Staphylococcus aureus Synergized with Candida albicans to Increase the Pathogenesis and Drug Resistance in Cutaneous Abscess and Peritonitis Murine Models

A customizable and defined medium supporting culturing of Candida albicans, Staphylococcus aureus, and human oral epithelial cells

Candida albicans, an opportunistic oral pathogen, synergizes with Staphylococcus aureus, allowing bacteria to co-invade and systemically disseminate within the host. Studying human-microbe interactions creates the need for a universal culture medium that supports fungal, bacterial, and human cell culturing, while allowing sensitive analytical approaches such as OMICs and chromatography techniques. In this study, we established a fully defined, customizable adaptation of Dulbecco's modified Eagle medium (DMEM), allowing multi-kingdom culturing of S. aureus, C. albicans, and human oral cell lines, whereas minimal version of DMEM (mDMEM) did not support growth of S. aureus, and neither did supplementation with dextrose, MEM non-essential amino acids, pyruvate, and Glutamax. This new medium composition, designated as "mDMEM-DMP," promoted growth of all tested S. aureus strains. Addition of 25 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) further improved growth, while higher concentrations did not improve growth any further. Higher concentrations of HEPES did result in prolonged stabilization of medium pH. mDMEM-DMP promoted (hyphal) C. albicans monoculturing and co-culturing on both solid and semi-solid surfaces. In contrast to S. aureus, addition of HEPES reduced C. albicans maximum culture optical density (OD). Finally, only buffered mDMEM-DMP (100 mM HEPES) was successful in maintaining the metabolic activity of human oral Ca9-22 and HO1N1 cell lines for 24 hours. Altogether, our findings show that mDMEM-DMP is a versatile and potent culture medium for both microbial and human cell culturing, providing a customizable platform to study human as well as microbial molecular physiology and putative interactions.

IMPORTANCE

Interaction between microbes and the host are in the center of interest both in disease and in health. In order to study the interactions between microbes of different kingdoms and the host, alternative media are required. Synthetic media are useful as they allow addition of specific components. In addition, well-defined media are required if high-resolution analyses such as metabolomics and proteomics are desired. We describe the development of a synthetic medium to study the interactions between C. albicans, S. aureus, and human oral epithelial cells. Our findings show that mDMEM-DMP is a versatile and potent culture medium for both microbial and human cell culturing, providing a customizable platform to study human as well as microbial molecular physiology and putative interactions.

Staphylococcus aureus wraps around Candida albicans and synergistically escapes from Neutrophil extracellular traps

Background

NETs, a unique neutrophil immune mechanism, are vital in defending against microbial invasions. Understanding the mechanisms of co-infection by Candida albicans and Staphylococcus aureus, which often leads to higher mortality and poorer prognosis, is crucial for studying infection progression.

Methods

In our study, we established a mouse model of subcutaneous infection to characterize the inflammation induced by co-infection. By purifying and extracting NETs to interact with microorganisms, we delve into the differences in their interactions with various microbial species. Additionally, we investigated the differences in NETs production by neutrophils in response to single or mixed microorganisms through the interaction between neutrophils and these microorganisms. Furthermore, we analyzed the gene expression differences during co-infection using transcriptomics.

Results

In vivo, C. albicans infections tend to aggregate, while S. aureus infections are more diffuse. In cases of co-infection, S. aureus adheres to and wraps C. albicans. NETs exhibit strong killing capability against C. albicans but weaker efficacy against S. aureus. When NETs interact with mixed microorganisms, they preferentially target and kill the outer layer of S. aureus. In the early stages, neutrophils primarily rely on phagocytosis to kill S. aureus, but as the bacteria accumulate, they stimulate neutrophils to produce NETs. Interestingly, in the presence of neutrophils, S. aureus promotes the proliferation and hyphal growth of C. albicans.

Conclusion

Our research has showed substantial differences in the progression of co-infections compared to single-microbial infections, thereby providing scientific evidence for NETs as potential therapeutic targets in the treatment of co-infections.

Molecular Analysis of Volatile Metabolites Synthesized by Candida albicans and Staphylococcus aureus in In Vitro Cultures and Bronchoalveolar Lavage Specimens Reflecting Single- or Duo-Factor Pneumonia

Current microbiological methods for pneumonia diagnosis require invasive specimen collection and time-consuming analytical procedures. There is a need for less invasive and faster methods to detect lower respiratory tract infections. The analysis of volatile metabolites excreted by pathogenic microorganisms provides the basis for developing such a method. Given the synergistic role of Candida albicans in increasing the virulence of pathogenic bacteria causing pneumonia and the cross-kingdom metabolic interactions between microorganisms, we compare the emission of volatiles from Candida albicans yeasts and the bacteria Staphylococcus aureus using single and mixed co-cultures and apply that knowledge to human in vivo investigations. Gas chromatography-mass spectrometry (GC-MS) analysis resulted in the identification of sixty-eight volatiles that were found to have significantly different levels in cultures compared to reference medium samples. Certain volatiles were found in co-cultures that mainly originated from C. albicans metabolism (e.g., isobutyl acetate), whereas other volatiles primarily came from S. aureus (e.g., ethyl 2-methylbutyrate). Isopentyl valerate reflects synergic interactions of both microbes, as its level in co-cultures was found to be approximately three times higher than the sum of its amounts in monocultures. Hydrophilic-lipophilic-balanced (HLB) coated meshes for thin-film microextraction (TFME) were used to preconcentrate volatiles directly from bronchoalveolar lavage (BAL) specimens collected from patients suffering from ventilation-associated pneumonia (VAP), which was caused explicitly by C. albicans and S. aureus. GC-MS analyses confirmed the existence of in vitro-elucidated microbial VOCs in human specimens. Significant differences in BAL-extracted amounts respective to the pathogen-causing pneumonia were found. The model in vitro experiments provided evidence that cross-kingdom interactions between pathogenic microorganisms affect the synthesis of volatile compounds. The TFME meshes coated with HLB particles proved to be suitable for extracting VOCs from human material, enabling the translation of in vitro experiments on the microbial volatilome to the in vivo situation involving infected patients. This indicates the direction that should be taken for further clinical studies on VAP diagnosis based on volatile analysis.

Mineral trioxide aggregate in membrane form as a barrier membrane in guided bone regeneration

Background/purpose

In the field of conservative dentistry and endodontics, mineral trioxide aggregate (MTA), commonly used, possesses advantages such as biocompatibility, antimicrobial properties and osteogenic potential. This study investigated the feasibility of utilizing membrane form mineral trioxide aggregate (MTA) as a barrier membrane in guided bone regeneration (GBR) procedures.

Materials and methods

Membranes were electrospun from three different formulations: 15 w/v% Polycaprolactone (PCL), 13 w/v% PCL + 2 w/v% MTA (2MTA), and 11 w/v% PCL + 4 w/v% MTA (4MTA). Physicochemical and mechanical properties of the electrospun membrane were compared, encompassing parameters such as surface morphology, fiber diameter distribution, chemical composition, phase identification, tensile stress, pH variation, and water contact angle. Moreover, the antimicrobial properties against of the electrospun membranes were assessed through direct exposure to streptococcus aureus (S. aureus) and candida albicans (C. albicans). Additionally, on the 7th day, biocompatibility and cell attachment were investigated with respect to L929 (fibroblast) and MC3T3 (pre-osteoblast) cells. Inhibition of L929 cell infiltration and the expression of osteogenic related genes including osteocalcin (OCN), alkaline phosphatase (ALP), and runt related transcription factor 2 (RUNX2) in MC3T3 cells on 7th and 14th days were also investigated.

Results

PCL, 2MTA, and 4MTA exhibited no statistically differences in fiber diameter distribution and tensile stress. However, as the MTA content increased, wettability and pH also increased. Due to the elevated pH, 4MTA demonstrated the lowest viability S.aureus and C.albicans. All membranes were highly biocompatibility and promoted cell attachment, while effectively preventing L929 cell infiltration. Lastly 4MTA showed increase in OCN, ALP, and RUNX2 expression on both 7th and 14th day.

Conclusion

The membrane form MTA possessed characteristics essential for a novel barrier membrane.

Candida albicans and Candida glabrata: global priority pathogens

SUMMARYA significant increase in the incidence of Candida-mediated infections has been observed in the last decade, mainly due to rising numbers of susceptible individuals. Recently, the World Health Organization published its first fungal pathogen priority list, with Candida species listed in medium, high, and critical priority categories. This review is a synthesis of information and recent advances in our understanding of two of these species-Candida albicans and Candida glabrata. Of these, C. albicans is the most common cause of candidemia around the world and is categorized as a critical priority pathogen. C. glabrata is considered a high-priority pathogen and has become an increasingly important cause of candidemia in recent years. It is now the second most common causative agent of candidemia in many geographical regions. Despite their differences and phylogenetic divergence, they are successful as pathogens and commensals of humans. Both species can cause a broad variety of infections, ranging from superficial to potentially lethal systemic infections. While they share similarities in certain infection strategies, including tissue adhesion and invasion, they differ significantly in key aspects of their biology, interaction with immune cells, host damage strategies, and metabolic adaptations. Here we provide insights on key aspects of their biology, epidemiology, commensal and pathogenic lifestyles, interactions with the immune system, and antifungal resistance.

Antimicrobials: An update on new strategies to diversify treatment for bacterial infections

Ninety-five years after Fleming's discovery of penicillin, a bounty of antibiotic compounds have been discovered, modified, or synthesised. Diversification of target sites, improved stability and altered activity spectra have enabled continued antibiotic efficacy, but overwhelming reliance and misuse has fuelled the global spread of antimicrobial resistance (AMR). An estimated 1.27 million deaths were attributable to antibiotic resistant bacteria in 2019, representing a major threat to modern medicine. Although antibiotics remain at the heart of strategies for treatment and control of bacterial diseases, the threat of AMR has reached catastrophic proportions urgently calling for fresh innovation. The last decade has been peppered with ground-breaking developments in genome sequencing, high throughput screening technologies and machine learning. These advances have opened new doors for bioprospecting for novel antimicrobials. They have also enabled more thorough exploration of complex and polymicrobial infections and interactions with the healthy microbiome. Using models of infection that more closely resemble the infection state in vivo, we are now beginning to measure the impacts of antimicrobial therapy on host/microbiota/pathogen interactions. However new approaches are needed for developing and standardising appropriate methods to measure efficacy of novel antimicrobial combinations in these contexts. A battery of promising new antimicrobials is now in various stages of development including co-administered inhibitors, phages, nanoparticles, immunotherapy, anti-biofilm and anti-virulence agents. These novel therapeutics need multidisciplinary collaboration and new ways of thinking to bring them into large scale clinical use.

Secretory IgA reduced the ergosterol contents of Candida albicans to repress its hyphal growth and virulence

Candida albicans, one of the most prevalent conditional pathogenic fungi, can cause local superficial infections and lethal systemic infections, especially in the immunocompromised population. Secretory immunoglobulin A (sIgA) is an important immune protein regulating the pathogenicity of C. albicans. However, the actions and mechanisms that sIgA exerts directly against C. albicans are still unclear. Here, we investigated that sIgA directs against C. albicans hyphal growth and virulence to oral epithelial cells. Our results indicated that sIgA significantly inhibited C. albicans hyphal growth, adhesion, and damage to oral epithelial cells compared with IgG. According to the transcriptome and RT-PCR analysis, sIgA significantly affected the ergosterol biosynthesis pathway. Furthermore, sIgA significantly reduced the ergosterol levels, while the addition of exogenous ergosterol restored C. albicans hyphal growth and adhesion to oral epithelial cells, indicating that sIgA suppressed the growth of hyphae and the pathogenicity of C. albicans by reducing its ergosterol levels. By employing the key genes mutants (erg11Δ/Δ, erg3Δ/Δ, and erg3Δ/Δ erg11Δ/Δ) from the ergosterol pathway, sIgA lost the hyphal inhibition on these mutants, while sIgA also reduced the inhibitory effects of erg11Δ/Δ and erg3Δ/Δ and lost the inhibition of erg3Δ/Δ erg11Δ/Δ on the adhesion to oral epithelial cells, further proving the hyphal repression of sIgA through the ergosterol pathway. We demonstrated for the first time that sIgA inhibited C. albicans hyphal development and virulence by affecting ergosterol biosynthesis and suggest that ergosterol is a crucial regulator of C. albicans-host cell interactions. KEY POINTS: • sIgA repressed C. albicans hyphal growth • sIgA inhibited C. albicans virulence to host cells • sIgA affected C. albicans hyphae and virulence by reducing its ergosterol levels.

Inhibition of Biofilm Formation in Cutibacterium acnes, Staphylococcus aureus, and Candida albicans by the Phytopigment Shikonin

Skin microbiota, such as acne-related Cutibacterium acnes, Staphylococcus aureus, and fungal Candida albicans, can form polymicrobial biofilms with greater antimicrobial tolerance to traditional antimicrobial agents and host immune systems. In this study, the phytopigment shikonin was investigated against single-species and multispecies biofilms under aerobic and anaerobic conditions. Minimum inhibitory concentrations of shikonin were 10 µg/mL against C. acnes, S. aureus, and C. albicans, and at 1-5 µg/mL, shikonin efficiently inhibited single biofilm formation and multispecies biofilm development by these three microbes. Shikonin increased porphyrin production in C. acnes, inhibited cell aggregation and hyphal formation by C. albicans, decreased lipase production, and increased hydrophilicity in S. aureus. In addition, shikonin at 5 or 10 µg/mL repressed the transcription of various biofilm-related genes and virulence-related genes in C. acnes and downregulated the gene expression levels of the quorum-sensing agrA and RNAIII, α-hemolysin hla, and nuclease nuc1 in S. aureus, supporting biofilm inhibition. In addition, shikonin prevented multispecies biofilm development on porcine skin, and the antimicrobial efficacy of shikonin was recapitulated in a mouse infection model, in which it promoted skin regeneration. The study shows that shikonin inhibits multispecies biofilm development by acne-related skin microbes and might be useful for controlling bacterial infections.

Co-colonization of methicillin-resistant Staphylococcus aureus and Candida spp. in children with malignancies

This study aimed to evaluate the interaction between methicillin-resistant Staphylococcus aureus(MRSA) and Candida spp. in the oral cavity of children with malignancies under chemotherapy. We evaluated the expression level of Als3p and mecA in Candida spp. and MRSA strains in both single colonization and co-colonization condition. Oral and nasal samples were collected by dry sponge swabs in 10 ml of sterile phosphate-buffered saline. The MRSA and Candida spp. was confirmed using the PCR method and mecA and Als3p genes, respectively. The SYBR Green-based quantitative real-time PCR was used to evaluate the relative expression levels of mecA and Als3p genes in MRSA and Candida spp., respectively. The frequency of S. aureus in oral-only and nasal-only swab samples were 14.1% (n = 24/170). 58.3% (n = 14/24) and 29.2% (n = 7/24) of S. aureus isolated from oral and nasal samples were MRSA, respectively. Among Candida species, C. albicans (n = 28/170; 16.5%) had the highest frequency. The oral co-colonization of MRSA and Candida spp. was detected in 4.7% (n = 8/170) patients. The overall average of gene expression levels among all Candida spp. and MRSA isolates indicated that the mecA and Als3p genes expression increased six and two times in co-colonization conditions compared to single colonization conditions, respectively. Our findings revealed the importance of polymicrobial infection in clinical settings and stated that it is possible that Candida spp. facilitates the infection of S. aureus and can lead to systemic infection in co-colonized patients.

Antimicrobial potential of a biosurfactant gel for the prevention of mixed biofilms formed by fluconazole-resistant C. albicans and methicillin-resistant S. aureus in catheters

Dual-species biofilms formed by Candida albicans and Staphylococcus aureus have high virulence and drug resistance. In this context, biosurfactants produced by Pseudomonas aeruginosa have been widely studied, of which a new derivative (RLmix_Arg) stands out for possible application in formulations. The objective of this study was to evaluate the antibiofilm activity of RLmix_Arg, both alone and incorporated in a gel prepared with Pluronic F-127, against dual-species biofilms of fluconazole-resistant C. albicans (FRCA) and methicillin-resistant S. aureus (MRSA) in impregnated catheters. Broth microdilution tests, MTT reduction assays of mature biofilms, impregnation of RLmix_Arg and its gel in peripheral venous catheters, durability tests and scanning electron microscopy (SEM) were performed. RLmix_Arg showed antimicrobial activity against Candida spp. and S. aureus, by reducing the cell viability of mixed biofilms of FRCA and MRSA, and preventing their formation in a peripheral venous catheter. The incorporation of this biosurfactant in the Pluronic F-127 gel considerably enhanced its antibiofilm activity. Thus, RLmix_Arg has potential application in gels for impregnation in peripheral venous catheters, helping to prevent development of dual-species biofilms of FRCA and MRSA.

Time-lapse mesoscopy of Candida albicans and Staphylococcus aureus dual-species biofilms reveals a structural role for the hyphae of C. albicans in biofilm formation

Polymicrobial infection with Candida albicans and Staphylococcus aureus may result in a concomitant increase in virulence and resistance to antimicrobial drugs. This enhanced pathogenicity phenotype is mediated by numerous factors, including metabolic processes and direct interaction of S. aureus with C. albicans hyphae. The overall structure of biofilms is known to contribute to their recalcitrance to treatment, although the dynamics of direct interaction between species and how it contributes to pathogenicity is poorly understood. To address this, a novel time-lapse mesoscopic optical imaging method was developed to enable the formation of C. albicans/S. aureus whole dual-species biofilms to be followed. It was found that yeast-form or hyphal-form C. albicans in the biofilm founder population profoundly affects the structure of the biofilm as it matures. Different sub-populations of C. albicans and S. aureus arise within each biofilm as a result of the different C. albicans morphotypes, resulting in distinct sub-regions. These data reveal that C. albicans cell morphology is pivotal in the development of global biofilm architecture and the emergence of colony macrostructures and may temporally influence synergy in infection.

Surface adherence and vacuolar internalization of bacterial pathogens to the Candida spp. cells: Mechanism of persistence and propagation

BACKGROUND

The co-existence of Candida albicans with the bacteria in the host tissues and organs displays interactions at competitive, antagonistic, and synergistic levels. Several pathogenic bacteria take advantage of such types of interaction for their survival and proliferation. The chemical interaction involves the signaling molecules produced by the bacteria or Candida spp., whereas the physical attachment occurs by involving the surface proteins of the bacteria and Candida. In addition, bacterial pathogens have emerged to internalize inside the C. albicans vacuole, which is one of the inherent properties of the endosymbiotic relationship between the bacteria and the eukaryotic host.

AIM OF REVIEW

The interaction occurring by the involvement of surface protein from diverse bacterial species with Candida species has been discussed in detail in this paper. An in silico molecular docking study was performed between the surface proteins of different bacterial species and Als3P of C. albicans to explain the molecular mechanism involved in the Als3P-dependent interaction. Furthermore, in order to understand the specificity of C. albicans interaction with Als3P, the evolutionary relatedness of several bacterial surface proteins has been investigated. Furthermore, the environmental factors that influence bacterial pathogen internalization into the Candida vacuole have been addressed. Moreover, the review presented future perspectives for disrupting the cross-kingdom interaction and eradicating the endosymbiotic bacterial pathogens.

KEY SCIENTIFIC CONCEPTS OF REVIEW

With the involvement of cross-kingdom interactions and endosymbiotic relationships, the bacterial pathogens escape from the environmental stresses and the antimicrobial activity of the host immune system. Thus, the study of interactions between Candida and bacterial pathogens is of high clinical significance.

Antibiofilm Activity of Invasive Plants against Candida albicans: Focus on Baccharis halimifolia Essential Oil and Its Compounds

The extracts of five invasive plants were investigated for antifungal and antibiofilm activities against Candida albicans, C. glabrata, C. krusei, and C. parapsilosis. The antifungal activity was evaluated using the microdilution assay and the antibiofilm effect by measurement of the metabolic activity. Ethanol and ethanol-water extracts of Reynoutria japonica leaves inhibited 50 % of planktonic cells at 250 μg mL-1 and 15.6 μg mL-1 , respectively. Ethanol and ethanol-water extracts of Baccharis halimifolia inhibited >75 % of the mature biofilm of C. albicans at 500 μg mL-1 . The essential oil (EO) of B. halimifolia leaves was the most active (50 % inhibition (IC50 ) at 4 and 74 μg mL-1 against the maturation phase and 24 h old-biofilms of C. albicans, respectively). Oxygenated sesquiterpenes were the primary contents in this EO (62.02 %), with β-caryophyllene oxide as the major component (37 %). Aromadendrene oxide-(2), β-caryophyllene oxide, and (±)-β-pinene displayed significant activities against the maturation phase (IC50 =9-310 μ mol l-1 ) and preformed 24 h-biofilm (IC50 =38-630 μ mol l-1 ) of C. albicans with very low cytotoxicity for the first two compounds. C. albicans remained the most susceptible species to this EO and its components. This study highlighted for the first time the antibiofilm potential of B. halimifolia, its EO and some of its components.

Novel antimicrobial iodo-dihydro-pyrrole-2-one compounds

Aim: A series of new hybrid molecules with two iodine atoms on the sides were synthesized. Methods: A one-pot, two-component method with trifluoroacetic acid as an effective catalyst to obtain dihydro-pyrrol-2-one compounds was developed. Short reaction times, a cheap catalyst, high yields and clean work-up are benefits of this method. Results: The chemical structures of the newly synthesized compounds were verified through spectroscopic techniques. Their antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans was tested in vitro. Conclusion: NC- and OH- radicals confer broad-spectrum antimicrobial activity, including against Gram-positive and Gram-negative bacteria and yeasts. Compounds 3g >7 and >9 were most active on the two bacterial species, while 3l >9 and >3i were most active against the fungal strain.

Staphylococcus aureus in Polymicrobial Skinand Soft Tissue Infections: Impact of Inter-Species Interactionsin Disease Outcome

Polymicrobial biofilms provide a complex environment where co-infecting microorganisms can behave antagonistically, additively, or synergistically to alter the disease outcome compared to monomicrobial infections. Staphylococcus aureus skin and soft tissue infections (Sa-SSTIs) are frequently reported in healthcare and community settings, and they can also involve other bacterial and fungal microorganisms. This polymicrobial aetiology is usually found in chronic wounds, such as diabetic foot ulcers, pressure ulcers, and burn wounds, where the establishment of multi-species biofilms in chronic wounds has been extensively described. This review article explores the recent updates on the microorganisms commonly found together with S. aureus in SSTIs, such as Pseudomonas aeruginosa, Escherichia coli, Enterococcus spp., Acinetobacter baumannii, and Candida albicans, among others. The molecular mechanisms behind these polymicrobial interactions in the context of infected wounds and their impact on pathogenesis and antimicrobial susceptibility are also revised.

Inhibition of Mixed Biofilms of Candida albicans and Staphylococcus aureus by β-Caryophyllene-Gold Nanoparticles

Polymicrobial biofilms, consisting of fungal and bacterial pathogens, often contribute to the failure of antimicrobial treatment. The growing resistance of pathogenic polymicrobial biofilms to antibiotics has led to the development of alternative strategies to combat polymicrobial diseases. To this end, nanoparticles synthesized using natural molecules have received significant attention for disease treatment. Here, gold nanoparticles (AuNPs) were synthesized using β-caryophyllene, a bioactive compound isolated from various plant species. The shape, size, and zeta potential of the synthesized β-c-AuNPs were found to be non-spherical, 17.6 ± 1.2 nm, and -31.76 ± 0.73 mV, respectively. A mixed biofilm of Candida albicans and Staphylococcus aureus was used to test the efficacy of the synthesized β-c-AuNPs. The results revealed a concentration-dependent inhibition of the initial stages of formation of single-species as well as mixed biofilms. Furthermore, β-c-AuNPs also eliminated mature biofilms. Therefore, using β-c-AuNPs to inhibit biofilm and eradicate bacterial-fungal mixed biofilms represents a promising therapeutic approach for controlling polymicrobial infections.

Alpha-Hemolysin from Staphylococcus aureus Obstructs Yeast-Hyphae Switching and Diminishes Pathogenicity in Candida albicans

The use of antibiotics can disrupt the body's natural balance and increase the susteptibility of patients towards fungal infections. Candida albicans is a dimorphic opportunistic fungal pathogen with niches similar to those of bacteria. Our aim was to study the interaction between this pathogen and bacteria to facilitate the control of C. albicans infection. Alpha-hemolysin (Hla), a protein secreted from Staphylococcus aureus, causes cell wall damage and impedes the yeast-hyphae transition in C. albicans. Mechanistically, Hla stimulation triggered the formation of reactive oxygen species that damaged the cell wall and mitochondria of C. albicans. The cell cycle was arrested in the G0/G1 phase, CDC42 was downregulated, and Ywp1 was upregulated, disrupting yeast hyphae switching. Subsequently, hyphae development was inhibited. In mouse models, C. albicans pretreated with Hla reduced the C. albicans burden in skin and vaginal mucosal infections, suggesting that S. aureus Hla can inhibit hyphal development and reduce the pathogenicity of candidiasis in vivo.

Hitchhiking motility of Staphylococcus aureus involves the interaction between its wall teichoic acids and lipopolysaccharide of Pseudomonas aeruginosa

Staphylococcus aureus, which lacks pili and flagella, is nonmotile. However, it hitchhikes motile bacteria, such as Pseudomonas aeruginosa, to migrate in the environment. This study demonstrated that the hitchhiking motility of S. aureus SA113 was reduced after the tagO, which encodes an enzyme for wall teichoic acids (WTA) synthesis, was deleted. The hitchhiking motility was restored after the mutation was complemented by transforming a plasmid expressing TagO into the mutant. We also showed that adding purified lipopolysaccharide (LPS) to a culture that contains S. aureus SA113 and P. aeruginosa PAO1, reduced the movement of S. aureus, showing that WTA and LPS are involved in the hitchhiking motility of S. aureus. This study also found that P. aeruginosa promoted the movement of S. aureus in the digestive tract of Caenorhabditis elegans and in mice. In conclusion, this study reveals how S. aureus hitchhikes P. aeruginosa for translocation in an ecosystem. The results from this study improve our understanding on how a nonmotile pathogen moves in the environment and spreads in animals.

Pediatric Candida Bloodstream Infections Complicated with Mixed and Subsequent Bacteremia: The Clinical Characteristics and Impacts on Outcomes

Background: Pediatricians face a therapeutic challenge when patients with Candida bloodstream infections (BSIs) simultaneously have positive bacterial culture. We aim to characterize the clinical characteristics of pediatric Candida BSIs complicated with mixed bacteremia and subsequent bacterial infections, risk factors and impacts on outcomes. Methods: All episodes of pediatric Candida BSIs between 2005 and 2020 from a medical center in Taiwan were reviewed. Mixed Candida/bacterial BSIs were defined as isolation of a bacterial pathogen from blood cultures obtained within 48 h before or after the onset of Candida BSI. The clinical features and impacts of mixed Candida/bacterial BSIs were investigated. Results: During the study period, 320 patients with a total of 365 episodes of Candida BSIs were identified and analyzed. Mixed Candida/bacterial BSIs were 35 episodes (9.6%). No significant difference was found between mixed Candida/bacterial BSIs and monomicrobial Candida BSIs in terms of patient demographics, Candida species distributions, most chronic comorbidities or risk factors. Patients with mixed Candida/bacterial BSIs were associated with a significantly higher risk of subsequent bacteremia (51.4% vs. 21.2%, p < 0.001) and a relatively higher candidemia-attributable mortality rate (37.2% vs. 22.4%, p = 0.061) than those with monomicrobial Candida BSIs. Mixed Candida/bacterial BSIs were not an independent risk factor of treatment failure or final mortality according to multivariate logistic regression analyses. Conclusions: The clinical significance of mixed Candida/bacterial BSIs in children included a longer duration of septic symptoms, significantly higher likelihood to have subsequent bacteremia, and relatively higher risk of candidemia attributable mortality.

Lycosin-II Exhibits Antifungal Activity and Inhibits Dual-Species Biofilm by Candida albicans and Staphylococcus aureus

The increase and dissemination of antimicrobial resistance is a global public health issue. To address this, new antimicrobial agents have been developed. Antimicrobial peptides (AMPs) exhibit a wide range of antimicrobial activities against pathogens, including bacteria and fungi. Lycosin-II, isolated from the venom of the spider Lycosa singoriensis, has shown antibacterial activity by disrupting membranes. However, the mode of action of Lycosin-II and its antifungal activity have not been clearly described. Therefore, we confirmed that Lycosin-II showed antifungal activity against Candida albicans (C. albicans). To investigate the mode of action, membrane-related assays were performed, including an evaluation of C. albicans membrane depolarization and membrane integrity after exposure to Lycosin-II. Our results indicated that Lycosin-II damaged the C. albicans membrane. Additionally, Lycosin-II induced oxidative stress through the generation of reactive oxygen species (ROS) in C. albicans. Moreover, Lycosin-II exhibited an inhibitory effect on dual-species biofilm formation by C. albicans and Staphylococcus aureus (S. aureus), which are the most co-isolated fungi and bacteria. These results revealed that Lycosin-II can be utilized against C. albicans and dual-species strain infections.

The Arginine Biosynthesis Pathway of Candida albicans Regulates Its Cross-Kingdom Interaction with Actinomyces viscosus to Promote Root Caries

The cross-kingdom interactions between Candida albicans and Actinomyces viscosus play critical roles in root caries. However, the key pathway by which C. albicans regulates its interactions with A. viscosus is unclear. Here, we first employed 39 volunteers with root caries and 37 caries-free volunteers, and found that the abundances of C. albicans and A. viscosus were significantly increased in the individuals with root caries and showed a strong positive correlation. Their dual-species combination synergistically promoted biofilm formation and root caries in rats. The arginine biosynthesis pathway of C. albicans was significantly upregulated in dual-species biofilms and dental plaques from another 10 root caries volunteers compared with the 10 caries-free volunteers. The exogenous addition of arginine increased the cariogenicity of the dual-species biofilm. The C. albicansARG4, a key gene from the arginine biosynthesis pathway, null mutant failed to promote dual-species biofilm formation and root caries in rats; however, the addition of arginine restored its synergistic actions with A. viscosus. Our results identified the critical roles of the C. albicans arginine biosynthesis pathway in its cross-kingdom interactions with A. viscosus for the first time and indicated that targeting this pathway was a practical way to treat root caries caused by multiple species.

IMPORTANCE Root caries is a critical problem that threatens the oral health of the elderly population. Our results identified the essential roles of the C. albicans arginine biosynthesis pathway in its cross-kingdom interactions with A. viscosus in root caries for the first time and indicated that targeting this pathway was a practical way to treat root caries caused by multiple species.

Recent Advances and Opportunities in the Study of Candida albicans Polymicrobial Biofilms

It is well known that the opportunistic pathogenic yeast, Candida albicans, can form polymicrobial biofilms with a variety of bacteria, both in vitro and in vivo, and that these polymicrobial biofilms can impact the course and management of disease. Although specific interactions are often described as either synergistic or antagonistic, this may be an oversimplification. Polymicrobial biofilms are complex two-way interacting communities, regulated by inter-domain (inter-kingdom) signaling and various molecular mechanisms. This review article will highlight advances over the last six years (2016-2021) regarding the unique biology of polymicrobial biofilms formed by C. albicans and bacteria, including regulation of their formation. In addition, some of the consequences of these interactions, such as the influence of co-existence on antimicrobial susceptibility and virulence, will be discussed. Since the aim of this knowledge is to inform possible alternative treatment options, recent studies on the discovery of novel anti-biofilm compounds will also be included. Throughout, an attempt will be made to identify ongoing challenges in this area.

Enhanced Virulence of Candida albicans by Staphylococcus aureus: Evidence in Clinical Bloodstream Infections and Infected Zebrafish Embryos

Coinfection with Candida and Staphylococcus results in higher mortality in animal studies. However, the pathogenesis and interplay between C. albicans and S. aureus in bloodstream infections (BSIs) is unclear. This study determines the clinical features and outcomes of mixed C. albicans/S. aureus (CA/SA) BSIs and biofilm formation on pathogenesis during coinfection. Demographics and outcomes for mixed BSIs and monomicrobial candidemia were compared. Compared to 115 monomicrobial C. albicans BSIs, 22 patients with mixed CA/SA BSIs exhibited a significantly higher mortality rate and shorter survival time. In vitro and in vivo biofilm analysis showed that C. albicans accounted for the main biofilm architecture, and S. aureus increased its amount. Antibiotic tolerance in S. aureus, which adhered to Candida hyphae observed by scanning electron microscope, was demonstrated by the presence of wild-type C. albicans co-biofilm. Upregulation in exotoxin genes of S. aureus was evidenced by quantitative RT-PCR when a co-biofilm was formed with C. albicans. Mixed CA/SA BSIs result in a higher mortality rate in patients and in vivo surrogate models experiments. This study demonstrates that the virulence enhancement of C. albicans and S. aureus during co-biofilm formation contributes to the high mortality rate.