains an outer leaflet of lipopolysaccharides (LPS) or lipooligosaccharides (LOS) and an inner leaflet of glycerophospholipids (GPL). We screened Acinetobacter baumannii transposon mutants and identified a number of mutants with OM defects, including an ABC transporter system homologous to the Mla system in E. coli. We further show that this opportunistic, antibiotic-resistant pathogen uses this multicomponent protein complex and ATP hydrolysis at the inner membrane to promote GPL export to the OM. The broad conservation of the Mla system in Gram-negative bacteria suggests the system may play a conserved role in OM biogenesis. The importance of the Mla system to Acinetobacter baumannii OM integrity and antibiotic sensitivity suggests that its components may serve as new antimicrobial therapeutic targets.

Klebsiella pneumoniae: a major worldwide source and shuttle for antibiotic resistance

Klebsiella pneumoniae is an important multidrug-resistant (MDR) pathogen affecting humans and a major source for hospital infections associated with high morbidity and mortality due to limited treatment options. We summarize the wide resistome of this pathogen, which encompasses plentiful chromosomal and plasmid-encoded antibiotic resistance genes (ARGs). Under antibiotic selective pressure, K. pneumoniae continuously accumulates ARGs, by de novo mutations, and via acquisition of plasmids and transferable genetic elements, leading to extremely drug resistant (XDR) strains harboring a 'super resistome'. In the last two decades, numerous high-risk (HiR) MDR and XDR K. pneumoniae sequence types have emerged showing superior ability to cause multicontinent outbreaks, and continuous global dissemination. The data highlight the complex evolution of MDR and XDR K. pneumoniae, involving transfer and spread of ARGs, and epidemic plasmids in highly disseminating successful clones. With the worldwide catastrophe of antibiotic resistance and the urgent need to identify the main pathogens that pose a threat on the future of infectious diseases, further studies are warranted to determine the epidemic traits and plasmid acquisition in K. pneumoniae. There is a need for future genomic and translational studies to decipher specific targets in HiR clones to design targeted prevention and treatment.

Molecular characterization of clinical IMP-producing Klebsiella pneumoniae isolates from a Chinese Tertiary Hospital

BACKGROUND

IMP-producing Klebsiella pneumoniae (IMPKpn) exhibits sporadic prevalence in China. The mechanisms related to the spread of IMPKpn remain unclear.

METHODS

Carbapenem non-susceptible K. pneumoniae isolates were collected from our hospital. The genetic relatedness, antimicrobial susceptibility, as well as sequence types (ST) were analyzed by pulsed-field gel electrophoresis (PFGE), VITEK 2 AST test Kit, and multilocus sequence typing (MLST), respectively. S1-PFGE, Southern blot analysis and multiple PCR amplification were used for plasmid profiling.

RESULTS

Between October 2009 and June 2016, 25 non-repetitive IMPKpn isolates were identified. PFGE results showed that these isolates belonged to 20 genetically unrelated IMPKpn strains. Diverse STs were identified by MLST. Most strains carried bla IMP-4, followed by bla IMP-1. Four incompatibility types of bla IMP-carrying plasmids were identified, which included A/C (n = 2), B/O (n = 2), L/M (n = 1) and N (n = 14), while type of other one plasmid failed to be determined.

CONCLUSIONS

The IMPKpn isolates exhibited sporadic prevalence in our hospital. IncN types of plasmids with various sizes have emerged as the main platform mediating the spread of the bla IMP genes in our hospital.

A cluster of KPC-2 and VIM-2-producing Klebsiella pneumoniae ST833 isolates from the pediatric service of a Venezuelan Hospital

BACKGROUND

Klebsiella pneumoniae is a bacterial pathogen that has developed resistance to multiple antibiotics and is a major cause of nosocomial infections worldwide. Carbapenemase-producing Klebsiella pneumoniae have been isolated in many hospitals in Venezuela, but they have not been well-studied. The aim of this study was to characterize carbapenem-resistant Klebsiella pneumoniae isolates from the pediatric service of a hospital located in Anzoategui State, in the eastern part of Venezuela.

METHODS

Nineteen Klebsiella pneumoniae strains isolated in the hospital from April to July 2014 were evaluated phenotypically and molecularly for the presence of carbapenemases blaKPC, blaIMP and blaVIM. Molecular epidemiology was performed with Repetitive Extragenic Palindromic-PCR (REP-PCR) and Multilocus Sequence Typing (MLST). They were also studied for phenotypic and molecular resistance to a quaternary ammonium compound (QAC) disinfectant.

RESULTS

All 19 isolates contained both bla _VIM-2 and bla _KPC-2 genes, and the bla _KPC-2 gene was associated with Tn4401b. All isolates were phenotypically sensitive to QACs and contained qacΔE and addA2 genes typical of class 1 integrons. Analysis by REP-PCR and MLST showed that all isolates had identical profiles characteristic of sequence type ST833.

CONCLUSION

All 19 strains are bla _VIM-2 and bla _KPC-_2-producing ST833 K. pneumoniae sensitive to QACs. This analysis may help to understand the routes of dissemination and confirms that QAC disinfectants can be used to help control their spread.

NDM-producing Enterobacteriaceae in a Chinese hospital, 2014-2015: identification of NDM-producing Citrobacterwerkmanii and acquisition of blaNDM-1-carrying plasmid in vivo in a clinical Escherichia coli isolate

New Delhi metallo-β-lactamase (NDM)-producing Enterobacteriaceae (NPE) shows prevalence in China. Little is known about the mechanisms related to the spread of NPE. Recently, a total of 51 non-duplicated NPE isolates were collected from a tertiary-care hospital in China and analysed for genetic relatedness by PFGE, antimicrobial susceptibility by Etest and sequence type by multilocus sequence typing. S1-PFGE and Southern blot analysis or PCR amplification were used for plasmid profiling. Between 2014 and 2015, 22 Escherichia coli, 10 Klebsiella pneumoniae, 9 Enterobacter cloacae, 2 Enterobacter aerogenes, 3 Providencia rettgeri, 1 Klebsiella oxytoca, 1 Proteus mirabilis, 1 Citrobacter freundii, 1 Citrobacterwerkmanii and 1 Raoultella planticola were identified as NPE. Results of PFGE and multilocus sequence typing showed that most strains were genetically unrelated. Among the 45 blaNDM-carrying plasmids, there were 25 IncX3 plasmids with a size of about 30 to 50 kb, one 100 kb IncX3 plasmid, 11 IncA/C plasmids with a size range from 70 to 300 kb, six 90 to 120 kb IncB/O plasmids, one IncN plasmid with a size of 100 kb and one 140 kb IncFrep plasmid. An NDM-1-producing isolate of C. werkmanii was identified, which had not been reported previously. An Escherichia coli strain was found acquiring a blaNDM-1-carrying IncFrep plasmid in vivo during infection. In conclusion, an NDM-1-producing isolate of C. werkmanii was identified. An Escherichia coli strain acquired a blaNDM-1-carrying plasmid in vivo. IncX3 and IncA/C plasmids with various sizes might have emerged as the main platforms mediating the spread of the blaNDM genes in China.

Horizontal Transfer of Carbapenemase-Encoding Plasmids and Comparison with Hospital Epidemiology Data

Carbapenemase-producing organisms have spread worldwide, and infections with these bacteria cause significant morbidity. Horizontal transfer of plasmids carrying genes that encode carbapenemases plays an important role in the spread of multidrug-resistant Gram-negative bacteria. Here we investigate parameters regulating conjugation using an Escherichia coli laboratory strain that lacks plasmids or restriction enzyme modification systems as a recipient and also using patient isolates as donors and recipients. Because conjugation is tightly regulated, we performed a systematic analysis of the transfer of Klebsiella pneumoniae carbapenemase (blaKPC)-encoding plasmids into multiple strains under different environmental conditions to investigate critical variables. We used four blaKPC-carrying plasmids isolated from patient strains obtained from two hospitals: pKpQIL and pKPC-47e from the National Institutes of Health, and pKPC_UVA01 and pKPC_UVA02 from the University of Virginia. Plasmid transfer frequency differed substantially between different donor and recipient pairs, and the frequency was influenced by plasmid content, temperature, and substrate, in addition to donor and recipient strain. pKPC-47e was attenuated in conjugation efficiency across all conditions tested. Despite its presence in multiple clinical species, pKPC_UVA01 had lower conjugation efficiencies than pKpQIL into recipient strains. The conjugation frequency of these plasmids into K. pneumoniae and E. coli patient isolates ranged widely without a clear correlation with clinical epidemiological data. Our results highlight the importance of each variable examined in these controlled experiments. The in vitro models did not reliably predict plasmid mobilization observed in a patient population, indicating that further studies are needed to understand the most important variables affecting horizontal transfer in vivo.

Klebsiella pneumoniae: Going on the Offense with a Strong Defense

Klebsiella pneumoniae causes a wide range of infections, including pneumonias, urinary tract infections, bacteremias, and liver abscesses. Historically, K. pneumoniae has caused serious infection primarily in immunocompromised individuals, but the recent emergence and spread of hypervirulent strains have broadened the number of people susceptible to infections to include those who are healthy and immunosufficient. Furthermore, K. pneumoniae strains have become increasingly resistant to antibiotics, rendering infection by these strains very challenging to treat. The emergence of hypervirulent and antibiotic-resistant strains has driven a number of recent studies. Work has described the worldwide spread of one drug-resistant strain and a host defense axis, interleukin-17 (IL-17), that is important for controlling infection. Four factors, capsule, lipopolysaccharide, fimbriae, and siderophores, have been well studied and are important for virulence in at least one infection model. Several other factors have been less well characterized but are also important in at least one infection model. However, there is a significant amount of heterogeneity in K. pneumoniae strains, and not every factor plays the same critical role in all virulent Klebsiella strains. Recent studies have identified additional K. pneumoniae virulence factors and led to more insights about factors important for the growth of this pathogen at a variety of tissue sites. Many of these genes encode proteins that function in metabolism and the regulation of transcription. However, much work is left to be done in characterizing these newly discovered factors, understanding how infections differ between healthy and immunocompromised patients, and identifying attractive bacterial or host targets for treating these infections.

Complete Genome Sequence of Klebsiella pneumoniae Carbapenemase-Producing K. pneumoniae Myophage Miro

Klebsiella pneumoniae is a Gram-negative pathogen frequently associated with antibiotic-resistant nosocomial infections. Bacteriophage therapy against K. pneumoniae may be possible to combat these infections. The following describes the complete genome sequence and key features of the pseudo-T-even K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae myophage Miro.

The role of epidemic resistance plasmids and international high-risk clones in the spread of multidrug-resistant Enterobacteriaceae

Escherichia coli sequence type 131 (ST131) and Klebsiella pneumoniae ST258 emerged in the 2000s as important human pathogens, have spread extensively throughout the world, and are responsible for the rapid increase in antimicrobial resistance among E. coli and K. pneumoniae strains, respectively. E. coli ST131 causes extraintestinal infections and is often fluoroquinolone resistant and associated with extended-spectrum β-lactamase production, especially CTX-M-15. K. pneumoniae ST258 causes urinary and respiratory tract infections and is associated with carbapenemases, most often KPC-2 and KPC-3. The most prevalent lineage within ST131 is named fimH30 because it contains the H30 variant of the type 1 fimbrial adhesin gene, and recent molecular studies have demonstrated that this lineage emerged in the early 2000s and was then followed by the rapid expansion of its sublineages H30-R and H30-Rx. K. pneumoniae ST258 comprises 2 distinct lineages, namely clade I and clade II. Moreover, it seems that ST258 is a hybrid clone that was created by a large recombination event between ST11 and ST442. Epidemic plasmids with blaCTX-M and blaKPC belonging to incompatibility group F have contributed significantly to the success of these clones. E. coli ST131 and K. pneumoniae ST258 are the quintessential examples of international multidrug-resistant high-risk clones.

Genomic Analysis of the Emergence and Rapid Global Dissemination of the Clonal Group 258 Klebsiella pneumoniae Pandemic

Multidrug-resistant Klebsiella pneumoniae producing the KPC carbapenemase have rapidly spread throughout the world, causing severe healthcare-associated infections with limited antimicrobial treatment options. Dissemination of KPC-producing K. pneumoniae is largely attributed to expansion of a single dominant strain, ST258. In this study, we explore phylogenetic relationships and evolution within ST258 and its clonal group, CG258, using whole genome sequence analysis of 167 isolates from 20 countries collected over 17 years. Our results show a common ST258 ancestor emerged from its diverse parental clonal group around 1995 and likely acquired blaKPC prior to dissemination. Over the past two decades, ST258 has remained highly clonal despite diversity in accessory elements and divergence in the capsule polysaccharide synthesis locus. Apart from the large recombination event that gave rise to ST258, few mutations set it apart from its clonal group. However, one mutation occurs in a global transcription regulator. Characterization of outer membrane protein sequences revealed a profile in ST258 that includes a truncated OmpK35 and modified OmpK37. Our work illuminates potential genomic contributors to the pathogenic success of ST258, helps us better understand the global dissemination of this strain, and identifies genetic markers unique to ST258.

Carbapenemase-Producing Klebsiella pneumoniae, a Key Pathogen Set for Global Nosocomial Dominance

The management of infections due to Klebsiella pneumoniae has been complicated by the emergence of antimicrobial resistance, especially to carbapenems. Resistance to carbapenems in K. pneumoniae involves multiple mechanisms, including the production of carbapenemases (e.g., KPC, NDM, VIM, OXA-48-like), as well as alterations in outer membrane permeability mediated by the loss of porins and the upregulation of efflux systems. The latter two mechanisms are often combined with high levels of other types of β-lactamases (e.g., AmpC). K. pneumoniae sequence type 258 (ST258) emerged during the early to mid-2000s as an important human pathogen and has spread extensively throughout the world. ST258 comprises two distinct lineages, namely, clades I and II, and it seems that ST258 is a hybrid clone that was created by a large recombination event between ST11 and ST442. Incompatibility group F plasmids with blaKPC have contributed significantly to the success of ST258. The optimal treatment of infections due to carbapenemase-producing K. pneumoniae remains unknown. Some newer agents show promise for treating infections due to KPC producers; however, effective options for the treatment of NDM producers remain elusive.

Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae at a single institution: insights into endemicity from whole-genome sequencing

The global emergence of Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) multilocus sequence type ST258 is widely recognized. Less is known about the molecular and epidemiological details of non-ST258 K. pneumoniae in the setting of an outbreak mediated by an endemic plasmid. We describe the interplay of bla_KPC plasmids and K. pneumoniae strains and their relationship to the location of acquisition in a U.S. health care institution. Whole-genome sequencing (WGS) analysis was applied to KPC-Kp clinical isolates collected from a single institution over 5 years following the introduction of bla_KPC in August 2007, as well as two plasmid transformants. KPC-Kp from 37 patients yielded 16 distinct sequence types (STs). Two novel conjugative bla_KPC plasmids (pKPC_UVA01 and pKPC_UVA02), carried by the hospital index case, accounted for the presence of bla_KPC in 21/37 (57%) subsequent cases. Thirteen (35%) isolates represented an emergent lineage, ST941, which contained pKPC_UVA01 in 5/13 (38%) and pKPC_UVA02 in 6/13 (46%) cases. Seven (19%) isolates were the epidemic KPC-Kp strain, ST258, mostly imported from elsewhere and not carrying pKPC_UVA01 or pKPC_UVA02. Using WGS-based analysis of clinical isolates and plasmid transformants, we demonstrate the unexpected dispersal of bla_KPC to many non-ST258 lineages in a hospital through spread of at least two novel bla_KPC plasmids. In contrast, ST258 KPC-Kp was imported into the institution on numerous occasions, with other bla_KPC plasmid vectors and without sustained transmission. Instead, a newly recognized KPC-Kp strain, ST941, became associated with both novel bla_KPC plasmids and spread locally, making it a future candidate for clinical persistence and dissemination.

Emergence of blaKPC carbapenemase genes in Australia

blaKPC genes encoding resistance to carbapenems are increasingly widely reported and are now endemic in parts of several countries, but only one Klebsiella pneumoniae isolate carrying blaKPC-2 had previously been reported in Australia, in 2010. Here we characterised this isolate, six additional K. pneumoniae and one Escherichia coli carrying blaKPC and another K. pneumoniae lacking blaKPC, all isolated in Australia in 2012. Seven K. pneumoniae belonged to clonal complex (CC) 292, associated with blaKPC in several countries. Five with blaKPC-2 plus the isolate lacking a blaKPC gene were sequence type 258 (ST258) and the seventh was the closely related ST512 with blaKPC-3. The eighth K. pneumoniae isolate, novel ST1048, and the E. coli (ST131) also carried blaKPC-2. blaKPC genes were associated with the most common Tn4401a variant, which gives the highest levels of expression, in all isolates. The ST258 isolates appeared to share a similar set of plasmids, with IncFIIK, IncX3 and ColE-type plasmids identified in most isolates. All K. pneumoniae isolates had a characteristic insertion in the ompK35 gene resulting in a frameshift and early termination, but only the ST512 isolate had a GlyAsp insertion in loop 3 of OmpK36 that may contribute to increased resistance. The clinical epidemiology of blaKPC emergence in Australia thus appears to reflect the global dominance of K. pneumoniae CC292 (and perhaps E. coli ST131). Some, but not all, patients carrying these isolates had previously been hospitalised outside Australia, suggesting multiple discrete importation events of closely related strains, as well as undetected nosocomial spread.

Carbapenem-resistant Enterobacteriaceae: biology, epidemiology, and management

Introduced in the 1980s, carbapenem antibiotics have served as the last line of defense against multidrug-resistant Gram-negative organisms. Over the last decade, carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant public health threat. This review summarizes the molecular genetics, natural history, and epidemiology of CRE and discusses approaches to prevention and treatment.

Carbapenemase-producing Klebsiella pneumoniae: molecular and genetic decoding

Klebsiella pneumoniae carbapenemases (KPCs) were first identified in 1996 in the USA. Since then, regional outbreaks of KPC-producing K. pneumoniae (KPC-Kp) have occurred in the USA, and have spread internationally. Dissemination of blaKPC involves both horizontal transfer of blaKPC genes and plasmids, and clonal spread. Of epidemiological significance, the international spread of KPC-producing K. pneumoniae is primarily associated with a single multilocus sequence type (ST), ST258, and its related variants. However, the molecular factors contributing to the success of ST258 largely remain unclear. In this review, we discuss the recent progresses in understanding KPC-producing K. pneumoniae that are contributing to our knowledge of plasmid and genome composition and structure among the KPC epidemic clone, and we identify possible factors that influence its epidemiological success.

Genomics of KPC-producing Klebsiella pneumoniae sequence type 512 clone highlights the role of RamR and ribosomal S10 protein mutations in conferring tigecycline resistance

Full genome sequences were determined for five Klebsiella pneumoniae strains belonging to the sequence type 512 (ST512) clone, producing KPC-3. Three strains were resistant to tigecycline, one showed an intermediate phenotype, and one was susceptible. Comparative analysis performed using the genome of the susceptible strain as a reference sequence identified genetic differences possibly associated with resistance to tigecycline. Results demonstrated that mutations in the ramR gene occurred in two of the three sequenced strains. Mutations in RamR were previously demonstrated to cause overexpression of the AcrAB-TolC efflux system and were implicated in tigecycline resistance in K. pneumoniae. The third strain showed a mutation located at the vertex of a very well conserved loop in the S10 ribosomal protein, which is located in close proximity to the tigecycline target site in the 30S ribosomal subunit. This mutation was previously shown to be associated with tetracycline resistance in Neisseria gonorrhoeae. A PCR-based approach was devised to amplify the potential resistance mechanisms identified by genomics and applied to two additional ST512 strains showing resistance to tigecycline, allowing us to identify mutations in the ramR gene.

Characterization of multidrug-resistant Klebsiella pneumoniae from Australia carrying blaNDM-1

blaNDM genes, encoding metallo-β-lactamases providing resistance to carbapenems, have been reported in many locations since the initial report in 2008, including in several Enterobacteriaceae isolates in Australia/New Zealand. Here, we compare 4 additional carbapenem-resistant Klebsiella pneumoniae carrying blaNDM-1 isolated in Australia. Two are sequence type ST147, previously associated with blaNDM in Australia and elsewhere. They carry blaNDM-1 and different 16S rRNA methylase genes (armA or rmtC) on different conjugative plasmids, in 1 case with an IncFIIY replicon. One isolate belongs to the globally important ST11 but did not transfer a plasmid to Escherichia coli. The fourth isolate belongs to the novel ST1068 and transferred blaNDM-1, armA, and an IncA/C plasmid. Amplification and sequencing of ompK porin genes suggest that, unlike the case for other carbapenemase genes, ompK36 defects may not be required for NDM to cause clinically relevant levels of carbapenem resistance.

Development and validation of a multiplex PCR assay for identification of the epidemic ST-258/512 KPC-producing Klebsiella pneumoniae clone

The Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-KP) sequence type (ST)-258/512 clone is the dominant clone by which KPC has disseminated worldwide. Standard typing methods are time-consuming and are therefore impractical for identification of this clone in the course of an outbreak. Through comparative genomic study, we have previously identified several presumably unique genes of this clone: 1) PILV-like protein (pilv-l), 2) transposase, IS66-family (is-66), and a 3) phage-related protein (prp). Our aims were to 1) test for the presence of these genes using a multiplex PCR in a large, multinational collection of KPC-KP isolates and to 2) validate this assay as a typing method for the identification of the ST-258/512 clone. KPC-KP isolates (n=160) that included both ST-258/512 (group A, n=114) and non-ST-258 (group B, n=46) strains were collected from the following countries: Greece, 20; Israel, 93; Italy, 19; USA, 25; and Colombia, 3. Group B included 30 different STs from various lineages. The pilv-l gene was present in 111/114 of ST-258 isolates, including all of the KPC-negative isolates resulting in a sensitivity of 97%. Using primers for a unique ST-258 pilv-l allele resulted in a specificity of 100%. The sensitivity values of is-66 and prp genes for detecting KPC-KP ST-258 were 83 and 89%, respectively, and the specificity values were 67 and 93%, respectively. PCR for the unique pilv-l ST-258 allele provides a reliable tool for rapid detection of the ST-258 clone. This method can be helpful both in the setting of an outbreak and in a large-scale survey of KPC-KP strains.

KPC-2-encoding plasmids from Escherichia coli and Klebsiella pneumoniae in Taiwan

OBJECTIVES

Two plasmids carrying bla(KPC-2) isolated from carbapenem-resistant Escherichia coli (CR-EC) and carbapenem-resistant Klebsiella pneumoniae (CR-KP), respectively, were completely sequenced. The CR-KP strain was selected from an outbreak in 2012, and the CR-EC strain was the first blaKPC-2-carrying E. coli identified in the same carbapenem resistance monitoring programme in Taiwan.

METHODS

Antimicrobial susceptibility tests, multilocus sequence typing (MLST) and the conjugal transfer of plasmids were performed. Complete sequencing of the plasmids was performed using a shotgun approach.

RESULTS

The CR-EC and CR-KP strains in this study were determined to be ST410 and ST11, respectively, by MLST. From CR-EC, we identified a 145 kb conjugative plasmid that carries bla(KPC-2), bla(CMY-2), bla(CTX-M-3) and bla(TEM-1). The plasmid is a chimera composed of three regions related to IncI, IncN and RepFIC replicons. From CR-KP, we identified an 86.5 kb plasmid, pKPC-LK30, which carries bla(KPC-2) and bla(SHV-11). The plasmid is very similar to two bla(KPC-2)-carrying IncFII(K) plasmids, but lacks one of the replication origins and cannot conjugate.

CONCLUSIONS

The differences in cross-species transferability of the two plasmids can be explained by genetic differences between their backbones and could have resulted in the confined bla(KPC-2)-carrying CR-KP outbreak in Taiwan. Plasmid pKPC-LKEc is the first bla(KPC-2)-carrying plasmid identified from CR-EC in Taiwan. With relatively high transferability it should be closely monitored.

Complete nucleotide sequence of a blaKPC-harboring IncI2 plasmid and its dissemination in New Jersey and New York hospitals

Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains have spread worldwide and become a significant public health threat. blaKPC, the plasmid-borne KPC gene, was frequently identified on numerous transferable plasmids in different incompatibility replicon groups. Here we report the complete nucleotide sequence of a novel blaKPC-3-harboring IncI2 plasmid, pBK15692, isolated from a multidrug-resistant K. pneumoniae ST258 strain isolated from a New Jersey hospital in 2005. pBK15692 is 78 kb in length and carries a backbone that is similar to those of other IncI2 plasmids (pR721, pChi7122-3, pHN1122-1, and pSH146-65), including the genes encoding type IV pili and shufflon regions. Comparative genomics analysis of IncI2 plasmids reveals that they possess a conserved plasmid backbone but are divergent with respect to the integration sites of resistance genes. In pBK15692, the blaKPC-3-harboring Tn4401 was inserted into a Tn1331 element and formed a nested transposon. A PCR scheme was designed to detect the prevalence of IncI2 and pBK15692-like plasmids from a collection of clinical strains from six New Jersey and New York hospitals isolated between 2007 and 2011. IncI2 plasmids were found in 46.2% isolates from 318 clinical K. pneumoniae strains. Notably, 59 pBK15692-like plasmids (23%) have been identified in 256 KPC-bearing K. pneumoniae strains, and all carried KPC-3 and belong to the epidemic ST258 clone. Our study revealed that the prevalence of IncI2 plasmids has been considerably underestimated. Further studies are needed to understand the distribution of this plasmid group in other health care regions and decipher the association between IncI2 plasmids and blaKPC-3-bearing ST258 strains.

KPC-producing, multidrug-resistant Klebsiella pneumoniae sequence type 258 as a typical opportunistic pathogen

The virulence of a KPC-producing Klebsiella pneumoniae sequence type 258 (ST258) strain representing those circulating in Greece was assessed in a mouse septicemia model. The strain was virtually avirulent (50% lethal dose, >10(8) and 5 × 10(7) CFU for immunocompetent and neutropenic animals, respectively). Also, it was highly susceptible to serum killing, rapidly phagocytosed in vitro, and classified as K41, which is not among the virulent capsular types. The findings indirectly support the notion that high ST258-associated mortality is largely due to inefficient antimicrobial treatment.

A nosocomial outbreak of KPC-2-producing Klebsiella pneumoniae in a Chinese hospital: dissemination of ST11 and emergence of ST37, ST392 and ST395

In China, Klebsiella pneumoniae carbapenemase (KPC) -producing K. pneumoniae isolates have been identified. However, little is known about the spread and outbreak of KPC-producing enterobacterial pathogens. In this study, 48 non-duplicated KPC-producing isolates were analysed for genetic relatedness by pulsed-field gel electrophoresis (PFGE), antimicrobial susceptibility by E-test, and sequence type (ST) by multilocus sequence typing. S1-PFGE and Southern blot were used for plasmid profiling, and PCR and subsequent sequencing were performed to determine the effects of genetic background on the blaKPC gene. From December 2011 to June 2012, an outbreak of the KPC-2-producing K. pneumoniae was observed. The 48 isolates of K. pneumoniae are categorized into eight PFGE types (A1, A2, A3, A4, B, C, D and E). The predominant pathogens of the outbreak were strains with PFGE types A1, A2 and A3, which all belong to ST11. Furthermore, ST37, ST392 and ST395 KPC-2-producing K. pneumoniae isolates have also been sporadically identified. The blaKPC-2 -carrying plasmids vary in size from 30 to 220 kb. The genetic environments of the blaKPC-2 gene for most strains were consistent with the genetic structure of blaKPC-2 on the plasmid pKP048. In conclusion, the dissemination and outbreak of KPC-2-producing K. pneumoniae isolates in this study appeared to be clonal, and ST11 K. pneumoniae was the predominant clone attributed to the outbreak. This is the first study to report the emergence and spread of KPC-producing K. pneumoniae ST392 and ST395 worldwide. Our findings suggest that horizontal transfer of Tn3-based transposons might mediate the spread of blaKPC-2 gene between different K. pneumoniae clones in China.

Reversion to susceptibility of a carbapenem-resistant clinical isolate of Klebsiella pneumoniae producing KPC-3

OBJECTIVES

We report the case of a kidney-transplant patient, suffering an intra-abdominal abscess at the surgical site caused by a carbapenem-resistant ST258 Klebsiella pneumoniae clone, producing the KPC-3 carbapenemase. Under tigecycline treatment, the patient developed a sepsis caused by a carbapenem-susceptible ST258 K. pneumoniae strain. Complete DNA sequences of the plasmids carried by the resistant and susceptible strains from this patient were determined.

METHODS

The complete DNA sequences of plasmids were obtained by applying the 454 Genome Sequencer FLX-PLUS procedure on a library constructed of total plasmid DNA purified from the carbapenem-resistant and -susceptible strains.

RESULTS

In the carbapenem-resistant strain, four plasmids encoding 24 resistance genes, including blaKPC-3, and two putative virulence clusters were detected. In the susceptible strain, large rearrangements occurred in the KPC-carrying plasmid, causing the deletion of the entire Tn4401::blaKPC-3 transposon, with the consequent reversion of the strain to carbapenem susceptibility. The patient was successfully treated with carbapenems and fully recovered.

CONCLUSIONS

The description of the plasmid content in these two strains gives interesting insights into the plasticity of KPC-carrying plasmids in K. pneumoniae.