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Two independent recent studies have revealed how distinct components of the biofilm matrix contribute to its architectural stability and functionality.

is a prominent pathogen causing life-threatening bloodstream infections. Although biofilm formation and resistance to human serum are well-recognized virulence traits, their interrelatedness during bloodstream infections remains unclear. Here, we hypothesize that biofilm production is related to 's ability to thrive in human serum and, therefore, may predict the strains' ability for serum survival. We analyzed 57 clinical, genetically diverse classical strains and characterized their survival and biofilm-producing ability in human serum. Serum survival patterns revealed three serum resistance categories-Low, Mid, and High. In addition, the biofilm biomass produced by the strains correlated with their serum resistance level ( < 0.001), and 3D biofilm visualization using confocal microscopy further confirmed that biofilm extracellular polysaccharide substances and biomass patterns were consistent with the serum resistance categories. Moreover, we revealed a direct correlation between the level of biofilm formation and the strain's serum survival level ( = 0.696), a prerequisite for systemic dissemination. As biofilm formation in serum reflects both survival and biofilm-forming ability, we assessed biofilm formation in defined modified basal medium (BM2), to rule out serum-mediated killing, and discovered a strong and significant association between the serum resistance category and BM2 biofilm biomass ( < 0.0001). By applying regression models, we discovered that biofilm formation serves as a significant predictor for bacterial survival in serum. Overall, our findings establish biofilm production in as a biomarker of serum survival and may open a new avenue for predicting bloodstream infection risk in clinical settings.IMPORTANCEBloodstream infections caused by are devastating life-threatening infections worldwide. Understanding the survival strategies of in the bloodstream is critical for elucidating key aspects of bacterial pathogenicity and developing new diagnostic and therapeutic modalities. Although serum survival is a recognized virulence trait necessary to thrive in the bloodstream, the relationship between serum resistance and biofilm formation, a multicellular organization that may protect bacteria from bloodstream stressors, remains poorly understood. In this article, we demonstrate biofilm production in human serum by clinical classical strains for the first time and discovered a direct correlation between the level of biofilm biomass formation and the degree of serum survival in human serum and in defined modified basal medium. These findings offer insights into the importance of biofilm production in serum resistance and may be used to develop future therapeutic strategies targeting bloodstream infections.

Biofilms are problematic structures in the context of microbial infections due to their ability to resist both host- and drug-mediated attempts at tissue sterilization. Consequently, it is imperative to identify mechanisms underlying the development of these structures and the emergent properties they develop. The filamentous fungal pathogen Aspergillus fumigatus forms robust-structured biofilms that are resistant to contemporary antifungal drug treatments, although the mechanisms are ill-defined. In this study, we compared the transcriptional landscape of two A. fumigatus reference strains grown as biofilms and in planktonic culture conditions to identify biofilm-specific genes and pathways. These analyses and subsequent genetic and phenotypic studies revealed that a ceramide synthase is important for biofilm development and is involved in antifungal drug susceptibility of the biofilm. Consequently, these data support the rationale for targeting fungal lipid homeostasis for antifungal therapeutic development, particularly in the context of biofilm-mediated infections.

IntroductionBacterial vaginosis (BV) is the most common vaginal infection among women around the world, characterised by the replacement of the normal vaginal microbiota by anaerobic bacteria, mainly G. vaginalis a Gram negative coccobacillus that is isolated in up to 98% of the cases. This bacterium is classified into eight biotypes and has several virulence factors such as the production of biofilm and phospholipase C (PLC) that are associated with gineco-obstetric complications. Therefore, it is necessary to evaluate the relationship between biotypes and virulence factors with BV, which was the main objective of this study.Methods250 samples of vaginal swab were analysed; the samples were inoculated on Columbia agar for the isolation of G. vaginalis. We use Amsel and Nugent criteria for the classification of vaginal flora and for the diagnosis of BV. For biotyping, we use Piot et al 1984 classification (hydrolysis of hippurate, β-galactosidase and lipase). Biofilm production was performed in 96-well plates and the results were classified as non-producing (<0.1), moderate (0.1–0.2) and abundant (>0.2). We measured PLC production on skim milk agar.ResultsWe isolated G. vaginalis in 75% (187) of the samples, of wich 15% (37) were associated with BV whereas 60% (150) with normal flora. We identify biotypes 1 (19%), 2 (8%), 5 (16%) and 6 (57%) in BV cases, whereas in normal flora we identify the same biotypes at different frequency [1 (22%), 2 (11%), 5 (21%) and 6 (46%)]. We observed PLC production in 22% of the cases associated with BV and at 27% in normal flora. We observed that 76% of strains associated with BV were non-producers, 19% were moderate and 5% were abundant, whereas in the normal flora group was 66%, 26% and 8%, respectively.Conclusion: G. vaginalis was isolated in 75% of the samples (15% associated with BV and 60% in normal flora). We identified biotypes 1, 2, 5 and 6 of G. vaginalis; the production of PLC and biofilm was similar in both study groups. We couldn’t associate biotypes and virulence factors with BV.

Biofilms are structured communities of microorganisms that attach to surfaces and persist within a self-produced matrix. The biofilm lifestyle underlies microbial survival in nature, contributes to industrial biofouling, and drives many chronic infections. Despite the importance of biofilms, high-throughput measurements of biofilm growth dynamics are challenging using existing tools, which are often disruptive or are not scalable. To overcome this limitation, we developed “label-free analysis of biofilms” (LFAB), a brightfield-based imaging platform that enables real-time, non-perturbative, and scalable quantification of biofilm biomass. LFAB is broadly applicable across species and correlates strongly with traditional assays. Applying LFAB to Streptococcus pneumoniae , a major human pathogen, we performed a mutagenesis screen, uncovering new genetic regulators of biofilm formation in this organism. These findings advance understanding of S. pneumoniae pathogenesis and establish LFAB as a powerful approach for dissecting the molecular basis of microbial community growth.