Changes in pore formation, strength characteristics and mineral composition of Portland cement M500 during biofouling under conditions simulating a deep geological radioactive waste repository were evaluated. The biocide polyhexamethylene guanidine (PHMG) was added to inhibit microbial growth. After two years, microbial activity was found to be a key determinant of the cement’s strength characteristics due to the dissolution of primary mineral phases (portlandite, C3S, C2S and C2FA) and the formation of calcite. The volume fraction of cracks increased by an average of 25 times in all samples. Notably, the addition of PHMG did not significantly affect the porosity of the cement, and its compressive strength parameters showed no correlation with pore and crack content during long-term storage. The observed strength increase with PHMG is likely attributable to the formation of an additional polymer skeleton within the cement matrix.

Burkholderia pseudomallei, the causative agent of melioidosis, presents high antimicrobial resistance, largely due to its biofilm-forming ability. Here, innovative lecithin/chitosan microparticles loaded with lemongrass (LEO) and geranium (GEO) essential oils (LEOLCN and GEOLCN) were developed and characterized as a novel strategy to combat B. pseudomallei. Microparticles were characterized and evaluated for their effects on planktonic growth and biofilm inhibition, as well as for potential synergistic interactions with antibiotics. Microparticles exhibited a spherical morphology, high encapsulation efficiency, and sustained release profiles, with up to 45% of EO released at pH 2.0 and 32% at pH 7.4 after 50 h. LEOLCN demonstrated MICs ranging from 64 to 128 µg ml–1 for most strains, although some resistant isolates exhibited MICs of up to 2,048 µg ml–1. At a concentration of 512 µg ml–1, both LEOLCN and GEOLCN reduced biofilm biomass and metabolic activity by more than 50%. LEOLCN exhibited synergistic effects with conventional antibiotics, reducing ceftazidime MICs by 2- to 9-fold, suggesting its potential to enhance antibiotic therapy against resistant strains. Scanning electron microscopy confirmed biofilm disruption. Overall, the dual antimicrobial and antibiofilm action of these compounds introduces a promising and innovative in vitro platform to address the persistent challenge of B. pseudomallei infections and biofilm-associated resistance.

Polymicrobial biofilms of Staphylococcus aureus and Pseudomonas aeruginosa pose serious clinical challenges due to their persistence, metabolic adaptability, and antibiotic tolerance. The present study investigated the ability of these two bacteria to co-exist and form mixed-species biofilms and evaluated the antibiofilm potential of piperine, a plant-derived alkaloid from Piper nigrum. Co-existence of S. aureus and P. aeruginosa was confirmed by enumeration of colony-forming units, growth kinetics, cross-streaking, metabolic fingerprinting, Gini coefficient analysis, and antibiotic susceptibility. Sub-minimum inhibitory concentrations of piperine significantly inhibited mixed-species biofilm formation, as demonstrated by biochemical, microbiological and microscopic analysis. Piperine treatment led to noticeable reductions in biofilm biomass, exopolysaccharide content, total protein content, metabolic activity and extracellular DNA. Mechanistic investigations revealed that piperine impaired biofilm-forming determinants by reducing cellular co-aggregation and cell surface hydrophobicity, inducing intracellular reactive oxygen species (ROS) accumulation, and increasing membrane permeability. Significantly, piperine effectively disrupted pre-established mixed-species biofilms, and its antibiofilm efficacy was further validated in a catheter model, highlighting its relevance against device-associated infections. Collectively, these findings demonstrate that piperine inhibits and disintegrates S. aureus-P. aeruginosa biofilms through diverse mechanisms, positioning it as a promising phytochemical for managing biofilm-associated infections.

Candidozyma auris has high rates of resistance to antifungals and hospital disinfectants. This yeast remains on surfaces for long periods, favoring the colonization of patients. Similarly Candida species, it produces persistent biofilms, which contribute to invasive infections, resulting in high mortality rates. In the search for new therapeutic alternatives of antifungal action, natural products have been widely studied due to their pharmacological potential and diverse biological activities. Eugenol and cinnamaldehyde are derived from the essential oils of cinnamon and clove, respectively, and have shown action against several microorganisms, including Candida species. The aims of the present study were to evaluate the antibiofilm activity of the natural products eugenol and cinnamaldehyde on clinical isolates of C. auris. Both products showed inhibitory action on planktonic form. Biofilm biomass was considerably reduced for most of the evaluated isolates. On the other hand, during the treatment period, the metabolic activity of most isolates increased, compared to control, possibly due to the heteroresistance phenomenon; however, further studies are still needed to support this hypothesis.

Biofouling organisms threaten biodiversity as their pelagic larvae settle on submerged surfaces and are transported on the hulls of ships. Conventional antifouling paints are effective but release toxic biocides. We evaluated a nature-based alternative using exudates from the native sea anemone Anthothoe chilensis. Crude and diluted exudates (100%, 70%, 50%) were tested on larval settlement and behaviour of the bryozoan Bugulina flabellata, and compared with seawater and exudates from the non-native Anemonia alicemartinae. Settlement was strongly reduced under 100% A. chilensis exudate, while diluted treatments did not differ from controls. Larvae also swam longer and explored less, indicating behavioural deterrence. By contrast, A. alicemartinae exudate did not affect behaviour. Adult interactions showed asymmetric chemical interference. These results suggest that A. chilensis exudates act as selective chemical deterrents influencing recruitment and competition, pending comprehensive chemical characterisation and toxicity assessment, to determine their suitability as potential antifouling agents.

Catheter-associated urinary tract infections (CA-UTI) are among the most prevalent infections, affecting over 150 million individuals worldwide annually. Candida is the most common fungal genus causing urinary infections, representing a significant medical challenge, particularly in patients undergoing prolonged catheterization—a risk factor that exacerbates clinical conditions by promoting the formation of resistant biofilms. In this context, the coating of catheters with antimicrobial substances combined with drug repositioning is an innovative alternative. In this study, we evaluated the activity of promethazine (PMT), a first-generation antihistamine, against the formation of Candida spp. biofilms on urinary catheter fragments. Broth microdilution, impregnation of urinary catheter fragments, and scanning electron microscopy (SEM) were the exploratory techniques employed. PMT proved to be an effective agent in inhibiting biofilm formation, achieving a 50% reduction in colony-forming units (CFU/mL). The results indicated that PMT exhibits high potential as an antifungal agent, with promising applications in coatings aimed at preventing Candida spp. infections associated with long-term urinary devices.

Biofilm development, which occurs on numerous surfaces, can reduce the efficiency and increase operating costs in bioprocesses and fermentation. The current study proposes a strategy for biofilm inhibition by investigating the interactions between microorganisms and surfaces using an extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) approach and cell partition index (CPI) technique. Glass slide and Petri dish surfaces were modified with different surfactants. The results show that modification increased CPI values and altered the interaction behavior from attractive to repulsive, between microbial cells and different surfaces. Secondary energy values calculated by xDLVO theory between microbial cells and modified surfaces were repulsive. Meanwhile, the secondary energy values calculated for microbial cells and unmodified glass slide (−31 kT) and Petri dish surfaces (−27 kT) were attractive between cells and surfaces. The current study has opened a window for research in the field of biofilm inhibition through a surface energetics approach.

Antifouling coating development requires extensive performance testing. Coatings that prevent aquatic larval settlement are of interest because many forms of macrofouling begin at the larval stage. However, field testing can be time consuming and poorly controlled. Herein is reported a screening tool, Settlement of Larvae Assay using Mussels (SLAM), for down-selecting materials prior to field testing. The method entails using a dense concentration of mussel larvae that are allowed to settle on submerged test surfaces. Settled larvae are then quantified to provide a measure of antifouling performance. The SLAM test differentiated coatings with only slight differences in formulation. To enable efficient quantification of dense larvae settlement, an automated counting method was developed that combines two analyses: a color thresholding identifies larvae clumps, and a machine learning algorithm identifies non-clumped larvae. This automated ‘hybrid’ approach rapidly quantifies settled larvae as effectively as manual counting but in a fraction of the time.

Biofilm formation was investigated in a maize rot-causing pathogen, Fusarium verticillioides. This work revealed that in vitro cultures produce structured, adherent communities with a dense extracellular matrix (ECM) surrounding hyphae that makes up the biomass of a matured biofilm. Pellicle containing exopolysaccharide had a hydrodynamic diameter of 4.19 nm and a low viscosity (0.022 dl/g). The exopolysaccharide was composed of amino sugars and unordered, facilitating stability through complexation with the anionic eDNA. Biofilm formation varied over different pH and temperature values, emphasising its role in promoting adaption, survival, and persistence in F. verticillioides, potentially contributing to its pathogenicity in maize. Collectively, the results provide valuable insights into biofilm structure and stress resistance in this fungus, and will serve as a foundation for future studies incorporating in planta infection systems.

This study aimed to investigate the antibiofilm activity of Aleppo pine essential oil (APEO); hydrolytic enzyme mixtures or their combination in two sequential washing steps against C. sakazakii on plastic and stainless steel surfaces. The minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of APEO against C. sakazakii strains were 500–1,000 µg/ml, and 1,000–4,000 µg/ml, respectively. Further, APEO showed antibiofilm activity where 4 × MIC APEO at 25 °C for 30 min reduced C. sakazakii cells by 1.8 and 1.6 log CFU/coupon on plastic and stainless steel, respectively. Similarly, both enzyme mixtures reduced the C. sakazakii cells attached to both surfaces by 1.7–2.2 log CFU/coupon. However, the two-step sequential cleaning regime with enzyme mixture of 10% protease, 5% α-amylase, and 1% lipase at 50 °C for 30 min followed by 4 × MIC APEO for 30 min reduced C. sakazakii biofilm on both surfaces by 4.4–4.5 log CFU/coupon compared to the control.