scholarly journals The KbvR Regulator Contributes to Capsule Production, Outer Membrane Protein Biosynthesis, Antiphagocytosis, and Virulence in Klebsiella pneumoniae

2021 ◽  
Vol 89 (5) ◽  
Author(s):  
Li Xu ◽  
Meng Wang ◽  
Jie Yuan ◽  
Hui Wang ◽  
Moran Li ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Capsular Polysaccharide ◽  
Protein Biosynthesis ◽  
Outer Membrane Proteins ◽  
Systemic Infection ◽  
Innate Immune ◽  
Content Type

ABSTRACT Klebsiella pneumoniae is an opportunistic pathogen that mostly affects patients with weakened immune systems, but a few serotypes (especially K1 and K2) are highly invasive and result in systemic infection in healthy persons. The ability to evade and survive the components of the innate immune system is critical in infection. To investigate the role and mechanism of transcription regulator KP1_RS12260 (KbvR) in virulence and defense against the innate immune response, kbvR deletion mutant and complement strains were constructed. The in vivo animal infection assay and in vitro antiphagocytosis assay demonstrate K. pneumoniae KbvR is an important regulator that contributes to virulence and the defense against phagocytosis of macrophages. The transcriptome analysis and phenotype experiments demonstrated that deletion of kbvR decreased production of capsular polysaccharide (CPS) and biosynthesis of partly outer membrane proteins (OMPs). The findings suggest that KbvR is a global regulator that confers pathoadaptive phenotypes, which provide several implications for improving our understanding of the pathogenesis of K. pneumoniae.

scholarly journals OmpK26, a Novel Porin Associated with Carbapenem Resistance in Klebsiella pneumoniae

2011 ◽  
Vol 55 (10) ◽  
pp. 4742-4747 ◽  
Author(s):  
Laura García-Sureda ◽  
Antonio Doménech-Sánchez ◽  
Mariette Barbier ◽  
Carlos Juan ◽  
Joan Gascó ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane Proteins ◽  
Systemic Infection ◽  
Carbapenem Resistance ◽  
Resistant Isolate ◽  
Identical Result ◽  
Sequencing Analysis ◽  
Content Type ◽  
Carbapenem Resistant

ABSTRACTClinical isolates ofKlebsiella pneumoniaeresistant to carbapenems are being isolated with increasing frequency. Loss of the expression of the major nonspecific porins OmpK35/36 is a frequent feature in these isolates. In this study, we looked for porins that could compensate for the loss of the major porins in carbapenem-resistant organisms. Comparison of the outer membrane proteins from twoK. pneumoniaeclinical isogenic isolates that are susceptible (KpCS-1) and resistant (KpCR-1) to carbapenems revealed the absence of OmpK35/36 and the presence of a new 26-kDa protein in the resistant isolate. An identical result was obtained when another pair of isogenic isolates that are homoresistant (Kpn-3) and heteroresistant (Kpn-17) to carbapenems were compared. Mass spectrometry and DNA sequencing analysis demonstrated that this new protein, designated OmpK26, is a small monomeric oligogalacturonate-specific porin that belongs to the KdgM family of porins. Insertion-duplication mutagenesis of the OmpK26 coding gene,yjhA, in the carbapenem-resistant, porin-deficient isolate KpCR-1 caused the expression of OmpK36 and the reversion to the carbapenem-susceptible phenotype, suggesting that OmpK26 is indispensable for KpCR-1 to lose OmpK36 and become resistant to these antibiotics. Moreover, loss of the major porin and expression of OmpK26 reducedin vitrofitness and attenuated virulence in a murine model of acute systemic infection. Altogether, these results indicate that expression of the oligogalacturonate-specific porin OmpK26 compensates for the absence of OmpK35/36 and allows carbapenem resistance inK. pneumoniaebut cannot restore the fitness of the microorganism.

scholarly journals Serum Antibody Responses against Carbapenem-Resistant Klebsiella pneumoniae in Infected Patients

mSphere ◽  
2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Kasturi Banerjee ◽  
Michael P. Motley ◽  
Elizabeth Diago-Navarro ◽  
Bettina C. Fries
Keyword(s):  
Klebsiella Pneumoniae ◽  
Capsular Polysaccharide ◽  
Serum Antibody ◽  
Antibody Responses ◽  
Capsular Polysaccharides ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Reactive Properties

ABSTRACT Capsular polysaccharide (CPS) heterogeneity within carbapenem-resistant Klebsiella pneumoniae (CR-Kp) strain sequence type 258 (ST258) must be considered when developing CPS-based vaccines. Here, we sought to characterize CPS-specific antibody responses elicited by CR-Kp-infected patients. Plasma and bacterial isolates were collected from 33 hospital patients with positive CR-Kp cultures. Isolate capsules were typed by wzi sequencing. Reactivity and measures of efficacy of patient antibodies were studied against 3 prevalent CR-Kp CPS types (wzi29, wzi154, and wzi50). High IgG titers against wzi154 and wzi50 CPS were documented in 79% of infected patients. Patient-derived (PD) IgGs agglutinated CR-Kp and limited growth better than naive IgG and promoted phagocytosis of strains across the serotype isolated from their donors. Additionally, poly-IgG from wzi50 and wzi154 patients promoted phagocytosis of nonconcordant CR-Kp serotypes. Such effects were lost when poly-IgG was depleted of CPS-specific IgG. Additionally, mice infected with wzi50, wzi154, and wzi29 CR-Kp strains preopsonized with wzi50 patient-derived IgG exhibited lower lung CFU than controls. Depletion of wzi50 antibodies (Abs) reversed this effect in wzi50 and wzi154 infections, whereas wzi154 Ab depletion reduced poly-IgG efficacy against wzi29 CR-Kp. We are the first to report cross-reactive properties of CPS-specific Abs from CR-Kp patients through both in vitro and in vivo models. IMPORTANCE Carbapenem-resistant Klebsiella pneumoniae is a rapidly emerging public health threat that can cause fatal infections in up to 50% of affected patients. Due to its resistance to nearly all antimicrobials, development of alternate therapies like antibodies and vaccines is urgently needed. Capsular polysaccharides constitute important targets, as they are crucial for Klebsiella pneumoniae pathogenesis. Capsular polysaccharides are very diverse and, therefore, studying the host’s capsule-type specific antibodies is crucial to develop effective anti-CPS immunotherapies. In this study, we are the first to characterize humoral responses in infected patients against carbapenem-resistant Klebsiella pneumoniae expressing different wzi capsule types. This study is the first to report the efficacy of cross-reactive properties of CPS-specific Abs in both in vitro and in vivo models.

scholarly journals YraP Contributes to Cell Envelope Integrity and Virulence ofSalmonella entericaSerovar Typhimurium

2018 ◽  
Vol 86 (11) ◽  
Author(s):  
Faye C. Morris ◽  
Timothy J. Wells ◽  
Jack A. Bryant ◽  
Anna E. Schager ◽  
Yanina R. Sevastsyanovich ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Cell Envelope ◽  
Systemic Infection ◽  
Eukaryotic Cell ◽  
Infection Model ◽  
Content Type ◽  
Protein Levels ◽  
K 12

ABSTRACTMutations in σE-regulated lipoproteins have previously been shown to impact bacterial viability under conditions of stress and duringin vivoinfection. YraP is conserved across a number of Gram-negative pathogens, includingNeisseria meningitidis, where the homolog is a component of the Bexsero meningococcal group B vaccine. Investigations using laboratory-adaptedEscherichia coliK-12 have shown thatyraPmutants have elevated sensitivity to a range of compounds, including detergents and normally ineffective antibiotics. In this study, we investigate the role of the outer membrane lipoprotein YraP in the pathogenesis ofSalmonella entericaserovar Typhimurium. We show that mutations inS. TyphimuriumyraPresult in a defective outer membrane barrier with elevated sensitivity to a range of compounds. This defect is associated with attenuated virulence in an oral infection model and during the early stages of systemic infection. We show that this attenuation is not a result of defects in lipopolysaccharide and O-antigen synthesis, changes in outer membrane protein levels, or the ability to adhere to and invade eukaryotic cell linesin vitro.

scholarly journals Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and ReducesIn VivoPathogenicity

2012 ◽  
Vol 57 (1) ◽  
pp. 445-451 ◽  
Author(s):  
Ilka Tiemy Kato ◽  
Renato Araujo Prates ◽  
Caetano Padial Sabino ◽  
Beth Burgwyn Fuchs ◽  
George P. Tegos ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Virulence Factors ◽  
Sodium Dodecyl ◽  
Systemic Infection ◽  
Tube Formation ◽  
Photodynamic Inactivation ◽  
Content Type ◽  
Daughter Cells

ABSTRACTThe objective of this study was to evaluate whetherCandida albicansexhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells.C. albicanswas exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm2, 9 to 27 J/cm2).In vitro, we evaluated APDI effects onC. albicansgrowth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility.In vivo, we evaluatedC. albicanspathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability ofC. albicansto form germ tubes compared to untreated cells (P< 0.05). Survival of mice systemically infected withC. albicanspretreated with APDI was significantly increased compared to mice infected with untreated yeast (P< 0.05). APDI increasedC. albicanssensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole forC. albicanswas also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells ofC. albicanssubmitted to APDI. These data suggest that APDI may inhibit virulence factors and reducein vivopathogenicity ofC. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treatC. albicansinfections.

scholarly journals The Transcriptional Regulator CpsY Is Important for Innate Immune Evasion in Streptococcus pyogenes

2016 ◽  
Vol 85 (3) ◽  
Author(s):  
Luis A. Vega ◽  
Kayla M. Valdes ◽  
Ganesh S. Sundar ◽  
Ashton T. Belew ◽  
Emrul Islam ◽  
...  
Keyword(s):  
Streptococcus Pyogenes ◽  
Immune Evasion ◽  
Immune Cell ◽  
Group A Streptococcus ◽  
Transcriptional Regulator ◽  
Innate Immune ◽  
Content Type ◽  
Human Host

ABSTRACTAs an exclusively human pathogen,Streptococcus pyogenes(the group A streptococcus [GAS]) has specifically adapted to evade host innate immunity and survive in multiple tissue niches, including blood. GAS can overcome the metabolic constraints of the blood environment and expresses various immunomodulatory factors necessary for survival and immune cell resistance. Here we present our investigation of one such factor, the predicted LysR family transcriptional regulator CpsY. The encoding gene,cpsY, was initially identified as being required for GAS survival in a transposon-site hybridization (TraSH) screen in whole human blood. CpsY is homologous with transcriptional regulators ofStreptococcus mutans(MetR),Streptococcus iniae(CpsY), andStreptococcus agalactiae(MtaR) that regulate methionine transport, amino acid metabolism, resistance to neutrophil-mediated killing, and survivalin vivo. Our investigation indicated that CpsY is involved in GAS resistance to innate immune cells of its human host. However, GAS CpsY does not manifest thein vitrophenotypes of its homologs in other streptococcal species. GAS CpsY appears to regulate a small set of genes that is markedly different from the regulons of its homologs. The differential expression of these genes depends on the growth medium, and CpsY modestly influences their expression. The GAS CpsY regulon includes known virulence factors (mntE,speB,spd,nga[spn],prtS[SpyCEP], andsse) and cell surface-associated factors of GAS (emm1,mur1.2,sibA[cdhA], andM5005_Spy0500). Intriguingly, the loss of CpsY in GAS does not result in virulence defects in murine models of infection, suggesting that CpsY function in immune evasion is specific to the human host.

scholarly journals Doripenem MICs andompK36Porin Genotypes of Sequence Type 258, KPC-Producing Klebsiella pneumoniae May Predict Responses to Carbapenem-Colistin Combination Therapy among Patients with Bacteremia

2014 ◽  
Vol 59 (3) ◽  
pp. 1797-1801 ◽  
Author(s):  
Ryan K. Shields ◽  
M. Hong Nguyen ◽  
Brian A. Potoski ◽  
Ellen G. Press ◽  
Liang Chen ◽  
...  
Keyword(s):  
Amino Acids ◽  
Combination Therapy ◽  
Klebsiella Pneumoniae ◽  
Sequence Type ◽  
Content Type

ABSTRACTTreatment failures of a carbapenem-colistin regimen among patients with bacteremia due to sequence type 258 (ST258), KPC-2-producingKlebsiella pneumoniaewere significantly more likely if both agents were inactivein vitro, as defined by a colistin MIC of >2 μg/ml and the presence of either a majorompK36porin mutation (guanine and alanine insertions at amino acids 134 and 135 [ins aa 134–135 GD], IS5promoter insertion [P= 0.007]) or a doripenem MIC of >8 μg/ml (P= 0.01). MajorompK36mutations among KPC-K. pneumoniaestrains are important determinants of carbapenem-colistin responsesin vitroandin vivo.

scholarly journals Combined Stimulation of Toll-Like Receptor 5 and NOD1 Strongly Potentiates Activity of NF-κB, Resulting in Enhanced Innate Immune Reactions and Resistance to Salmonella enterica Serovar Typhimurium Infection

2013 ◽  
Vol 81 (10) ◽  
pp. 3855-3864 ◽  
Author(s):  
Amir I. Tukhvatulin ◽  
Ilya I. Gitlin ◽  
Dmitry V. Shcheblyakov ◽  
Natalia M. Artemicheva ◽  
Lyudmila G. Burdelya ◽  
...  
Keyword(s):  
Critical Role ◽  
Immune Defense ◽  
Innate Immune ◽  
Microbial Infection ◽  
Immune Reactions ◽  
Content Type ◽  
Essential Components ◽  
Stimulation Of

ABSTRACTPathogen recognition receptors (PRRs) are essential components of host innate immune systems that detect specific conserved pathogen-associated molecular patterns (PAMPs) presented by microorganisms. Members of two families of PRRs, transmembrane Toll-like receptors (TLRs 1, 2, 4, 5, and 6) and cytosolic NOD receptors (NOD1 and NOD2), are stimulated upon recognition of various bacterial PAMPs. Such stimulation leads to induction of a number of immune defense reactions, mainly triggered via activation of the transcription factor NF-κB. While coordination of responses initiated via different PRRs sensing multiple PAMPS present during an infection makes clear biological sense for the host, such interactions have not been fully characterized. Here, we demonstrate that combined stimulation of NOD1 and TLR5 (as well as other NOD and TLR family members) strongly potentiates activity of NF-κB and induces enhanced levels of innate immune reactions (e.g., cytokine production) bothin vitroandin vivo. Moreover, we show that an increased level of NF-κB activity plays a critical role in formation of downstream responses. In live mice, synergy between these receptors resulting in potentiation of NF-κB activity was organ specific, being most prominent in the gastrointestinal tract. Coordinated activity of NOD1 and TLR5 significantly increased protection of mice against enteroinvasiveSalmonellainfection. Obtained results suggest that cooperation of NOD and TLR receptors is important for effective responses to microbial infectionin vivo.

scholarly journals Ursodeoxycholic Acid (UDCA) Mitigates the Host Inflammatory Response during Clostridioides difficile Infection by Altering Gut Bile Acids

2020 ◽  
Vol 88 (6) ◽  
Author(s):  
Jenessa A. Winston ◽  
Alissa J. Rivera ◽  
Jingwei Cai ◽  
Rajani Thanissery ◽  
Stephanie A. Montgomery ◽  
...  
Keyword(s):  
Immune Response ◽  
Bile Acid ◽  
Inflammatory Response ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Colonization Resistance ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile infection (CDI) is associated with increasing morbidity and mortality posing an urgent threat to public health. Recurrence of CDI after successful treatment with antibiotics is high, thus necessitating discovery of novel therapeutics against this enteric pathogen. Administration of the secondary bile acid ursodeoxycholic acid (UDCA; ursodiol) inhibits the life cycles of various strains of C. difficile in vitro, suggesting that the FDA-approved formulation of UDCA, known as ursodiol, may be able to restore colonization resistance against C. difficile in vivo. However, the mechanism(s) by which ursodiol is able to restore colonization resistance against C. difficile remains unknown. Here, we confirmed that ursodiol inhibits C. difficile R20291 spore germination and outgrowth, growth, and toxin activity in a dose-dependent manner in vitro. In a murine model of CDI, exogenous administration of ursodiol resulted in significant alterations in the bile acid metabolome with little to no changes in gut microbial community structure. Ursodiol pretreatment resulted in attenuation of CDI pathogenesis early in the course of disease, which coincided with alterations in the cecal and colonic inflammatory transcriptome, bile acid-activated receptors nuclear farnesoid X receptor (FXR) and transmembrane G-protein-coupled membrane receptor 5 (TGR5), which are able to modulate the innate immune response through signaling pathways such as NF-κB. Although ursodiol pretreatment did not result in a consistent decrease in the C. difficile life cycle in vivo, it was able to attenuate an overly robust inflammatory response that is detrimental to the host during CDI. Ursodiol remains a viable nonantibiotic treatment and/or prevention strategy against CDI. Likewise, modulation of the host innate immune response via bile acid-activated receptors FXR and TGR5 represents a new potential treatment strategy for patients with CDI.

scholarly journals The Capsular Polysaccharide of Acinetobacter baumannii Is an Obstacle for Therapeutic Passive Immunization Strategies

2017 ◽  
Vol 85 (12) ◽  
Author(s):  
Shun Xin Wang-Lin ◽  
Ruth Olson ◽  
Janet M. Beanan ◽  
Ulrike MacDonald ◽  
Joseph P. Balthasar ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Bactericidal Activity ◽  
Capsular Polysaccharide ◽  
Rapid Development ◽  
Outer Membrane Proteins ◽  
Passive Immunization ◽  
Clinical Isolates ◽  
Content Type ◽  
Resistant Strains

ABSTRACT Acinetobacter baumannii has become an important concern for human health due to rapid development and wide spread of antimicrobial-resistant strains and high mortality associated with the infection. Passive immunizations with antisera targeting outer membrane proteins (OMPs) have shown encouraging results in protecting mice from A. baumannii infection, but monoclonal anti-OMP antibodies have not been developed, and their potential therapeutic properties have not been explored. The goal of this report is to evaluate the antibacterial activity of monoclonal antibodies (MAbs) targeting outer membrane protein A (OmpA) of A. baumannii. Five anti-OmpA MAbs were developed using hybridoma technology and showed strong binding to strain ATCC 19606. However, low antibody binding was observed when they were tested against six clinical isolates, which included extensively drug-resistant strains. In contrast, high binding to an isogenic K1 capsule-negative mutant (AB307.30) was shown, suggesting that capsular polysaccharide mediated the inhibition of MAb binding to OmpA. Anti-OmpA MAbs increased the macrophage-mediated bactericidal activity of AB307.30 but failed to increase phagocytic killing of capsule-positive strains. Capsular polysaccharide was also protective against complement-mediated bactericidal activity in human ascites in the presence and absence of opsonization. Lastly, passive immunization with anti-OmpA MAbs did not confer protection against challenge with AB307-0294, the encapsulated parent strain of AB307.30, in a mouse sepsis infection model. These results reveal the important role of capsule polysaccharide in shielding OmpA and thereby inhibiting anti-OmpA MAb binding to clinical isolates. This property of capsule hindered the therapeutic utility of anti-OmpA MAbs, and it may apply to other conserved epitopes in A. baumannii.

scholarly journals Localized adherence by enteropathogenic Escherichia coli is an inducible phenotype associated with the expression of new outer membrane proteins.

1991 ◽  
Vol 174 (5) ◽  
pp. 1167-1177 ◽  
Author(s):  
J Vuopio-Varkila ◽  
G K Schoolnik
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
De Novo ◽  
Outer Membrane Proteins ◽  
Temporal Correlation ◽  
Enteropathogenic Escherichia Coli ◽  
E Coli

Enteropathogenic Escherichia coli grow as discrete colonies on the mucous membranes of the small intestine. A similar pattern can be demonstrated in vitro; termed localized adherence (LA), it is characterized by the presence of circumscribed clusters of bacteria attached to the surfaces of cultured epithelial cells. The LA phenotype was studied using B171, an O111:NM enteropathogenic E. coli (EPEC) strain, and HEp-2 cell monolayers. LA could be detected 30-60 min after exposure of HEp-2 cells to B171. However, bacteria transferred from infected HEp-2 cells to fresh monolayers exhibited LA within 15 min, indicating that LA is an inducible phenotype. Induction of the LA phenotype was found to be associated with de novo protein synthesis and changes in the outer membrane proteins, including the production of a new 18.5-kD polypeptide. A partial NH2-terminal amino acid sequence of this polypeptide was obtained and showed it to be identical through residue 12 to the recently described bundle-forming pilus subunit of EPEC. Expression of the 18.5-kD polypeptide required the 57-megadalton enteropathogenic E. coli adherence plasmid previously shown to be required for the LA phenotype in vitro and full virulence in vivo. This observation, the correspondence of the 18.5-kD polypeptide to an EPEC-specific pilus protein, and the temporal correlation of its expression with the development of the LA phenotype suggest that it may contribute to the EPEC colonial mode of growth.

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