Nanomaterials for targeted detection and photothermal killing of bacteria

Human pathogens are one of the major threats to global public health. Wastewater treatment plants (WWTPs) serve as city guts to receive and digest various human pathogens. Several techniques have been developed to detect human pathogens in WWTPs and to assess potential environmental risks. In this study, we employed 24 metagenomic DNA data sets derived from a high-throughput shotgun sequencing technique to more accurately and efficiently detect human bacterial pathogens in influent, activated sludge, and effluent of two Hong Kong WWTPs. Each data set was quality-filtered and normalized to 12,500,000 DNA sequences with a length of 150-190 bp. Then, a BLASTN search against Greengenes general 16S rRNA gene database and human pathogenic bacteria 16S rRNA gene database, a BLASTX search against human pathogenic bacteria virulence factor database, as well as MetaPhlAn analysis were conducted to survey the distribution, diversity, and abundance of human bacterial pathogens. The results revealed that (i) nine bacterial pathogens were detected; (ii) the overall pathogenic bacteria abundance was estimated as 0.06-3.20% in the total bacteria population using 16S rRNA gene fingerprinting; (iii) pathogenic bacteria detected in activated sludge and effluent shared similar profiles but were different from influent based on both 16S rRNA gene and virulence factor fingerprintings; (iv) Mycobacterium tuberculosis -like species may present potential pathogenic risks because it was detected with high abundance in both activated sludge and effluent. These findings provided a comprehensive profile of commonly concerned human pathogens in two Hong Kong WWTPs and demonstrated that the high-throughput shotgun sequencing technique is a feasible and effectual approach for environmental detection of human bacterial pathogens.

Two edible fishes, Bulls eye, Priacanthus hamrur (Percidae) and Hard tail scad, Megalaspis cordyla (Carangidae) from the waters of Royapuram coast, Chennai, Tamil Nadu were chosen for isolation of bacterial human pathogens in their gills, intestine, muscle and skin. Based on their growth characteristics on specific culture media, the following human bacterial pathogens, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Vibrio cholerae and Shigella dysenteriae were isolated in both the fishes. The medium of the fishes and the sediments of their habitat were furthermore collected and examined for pathogens. Different bacterial species were found in the medium that was analyzed, including the human pathogens isolated from the fishes. Surprisingly the five human bacterial pathogens harbored in the fishes were found in the medium but not in the sediment. This research is primarily to highlight the quality of these two edible fishes in the coastal waters of Royapuram, Chennai and to create awareness amid fish eating population.

We report a strategy to fabricate a rapid and stable surface-enhanced Raman scattering (SERS)-based hybrid nanomaterial using gold nanopopcorns attached single-walled carbon nanotubes (AuNP@f3-SWCNTs) for label-free detection and photothermal killing of bacteria. Herein, previously ester-functionalized single-walled carbon nanotubes (f1-SWCNTs) undergo 1,3-dipolar cycloaddition reaction with in-situ generated nitrile imine under Microwave (MW) irradiation to form a doubly ester terminated SWCNTs cycloadduct (f2-SWCNTs). The ester terminals are further modified with 4-aminothiophenol (4-ATP) under MW-irradiation to form thiol-terminated SWCNTs templates (f3-SWCNTs) that allow gold nanopopcorns (AuNPs) to covalently and uniformly attach at a minimum inter-particle distance thus yielding a hybrid nanomaterial (AuNP@f3-SWCNT) with good aqueous stability and abundant 'hotspots'. Consequently, monoclonal E. coli antibody-conjugated bioassays fabricated with our AuNP@f3-SWCNT substrates (mAb-AuNP@f3-SWCNT) rapidly detect E. coli in water with good selectivity and impressive SERS sensitivity. The detection limit of E. coli 49979, selected as a model to establish proof of principle, was found to be 1.0×102 CFU/mL. Furthermore, the AuNP@f3-SWCNT hybrid nanomaterial offers impressive photothermal pathogen killing effects. The synergy-type enhancement effect arising from the inherent noble properties of the respective components of the hybrid nanomaterial indicate that our AuNP@f3-SWCNT has the potential for further application in multiplex detection in samples.

Herein, an interference-free surface-enhanced Raman scattering (SERS) platform with a "sandwich" structure has been developed for reliable detection and photothermal killing of bacteria with whole blood as the real sample. The multifunctional platform comprised a plasmonic gold film (pAu) functionalized with bacteria-capturing units of 4-mercaptophenylboronic acid and internal reference of 4-mercaptobenzonitrile as the SERS substrate and vancomycin-modified core (gold)-shell (Prussian blue) nanoparticles (Au@PB@Van NPs) as the SERS tag. The detected SERS signals were from the Raman-silent region where no background signals occurred from biological sources, eliminating the interference and improving the detection sensitivity and accuracy. As a proof-of-concept, model bacterial strain, Staphylococcus aureus, was captured and detected in the whole blood samples. Furthermore, high antibacterial efficiency of approximately 100% was reached under the synergistic photothermal effect from pAu and Au@PB@Van NPs. This study provides a new avenue for bacteria detection in real samples and their subsequent in situ elimination.

Infectious pathogens cause severe human illnesses and great deaths per year worldwide. Rapid, sensitive, and accurate detection of pathogens is of great importance for preventing infectious diseases caused by pathogens and optimizing medical healthcare systems. Inspired by a microbial defense system (i.e., CRISPR/ CRISPR-associated proteins (Cas) system, an adaptive immune system for protecting microorganisms from being attacked by invading species), a great many new biosensors have been successfully developed and widely applied in the detection of infectious viruses and pathogenic bacteria. Moreover, advanced nanotechnologies have also been integrated into these biosensors to improve their detection stability, sensitivity, and accuracy. In this review, the recent advance in CRISPR/Cas systems-based nano/biosensors and their applications in the detection of infectious viruses and pathogenic bacteria are comprehensively reviewed. First of all, the categories and working principles of CRISPR/Cas systems for establishing the nano/biosensors are simply introduced. Then, the design and construction of CRISPR/Cas systems-based nano/biosensors are comprehensively discussed. In the end, attentions are focused on the applications of CRISPR/Cas systems-based nano/biosensors in the detection of infectious viruses and pathogenic bacteria. Impressively, the remaining opportunities and challenges for the further design and development of CRISPR/Cas system-based nano/biosensors and their promising applications are proposed.

Bacterial pathogens in the domestic environment present a risk to residents, particularly among susceptible populations. However, the impact of consumer demographic characteristics and food handling methods on kitchen microbiomes is not fully understood. The domestic kitchen bacterial communities of ten predominantly low-income families in Houston, TX, were assessed in conjunction with a cross-sectional food safety survey to evaluate differences in household and surface-specific microbiomes and bacterial foodborne pathogen presence. Three kitchen surfaces within each household, including the sink drain, the refrigerator handle, and the counter, were environmentally sampled and metataxonomically evaluated via targeted 16S rRNA sequencing. Disposable dish sponges were also acquired and examined. Results indicated that alpha diversity did not vary by the households, sampling locations, or demographic characteristics evaluated. Significant differences in beta diversity were observed among the bacterial communities of five pairs of households and between refrigerator handle and disposable dish sponge microbiomes. A total of 89 unique bacterial foodborne pathogens were identified across surface types. Each household contained at least one contaminated surface, and the most common bacterial foodborne pathogens identified were Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae. All parents reported washing their hands before meal preparation, washing fresh fruits and vegetables, and washing cutting boards with soap after use to prepare raw animal proteins. Gaps in food safety behaviors identified included a lack of serious concern for food contamination with germs and inappropriate handwashing, food handling, and cleaning behaviors. The number of unique bacterial foodborne pathogens identified within households was significantly higher among households whose respondent parent reported that they did not consider food contamination with germs to be a serious food safety problem (median: 41.0 species) compared to households whose respondent parent did consider food contamination to be a serious food safety problem (median: 3.0 species; p value = 0.0218). These results demonstrate that domestic kitchen taxonomic abundance profiles vary according to household and surface type. Data suggest that low-income consumers may be at risk of foodborne pathogen exposure from contaminated home kitchen surfaces, and that food safety attitudes may directly contribute to this hazard.

Review: 83 refs.

11 - Multifunctional Smart Biopolymer Composites as Actuators

Adaptation of plant and human pathogenic bacteria to niches of existence differing from their original ones is a sophisticated mechanism for survival. Research indicates that certain plant bacterial pathogens are capable of causing disease in humans, and some human bacterial pathogens can inhabit the plant environment and cause disease in plants. The infection of humans by plant bacteria may occur at direct physical contact with diseased plants and/or via the respiratory tract in mainly immunocompromised or otherwise stressed individuals. Indirect transmitters of plant and human microbes can be wind, rain, dust, insects, and animals. Human pathogenic bacteria may contaminate the soil and irrigation water, colonize the rhizosphere, more rarely also the phyllosphere, and can survive as epiphytes. Thus, the plant environment may become a reservoir of human pathogens. A source of foodborne human pathogenic bacteria can be unprocessed or unwashed fruits and vegetables. Especially during the last decade, the processes underlying the cross-kingdom performance of pathogenic bacteria are intensively researched. However, in reality, the risk for human health at infections by plant bacteria and by human bacterial pathogens surviving in the plant environment is still underestimated. The goal of the current review is to increase the interest in these issues in agricultural and general environments. Some basic strategies for infection and symptoms of diseases caused by the microorganisms under consideration are described. The potency of certain plant bacterial pathogens to surpass barriers towards humans and the interaction of human bacterial pathogens with the plant environment are addressed and the existing information is critically discussed.

Introduction Bukavu city is facing sanitation challenges, with many reported cases of epidemics such as cholera, salmonellosis, and other infectious diseases. Food and water sold under poor sanitation conditions are exposed to potential contamination by pathogenic bacteria. Consumers are therefore at risk of contracting bacterial infections, which could increase the burden of infectious diseases. Solid waste and wastewater management is unsatisfactory in Bukavu city. Few scientific investigations have been conducted to assess the influence of environmental conditions on food and water contamination. For these reasons, this study aimed to investigate the quality of food sold in restaurants and on the streets, as well as the types of water and milk produced and consumed, since food safety and environmental sanitation remain major public health challenges in Bukavu city. Objective The broad objective of this study was to assess the safety risks associated with food and water contamination by Salmonella enterica and Escherichia coli in Bukavu city, DR Congo. Methods A field observation was conducted to identify restaurant locations, and a probabilistic model was applied to determine the number of restaurants to be surveyed. A simple random method was then applied to survey 206 food handlers in restaurants across all three municipalities of Bukavu city. A total of 415 food samples from restaurants, 34 milk samples from dairy farms, and 104 water samples from taps, tanks, and wells were collected. Salmonella enterica and Escherichia coli were isolated from these samples, characterized, and identified through cultural methods and biochemical tests. Results The presence of Salmonella enterica was observed in 38.2% of pork, sausage, and ugali samples (n = 34 for each food), 35.5% of bread, 32.4% of beef and potatoes (n = 34 for each food), and 24.4% of beans (n = 41) tested positive for S. enterica. While Escherichia coli was not isolated from beans, beef, potato, sausage, or vegetable samples, the bacterium was most prevalent in fish (11.8%, n = 34). More than half (57.1%, n = 28) of the water samples from wells were contaminated by S. enterica, and 35.7% (n = 28) by E. coli. The high rate of well contamination could be explained by the location of wells near public waste disposal sites, sewage systems, and pathways frequently used by humans and animals. The presence of S. enterica and E. coli was not significantly different in food (p = 0.15) and water (p = 0.58), suggesting that the environmental conditions of Bukavu city are favorable for the growth of both bacterial species in food and water. However, food contamination by S. enterica and E. coli was significantly (p < 0.05) dependent on food handling practices such as "frequency of cooking food" and "heating food before serving customers" in both formal and informal restaurants (street-vended food). Conclusion Hygiene practices in Bukavu restaurants were not sufficient to guarantee safe food for human consumption, particularly during the serving stages. There is a need for public health and environmental decision-makers to develop or update guidelines in line with national and international standards to enhance public health countermeasures in and around wells, restaurants, and street-vended food and to improve water treatment and infrastructure in Bukavu city.

Endoprotein-activating DNAzyme assay for nucleic acid extraction- and amplification-free detection of viable pathogenic bacteria

The contamination of food with pathogenic bacteria is a major public health concern, requiring rapid and accurate detection methods. Conventional approaches, such as culture-based or molecular assays, are time-consuming, labor-intensive, and often demand specialized expertise. Here, we developed a deep learning-based strategy for rapid detection and classification of live bacteria using simple white-light microscopic images of microcolonies, even in the presence of morphologically similar food debris. The model, based on ResNet50 with a Region Proposal Network, was trained on Escherichia coli, Listeria monocytogenes, Bacillus subtilis, and debris from chicken, spinach, and cheese. The model trained on bacteria misclassified debris as bacteria (24.2% false positives), whereas the model trained on both bacteria and food debris achieved 0% false positives with 100% precision and 94.4% recall. Validation with GFP-producing B. subtilis in food matrices further confirmed robust performance (mPrecision 94.6%, mRecall 92.5%). This cost-effective method enables reliable bacterial detection in complex foods within 3 h.

New hospital disinfection processes for both conventional and prion infectious agents compatible with thermosensitive medical equipment

Chapter 1 - Human pathogenic microbes (bacterial and fungal) and associated diseases

Polyherbal formulations are known for various medicinal properties. The aim of this study was to biosynthesis of Silver nanoparticle (AgNps) using polyherbal extract and to evaluate their effect on human bacterial pathogens. Polyherbal extract silver nanoparticles were synthesized and the presence of AgNPs was confirmed by UV-Visible (UV-VIS) spectrophotometer and Scanning Electron Microscopic (SEM) analysis. The effect of polyherbal AgNps were evaluated against human bacterial pathogens by agar well diffusion method. The UV-VIS spectrophotometer, SEM analysis and the agar well diffusion method confirmed the potential antibacterial activity of biosynthesized polyherbal AgNPs against common bacterial pathogens such as Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, Propionibacteriun acnes, Streptococcus oralis, Enterobacter feacalis, Proteus vulgaris, Aeromonas hydrophila, Corynebacterium diphtheriae and Actinomycetes Sp. Therefore, we suggest that polyherbal AgNPs can be used for the treatment of bacterial diseases.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Preparation of polyherbal formulation from selected traditional medicinal plants (Caesalpinia bonduc, Morinda citrifolia and Nigella sativa)&#x0D; Green synthesis and characterization of silver nanoparticles synthesized using polyherbal aqueous extract and evaluate its antibacterial activity against human pathogens&#x0D; &#x0D; &#x0D; The biosynthesized silver nanoparticles that use the extract of polyherbal formulations have proven excellent antibacterial activity against human pathogens through Disc diffusion method&#x0D; The present study demonstrated a quick, rapid, and economical way of synthesizing silver nanoparticles.&#x0D; Synthesized polyherbal nanoparticles can be used against human pathogens acts as antimicrobial drug&#x0D; &#x0D; GRAPHICAL ABSTRACT