Hypervirulent Strains Research Articles

Molecular genetic markers of resistance and virulence of invasive Klebsiella pneumoniae strains according to whole genome sequencing data

Objective. To evaluate genetic mechanisms of antibiotic resistance and virulence of invasive strains of Klebsiella pneumoniae isolated from inpatients using whole genome sequencing.Materials and methods. For two carbapenem-resistant multiple-antibiotic-resistant invasive strains of K.pneumoniae, as well as two carbapenem-sensitive invasive strains of K.pneumoniae, sequencing was performed using the MiSeq genomic sequencer (Illumina). Genomic sequences were assembled and annotated. Sequence type determination, search for plasmids and virulence factors, antibiotic resistance genes, and efflux mechanisms were performed.Results. K.pneumoniae strains belonged to sequence types ST395, ST101, ST111, and ST512 s and had a hypermucoid phenotype. The iutA aerobactin genes were detected in both sensitive and carbapenem-resistant strains. Virulence genes fimH, fyuA, and irp2 were detected in one strain isolated from blood. Carbapenemase genes (blaKPC, blaNDM) were detected in two strains. Aminoglycosides and fluoroquinolones resistance genes were detected in 3 of 4 strains. All strains showed the presence of different systems of active antibiotic elimination from the microbial cell.Conclusion. The possibility of identifying hypervirulent strains of K.pneumoniae using a complex phenotypic test along with hvKp genotyping is shown. The results of full-genome sequencing reflect significant resistance of hypervirulent K.pneumoniae strains isolated from blood to most antibiotics, including β-lactams, aminoglycosides, fluoroquinolones, phosphomycin, chloramphenicol and polymyxins.

Klebsiella pneumoniae survives on surfaces as a dry biofilm

BackgroundDry surface biofilms (DSB) are widespread in healthcare settings presenting a challenge to cleaning and disinfection. Klebsiella pneumoniae has been a focus of attention due to antibiotic resistance and the emergence of hypervirulent strains. Few studies have demonstrated K pneumoniae survival on surfaces following desiccation. MethodsDSB were formed over 12 days. Bacterial culturability and transfer were investigated following DSB incubation up to 4 weeks. Bacterial viability in DSB was investigated with live/dead staining using flow cytometry. ResultsK pneumoniae formed mature DSB. After 2 and 4 weeks of incubation, transfer from DSB was low (<55%) and reduced further (<21%) following wiping. Culturability at 2 and 4 weeks varied although viability remained high indicating viable but non culturable state (VBNC). DiscussionK pneumoniae was removed from surfaces by mechanical wiping as shown with DSB of other species. Although culturability was reduced over time, bacteria remained viable up to 4 weeks incubation, proving the need for robust cleaning regimens. ConclusionsThis is the first study confirming K pneumoniae survival on dry surfaces as a DSB. The presence of VBNC bacteria indicated that K pneumoniae can for extended periods, raising questions about its persistence on surfaces.

Phylogenetic Analysis and Virulence Characteristics of Methicillin-Resistant Staphylococcus aureus ST45 in China: a Hyper-Virulent Clone Associated with Bloodstream Infections.

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 45 (ST45) was rarely found in China. This study was conducted to trace the transmission and evolution of emerging MRSA ST45 strains in mainland China and explore its virulence. A total of 27 ST45 isolates were included for whole-genome sequencing and genetic characteristic analysis. Epidemiological results showed that MRSA ST45 isolates were often obtained from blood, primarily originated in Guangzhou, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type IV (SCCmec IV) dominated in MRSA ST45 (23/27, 85.2%). ST45-SCCmec V was located on a phylogenetic clade distinct from the SCCmec IV cluster. We selected two representative isolates, MR370 (ST45-SCCmec IV) and MR387 (ST45-SCCmec V), and performed hemolysin activity, a blood killing assay, a Galleria mellonella infection model, and a mouse bacteremia model, as well as real-time fluorescence quantitative PCR. MR370 was proved to have extreme virulence in the phenotypic assays and at the mRNA level compared with ST59, ST5, and USA300 MRSA strains. MR387 was comparable to USA300-LAC on the phenotype and was verified to have higher expression of scn, chp, sak, saeR, agrA, and RNAIII than USA300-LAC. The results emphasized the extraordinary performance of MR370 and the good potential of MR387 in virulence causing bloodstream infection. Meanwhile, we conclude that China MRSA ST45 showed two different clonotypes, which may be widespread in the future. The entire study is valuable as a timely reminder and reports virulence phenotypes of China MRSA ST45 for the first time. IMPORTANCE Methicillin-resistant Staphylococcus aureus ST45 is epidemic worldwide. This study contributed to the awareness of the Chinese hyper-virulent MRSA ST45 strains and served as a timely reminder of its wide dissemination of clonotypes. Further, we provide novel insights for prevention from the perspective of bloodstream infections. ST45-SCCmec V is a clonotype deserving special attention in China, and we performed genetic and phenotypic analyses for the first time on it.

The Environment, Farm Animals and Foods as Sources of Clostridioides difficile Infection in Humans.

The recent discovery of the same Clostridioides difficile ribotypes associated with human infection in a broad range of environments, animals and foods, coupled with an ever-increasing rate of community-acquired infections, suggests this pathogen may be foodborne. The objective of this review was to examine the evidence supporting this hypothesis. A review of the literature found that forty-three different ribotypes, including six hypervirulent strains, have been detected in meat and vegetable food products, all of which carry the genes encoding pathogenesis. Of these, nine ribotypes (002, 003, 012, 014, 027, 029, 070, 078 and 126) have been isolated from patients with confirmed community-associated C. difficile infection (CDI). A meta-analysis of this data suggested there is a higher risk of exposure to all ribotypes when consuming shellfish or pork, with the latter being the main foodborne route for ribotypes 027 and 078, the hypervirulent strains that cause most human illnesses. Managing the risk of foodborne CDI is difficult as there are multiple routes of transmission from the farming and processing environment to humans. Moreover, the endospores are resistant to most physical and chemical treatments. The most effective current strategy is, therefore, to limit the use of broad-spectrum antibiotics while advising potentially vulnerable patients to avoid high-risk foods such as shellfish and pork.

Activated Platelets Mediate Monocyte Killing of Klebsiella pneumoniae.

Platelets are known for essential activities in hemostasis and for their important contribution to protection against infectious pathogens. Klebsiella pneumoniae is an opportunistic pathogen widely known to cause nosocomial infections. Recently, hypervirulent strains of K. pneumoniae have been emerging, which can cause severe infections in immunocompetent individuals. Combined with the increase in antibiotic resistance, it is important to understand how K. pneumoniae affects components of the immune system. We studied the interactions of human platelets with several K. pneumoniae strains (the wild type encapsulated strain, and a nonencapsulated mutant). Thrombin-stimulated whole human and mouse blood significantly inhibited bacterial growth compared to unstimulated whole blood. Furthermore, we investigated the effect of K. pneumoniae on platelet activation. Both strains induced significant increase in activation of both unstimulated and thrombin-stimulated human platelets. Additionally, only the nonencapsulated mutant increased aggregation of platelets in response to ADP. K. pneumoniae killing assays were then performed with washed platelets in the presence or absence of thrombin. Surprisingly, washed platelets failed to exhibit any effects on the growth of K. pneumoniae. We further explored the impact of platelets on monocyte-mediated killing of K. pneumoniae. Importantly, we found that activated platelets significantly enhanced monocyte-mediated killing of K. pneumoniae. This effect was likely due to the formation of platelet-monocyte aggregates in blood upon thrombin stimulation. Overall, this study highlights the role of platelets in mediating a protective response against K. pneumoniae and reinforces the importance of platelets in modulating leukocyte behavior.

Presence of Polyketide Synthase (PKS) Gene and Counterpart Virulence Determinants in Klebsiella pneumoniae Strains Enhances Colorectal Cancer Progression In-Vitro.

Klebsiella pneumoniae (K. pneumoniae) colonizes the human gut and is a causative factor of pyogenic liver abscess (PLA). Retrospective studies conducted on K. pneumoniae PLA patients revealed subsequent CRC development in later years of their life with increasing prevalence of these strains harbouring polyketide synthase (PKS) genes. To our knowledge there are no known studies directly implicating K. pneumoniae with CRC to date. Our aims are to characterize K. pneumoniae isolates from CRC patients and investigate its effects on cell proliferation in vitro. K. pneumoniae isolates were characterized by screening virulence genes including polyketide synthase (PKS), biofilm assay, antibiotic susceptibility, and string test to determine hypervirulent (hvKp) strains. Solubilised antigens of selected K. pneumoniae isolates were co-cultured with primary colon cell lines and CRC cell lines (Stage I-IV) for 48 h. The enhancement of proliferation was measured through MTT and ECIS assay. Twenty-five percent of K. pneumoniae isolates were PKS-positive out of which 50% were hvKp strains. The majority of the isolates were from the more virulent serotype of K1 (30%) and K2 (50%). PKS-positive K. pneumoniae isolates did not possess genes to confer carbapenem resistance but instead were more highly associated with siderophore genes (aerobactin, enterobactin, and yersiniabactin) and allantoin metabolism genes (allS, allS2). Cell proliferation in primary colon, SW1116 (Stage I), and SW480 (Stage II) CRC cell lines were enhanced when co-cultured with PKS-positive K. pneumoniae antigens. ECIS revealed enhanced cell proliferation upon recurrent antigen exposure. This demonstrates the possible role that PKS-positive K. pneumoniae has in exacerbating CRC progression.

Phenotypic and Genomic Characterization of Nine String-Positive Carbapenem-Resistant Acinetobacter baumannii Isolates from Israel.

A positive "string test" indicates the ability of bacterial colonies grown on agar plates to form viscous strings of >5 mm when stretched. This phenotype is strongly associated with hypervirulence in Klebsiella pneumoniae but has never been described in carbapenem-resistant Acinetobacter baumannii (CRAB), an emerging human pathogen of high clinical significance. In this work, we screened 1,000 CRAB isolates, among which we identified and characterized 9 string-positive CRAB (stCRAB) isolates. Phenotypic and genotypic analyses revealed that the isolates were not phylogenetically related and possessed different antibiotic resistance and virulence profiles. Transmission electron microscopy (TEM) showed the presence of capsule in string-positive isolates. String-positive isolates were more motile but did not form more biofilm than non-string-positive isolates. They were less virulent in a murine thigh fitness model and a Galleria mellonella survival assay. In conclusion, here, we describe string-positive A. baumannii isolates and their phenotypic and molecular characteristics. We found that unlike K. pneumoniae, stCRAB isolates were not associated with increased virulence. IMPORTANCE Acinetobacter baumannii has been considered a major health care threat in recent years. Despite many efforts, the pathogenesis and molecular mechanism of A. baumannii virulence remain poorly understood. Moreover, the plasticity of its genome frequently gives rise to new and more virulent isolates. Our current study is of significant importance as it concerns a previously undescribed A. baumannii phenotype. The string-positive phenotype is strongly associated with increased fitness and virulence in other Gram-negative bacteria such as K. pneumoniae. Although no clear correlation with virulence or fitness was found in our 9 stCRAB isolates, this could have been due to the limited statistical power of our research. We suggest that this phenotype should be taken into consideration as due to its genome plasticity, the next change can give rise to string-positive and hypervirulent strains, as is known for K. pneumoniae. Additional future research is needed regarding its possible consequences.

Clostridioides difficile Binary Toxin Binding Component Increases Virulence in a Hamster Model.

Clostridioides difficile is the leading cause of hospital-acquired gastrointestinal infection, in part due to the existence of binary toxin (CDT)-expressing hypervirulent strains. Although the effects of the CDT holotoxin on disease pathogenesis have been previously studied, we sought to investigate the role of the individual components of CDT during in vivo infection. To determine the contribution of the separate components of CDT during infection, we developed strains of C difficile expressing either CDTa or CDTb individually. We then infected both mice and hamsters with these novel mutant strains and monitored them for development of severe illness. Although expression of CDTb without CDTa did not induce significant disease in a mouse model of C difficile infection, we found that complementation of a CDT-deficient C difficile strain with CDTb alone restored virulence in a hamster model of C difficile infection. Overall, this study demonstrates that the binding component of C difficile binary toxin, CDTb, contributes to virulence in a hamster model of infection.

Cytotoxic synergism of Clostridioides difficile toxin B with proinflammatory cytokines in subjects with inflammatory bowel diseases.

Clostridioides difficile (C. difficile) is progressively colonizing humans and animals living with humans. During this process, hypervirulent strains and mutated toxin A and B of C. difficile (TcdA and TcdB) are originating and developing. While in healthy subjects colonization by C. difficile becomes a risk after the use of antibiotics that alter the microbiome, other categories of people are more susceptible to infection and at risk of relapse, such as those with inflammatory bowel disease (IBD). Recent in vitro studies suggest that this increased susceptibility could be due to the strong cytotoxic synergism between TcdB and proinflammatory cytokines the tumor necrosis factor-alpha and interferon-gamma (CKs). Therefore, in subjects with IBD the presence of an inflammatory state in the colon could be the driver that increases the susceptibility to C. difficile infection and its progression and relapses. TcdB is internalized in the cell via three receptors: chondroitin sulphate proteoglycan 4; poliovirus receptor-like 3; and Wnt receptor frizzled family. Chondroitin sulphate proteoglycan 4 and Wnt receptor frizzled family are involved in cell death by apoptosis or necrosis depending on the concentration of TcdB and cell types, while poliovirus receptor-like 3 induces only necrosis. It is possible that cytokines could also induce a greater expression of receptors for TcdB that are more involved in necrosis than in apoptosis. Therefore, in subjects with IBD there are the conditions: (1) For greater susceptibility to C. difficile infection, such as the inflammatory state, and abnormalities of the microbiome and of the immune system; (2) for the enhancement of the cytotoxic activity of TcdB +Cks; and (3) for a greater expression of TcdB receptors stimulated by cytokines that induce cell death by necrosis rather than apoptosis. The only therapeutic approach currently possible in IBD patients is monitoring of C. difficile colonization for interventions aimed at reducing tumor necrosis factor-alpha and interferon-gamma levels when the infection begins. The future perspective is to generate bacteriophages against C. difficile for targeted therapy.

Keeping alert to the hypervirulent K1, K2, K3, K5, K54 and K57 strains of Klebsiella pneumoniae within dairy production process

Klebsiella pneumoniae (Kp) is now recognized as an urgent threat to public health since the emergence of multidrug-resistant and hypervirulent isolates. We identified a hypervirulent K2 isolate from the milk samples possibly associated with an infection incident in children, which raised the alarm to the zoonotic potential of bovine mastitis Kp as a foodborne pathogen. Subsequently, numerous K1, K2, K3, K5, K54 and K57 strains were identified from mastitis milk samples, and showed high pathogenicity in infected mouse. Further analysis based on complete genomes found that these isolates showed closely evolutionary relationships with the human hypervirulent strains in diverse phylogenetic lineages, suggesting their potential risk to public health.

Large-scale genomic analysis of global Klebsiella pneumoniae plasmids reveals multiple simultaneous clusters of carbapenem-resistant hypervirulent strains

BackgroundKlebsiella pneumoniae (Kp) Gram-negative bacteria cause nosocomial infections and rapidly acquire antimicrobial resistance (AMR), which makes it a global threat to human health. It also has a comparatively rare hypervirulent phenotype that can lead to severe disease in otherwise healthy individuals. Unlike classic Kp, canonical hypervirulent strains usually have limited AMR. However, after initial case reports in 2015, carbapenem-resistant hypervirulent Kp has increased in prevalence, including in China, but there is limited understanding of its burden in other geographical regions.MethodsHere, we examined the largest collection of publicly available sequenced Kp isolates (n=13,178), containing 1603 different sequence types (e.g. ST11 15.0%, ST258 9.5%), and 2174 (16.5%) hypervirulent strains. We analysed the plasmid replicons and carbapenemase and siderophore encoding genes to understand the movement of hypervirulence and AMR genes located on plasmids, and their convergence in carbapenem-resistant hypervirulent Kp.ResultsWe identified and analysed 3034 unique plasmid replicons to inform the epidemiology and transmission dynamics of carbapenem-resistant hypervirulent Kp (n=1028, 7.8%). We found several outbreaks globally, including one involving ST11 strains in China and another of ST231 in Asia centred on India, Thailand, and Pakistan. There was evidence of global flow of Kp, including across multiple continents. In most cases, clusters of Kp isolates are the result of hypervirulence genes entering classic strains, instead of carbapenem resistance genes entering canonical hypervirulent ones.ConclusionsOur analysis demonstrates the importance of plasmid analysis in the monitoring of carbapenem-resistant and hypervirulent strains of Kp. With the growing adoption of omics-based technologies for clinical and surveillance applications, including in geographical regions with gaps in data and knowledge (e.g. sub-Saharan Africa), the identification of the spread of AMR will inform infection control globally.

Clinical and Microbiological Characteristics of Endogenous Klebsiella pneumoniae Endophthalmitis in a Tertiary Hospital in Shanghai, China

ABSTRACT Purpose To investigate the clinical features of endogenous Klebsiella pneumoniae endophthalmitis (EKPE) and the molecular characteristics of pathogenic K. pneumoniae. Methods A retrospective study was conducted between January 2014 and January 2021. Clinical data were extracted. K. pneumoniae isolates cultured from EKPE patients’ specimens were characterized by antimicrobial susceptibility testing, multilocus sequence typing, capsular serotyping, and virulence gene profiles. Virulence phenotypes were confirmed by mouse lethality assay. Results Thirty-nine patients (47 eyes) were diagnosed with EKPE. Administration of systemic antibiotics and eye treatment within 24 hours of ocular symptom onset was statistically associated with better visual outcomes (p = .007). Sixteen K. pneumoniae isolates were collected, three of which were carbapenem-resistant and avirulent. Only salmochelin encoding gene was harbored by all isolates. Conclusions Systemic and eye treatment administered within 24 hours from the onset improves visual prognosis. Besides hypervirulent strains, avirulent carbapenem-resistant K. pneumoniae can cause EKPE.

Genotypic Diversity and Antifungal Susceptibility of Clinical Isolates of Cryptococcus Gattii Species Complex from Argentina.

The aim of this study was to determine the genotypic diversity of 22 Cryptococcus gattii species complex clinical isolates from Argentina and to place these genotypes within the diversity of clinical, veterinary and environmental isolates from Latin America. Mating type and antifungal susceptibility of the isolates were also determined. By URA5-RFLP, nine isolates were identified as molecular type VGI, 10 as VGII, one as VGIII and two as VGIV. Multilocus sequence typing (MSLT), following the International Society for Human and Animal Mycology (ISHAM) consensus MLST scheme, was used to determine the genotypic diversity. Our results suggest that, in Argentina, VGI isolates have low genetic diversity, while VGII isolates have high genetic diversity. Both isolates identified as VGIV by URA5-RFLP were genotyped by MLST as belonging to the currently named VGVI clade. From all isolates, eight sequence types (STs) were unique for Argentina, while five STs have been reported already in other countries, being of high interest the genotypes ST20 and ST7 since they belong to the subtypes VGIIa and VGIIb, respectively, which are associated with hypervirulent strains responsible for outbreaks in North America. To note, geographical analysis showed that some genotypes may be associated with some regions in Argentina. Most isolates were MATα, but we are reporting one isolate MATa for the first time in the country. Antifungal susceptibility tests showed that itraconazole, voriconazole and posaconazole had high activity against all isolates, while amphotericin B, fluconazole and 5-fluorocytosine were the least active drugs against all studied isolates.

Meningitis-associated pneumococcal serotype 8, ST 53, strain is hypervirulent in a rat model and has non-haemolytic pneumolysin which can be attenuated by liposomes.

Streptococcus pneumoniae bacteria cause life-threatening invasive pneumococcal disease (IPD), including meningitis. Pneumococci are classified into serotypes, determined by differences in capsular polysaccharide and both serotype and pneumolysin toxin are associated with disease severity. Strains of serotype 8, ST 53, are increasing in prevalence in IPD in several countries. Here we tested the virulence of such an isolate in a rat model of meningitis in comparison with a serotype 15B and a serotype 14 isolate. All three were isolated from meningitis patients in South Africa in 2019, where serotype 8 is currently the most common serotype in IPD. Only the serotype 8 isolate was hypervirulent causing brain injury and a high mortality rate. It induced a greater inflammatory cytokine response than either the serotype 15B or 14 strain in the rat model and from primary mixed-glia cells isolated from mouse brains. It had the thickest capsule of the three strains and produced non-haemolytic pneumolysin. Pneumolysin-sequestering liposomes reduced the neuroinflammatory cytokine response in vitro indicating that liposomes have the potential to be an effective adjuvant therapy even for hypervirulent pneumococcal strains with non-haemolytic pneumolysin.

Protective Efficacy and Immunogenicity of Rv0351/Rv3628 Subunit Vaccine Formulated in Different Adjuvants Against Mycobacterium tuberculosis Infection.

Bacillus Calmette-Guerin (BCG) vaccine is the only licensed vaccine for tuberculosis (TB) prevention. Previously, our group demonstrated the vaccine potential of Rv0351 and Rv3628 against Mycobacterium tuberculosis (Mtb) infection by directing Th1-biased CD4+ T cells co-expressing IFN-γ, TNF-α, and IL-2 in the lungs. Here, we assessed immunogenicity and vaccine potential of the combined Ags (Rv0351/Rv3628) formulated in different adjuvants as subunit booster in BCG-primed mice against hypervirulent clinical Mtb strain K (Mtb K). Compared to BCG-only or subunit-only vaccine, BCG prime and subunit boost regimen exhibited significantly enhanced Th1 response. Next, we evaluated the immunogenicity to the combined Ags when formulated with four different types of monophosphoryl lipid A (MPL)-based adjuvants: 1) dimethyldioctadecylammonium bromide (DDA), MPL, and trehalose dicorynomycolate (TDM) in liposome form (DMT), 2) MPL and Poly I:C in liposome form (MP), 3) MPL, Poly I:C, and QS21 in liposome form (MPQ), and 4) MPL and Poly I:C in squalene emulsion form (MPS). MPQ and MPS displayed greater adjuvancity in Th1 induction than DMT or MP did. Especially, BCG prime and subunit-MPS boost regimen significantly reduced the bacterial loads and pulmonary inflammation against Mtb K infection when compared to BCG-only vaccine at a chronic stage of TB disease. Collectively, our findings highlighted the importance of adjuvant components and formulation to induce the enhanced protection with an optimal Th1 response.

Evaluation of immunogenicity and efficacy of the enterobactin conjugate vaccine in protecting chickens from colibacillosis.

Colibacillosis is one of the most common and economically devastating infectious diseases in poultry production worldwide. Innovative universal vaccines are urgently needed to protect chickens from the infections caused by genetically diverse avian pathogenic Escherichia coli (APEC). Enterobactin (Ent) is a highly conserved siderophore required for E. coli iron acquisition and pathogenesis. The Ent-specific antibodies induced by a novel Ent conjugate vaccine significantly inhibited the in vitro growth of diverse APEC strains. In this study, White Leghorn chickens were immunized with the Ent conjugate vaccine using a crossed design with two variables, vaccination (with or without) and APEC challenge (O1, O78, or PBS control), resulting in six study groups (9 to 10 birds/group). The chickens were subcutaneously injected with the vaccine (100μg per bird) at 7days of age, followed by booster immunization at 21days of age. The chickens were intratracheally challenged with an APEC strain (108 CFU/bird) or PBS at 28days of age. At 5days post infection, all chickens were euthanized to examine lesions and APEC colonization of the major organs. Immunization of chickens with the Ent vaccine elicited a strong immune response with a 64-fold increase in the level of Ent-specific IgY in serum. The hypervirulent strain O78 caused extensive lesions in lung, air sac, heart, liver, and spleen with significantly reduced lesion scores observed in the vaccinated chickens. Interestingly, the vaccination did not significantly reduce APEC levels in the examined organs. The APEC O1 with low virulence only caused sporadic lesions in the organs in both vaccination and control groups. The Ent conjugate vaccine altered the bacterial community of the ileum and cecum. Taken together, the findings from this study showed the Ent conjugate vaccine could trigger a strong specific immune response and was promising to confer protection against APEC infection.

Effect of ZnO Nanoparticles as Antimicrobial on Multidrug Resistance Klebsiella Pneumonia: A Review

Klebsiella pneumoniae (K. pneumoniae)is a common microorganism for different infections, including respiratory, urinary tract, and biliary diseases, where immunocompromised individuals are directly affected by this bacterium. However, with the emergence of hypervirulent strains, individuals,whether healthy or immunocompetent, are equally susceptible to K. pneumoniae infections. This problem is diagnosed by the wide spreading of multidrug-resistant bacteria in the environment with multiple resistance mechanisms, which are the main challenges for an effective treatment. This put physicians in an inflexible confusion because of the limitation of medical treatment options. Among many remedy substances, zinc oxide (ZnO) nanoparticles (NPs) showed remarkable antibacterial properties versus many Gram-positive and Gram-negative bacteria. This work focuses on presenting the influence of these NPs on the expression of genes in charged in generating the K. pneumoniae capsule. Furthermore, perspectives for applying ZnO NPs in clinical practices are also discussed. As the in vivo studies show a powerful impact of ZnO on bacteria, it is anticipated that this method of treatment will be utilized by hospitals.

Multiple detection of hypermucoviscous and hypervirulent strains of Klebsiella pneumoniae: An emergent health care threat.

This study focused on the characterization of 19 hypermucoviscous Klebsiella pneumoniae strains, that were identified from 26 hypermucosal strains. In order to identify hypermucoviscous strains of K. pneumoniae, the string test was applied. This phenotype is known in the literature as one of the virulence factors of this species together with the production of biofilm and other hypervirulence factor genes such as: rmpA, rmpA2, iucA, iroB, peg-344. We also investigated presence of magA gene that correlates with the hyper-production of capsule of K1 serotype. Of the strains under study, 13 out of 19 harboured at least one virulence factor.Sequence type (ST) was determined in order to identify known high-risk clones or new emerging high-risk clones and their variability in a single clinical setting. Important STs found among these strains were ST65 and ST29. Carbapenem resistance was also investigated and 4 out of 19 strains harboured at least a carbapenemase: one strain harboured a KPC enzyme alone, one strain carried a KPC and an OXA-48 like, one strain produced OXA-48-like alone, and the last strain harboured two metallo-β-lactamases (VIM-1 and NDM-5) plus OXA-48-like. In particular, this latter strain belongs to ST383, which was recently reported in Northern Italy as a hypervirulent and XDR strain.The global spread of hypervirulent K. pneumoniae is an important epidemiological issue that should be considered in diagnostic and therapeutic managements of patients with K. pneumoniae infections.

Rapid-format recombinant antibody-based methods for the diagnosis of Clostridioides difficile infection: Recent advances and perspectives.

Clostridioides difficile, the most common cause of nosocomial diarrhea, has been continuously reported as a worldwide problem in healthcare settings. Additionally, the emergence of hypervirulent strains of C. difficile has always been a critical concern and led to continuous efforts to develop more accurate diagnostic methods for detection of this recalcitrant pathogen. Currently, the diagnosis of C. difficile infection (CDI) is based on clinical manifestations and laboratory tests for detecting the bacterium and/or its toxins, which exhibit varied sensitivity and specificity. In this regard, development of rapid diagnostic techniques based on antibodies has demonstrated promising results in both research and clinical environments. Recently, application of recombinant antibody (rAb) technologies like phage display has provided a faster and more cost-effective approach for antibody production. The application of rAbs for developing ultrasensitive diagnostic tools ranging from immunoassays to immunosensors, has allowed the researchers to introduce new platforms with high sensitivity and specificity. Additionally, DNA encoding antibodies are directly accessible in these approaches, which enables the application of antibody engineering to increase their sensitivity and specificity. Here, we review the latest studies about the antibody-based ultrasensitive diagnostic platforms for detection of C. difficile bacteria, with an emphasis on rAb technologies.

Pyogenic spondylitis caused by Klebsiella pneumoniae: should the possibility of hypervirulent Klebsiella pneumoniae be considered?

BackgroundKlebsiella pneumoniae is rare but the second most common causative agent among gram-negative bacteria that cause pyogenic spondylitis. However, there are no available studies on the serotype, virulence factors, and clinical characteristics associated with K. pneumoniae-caused pyogenic spondylitis. Accordingly, we investigated the clinical characteristics of pyogenic spondylitis, K1 and K2 serotypes, and virulence factors of K. pneumoniae.MethodsWe reviewed the microbiological reports of specimens collected between January 2014 and December 2019 as well as the medical records of patients with pyogenic spondylitis caused by K. pneumoniae. We also evaluated K1 and K2 serotypes and the virulent genes rmpA, iutA, mrkD, ybtS, entB, and kfu. Strains that possessed rmpA and iutA were defined as hypervirulent K. pneumoniae.ResultsSix patients with pyogenic spondylitis caused by K. pneumoniae were enrolled in the study. The capsular serotypes K1 and K2 were present in 66.7% (4/6) of cases, and the hypervirulent strains were present in 88.3% (5/6) of cases. All patients had community-acquired infections, and all strains isolated were susceptible to antimicrobial agents. Intravenous antibiotic treatment continued for 2–7 weeks, and no patient underwent decompressive operation or surgical debridement. There was no recurrence. One patient died from pneumonia with a septic lung.ConclusionHypervirulent K. pneumoniae is a rare but possible causative agent associated with pyogenic spondylitis.