Isolation and identification of enterotoxigenic Staphylococcus aureus isolates from Indian food samples: evaluation of in-house developed aptamer linked sandwich ELISA (ALISA) method

Effect of silver nanoparticles and REP-PCR typing of Staphylococcus aureus isolated from various sources

This is the primary study at Matrouh Governorate to unveil antibiotic resistance, biofilm formation, silver nanoparticles (Ag-NPs) effect using electron microscopy, and REP-PCR analysis of Staphylococcus aureus strains isolated from COVID-19 patients, contaminated food, and Morel's diseased sheep and goats. A total of 15 S. aureus strains were isolated; five from each of the COVID-19 patients, Morel's diseased sheep and goats, and contaminated food. All strains were considered multidrug-resistant (MDR). All strains showed the presence of biofilm. Morphological changes in the cell surface of the bacterium were evidenced, and penetration with the rupture of some bacterial cells. Based on REP-PCR analysis, 4 clusters (C1-C4) with dissimilarity between clusters C1 and C2 8% and between C3 and C4 15%. Cluster I included 3 strains from contaminated food with a similarity of 97%, and Cluster II included 2 strains from contaminated food and 2 from COVID-19-infected patients with a similarity of 96% (confirming the zoonotic nature of this pathogen). Cluster III contained 4 strains isolated from Morel's diseased sheep & goats with a similarity ratio of 99% in comparison the 4th cluster contained 3 strains isolated from COVID-patients and one from Morel's diseased sheep & goats with a similarity ratio of 92%.

Conventional and advanced detection techniques of foodborne pathogens: A comprehensive review

Foodborne pathogens are a major public health concern and have a significant economic impact globally. From harvesting to consumption stages, food is generally contaminated by viruses, parasites, and bacteria, which causes foodborne diseases such as hemorrhagic colitis, hemolytic uremic syndrome (HUS), typhoid, acute, gastroenteritis, diarrhea, and thrombotic thrombocytopenic purpura (TTP). Hence, early detection of foodborne pathogenic microbes is essential to ensure a safe food supply and to prevent foodborne diseases. The identification of foodborne pathogens is associated with conventional (e.g., culture-based, biochemical test-based, immunological-based, and nucleic acid-based methods) and advances (e.g., hybridization-based, array-based, spectroscopy-based, and biosensor-based process) techniques. For industrial food applications, detection methods could meet parameters such as accuracy level, efficiency, quickness, specificity, sensitivity, and non-labor intensive. This review provides an overview of conventional and advanced techniques used to detect foodborne pathogens over the years. Therefore, the scientific community, policymakers, and food and agriculture industries can choose an appropriate method for better results.

Advances in microbial analysis: based on volatile organic compounds of microorganisms in food

In recent years, microbial volatile organic compounds (mVOCs) produced by microbial metabolism have attracted more and more attention because they can be used to detect food early contamination and flaws. So far, many analytical methods have been reported for the determination of mVOCs in food, but few integrated review articles discussing these methods are published. Consequently, mVOCs as indicators of food microbiological contamination and their generation mechanism including carbohydrate, amino acid, and fatty acid metabolism are introduced. Meanwhile, a detailed summary of the mVOCs sampling methods such as headspace, purge trap, solid phase microextraction, and needle trap is presented, and a systematic and critical review of the analytical methods (ion mobility spectrometry, electronic nose, biosensor, and so on) of mVOCs and their application in the detection of food microbial contamination is highlighted. Finally, the future concepts that can help improve the detection of food mVOCs are prospected.

Prevalence of staphylococcal toxin in food contaminated by Staphylococcus spp.: Protocol for a systematic review with meta-analysis

BACKGROUND

Food contamination by Staphylococcus spp. enterotoxigenic strains is quite common and despite underreporting caused by the short duration of clinical symptoms and lack of medical care, staphylococcal food poisoning is one of the most common Foodborne Diseases (FBD) in the world. This study describes a systematic review protocol with meta-analysis on the prevalence and types of staphylococcal enterotoxins in food, and the profile of contaminated foods.

METHODS

The research will be conducted through the selection of studies reporting the analysis of staphylococcal enterotoxins in food contaminated by Staphylococcus spp. Searches will happen on the following databases: Medline (OVID), GALE, Science Direct, CAB Direct (CABI), Google Scholar, in addition to manual search in the list of references of articles, directory of theses and dissertations, and countries' health agencies. Reports will be imported into the application Rayyan. Two researchers will independently select studies and extract data, and a third reviewer will solve conflicting decisions. The primary outcome will be the identification of staphylococcal enterotoxins in food, and the secondary outcomes will include staphylococcal enterotoxin types and foods involved. To assess the risk of bias in the studies, the tool developed by the Joanna Briggs Institute (JBI) will be used. For data synthesis, a meta-analysis will be performed. However, in case that is not possible, a narrative synthesis of the most relevant results will be carried out.

DISCUSSION

This protocol will serve as the basis for a systematic review that aims to relate the results of existing studies on the staphylococcal enterotoxin prevalence and types in food, and the profile of the contaminated foods. The results will broaden the perception of food safety risks, highlight existing literature gaps, contribute to the study of the epidemiological profile and may guide the allocation of health resources for the development of preventive measures related.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42021258223.

Multi-Biofunctional Properties of Phytofabricated Selenium Nanoparticles From Carica papaya Fruit Extract: Antioxidant, Antimicrobial, Antimycotoxin, Anticancer, and Biocompatibility

The present study focused on phytofabrication of selenium nanoparticles (SeNPs) from Carica papaya extract and exploration of their multi-biofunctional features. Total phenolics and flavonoids of C. papaya fruit extract were determined as 23.30 ± 1.88 mg gallic acid equivalents and 19.21 ± 0.44 mg quercetin equivalents per gram, respectively, which suggested that C. papaya fruit extract could be a competitive reducing and stabilizing agent during phytofabrication of nanoparticles. UV-Vis and FTIR spectroscopy showed the formation of SeNPs from sodium selenite, which could be related to the reducing and stabilizing activities of C. papaya fruit extract. The SeNPs were found to be stable with a Zeta potential of -32 mV. The average hydrodynamic size of SeNPs was found as 159 nm by dynamic light scattering. The SeNPs showed a broader XRD pattern with no sharp Bragg's peaks and found to be amorphous. SEM showed that SeNPs were spherical in shape and EDX pattern showed that SeNPs were made up of Se (71.81%), C (11.41%), and O (14.88%). The HR-TEM picture showed that SeNPs were spherical in morphology and have a size range of 101-137 nm. The SeNPs exhibited potent antioxidant activity and their EC50 values (effective concentration required to inhibit 50% of radicals) were 45.65 ± 2.01 and 43.06 ± 3.80 μg/ml in DPPH and ABTS assays, respectively. The antimicrobial action of SeNPs was found as a broad spectrum and suppressed microbial pathogens in ascending order: fungi > Gram-positive bacteria > Gram-negative bacteria. The SeNPs have been demonstrated to reduce the growth and ochratoxin A (OTA) of mycotoxigenic Aspergillus ochraceus and Penicillium verrucosum at 40 μg/ml in broth culture, which is noteworthy. The SeNPs reduced cancer cell proliferation (RAW 264.7, Caco-2, MCF-7, and IMR-32) more preferentially than normal cells (Vero), found to be highly biocompatible. Lower doses of SeNPs (up to 50 μg/ml) were shown to be less toxic and did not cause death in Danio rerio (zebrafish) embryos, implying that lower doses of SeNPs could be beneficial for biological purposes. The present study concluded that phytofabricated SeNPs have multiple biofunctional properties, including antioxidant, antimicrobial, antimycotoxin, and anticancer activities, as well as high biocompatibility.

Characterization of Staphylococcus aureus isolates from pastry samples by rep-PCR and phage typing

BACKGROUND AND OBJECTIVES

Staphylococcus aureus is one of the most common causes of food poisoning. This study aimed to identify S. aureus isolated from pastries, the virulence factors, antimicrobial resistance patterns, biofilm formation, and then classification based on SCCmec types, phage types, and also Rep types.

MATERIALS AND METHODS

In this study, 370 creamy and dried pastry samples have been randomly collected from different confectioneries in Hamadan city. The S. aureus isolates were identified by conventional microbiological methods and nuc gene amplification. The virulence factors and prophage genes were detected. After that, the biofilm production and antibiotic susceptibility assay of S. aureus isolates were examined. Finally, the isolates were classified by rep-PCR typing.

RESULTS

Among 370 samples, 97 creamy (34.64%) and 3 dried (3.33%) pastry samples were contaminated with S. aureus. Antibiotic sensitivity results showed the highest resistance to penicillin (90%) but none of them were MRSA. According to biofilm formation assay, 14 strains (45%) were strongly adhesive. The dominant phage among isolates was SGF, especially SGFa subgroup. About half of the isolates carried SCCmec Types I and III. Analysis of the genetic linkage between isolates by rep-PCR showed ≥80% genetic similarity and also different rep-types of S. aureus isolates.

CONCLUSION

The presence of different prophage encoded virulence factors and antibiotic resistance enable S. aureus strains to produce a broad range of diseases. Thus, consumption of creamy pastries increases the risk of infection with S. aureus and it is a serious warning to the health system.

Evaluation of Staphylococcus aureus growth and staphylococcal enterotoxin production in delicatessen and fine bakery products

Staphylococcal food poisoning is one of the most prevalent causes of foodborne intoxication worldwide. Sandwiches and desserts are susceptible to contamination by S. aureus due to the high proportion of manual work during their production. Our study aimed to evaluate the impact of storage conditions on staphylococcal enterotoxin production in sandwiches and buttercream puffs. Foods were inoculated with different S. aureus strains capable of producing type A, B, and C staphylococcal enterotoxins and incubated at 15, 25, and 30 °C. During the storage, samples were analysed for S. aureus counts and for staphylococcal enterotoxins. An enzyme-linked fluorescence assay was used to detect staphylococcal enterotoxins. The influence of inappropriate storage on S. aureus growth and staphylococcal enterotoxin production was evaluated. No staphylococcal enterotoxins were detected in sandwiches stored for 72 h at any of the tested temperatures. In buttercream puffs, enterotoxins type A, B, and C were detected within 24 h of storage at 25 °C.

Recent Advances and a Roadmap to Aptamer-Based Sensors for Bloodstream Infections

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.

Detection of Bacterial Pathogens and Antibiotic Residues in Chicken Meat: A Review

Detection of pathogenic microbes as well as antibiotic residues in food animals, especially in chicken, has become a matter of food security worldwide. The association of various pathogenic bacteria in different diseases and selective pressure induced by accumulated antibiotic residue to develop antibiotic resistance is also emerging as the threat to human health. These challenges have made the containment of pathogenic bacteria and early detection of antibiotic residue highly crucial for robust and precise detection. However, the traditional culture-based approaches are well-comprehended for identifying microbes. Nevertheless, because they are inadequate, time-consuming and laborious, these conventional methods are not predominantly used. Therefore, it has become essential to explore alternatives for the easy and robust detection of pathogenic microbes and antibiotic residue in the food source. Presently, different monitoring, as well as detection techniques like PCR-based, assay (nucleic acid)-based, enzyme-linked immunosorbent assays (ELISA)-based, aptamer-based, biosensor-based, matrix-assisted laser desorption/ionization-time of flight mass spectrometry-based and electronic nose-based methods, have been developed for detecting the presence of bacterial contaminants and antibiotic residues. The current review intends to summarize the different techniques and underline the potential of every method used for the detection of bacterial pathogens and antibiotic residue in chicken meat.

Recent Progress in the Identification of Aptamers Against Bacterial Origins and Their Diagnostic Applications

Aptamers have gained an increasing role as the molecular recognition element (MRE) in diagnostic assay development, since their first conception thirty years ago. The process to screen for nucleic acid-based binding elements (aptamers) was first described in 1990 by the Gold Laboratory. In the last three decades, many aptamers have been identified for a wide array of targets. In particular, the number of reports on investigating single-stranded DNA (ssDNA) aptamer applications in biosensing and diagnostic platforms have increased significantly in recent years. This review article summarizes the recent (2015 to 2020) progress of ssDNA aptamer research on bacteria, proteins, and lipids of bacterial origins that have implications for human infections. The basic process of aptamer selection, the principles of aptamer-based biosensors, and future perspectives will also be discussed.

Nanobodies Based on a Sandwich Immunoassay for the Detection of Staphylococcal Enterotoxin B Free from Interference by Protein A

As one of the leading causes of food poisoning, staphylococcal enterotoxins (SEs) secreted by Staphylococcus aureus pose a serious threat to human health. The immunoassay has become the dominant tool used for the rapid detection of harmful bacteria and toxins as a result of its excellent specificity. However, with regard to SEs, staphylococcal protein A (SpA) is likely to bind with the fragment crystallizable (Fc) terminal of the traditional antibody and result in a false positive, limiting the practical application of this method. Therefore, to eliminate the bottleneck problem, the sandwich immunoassay was development by replacing the traditional antibody with a nanobody (Nb) that lacked a Fc terminal. Using 0.5 × 10⁷ colony-forming units, the Nb library was constructed using Bactrian camels immunized with staphylococcal enterotoxin B (SEB) to obtain a paired Nb against SEB with good affinity. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed using one Nb as the capture antibody and a phage-displayed Nb with signal-amplifying properties as the detection antibody. In optimal conditions, the current immunoassay displayed a broad quantitative range from 1 to 512 ng/mL and a 0.3 ng/mL limit of detection. The recovery of spiked milk, milk powder, cheese, and beef ranged from 87.66 to 114.2%. The Nbs-ELISA was not influenced by SpA during the detection of SEB in S. aureus food poisoning. Therefore, the Nb developed here presented the perfect candidates for immunoassay application during SE determination as a result of the complete absence of SpA interference.

Prevalence and antibiotic resistance profiles of Staphylococcus sp. isolated from food, food contact surfaces and food handlers in a Moroccan hospital kitchen

Food poisoning risk related to the consumption of contaminated food with known foodborne pathogens or antibiotic-resistant bacteria is currently a serious threat for public health. Thus, pathogenic methicillin-resistant Staphylococcus strains are considered as one of the major cause of foodborne diseases in hospitals. The present study aims to determine the prevalence and the antibiotic resistance patterns of Staphylococcus in various types of hospital food samples, work surfaces and its carriage by food handlers. A total of 608 collected samples including 300 food samples, 238 food contact surfaces and 70 nasal and hand samples were tested. The identified Staphylococcus and their antibiotic resistance patterns were analysed using the agar disk-diffusion and PCR method was used for mecA resistance gene amplification. The prevalence of S. aureus and the coagulase-negative staphylococci were 17·33 and 23·33%, respectively. The antibiotic resistance reached 100% towards oxacillin and Penicillin G for both S. aureus and CoNs. The mecA gene was detected in 5·71% (4/70) and 7·69% (4/52) of S. aureus and CoNs strains, respectively. The outcome of this study enlightens isolation of MRSA strains and resistant CoNs from food, food contact surfaces and food handlers. The presence of this resistant species in this critical setting, where products were intended to vulnerable and immunocompromised patients, represents a serious threat to this community. It can be a source of nosocomial infection and more precautions must be taken to prevent staphylococci food contamination mainly in hospitals. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study describing the antibiotic resistance patterns of Staphylococcus aureus and coagulase-negative Staphylococcus isolated from hospital food, food contact surfaces and food handlers samples in a Moroccan hospital kitchen. High levels of multi-resistance were reported. The alarming outcome of this study emphasizes the crucial need of implementing an approach to fight multidrug-resistant staphylococci mainly in healthcare settings, where the community have already compromised health issues.

Phytofabrication of Selenium Nanoparticles From Emblica officinalis Fruit Extract and Exploring Its Biopotential Applications: Antioxidant, Antimicrobial, and Biocompatibility

In the present study, phytofabricated selenium nanoparticles (PF-SeNPs) were prepared from aqueous fruit extract of Emblica officinalis in a facile, green, economic, tactic and eco-friendly way. The aqueous fruit extract of E. officinalis was found to be rich with various secondary metabolites including phenolics (59.18 ± 2.91 mg gallic acid equivalents/g), flavonoids (38.50 ± 2.84 mg catechin equivalents/g), and tannins (44.28 ± 3.09 mg tannic acid equivalents/g) and determined that highly appropriate for the biosynthesis of nanoparticles. The facile phytofabrication of PF-SeNPs was confirmed by UV-visible and FTIR spectroscopic analysis. The XRD pattern and Raman spectroscopy showed that synthesized PF-SeNPs were amorphous in nature. The Zeta potential analysis confirmed that PF-SeNPs were negatively charged (-24.4 mV). The DLS analysis revealed that PF-SeNPs were in nano size and less aggregated with poly-dispersity index of less than 0.2. The SEM images depicted that PF-SeNPs were spherical in shape. The EDX analysis revealed that PF-SeNPs were constituted with Se (61.60%), C (29.96%), and O (4.41%). The HR-TEM analysis determined that PF-SeNPs were in nano size with an average diameter of 15–40 nm. The PF-SeNPs have offered fascinating bio-potential applications, such as antioxidant, antimicrobial and biocompatibility. They have also exhibited dose-dependent free radical scavenging activity, and EC50 was determined as 15.67 ± 1.41 and 18.84 ± 1.02 μg/mL for DPPH and ABTS assays, respectively. The PF-SeNPs has also shown the wide range of antimicrobial activity on foodborne pathogens, and it was found to be highly efficient on fungi followed by Gram-positive and Gram-negative bacteria. The biocompatibility of PF-SeNPs was assessed in N2a cells with much higher IC50 value (dose required to inhibit 50% of cell viability) compared to sodium selenite. Also, mitochondrial membrane potential (MMP) and caspase-3 were much less altered on treatment of PF-SeNPs related to sodium selenite. The cytotoxic studies clearly determined that PF-SeNPs was much less toxic and safer related to sodium selenite. Thus, PF-SeNPs could find suitable application as antioxidant and antimicrobial agent in food, biomedical, and pharmaceutical industry.