International Microbiology最新文献

This study analyzed the prevalence and antimicrobial resistance patterns of Enterococcus faecium (Efm) infections within a tertiary pediatric hospital in Mexico, highlighting the critical need to understand the epidemiology of this opportunistic pathogen in vulnerable pediatric populations. The primary objective is to elucidate the current landscape of Efm infections in children, including prevalent resistance profiles, which will enable the development of efficient control strategies and optimize empirical treatment regimens. A retrospective analysis of clinical isolates of Efm collected over 7 years (2018-2024) was conducted, encompassing detailed microbiological data, including species identification, antimicrobial susceptibility testing, and patient demographics. Antimicrobial susceptibility testing was performed using the VITEK 2 automated system and interpreted according to CLSI guidelines. Also, the isolates were typified using RAPD. This study's results revealed a significant prevalence of Efm infections among hospitalized children, particularly those in intensive care units and oncology wards. Many isolates were resistant to multiple antibiotics, including vancomycin, aminoglycosides, and beta-lactams, posing significant therapeutic challenges. Finally, the isolates could be grouped into five RAPD types, supporting the idea that the strains have a genetic relationship. This study demonstrates the impact of Efm infections on the pediatric population in a third-level hospital. The high incidence of XDR strains (85%), although only 40% of the isolates are vancomycin-resistant, exposes a serious menace that Efm represents. Additionally, the correlation identified between certain antibiotic resistance patterns may be important for empirical treatment.

Schyzocotyle acheilognathi is an invasive generalist cestode with a high capacity for adaptation to multiple hosts and freshwater environments. Recent reports suggest that this parasite possesses an intrinsic symbiotic microbiota distinct from that of its fish hosts, and its presence induces gut dysbiosis in the host. In this study, we reassessed these ideas. For this, we collected naturally parasitized fish specimens from different locations in Mexico, encompassing different host species, including Cyprinus carpio, Pseudoxiphophorus bimaculatus, Tlaloc hildebrandi, and Vieja hartwegi. We also tested whether this parasite induces a dysbiotic process in the gut bacterial community of Tlaloc hildebrandi. Parasites were identified based on morphological and molecular criteria, and their bacterial communities were characterized using metataxonomy. Our results revealed that S. acheilognathi does not harbor a consistent microbial community among the different host species surveyed. We also did not detect any dysbiotic effect on the gut microbiota of Tlaloc hildebrandi. These findings contradict previous data and provide evidence of the loose relationship between this parasite and bacteria, which we propose could be a part of its successful generalist strategy. The results presented herein offer a novel perspective on the quest for understanding the microbial ecology in generalist cestodes of freshwater fish.

Bacteriophages are major determinants of bacterial community dynamics. Industrial wastewaters constitute distinctive microbe-phage ecosystems shaped by heavy-metal and chemical stressors, yet they remain sparsely characterized by metagenomics. Most existing studies focus on municipal or hospital wastewaters, while phage and bacteriome communities in industrial effluents such as ceramic wastewater are largely unexplored. This study aimed to comprehensively characterize bacterial and phage communities in influent and effluent samples from a ceramic factory using metagenomic approaches. Phage DNA was sequenced on an Illumina NextSeq and processed with a standard bioinformatics pipeline for taxonomic and functional annotation. Of 657 million raw reads, 66% mapped to phage sequences. Caudovirales predominated, with Autographiviridae comprising 59% of classified viral reads. Functional annotation indicated that 64% of assigned genes encoded structural or replication functions. For the bacteriome, 16 S rRNA (V3-V4) amplicons were sequenced on an Illumina NovaSeq 6000 and classified with Kraken2. Proteobacteria dominated both sample types, but community structure shifted along the treatment line: the influent was enriched in environmental-water genera-Flavobacterium (25%), Aeromonas (16%), and Acinetobacter (11%) -whereas the effluent was dominated by Flavobacterium (37%), Hydrogenophaga (25%), and Rhodoferax (14%). Genus-level richness contracted from 228 (influent) to 67 (effluent), and the number of reads entering taxonomic classification declined sharply (1,482,914 vs. 55,847), consistent with selective removal and physicochemical filtering during treatment. Collectively, these results demonstrate that ceramic wastewater harbors a distinct microbe-phage ecosystem molded by chemical and particulate stress. By illuminating an understudied industrial niche, this work provides actionable insights for wastewater treatment, environmental bioremediation, and microbial risk assessment.

Biosurfactant production by a novel Cyberlindnera fabianii MIAU-1 isolate was achieved using co-carbon substrates glucose and sunflower oil, in addition to yeast extract and urea as nitrogen sources. The surface tension of the fermentation medium, consisting of optimal concentrations of glucose (10%), sunflower oil (10%), yeast extract (3 g/L) and urea (3 g/L), was reduced to 36.39 mN/m. This strain produced 39.85 g/L of biosurfactant after 48 h of fermentation under bioreactor conditions. This indicates a 6.78% increase over the 37.32 g/L biosurfactant produced using shake flask after 72 h. The biosurfactant was purified and then characterized using FT-IR and NMR. The crude (CBS) and purified (PBS) biosurfactants were determined to have glycolipid (sophorolipid) structure. The degradation temperatures of CBS and PBS were determined to be 255 °C and 275 °C, respectively, following thermogravimetric analysis. CBS reduced the surface tension of distilled water to about 40 mN/m at 43.63 mg/L its critical micelle concentration (CMC); and PBS reduced it to about 50 mN/m at 1290.91 mg/L CMC. CBS maintained stable surface activity over the range of pH, salinity, temperature, and heating time. Additionally, CBS used at various concentrations exhibited antibacterial activity and inhibited the growth of Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7. CBS also showed anti-adhesive activity to prevent biofilm formation of Staphylococcus aureus and L. monocytogenes.

Fungal endophytes inhabiting the medicinal plants have been considered repertoire for bioactive metabolites. In the current study, the medicinal plant Polygala sinaica was used for the first time as a source for endophytic fungi, which were screened for novel bioactive compounds. The potent biologically active fungal isolate was morphologically identified and molecularly verified using 18S rDNA sequencing as F. oxysporum with accession # OR616565. Two compounds were isolated using flash chromatography, identified using GC/MS and NMR techniques, and quantified using HPLC. Identified compounds were bis-(2-ethylhexyl) phthalate (DEHP) (1) and dibutyl phthalate (DBP) (2) isolated for the first time from F. oxysporum. The ethyl acetate extract of F. oxysporum exhibited potent activity against different multi-drug resistant Gram-negative and Gram-positive bacteria and Candida tropicalis. The production of DEHP was studied in different modified Wickerham media, using oat flakes, rice, and tomato as carbon sources, while corn steep liquor (CSL) and soy protein were used as nitrogen sources. CSL-containing medium exhibited the highest DEHP production by F. oxysporum at an initial pH of 7.2, 0.1% inoculum size after 15 days of incubation under static conditions at 28 °C. The biosynthesis of DEHP by F. oxysporum would serve as an excellent safe and eco-friendly source for its production to be used medicinally and industrially on a large scale with less toxic effects. The current data brings insights into the potency of Fusarium oxysporum, an endophyte of Polygala sinaica, for the production of bis-(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP).

Biofilm formation and other virulence phenotypes under quorum sensing regulation play a vital role in the pathogenicity of Aeromonas hydrophila, triggering the emergence of multi-drug resistance (MDR) which increases fish mortality, environmental issues, and economic loss in aquaculture, necessitating the discovery of novel drugs to bypass standard antibiotics. Here, quorum quenching (QQ) may be a sustainable anti-virulent approach. β-Lactamase enzyme obtained from Chromohalobacter sp. strain D23 restricted violacein pigmentation in Chromobacterium violaceum CV026 by degrading C4-homoserine lactone (C4-HSL) and C6-HSL up to 70% (P < 0.0001). HPLC study also revealed > 73% enzymatic breakdown of both C4-HSL and C6-HSL within 2 h. Crude β-lactamase also hampered biofilm formation of A. hydrophila by reducing total biomass (> 66%, P < 0.001) and cellular viability (62%, P < 0.0001) without affecting planktonic growth. QS-mediated other virulence factors of A. hydrophila, like hemolysin, serine protease, exopolysaccharides, metalloprotease, and lipase activities, were also significantly inhibited (P < 0.0001). Draft genome size of strain D23 was 3.6 mb, having 64.01% G + C content. Annotation revealed the presence of a MBL (metallo-beta-lactamase)-fold metallo-hydrolase enzyme. Multiple sequence alignment indicated the presence of the conserved ⁶⁶HXHXDH⁷¹ domain. Pairwise alignment showed 65% ≤ sequence identity with known marine lactonase enzymes. The molecular docking study revealed moderate binding affinity of β-lactamase to C4-HSL and C6-HSL (- 5.3 kcal/mol). Thus, the present study shows the potent QQ activity of β-lactamase of strain D23 against MDR A. hydrophila, targeting their pathogenesis without necessarily killing them, which can minimize the use of antibiotics in aquaculture and also suggests possible biomedical use. This study also highlights the usefulness of less explored marine bacteria as a potent source of bioactive enzymes.

This study is aimed at evaluating the efficacy of essential oil-based microemulsions in combination with antimicrobials against Mycoplasma gallisepticum (MG), a major respiratory pathogen in poultry. MG was isolated from 1.1% of broiler and 0.5% of breeder flocks, with the highest incidence recorded during winter and autumn, particularly in farms located in Giza and Sharkia governorates. Among 37 confirmed isolates, eight were positive for the mgc2 gene, while six carried gapA and crmA. Cumin, camphor, and olive microemulsions exhibited favorable physicochemical characteristics. GC-MS analysis identified α-citral, ( +)-2-bornanone, and cis-vaccenic acid as the major components of cumin, camphor, and olive oils, respectively. Notably, olive/camphor and cumin microemulsions were rich in cis-vaccenic acid and linoleoyl chloride, respectively. Antibiotic susceptibility testing revealed that all isolates were resistant to lincomycin, erythromycin, spectinomycin, and tiamulin, with 50% exhibiting complete resistance to all antibiotics. Tylosin showed partial activity, inhibiting 37.5% of isolates (MIC 0.25-4 µg/mL). Camphor microemulsion demonstrated the highest antimicrobial effect (MIC 0.08-5 µg/mL). The most significant synergistic interaction was observed between cumin oil and either oxytetracycline or spiramycin, as well as between camphor microemulsion and doxycycline against MG isolates. Furthermore, combination treatments significantly downregulated the expression of mgc2, crmA, and gapA genes. These findings highlight the promising role of essential oil-based microemulsions as effective adjuncts in MG control strategies.

Environmental pollution by heavy metals is a major global concern, necessitating the exploration of sustainable bioremediation strategies. Airborne bacteria represent an underexplored resource in this context. This study investigated the potential of bacteria isolated from bioaerosols for the bioremediation of heavy metals. Nine bacterial strains belonging to the genera Exiguobacterium, Kocuria, Rhodococcus, and Staphylococcus were isolated and identified through MaLDI-TOF analysis and 16S rRNA gene sequencing. The minimum inhibitory concentrations (MIC) of chromium, copper, lead, nickel, mercury, and cadmium were determined to evaluate metal resistance. Bioreduction assays were performed to determine the capacity of selected strains to reduce hexavalent chromium [Cr(VI)] in solution. Chromate reductase activity was quantified in Rhodococcus rhodochrous As33. Morphological responses to chromium exposure were examined using scanning and transmission electron microscopy (SEM and TEM). MIC analyses revealed variable but significant resistance to multiple Heavy metals among the isolates. Bioreduction assays demonstrated that five selected strains reduced from 79.9% to 100% of Cr(VI) within 72 h. R. rhodochrous As33 achieved complete Cr(VI) reduction, as confirmed by 1,5-diphenylcarbazide complexation, and inductively coupled plasma mass spectrometry (ICP-MS). Enzymatic analysis indicated a chromate reductase activity of 67.87 U mg⁻¹ of total protein in this strain. SEM and TEM revealed marked cellular adaptations to chromium stress, including pleomorphism, membrane thinning, vesicle formation, and the deposition of extracellular electron-dense precipitates, suggesting active biosorption and bioprecipitation mechanisms. The results highlight the bioremediation potential of airborne bacteria, particularly R. rhodochrous As33, in heavy metal-contaminated environments. Further studies are needed to validate their performance under complex environmental conditions and to support their application in sustainable remediation strategies.

Produced water (PW), a major by-product of the petrochemical industry, contains a complex mixture of contaminants that limit its reuse and pose environmental risks if discharged untreated. Numerous treatment technologies have been developed to remediate this water, with bioremediation standing out as one of the most promising novel approaches. One such bioremediation method is through the application of cyanobacteria, which are able to remove pollutants such as heavy metals from produced water, although the mechanism by which the pollutants are removed is still unknown. In this study, a well-characterized cyanobacterium, Synechococcus elongatus, was used as a model organism to establish a proof of concept for identifying genes responsive to PW exposure and heavy metal stress. RNA sequencing was performed to analyze transcriptomic changes in S. elongatus grown in BG-11 (control) and exposed to 3 mg/mL of iron (heavy metal (HM)) or 25% v/v PW in BG-11. Differential expression analysis revealed that 11 and 67 genes were ≥ fivefold upregulated, and 337 and 27 genes were ≥ fivefold downregulated under HM and PW exposure, respectively, compared to the control. Among the over-expressed genes, the plasma membrane transporter, nitrate ABC transporter permease, was identified, suggesting its important role in the bioremediation process of heavy metals from wastewater. These findings provide foundational insights into stress-responsive gene networks in cyanobacteria and inform future bioengineering strategies for enhancing bioremediation capabilities in S. elongatus and related strains.

Pseudomonas aeruginosa (P. aeruginosa) represents a critical global health challenge due to its escalating antibiotic resistance and its formidable ability to form protective biofilms, necessitating the urgent development of novel therapeutic strategies. This research explores the potential of allicin, a natural antibacterial compound, encapsulated within alginate-casein (ACAN) nanoparticles as a promising approach to combat multidrug-resistant (MDR) P. aeruginosa proliferation and biofilm formation. The ACAN nanoparticles were comprehensively characterized for their morphological traits using FESEM, DLS, and FTIR, confirming successful allicin encapsulation and enhanced stability. Notably, the ACAN formulation demonstrated significantly improved antibacterial efficacy and a profound ability to inhibit biofilm growth. Specifically, ACAN nanoparticles achieved up to 77% inhibition of P. aeruginosa biofilm growth, a statistically significant improvement compared to free allicin (e.g., ~ 28% inhibition). Furthermore, the study investigated the impact of ACAN on key biofilm-related genes, revealing a marked downregulation of pslG (involved in exopolysaccharide production) and lasI (critical for quorum sensing and biofilm maturation). These findings collectively highlight that encapsulating allicin within alginate-casein nanoparticles not only enhances its stability and delivery but also significantly boosts its efficacy against the persistent biofilm-forming capabilities of MDR P. aeruginosa. This novel ACAN platform thus presents a compelling and promising therapeutic strategy for addressing challenging bacterial infections.