The AdcACB/AdcAII system is Essential for Zinc Homeostasis and an Important Contributor of Enterococcus faecalis Virulence

Bacterial pathogens require a variety of micronutrients for growth, including trace metals such as iron, manganese, and zinc (Zn). Despite their relative abundance in host environments, access to these metals is severely restricted during infection due to host-mediated defense mechanisms collectively known as nutritional immunity. Despite a growing appreciation of the importance of Zn in host-pathogen interactions, the mechanisms of Zn homeostasis and the significance of Zn to the pathophysiology of E. faecalis, a major pathogen of nosocomial and community-associated infections, have not been investigated. Here, we show that E. faecalis encoded an ABC-type transporter AdcACB and an orphan substrate-binding lipoprotein AdcAII that work cooperatively to maintain Zn homeostasis. Simultaneous inactivation of adcA and adcAII or the entire adcACB operon led to significant reduction in intracellular Zn under Zn-restricted conditions, heightened sensitivity to Zn-chelating agents including human calprotectin, aberrant cell morphology, and impaired fitness in serum ex vivo. Additionally, inactivation of adcACB and adcAII significantly reduced bacterial tolerance towards cell envelope-targeting antibiotics, which may be associated to altered fatty acid abundance and species. Lastly, we show that the AdcACB/AdcAII system contributes to E. faecalis virulence in an invertebrate (Galleria mellonella) infection model and in two catheter-associated mouse infection models that recapitulate many of the host conditions associated with enterococcal human infections. Collectively, this report reveals that high-affinity Zn import is essential for the pathogenesis of E. faecalis indicating that the surface-associated AdcA and AdcAII lipoproteins are potential therapeutic targets.

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Serial Passage of Cryptococcus neoformans in Galleria mellonella Results in Increased Capsule and Intracellular Replication in Hemocytes, but Not Increased Resistance to Hydrogen Peroxide

Pathogens ◽

10.3390/pathogens9090732 ◽

2020 ◽

Vol 9 (9) ◽

pp. 732 ◽

Cited By ~ 1

Author(s):

Muhammad Fariz Ali ◽

Stephen M. Tansie ◽

John R. Shahan ◽

Rebecca L. Seipelt-Thiemann ◽

Erin E. McClelland

Keyword(s):

Hydrogen Peroxide ◽

Cryptococcus Neoformans ◽

Galleria Mellonella ◽

Ex Vivo ◽

Histopathological Examination ◽

Serial Passage ◽

Infection Model ◽

Hydrogen Peroxide Production ◽

Species Response

To gain insight into how pathogens adapt to new hosts, Cryptococcus neoformans (H99W) was serially passaged in Galleria mellonella. The phenotypic characteristics of the passaged strain (P15) and H99W were evaluated. P15 grew faster in hemolymph than H99W, in vitro and in vivo, suggesting that adaptation had occurred. However, P15 was more susceptible to hydrogen peroxide in vitro, killed fewer mouse macrophages, and had less fungal burden in human ex vivo macrophages than H99W. Analysis of gene expression changes during Galleria infection showed only a few different genes involved in the reactive oxygen species response. As P15 sheds more GXM than H99W, P15 may have adapted by downregulating hemocyte hydrogen peroxide production, possibly through increased capsular glucuronoxylomannan (GXM) shedding. Hemocytes infected with P15 produced less hydrogen peroxide, and hydrogen peroxide production in response to GXM-shedding mutants was correlated with shed GXM. Histopathological examination of infected larvae showed increased numbers and sizes of immune nodules for P15 compared to H99W, suggesting an enhanced, but functionally defective, response to P15. These results could explain why this infection model does not always correlate with murine models. Overall, C. neoformans’ serial passage in G. mellonella resulted in a better understanding of how this yeast evolves under selection.

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Identifying virulence determinants of multidrug-resistant Klebsiella pneumoniae in Galleria mellonella

10.1101/2020.10.30.362657 ◽

2020 ◽

Author(s):

Sebastian Bruchmann ◽

Theresa Feltwell ◽

Julian Parkhill ◽

Francesca L. Short

Keyword(s):

Klebsiella Pneumoniae ◽

Large Scale ◽

Galleria Mellonella ◽

Fitness Landscape ◽

Cell Envelope ◽

Dominant Role ◽

Multidrug Resistant ◽

Infection Model ◽

Virulence Determinants ◽

Genome Scale

AbstractInfections caused by Klebsiella pneumoniae are a major public health threat. Extensively drug-resistant and even pan-resistant strains have been reported. Understanding K. pneumoniae pathogenesis is hampered by the fact that murine models of infection offer limited resolution for the non-hypervirulent strains which cause the majority of infections. We have performed genome-scale fitness profiling of a multidrug-resistant K. pneumoniae ST258 strain during infection of the insect Galleria mellonella, with the aim to determine if this model is suitable for large-scale virulence factor discovery in this pathogen. Our results demonstrated a dominant role for surface polysaccharides in infection, with contributions from siderophores, cell envelope proteins, purine biosynthesis genes and additional genes of unknown function. Comparison with a hypervirulent strain, ATCC 43816, revealed substantial overlap in important infection-related genes, as well as additional putative virulence factors that may be specific to ST258. Our analysis also identified a role for the metalloregulatory protein NfeR (also called YqjI) in virulence. Overall, this study offers new insight into the infection fitness landscape of K. pneumoniae ST258, and provides a framework for using the highly flexible, scalable G. mellonella infection model to dissect the molecular virulence mechanisms of K. pneumoniae and other bacterial pathogens.

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GigC, a LysR Family Transcription Regulator, Is Required for Cysteine Metabolism and Virulence in Acinetobacter baumannii

Infection and Immunity ◽

10.1128/iai.00180-20 ◽

2020 ◽

Vol 89 (1) ◽

pp. e00180-20

Author(s):

Michael J. Gebhardt ◽

Daniel M. Czyz ◽

Shweta Singh ◽

Daniel V. Zurawski ◽

Lev Becker ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Galleria Mellonella ◽

Multidrug Resistant ◽

Resistant Isolate ◽

Infection Model ◽

Content Type ◽

Transcription Regulator ◽

Nutritional Immunity ◽

Metabolic Products ◽

Lysr Family

ABSTRACTA critical facet of mammalian innate immunity involves the hosts’ attempts to sequester and/or limit the availability of key metabolic products from pathogens. For example, nutritional immunity encompasses host approaches to limit the availability of key heavy metal ions such as zinc and iron. Previously, we identified several hundred genes in a multidrug-resistant isolate of Acinetobacter baumannii that are required for growth and/or survival in the Galleria mellonella infection model. In the present study, we further characterize one of these genes, a LysR family transcription regulator that we previously named GigC. We show that mutant strains lacking gigC have impaired growth in the absence of the amino acid cysteine and that gigC regulates the expression of several genes involved in the sulfur assimilation and cysteine biosynthetic pathways. We further show that cells harboring a deletion of the gigC gene are attenuated in two murine infection models, suggesting that the GigC protein, likely through its regulation of the cysteine biosynthetic pathway, plays a key role in the virulence of A. baumannii.

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Deletion of the SKO1 Gene in a hog1 Mutant Reverts Virulence in Candida albicans

Journal of Fungi ◽

10.3390/jof5040107 ◽

2019 ◽

Vol 5 (4) ◽

pp. 107

Author(s):

Verónica Urrialde ◽

Daniel Prieto ◽

Susana Hidalgo-Vico ◽

Elvira Román ◽

Jesús Pla ◽

...

Keyword(s):

Candida Albicans ◽

Intestinal Tract ◽

Galleria Mellonella ◽

Ex Vivo ◽

Mutant Cell ◽

Systemic Infection ◽

Infection Model ◽

Relevant Role

Candida albicans displays the ability to adapt to a wide variety of environmental conditions, triggering signaling pathways and transcriptional regulation. Sko1 is a transcription factor that was previously involved in early hypoxic response, cell wall remodeling, and stress response. In the present work, the role of sko1 mutant in in vivo and ex vivo studies was explored. The sko1 mutant behaved as its parental wild type strain regarding the ability to colonize murine intestinal tract, ex vivo adhesion to murine gut epithelium, or systemic virulence. These observations suggest that Sko1 is expendable during commensalism or pathogenesis. Nevertheless, the study of the hog1 sko1 double mutant showed unexpected phenotypes. Previous researches reported that the deletion of the HOG1 gene led to avirulent C. albicans mutant cell, which was, therefore, unable to establish as a commensal in a gastrointestinal murine model. Here, we show that the deletion of sko1 in a hog1 background reverted the virulence of the hog1 mutant in a systemic infection model in Galleria mellonella larvae and slightly improved the ability to colonize the murine gut in a commensalism animal model compared to the hog1 mutant. These results indicate that Sko1 acts as a repressor of virulence related genes, concluding that Sko1 plays a relevant role during commensalism and systemic infection.

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Manganese acquisition is essential for virulence ofEnterococcus faecalis

10.1101/323832 ◽

2018 ◽

Author(s):

C Colomer-Winter ◽

AL Flores-Mireles ◽

SP Baker ◽

KL Frank ◽

AJL Lynch ◽

...

Keyword(s):

Metal Binding ◽

Defense Mechanism ◽

Galleria Mellonella ◽

Ex Vivo ◽

Systemic Infection ◽

Significant Loss ◽

Antimicrobial Protein ◽

Nutritional Immunity ◽

Maximal Sensitivity

AbstractManganese (Mn) is an essential micronutrient that is not readily available to pathogens during infection due to an active host defense mechanism known as nutritional immunity. To overcome this nutrient restriction, bacteria utilize high-affinity transporters that allow them to compete with host metal-binding proteins. Despite the established role of Mn in bacterial pathogenesis, little is known about the relevance of Mn in the pathophysiology ofE. faecalis. Here, we identified and characterized the major Mn acquisition systems ofE. faecalis. We discovered that the ABC-type permease EfaCBA and two Nramp-type transporters, named MntH1 and MntH2, work collectively to promote cell growth under Mn-restricted conditions. The simultaneous inactivation of EfaCBA, MntH1 and MntH2 (ΔefaΔmntH1ΔmntH2strain) led to drastic reductions (>95%) in intracellular Mn content, severe growth defects in body fluids (serum and urine)ex vivo, significant loss of virulence inGalleria mellonella, and virtually complete loss of virulence in rabbit endocarditis and murine catheter-associated urinary tract infection (CAUTI) models. Despite the functional redundancy ofEfaCBA,MntH1andMntH2underin vitroorex vivoconditions and in the invertebrate model, dual inactivation ofefaCBAandmntH2(ΔefaΔmntH2strain) was sufficient to prompt maximal sensitivity to calprotectin, a Mn- and Zn-chelating host antimicrobial protein, and for the loss of virulence in mammalian models. Interestingly, EfaCBA appears to play a prominent role during systemic infection, whereas MntH2 was more important during CAUTI. The different roles of EfaCBA and MntH2 in these sites could be attributed, at least in part, to the differential expression ofefaAandmntH2in cells isolated from hearts or from bladders. Collectively, this study demonstrates that Mn acquisition is essential for the pathogenesis ofE. faecalisand validates Mn uptake systems as promising targets for the development of new antimicrobials.

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In Vitro, In Silico and Ex Vivo Studies of Dihydroartemisinin Derivatives as Antitubercular Agents

Current Topics in Medicinal Chemistry ◽

10.2174/1568026619666190305131425 ◽

2019 ◽

Vol 19 (8) ◽

pp. 633-644 ◽

Cited By ~ 1

Author(s):

Komal Kalani ◽

Sarfaraz Alam ◽

Vinita Chaturvedi ◽

Shyam Singh ◽

Feroz Khan ◽

...

Keyword(s):

Bone Marrow ◽

In Silico ◽

Ex Vivo ◽

Virulent Strain ◽

Infection Model ◽

Mouse Bone Marrow ◽

Significant Activity ◽

Macrophage Infection ◽

In Silico Studies

Introduction: As a part of our drug discovery program for anti-tubercular agents, dihydroartemisinin (DHA-1) was screened against Mtb H37Rv, which showed moderate anti-tubercular activity (>25.0 µg/mL). These results prompted us to carry out the chemical transformation of DHA-1 into various derivatives and study their antitubercular potential. Materials and Methods: DHA-1 was semi-synthetically converted into four new acyl derivatives (DHA-1A – DHA-1D) and in-vitro evaluated for their anti-tubercular potential against Mycobacterium tuberculosis H37Rv virulent strain. The derivatives, DHA-1C (12-O-(4-nitro) benzoyl; MIC 12.5 µg/mL) and DHA-1D (12-O-chloro acetyl; MIC 3.12µg/mL) showed significant activity against the pathogen. Results: In silico studies of the most active derivative (DHA-1D) showed interaction with ARG448 inhibiting the mycobacterium enzymes. Additionally, it showed no cytotoxicity towards the Vero C1008 cells and Mouse bone marrow derived macrophages. Conclusion: DHA-1D killed 62% intracellular M. tuberculosis in Mouse bone marrow macrophage infection model. To the best of our knowledge, this is the first-ever report on the antitubercular potential of dihydroartemisinin and its derivatives. Since dihydroartemisinin is widely used as an antimalarial drug; these results may be of great help in anti-tubercular drug development from a very common, inexpensive, and non-toxic natural product.

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In Silico Predicted Antifungal Peptides: In Vitro and In Vivo Anti-Candida Activity

Journal of Fungi ◽

10.3390/jof7060439 ◽

2021 ◽

Vol 7 (6) ◽

pp. 439

Author(s):

Tecla Ciociola ◽

Walter Magliani ◽

Tiziano De Simone ◽

Thelma A. Pertinhez ◽

Stefania Conti ◽

...

Keyword(s):

In Silico ◽

Mammalian Cells ◽

Galleria Mellonella ◽

Ex Vivo ◽

Consensus Sequence ◽

In Silico Analysis ◽

Significant Activity ◽

Synthetic Antibody

It has been previously demonstrated that synthetic antibody-derived peptides could exert a significant activity in vitro, ex vivo, and/or in vivo against microorganisms and viruses, as well as immunomodulatory effects through the activation of immune cells. Based on the sequence of previously described antibody-derived peptides with recognized antifungal activity, an in silico analysis was conducted to identify novel antifungal candidates. The present study analyzed the candidacidal and structural properties of in silico designed peptides (ISDPs) derived by amino acid substitutions of the parent peptide KKVTMTCSAS. ISDPs proved to be more active in vitro than the parent peptide and all proved to be therapeutic in Galleria mellonella candidal infection, without showing toxic effects on mammalian cells. ISDPs were studied by circular dichroism spectroscopy, demonstrating different structural organization. These results allowed to validate a consensus sequence for the parent peptide KKVTMTCSAS that may be useful in the development of novel antimicrobial molecules.

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Phage Resistance Is Associated with Decreased Virulence in KPC-Producing Klebsiella pneumoniae of the Clonal Group 258 Clade II Lineage

Microorganisms ◽

10.3390/microorganisms9040762 ◽

2021 ◽

Vol 9 (4) ◽

pp. 762

Author(s):

Lucia Henrici De Angelis ◽

Noemi Poerio ◽

Vincenzo Di Pilato ◽

Federica De Santis ◽

Alberto Antonelli ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

Parental Strain ◽

Bacterial Infections ◽

Capsular Polysaccharide ◽

Galleria Mellonella ◽

Bacterial Pathogen ◽

Phage Resistance ◽

Infection Model ◽

Lytic Phage ◽

Susceptible Host

Phage therapy is now reconsidered with interest in the treatment of bacterial infections. A major piece of information for this application is the definition of the molecular targets exploited by phages to infect bacteria. Here, the genetic basis of resistance to the lytic phage φBO1E by its susceptible host Klebsiella pneumoniae KKBO-1 has been investigated. KKBO-1 phage-resistant mutants were obtained by infection at high multiplicity. One mutant, designated BO-FR-1, was selected for subsequent experiments, including virulence assessment in a Galleria mellonella infection model and characterization by whole-genome sequencing. Infection with BO-FR-1 was associated with a significantly lower mortality when compared to that of the parental strain. The BO-FR-1 genome differed from KKBO-1 by a single nonsense mutation into the wbaP gene, which encodes a glycosyltransferase involved in the first step of the biosynthesis of the capsular polysaccharide (CPS). Phage susceptibility was restored when BO-FR-1 was complemented with the constitutive wbaP gene. Our results demonstrated that φBO1E infects KKBO-1 targeting the bacterial CPS. Interestingly, BO-FR-1 was less virulent than the parental strain, suggesting that in the context of the interplay among phage, bacterial pathogen and host, the emergence of phage resistance may be beneficial for the host.

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Designing P. aeruginosa synthetic phages with reduced genomes

Scientific Reports ◽

10.1038/s41598-021-81580-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Diana P. Pires ◽

Rodrigo Monteiro ◽

Dalila Mil-Homens ◽

Arsénio Fialho ◽

Timothy K. Lu ◽

...

Keyword(s):

Galleria Mellonella ◽

Antibacterial Properties ◽

Genetically Engineered ◽

In Vivo Studies ◽

Infection Model ◽

Promising Therapeutic Approach ◽

Genes Encoding ◽

First Time

AbstractIn the era where antibiotic resistance is considered one of the major worldwide concerns, bacteriophages have emerged as a promising therapeutic approach to deal with this problem. Genetically engineered bacteriophages can enable enhanced anti-bacterial functionalities, but require cloning additional genes into the phage genomes, which might be challenging due to the DNA encapsulation capacity of a phage. To tackle this issue, we designed and assembled for the first time synthetic phages with smaller genomes by knocking out up to 48% of the genes encoding hypothetical proteins from the genome of the newly isolated Pseudomonas aeruginosa phage vB_PaeP_PE3. The antibacterial efficacy of the wild-type and the synthetic phages was assessed in vitro as well as in vivo using a Galleria mellonella infection model. Overall, both in vitro and in vivo studies revealed that the knock-outs made in phage genome do not impair the antibacterial properties of the synthetic phages, indicating that this could be a good strategy to clear space from phage genomes in order to enable the introduction of other genes of interest that can potentiate the future treatment of P. aeruginosa infections.

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Emergence of ceftazidime/avibactam resistance in KPC-3-producing Klebsiella pneumoniae in vivo

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkz330 ◽

2019 ◽

Vol 74 (11) ◽

pp. 3211-3216 ◽

Cited By ~ 13

Author(s):

Stephan Göttig ◽

Denia Frank ◽

Eleonora Mungo ◽

Anika Nolte ◽

Michael Hogardt ◽

...

Keyword(s):

Combination Therapy ◽

Klebsiella Pneumoniae ◽

Selection Pressure ◽

Galleria Mellonella ◽

Phenotypic Characterization ◽

Infection Model ◽

Development Of Resistance ◽

Time Kill

Abstract Objectives The β-lactam/β-lactamase inhibitor combination ceftazidime/avibactam is active against KPC-producing Enterobacterales. Herein, we present molecular and phenotypic characterization of ceftazidime/avibactam resistance in KPC-3-producing Klebsiella pneumoniae that emerged in vivo and in vitro. Methods Sequence analysis of blaKPC-3 was performed from clinical and in vitro-generated ceftazidime/avibactam-resistant K. pneumoniae isolates. Time–kill kinetics and the Galleria mellonella infection model were applied to evaluate the activity of ceftazidime/avibactam and imipenem alone and in combination. Results The ceftazidime/avibactam-resistant clinical K. pneumoniae isolate revealed the amino acid change D179Y in KPC-3. Sixteen novel mutational changes in KPC-3 among in vitro-selected ceftazidime/avibactam-resistant isolates were described. Time–kill kinetics showed the emergence of a resistant subpopulation under selection pressure with either imipenem or ceftazidime/avibactam. However, combined selection pressure with imipenem plus ceftazidime/avibactam prevented the development of resistance and resulted in bactericidal activity. Concordantly, the G. mellonella infection model revealed that monotherapy with ceftazidime/avibactam is prone to select for resistance in vivo and that combination therapy with imipenem results in significantly better survival. Conclusions Ceftazidime/avibactam is a valuable antibiotic against MDR and carbapenem-resistant Enterobacterales. Based on time–kill kinetics as well as an in vivo infection model we postulate a combination therapy of ceftazidime/avibactam and imipenem as a strategy to prevent the development of ceftazidime/avibactam resistance in KPC-producing Enterobacterales in vivo.

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