A Contemporary Warming/Restraining Device for Efficient Tail Vein Injections in a Murine Fungal Sepsis Model

In rodent models, tail vein injections are important methods for intravenous administration of experimental agents. Tail vein injections typically involve ...

Tulane University School of Medicine

Denture stomatitis (DS) is a condition characterized by inflammation of the oral mucosa in direct contact with dentures and affects a significant number of otherwise healthy denture wearers. associated DS is predominantly caused by , a dimorphic fungus that readily colonizes and forms biofilms on denture materials. Previous studies showed a requirement for  biofilm formation on both palate and dentures in infection and identified fungal morphogenic transcription factors, Efg1 and Bcr1, as key players in DS pathogenesis. While both  and  are frequently coisolated in mucosal candidiasis, a pathogenic role for  in DS remains unknown. Using an established rat model of DS, we sought to determine whether  alone or coinoculation with  establishes colonization and causes palatal tissue damage and inflammation. Rats fitted with custom dentures were inoculated with  and/or  and monitored over a 4-week period for fungal burden (denture/palate), changes in body weight, and tissue damage via lactate dehydrogenase (LDH) release as well as palatal staining by hematoxylin and eosin (H&E) and immunohistochemistry for myeloperoxidase (MPO) as measures of inflammation.  colonized the denture/palate similarly to  In contrast to , colonization by  resulted in minimal changes in body weight, palatal LDH release, and MPO expression. Coinoculation with both species had no obvious modulation of -mediated pathogenic effects. These data suggest that  readily establishes colonization on denture and palate but has no apparent role for inducing/enhancing  pathogenesis in DS. Many denture wearers suffer from -associated denture stomatitis (DS), a fungal infection of the hard palate in contact with dentures. Biofilm formation by  on denture/palate surfaces is considered a central process in the infection onset. Although  is frequently coisolated with , its role in DS pathogenesis is unknown. We show here, using a contemporary rat model that employed a patented intraoral denture system, that  established stable colonization on the denture/palate. However, in contrast to  inoculated rats, rats inoculated with  exhibited minimal changes in weight gain or palatal tissue damage. Likewise, coinoculation with the two  species resulted in no exacerbation of -induced DS pathology. Together, our findings indicate that  has no inducing/enhancing role in DS pathogenesis.

Candida glabrata Has No Enhancing Role in the Pathogenesis of -Associated Denture Stomatitis in a Rat Model.

Polymicrobial sepsis is difficult to diagnose and treat and causes significant morbidity and mortality, especially when fungi are involved. In vitro, synergism between  and various bacterial species has been described for many years. Our laboratory has developed a murine model of polymicrobial intra-abdominal infection with  and , demonstrating that polymicrobial infections cause high levels of mortality, while monoinfections do not. By contrast, closely related  does not cause synergistic lethality and rather provides protection against lethal polymicrobial infection. This protection is thought to be driven by a novel form of trained innate immunity mediated by myeloid-derived suppressor cells (MDSCs), which we are proposing to call "trained tolerogenic immunity". MDSC accumulation has been described in patients with sepsis, as well as in in vivo sepsis models. However, clinically, MDSCs are considered detrimental in sepsis, while their role in in vivo models differs depending on the sepsis model and timing. In this review, we will discuss the role of MDSCs in sepsis and infection and summarize our perspectives on their development and function in the spectrum of trained innate immune protection against fungal-bacterial sepsis.

 Polymicrobial Intra-Abdominal Infection: Pathogenesis and Perspectives for a Novel Form of Trained Innate Immunity.

 and  are among the most prevalent nosocomial pathogens that are responsible for severe morbidity and mortality, even with appropriate treatment. Using a murine model of polymicrobial intra-abdominal infection (IAI), we have previously shown that coinfection with these pathogens results in synergistic lethality that is partially dependent on exacerbated prostaglandin signaling, while monomicrobial infection is nonlethal. Therefore, the objective of this study was to identify staphylococcal virulence determinants that drive lethal synergism during polymicrobial IAI. Using the toxigenic  strain JE2, we observed that coinfection with  led to a striking 80 to 100% mortality rate within 20 h postinoculation (p.i.) while monomicrobial infections were nonlethal. Use of a green fluorescent protein (GFP)-P3 promoter  reporter strain revealed enhanced activation of the staphylococcal  quorum sensing system during  polymicrobial versus monomicrobial growth. Analyses by quantitative real-time PCR (qPCR), Western blot, and toxin functional assays confirmed enhanced -associated gene transcription and increases in secreted alpha- and delta-toxins. -mediated elevated toxin production and hemolytic activity were determined to be  dependent, and genetic knockout and complementation of  identified alpha-toxin as the key staphylococcal virulence factor driving lethal synergism. Analysis of mono- and polymicrobial infections 8 h p.i. demonstrated equivalent bacterial burdens in the peritoneal cavity but significantly elevated levels of alpha-toxin (3-fold) and the eicosanoid prostaglandin E (PGE) (4-fold) during coinfection. Importantly, prophylactic passive immunization using the monoclonal anti-alpha-toxin antibody MEDI4893* led to significantly improved survival rates compared to those following treatment with isotype control antibody. Collectively, these results define alpha-toxin as an essential virulence determinant during - IAI and describe a novel mechanism by which a human-pathogenic fungus can augment the virulence of a highly pathogenic bacterium  Relatively little is known about the complex interactions and signaling events that occur between microbes and even less so about how microbial "cross talk" shapes human health and disease.  (a fungus) and  (a bacterium) are formidable human nosocomial pathogens, causing severe morbidity and mortality. Moreover, they are frequently coisolated from central venous catheters and deep-seated infections, including intra-abdominal sepsis. In this work, we have shown that coinfection with  and  is highly lethal, leading to >80% mortality by day 1 postinfection, whereas monoinfection with  or  does not cause mortality. This infectious synergism is dependent on the expression of staphylococcal alpha-toxin, and secretion of this potent virulence factor is actually augmented by  via an -dependent mechanism. Moreover, prophylactic neutralization of alpha-toxin with a monoclonal antibody is sufficient to elicit protection during coinfection. Therefore, we have demonstrated that a pathogenic fungus can enhance virulence determinants of a bacterium  with devastating consequences to the host. These results have important implications in the surveillance and treatment of polymicrobial disease and highlight the dynamic intersection of environment, pathogens, and host.

Candida albicans Augments Staphylococcus aureus Virulence by Engaging the Staphylococcal  Quorum Sensing System.

We would like to thank all the contributors to the Special Issue on Fungal-Bacterial Interactions-Current Knowledge and Future Perspectives [...].

Special Issue: Fungal-Bacterial Interactions-Current Knowledge and Future Perspectives.

Disease is a complex outcome that can occur as a result of pathogen-mediated damage, host-mediated damage or both. This has led to the revolutionary concept of the damage response framework (DRF) that defines microbial virulence as a function of host immunity. The DRF outlines six scenarios (classes) of host damage or beneficial outcomes, depending on the microbe and the strength of the immune response.  is uniquely adapted to its human host and can exist as either a commensal, colonizing various anatomical sites without causing notable damage, or as a pathogen, with the ability to cause a diverse array of diseases, ranging from mucosal to invasive systemic infections that result in varying levels of microbe-mediated and/or host-mediated damage. We recently categorized six different forms of candidiasis (oropharyngeal, hematogenous, intra-abdominal, gastrointestinal, denture stomatitis, and vulvovaginitis) into independent DRF classes, supporting a contemporary view of unique mechanisms of pathogenesis for these  infections. In this review, we summarize the evidence for the pathogenesis of these various forms of candidiasis in the context of the DRF with the further intent to provide insights into strategies to achieve a level of host response or outcome otherwise, that limits host damage.

Applying the Host-Microbe Damage Response Framework to  Pathogenesis: Current and Prospective Strategies to Reduce Damage.

We propose the concept that administration of an unrelated live attenuated vaccine, such as MMR (measles, mumps, rubella), could serve as a preventive measure against the worst sequelae of coronavirus disease 2019 (COVID-19). There is mounting evidence that live attenuated vaccines provide nonspecific protection against lethal infections unrelated to the target pathogen of the vaccine by inducing "trained" nonspecific innate immune cells for improved host responses against subsequent infections. Mortality in COVID-19 cases is strongly associated with progressive lung inflammation and eventual sepsis. Vaccination with MMR in immunocompetent individuals has no contraindications and may be especially effective for health care workers who can easily be exposed to COVID-19. Following the lead of other countries conducting clinical trials with the live attenuated  BCG (BCG) vaccine under a similar concept, a clinical trial with MMR in high-risk populations may provide a "low-risk-high-reward" preventive measure in saving lives during this unprecedented COVID-19 pandemic.

Mairi C. Noverr

Department of Microbiology and Immunology

Tulane University School of Medicine

A Contemporary Warming/Restraining Device for Efficient Tail Vein Injections in a Murine Fungal Sepsis Model

Mairi C. Noverr

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Microbiology and Immunology

Tulane University School of Medicine

A Contemporary Warming/Restraining Device for Efficient Tail Vein Injections in a Murine Fungal Sepsis Model

Department of Microbiology and Immunology