scholarly journals Optimization and Characterization of a Galleria mellonella Larval Infection Model for Virulence Studies and the Evaluation of Therapeutics Against Streptococcus pneumoniae

2019 ◽  
Vol 10 ◽  
Author(s):  
Freya Cools ◽  
Eveline Torfs ◽  
Juliana Aizawa ◽  
Bieke Vanhoutte ◽  
Louis Maes ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Galleria Mellonella ◽  
Infection Model ◽  
Larval Infection

scholarly journals Galleria mellonella Larvae as an Infection Model to Investigate sRNA-Mediated Pathogenesis in Staphylococcus aureus

2021 ◽  
Vol 11 ◽  
Author(s):  
Guillaume Ménard ◽  
Astrid Rouillon ◽  
Gevorg Ghukasyan ◽  
Mathieu Emily ◽  
Brice Felden ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Galleria Mellonella ◽  
Inflammatory Responses ◽  
Expression Profiles ◽  
Bacterial Pathogens ◽  
Infection Model ◽  
Animal Testing ◽  
Easy Method ◽  
Larval Infection ◽  
Over Time

Small regulatory RNAs (sRNAs) are key players in bacterial regulatory networks. Monitoring their expression inside living colonized or infected organisms is essential for identifying sRNA functions, but few studies have looked at sRNA expression during host infection with bacterial pathogens. Insufficient in vivo studies monitoring sRNA expression attest to the difficulties in collecting such data, we therefore developed a non-mammalian infection model using larval Galleria mellonella to analyze the roles of Staphylococcus aureus sRNAs during larval infection and to quickly determine possible sRNA involvement in staphylococcal virulence before proceeding to more complicated animal testing. We began by using the model to test infected larvae for immunohistochemical evidence of infection as well as host inflammatory responses over time. To monitor sRNA expression during infection, total RNAs were extracted from the larvae and invading bacteria at different time points. The expression profiles of the tested sRNAs were distinct and they fluctuated over time, with expression of both sprD and sprC increased during infection and associated with mortality, while rnaIII expression remained barely detectable over time. A strong correlation was observed between sprD expression and the mortality. To confirm these results, we used sRNA-knockout mutants to investigate sRNA involvement in Staphylococcus aureus pathogenesis, finding that the decrease in death rates is delayed when either sprD or sprC was lacking. These results demonstrate the relevance of this G. mellonella model for investigating the role of sRNAs as transcriptional regulators involved in staphylococcal virulence. This insect model provides a fast and easy method for monitoring sRNA (and mRNA) participation in S. aureus pathogenesis, and can also be used for other human bacterial pathogens.

Characterization of Streptococcus pneumoniae phage-like element SpnCI reveals an enhanced virulent phenotype in the acute invertebrate infection model Galleria mellonella

2019 ◽  
Author(s):  
Kimberly McCullor ◽  
Maliha Rahman ◽  
Catherine King ◽  
W. Michael McShan
Keyword(s):  
Streptococcus Pneumoniae ◽  
Galleria Mellonella ◽  
Diagnostic Tools ◽  
Infection Model ◽  
Pneumococcal Infections ◽  
Health Score ◽  
Survival Percentage ◽  
Pneumococcal Strain ◽  
Streptococcal Species ◽  
Virulent Phenotype

AbstractPhage-like elements are found in a multitude of streptococcal species, including pneumococcal strain Hungary19A-6 (SpnCI). The aim of our research was to investigate the role of phage-like element SpnCI in enhanced virulence and phenotypic modulation within Streptococcus pneumoniae. SpnCI was found to significantly enhance virulence within the invertebrate infection model Galleria mellonella. Infections with SpnCI led to a lower mean health score (1.6) and survival percentage (20%) compared to SpnCI null TIGR4 infections (3.85 mean health score and 50% survival). SpnCI remained integrated throughout growth, conferring greater sensitivity to UV irradiation. Change in transcriptional patterns occurred, including downregulation of operons involved with cell surface modelling in the SpnCI containing strain of TIGR4. Kanamycin-tagged SpnCI strain in Hungary19A-6 was inducible and isolated from lysate along with both annotated prophages. No phages were identified by PCR nor electron microscopy (EM) following induction of TIGR4 SpnCIΔstrA suggesting helper-phage dependence for dissemination. EM of lysate showed typical siphoviridae morphology with an average capsid size of 60 nm. Two of sixty capsids were found to be smaller, suggesting SpnCI disseminates using a similar mechanism described for Staphylococcus aureus phage-like element SaPI. SpnCI from lysate infected capsule null strain T4R but was incapable of infecting the encapsulated TIGR4 strain suggesting that capsule impedes phage infection. Our work demonstrates that SpnCI can modulate virulence, UV susceptibility, alter transcriptional patterns, and furthermore, can disseminate via infection within pneumococcus. Further research is necessary to elucidate how SpnCI modulates virulence and what genes are responsible for the enhanced virulence phenotype.ImportanceAlthough vaccines have limited the scope of pneumococcal infections, Streptococcus pneumoniae still remains an important human pathogen. Understanding novel elements, such as SpnCI, that enhance virulence can lead to the development of more targeted therapeutic and diagnostic tools within the clinical realm.

Glutamate dehydrogenase (GdhA) of Streptococcus pneumoniae is required for high temperature adaptation

2021 ◽  
Author(s):  
Ozcan Gazioglu ◽  
Banaz O. Kareem ◽  
Muhammad Afzal ◽  
Sulman Shafeeq ◽  
Oscar P. Kuipers ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Glutamate Dehydrogenase ◽  
Galleria Mellonella ◽  
Thermal Adaptation ◽  
Transcriptional Response ◽  
Temperature Adaptation ◽  
Effect Of Temperature ◽  
Infection Model ◽  
Dependent Manner

During its progression from the nasopharynx to other sterile and non-sterile niches of its human host, Streptococcus pneumoniae must cope with changes in temperature. We hypothesised that the temperature adaptation is an important facet of pneumococcal survival in the host. Here, we evaluated the effect of temperature on pneumococcus and studied the role of glutamate dehydrogenase (GdhA) in thermal adaptation associated with virulence and survival. Microarray analysis revealed a significant transcriptional response to changes in temperature, affecting the expression of 252 genes in total at 34°C and 40°C relative to at 37°C. One of the differentially regulated genes was gdhA, which is upregulated at 40°C and downregulated at 34°C relative to 37°C. Deletion of gdhA attenuated the growth, cell size, biofilm formation, pH survival, and biosynthesis of proteins associated with virulence in a temperature-dependent manner. Moreover, deletion of gdhA stimulated formate production irrespective of temperature fluctuation. Finally, Δ gdhA grown at 40°C was less virulent compare to other temperatures or than the wild type at the same temperature in a Galleria mellonella infection model, suggesting that GdhA is required for pneumococcal virulence at elevated temperature.

In vivo synergism of ampicillin, gentamicin, ceftaroline and ceftriaxone against Enterococcus faecalis assessed in the Galleria mellonella infection model

2020 ◽  
Author(s):  
Lara Thieme ◽  
Anita Hartung ◽  
Oliwia Makarewicz ◽  
Mathias W Pletz
Keyword(s):  
Enterococcus Faecalis ◽  
Galleria Mellonella ◽  
Synergistic Effects ◽  
Agar Plate ◽  
Infection Model ◽  
Pharmacokinetic Data ◽  
Multiple Dosing ◽  
Larval Infection

Abstract Background The unfavourable safety profile of aminoglycosides and the synergistic effects observed in vitro have prompted the development of novel dual β-lactam therapies, e.g. ampicillin/ceftriaxone or ampicillin/ceftaroline, for the treatment of Enterococcus faecalis endocarditis. Objectives For comparison with in vitro chequerboard assay results, a partial chequerboard setup of ampicillin/gentamicin, ampicillin/ceftriaxone and ampicillin/ceftaroline against E. faecalis was established in the Galleria mellonella larval infection model. Methods Discrimination of synergistic and additive interactions was based on the evaluation of larval survival, bacterial quantity in the haemolymph and a pathology score index (internal to the workgroup). Single and multiple dosing schemes based on the half-life of ampicillin were applied. Pharmacokinetic data of the antibiotics in the larvae were determined via agar plate diffusion assays. Results Ampicillin and ceftriaxone exhibited strain-specific synergistic interactions in the larvae under both dosing regimens, while the other two combinations showed additive effects. Ampicillin/ceftaroline was inferior to ampicillin/ ceftriaxone. Not all synergistic effects observed in vitro could be replicated in the larvae. Conclusions Our results suggest superior efficacy of ampicillin/ceftriaxone for the treatment of high-inoculum enterococcal infections, for at least some strains, but question the benefit of the current standard of adding the nephrotoxic gentamicin compared with the safer ceftriaxone. This is the first study to develop a scheme for differentiation between additive and synergistic effects in larvae and apply a multiple-antibiotic dosing scheme based on the pharmacokinetics of ampicillin. The model allows the analysis of synergistic effects of antimicrobials in an in vivo setting, but the clinical correlation warrants further study.

scholarly journals Characterization of carbapenem-resistant hypervirulent Acinetobacter baumannii strains isolated from hospitalized patients in the mid-south region of China

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Jun Li ◽  
Ting Yu ◽  
Yi Luo ◽  
Jing-Yi Peng ◽  
Yu-Jia Li ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Acinetobacter Baumannii ◽  
High Mortality ◽  
Galleria Mellonella ◽  
Opportunistic Pathogen ◽  
Infection Model ◽  
Carbapenem Resistant ◽  
Blood Specimens ◽  
Sequence Types

Abstract Background Acinetobacter baumannii has traditionally been considered an opportunistic pathogen with low virulence. In this study, we characterized the carbapenem-resistant hypervirulent A. baumannii (CR-hvAB) stains isolated from our hospital in mid-south region of China. Results Blood samples collected between January 2017 and May 2019 were used for virulence experiments and biofilm assays of individual carbapenem-resistant A. baumannii (CR-AB) strains, performed using a Galleria mellonella infection model and crystal violet staining method, respectively. CR-AB isolates that induced high mortality in the G. mellonella infection model were subjected to genotyping, susceptibility testing, and clinical data analysis, and the genetic characterization of these isolates was performed by whole-genome sequencing (WGS). Among the 109 CR-AB clinical strains, the survival rate of G. mellonella larvae infected with 7 (6.4%) CR-AB isolates (number of strains with mortality of 0, 10 and 20% was 4, 1, and 2, respectively), was significantly lower than that of A. baumannii ATCC 19606 (100.0%) and the remaining CR-AB isolates (> 80.0%). Consistent with these results, patients infected with these seven isolates had an average 7-day mortality rate of 42.9%, suggesting that the isolates were CR-hvAB. These seven isolates belonged to four sequence types (STs): ST457, ST195, ST369, and ST2088 (a new ST), and mainly ST457 (n = 4). The results of the biofilm study showed that eight strains had powerful biofilm ability (strong [n = 1] and moderate [n = 7] biofilm producers) including these seven CR-hvAB isolates. Conclusions CR-hvAB isolates that induced a high mortality rate were cloned in our hospital, most of which belonged to ST457; thus, monitoring of these strains, particularly ST457, should be strengthened in the future. Meanwhile, A. baumannii, which was isolated from blood specimens and found to powerful biofilm-forming ability, is a probable hvAB isolate.

scholarly journals Type VI secretion system and its effectors PdpC, PdpD and OpiA contribute to Francisella virulence in Galleria mellonella larvae

2021 ◽  
Author(s):  
Maj Brodmann ◽  
Sophie Schnider ◽  
Marek Basler
Keyword(s):  
Galleria Mellonella ◽  
Response Regulator ◽  
Infection Model ◽  
Type Vi Secretion System ◽  
Infectious Dose ◽  
Infection Models

Francisella tularensis causes the deadly zoonotic disease tularemia in humans and is able to infect a broad range of organisms including arthropods, which are thought to play a major role in Francisella transmission. However, while mammalian in vitro and in vivo infection models are widely used to investigate Francisella pathogenicity, a detailed characterization of the major Francisella virulence factor, a non-canonical T6SS, in an arthropod in vivo infection model is missing. Here we use Galleria mellonella larvae to analyze the role of the Francisella T6SS and its corresponding effectors in F. novicida virulence. We report that G. mellonella larvae killing depends on the functional T6SS and infectious dose. In contrast to other mammalian in vivo infection models, even one of PdpC, PdpD or OpiA T6SS effectors is sufficient to kill G. mellonella larvae while sheath recycling by ClpB is dispensable. We further demonstrate that treatment by polyethylene glycol (PEG) activates Francisella T6SS in liquid culture and that this is independent of the response regulator PmrA. PEG-activated IglC secretion is dependent on T6SS structural component PdpB but independent of putative effectors PdpC, PdpD, AnmK and OpiB1-3. The results of larvae infection and secretion assay suggest that AnmK, a putative T6SS component with unknown function, interferes with OpiA-mediated toxicity but not with general T6SS activity. We establish that the easy-to-use G. mellonella larvae infection model provides new insights into function of T6SS and pathogenesis of Francisella.

scholarly journals Characterization of the Differential Pathogenicity of Candida auris in a Galleria mellonella Infection Model

2021 ◽  
Author(s):  
Victor Garcia-Bustos ◽  
Amparo Ruiz-Saurí ◽  
Alba Ruiz-Gaitán ◽  
Ignacio Antonio Sigona-Giangreco ◽  
Marta Dafne Cabañero-Navalon ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Galleria Mellonella ◽  
Infection Model ◽  
Host Pathogen Interactions ◽  
Candida Auris ◽  
Content Type ◽  
Host Pathogen ◽  
Global Threat

Candida auris is an emergent fungus that has become a global threat due to its multidrug resistance, mortality, and transmissibility. These unique features make it different from other Candida species, but we still do not fully know the degree of virulence and, especially, the host-pathogen interactions.

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