Scrub typhus is a mite-borne, acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is a re-emerging infectious disease of the tsutsugamushi triangle. Scrub typhus is transmitted through bites of contaminated chiggers (larval stage). Diagnosis of scrub typhus is challenging as its symptoms mimic with other acute febrile illnesses. Several methods are effectual for diagnosis of scrub typhus that includes enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), immunochromatographic test (ICT), Weil-Felix, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). Weil-Felix test was initially used for the diagnosis of scrub typhus in underdeveloped countries but not preferred due to a lack of both specificity and sensitivity. Other immuno-based methods like IFA and ELISA are most outrank for detection of scrub typhus due to their higher sensitivity and specificity, but not vigorous to lay bare the infection at early stages and need the convalescent sampling for verification of positive samples. On another deed, PCR based methods becoming acceptable over era due to its dexterity of early-stage diagnosis with higher specificity and sensitivity but lack its applicability in circumstances of scrub typhus due to the variegated genetic makeup of Orientia tsutsugamushi among its serotypes. The present review focused on various detection methods along with their advantages and disadvantages used in the diagnosis of scrub typhus. A comparison between available methods of diagnosis with challenges in the detection of scrub typhus is also summarized.

Purpose This review focuses on the spoilage strategies used by the Pseudomonas fluorescens, and in addition, it also discusses various diagnostic approaches used for its identification in food items. Some challenges faced and advances in the detection of P. fluorescens and also discussed in this review. Methods An extensive literature search was performed with published work and data was analyzed in detail to meet the requirements of the objectives. Results P. fluorescens are unicellular rods, with long straight or curved axis, but not helical, motility by one or more polar flagella, Gram-negative, non-spores former, stalks, or sheaths. P. fluorescens is represented by seven biotypes denoted by the letters A, B, C, D, E, F, and G. The microbe shows wide choice of growth temperature and causes contamination and spoilage in ordinary and refrigerated food items by its enzymes and pigment production. The biofilm formation by P. fluorescens poses another serious threat to the food industries. Conclusion Molecular identification of P. fluorescens is generally done by 16S rRNA, intergenic spacer (ITS1) utilizing traditional polymerase chain reactions (PCR). Nowadays, qPCR and multiplex PCR are largely utilized in identification of P. fluorescens based on AprX gene (extracellular caseinolytic metalloprotease) in the milk and meat spoilage strains. The available methods still show some disadvantages with accuracy and specificity of detection. Rapid detection of P. fluorescens in food samples is the need of hour to improve the detection efficiency.

The intake of microbial-contaminated food poses severe health issues due to the outbreaks of stern food-borne diseases. Therefore, there is a need for precise detection and identification of pathogenic microbes and toxins in food to prevent these concerns. Thus, understanding the concept of biosensing has enabled researchers to develop nanobiosensors with different nanomaterials and composites to improve the sensitivity as well as the specificity of pathogen detection. The application of nanomaterials has enabled researchers to use advanced technologies in biosensors for the transfer of signals to enhance their efficiency and sensitivity. Nanomaterials like carbon nanotubes, magnetic and gold, dendrimers, graphene nanomaterials and quantum dots are predominantly used for developing biosensors with improved specificity and sensitivity of detection due to their exclusive chemical, magnetic, mechanical, optical and physical properties. All nanoparticles and new composites used in biosensors need to be classified and categorized for their enhanced performance, quick detection, and unobtrusive and effective use in foodborne analysis. Hence, this review intends to summarize the different sensing methods used in foodborne pathogen detection, their design, working principle and advances in sensing systems.

Progress in the medical profession is determined by the achievements and effectiveness of new antibiotics in the treatment of microbial infections. However, the development of multiple-drug resistance in numerous bacteria, especially Gram-negative bacteria, has limited the treatment options. Due to this resistance, the resurgence of cyclic polypeptide drugs like colistin remains the only option. The drug, colistin, is a well-known growth inhibitor of Gram-negative bacteria like Acinetobacter baumanni, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Technological advancements have uncovered the role of the mcr-1(mobilized colistin resistance) gene, which is responsible for the development of resistance in Gram-negative bacteria, which make them distinct from other bacteria without this gene. Additionally, food animals have been determined to be the reservoir for colistin resistance microbes, from which they spread to other hosts. Due to the adverse effects of colistin, many developed countries have prohibited its usage in animal foods, but developing countries are still using colistin in animal food production, thereby imposing a major risk to the public health. Therefore, there is a need for implementation of sustainable measures in livestock farms to prevent microbial infection. This review highlights the negative effects (increased resistance) of colistin consumption and emphasizes the different approaches used for detecting colistin in animal-based foods as well as the challenges associated with its detection.

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The first gold-mercaptopropionic acid-polyethylenimine composite based electrochemical DNA biosensor was fabricated for the early detection of Streptococcus pyogenes infection in humans causing rheumatic heart disease (heart valve damage). No biosensor is available for the detection of rheumatic heart disease (RHD). Therefore, the mga gene based sensor was developed by the covalent immobilization of a 5'-carboxyl modified single stranded DNA probe onto the gold composite electrode. The immobilized probe was hybridized with the genomic DNA (G-DNA) of S. pyogenes from throat swabs and the electrochemical response was measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance (EI). Covalent immobilization of the probe onto the gold composite and its hybridization with G-DNA was characterized by FTIR and SEM. The sensitivity of the sensor was 110.25 μA cm(-2) ng(-1) with DPV and the lower limit of detection was 10 pg per 6 μL. The sensor was validated with patient throat swab samples and results were compared with available methods. The sensor is highly specific to S. pyogenes and can prevent damage to heart valves by the early detection of the infection in only 30 min.

Accurate and on time diagnosis of plant viruses is an essential prerequisite for efficient control in field conditions. A number of diagnostic methods have been reported with the required level of sensitivity. Here, we propose a label free immunosensor for efficient and sensitive detection of capsicum chlorosis virus (CaCV) in bell pepper. Antigen was immobilized over the surface of gold nanoparticle/multi-walled carbon nanotube (Nano-Au/C-MWCNT) screen printed electrodes using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) cross linking chemistry followed by interaction with groundnut bud necrosis virus (GBNV)/CaCV specific polyclonal antibody. The electrochemical response was measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV) using the redox indicator. Electrode surface characterization was done by performing scanning electron microscopy (SEM). Electrochemical studies showed positive results at different antigenic dilutions ranging from 10 - 8x10. The sensitivity of the immunosensor developed has been compared with direct antigen coated enzyme-linked immunosorbent assay (DAC-ELISA) and the results showed that the immunosensor developed was 800-1000 times more sensitive, when compared to DAC-ELISA for CaCV detection. The immunosensor we have developed is economical and sensitive and could be used for immediate determination of the presence of virus in extracts from bell pepper leaves.

The present review is intended to describe bloodstream infections (BSIs), the major pathogens responsible for BSIs, conventional tests and their limitations, commercially available methods used, and the aptamer and nanomaterials-based approaches developed so far for the detection of BSIs. The advantages associated with aptamers and the aptamer-based sensors, the comparison between the aptamers and the antibodies, and the various types of aptasensors developed so far for the detection of bloodstream infections have been described in detail in the present review. Also, the future outlook and roadmap toward aptamer-based sensors and the challenges associated with the aptamer development have also been concluded in this review.