Search Results (21)

Shiga toxin–producing Escherichia coli (STEC) are important zoonotic pathogens that can disseminate through environmental water systems, yet data from Southern Italy remain scarce. The aim of this study was to investigate the occurrence and genetic characteristics of STEC isolated from surface water samples collected from rivers and lakes in the Apulia region (Southern Italy). A total of 120 samples were processed according to ISO/TS 13136:2012, followed by whole genome sequencing (WGS) for isolate confirmation and characterization. Overall, 20% of the samples were stx-positive in screening. STEC strains were isolated from 4.2% of stx-positive enrichments, corresponding to one sample out of a total of 120 (0.8%). The isolate was identified as O139:H1, carrying the stx2e subtype and belonging to sequence type ST1. Genomic analysis revealed multiple virulence-associated determinants, including the complete F18 fimbrial operon (fedA-F), hlyA, csgA, gad, chuA, yehA-D, and ompT, along with stress-resistance and tellurite-resistance genes. The strain was susceptible to all antibiotics tested. The genomic profile suggests a swine-associated lineage with multiple environmental persistence traits but limited antimicrobial resistance. The detection of a swine-associated STEC strain in surface waters highlights potential environmental dissemination pathways and underscores the importance of continued monitoring within integrated water–livestock surveillance frameworks. Full article

Extraintestinal pathogenic Escherichia coli (ExPEC) poses escalating threats to human and veterinary health amid rising antimicrobial resistance. We isolated a highly virulent ExPEC strain RZ-13 (ST345, O134:H21) from diarrheic calves at a large beef cattle farm in Rizhao City, and conducted whole genome sequencing, conjugation experiments, and antimicrobial susceptibility testing to elucidate its genomic architecture and resistance mechanisms. The RZ-13 genome comprises one chromosome and four plasmids. The chromosome harbors virulence factors for adhesion, invasion, biofilm formation, and iron acquisition. Notably, plasmids pRZ13-1 (265,777 bp, IncHI2-IncHI2A) and pRZ13-3 (74,304 bp, IncFII) carry the majority of resistance genes. Plasmid pRZ13-1 carries 25 resistance genes, including bla_CTX-M-55, floR, qnrS1, sul3, and tet(A), as well as a complete tellurite resistance gene cluster, terABCDEFZY1. Its multidrug resistance (MDR) region features an IS26-mediated tandem amplification and an approximately 29 kb inverted structure. Comparative analysis indicated that the MDR region carried by this plasmid is highly prevalent in both animal-derived and human-derived isolates. Plasmid pRZ13-3 harbors an IS91-mediated mobile region that integrates both antimicrobial resistance and stress adaptation genes, which have been repeatedly identified in plasmids from diverse sources, including animals and humans. Conjugation experiments confirmed both pRZ13-1 and pRZ13-3 plasmids are self-transmissible and confer multidrug-resistant phenotypes to recipient strains, with pRZ13-3 exhibiting an exceptionally high transfer frequency of 8.9 × 10⁻², substantially exceeding that of previously reported IncFII plasmids. These findings demonstrate that pRZ13-1 and pRZ13-3 serve as critical vehicles for resistance dissemination through complex mobile genetic element structures and efficient horizontal transfer, highlighting the urgent need for surveillance of livestock-reservoir ExPEC to mitigate public health risks. Full article

Urinary tract infections (UTIs) remain a major global health concern, with rising antimicrobial resistance prompting the search for alternative therapies. Selenium nanoparticles (Se NPs) are promising antimicrobial agents due to their unique physicochemical properties and ability to disrupt bacterial physiology. This study evaluated the antibacterial efficacy of Se NPs against four uropathogens and conducted comparative proteomic analyses to elucidate stress responses. Enumeration assays showed that Se NPs effectively inhibited bacterial growth, with Pseudomonas aeruginosa being the most susceptible and Proteus mirabilis the most resistant. Microscopy revealed Se NP-induced membrane rupture and cellular deformation across all species. Proteomic and bioinformatic analyses showed more pronounced protein regulation in P. mirabilis than in P. aeruginosa. Cluster of Orthologous Groups (COG) analysis revealed both shared and species-specific responses, while Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated activation of key stress pathways. Virulence-associated proteins were modulated in both species, with P. mirabilis uniquely upregulating stress survival and exotoxin-related proteins. Both regulated efflux pumps, suggesting active transport mitigates Se NP toxicity. P. aeruginosa showed mercury resistance, while P. mirabilis expressed tellurite resistance proteins. These findings highlight distinct yet overlapping strategies and support the potential of Se NPs in novel antimicrobial development. Full article

Introduction: Staphylococcus aureus is a high-priority foodborne pathogen contributing to several food poisoning outbreaks. Methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA), pose significant public health concerns due to their potential for serious illness, antibiotic resistance, and transmission within both healthcare and community settings. These bacteria can cause numerous infections, ranging from skin and soft tissue infections to life-threatening conditions like bloodstream infections, pneumonia, and endocarditis. Although several publications are concerned with Staphylococcus aureus contamination in ready-to-eat (RTE) food products, little published data is available about its prevalence in pizza, which is widely distributed and consumed worldwide. Methods: The current study is intended to determine the prevalence, virulence genes, and antimicrobial resistance profiles of S. aureus in three hundred ready-to-eat pizza samples (100 each of meat, chicken, and canned tuna pizzas) collected from different restaurants in Mansoura City, Egypt. The typical colonies on Baird–Parker selective agar supplemented with egg yolk tellurite emulsion were counted and further confirmed based on Gram staining, coagulase testing, catalase testing, carbohydrate fermentation, and thermostable nuclease production. The genomic DNA of the confirmed coagulase-positive isolates was prepared and subjected to PCR analyses for detecting the nuc gene, mecA (methicillin resistance gene), and vancomycin resistance gene (vanA), as well as six selected S. aureus virulence genes: sea, seb, sec, sed, hla, and tsst. The antimicrobial resistance profile of the S. aureus isolates was determined against 16 antimicrobial agents belonging to six classes using the agar disc diffusion method according to the Clinical and Laboratory Standards Institute guidelines (CLSI), except for oxacillin and vancomycin, which were assessed using the MIC test. Results: The results revealed that 56% (56/100), 56% (56/100), and 40% (40/100) of chicken, meat, and canned tuna pizzas were positive for S. aureus, with an overall prevalence of 50.7% (152/300). All 560 isolates (100%) were verified as S. aureus based on molecular confirmation of the nuc gene. Interestingly, 48.6% (272/560) and 8.6% (48/560) of the isolates tested were identified as methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA) through detection of mecA and vanA genes, respectively. Among the S. aureus isolates tested, the hla gene was detected in 87.1% (488/560), while the enterotoxin genes sea, seb, sec, and sed were identified in 50% (280/560), 78.6% (440/560), 9.8% (55/560), and 24.5% (137/560) of isolates, respectively. All recovered isolates (n = 560) were classified as multidrug-resistant and were resistant to penicillin, oxacillin, and ampicillin. Moreover, 77% (431/560), 24% (134/560), 8% (45/560), and 8.6% (48/560) of isolates were resistant to cefotaxime, ciprofloxacin, azithromycin, and vancomycin, respectively. Conclusions: The current study emphasizes that ready-to-eat pizza is highly contaminated with multidrug-resistant S. aureus, highlighting the urgent need for rationalizing antibiotic use in both veterinary and human medicine to prevent the transmission of resistant bacteria through the food chain. Additionally, strict adherence to good hygienic practices throughout all stages of the food chain is essential to minimize overall contamination and enhance food safety. Full article

Tellurite (TeO₃²⁻) is a highly soluble and toxic oxyanion that inhibits the growth of Escherichia coli at concentrations as low as ~1 µg/mL. This toxicity has been primarily attributed to the generation of reactive oxygen species (ROS) during its intracellular reduction by thiol-containing molecules and NAD(P)H-dependent enzymes. However, under anaerobic conditions, E. coli exhibits significantly increased tellurite tolerance—up to 100-fold in minimal media—suggesting the involvement of additional, ROS-independent mechanisms. In this study, we combined chemical-genomic screening, untargeted metabolomics, and targeted biochemical assays to investigate the effects of tellurite under both aerobic and anaerobic conditions. Our findings reveal that tellurite perturbs amino acid and nucleotide metabolism, leading to intracellular imbalances that impair protein synthesis. Additionally, tellurite induces notable changes in membrane lipid composition, particularly in phosphatidylethanolamine derivatives, which may influence biophysical properties of the membrane, such as fluidity or curvature. This membrane remodeling could contribute to the increased resistance observed under anaerobic conditions, although direct evidence of altered membrane fluidity remains to be established. Overall, these results demonstrate that tellurite toxicity extends beyond oxidative stress, impacting central metabolic pathways and membrane-associated functions regardless of oxygen availability. Full article

Despite their prevalence in Europe, the source of contamination of humans by Attaching-Effacing Shigatoxigenic Escherichia coli (AE-STEC) O80:H2 remains unidentified. This study aimed to assess a procedure based on non-melibiose fermentation and resistance to tellurite to isolate AE-STEC and enteropathogenic (EPEC) O80:H2 from healthy cattle. The genome sequences of 40 calf and human AE-STEC and EPEC O80:H2 were analyzed: (i) none harbored the mel operon, but the 70mel DNA sequence instead; (ii) the ter-type 1 operon was detected in 16 EPEC and stx1a or stx2a AE-STEC, while no ter-type 1 operon was detected in the remaining 24 EPEC and stx2d AE-STEC. The 21 calf AE-STEC and EPEC O80:H2 were tested phenotypically: (i) none fermented melibiose on melibiose-MacConkey agar plates; (ii) ten of the 11 ter-type 1-positive strains had Minimal Inhibitory Concentrations (MIC) ≥ 128 µg/mL to potassium tellurite; (iii) conversely, the ten ter-negative strains had MIC of two µg/mL. Accordingly, enrichment broths containing two µg/mL of potassium tellurite and inoculated with one high MIC (≥256 µg/mL) stx1a AE-STEC O80:H2 tested positive with the O80 PCR after overnight growth, but not the enrichment broths inoculated with one low MIC (two µg/mL) EPEC. Nevertheless, neither AE-STEC nor EPEC O80:H2 were recovered from 96 rectal fecal samples collected from healthy cattle at one slaughterhouse after overnight growth under the same conditions. In conclusion, this procedure may help to isolate stx1a and stx2a AE-STEC and EPEC O80:H2, but not stx2d AE-STEC that are tellurite sensitive, and new surveys using different procedures are necessary to identify their animal source, if any. Full article

Tellurium nanoparticles (TeNPs) are emerging as valuable materials in various technological and biomedical applications due to their unique physicochemical properties. In general, TeNPs are prepared using chemical methods based on a redox reaction in which strong reducing agents are employed which are often toxic and harmful to the environment. Biological biosynthesis provides a green strategy for substituting the commonly used reducing chemical agents with microorganisms or enzymes. Among the enzymes noted as key players in microbial tellurite reduction, glutathione reductase (GR) has been identified; however, its specific role in enhancing TeNP biosynthesis has yet to be fully elucidated. In this study, we aimed to evaluate the impact of GR overexpression on TeNP production in Escherichia coli (E. coli). For this purpose, four GR enzymes from different microorganisms identified as tellurite resistant were heterogeneously expressed and purified from E. coli. The kinetic parameters for NADPH and oxidized glutathione (GSSG), the native substrates of GR, were determined to evaluate their TR activity under saturated NADPH concentrations. The GR from Pseudomonas lini strain BNF22 presented the highest catalytic efficiency for NADPH and exhibited greater TR activity. This enzyme was overexpressed in E. coli MG1655 (DE3) and cells overexpressing GR increased the yield of TeNPs in those cells, presenting an increased elemental cell tellurium composition. Our results provide valuable insights for the development of engineered E. coli as a platform for TeNP biosynthesis. Using microorganisms as a green strategy for TeNP production, the results of this study highlight the enzymatic mechanisms underlying the role of GR in the biosynthesis of TeNPs. Full article

Membrane proteins constitute about 20% of the human proteome and play crucial roles in cellular functions. However, a complete understanding of their structure and function is limited by their hydrophobic nature, which poses significant challenges in purification and stabilization. Detergents, essential in the isolation process, risk destabilizing or altering the proteins’ native conformations, thus affecting stability and functionality. This study leverages single-particle cryo-electron microscopy to elucidate the structural nuances of membrane proteins, focusing on the SLAC1 bacterial homolog from Haemophilus influenzae (HiTehA) purified with diverse detergents, including n-dodecyl β-D-maltopyranoside (DDM), glycodiosgenin (GDN), β-D-octyl-glucoside (OG), and lauryl maltose neopentyl glycol (LMNG). This research not only contributes to the understanding of membrane protein structures but also addresses detergent effects on protein purification. By showcasing that the overall structural integrity of the channel is preserved, our study underscores the intricate interplay between proteins and detergents, offering insightful implications for drug design and membrane biology. Full article

Using seleno-compounds and telluric compounds is a practical approach for developing solutions against drug-resistant bacterial infections and malignancies. It will accelerate the search for novel treatments or adjuvants for existing therapies. Selenium and tellurium nanospheres can be produced by lactic acid bacteria. The bacteria can differentiate the selenium and tellurium when the medium contains both selenite and tellurite. Therefore, our question in this study was the following: are they making alloys from the selenium and tellurium and what will be the composition, color, and shape of the nanoparticles? We used a simple microbial synthesis to produce nanoselenium, nanotellurium, and their alloys from sodium selenite and sodium tellurite using Lactobacillus casei. This bacterium produced red spherical amorphous elemental selenium nanospheres with a diameter of 206 ± 33 nm from selenite and amorphous black nanorods with a length of 176 ± 32 nm and a cross-section of 62 ± 13 nm from tellurite. If the initial medium contains a mixture of selenite and tellurite, the resulting nanoparticles will contain selenium and tellurium in the same ratios in the alloy as in the medium. This proves that Lactobacillus casei cannot distinguish between selenite and tellurite. The shape of the nanoparticles varies from spherical to rod-shaped, depending on the ratio of selenium and tellurium. The color of nanomaterials ranges from red to black, depending on the percentage of selenium and tellurium. These nanomaterials could be good candidates in the pharmaceutical industry due to their antipathogenic and anticarcinogenic properties. Full article

Staphylococcus aureus was isolated from a total of 360 nasal and groin skin swabs from 180 systematic randomly-selected horses slaughtered for meat at Obollo-Afor, Enugu State, Southeast Nigeria and antimicrobial, methicillin and heavy metal resistance profile and virulence potentials of the isolates established. Baird-Parker agar with egg yolk tellurite was used for S. aureus isolation. S. aureus isolates were confirmed biochemically and serologically using a specific S. aureus Staphytect Plus™ latex agglutination test kit. The antimicrobial resistance profile, methicillin, vancomycin and inducible clindamycin resistance, and β-lactamase production of the isolates were determined with disc diffusion. Tolerance to Copper, Cadmium, Lead and Zinc was assessed using the agar dilution method and virulence potentials were determined using phenotypic methods. Forty-three (23.9%) of the 180 horses harbored S. aureus. Some 71 S. aureus were recovered from the 360 samples. Two (2.8%) of the 71 S. aureus were methicillin-resistant S. aureus (MRSA) and 69 (97.2%) were methicillin-susceptible. MRSA was recovered from 2 (1.1%) of the 180 horses. Some 9.4% of the isolates were multiple drug-resistant (MDR). The mean multiple antibiotic resistance indices (MARI) for the isolates was 0.24. Heavy metal resistance rate of the isolates ranged between 35.4–70.4%. The isolates, including the MRSA strains, displayed virulence potentials as clumping factor and catalase, gelatinase, caseinase, heamolysin, and biofilm was at the rate of 100%, 53.5%, 43.7%, 18.3% and 23.9%, respectively. This study showed that a considerable percentage of horses slaughtered in Obollo-Afor Southeastern Nigeria are potential reservoirs of virulent multiple drug- and heavy metal-resistant S. aureus, including MRSA, that could spread to humans and the environment. Full article

This study focused on the detection and quantification of selected bacteria and on the presence of enterotoxin genes in milk and dairy products from sheep and goat farms in the Czech Republic using quantitative real-time PCR (qPCR) and multiplex PCR (PCR). The presence of Corynebacterium pseudotuberculosis (CP), Mycobacterium avium subsp. paratuberculosis (MAP), Listeria monocytogenes, Staphylococcus aureus, S. aureus enterotoxin genes and methicillin-resistant Staphylococcus aureus (MRSA) was determined in 18 milk samples, 28 fresh cheeses, 20 ripened cheeses and 14 yoghurts. The serological status of the herds in relation to CP and MAP was taken into account. The most frequently detected bacterium was S. aureus (48.8%), and subsequent PCR revealed 11 MRSA positive samples. The S. aureus enterotoxin genes seg, sei and sec were detected in two goat cheeses. Cheese samples showed a statistically higher risk of SA and MRSA occurrence. CP (8.8%) and MAP (13.8%) were detected by qPCR on two different seropositive farms. Cultivation of qPCR positive CP samples on agar plates supplemented with potassium tellurite showed the presence of viable bacterium. The results obtained confirmed the necessity of monitoring the infectious status of dairy animals and rapid diagnosis of bacterial pathogens in milk and dairy products. Full article

Shiga toxin-producing Escherichia coli (STEC) O145:H28 can cause severe disease in humans and is a predominant serotype in STEC O145 environmental isolates. Here, comparative genomics was applied to a set of clinical and environmental strains to systematically evaluate the pathogenicity potential in environmental strains. While the core genes-based tree separated all O145:H28 strains from the non O145:H28 reference strains, it failed to segregate environmental strains from the clinical. In contrast, the accessory genes-based tree placed all clinical strains in the same clade regardless of their genotypes or serotypes, apart from the environmental strains. Loss-of-function mutations were common in the virulence genes examined, with a high frequency in genes related to adherence, autotransporters, and the type three secretion system. Distinct differences in pathogenicity islands LEE, OI-122, and OI-57, the acid fitness island, and the tellurite resistance island were detected between the O145:H28 and reference strains. A great amount of genetic variation was detected in O145:H28, which was mainly attributed to deletions, insertions, and gene acquisition at several chromosomal “hot spots”. Our study demonstrated a distinct virulence gene repertoire among the STEC O145:H28 strains originating from the same geographical region and revealed unforeseen contributions of loss-of-function mutations to virulence evolution and genetic diversification in STEC. Full article

Phosphate and tellurite glasses can be used in optics, optoelectronics, magneto-optics, and nuclear and medical fields. Two series of phosphate-tellurite glasses, (50-x)ZnO-10Al₂O₃-40P₂O₅-xTeO₂ and (40-x)Li₂O-10Al₂O₃-5TiO₂-45P₂O₅-xTeO₂ (x = 5, 10), were synthesized by a non-conventional wet-route, and the mechanical properties as key performance measures for their application in optoelectronics were investigated. X-ray Diffraction (XRD) measurements revealed the vitreous nature of the investigated materials. Instrumented indentation tests allowed the calculation of hardness (H) and Young’s modulus (E) using the Oliver and Pharr model. The influence of increasing the TeO₂ content, as well as the substitution of ZnO by Li₂O-TiO₂, on the variation of hardness, Young’s modulus, penetration depth (PD), and fracture toughness (FT) was evaluated in both series. As a general trend, there is a decrease in the hardness and Young’s modulus with increasing penetration depth. The addition of Li₂O and TiO₂ instead of ZnO leads to improved hardness and elastic modulus values. Regarding the H/E ratio, it was found that the samples with lower TeO₂ content should be significantly more crack-resistant compared to the higher TeO₂ content samples. The H³/E² ratio, being lower than 0.01, revealed a poor resistance of these glasses to plastic deformation. At the same time, a decrease of the fracture toughness with increasing TeO₂ content was noticed for each glass series. Based on dilatometry measurements, the thermal expansion coefficient as well as the characteristic temperatures of the glasses were measured. Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray analysis (FESEM-EDX) revealed a uniform distribution of the elements in the bulk samples. The mechanical properties of these vitreous materials are important in relation to their application as magneto-optical Faraday rotators in laser cavities. Full article

Tellurite is highly toxic to bacteria and commonly used in the clinical screening for pathogens; it is speculated that there is a potential relationship between tellurite resistance and bacterial pathogenicity. Until now, the core function genes of tellurite resistance and their characteristics are still obscure. Pseudomonas citronellolis SJTE-3 was found able to resist high concentrations of tellurite (250 μg/mL) and formed vacuole-like tellurium nanostructures. The terZABCDE gene cluster located in the large plasmid pRBL16 endowed strain SJTE-3 with the tellurite resistance of high levels. Although the terC and terD genes were identified as the core function genes for tellurite reduction and resistance, the inhibition of cell growth was observed when they were used solely. Interestingly, co-expression of the terA gene or terZ gene could relieve the burden caused by the expression of the terCD genes and recover normal cell growth. TerC and TerD proteins commonly shared the conserved sequences and are widely distributed in many pathogenic bacteria, highly associated with the pathogenicity factors. Full article

Cattle are the main reservoir of Shiga toxin-producing Escherichia coli (STEC), one of the world’s most important foodborne pathogens. The pathogen causes severe human diseases and outbreaks. This study aimed to identify and characterize non-O157 STEC isolated from cattle feces from central and southern Chile. We analyzed 446 cattle fecal samples and isolated non-O157 STEC from 12.6% (56/446); a total of 93 different isolates were recovered. Most isolates displayed β-glucuronidase activity (96.8%; 90/93) and fermented sorbitol (86.0%; 80/93), whereas only 39.8% (37/93) were resistant to tellurite. A subgroup of 30 representative non-O157 STEC isolates was selected for whole-genome sequencing and bioinformatics analysis. In silico analysis showed that they grouped into 16 different sequence types and 17 serotypes; the serotypes most frequently identified were O116:H21 and O168:H8 (13% each). A single isolate of serotype O26:H11 was recovered. One isolate was resistant to tetracycline and carried resistance genes tet(A) and tet(R); no other isolate displayed antimicrobial resistance or carried antimicrobial resistance genes. The intimin gene (eae) was identified in 13.3% (4/30) of the genomes and 90% (27/30) carried the stx2 gene. A phylogenetic reconstruction demonstrated that the isolates clustered based on serotypes, independent of geographical origin. These results indicate that cattle in Chile carry a wide diversity of STEC potentially pathogenic for humans based on the presence of critical virulence genes. Full article