Population Structure, Antibiotic Resistance, and Uropathogenicity of Klebsiella variicola

Native CRISPR-Cas-based programmable multiplex gene repression in Klebsiella variicola

Klebsiella variicola is a Gram-negative bacterium that is frequently isolated from a wide variety of natural niches. It is a ubiquitous opportunistic pathogen that can cause diverse infections in plants, animals, and humans. It also has significant biotechnological potential. However, due to the lack of efficient genetic tools, the molecular basis contributing to the pathogenesis and beneficial activities of K. variicola remains poorly understood. In this study, we found and characterized a native type I-E CRISPR-Cas system in a recently isolated K. variicola strain KV-1. The system cannot cleave target DNA sequences due to the inactivation of the Cas3 nuclease by a transposable element but retains the activity of the crRNA-guided Cascade binding to the target DNA sequence. A targeting plasmid carrying a mini-CRISPR to encode a crRNA was designed and introduced into the KV-1 strain, which successfully repurposed the native type I-E CRISPR-Cas system to inhibit the expression of the target gene efficiently and specifically. Moreover, by creating a mini-CRISPR to encode multiple crRNAs, multiplex gene repression was achieved by providing a single targeting plasmid. This work provides the first native CRISPR-Cas-based tool for programmable multiplex gene repression in K. variicola, which will facilitate studying the pathogenic mechanism of K. variicola and enable metabolic engineering to produce valuable bioproducts.

Genomic insight on Klebsiella variicola isolated from wastewater treatment plant has uncovered a novel bacteriophage

Klebsiella variicola is considered an emerging pathogen, which may colonize a variety of hosts, including environmental sources. Klebsiella variicola investigated in this study was obtained from an influent wastewater treatment plant in the North-West Province, South Africa. Whole genome sequencing was conducted to unravel the genetic diversity and antibiotic resistance patterns of K. variicola. Whole genome core SNP phylogeny was employed on publicly available 170 genomes. Furthermore, capsule types and antibiotic resistance genes, particularly beta-lactamase and carbapenems genes were investigated from the compared genomes. A 38 099 bp bacteriophage was uncovered alongside with K. variicola genome. Whole genome sequencing revealed that the extended beta-lactamase blaLEN (75.3%) of the beta-lactamase is dominant among compared K. variicola strains. The identified IncF plasmid AA035 confers resistance genes of metal and heat element subtypes, i.e., silver, copper, and tellurium. The capsule type KL107-D1 is a predominant capsule type present in 88.2% of the compared K. variicola genomes. The phage was determined to be integrase-deficient consisting of a fosB gene associated with fosfomycin resistance and clusters with the Wbeta genus Bacillus phage group. In silico analysis showed that the phage genome interacts with B. cereus as opposed to K. variicola strain T2. The phage has anti-repressor proteins involved in the lysis-lysogeny decision. This phage will enhance our understanding of its impact on bacterial dissemination and how it may affect disease development and antibiotic resistance mechanisms in wastewater treatment plants. This study highlights the need for ongoing genomic epidemiological surveillance of environmental K. variicola isolates.

Comparative Genomics Revealing the Genomic Characteristics of Klebsiella variicola Clinical Isolates in China

Klebsiella variicola is an opportunistic pathogen often misidentified as Klebsiella pneumoniae, leading to misdiagnoses and inappropriate treatment in clinical settings. The genetic and molecular characteristics of clinically isolated K. variicola remain largely unexplored. We aim to fill this knowledge gap by examining the genomic properties of and evolutionary relationships between clinical isolates of K. variicola. The genomic data of 70 K. variicola strains were analyzed using whole-genome sequencing. A phylogenetic tree was generated based on the gene sequences from these K. variicola strains and public databases. Among the K. variicola strains, the drug resistance genes with the highest carrying rates were beta-lactamase and aminoglycoside. Locally isolated strains had a higher detection rate for virulence genes than those in public databases, with yersiniabactin genes being the most prevalent. The K locus types and MLST subtypes of the strains exhibited a dispersed distribution, with O3/O3a being the predominant subtype within the O category. In total, 28 isolates carried both IncFIB(K)_Kpn3 and IncFII_pKP91 replicons. This study underscores the importance of developing more effective diagnostic tools and therapeutic strategies for K. variicola infections. The continued surveillance and monitoring of K. variicola strains is essential for understanding the epidemiology of infections and informing public health strategies.

Global Emergence and Genomic Epidemiology of blaNDM-Carrying Klebsiella variicola

Purpose

Klebsiella variicola has emerged as a human pathogen in the past decade. Here, we present findings related to a K. variicola strain carrying the blaNDM-1 gene, which was isolated from a urinary tract infection in China. Global transmission dynamics and genomic epidemiology of blaNDM-carrying K. variicola were further investigated.

Material and Methods

The complete genome sequence of the strain was determined using the Illumina NovaSeq 6000 and Nanopore MinION sequencer. Genomic features and resistance mechanisms were analyzed through diverse bioinformatics approaches. Additionally, genome sequences of K. variicola strains carrying blaNDM were retrieved from the NCBI database, and a comprehensive analysis of the global dissemination trends of these strains was conducted.

Results

K. variicola strain 353 demonstrated resistance to multiple antimicrobials, including carbapenems. Within its genome, we identified fourteen antimicrobial resistance genes associated with β-lactam, aminoglycoside, fosfomycin, quinolone, trimethoprim, rifamycin, and sulfonamide resistance. The carbapenem-resistant gene blaNDM-1 was located on an IncU-type plasmid spanning 294,608 bp and flanked by ISCR1 and IS26. Downstream of blaNDM-1, we identified an Intl1 element housing numerous antibiotic resistance genes. A comprehensive search of the NCBI database revealed 72 K. variicola strains carrying blaNDM from twelve different countries, predominantly from clinical sources, with the highest prevalence observed in the USA and China. A total of 28 distinct sequence types (STs) were identified, with ST115 being the most prevalent, followed by ST60.

Conclusion

In summary, this study presents the genomic characterization of a K. variicola strain carrying blaNDM-1 on an IncU-type plasmid. The research highlights the global dissemination of blaNDM-carrying K. variicola, observed in both healthcare settings and natural environments. Our data have revealed a diverse array of antimicrobial resistance determinants in K. variicola, providing valuable insights that could aid in the development of strategies for the prevention, diagnosis, and treatment of K. variicola infections.

Comparative genomics reveals the correlations of stress response genes and bacteriophages in developing antibiotic resistance of Staphylococcus saprophyticus

IMPORTANCE

Staphylococcus saprophyticus is the second most common bacteria associated with urinary tract infections (UTIs) in women. The antimicrobial treatment regimen for uncomplicated UTI is normally nitrofurantoin, trimethoprim-sulfamethoxazole (TMP-SMX), or a fluoroquinolone without routine susceptibility testing of S. saprophyticus recovered from urine specimens. However, TMP-SMX-resistant S. saprophyticus has been detected recently in UTI patients, as well as in our cohort. Herein, we investigated the understudied resistance patterns of this pathogenic species by linking genomic antibiotic resistance gene (ARG) content to susceptibility phenotypes. We describe ARG associations with known and novel SCCmec configurations as well as phage elements in S. saprophyticus, which may serve as intervention or diagnostic targets to limit resistance transmission. Our analyses yielded a comprehensive database of phenotypic data associated with the ARG sequence in clinical S. saprophyticus isolates, which will be crucial for resistance surveillance and prediction to enable precise diagnosis and effective treatment of S. saprophyticus UTIs.

Diagnostic and commensal Staphylococcus pseudintermedius genomes reveal niche adaptation through parallel selection of defense mechanisms

Staphylococcus pseudintermedius is historically understood as a prevalent commensal and pathogen of dogs, though modern clinical diagnostics reveal an expanded host-range that includes humans. It remains unclear whether differentiation across S. pseudintermedius populations is driven primarily by niche-type or host-species. We sequenced 501 diagnostic and commensal isolates from a hospital, veterinary diagnostic laboratory, and within households in the American Midwest, and performed a comparative genomics investigation contrasting human diagnostic, animal diagnostic, human colonizing, pet colonizing, and household-surface S. pseudintermedius isolates. Though indistinguishable by core and accessory gene architecture, diagnostic isolates harbor more encoded and phenotypic resistance, whereas colonizing and surface isolates harbor similar CRISPR defense systems likely reflective of common household phage exposures. Furthermore, household isolates that persist through anti-staphylococcal decolonization report elevated rates of base-changing mutations in - and parallel evolution of - defense genes, as well as reductions in oxacillin and trimethoprim-sulfamethoxazole susceptibility. Together we report parallel niche-specific bolstering of S. pseudintermedius defense mechanisms through gene acquisition or mutation.

Plasmids of the incompatibility group FIBK occur in Klebsiella variicola from diverse ecological niches

Plasmids play a fundamental role in the evolution of bacteria by allowing them to adapt to different environments and acquire, through horizontal transfer, genes that confer resistance to different classes of antibiotics. Using the available in vitro and in silico plasmid typing systems, we analyzed a set of isolates and public genomes of K. variicola to study its plasmid diversity. The resistome, the plasmid multilocus sequence typing (pMLST), and molecular epidemiology using the MLST system were also studied. A high frequency of IncF plasmids from human isolates but lower frequency from plant isolates were found in our strain collection. In silico detection revealed 297 incompatibility (Inc) groups, but the IncFIBK (216/297) predominated in plasmids from human and environmental samples, followed by IncFIIK (89/297) and IncFIA/FIA(HI1) (75/297). These Inc groups were associated with clinically important ESBL (CTX-M-15), carbapenemases (KPC-2 and NDM-1), and colistin-resistant genes which were associated with major sequence types (ST): ST60, ST20, and ST10. In silico MOB typing showed 76% (311/404) of the genomes contained one or more of the six relaxase families with MOBF being most abundant. We identified untypeable plasmids carrying blaKPC-2, blaIMP-1, and blaSHV-187 but for which a relaxase was found; this may suggest that novel plasmid structures could be emerging in this bacterial species. The plasmid content in K. variicola has limited diversity, predominantly composed of IncFIBK plasmids dispersed in different STs. Plasmid detection using the replicon and MOB typing scheme provide a broader context of the plasmids in K. variicola. This study showed that whole-sequence-based typing provides current insights of the prevalence of plasmid types and their association with antimicrobial resistant genes in K. variicola obtained from humans and environmental niches.

Fast genome-based delimitation of Enterobacterales species

Average Nucleotide Identity (ANI) is becoming a standard measure for bacterial species delimitation. However, its calculation can take orders of magnitude longer than similarity estimates based on sampling of short nucleotides, compiled into so-called sketches. These estimates are widely used. However, their variable correlation with ANI has suggested that they might not be as accurate. For a where-the-rubber-meets-the-road assessment, we compared two sketching programs, mash and dashing, against ANI, in delimiting species among Esterobacterales genomes. Receiver Operating Characteristic (ROC) analysis found Area Under the Curve (AUC) values of 0.99, almost perfect species discrimination for all three measures. Subsampling to avoid over-represented species reduced these AUC values to 0.92, still highly accurate. Focused tests with ten genera, each represented by more than three species, also showed almost identical results for all methods. Shigella showed the lowest AUC values (0.68), followed by Citrobacter (0.80). All other genera, Dickeya, Enterobacter, Escherichia, Klebsiella, Pectobacterium, Proteus, Providencia and Yersinia, produced AUC values above 0.90. The species delimitation thresholds varied, with species distance ranges in a few genera overlapping the genus ranges of other genera. Mash was able to separate the E. coli + Shigella complex into 25 apparent phylogroups, four of them corresponding, roughly, to the four Shigella species represented in the data. Our results suggest that fast estimates of genome similarity are as good as ANI for species delimitation. Therefore, these estimates might suffice for covering the role of genomic similarity in bacterial taxonomy, and should increase confidence in their use for efficient bacterial identification and clustering, from epidemiological to genome-based detection of potential contaminants in farming and industry settings.

Emergence of novel non-aggregative variants under negative frequency-dependent selection in Klebsiella variicola

Klebsiella variicola is an emergent human pathogen causing diverse infections, some of which in the urinary tract. However, little is known about the evolution and maintenance of genetic diversity in this species, the molecular mechanisms and their population dynamics. Here, we characterized the emergence of a novel rdar-like (rough and dry) morphotype which is contingent both on the genetic background and the environment. We show that mutations in either the nitrogen assimilation control gene (nac) or the type III fimbriae regulator, mrkH, suffice to generate rdar-like colonies. These morphotypes are primarily selected for the reduced inter-cellular aggregation as a result of MrkH loss-of-function which reduces type 3 fimbriae expression. Additionally, these clones also display increased growth rate and reduced biofilm formation. Direct competitions between rdar and wild type clones show that mutations in mrkH provide large fitness advantages. In artificial urine, the morphotype is under strong negative frequency-dependent selection and can socially exploit wild type strains. An exhaustive search for mrkH mutants in public databases revealed that ca 8% of natural isolates analysed had a truncated mrkH gene many of which were due to insertions of IS elements, including a reported clinical isolate with rdar morphology. These strains were rarely hypermucoid and often isolated from human, mostly from urine and blood. The decreased aggregation of these mutants could have important clinical implications as we hypothesize that such clones could better disperse within the host allowing colonisation of other body sites and potentially leading to systemic infections.

Uncharacterized and lineage-specific accessory genes within the Proteus mirabilis pan-genome landscape

Proteus mirabilis is a Gram-negative bacterium recognized for its unique swarming motility and urease activity. A previous proteomic report on four strains hypothesized that, unlike other Gram-negative bacteria, P. mirabilis may not exhibit significant intraspecies variation in gene content. However, there has not been a comprehensive analysis of large numbers of P. mirabilis genomes from various sources to support or refute this hypothesis. We performed comparative genomic analysis on 2,060 Proteus genomes. We sequenced the genomes of 893 isolates recovered from clinical specimens from three large US academic medical centers, combined with 1,006 genomes from NCBI Assembly and 161 genomes assembled from Illumina reads in the public domain. We used average nucleotide identity (ANI) to delineate species and subspecies, core genome phylogenetic analysis to identify clusters of highly related P. mirabilis genomes, and pan-genome annotation to identify genes of interest not present in the model P. mirabilis strain HI4320. Within our cohort, Proteus is composed of 10 named species and 5 uncharacterized genomospecies. P. mirabilis can be subdivided into three subspecies; subspecies 1 represented 96.7% (1,822/1,883) of all genomes. The P. mirabilis pan-genome includes 15,399 genes outside of HI4320, and 34.3% (5,282/15,399) of these genes have no putative assigned function. Subspecies 1 is composed of several highly related clonal groups. Prophages and gene clusters encoding putatively extracellular-facing proteins are associated with clonal groups. Uncharacterized genes not present in the model strain P. mirabilis HI4320 but with homology to known virulence-associated operons can be identified within the pan-genome. IMPORTANCE Gram-negative bacteria use a variety of extracellular facing factors to interact with eukaryotic hosts. Due to intraspecies genetic variability, these factors may not be present in the model strain for a given organism, potentially providing incomplete understanding of host-microbial interactions. In contrast to previous reports on P. mirabilis, but similar to other Gram-negative bacteria, P. mirabilis has a mosaic genome with a linkage between phylogenetic position and accessory genome content. P. mirabilis encodes a variety of genes that may impact host-microbe dynamics beyond what is represented in the model strain HI4320. The diverse, whole-genome characterized strain bank from this work can be used in conjunction with reverse genetic and infection models to better understand the impact of accessory genome content on bacterial physiology and pathogenesis of infection.

Emergence of OXA-484-Producing Klebsiella variicola in China

Purpose

The frequent and inappropriate use of antibiotics has caused a dramatic rise in the number, species, and degree of multi-drug resistant bacteria, making them more prevalent and difficult to treat. In this context, the aim of the present study was to characterize the OXA-484-producing strains isolated from a perianal swab of a patient by using whole-genome analysis.

Patients and Methods

In this study, carbapenemase-producing Klebsiella variicola was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), average nucleotide identity (ANI) and PCR. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting were utilized to characterize the plasmid profiles of K. variicola 4717. In particular, WGS was performed to obtain genomic information on this clinical isolate, and assemble all the plasmids of the bla _OXA-484-harboring strain.

Results

The antimicrobial susceptibility pattern of K. variicola 4717 revealed that it was resistant to a range of antibiotics, including aztreonam, imipenem, meropenem, ceftriaxone, cefotaxime, ceftazidime, levofloxacin, ciprofloxacin, piperacillin-tazobactam, methylene-sulfamer oxazole, amoxicillin-clavulanic acid, cefepime, and tigecycline. Its susceptibility to chloromycin was intermediate, while it was still susceptible to amikacin, gentamicin, fosfomycin, and polymyxin B. The presence of two companion plasmids, p4717_1 and p4717_2, together with a plasmid carrying the bla _OXA-484 gene was observed. An in-depth investigation of p4717-OXA-484 uncovered that it is an IncX3-type plasmid and shares a similar segment encoded by IS26. Given the similar genetic background, it was conceivable that bla _OXA-484 could have developed from bla _OXA-181 through a series of mutations.

Conclusion

Herein, we described the first genome sequence of K. variicola strain harbouring the class D β-actamase bla _OXA-484 in an Inc-X3-type plasmid. Our work also uncovered the genetic characterization of K. variicola 4717 and the importance of initiating antimicrobial detection promptly.

Outpatient Clonal Propagation and Rapid Regional Establishment of an Emergent Carbapenem-Resistant Acinetobacter baumannnii Lineage Sequence Type 499Pas

Eliminating carbapenem-resistant Acinetobacter baumannii (CRAb) disease requires comprehensive knowledge of how this noncommensal organism propagates among at-risk hosts. We molecularly characterized an ongoing surge of CRAb cases among patients in a Midwest US healthcare system, which coincided with sustained reductions in hospital-acquired CRAb infections and falloffs of cases associated with distinctly more resistant antibiotypes. Genome sequencing revealed surge isolates belonged to an emergent Pasteur scheme sequence type 499 and comprised multiple contemporaneous clonal clusters. Detailed query of health records revealed no consistent hospital source but instead identified various outpatient healthcare settings linked to cluster cases. We show that CRAb can rapidly establish a regional presence even without gains in breadth of antibiotic resistance and negligible contribution from sustained intrahospital transmission. As CRAb lineages may sidestep control efforts via outpatient epidemiological niches, our approach can be implemented to investigate outpatient CRAb propagation and inform subsequent local surveillance outside hospital settings.

Improvement and Validation of a Multi-Locus Variable Number of Tandem Repeats Analysis (MLVA8+) for Klebsiella pneumoniae, Klebsiella variicola, and Klebsiella quasipneumoniae

The genotyping of the multidrug-resistant Klebsiella pneumoniae species complex is essential to identify outbreaks and to track their source and spread. The aim of this study was to improve and extend the typeability, availability, cost and time efficiency of an existing multi-locus VNTR analysis (MLVA). A modified scheme (MLVA8+) was adopted and validated for strain-level differentiation of the three Klebsiella species involved in human pathology. A diverse set of 465 K. pneumoniae clinical isolates from 22 hospitals and 3 outpatient laboratories in Bulgaria were studied, where 315 were carbapenem-resistant. The MLVA8+ typeability was significantly improved and the typing data were validated against 158 isolates which were previously typed by WGS. The MLVA8+ results were highly concordant with the classic 7-locus MLST and the novel K. variicola MLST, but had greater congruency coefficients (adjusted Wallace). A major advantage was the differentiation of the hybrid cluster ST258 into its corresponding clades. Furthermore, the applicability of MLVA8+ was demonstrated by conducting a retrospective investigation of the intra-hospital spread of blaKPC-, blaNDM- and blaOXA-48-like producers. The MLVA8+ has improved utility and extended typing scope to K. variicola and K. quasipneumoniae, while its cost and time-to-result were reduced.

Antibiotic resistance surveillance of Klebsiella pneumoniae complex is affected by refined MALDI-TOF identification, Swiss data, 2017 to 2022

Background

Modern laboratory methods such as next generation sequencing and MALDI-TOF allow identification of novel bacterial species. This can affect surveillance of infections and antimicrobial resistance. From 2017, increasing numbers of medical microbiology laboratories in Switzerland differentiated Klebsiella variicola from Klebsiella pneumoniae complex using updated MALDI-TOF databases, whereas many laboratories still report them as K. pneumoniae or K. pneumoniae complex.

Aim

Our study explored whether separate reporting of K. variicola and the Klebsiella pneumoniae complex affected the ANRESIS surveillance database.

Methods

We analysed antibiotic susceptibility rates and specimen types of K. variicola and non-K. variicola-K. pneumoniae complex isolates reported by Swiss medical laboratories to the ANRESIS database (Swiss Centre for Antibiotic Resistance) from January 2017 to June 2022.

Results

Analysis of Swiss antimicrobial resistance data revealed increased susceptibility rates of K. variicola compared with species of the K. pneumoniae complex other than K. variicola in all six antibiotic classes tested. This can lead to underestimated resistance rates of K. pneumoniae complex in laboratories that do not specifically identify K. variicola. Furthermore, K. variicola strains were significantly more often reported from blood and primarily sterile specimens than isolates of the K. pneumoniae complex other than K. variicola, indicating increased invasiveness of K. variicola.

Conclusion

Our data suggest that refined differentiation of the K. pneumoniae complex can improve our understanding of its taxonomy, susceptibility, epidemiology and clinical significance, thus providing more precise information to clinicians and epidemiologists.

Genomic Characterization of a Carbapenemase-Producing, Extensively Drug-Resistant Klebsiella michiganensis Strain from a Renal Abscess Patient

We describe an extensively drug-resistant Klebsiella michiganensis strain, Kmfe267, which was originally isolated from a renal abscess patient. The strain carries the blaNDM-5 gene, which encodes a New Delhi metallo-β-lactamase. The complete genome of the strain contains a 5.9-Mb chromosome and 5 plasmids.

Conserved FimK Truncation Coincides with Increased Expression of Type 3 Fimbriae and Cultured Bladder Epithelial Cell Association in Klebsiella quasipneumoniae

Klebsiella spp. commonly cause both uncomplicated urinary tract infection (UTI) and recurrent UTI (rUTI). Klebsiella quasipneumoniae, a relatively newly defined species of Klebsiella, has been shown to be metabolically distinct from Klebsiella pneumoniae, but its type 1 and type 3 fimbriae have not been studied. K. pneumoniae uses both type 1 and type 3 fimbriae to attach to host epithelial cells. The type 1 fimbrial operon is well conserved between Escherichia coli and K. pneumoniae apart from fimK, which is unique to Klebsiella spp. FimK contains an N-terminal DNA binding domain and a C-terminal phosphodiesterase (PDE) domain that has been hypothesized to cross-regulate type 3 fimbriae expression via modulation of cellular levels of cyclic di-GMP. Here, we find that a conserved premature stop codon in K. quasipneumoniae fimK results in truncation of the C-terminal PDE domain and that K quasipneumoniae strain KqPF9 cultured bladder epithelial cell association and invasion are dependent on type 3 but not type 1 fimbriae. Further, we show that basal expression of both type 1 and type 3 fimbrial operons as well as cultured bladder epithelial cell association is elevated in KqPF9 relative to uropathogenic K. pneumoniae TOP52. Finally, we show that complementation of KqPF9ΔfimK with the TOP52 fimK allele reduced type 3 fimbrial expression and cultured bladder epithelial cell attachment. Taken together these data suggest that the C-terminal PDE of FimK can modulate type 3 fimbrial expression in K. pneumoniae and its absence in K. quasipneumoniae may lead to a loss of type 3 fimbrial cross-regulation. IMPORTANCE K. quasipneumoniae is often indicated as the cause of opportunistic infections, including urinary tract infection, which affects >50% of women worldwide. However, the virulence factors of K. quasipneumoniae remain uninvestigated. Prior to this work, K. quasipneumoniae and K. pneumoniae had only been distinguished phenotypically by metabolic differences. This work contributes to the understanding of K. quasipneumoniae by evaluating the contribution of type 1 and type 3 fimbriae, which are critical colonization factors encoded by all Klebsiella spp., to K. quasipneumoniae bladder epithelial cell attachment in vitro. We observe clear differences in bladder epithelial cell attachment and regulation of type 3 fimbriae between uropathogenic K. pneumoniae and K. quasipneumoniae that coincide with a structural difference in the fimbrial regulatory gene fimK.

Do plasmids containing heavy metal resistance genes play a role in neonatal sepsis and invasive disease caused by Klebsiella pneumoniae and Klebsiella variicola?

Introduction. Klebsiella species are some of those most implicated in neonatal sepsis. However, many isolates from infections appear unremarkable; they are generally susceptible to antibiotics and often of sporadic types not associated with virulence.Hypothesis/Gap Statement. Investigation is needed to identify if such isolates have virulence characteristics.Aim. To sequence multiple isolates of a range of types from cases of neonatal invasive disease to identify elements that may explain their virulence, and to determine if such elements are more common among these isolates than generally.Methodology. In total, 14 isolates of K. pneumoniae/K. variicola belonging to 13 distinct types from blood or CSF from neonatal infections were sequenced using long-read nanopore technology. PCR assays were used to screen a general set of isolates for heavy metal resistance genes arsC, silS and merR.Results. Overall, 12/14 isolates carried one or more plasmids. Ten carried a large plasmid (186 to 310 kb) containing heavy metal resistance genes associated with hypervirulence plasmids, with most (nine) carrying genes for resistance to copper, silver and one other heavy metal (arsenic, tellurite or mercury), but lacking the genes encoding capsule-upregulation and siderophores. Most isolates (9/14) lacked any additional antibiotic resistance genes other than those intrinsic in the species. However, a representative of an outbreak strain carried a plasmid containing bla _CTX-M-15, qnrS1, aac3_IIa, dfrA17, sul1, mph(A), tet(A), bla _TEM1B and aadA5, but no heavy metal resistance genes. arsC, silS and merR were widely found among 100 further isolates screened, with most carbapenemase-gene-positive isolates (20/27) carrying at least one.Conclusion. Plasmids containing heavy metal resistance genes were a striking feature of isolates from neonatal sepsis but are widely found. They share elements in common with virulence and antibiotic resistance plasmids, perhaps providing a basis from which such plasmids evolve.

Clinical characteristics and antimicrobial susceptibility of Klebsiella pneumoniae, Klebsiella variicola and Klebsiella quasipneumoniae isolated from human urine in Japan

Introduction. The three Klebsiella species K. pneumoniae, K. variicola and K. quasipneumoniae are difficult to distinguish, owing to their similar biochemical properties, and are often confused in medical practice.Gap statement. There is a scarcity of data comparing the clinical characteristics and antimicrobial susceptibility of K. pneumoniae, K. variicola and K. quasipneumoniae. We believe that knowledge of the characteristics of each species will help in their better identification. Further, knowing the antimicrobial susceptibility of the species will help physicians in prescribing an effective treatment course for Klebsiella infections.Aim. This study aimed to determine the clinical characteristics and antimicrobial resistance of K. pneumoniae, K. variicola and K. quasipneumoniae isolated from human urine samples.Methodology. This study included 125 K. pneumoniae strains isolated from human urine samples. Multiplex polymerase chain reaction was performed to identify K. pneumoniae, K. variicola and K. quasipneumoniae. We retrospectively investigated the patient background, complications of bacteraemia, antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL).Results. We identified 84 (67.2 %), 31 (24.8 %) and 10 strains (8 .0%) of K. pneumoniae, K. variicola and K. quasipneumoniae, respectively. There was no difference in patient background and frequency of bacteraemia complications among these species. K. pneumoniae was significantly less susceptible than K. variicola to ampicillin/sulbactam (P=0.03) and piperacillin (P<0.01). Furthermore, K. pneumoniae (79.8 %) was less susceptible to trimethoprim/sulfamethoxazole than K. variicola (96.8 %) and K. quasipneumoniae (100 %). There were nine ESBL-producing strains (7.2 %), all of which were K. pneumoniae.Conclusion. There was no difference in patient background and frequency of bacteraemia complications between K. pneumoniae, K. variicola and K. quasipneumoniae isolated from urine. The three Klebsiella species showed a varying extent of antimicrobial susceptibility and ESBL production, and accurate identification is needed to understand the epidemiology of these species.

Genomic dissection of Klebsiella pneumoniae infections in hospital patients reveals insights into an opportunistic pathogen

Klebsiella pneumoniae is a major cause of opportunistic healthcare-associated infections, which are increasingly complicated by the presence of extended-spectrum beta-lactamases (ESBLs) and carbapenem resistance. We conducted a year-long prospective surveillance study of K. pneumoniae clinical isolates in hospital patients. Whole-genome sequence (WGS) data reveals a diverse pathogen population, including other species within the K. pneumoniae species complex (18%). Several infections were caused by K. variicola/K. pneumoniae hybrids, one of which shows evidence of nosocomial transmission. A wide range of antimicrobial resistance (AMR) phenotypes are observed, and diverse genetic mechanisms identified (mainly plasmid-borne genes). ESBLs are correlated with presence of other acquired AMR genes (median n = 10). Bacterial genomic features associated with nosocomial onset are ESBLs (OR 2.34, p = 0.015) and rhamnose-positive capsules (OR 3.12, p < 0.001). Virulence plasmid-encoded features (aerobactin, hypermucoidy) are observed at low-prevalence (<3%), mostly in community-onset cases. WGS-confirmed nosocomial transmission is implicated in just 10% of cases, but strongly associated with ESBLs (OR 21, p < 1 × 10-11). We estimate 28% risk of onward nosocomial transmission for ESBL-positive strains vs 1.7% for ESBL-negative strains. These data indicate that K. pneumoniae infections in hospitalised patients are due largely to opportunistic infections with diverse strains, with an additional burden from nosocomially-transmitted AMR strains and community-acquired hypervirulent strains.

Multidrug-Resistant Klebsiella variicola Isolated in the Urine of Healthy Bovine Heifers, a Potential Risk as an Emerging Human Pathogen

Klebsiella variicola, a member of Klebsiella pneumoniae complex, is found to infect plants, insects, and animals and is considered an emerging pathogen in humans. While antibiotic resistance is often prevalent among K. variicola isolates from humans, this has not been thoroughly investigated in isolates from nonhuman sources. Prior evidence suggests that K. variicola can be transmitted between agricultural products as well as between animals, and the use of antibiotics in agriculture has increased antibiotic resistance in other emerging pathogens. Furthermore, in animals that contain K. variicola as a normal member of the rumen microbiota, the same bacteria can also cause infections, such as clinical mastitis in dairy cows. Here, we describe K. variicola UFMG-H9 and UFMG-H10, both isolated from the urine of healthy Gyr heifers. These two genomes represent the first isolates from the urine of cattle and exhibit greater similarity with strains from the human urinary tract than isolates from bovine fecal or milk samples. Unique to the UFMG-H9 genome is the presence of flagellar genes, the first such observation for K. variicola. Neither of the sampled animals had symptoms associated with K. variicola infection, even though genes associated with virulence and antibiotic resistance were identified in both strains. Both strains were resistant to amoxicillin, erythromycin, and vancomycin, and UFMG-H10 is resistant to fosfomycin. The observed resistances emphasize the concern regarding the emergence of this species as a human pathogen given its circulation in healthy livestock animals. IMPORTANCE Klebsiella variicola is an opportunistic pathogen in humans. It also has been associated with bovine mastitis, which can have significant economic effects. While numerous isolates have been sequenced from human infections, only 12 have been sequenced from cattle (fecal and milk samples) to date. Recently, we discovered the presence of K. variicola in the urine of two healthy heifers, the first identification of K. variicola in the bovine urinary tract and the first confirmed K. variicola isolate encoding for flagella-mediated motility. Here, we present the genome sequences and analysis of these isolates. The bovine urinary genomes are more similar to isolates from the human urinary tract than they are to other isolates from cattle, suggesting niche specialization. The presence of antibiotic resistance genes is concerning, as prior studies have found transmission between animals. These findings are important to understand the circulation of K. variicola in healthy livestock animals.

Whole genome sequencing of Klebsiella pneumoniae clinical isolates sequence type 627 isolated from Egyptian patients

Klebsiella pneumoniae is considered a threat to public health especially due to multidrug resistance emergence. It is largely oligoclonal based on multi-locus sequence typing (MLST); in Egypt, ST 627 was recently detected. Despites the global dissemination of this ST, there is still paucity of information about it. Herein, we used 4 K. pneumoniae ST627 for whole genome sequencing utilizing an Illumina MiSeq platform. Genome sequences were examined for resistance and virulence determinants, capsular types, plasmids, insertion sequences, phage regions, and Clustered Regularly Interspaced Palindromic Repeats (CRISPR) regions using bioinformatic analysis. The molecular characterization revealed 15 and 65 antimicrobial resistance and virulence genes, respectively. Resistance genes such as tet(D), aph(3’’)-Ib, aph(6)-Id, blaTEM-234, fosA, and fosA6; were mainly responsible for tetracycline, aminoglycoside, and fosfomycin resistance; respectively. The capsular typing revealed that the four strains are KL-24 and O1v1. One plasmid was found in all samples known as pC17KP0052-1 and another plasmid with accession no. NZ_CP032191.1 was found only in K90. IncFIB(K) and IncFII(K) are two replicons found in all samples, while ColRNAI replicon was found only in K90. Entero P88, Salmon SEN5, and Klebsi phiKO2 intact phage regions were identified. All samples harbored CRISPR arrays including CRISPR1 and CRISPR2. Our results shed light on critical tasks of mobile genetic elements in ST 627 in antibiotic resistance spreading.

Reduction of gastrointestinal tract colonization by Klebsiella quasipneumoniae using antimicrobial protein KvarIa

Background

Klebsiella quasipneumoniae is an opportunistic pathogen causing antibiotic-resistant infections of the gastrointestinal tract in many clinical cases. Orally delivered bioactive Klebsiella-specific antimicrobial proteins, klebicins, could be a promising method to eradicate Klebsiella species infecting the gut.

Methods

Mouse infection model was established based on infection of antibiotic-treated BALB/C mice with K. quasipneumoniae strain DSM28212. Four study groups were used (3 animals/group) to test the antimicrobial efficacy of orally delivered klebicin KvarIa: vehicle-only group (control, phosphate-buffered saline), and other three groups with bacteria, antibiotic therapy and 100 µg of uncoated Kvarla, 100 µg coated KvarIa, 1000 µg coated-KvarIa. Because of the general sensitivity of bacteriocins to gastroduodenal proteases, Kvarla doses were coated with Eudragit®, a GMP-certified formulation agent that releases the protein at certain pH. The coating treatment was selected based on measurements of mouse GI tract pH. The quantity of Klebsiella haemolysin gene (khe) in faecal samples of the study animals was used to quantify the presence of Klebsiella.

Results

GI colonization of K. quasipneumoniae was achieved only in the antibiotic-treated mice groups. Significant changes in khe marker quantification were found after the use of Eudragit® S100 formulated klebicin KvarIa, at both doses, with a significant reduction of K. quasipneumoniae colonization compared to the vehicle-only control group.

Conclusions

Mouse GI tract colonization with K. quasipneumoniae can be achieved if natural gut microbiota is suppressed by prior antibiotic treatment. The study demonstrates that GI infection caused by K. quasipneumoniae can be significantly reduced using Eudragit®-protected klebicin KvarIa.

Fatal community-acquired bloodstream infection caused by Klebsiella variicola: A case report

BACKGROUND

Klebsiella pneumoniae (K. pneumoniae) is an infective microorganism of worldwide concern because of its varied manifestations and life-threatening potential. Genetic analyses have revealed that subspecies of K. pneumoniae exhibit higher virulence and mortality. However, infections with Klebsiella subspecies are often misdiagnosed and underestimated in the clinic because of difficulties in distinguishing K. pneumoniae from its subspecies using routine tests. This case study reports the rapid and fatal effects of K. pneumoniae subspecies.

CASE SUMMARY

A 52-year-old male patient was febrile and admitted to hospital. Examinations excluded viral and fungal causes along with mycoplasma/chlamydia and parasitic infections. Bacterial cultures revealed blood-borne K. pneumoniae sensitive to carbapenem antibiotics, although corresponding treatment failed to improve the patient’s symptoms. His condition worsened and death occurred within 72 h of symptom onset from sepsis shock. Application of the PMseq-DNA Pro high throughput gene detection assay was implemented with results obtained after death showing a mixed infection of K. pneumoniae and Klebsiella variicola (K. variicola). Clinical evidence suggested that K. variicola rather than K. pneumoniae contributed to the patient’s poor prognosis.

CONCLUSION

This is the first case report to show patient death from Klebsiella subspecies infection within a short period of time. This case provides a timely reminder of the clinical hazards posed by Klebsiella subspecies and highlights the limitations of classical laboratory methods in guiding anti-infective therapies for complex cases. Moreover, this report serves as reference for physicians diagnosing similar diseases and provides a recommendation to employ early genetic detection to aid patient diagnosis and management.

Transcriptome response of a new serotype of avian type Klebsiella varicella strain to chicken sera

Klebsiella variicola is a newly discovered pathogen of zoonotic importance, commonly causing serious systemic infection via the bloodstream route. However, the mechanism by which K. variicola survives and grows in the bloodstream is poorly understood. In a previous study, a strain of Klebsiella causing chicken bloodstream infection was obtained, and whole genome sequencing showed that it was a new ST174 type K. variicola. Therefore, the present study aimed to determine the molecular mechanism underlying the survival and development of K. variicola in host serum. First, we compared the transcriptomes of K. variicola grown in Luria-Bertani broth and chicken serum. We sequenced six RNA libraries from the two groups, each library had three repeats. A total of 1046 differentially expressed genes were identified. Functional annotation analysis showed that the differentially expressed genes are mainly involved in adaptive metabolism, biosynthesis pathways (including biosynthesis of siderophore group nonribosomal peptides and lipopolysaccharide (LPS) biosynthesis), stress resistance, and several known virulence regulatory systems (including the ABC transporter system, the two-component signal transduction system and the quorum sensing system). These genes are expected to contribute to the adaptation and growth of K. variicola in host birds. This analysis provides a new insight into the pathogenesis of K. variicola.

Kaptive 2.0: updated capsule and lipopolysaccharide locus typing for the Klebsiella pneumoniae species complex

The outer polysaccharide capsule and lipopolysaccharide (LPS) antigens are key targets for novel control strategies targeting Klebsiella pneumoniae and related taxa from the K. pneumoniae species complex (KpSC), including vaccines, phage and monoclonal antibody therapies. Given the importance and growing interest in these highly diverse surface antigens, we had previously developed Kaptive, a tool for rapidly identifying and typing capsule (K) and outer LPS (O) loci from whole genome sequence data. Here, we report two significant updates, now freely available in Kaptive 2.0 (https://github.com/katholt/kaptive): (i) the addition of 16 novel K locus sequences to the K locus reference database following an extensive search of >17 000 KpSC genomes; and (ii) enhanced O locus typing to enable prediction of the clinically relevant O2 antigen (sub)types, for which the genetic determinants have been recently described. We applied Kaptive 2.0 to a curated dataset of >12 000 public KpSC genomes to explore for the first time, to the best of our knowledge, the distribution of predicted O (sub)types across species, sampling niches and clones, which highlighted key differences in the distributions that warrant further investigation. As the uptake of genomic surveillance approaches continues to expand globally, the application of Kaptive 2.0 will generate novel insights essential for the design of effective KpSC control strategies.

Genetic Characteristics and Microbiological Profile of Hypermucoviscous Multidrug-Resistant Klebsiella variicola Coproducing IMP-4 and NDM-1 Carbapenemases

We report here a hypermucoviscous, New Delhi metallo-β-lactamase 1 (NDM-1) and imipenemase 4 (IMP-4) carbapenemases-coproducing Klebsiella variicola isolate obtained from a pediatric patient. This strain was resistant to carbapenems and most other β-lactams. Although hypermucoviscous, this strain possessed attenuated virulence according to serum killing assay and Galleria mellonella infection model. Notably, two copies of blaNDM-1 were contained on two tandem ISCR1 elements and coexisted with blaIMP-4 in a novel hybrid multidrug resistance plasmid. This is the first description of the coexistence of blaNDM-1 and blaIMP-4 in a single plasmid of hypermucoviscous K. variicola. IMPORTANCE As an important member of the Klebsiella pneumoniae complex, Klebsiella variicola is poorly studied as an emerging human pathogen. We, for the first time, report a unique K. variicola isolated from a pediatric patient in China. This isolate exhibited hypermucoviscosity, a classic hypervirulence characteristic of K. pneumoniae, and contained multiple carbapenem-resistant genes, including blaIMP-1 and blaNDM-1. Interestingly, these antimicrobial resistance genes were located on a novel hybrid plasmid, and our results suggested that this plasmid might have been introduced from K. pneumoniae and undergone a series of integration and recombination evolutionary events. Overall, our study provides more insight into K. variicola and highlights its superior capability to acquire and maintain foreign resistance genes.

Comparative Genomics of Borderline Oxacillin-Resistant Staphylococcus aureus Detected during a Pseudo-outbreak of Methicillin-Resistant S. aureus in a Neonatal Intensive Care Unit

Active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) is a component of our neonatal intensive care unit (NICU) infection prevention efforts. Recent atypical trends prompted review of 42 suspected MRSA isolates. Species identification was confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and methicillin resistance was reevaluated by PBP2a lateral flow assay, cefoxitin/oxacillin susceptibility testing, mecA and mecC PCR, and six commercially available MRSA detection agars. All isolates were confirmed S. aureus, but only eight were MRSA (cefoxitin resistant, PBP2a positive, mecA positive, growth on all MRSA screening agars). One MRSA isolate was cefoxitin susceptible but PBP2a and mecA positive, and the remaining 33 were cefoxitin susceptible, PBP2a negative, and mecA negative; interestingly, these isolates grew inconsistently across MRSA screening agars and had susceptibility profiles consistent with that of borderline oxacillin-resistant S. aureus (BORSA). Comparative genomic analyses found these BORSA isolates to be phylogenetically diverse and not representative of clonal expansion or shared gene content, though clones of two NICU strains were infrequently observed over 8 months. We identified 6 features-substitutions and truncations in PBP2, PBP4, and GdpP and beta-lactamase hyperproduction-that were used to generate a random forest classifier to distinguish BORSA from methicillin-susceptible S. aureus (MSSA) in our cohort. Our model demonstrated a robust ability to predict the BORSA phenotype among isolates collected across two continents (validation area under the curve [AUC], 0.902). Taking these findings together, we observed an unexpected prevalence of BORSA in our NICU, BORSA misclassification by existing MRSA screening methods, and markers that are together discriminatory for BORSA and MSSA within our cohort. This work has implications for epidemiological reporting of MRSA rates for centers using different screening methods. IMPORTANCE In this study, we found a high prevalence of Staphylococcus aureus isolates exhibiting a borderline oxacillin resistance phenotype (BORSA) in our neonatal intensive care unit (NICU) serendipitously due to the type of MRSA screening agar used by our laboratory for active surveillance cultures. Subsequent phenotypic and molecular characterization highlighted an unexpected prevalence and variability of BORSA isolates. Through whole-genome sequencing, we interrogated core and accessory genome content and generated a random forest classification model to identify mutations and truncations in the PBP2, PBP4, and GdpP proteins and beta-lactamase hyperproduction, which correlated with BORSA and MSSA phenotypes among S. aureus clinical isolates collected across two continents. In consideration of these findings, this work will help clinical microbiology laboratories and clinicians identify MRSA screening shortfalls and draw attention to the non-mecA-mediated BORSA phenotype.

PCR system for the correct differentiation of the main bacterial species of the Klebsiella pneumoniae complex

Accurate recognition of the closely related species Klebsiella pneumoniae, Klebsiella quasipneumoniae and Klebsiella variicola by phenotypic, biochemical and automated tests is notoriously unreliable in hospitals' diagnostic laboratories. A comparative genomics approach was conducted for the correct differentiation of the main bacterial species in the K. pneumoniae complex. Analysis of the deduced proteomes of 87 unique genomes of the Klebsiella in public databases, was used for the identification of unique protein family members. This allowed the design of a multiplex-PCR assay for the correct differentiation of these three species from different origins. This system allowed us to determine the prevalence of K. pneumoniae, K. quasipneumoniae and K. variicola among a collection of 552 clinical isolates. Of these, 87.3% (482/552) isolates corresponded to K. pneumoniae, 6.7% (33/552) to K. quasipneumoniae and 5.9% (33/552) to K. variicola. The multiplex-PCR results showed a 100% accuracy for the correct identification of the three species evaluated, which was validated with rpoB phylogenetic sequence analysis.

Characterization of Carbapenem-Resistant Enterobacteriaceae Cultured From Retail Meat Products, Patients, and Porcine Excrement in China

The emergence and dissemination of carbapenem-resistant Enterobacteriaceae (CRE) is a growing concern to animal and public health. However, little is known about the spread of CRE in food and livestock and its potential transmission to humans. To identify CRE strains from different origins and sources, 53 isolates were cultured from 760 samples including retail meat products, patients, and porcine excrement. Antimicrobial susceptibility testing was carried out, followed by phylogenetic typing, whole-genome sequencing, broth mating assays, and plasmids analyses. Forty-three Escherichia coli, nine Klebsiella pneumoniae, and one Enterobacter cloacae isolates were identified, each exhibiting multidrug-resistant phenotypes. Genetically, the main sequence types (STs) of E. coli were ST156 (n = 7), ST354 (n = 7), and ST48 (n = 7), and the dominant ST of K. pneumoniae is ST11 (n = 5). bla_NDM–5 (n = 40) of E. coli and bla_KPC–2 (n = 5) were the key genes that conferred carbapenem resistance phenotypes in these CRE strains. Additionally, the mcr-1 gene was identified in 17 bla_NDM-producing isolates. The bla_NDM–5 gene from eight strains could be transferred to the recipients via conjugation assays. Two mcr-1 genes in the E. coli isolates could be co-transferred along with the bla_NDM–5 genes. IncF and IncX3 plasmids have been found to be predominantly associated with bla_NDM gene in these strains. Strains isolated in our study from different sources and regions tend to be concordant and overlap. CRE strains from retail meat products are a reservoir for transition of CRE strains between animals and humans. These data also provide evidence of the dissemination of CRE strains and carbapenem-resistant genes between animal and human sources.

Enabling Biological Nitrogen Fixation for Cereal Crops in Fertilized Fields

Agricultural productivity relies on synthetic nitrogen fertilizers, yet half of that reactive nitrogen is lost to the environment. There is an urgent need for alternative nitrogen solutions to reduce the water pollution, ozone depletion, atmospheric particulate formation, and global greenhouse gas emissions associated with synthetic nitrogen fertilizer use. One such solution is biological nitrogen fixation (BNF), a component of the complex natural nitrogen cycle. BNF application to commercial agriculture is currently limited by fertilizer use and plant type. This paper describes the identification, development, and deployment of the first microbial product optimized using synthetic biology tools to enable BNF for corn (Zea mays) in fertilized fields, demonstrating the successful, safe commercialization of root-associated diazotrophs and realizing the potential of BNF to replace and reduce synthetic nitrogen fertilizer use in production agriculture. Derived from a wild nitrogen-fixing microbe isolated from agricultural soils, Klebsiella variicola 137-1036 ("Kv137-1036") retains the capacity of the parent strain to colonize corn roots while increasing nitrogen fixation activity 122-fold in nitrogen-rich environments. This technical milestone was then commercialized in less than half of the time of a traditional biological product, with robust biosafety evaluations and product formulations contributing to consumer confidence and ease of use. Tested in multi-year, multi-site field trial experiments throughout the U.S. Corn Belt, fields grown with Kv137-1036 exhibited both higher yields (0.35 ± 0.092 t/ha ± SE or 5.2 ± 1.4 bushels/acre ± SE) and reduced within-field yield variance by 25% in 2018 and 8% in 2019 compared to fields fertilized with synthetic nitrogen fertilizers alone. These results demonstrate the capacity of a broad-acre BNF product to fix nitrogen for corn in field conditions with reliable agronomic benefits.

Staphylococcus aureus injection drug use-associated bloodstream infections are propagated by community outbreaks of diverse lineages

Background

The ongoing injection drug use (IDU) crisis in the United States has been complicated by an emerging epidemic of Staphylococcus aureus IDU-associated bloodstream infections (IDU-BSI).

Methods

We performed a case-control study comparing S. aureus IDU-BSI and non-IDU BSI cases identified in a large US Midwestern academic medical center between Jan 1, 2016 and Dec 21, 2019. We obtained the whole-genome sequences of 154 S. aureus IDU-BSI and 91 S. aureus non-IDU BSI cases, which were matched with clinical data. We performed phylogenetic and comparative genomic analyses to investigate clonal expansion of lineages and molecular features characteristic of IDU-BSI isolates.

Results

Here we show that patients with IDU-BSI experience longer durations of bacteremia and have lower medical therapy completion rates. In phylogenetic analyses, 45/154 and 1/91 contemporaneous IDU-BSI and non-IDU BSI staphylococcal isolates, respectively, group into multiple, unique clonal clusters, revealing that pathogen community transmission distinctively spurs IDU-BSI. Lastly, multiple S. aureus lineages deficient in canonical virulence genes are overrepresented among IDU-BSI, which may contribute to the distinguishable clinical presentation of IDU-BSI cases.

Conclusions

We identify clonal expansion of multiple S. aureus lineages among IDU-BSI isolates, but not non-IDU BSI isolates, in a community with limited access to needle exchange facilities. In the setting of expanding numbers of staphylococcal IDU-BSI cases consideration should be given to treating IDU-associated invasive staphylococcal infections as a communicable disease.

Co-occurrence of Klebsiella variicola and Klebsiella pneumoniae Both Carrying bla KPC from a Respiratory Intensive Care Unit Patient

Objective

The aim of this study was to use whole-genome sequencing to characterize Klebsiella pneumoniae SKp2F and Klebsiella variicola SKv2E, both carrying bla_KPC, co-isolated from the same sputum specimen.

Methods

Antimicrobial susceptibility testing was performed using microbroth dilution. Biofilm formation was determined by crystal violet staining and virulence was measured by a serum killing assay. Whole-genome sequencing of SKp2F and SKv2E was performed using an Illumina sequencer and the genetic characteristics were analyzed by computer.

Results

SKp2F and SKv2E were sensitive only to tigecycline and polymyxin among the tested antibiotics. The biofilm-forming ability of SKv2E is stronger than that of SKp2F. The grades of serum resistance of SKp2F and SKv2E are 4 and 3. MLST analysis of the 6,115,610 bp and 5,403,687 bp of SKv2E and SKp2F showed associations with ST1615 and ST631, respectively. SKv2E carried 13 resistance genes (bla_KPC-2, bla_TEM-1A, bla_LEN17, aadA16, arr-3, qnrB4, oqxA/B, dfrA27, sul1, tetD, fosA, qacEΔ1) and SKp2F carried 23 (bla_KPC-2, bla_CTX-M-3, bla_TEM-1B, bla_CTX-M-65, bla_SHV-27, aac(6ʹ)-IIa, rmtB, arr-3, aph(3ʹ)-Ia, aadA16, qnrS1, aac(6ʹ)-Ib-cr, qnrB91, oqxA/B, mph(A), tet(A), fosA, dfrA27, and two copies of qacEΔ1-sul1). Most of them were carried by various mobile genetic elements, such as IncFIB(K)/IncFII(K)/IncFII(Yp), IncFII(K) plasmid, Tn6338, and In469. Both SKv2E and SKp2F carried a large number of virulence factors, including type 1 and 3 fimbriae, capsule, aerobactin (iutA), ent siderophore (entABCDEFS, fepABCDGfes), and salmochelin (iroE/iroEN). SKv2E also carried type IV pili (pilW), fimbrial adherence (steB, stfD), and capsule biosynthesis gene (glf).

Conclusion

bla_KPC-2-carrying K. variicola and K. pneumoniae, which carried multiple resistance genes, virulence factors, and highly similar mobile genetic elements, were identified from the same specimen, indicating that clinical samples may carry multiple bacteria. We should avoid misidentification, and bear in mind that resistance genes carrying mobile genetic elements can be transmitted or integrated between bacteria in the same host.

Exploring the environmental traits and applications of Klebsiella variicola

Klebsiella variicola has been found in various natural niches, alone or in association with other bacteria, and causes diseases in animals and plants with important economic and environmental impacts. K. variicola has the capacity to fix nitrogen in the rhizosphere and soil; produces indole acetic acid, acetoin, and ammonia; and dissolves phosphorus and potassium, which play an important role in plant growth promotion and nutrition. Some members of K. variicola have properties such as halotolerance and alkalotolerance, conferring an evolutionary advantage. In the environmental protection, K. variicola can be used in the wastewater treatment, biodegradation, and bioremediation of polluted soil, either alone or in association with other organisms. In addition, it has the potential to carry out industrial processes in the food and pharmaceutical industries, like the production of maltose and glucose by the catalysis of debranching unmodified oligosaccharides by the pullulanase enzyme. Finally, this bacterium has the ability to transform chemical energy into electrical energy, such as a biocatalyst, which could be useful in the near future. These properties show that K. variicola should be considered an eco-friendly bacterium with hopeful technological promise. In this review, we explore the most significant aspects of K. variicola and highlight its potential applications in environmental and biotechnological processes.

A genomic surveillance framework and genotyping tool for Klebsiella pneumoniae and its related species complex

Klebsiella pneumoniae is a leading cause of antimicrobial-resistant (AMR) healthcare-associated infections, neonatal sepsis and community-acquired liver abscess, and is associated with chronic intestinal diseases. Its diversity and complex population structure pose challenges for analysis and interpretation of K. pneumoniae genome data. Here we introduce Kleborate, a tool for analysing genomes of K. pneumoniae and its associated species complex, which consolidates interrogation of key features of proven clinical importance. Kleborate provides a framework to support genomic surveillance and epidemiology in research, clinical and public health settings. To demonstrate its utility we apply Kleborate to analyse publicly available Klebsiella genomes, including clinical isolates from a pan-European study of carbapenemase-producing Klebsiella, highlighting global trends in AMR and virulence as examples of what could be achieved by applying this genomic framework within more systematic genomic surveillance efforts. We also demonstrate the application of Kleborate to detect and type K. pneumoniae from gut metagenomes.

Klebsiella variicola Reference Strain F2R9 (ATCC BAA-830) Genome Sequence

Klebsiella variicola F2R9 was isolated from banana root, and its sequence has been deposited as ATCC BAA-830. It corresponds to sequence type 11 (ST11) and KL16 and contains no identifiable plasmids. The genome showed few antimicrobial resistance and virulence genes and several plant association genes. The strain showed susceptibility to most antimicrobials and avirulent behavior.

Multidrug-Resistant (MDR) Klebsiella variicola Strains Isolated in a Brazilian Hospital Belong to New Clones

Klebsiella variicola is mainly associated with opportunistic infections and frequently identified as Klebsiella pneumoniae. This misidentification implies a wrong epidemiology result as well as incorrect attribution to K. pneumoniae as the etiology of some severe infections. Recently, huge efforts have been made to study K. variicola, however, the biological aspects of this species are still unclear. Here we characterized five K. variicola strains initially identified as K. pneumoniae, with a Vitek-2 System and 16S rRNA sequencing. One-step multiplex polymerase chain reaction and Whole Genome Sequencing (WGS) identified them as K. variicola. Additionally, WGS analysis showed that all the strains are closely related with K. variicola genomes, forming a clustered group, apart from K. pneumoniae and K. quasipneumoniae. Multilocus sequence typing analysis showed four different sequence types (STs) among the strains and for two of them (Kv97 and Kv104) the same ST was assigned. All strains were multidrug-resistant (MDR) and three showed virulence phenotypes including invasion capacity to epithelial cells, and survival in human blood and serum. These results showed the emergence of new K. variicola clones with pathogenic potential to colonize and cause infection in different tissues. These characteristics associated with MDR strains raise great concern for human health.

Approaches for characterizing and tracking hospital-associated multidrug-resistant bacteria

Hospital-associated infections are a major concern for global public health. Infections with antibiotic-resistant pathogens can cause empiric treatment failure, and for infections with multidrug-resistant bacteria which can overcome antibiotics of "last resort" there exists no alternative treatments. Despite extensive sanitization protocols, the hospital environment is a potent reservoir and vector of antibiotic-resistant organisms. Pathogens can persist on hospital surfaces and plumbing for months to years, acquire new antibiotic resistance genes by horizontal gene transfer, and initiate outbreaks of hospital-associated infections by spreading to patients via healthcare workers and visitors. Advancements in next-generation sequencing of bacterial genomes and metagenomes have expanded our ability to (1) identify species and track distinct strains, (2) comprehensively profile antibiotic resistance genes, and (3) resolve the mobile elements that facilitate intra- and intercellular gene transfer. This information can, in turn, be used to characterize the population dynamics of hospital-associated microbiota, track outbreaks to their environmental reservoirs, and inform future interventions. This review provides a detailed overview of the approaches and bioinformatic tools available to study isolates and metagenomes of hospital-associated bacteria, and their multi-layered networks of transmission.

Comprehensive genomic analysis and characterization of a new ST 174 type Klebsiella variicola strain isolated from chicken embryos

Klebsiella variicola is a widespread opportunistic pathogen that causes infections in humans and animals. Herein a novel Klebsiella strain, AHKv-S01, was isolated and identified from dead chicken embryos in Anhui, China. Its genome contained a circular chromosome of 5,505,304 bp, with 5244 protein-coding genes, and an integrative conjugative element region containing 79 ORF sequences. AHKv-S01 was given a new sequence type number-174. Phylogenetic analyses showed that rpoB partial nucleotide sequences were highly reliable for identifying Klebsiella spp. Most of the 340 unique genes of AHKv-S01 were involved in cell envelop biogenesis, transcription, transport, and metabolic processes. Moreover, AHKv-S01 was sensitive to several antibiotics, but it showed strong resistance to penicillins, macrolides, and lincosamide. The genome contained three drug efflux pump superfamilies, β-lactamase genes, and fosfomycin resistance-related genes. Most drug resistance genes showed amino acid mutations. Multiple virulence and pathogenic factors were also identified, and they were mainly related to adhesion, secretion, iron acquisition, and immune evasion. Chicken embryo lethality assay results revealed that the 7-day chicken embryo lethality rate was 80%, 40%, and 50% for AHKv-S01, K. pneumoniae ATCC10031, and K. pneumoniae CICC24714, respectively. The median lethal dose of AHKv-S01 was 39.9 CFU/embryo. Even low infection levels of AHKv-S01 caused a significant reduction in chicken embryo hatchability. Severe pathological changes to the liver, heart, and brain tissues of embryos infected with AHKv-S01 were observed, and these changes appeared earlier in the heart and brain than in the liver. To conclude, our results provide a foundation for further studies aiming to assess the potential risk of K. variicola to poultry populations and production yields.

Genomic Epidemiology of Carbapenemase Producing Klebsiella pneumoniae Strains at a Northern Portuguese Hospital Enables the Detection of a Misidentified Klebsiella variicola KPC-3 Producing Strain

The evolutionary epidemiology, resistome, virulome and mobilome of thirty-one multidrug resistant Klebsiella pneumoniae clinical isolates from the northern Vila Real region of Portugal were characterized using whole-genome sequencing and bioinformatic analysis. The genomic population structure was dominated by two main sequence types (STs): ST147 (n = 17; 54.8%) and ST15 (n = 6; 19.4%) comprising four distinct genomic clusters. Two main carbapenemase coding genes were detected (blaKPC-3 and blaOXA-48) along with additional extended-spectrum β-lactamase coding loci (blaCTX-M-15, blaSHV-12, blaSHV-27, and blaSHV-187). Moreover, whole genome sequencing enabled the identification of one Klebsiella variicola KPC-3 producer isolate previously misidentified as K. pneumoniae, which in addition to the blaKPC-3 carbapenemase gene, bore the chromosomal broad spectrum β-lactamase blaLEN-2 coding gene, oqxAB and fosA resistance loci. The blaKPC-3 genes were located in a Tn4401b transposon (K. variicolan = 1; K. pneumoniaen = 2) and Tn4401d isoform (K. pneumoniaen = 28). Overall, our work describes the first report of a blaKPC-3 producing K. variicola, as well as the detection of this species during infection control measures in surveillance cultures from infected patients. It also highlights the importance of additional control measures to overcome the clonal dissemination of carbapenemase producing clones.

Antibiotic Sensitivity Screening of Klebsiella spp. and Raoultella spp. Isolated from Marine Bivalve Molluscs Reveal Presence of CTX-M-Producing K. pneumoniae

Klebsiella spp. are a major cause of both nosocomial and community acquired infections, with K. pneumoniae being responsible for most human infections. Although Klebsiella spp. are present in a variety of environments, their distribution in the sea and the associated antibiotic resistance is largely unknown. In order to examine prevalence of K. pneumoniae and related species in the marine environment, we sampled 476 batches of marine bivalve molluscs collected along the Norwegian coast. From these samples, K. pneumoniae (n = 78), K. oxytoca (n = 41), K. variicola (n = 33), K. aerogenes (n = 1), Raoultella ornithinolytica (n = 38) and R. planticola (n = 13) were isolated. The number of positive samples increased with higher levels of faecal contamination. We found low prevalence of acquired resistance in all isolates, with seven K. pneumoniae isolates showing resistance to more than one antibiotic class. The complete genome sequence of cefotaxime-resistant K. pneumoniae sensu stricto isolate 2016-1400 was obtained using Oxford Nanopore and Illumina MiSeq based sequencing. The 2016-1400 genome had two contigs, one chromosome of 5,088,943 bp and one plasmid of 191,744 bp and belonged to ST1035. The β-lactamase genes bla_CTX-M-3 and bla_TEM-1, as well as the heavy metal resistance genes pco, ars and sil were carried on a plasmid highly similar to one found in K. pneumoniae strain C17KP0055 from South-Korea recovered from a blood stream infection. The present study demonstrates that K. pneumoniae are prevalent in the coastal marine environment and that bivalve molluscs may act as a potential reservoir of extended spectrum β-lactamase (ESBL)-producing K. pneumoniae that may be transmitted through the food chain.

Diverse and abundant resistome in terrestrial and aquatic vertebrates revealed by transcriptional analysis

Despite increasing evidence that antibiotic resistant pathogens are shared among humans and animals, the diversity, abundance and patterns of spread of antibiotic resistance genes (ARGs) in wildlife remains unclear. We identified 194 ARGs associated with phenotypic resistance to 13 types of antibiotic in meta-transcriptomic data generated from a broad range of lower vertebrates residing in both terrestrial and aquatic habitats. These ARGs, confirmed by PCR, included those that shared high sequence similarity to clinical isolates of public health concern. Notably, the lower vertebrate resistome varied by ecological niche of the host sampled. The resistomes in marine fish shared high similarity and were characterized by very high abundance, distinct from that observed in other habitats. An assessment of ARG mobility found that ARGs in marine fish were frequently co-localized with mobile elements, indicating that they were likely spread by horizontal gene transfer. Together, these data reveal the remarkable diversity and transcriptional levels of ARGs in lower vertebrates, and suggest that these wildlife species might play an important role in the global spread of ARGs.

Investigation on the Genetic Signatures of Antibiotic Resistance in Multi-Drug-Resistant Klebsiella Pneumoniae Isolates From National Guard Hospital, Riyadh

Introduction Despite a large number of antibiotics available to treat Klebsiella (K.) pneumoniae (KP), resistance against these antibiotics is ever-increasing and has now become a global threat to human life. The most frequently observed resistant genes in Klebsiella pneumoniae are CTX-M, OXA-48, IMP, and NDM; some are clone-specific while others form a reservoir for infection. Methods Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) was employed for the identification of the pathogens and automated VITEK-2 (bioMérieux, Marcy-l'Étoile, France) was used for minimum inhibitory concentration (MIC) determination, followed by polymerase chain reaction (PCR) amplification of target genes and Sanger sequencing of amplicons. Results Forty-three out of 50 isolates (86%) were OXA gene-positive, and 49 out of 50 (98%) isolates were CTX-M gene positive. Two phenotypes of OXA were identified in 33 samples sequenced, OXA-505 (70%) and OXA-232 (30%). Sixteen isolates (32%) were positive for NDM-1. Twelve isolates were positive for both OXA and NDM. Multilocus sequence typing (MLST) on these isolates showed that they were distributed in 12 sequence types (STs). Thirty-six out of 50 were grouped in four clonal complexes. ST-14 was the predominant genotype. Conclusion This study has revealed that CTX-M-15 is the most common extended-spectrum beta-lactamase (ESBL) present in almost all isolates. The study also shows the presence of OXA as the main carbapenemase gene, alone or in combination with other carbapenemases such as NDM-1. Multilocus sequence typing revealed the incidence of polyclonal KP pool with ST-14, ST-29, ST-307, and ST-15 being the predominant ones.

Antibacterial Activity of Halophilic Bacteria Against Drug-Resistant Microbes Associated with Diabetic Foot Infections

Bacteria causing diabetic foot infections (DFI) are chronic and generally multidrug resistant (MDR), which calls urgently for alternative antibacterials. The present study focused on potential metabolite producing bacteria from a saltpan environment and screened against MDR pathogens isolated from DFI patients. Molecular identification of the DFI pathogens provided Klebsiella quasivariicola, Staphylococcus argenteus, Escherichia coli, Staphylococcus hominis subsp. novobiosepticus, Bacillus australimaris, and Corynebacterium stationis. Among 34 isolated halophilic bacteria, the cell-free supernatant of strain PSH06 provided the largest inhibition zone of 23 mm against K. quasivariicola [D1], 21 mm against. S. argenteus [D2], 19 mm against E. coli [D3], and a minimum inhibition zone was found to be 14 mm against C. stationis [D8]. The potent activity providing stain confirmed as Pseudomonas aeruginosa through molecular identification. On the other hand, ethyl acetate extract of this strain showed excellent growth inhibition in MIC at 64 µg/mL against K. quasivariicola. Distressed cell membranes and vast dead cells were observed at MIC of ethyl acetate extract by SEM and CLSM against K.quasivariicola and E. coli. GC-MS profile of ethyl acetate extract exposed the occurrence of Bis (2-Ethylhexyl) Phthalate and n-Hexadecanoic acid and shows 100% toxic effect at 24 mg/mL by Artemia nauplii. The active extract fraction with above compounds derived from saltpan bacteria provided highest antibacterial efficacy against DFI-associated pathogens depicted with broad spectrum activity compared to standard antibiotics.

Comparative genome analysis and characterization of a MDR Klebsiella variicola

Klebsiella variicola is an emerging pathogen responsible for causing blood-stream infections, urinary and respiratory tract related diseases in humans. In this report, we describe the genome sequence data and phenotypic characterization of K. variicola strain KV093 isolated from India. Comparative genome sequence analysis revealed the presence of genes linked with virulence, iron acquisition and transport, type 1 and type 3 pili, secretion systems including the capsular gene cluster. The plant-associated genes such as nitrogen fixation, growth and defense mechanisms against oxidative stress were also identified. On performing antibiotic susceptibility testing, growth inhibition, and stress challenge assays it was observed that the drug resistant K. variicola KV093 exhibited cross resistance to various antibiotics, antiseptics, including disinfectants. This report highlights the arsenal of virulence and antibiotic resistance determinants in K. variicola KV093, an effort emphasizing the current pressing need for regular surveillance of K. variicola strains especially in India.

Klebsiella variicola causing nosocomial transmission among neonates - an emerging pathogen?

Introduction. Transmission of Enterobacterales in neonatal intensive care units (NICU) can cause outbreaks of colonization and invasive infections among neonates. Two clusters of nosocomial transmission of Klebsiella pneumoniae identified by MALDI-ToF mass-spectrometry were suspected at two NICUs in July and August 2016.Aim. To assess the potential transmission of K. pneumoniae among neonates.Methodology. Whole-genome sequencing (WGS) was performed of K. pneumoniae isolates obtained through targeted surveillance of patients and environmental sampling.Results. WGS data revealed that patient and environmental isolates represented two species, K. pneumoniae and K. variicola. Core-genome multi-locus sequence typing (cgMLST) of the isolates identified three separate transmission clusters, in Hospital A a cluster of K. pneumoniae isolates in 12 children and two environmental samples and a second cluster of K. variicola isolates in five children. In Hospital B a cluster of K. pneumoniae isolates from three children and five unrelated isolates of K. pneumoniae and two unrelated isolates of K. variicola were found.Conclusion. K. variicola can cause hospital outbreaks of colonization and infection similar to other Klebsiella spp.Preliminary results from this study were presented at the 27th European Congress of Clinical Microbiology and Infectious Diseases, April 22-25, 2018, Vienna, Austria.

Population genomics of Klebsiella pneumoniae

Klebsiella pneumoniae is a common cause of antimicrobial-resistant opportunistic infections in hospitalized patients. The species is naturally resistant to penicillins, and members of the population often carry acquired resistance to multiple antimicrobials. However, knowledge of K. pneumoniae ecology, population structure or pathogenicity is relatively limited. Over the past decade, K. pneumoniae has emerged as a major clinical and public health threat owing to increasing prevalence of healthcare-associated infections caused by multidrug-resistant strains producing extended-spectrum β-lactamases and/or carbapenemases. A parallel phenomenon of severe community-acquired infections caused by 'hypervirulent' K. pneumoniae has also emerged, associated with strains expressing acquired virulence factors. These distinct clinical concerns have stimulated renewed interest in K. pneumoniae research and particularly the application of genomics. In this Review, we discuss how genomics approaches have advanced our understanding of K. pneumoniae taxonomy, ecology and evolution as well as the diversity and distribution of clinically relevant determinants of pathogenicity and antimicrobial resistance. A deeper understanding of K. pneumoniae population structure and diversity will be important for the proper design and interpretation of experimental studies, for interpreting clinical and public health surveillance data and for the design and implementation of novel control strategies against this important pathogen.

Evaluation of two rapid molecular test systems to establish an algorithm for fast identification of bacterial pathogens from positive blood cultures

Fast identification of pathogens directly from positive blood cultures is of highest importance to supply an adequate therapy of bloodstream infections (BSI). There are several platforms providing molecular-based identification, detection of antimicrobial resistance genes, or even a full antimicrobial susceptibility testing (AST). Two of such test systems allowing rapid diagnostics were assessed in this study: The Biofire FilmArray® and the Genmark ePlex®, both fully automated test system with a minimum of hands-on time. Overall 137 BSI episodes were included in our study and compared to conventional culture–based reference methods. The FilmArray® is using one catridge including a panel for the most common bacterial and fungal BSI pathogens as well as selected resistance markers. The ePlex® offers three different cartridges for detection of Gram-positives, Gram-negatives, and fungi resulting in a broader panel including also rare pathogens, putative contaminants, and more genetic resistance markers. The FilmArray® and ePlex® were evaluated for all 137 BSI episodes with FilmArray® detecting 119 and ePlex® detecting 128 of these. For targets on the respective panel of the system, the FilmArray® generated a sensitivity of 98.9% with 100% specificity on Gram-positive isolates. The ePlex® system generated a sensitivity of 94.7% and a specificity of 90.7% on Gram-positive isolates. In each case, the two systems performed with 100% sensitivity and specificity for the detection of Gram-negative specimens covered by each panel. In summary, both evaluated test systems showed a satisfying overall performance for fast pathogen identification and are beneficial tools for accelerating blood culture diagnostics of sepsis patients.

Genomic Characterization of Antibiotic Resistant Escherichia coli Isolated From Domestic Chickens in Pakistan

Poultry husbandry is important for the economic health of Pakistan, but the Pakistani poultry industry is negatively impacted by infections from Escherichia coli. We performed Illumina whole genome sequencing on 92 E. coli isolates obtained from the livers of deceased chickens originating in five Pakistani geographical regions. Our analysis indicates that the isolates are predominantly from the B1 and A clade and harbor a diverse number of antibiotic resistance and virulence genes, with no linkage between phylogeny and antibiotic resistance gene presence but some association between phylogeny and virulence gene and SNP presence for the B1 and E phylogroups. The colistin resistance gene mcr-1 and the quinolone resistance gene qnrS1 were both found in 13/92 isolates. Alarmingly, 82/92 of the E. coli strains characterized in this study are multidrug resistant with 100% (92/92) resistance to lincomycin, 81.5% (75/92) to streptomycin, 79.3% (73/92) to ampicillin and 66.3% (61/92) to ciprofloxacin. These results provide a high-resolution analysis of poultry-associated E. coli isolates in an area with a high endemic burden of antibiotic resistance. Surveillance of antibiotic resistance in poultry associated E. coli isolates is an important pillar of the One Health concept to integrate analysis of potential pathogens in human, animal, and environmental niches.

In vitro activity of meropenem/piperacillin/tazobactam triple combination therapy against clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus pseudintermedius and vancomycin-resistant Enterococcus spp

OBJECTIVES

To evaluate the activity of the reported synergistic and collaterally sensitive antibiotic combination, meropenem/piperacillin/tazobactam (ME/PI/TZ), against a panel of methicillin-resistant Staphylococcus aureus (MRSA) and other methicillin-resistant Staphylococcus species; and to investigate the relationship between ME/PI/TZ susceptibility and the genomic background of clinical isolates of MRSA.

METHODS

ME/PI/TZ combination and single drug minimum inhibitory concentrations (MICs) were determined for 207 strains (including 121 MRSA, 4 methicillin-sensitive S. aureus [MSSA], 37 vancomycin-intermediate S. aureus [VISA], 6 ceftaroline non-susceptible MRSA, 29 coagulase-negative staphylococci [CoNS], 5 S. pseudointermedius and 5 vancomycin-resistant Enterococci [VRE]) by broth microdilution. Whole genomes of 168 S. aureus strains were sequenced, assembled, and comparatively analysed.

RESULTS

USA300-SCCmec type IV isolates, clonal complex 8 (CC8)-MRSA isolates, including some VISA and ceftaroline (CPT)-intermediate strains, and all tested methicillin-resistant S. epidermidis isolates were highly susceptible to ME/PI/TZ. Isolates with elevated MICs (MICs of >16/16/16 mg/L) clustered with the USA100-SCCmec type II strain. Susceptibility of MRSA to ME/PI/TZ was correlated with susceptibility to ME. No obvious cross-resistance to CPT was observed among high-ME/PI/TZ MIC isolates.

CONCLUSIONS

The ME/PI/TZ combination is effective against a variety of clinical MRSA isolates, particularly of the USA300 lineage, which is expanding worldwide. ME/PI/TZ is also effective against drug-resistant CoNS and S. pseudintermedius clinical isolates.