The increasing clinical burden of antimicrobial-resistant Klebsiella pneumoniae, together with its capacity for biofilm formation and persistence, has intensified the search for alternative and adjunctive antimicrobial strategies. Phycocyanin is a cyanobacteria-derived phycobiliprotein with emerging biological and antimicrobial properties; however, its activity against K. pneumoniae, particularly across planktonic, biofilm, and antibiotic-response phenotypes, remains insufficiently characterized. Klebsiella pneumoniae ATCC 700,603 was used as the experimental strain, and phycocyanin obtained from Sigma was evaluated for antibacterial and antibiofilm activity. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution and subsequent subculture, respectively. Bacterial growth kinetics were monitored for 72 h under sub-inhibitory phycocyanin exposure, while direct antibacterial activity was evaluated using an agar well diffusion assay. Biofilm formation was assessed using the crystal violet microtiter-plate method. Changes in antibiotic inhibition-zone diameters following sub-inhibitory phycocyanin exposure were evaluated using ampicillin, ceftriaxone, and imipenem. All experiments were performed in triplicate. Phycocyanin exhibited measurable antibacterial activity against K. pneumoniae, with MIC and MBC values of 10 and 20 mg/mL, respectively. Growth-kinetic analysis showed comparable bacterial growth during the initial hours, followed by sustained attenuation of growth in phycocyanin-exposed cultures from approximately 6 h onward. In the agar well diffusion assay, inhibition-zone diameters increased in a concentration-dependent manner, from approximately 7 mm at the lowest tested amount to 12 mm at the highest. Phycocyanin also inhibited biofilm formation in a concentration-dependent manner, with maximum inhibition reaching 41.3
The increasing prevalence of multidrug-resistant (MDR) Klebsiella pneumoniae and its capacity to form persistent biofilms highlight the need for alternative antimicrobial strategies. This study characterised the lytic bacteriophage vB_KpnS_Tech (PQ859379.1) and evaluated its activity in combination with meropenem against established MDR K. pneumoniae biofilms of different maturities. vB_KpnS_Tech exhibited rapid adsorption, with 98.8
The ongoing search for new endodontic irrigants is critical due to the persistence of resistant microorganisms within the root canal system. This study evaluated the hydroethanolic extracts of Salvia rosmarinus (rosemary) and Plinia cauliflora (jabuticaba) for their chemical composition, antioxidant activity, synergistic and antibiofilm effects against a clinical strain of Enterococcus faecalis and standard strains of Porphyromonas gingivalis and Fusobacterium nucleatum. Additionally, their cytotoxicity was tested on human keratinocytes (HaCaT). The extracts were prepared and filtered. The content of soluble solids, flavonoids, and phenols were quantified. High-performance liquid chromatography (HPLC) was performed later. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated. Then, the free radical suppressive (antioxidant) activity and the synergistic activity of the extract’s combination using checkerboard microdilution assay were evaluated. The most effective concentrations were analyzed against biofilms. Later, the cytotoxicity of the extracts was tested on human keratinocyte lines (HaCaT). Data were analyzed by the Kruskal Wallis and Dunn test (p ≤ 0.05). S. rosmarinus extract contained 9.48 mg/mL of soluble solids and was rich in caffeoylquinic and chlorogenic acids. P. cauliflora had 22.22 mg/mL of soluble solids, with gallic and ellagic acids as major compounds. Both extracts demonstrated antioxidant activity at 59 μg/mL for S. rosmarinus and 159 μg/mL for P. cauliflora. An additive antibacterial effect was observed against E. faecalis when 0.036 mg/mL of S. rosmarinus was combined with 2.77 mg/mL of P. cauliflora. Both extracts at low concentrations did not reduce the metabolic activity of HaCaT cells.
Environmental fungi are increasingly recognized as emerging pathogens and potential agents for biotechnological applications. Candida palmioleophila, an ascomycete yeast originally isolated from soil, has demonstrated resistance to fluconazole and capacity for bioremediation of fats and pharmaceuticals. The Brazilian poultry industry produces large volumes of wastewater, which can serve as a reservoir for fungal species with pathogenic and environmental importance. In this study, we performed a fungal screening of wastewater from poultry slaughterhouses. Wastewater samples were collected from a poultry slaughterhouse in São José do Vale do Rio Preto, Rio de Janeiro. Fungal isolation was performed using Sabouraud Dextrose Agar supplemented with antibiotics. Only yeasts were obtained and identified by polyphasic taxonomy. Species identification of both isolates were confirmed by MALDI-TOF MS and ITS sequencing, and the antifungal susceptibility of the strains was evaluated using the Vitek2 system. Physicochemical parameters of the effluent were measured. Candida species were identified and their susceptibility profile described: C. palmioleophila (resistant to fluconazole) and C. parapsilosis (susceptible to all antifungals tested). Physicochemical analyses revealed moderate effluent characteristics, potentially favoring yeast survival. This study reports the first isolation of C. palmioleophila from poultry slaughterhouse wastewater in Brazil, providing phenotypic, proteomic, and molecular characterization of the isolate and expanding the knowledge of fungal diversity in poultry slaughterhouse wastewater. These findings highlight the value of a One Health perspective for monitoring fungal diversity in wastewater and identifying microorganisms of potential biotechnological interest.
The large-scale application of livestock and poultry manure in protected agriculture is common; however, research on the spread of antibiotic resistance genes (ARGs) from this practice remains limited. Herein, 16 S and metagenomic sequencing methods were used to investigate the effects of eight consecutive years of pig manure application on tetracycline (TC) antibiotics in protected soil and to evaluate the ecological consequences. In addition, the characteristics of soil ARGs and bacterial diversity were explored, and the potential hosts of ARGs in protected soil and the influence of environmental factors on these potential hosts and ARGs were preliminarily investigated. After 8 years of applying composted pig manure, the total tetracycline residues in the protected soil was as follows: commercial organic fertilizer soil > pig manure soil > rapeseed cake fertilizer soil. Soil enzymes indirectly affect ARG abundance by influencing the microbial community structure. g__unclassified_p__Acidobacteria and g__unclassified_c__Actinomycetia may be the two most important ARG hosts, with a highly significant positive correlation with 32 ARG subtypes. Total nitrogen (TN) and soil organic matter (SOM) significantly promoted the abundance of these two important potential hosts. Nocardioides, g__unclassified_o__Solirubrobacterales, Actinoplanes, and Methyloceanibacter are potential hosts for intI1. TC, Soil urease(S-UE), Soil acid phosphatase(ACP), Soil β-glucosidase(S-β-GC), TN, total phosphorus (TP), and SOM significantly promoted the abundance of potential intI1 hosts. Soil environmental factors collectively accounted for 72.27
