Complete Genome Sequence of a Community-Associated Methicillin-Resistant Staphylococcus aureus Hypervirulent Strain, USA300-C2406, Isolated from a Patient with a Lethal Case of Necrotizing Pneumonia.
ABSTRACT: USA300 is a predominant community-associated methicillin-resistant Staphylococcus aureus strain causing significant morbidity and mortality. We present here the full annotated genome of a USA300 hypervirulent clinical strain, USA300-C2406, isolated from a patient with a lethal case of necrotizing pneumonia, to gain a better understanding of USA300 hypervirulence.
Project description:Trauma-related necrotizing myocutaneous mucormycosis (NMM) has a high morbidity and mortality in victims of combat-related injuries, geometeorological disasters, and severe burns. Inspired by the observation that several recent clusters of NMM have been associated with extreme mechanical forces (e.g., during tornados), we studied the impact of mechanical stress on Mucoralean biology and virulence in a Drosophila melanogaster infection model. In contrast to other experimental procedures to exert mechanical stress, tornadic shear challenge (TSC) by magnetic stirring induced a hypervirulent phenotype in several clinically relevant Mucorales species but not in Aspergillus or Fusarium Whereas fungal growth rates, morphogenesis, and susceptibility to noxious environments or phagocytes were not altered by TSC, soluble factors released in the supernatant of shear-challenged R. arrhizus spores rendered static spores hypervirulent. Consistent with a rapid decay of TSC-induced hypervirulence, minimal transcriptional changes were revealed by comparative RNA sequencing analysis of static and shear-challenged Rhizopus arrhizus However, inhibition of the calcineurin/heat shock protein 90 (hsp90) stress response circuitry by cyclosporine and tanespimycin abrogated the increased pathogenicity of R. arrhizus spores following TSC. Similarly, calcineurin loss-of-function mutants of Mucor circinelloides displayed no increased virulence capacity in flies after undergoing TSC. Collectively, these results establish that TSC induces hypervirulence specifically in Mucorales and point out the calcineurin/hsp90 pathway as a key orchestrator of this phenotype. Our findings invite future studies of topical calcineurin inhibitor treatment of wounds as an adjunct mitigation strategy for NMM following high-energy trauma.IMPORTANCE Given the limited efficacy of current medical treatments in trauma-related necrotizing mucormycosis, there is a dire need to better understand the Mucoralean pathophysiology in order to develop novel strategies to counteract fungal tissue invasion following severe trauma. Here, we describe that tornadic shear stress challenge transiently induces a hypervirulent phenotype in various pathogenic Mucorales species but not in other molds known to cause wound infections. Pharmacological and genetic inhibition of calcineurin signaling abrogated hypervirulence in shear stress-challenged Mucorales, encouraging further evaluation of (topical) calcineurin inhibitors to improve therapeutic outcomes of NMM after combat-related blast injuries or violent storms.
Project description:Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is a threat to global public health. We characterized a sequence type 17 (ST17) K. pneumoniae clinical isolate that was resistant to carbapenems and belonged to serotype KL38/O2. Its complete genome is comprised of a 5.1-Mb chromosome and two conjugative plasmids. The 52,578-bp N-type plasmid pXH210-IMP contains the <i>bla</i><sub>IMP-4</sub> carbapenemase gene and the quinolone resistance gene <i>qnrS1</i>. The 272,742-bp FII(K)-9:FIB(K)-10 plasmid pXH210-AMV carries an array of genes that confer resistance to aminoglycosides, chloramphenicol, quinolones, tetracycline, sulfonamides, trimethoprim, arsenic, copper, and silver. However, the XH210 genome otherwise lacks the genes that are considered characteristic markers of hypervirulence in K. pneumoniae. The virulence potential of XH210 was assessed using a random forest algorithm predictive model, as well as Galleria mellonella and mouse infection models. The results of these were concordant and suggested that XH210 is hypervirulent and therefore a CR-hvKP strain. This worrying convergence of virulence and clinically significant antibiotic resistance is particularly concerning given the absence of typical hypervirulence markers. Further investigations are required to understand the virulence mechanisms of XH210 and to improve the diagnostics of hypervirulent K. pneumoniae. <b>IMPORTANCE</b> The combination of drug resistance and hypervirulence significantly limits the available treatment options for life-threatening infections caused by multidrug-resistant hvKP, especially CR-hvKP. To date, research on IMP-producing CR-hvKP is extremely scarce, and the virulence mechanisms of CR-hvKP are far more complicated and diverse than has been described in the literature so far. In this study, we characterized the tigecycline-resistant and IMP-4 carbapenemase-producing ST17 K. pneumoniae isolate XH210 from a human blood sample. Importantly, XH210 exhibits hypervirulence but does not possess traits that are frequently associated with the phenotype, highlighting the urgent need to improve identification of potentially hypervirulent isolates and enhance active surveillance of CR-hvKP strains to prevent their dissemination.
Project description:Klebsiella pneumoniae is one of the most clinically relevant species in immunocompromised individuals responsible for community-acquired and nosocomial infections, including pneumonias, urinary tract infections, bacteremias, and liver abscesses. Since the mid-1980s, hypervirulent K. pneumoniae, generally associated with the hypermucoviscosity phenotype, has emerged as a clinically significant pathogen responsible for serious disseminated infections, such as pyogenic liver abscesses, osteomyelitis, and endophthalmitis, in a generally younger and healthier population. Hypervirulent K. pneumoniae infections were primarily found in East Asia and now are increasingly being reported worldwide. Although most hypervirulent K. pneumoniae isolates are antibiotic-susceptible, some isolates with combined virulence and resistance, such as the carbapenem-resistant hypervirulent K. pneumoniae isolates, are increasingly being detected. The combination of multidrug resistance and enhanced virulence has the potential to cause the next clinical crisis. To better understand the basic biology of hypervirulent K. pneumoniae, this review will provide a summarization and discussion focused on epidemiology, hypervirulence-associated factors, and antibiotic resistance mechanisms of such hypervirulent strains. Epidemiological analysis of recent clinical isolates in China warns the global dissemination of hypervirulent K. pneumoniae strains with extensive antibiotic resistance in the near future. Therefore, an immediate response to recognize the global dissemination of this hypervirulent strain with resistance determinants is an urgent priority.
Project description:Predominant community-associated methicillin-resistant Staphylococcus aureus strain USA300 is believed to have originated from an ancestral methicillin-susceptible strain, although the details of that evolution remain unknown. To help understand the emergence of this highly successful strain, we sequenced the genomes of two methicillin-susceptible Staphylococcus aureus clinical strains that are very closely related to USA300.
Project description:INTRODUCTION:The USA300 clone of community-associated MRSA is reported to be hypervirulent and epidemic in the United States. This clone causes a variety of diseases from lethal pneumonia to mild skin infections. We hypothesized that evolutionary diversity may exist among USA300 clones, which may link virulence traits with host responses and mortality rates. METHODS:USA300 isolates from severe pneumonia (IP) and skin infection (IS) were characterized by pulsed-field gel electrophoresis (PFGE) and next-generation sequencing. Their virulence traits and host responses were compared in a lung infection model. RESULTS:The two USA300 isolates were found to be identical in genomic analysis. Robust IL-6 production, aggregation of bacteria, and hemorrhaging were observed in IP-infected lungs, which were associated with a higher rate of mortality than that observed with strain IS. Few neutrophils were detected in the lungs infected with strain IP, even at high bacterial loads. Massive production of ?-toxin and coagulase were evident during the early phase of IP infection, and robust gene expression of hla (?-toxin) and lukS-PV (Panton-Valentine leukocidin), but not coa, agrA, or rnaIII, was confirmed in vitro. Strain IP also induced strong hemolysis in red blood cells. CONCLUSIONS:The present data demonstrated latent diversity in the virulence of USA300 clones. Unknown regulatory mechanisms, probably involving a host factor(s) as a trigger, may govern the virulence expression and resultant high mortality in certain sub-clones of USA300.
Project description:The emergence of hypervirulent and carbapenem-resistant <i>Klebsiella pneumoniae</i> (hv-CRKP) has become a hot topic and confounding problem for clinicians and researchers alike. Conjugative virulence plasmids have the potential to cause more threatening dissemination of hv-CRKP strains. We previously identified K2606, a CG23 clinical hypervirulent strain of <i>Klebsiella pneumoniae</i> harboring a conjugative virulence plasmid designated pK2606. In this study we examined hypervirulence levels using assays of biofilm formation, serum resistance, and wax larvae and mouse <i>in vivo</i> infection models. Moreover, to define the transfer ability of pK2606 and whether this confers hypervirulence to other strains we performed plasmid transconjugation experiments between K2606 and the ST11 CRKP strain HS11286 along with <i>E. coli</i> J53. We found that although biofilm formation and serum resistance were not significantly increased, the transconjugants acquired the ability of produce high level of siderophores and also caused high mortality of wax larvae and mice. Furthermore, we identified pK2606-like conjugative virulence plasmids in GenBank, providing evidence that such plasmids may have begun to spread throughout China. These findings provide an evidence base for the possible mechanisms of the emergence of hv-CRKP strains and highlight the potential of pK2606-like conjugative virulence plasmids to spread worldwide.
Project description:Carbapenem-resistant and hypervirulent K. pneumoniae (CR-HvKP) strains that have emerged recently have caused infections of extremely high mortality in various countries. In this study, we discovered a conjugative plasmid that encodes carbapenem resistance and hypervirulence in a clinical ST86 K2 CR-HvKP, namely 17ZR-91. The conjugative plasmid (p17ZR-91-Vir-KPC) was formed by fusion of a non-conjugative pLVPK-like plasmid and a conjugative bla<sub>KPC-2</sub>-bearing plasmid and is present dynamically with two other non-fusion plasmids. Conjugation of p17ZR-91-Vir-KPC to other K. pneumoniae enabled them to rapidly express the carbapenem resistance and hypervirulence phenotypes. More importantly, genome analysis provided direct evidence that p17ZR-91-Vir-KPC could be directly transmitted from K2 CR-HvKP strain, 17ZR-91, to ST11 clinical K. pneumoniae strains to convert them into ST11 CR-HvKP strains, which explains the evolutionary mechanisms of recently emerged ST11 CR-HvKP strains.
Project description:USA300 is a predominant community-associated methicillin-resistant Staphylococcus aureus strain causing significant morbidity and mortality in North America. We present the full annotated genome sequences of two methicillin-resistant Staphylococcus aureus isolates related to the USA300 pulsotype with the goal of studying the evolutionary relationships of this highly successful strain type.
Project description:We report the identification of a carbapenem-resistant, hypervirulent Klebsiella pneumoniae (hvKp) strain which produced the carbapenemase VIM-1. Genomic analysis showed that the strain belonged to sequence type ST23 and serotype K1, a major hvKp clone, and harbored three resistance-encoding plasmids. Among them, a bla VIM-1-bearing plasmid was found to possess a mosaic structure presumably generated by multiple gene mobilization events. This finding indicates that hvKp actively acquires mobile resistance-encoding elements, facilitating simultaneous expression of hypervirulence and carbapenem-resistance.
Project description:Hypervirulent Klebsiella pneumoniae strains are usually susceptible to many antimicrobial agents including colistin. Here we report the isolation and characterization of several colistin-resistant hypervirulent K. pneumoniae clinical strains. K. pneumoniae strains recovered from blood samples were collected at a university hospital in China. MICs of colistin were determined using microdilution. Colistin-resistant strains were subjected to whole genome sequencing to reveal their clonal background, antimicrobial resistance determinants and virulence factors. Virulence assays were performed with strains carrying the mucoid phenotype regulator gene rmpA using wax moth larvae. The pmrB gene encoding a P344L substitution was cloned into a colistin-susceptible K. pneumoniae strain to examine whether the substitution confers colistin resistance. Five colistin-resistant hypervirulent K. pneumoniae were recovered from blood samples of patients in China, belonging to four sequence/capsular types (ST23:K1, ST412:K57, ST660:K16, and ST700:K1) and carried the virulence factor rmpA. Three strains had the known colistin-resistant D150G substitution in PhoQ including one ST700:K1 strain also carrying mcr-1. The remaining two isolates had a P344L substitution of PmrB but cloning of pmrB encoding the substitution into a colistin-susceptible isolate did not alter MICs of colistin, suggesting that such a substitution did not confer resistance to colistin. In conclusion, the convergence of colistin resistance and hypervirulence in K. pneumoniae of multiple clonal backgrounds has emerged and may warrant further surveillance.