Select Streptococci Can Degrade Candida Mannan To Facilitate Growth

Candida albicans impacts carbohydrate metabolism of Enterococcus faecalis in interkingdom biofilms

Objectives

This study investigated the transcriptional and physiological responses of Enterococcus faecalis, an opportunistic pathogen linked to endodontic infections, when cultivated in dual-species biofilms with Candida albicans, a yeast pathobiont found in the oral cavity.

Methods

Forty-eight-hour E. faecalis OG1RF biofilms were developed in BHI medium as mono- or dual-species with C. albicans SC5314. Biofilms were assessed for biomass, colony-forming units (CFUs), and architecture using confocal microscopy. RNA sequencing was performed on an Illumina platform. Mannose-PTS activity and glycerol quantification assays were conducted to investigate changes in carbohydrate metabolism.

Results

Transcriptomic analysis revealed 149 E. faecalis genes differentially expressed in dual-species biofilms. Genes linked to mannose-PTS and glycerol metabolism were notably upregulated. Mannose-PTS activity was significantly higher in dual-species biofilms. Mannose, as the sole carbohydrate source, increased E. faecalis CFUs and decreased C. albicans CFUs in co-culture, while glucose had no effect. As C. albicans is a glycerol net producer, glycerol levels were always higher when C. albicans was present, likely contributing to the upregulation of glycerol metabolism genes in E. faecalis when in co-cultures.

Conclusions

The presence of C. albicans alters E. faecalis gene expression and metabolism, suggesting metabolic crosstalk that may influence their pathogenicity and role in oral infections.

The oral microbiome: diversity, biogeography and human health

The human oral microbiota is highly diverse and has a complex ecology, comprising bacteria, microeukaryotes, archaea and viruses. These communities have elaborate and highly structured biogeography that shapes metabolic exchange on a local scale and results from the diverse microenvironments present in the oral cavity. The oral microbiota also interfaces with the immune system of the human host and has an important role in not only the health of the oral cavity but also systemic health. In this Review, we highlight recent advances including novel insights into the biogeography of several oral niches at the species level, as well as the ecological role of candidate phyla radiation bacteria and non-bacterial members of the oral microbiome. In addition, we summarize the relationship between the oral microbiota and the pathology of oral diseases and systemic diseases. Together, these advances move the field towards a more holistic understanding of the oral microbiota and its role in health, which in turn opens the door to the study of novel preventive and therapeutic strategies.

Interspecies Interactions within the Host: the Social Network of Group B Streptococcus

Group B Streptococcus (GBS) is a pervasive neonatal pathogen accounting for a combined half a million deaths and stillbirths annually. The most common source of fetal or neonatal GBS exposure is the maternal microbiota. GBS asymptomatically colonizes the gastrointestinal and vaginal mucosa of 1 in 5 individuals globally, although its precise role in these niches is not well understood. To prevent vertical transmission, broad-spectrum antibiotics are administered to GBS-positive mothers during labor in many countries. Although antibiotics have significantly reduced GBS early-onset neonatal disease, there are several unintended consequences, including an altered neonatal microbiota and increased risk for other microbial infections. Additionally, the incidence of late-onset GBS neonatal disease remains unaffected and has sparked an emerging hypothesis that GBS-microbe interactions in developing neonatal gut microbiota may be directly involved in this disease process. This review summarizes our current understanding of GBS interactions with other resident microbes at the mucosal surface from multiple angles, including clinical association studies, agriculture and aquaculture observations, and experimental animal model systems. We also include a comprehensive review of in vitro findings of GBS interactions with other bacterial and fungal microbes, both commensal and pathogenic, along with newly established animal models of GBS vaginal colonization and in utero or neonatal infection. Finally, we provide a perspective on emerging areas of research and current strategies to design microbe-targeting prebiotic or probiotic therapeutic intervention strategies to prevent GBS disease in vulnerable populations.

Profiling Antibiotic Resistance in Acinetobacter calcoaceticus

Background: Acinetobacter spp. have emerged as troublesome pathogens due to their multi-drug resistance. The majority of the work to date has focused on the antibiotic resistance profile of Acinetobacter baumannii. Although A. calcoaceticus strains are isolated in the hospital setting, limited information is available on these closely related species. Methods & Results: The computational analysis of antibiotic resistance genes in 1441 Acinetobacter genomes revealed that A. calcoaceticus harbored a similar repertoire of multi-drug efflux pump and beta-lactam resistance genes as A. baumannii, leading us to speculate that A. calcoaceticus would have a similar antibiotic resistance profile to A. baumannii. To profile the resistance patterns of A. calcoaceticus, strains were examined by Kirby−Bauer disk diffusion and phenotypic microarrays. We found that Acinetobacter strains were moderately to highly resistant to certain antibiotics within fluoroquinolones, aminoglycosides, tetracyclines, and other antibiotic classes. These data indicate that A. calcoaceticus has a similar antibiotic resistance profile as A. baumannii ATCC 19606. We also identified that all Acinetobacter species were sensitive to 5-fluoroorotic acid, novobiocin, and benzethonium chloride. Conclusion: Collectively, these data provide new insights into the antibiotic resistance in A. calcoaceticus and identify several antibiotics that could be beneficial in treating Acinetobacter infections.