Starvation survival and recovery in serum of Candida albicans compared with Enterococcus faecalis

Morphology of Penicillium rubens Biofilms Formed in Space

Fungi biofilms have been found growing on spacecraft surfaces such as windows, piping, cables, etc. The contamination of these surfaces with fungi, although undesirable, is highly difficult to avoid. While several biofilm forming species, including Penicillium rubens, have been identified in spacecraft, the effect of microgravity on fungal biofilm formation is unknown. This study sent seven material surfaces (Stainless Steel 316, Aluminum Alloy, Titanium Alloy, Carbon Fiber, Quartz, Silicone, and Nanograss) inoculated with spores of P. rubens to the International Space Station and allowed biofilms to form for 10, 15, and 20 days to understand the effects of microgravity on biofilm morphology and growth. In general, microgravity did not induce changes in the shape of biofilms, nor did it affect growth in terms of biomass, thickness, and surface area coverage. However, microgravity increased or decreased biofilm formation in some cases, and this was incubation-time- and material-dependent. Nanograss was the material with significantly less biofilm formation, both in microgravity and on Earth, and it could potentially be interfering with hyphal adhesion and/or spore germination. Additionally, a decrease in biofilm formation at 20 days, potentially due to nutrient depletion, was seen in some space and Earth samples and was material-dependent.

Environmental reservoirs of the drug-resistant pathogenic yeast Candida auris

Candia auris is an emerging human pathogenic yeast; yet, despite phenotypic attributes and genomic evidence suggesting that it probably emerged from a natural reservoir, we know nothing about the environmental phase of its life cycle and the transmission pathways associated with it. The thermotolerant characteristics of C. auris have been hypothesised to be an environmental adaptation to increasing temperatures due to global warming (which may have facilitated its ability to tolerate the mammalian thermal barrier that is considered a protective strategy for humans against colonisation by environmental fungi with pathogenic potential). Thus, C. auris may be the first human pathogenic fungus to have emerged as a result of climate change. In addition, the release of antifungal chemicals, such as azoles, into the environment (from both pharmaceutical and agricultural sources) is likely to be responsible for the environmental enrichment of resistant strains of C. auris; however, the survival and dissemination of C. auris in the natural environment is poorly understood. In this paper, we critically review the possible pathways through which C. auris can be introduced into the environment and evaluate the environmental characteristics that can influence its persistence and transmission in natural environments. Identifying potential environmental niches and reservoirs of C. auris and understanding its emergence against a backdrop of climate change and environmental pollution will be crucial for the development of effective epidemiological and environmental management responses.

Cathelicidin LL-37 in Health and Diseases of the Oral Cavity

The mechanisms for maintaining oral cavity homeostasis are subject to the constant influence of many environmental factors, including various chemicals and microorganisms. Most of them act directly on the oral mucosa, which is the mechanical and immune barrier of the oral cavity, and such interaction might lead to the development of various oral pathologies and systemic diseases. Two important players in maintaining oral health or developing oral pathology are the oral microbiota and various immune molecules that are involved in controlling its quantitative and qualitative composition. The LL-37 peptide is an important molecule that upon release from human cathelicidin (hCAP-18) can directly perform antimicrobial action after insertion into surface structures of microorganisms and immunomodulatory function as an agonist of different cell membrane receptors. Oral LL-37 expression is an important factor in oral homeostasis that maintains the physiological microbiota but is also involved in the development of oral dysbiosis, infectious diseases (including viral, bacterial, and fungal infections), autoimmune diseases, and oral carcinomas. This peptide has also been proposed as a marker of inflammation severity and treatment outcome.

Root canal microorganisms and their antibiotic susceptibility in patients with persistent endodontic infections, with and without clinical symptoms

Secondary/persistent infections are present in teeth with previous root canal treatment, and a great variety of anaerobic microorganisms has been observed in these infections. The antibiotics prescription is occasional; however, in some cases, it is essential, particularly when the general health condition of the patient is compromised. The aims of this study were to identify the associated microorganisms in diagnosis of persistent or secondary apical periodontitis and to evaluate the susceptibility level to the antibiotics most used. Fifteen patients with persistent or secondary apical periodontitis requiring endodontic re-treatment were included. Microbiological samples were taken from the root canals and incubated in thioglycollate under anaerobic conditions. Anaerobic CDC agar (formulated by the Center for Disease Control and Prevention) was employed as a culture medium and the microorganisms were identified using the API system. The microorganisms were subjected to antibiograms with three different antibiotics. Twenty-six microorganisms were identified, the most common genus was Enterococcus (26.8%), Streptococcus (19.22%), Aerococcus (19.1%), and Clostridium (11.4%). 48% of them were susceptible to amoxicillin, with 28% of resistance. For clavulanic acid/amoxicillin, the susceptibility occurred in 32%, with 28% of resistance; and for clindamycin, the susceptibility was present in 40%, with 52% of resistance. The most frequently detected associated microorganism for secondary infections was genus Enterococcus, which exhibited high resistance to the studied antibiotics.

Antimicrobial activity of Psidium cattleianum associated with calcium hydroxide against Enterococcus faecalis and Candida albicans: an in vitro study

OBJECTIVE

Evaluate, in vitro, the antimicrobial activity of Psidium cattleianum leaf extracts combined with calcium hydroxide against Enterococcus faecalis and Candida albicans biofilm.

MATERIALS AND METHODS

Dentin specimens obtained from extracted bovine incisors were infected during 14 days with E. faecalis ATCC 29212 and C. albicans ATCC 10231. The specimens were filled with calcium hydroxide pastes prepared with the following vehicles: Psidium cattleianum ethanolic, Psidium cattleianum propylene glycolic, distilled water, and saline as control. After 24 h, 3, 7, and 14 days, the canals were irrigated with sterile saline and dried. Dentin samples were collected from the canals with burs of increasing diameters. To determine the number of colony-forming units (CFU), samples were inoculated onto BHI agar supplemented with yeast extract (0.5%), at 37 °C, for 48 h, in CO₂ enriched atmosphere. Comparisons among the groups for the variation factors were performed by ANOVA and Tukey's test.

RESULTS

Ethanolic and propylene glycolic extracts showed significantly higher antimicrobial activity against E. faecalis (p < 0.01) when compared with distilled water. The ethanolic extract exhibited in 24 h the same antibacterial activity that propylene glycolic extract and distilled water after 7 and 14 days. For C. albicans, all were effective in reducing the number of CFU at all periods.

CONCLUSION

The P. cattleianum ethanolic extract presented the fastest and highest antimicrobial activity against E. faecalis, significantly reducing the microbial load in 24 h. All medications were effective against C. albicans.

CLINICAL RELEVANCE

The antibacterial potential of P. cattleianum and its biological compatibility associated with calcium hydroxide indicate promising applications in the field of dentistry.

Enterococcus faecalis immunoregulates osteoclastogenesis of macrophages

Persistent apical periodontitis (PAP) is characterized by refractory inflammation and progressive bone destruction. Enterococcus faecalis infection is considered an important etiological factor for the development of PAP, although the exact mechanisms remain unknown. This study aimed at investigating the role of E. faecalis in cell proliferation, inflammatory reactions and osteoclast differentiation of macrophages using an in vitro infection model of osteoclast precursor RAW264.7 cells. A cell viability assay of cultured RAW264.7 cells exposed to live E. faecalis at a multiplicity of infection of 100 for 2h, indicated that the infection exhibited no cytotoxic effect. Transmission electron microscopy images revealed no apoptotic changes but a rise of metabolic activity and phagocytic features in the infected RAW264.7 cells. Confocal laser scanning microscopic and flow cytometric analysis indicated that the phagocytosis of RAW264.7 cells was activated by E. faecalis infection. Furthermore, quantitative real-time PCR assays demonstrated that the expression of inflammatory cytokines was remarkably elevated in infected RAW264.7 cells. Differentiation of infected RAW264.7 cells into osteoclasts was remarkably attenuated, and expression of osteoclast marker genes as well as fusogenic genes significantly dropped. In summary, E. faecalis appears to attenuate osteoclastic differentiation of RAW264.7 precursor cells, rather stimulates them to function as macrophages.

Candida albicans survival and biofilm formation under starvation conditions

AIM

To investigate the survival and biofilm formation capacity of Candida albicans in starvation and under anaerobic conditions.

METHODOLOGY

Candida albicans growth and survival were monitored in vitro for up to 8 months. Fungal suspensions from late exponential, stationary and starvation phases were incubated on human dentine, polystyrene and glass slides. Scanning electron microscopy (SEM) was used to observe the process of biofilm formation. 2,3-bis(2-Methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxyanilide inner salt (XTT) reduction assay was performed to quantify the biofilm formation capability, and confocal laser scanning microscopy (CLSM) was used to study and make semi-quantitative comparisons of the ultrastructure of biofilms formed on human dentine. 'XTT bioactivity' and 'COMSTAT results' were analysed by two-way analysis of variance (ANOVA) and one-way ANOVA, respectively.

RESULTS

Candida albicans survived for over six months. SEM demonstrated that starving C. albicans produced mature biofilms on different substrata. C. albicans of the same growth phase incubated on human dentine displayed significantly higher biofilm formation capability than on polystyrene or glass slides (P < 0.05). Biofilm formation capability by starving cells was significantly lower than that in exponential or stationary phases (P < 0.05). CLSM revealed that biofilms formed by starvation-phase cells were less complex, had a higher roughness coefficient and surface/volume ratio (P < 0.05).

CONCLUSIONS

Candida albicans cells can survive and form biofilms in anaerobic and nutrient-limited conditions and may pose a treatment challenge.

Starvation survival of Candida albicans in various water microcosms

Candida is a major Human pathogen causing a variety of infections and can survive for extended period of time in aquatic environment including marine and fresh water. In this study we compared a colorimetric XTT assay to colony forming units (CFU) count to evaluate the survival potential of Candida albicans incubated in water microcosms. Our results showed that cells maintain cultivability within a long period followed by a decline in cultivability and a drop of plate counts to less than 20 cell ml(-1) after 150 days in tap water, 190 days in rain water and 200 days in seawater. In addition we noted that 10% of cells viability was reached after 150 days in seawater, 180 days in rain water and 210 days in tap water. Molecular method confirms the persistence of C. albicans cells in water during long time starvation period.