Neonatal Coinfection Model of Coagulase-Negative Staphylococcus (Staphylococcus epidermidis) and Candida albicans: Fluconazole Prophylaxis Enhances Survival and Growth

ABSTRACT Coagulase-negative staphylococci (CoNS) and Candida are among the most common causes of single infections and coinfections in neonates after 72 h of age. In neonates, coinfection increases the rate of mortality threefold and results in significantly greater morbidity compared to those that result from single infections. In an effort to better understand this phenomenon, we developed the first neonatal animal model of coinfection (with CoNS and Candida) and evaluated its effects on mortality and morbidity and the impact of antifungal prophylaxis with fluconazole. Neonatal Wistar rats were infected with Candida albicans and/or Staphylococcus epidermidis with doses of 2 × 108 and 2 × 106 CFU subcutaneously in different combinations and were monitored for mortality, weight gain, and bacteremia. The in vitro sensitivity of C. albicans to fluconazole was evaluated and the MIC was determined. A subset of rats in these experiments received fluconazole at 10 mg/kg of body weight/dose intraperitoneally starting 24 h before infection for 4 days, and the serum trough levels of fluconazole were measured. Coinfection in the suckling rat significantly increased the rate of mortality compared to that after infection with a single species (P < 0.001) and resulted in deaths even at sublethal doses. Coinfection also impaired weight gain significantly in severely infected pups compared to that achieved after infection with a single species (P < 0.001). Fluconazole prophylaxis significantly reduced mortality by 30% in the Candida group and 36% in the coinfection group and improved weight gain in this neonatal model of coinfection (P < 0.001). We developed a neonatal model of coinfection with Candida and CoNS, observed significantly greater mortality and morbidity with coinfection, and found that fluconazole prophylaxis significantly reduced the rates of both mortality and morbidity. Further research on neonatal coinfection is urgently needed to improve clinical outcomes.

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Staphylococcus epidermidis Has Growth Phase Dependent Affinity for Fibrinogen and Resulting Fibrin Clot Elasticity

Frontiers in Microbiology ◽

10.3389/fmicb.2021.649534 ◽

2021 ◽

Vol 12 ◽

Author(s):

Carolyn Vitale ◽

Tianhui Maria Ma ◽

Janice Sim ◽

Christopher Altheim ◽

Erika Martinez-Nieves ◽

...

Keyword(s):

Bacterial Infection ◽

Growth Phase ◽

Staphylococcus Epidermidis ◽

Fibrin Clot ◽

Exponential Phase ◽

Clot Formation ◽

Coagulase Negative Staphylococci ◽

Phase Dependence ◽

The Impact

Bacterial infection and thrombosis are highly correlated, especially in patients with indwelling medical devices. Coagulase-negative staphylococci, typified by Staphylococcus epidermidis, are a common cause of medical device infections owing to their biofilm forming capacity which provides protection from antibiotics and host immune response. Attention has been drawn to the interaction between S. epidermidis and host proteins, specifically fibrinogen. However, little is known regarding the impact of the transition from planktonic to biofilm forming phenotype on this interaction. Here we investigate the growth phase dependence of bacteria-fibrinogen interaction and the resulting effect on fibrin clot formation, structure, and mechanics. Flow cytometry demonstrated growth phase dependent affinity for fibrinogen. To mimic intravascular device seeding, we quantified the adhesion of S. epidermidis to a fibrinogen coated surface under continuous flow conditions in vitro. The bacterial deposition rate onto fibrinogen was significantly greater for stationary (5,360 ± 1,776 cells/cm2s) versus exponential phase (2,212 ± 264, cells/cm2 s). Furthermore, the expression of sdrG–a cell surface adhesion protein with specificity for fibrinogen–was upregulated ∼twofold in the stationary versus the exponential phase. Rheometry and confocal microscopy demonstrated that stationary phase S. epidermidis slows clot formation and generates a more heterogeneous fibrin network structure with greater elasticity (G′ = 5.7 ± 1.0 Pa) compared to sterile fibrinogen (G′ = l.5 ± 0.2 Pa), while exponential phase cells had little effect. This work contributes to the current understanding of the growth phase dependent regulation of bacterial virulence factors and the correlation between bacterial infection and thrombosis.

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Production of Noncapped Genomic RNAs Is Critical to Sindbis Virus Disease and Pathogenicity

mBio ◽

10.1128/mbio.02675-20 ◽

2020 ◽

Vol 11 (6) ◽

Author(s):

Autumn T. LaPointe ◽

V Douglas Landers ◽

Claire E. Westcott ◽

Kevin J. Sokoloski

Keyword(s):

Sindbis Virus ◽

Virus Disease ◽

Severe Disease ◽

Wild Type Virus ◽

Wild Type ◽

Genomic Rnas ◽

Mortality And Morbidity ◽

The Impact

ABSTRACT Alphaviruses are positive-sense RNA viruses that utilize a 5′ cap structure to facilitate translation of viral proteins and to protect the viral RNA genome. Nonetheless, significant quantities of viral genomic RNAs that lack a canonical 5′ cap structure are produced during alphaviral replication and packaged into viral particles. However, the role/impact of the noncapped genomic RNA (ncgRNA) during alphaviral infection in vivo has yet to be characterized. To determine the importance of the ncgRNA in vivo, the previously described D355A and N376A nsP1 mutations, which increase or decrease nsP1 capping activity, respectively, were incorporated into the neurovirulent AR86 strain of Sindbis virus to enable characterization of the impact of altered capping efficiency in a murine model of infection. Mice infected with the N376A nsP1 mutant exhibited slightly decreased rates of mortality and delayed weight loss and neurological symptoms, although levels of inflammation in the brain were similar to those of wild-type infection. Although the D355A mutation resulted in decreased antiviral gene expression and increased resistance to interferon in vitro, mice infected with the D355A mutant showed significantly reduced mortality and morbidity compared to mice infected with wild-type virus. Interestingly, expression of proinflammatory cytokines was found to be significantly decreased in mice infected with the D355A mutant, suggesting that capping efficiency and the production of ncgRNA are vital to eliciting pathogenic levels of inflammation. Collectively, these data indicate that the ncgRNA have important roles during alphaviral infection and suggest a novel mechanism by which noncapped viral RNAs aid in viral pathogenesis. IMPORTANCE Mosquito-transmitted alphaviruses have been the cause of widespread outbreaks of disease that can range from mild illness to lethal encephalitis or severe polyarthritis. There are currently no safe and effective vaccines or therapeutics with which to prevent or treat alphaviral disease, highlighting the need to better understand alphaviral pathogenesis to develop novel antiviral strategies. This report reveals production of noncapped genomic RNAs (ncgRNAs) to be a novel determinant of alphaviral virulence and offers insight into the importance of inflammation to pathogenesis. Taken together, the findings reported here suggest that the ncgRNAs contribute to alphaviral pathogenesis through the sensing of the ncgRNAs during alphaviral infection and are necessary for the development of severe disease.

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Impact of the Order of Initiation of Fluconazole and Amphotericin B in Sequential or Combination Therapy on Killing of Candida albicans In Vitro and in a Rabbit Model of Endocarditis and Pyelonephritis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.45.2.485-494.2001 ◽

2001 ◽

Vol 45 (2) ◽

pp. 485-494 ◽

Cited By ~ 40

Author(s):

Arnold Louie ◽

Pamela Kaw ◽

Partha Banerjee ◽

Weiguo Liu ◽

George Chen ◽

...

Keyword(s):

Candida Albicans ◽

Amphotericin B ◽

Induced Resistance ◽

Rabbit Model ◽

In Vivo Studies ◽

Infection Model ◽

Simultaneous Exposure ◽

The Impact

ABSTRACT In vitro time-kill studies and a rabbit model of endocarditis and pyelonephritis were used to define the impact that the order of exposure of Candida albicans to fluconazole (FLC) and amphotericin B (AMB), as sequential and combination therapies, had on the susceptibility of C. albicans to AMB and on the outcome. The contribution of FLC-induced resistance to AMB for C. albicans also was assessed. In vitro, AMB monotherapy rapidly killed each of four C. albicans strains; FLC alone was fungistatic. Preincubation of these fungi with FLC for 18 h prior to exposure to AMB decreased their susceptibilities to AMB for 8 to >40 h. Induced resistance to AMB was transient, but the duration of resistance increased with the length of FLC preincubation. Yeast sequentially incubated with FLC followed by AMB plus FLC (FLC→AMB+FLC) showed fungistatic growth kinetics similar to that of fungi that were exposed to FLC alone. This antagonistic effect persisted for at least 24 h. Simultaneous exposure of C. albicans to AMB and FLC [AMB+FLC(simult)] demonstrated activity similar to that with AMB alone for AMB concentrations of ≥1 μg/ml; antagonism was seen using an AMB concentration of 0.5 μg/ml. The in vitro findings accurately predicted outcomes in our rabbit infection model. In vivo, AMB monotherapy and treatment with AMB for 24 h followed by AMB plus FLC (AMB→AMB+FLC) rapidly sterilized kidneys and cardiac vegetations. AMB+FLC(simult) and FLC→AMB treatments were slower in clearing fungi from infected tissues. FLC monotherapy and FLC→AMB+FLC were both fungistatic and were the least active regimens. No adverse interaction was observed between AMB and FLC for the AMB→FLC regimen. However, FLC→AMB treatment was slower than AMB alone in clearing fungi from tissues. Thus, our in vitro and in vivo studies both demonstrate that preexposure of C. albicans to FLC reduces fungal susceptibility to AMB. The length of FLC preexposure and whether AMB is subsequently used alone or in combination with FLC determine the duration of induced resistance to AMB.

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Impact of Bacterial Biofilm Formation on In Vitro and In Vivo Activities of Antibiotics

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.4.895 ◽

1998 ◽

Vol 42 (4) ◽

pp. 895-898 ◽

Cited By ~ 112

Author(s):

Silvia Schwank ◽

Zarko Rajacic ◽

Werner Zimmerli ◽

Jürg Blaser

Keyword(s):

Animal Model ◽

Staphylococcus Epidermidis ◽

Biofilm Formation ◽

Bacterial Biofilm ◽

Phenotypic Resistance ◽

Vitro Model ◽

The Impact ◽

Isogenic Strains

ABSTRACT The impact of bacterial adherence on antibiotic activity was analyzed with two isogenic strains of Staphylococcus epidermidis that differ in the features of their in vitro biofilm formation. The eradication of bacteria adhering to glass beads by amikacin, levofloxacin, rifampin, or teicoplanin was studied in an animal model and in a pharmacokinetically matched in vitro model. The features of S. epidermidis RP62A that allowed it to grow on surfaces in multiple layers promoted phenotypic resistance to antibiotic treatment, whereas strain M7 failed to accumulate, despite initial adherence on surfaces and growth in suspension similar to those for RP62A. Biofilms of S. epidermidis M7 were better eradicated than those of strain RP62A in vitro (46 versus 31%;P < 0.05) as well as in the animal model (39 versus 9%; P < 0.01).

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Symbiotic Relationship between Streptococcus mutans and Candida albicans Synergizes Virulence of Plaque BiofilmsIn Vivo

Infection and Immunity ◽

10.1128/iai.00087-14 ◽

2014 ◽

Vol 82 (5) ◽

pp. 1968-1981 ◽

Cited By ~ 216

Author(s):

Megan L. Falsetta ◽

Marlise I. Klein ◽

Punsiri M. Colonne ◽

Kathleen Scott-Anne ◽

Stacy Gregoire ◽

...

Keyword(s):

Candida Albicans ◽

Dental Caries ◽

Streptococcus Mutans ◽

Bacterial Pathogen ◽

Single Species ◽

Content Type ◽

3 Dimensional ◽

Biofilm Development

ABSTRACTStreptococcus mutansis often cited as the main bacterial pathogen in dental caries, particularly in early-childhood caries (ECC).S. mutansmay not act alone;Candida albicanscells are frequently detected along with heavy infection byS. mutansin plaque biofilms from ECC-affected children. It remains to be elucidated whether this association is involved in the enhancement of biofilm virulence. We showed that the ability of these organisms together to form biofilms is enhancedin vitroandin vivo. The presence ofC. albicansaugments the production of exopolysaccharides (EPS), such that cospecies biofilms accrue more biomass and harbor more viableS. mutanscells than single-species biofilms. The resulting 3-dimensional biofilm architecture displays sizeableS. mutansmicrocolonies surrounded by fungal cells, which are enmeshed in a dense EPS-rich matrix. Using a rodent model, we explored the implications of this cross-kingdom interaction for the pathogenesis of dental caries. Coinfected animals displayed higher levels of infection and microbial carriage within plaque biofilms than animals infected with either species alone. Furthermore, coinfection synergistically enhanced biofilm virulence, leading to aggressive onset of the disease with rampant carious lesions. Ourin vitrodata also revealed that glucosyltransferase-derived EPS is a key mediator of cospecies biofilm development and that coexistence withC. albicansinduces the expression of virulence genes inS. mutans(e.g.,gtfB,fabM). We also found thatCandida-derived β1,3-glucans contribute to the EPS matrix structure, while fungal mannan and β-glucan provide sites for GtfB binding and activity. Altogether, we demonstrate a novel mutualistic bacterium-fungus relationship that occurs at a clinically relevant site to amplify the severity of a ubiquitous infectious disease.

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Molecular Epidemiology of a Vancomycin-Intermediate Heteroresistant Staphylococcus epidermidis Outbreak in a Neonatal Intensive Care Unit

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00726-16 ◽

2016 ◽

Vol 60 (10) ◽

pp. 5673-5681 ◽

Cited By ~ 7

Author(s):

Jasmine Chong ◽

Caroline Quach ◽

Ana C. Blanchard ◽

Philippe Guillaume Poliquin ◽

George R. Golding ◽

...

Keyword(s):

Intensive Care ◽

Molecular Epidemiology ◽

Staphylococcus Epidermidis ◽

Population Analysis ◽

Tertiary Care ◽

Hospital Environment ◽

Coagulase Negative Staphylococci ◽

Time Curve ◽

Content Type ◽

The Impact

ABSTRACTCoagulase-negative staphylococci (CoNS) have become the leading cause of bloodstream infections (BSIs) in intensive care units (ICUs), particularly in premature neonates. Vancomycin-intermediate heteroresistant CoNS (hVICoNS) have been identified as sources of BSIs worldwide, and their potential to emerge as significant pathogens in the neonatal ICU (NICU) remains uncertain. This study describes the molecular epidemiology of an outbreak of vancomycin-heteroresistant (hV)Staphylococcus epidermidiscentral-line-associated BSI (CLABSI) in a single tertiary care NICU and compares it to a second tertiary care NICU that had not been associated with an outbreak. Between November 2009 and April 2014, 119S. epidermidisCLABSIs were identified in two tertiary care NICUs in Quebec, Canada. Decreased vancomycin susceptibility was identified in about 88% of all collected strains using Etest methods. However, discrepancies were found according to the Etest and population analysis profiling–area under the concentration-time curve (PAP-AUC) methods used. All strains were susceptible to linezolid, and a few isolates were nonsusceptible to daptomycin. Great genetic diversity was observed within the collection, with 31 pulsed-field gel electrophoresis (PFGE) patterns identified. The outbreak strains were all determined to be heteroresistant to vancomycin and were polyclonal. The study identified two major clones, PFGE patterns E and G, which were found in both NICUs across the 5-year study period. This suggests the persistence of highly successful clones that are well adapted to the hospital environment. hVS. epidermidisseems more common than currently realized in the NICU, and certain hVS. epidermidisclones can become endemic to the NICU. The reservoirs for these clones remain unknown at this time, and identification of the reservoirs is needed to better understand the impact of hVS. epidermidisin the NICU and to inform infection prevention strategies. In addition, there is a need to investigate and validate hV determination protocols for different species of CoNS.

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Oral Administration of the Broad-Spectrum Antibiofilm Compound Toremifene Inhibits Candida albicans and Staphylococcus aureus Biofilm FormationIn Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03869-14 ◽

2014 ◽

Vol 58 (12) ◽

pp. 7606-7610 ◽

Cited By ~ 16

Author(s):

Kaat De Cremer ◽

Nicolas Delattin ◽

Katrijn De Brucker ◽

Annelies Peeters ◽

Soña Kucharíková ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Candida Albicans ◽

Broad Spectrum ◽

Staphylococcus Epidermidis ◽

Biofilm Formation ◽

Candida Krusei ◽

Content Type ◽

And Staphylococcus Aureus

ABSTRACTWe here report on thein vitroactivity of toremifene to inhibit biofilm formation of different fungal and bacterial pathogens, includingCandida albicans,Candida glabrata,Candida dubliniensis,Candida krusei,Pseudomonas aeruginosa,Staphylococcus aureus, andStaphylococcus epidermidis. We validated thein vivoefficacy of orally administered toremifene againstC. albicans and S. aureusbiofilm formation in a rat subcutaneous catheter model. Combined, our results demonstrate the potential of toremifene as a broad-spectrum oral antibiofilm compound.

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Honeybee gut microbiota promotes host weight gain via bacterial metabolism and hormonal signaling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1701819114 ◽

2017 ◽

Vol 114 (18) ◽

pp. 4775-4780 ◽

Cited By ~ 148

Author(s):

Hao Zheng ◽

J. Elijah Powell ◽

Margaret I. Steele ◽

Carsten Dietrich ◽

Nancy A. Moran

Keyword(s):

Weight Gain ◽

Gut Microbiota ◽

Microbial Metabolism ◽

Short Chain Fatty Acids ◽

Short Chain ◽

Whole Body ◽

Social Bees ◽

Host Microbe Interactions ◽

The Impact

Social bees harbor a simple and specialized microbiota that is spatially organized into different gut compartments. Recent results on the potential involvement of bee gut communities in pathogen protection and nutritional function have drawn attention to the impact of the microbiota on bee health. However, the contributions of gut microbiota to host physiology have yet to be investigated. Here we show that the gut microbiota promotes weight gain of both whole body and the gut in individual honey bees. This effect is likely mediated by changes in host vitellogenin, insulin signaling, and gustatory response. We found that microbial metabolism markedly reduces gut pH and redox potential through the production of short-chain fatty acids and that the bacteria adjacent to the gut wall form an oxygen gradient within the intestine. The short-chain fatty acid profile contributed by dominant gut species was confirmed in vitro. Furthermore, metabolomic analyses revealed that the gut community has striking impacts on the metabolic profiles of the gut compartments and the hemolymph, suggesting that gut bacteria degrade plant polymers from pollen and that the resulting metabolites contribute to host nutrition. Our results demonstrate how microbial metabolism affects bee growth, hormonal signaling, behavior, and gut physicochemical conditions. These findings indicate that the bee gut microbiota has basic roles similar to those found in some other animals and thus provides a model in studies of host–microbe interactions.

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Time Course of Microbiologic Outcome and Gene Expression in Candida albicans during and following In Vitro and In Vivo Exposure to Fluconazole

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.50.4.1311-1319.2006 ◽

2006 ◽

Vol 50 (4) ◽

pp. 1311-1319 ◽

Cited By ~ 27

Author(s):

A. Lepak ◽

J. Nett ◽

L. Lincoln ◽

K. Marchillo ◽

D. Andes

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Time Course ◽

Dependent Manner ◽

Time Points ◽

In Vivo Expression ◽

The Impact ◽

The Relationship

ABSTRACT Pharmacodynamics (PD) considers the relationship between drug exposure and effect. The two factors that have been used to distinguish the PD behaviors of antimicrobials are the impact of concentration on the extent of organism killing and the duration of persistent microbiologic suppression (postantibiotic effect). The goals of these studies were (i) to examine the relationship between antimicrobial PD and gene expression and (ii) to gain insight into the mechanism of fluconazole effects persisting following exposure. Microarrays were used to estimate the transcriptional response of Candida albicans to a supra-MIC F exposure over time in vitro. Fluconazole at four times the MIC was added to a log-phase C. albicans culture, and cells were collected to determine viable growth and for microarray analyses. We identified differential expression of 18% of all genes for at least one of the time points. More genes were upregulated (n = 1,053 [16%]) than downregulated (174 [3%]). Of genes with known function that were upregulated during exposure, most were related to plasma membrane/cell wall synthesis (18%), stress responses (7%), and metabolism (6%). The categories of downregulated genes during exposure included protein synthesis (15%), DNA synthesis/repair (7%), and transport (7%) genes. The majority of genes identified at the postexposure time points were from the protein (17%) and DNA (7%) synthesis categories. In subsequent studies, three genes (CDR1, CDR2, and ERG11) were examined in greater detail (more concentration and time points) following fluconazole exposure in vitro and in vivo. Expression levels from the in vitro and in vivo studies were congruent. CDR1 and CDR2 transcripts were reduced during in vitro fluconazole exposure and during supra-MIC exposure in vivo. However, in the postexposure period, the mRNA abundance of both pumps increased. ERG11 expression increased during exposure and fell in the postexposure period. The expression of the three genes responded in a dose-dependent manner. In sum, the microarray data obtained during and following fluconazole exposure identified genes both known and unknown to be affected by this drug class. The expanded in vitro and in vivo expression data set underscores the importance of considering the time course of exposure in pharmacogenomic investigations.

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Function Analysis of MBF1, a Factor Involved in the Response to Amino Acid Starvation and Virulence in Candida albicans

Frontiers in Fungal Biology ◽

10.3389/ffunb.2021.658899 ◽

2021 ◽

Vol 2 ◽

Author(s):

Sara Amorim-Vaz ◽

Alix T. Coste ◽

Van Du T. Tran ◽

Marco Pagni ◽

Dominique Sanglard

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Amino Acid ◽

Fungal Pathogens ◽

Galleria Mellonella ◽

Function Analysis ◽

Amino Acid Starvation ◽

Infection Model ◽

The Impact

Candida albicans is a commensal of human mucosae, but also one of the most common fungal pathogens of humans. Systemic infections caused by this fungus, mostly affecting immunocompromised patients, are associated to fatality rates as high as 50% despite the available treatments. In order to improve this situation, it is necessary to fully understand how C. albicans is able to cause disease and how it copes with the host defenses. Our previous studies have revealed the importance of the C. albicans gene MBF1 in virulence and ability to colonize internal organs of mammalian and insect hosts. MBF1 encodes a putative transcriptional regulator, and as such it likely has an impact in the regulation of C. albicans gene expression during host infection. Here, recent advances in RNA-seq technologies were used to obtain a detailed analysis of the impact of MBF1 on C. albicans gene expression both in vitro and during infection. MBF1 was involved in the regulation of several genes with a role in glycolysis and response to stress, particularly to nutritional stress. We also investigated whether an interaction existed between MBF1 and GCN4, a master regulator of response to starvation, and found that both genes were needed for resistance to amino acid starvation, suggesting some level of interaction between the two. Reinforcing this idea, we showed that the proteins encoded by both genes could interact. Consistent with the role of MBF1 in virulence, we also established that GCN4 was necessary for virulence in the mouse model of systemic infection as well as in the Galleria mellonella infection model.

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