Food poisoning and Staphylococcus aureus enterotoxins

Assessment of microbial communities in a dairy farm from a food safety perspective

Microbial communities associated with dairy farm operations have a significant influence on food safety, dairy product quality, and animal health. This study aimed to create a microbial mapping at a dairy farm to learn about their bacterial diversity, distribution, and potential dissemination pathways. The investigation included the detection of key zoonotic pathogens, enumeration of Staphylococcus aureus and Escherichia coli as indicators of typical bacterial loads in a dairy production environment, and a microbiome analysis using metagenomics. A total of 160 samples (environmental, udder swabs, feed, feces, raw milk, and water) were collected during winter (N = 80) and spring (N = 80). In winter, Cronobacter spp. were detected in four feed and two water samples; L. monocytogenes was identified in two samples, one from feces and one from a cattle mat; E. coli O157:H7 was found in two feed samples. On the other hand, during spring, Cronobacter spp. were present in four feed samples and one hallway drain, with only one feed sample testing positive for E. coli O157:H7, while L. monocytogenes was absent during the spring season. Regarding microbial counts, there was no significant difference between the two seasons (p = 0.068) for S. aureus; however, a significant difference (p = 0.025) was observed for E. coli. Environmental microbiome analysis showed the presence of Proteobacteria (46.0 %) and Firmicutes (27.2 %) as the dominant phyla during both seasons. Moraxellaceae (11.8 %) and Pseudomonadaceae (10.62 %) were notable during winter, while Lactobacillaceae (13.0 %) and Enterobacteriaceae (12.6 %) were prominent during spring. These findings offer valuable insights into microbial distribution within a dairy farm and potential risks to animal and human health through environmental cross-contamination.

Phytochemical fingerprint revealing antibacterial and antioxidant activities of endemic banana cultivars in Southeast Asia

This study explores the bioactive secondary metabolite profiles of the peels of three major cultivars of bananas (Musa acuminata and Musa balbisiana). These cultivars are primarily grown in Southeast Asia and are widely consumed due to their rich nutritional and fiber content. The research utilizes advanced analytical techniques, specifically HPLC-DAD-q-TOF-MS/MS, in conjunction with both univariate and multivariate statistical analyses, to analyze the ethanolic extracts of the banana peels. This study identifies phenolic acids, flavonoids, and proanthocyanidins as significant contributors to the differentiation of the cultivars. The secondary metabolites rutin, chlorogenic acid, and gentisic acid are pinpointed as the key discriminants. Moreover, the research demonstrates a synergistic contribution of certain phytochemicals to the antioxidant and antibacterial properties of the banana peel extracts. The fingerprint profiling tools introduced in this study offer a reliable method for identifying metabolite biomarkers for the discrimination of banana cultivars.

Enterotoxigenic Staphylococcus aureus in Brazilian artisanal cheeses: Occurrence, counts, phenotypic and genotypic profiles

The present study aimed to assess the occurrence and counts of Staphylococcus aureus in Brazilian artisanal cheeses (BAC) produced in five regions of Brazil: Coalho and Manteiga (Northeast region); Colonial and Serrano (South); Caipira (Central-West); Marajó (North); and Minas Artisanal cheeses, from Araxá, Campos das Vertentes, Cerrado, Serro and Canastra microregions (Southeast). The resistance to chlorine-based sanitizers, ability to attach to stainless steel surfaces, and antibiogram profile of a large set of S. aureus strains (n = 585) were assessed. Further, a total of 42 isolates were evaluated for the presence of enterotoxigenic genes (sea, seb, sec, sed, see, seg, sei, sej, and ser) and submitted to typing using pulsed-field gel electrophoresis (PFGE). BAC presented high counts of S. aureus (3.4-6.4 log CFU/g), varying from 25 to 62.5%. From the S. aureus strains (n = 585) assessed, 16% could resist 200 ppm of sodium hypochlorite, whereas 87.6% produced strong ability to attach to stainless steel surfaces, corroborating with S. aureus ability to persist and spread in the environment. Furthermore, the relatively high frequency (80.5%) of multidrug-resistant S. aureus and the presence of enterotoxin genes in 92.6% of the strains is of utmost attention. It reveals the lurking threat of SFP that can survive when conditions are favorable. The presence of enterotoxigenic and antimicrobial-resistant strains of S. aureus in cheese constitutes a potential risk to public health. This result calls for better control of cheese contamination sources, and taking hygienic measures is necessary for food safety. More attention should be paid to animal welfare and hygiene practices in some dairy farms during manufacturing to enhance the microbiological quality of traditional cheese products.

Staphylococci, Reptiles, Amphibians, and Humans: What Are Their Relations?

Reptiles and amphibians are largely present in many environments, including domestic areas when they are kept as pet animals. They often harbor zoonotic pathogens, which can pose a serious risk of infection for humans, mainly immunocompromised individuals, the elderly, children, and pregnant women. Several studies have been carried out to verify the role of cold-blooded animals in the epidemiology of some bacteria, mainly Salmonella, whereas scarce attention has been focused on these animals as a source of staphylococci. These bacteria are often antimicrobial-resistant and they act as opportunistic pathogens, which can cause relevant infections in humans and animals, both domestic and wild. Asymptomatic reptiles and amphibians often harbor staphylococcal strains, such as Staphylococcus aureus and coagulase-negative Staphylococcus spp.; however, these bacteria have been associated with clinical conditions that usually appear in animals under stress conditions. In all cases, greater attention should also be focused on staphylococci in cold-blooded animals due to their implications in human and veterinary medicine.

Staphylococcus aureus Isolated From Traditional Artisanal Raw Milk Cheese from Southern Brazil: Diversity, Virulence, and Antimicrobial Resistance Profile

Staphylococcus aureus is one of the primary pathogenic agents found in cheeses produced with raw milk. Some strains of S. aureus are enterotoxigenic, possessing the ability to produce toxins responsible for staphylococcal food poisoning when present in contaminated foods. This study aimed to genotypically characterize, assess the antimicrobial resistance profile, and examine the enterotoxigenic potential of strains of S. aureus isolated from artisanal colonial cheese. Additionally, a bacterial diversity assessment in the cheeses was conducted by sequencing the 16S rRNA gene. The metataxomic profile revealed the presence of 68 distinct species in the cheese samples. Fifty-seven isolates of S. aureus were identified, with highlighted resistance to penicillin in 33% of the isolates, followed by clindamycin (28%), erythromycin (26%), and tetracycline (23%). The evaluated strains also exhibited inducible resistance to clindamycin, with nine isolates considered multidrug-resistant (MDR). The agr type I was the most prevalent (62%) among the isolates, followed by agr type II (24%). Additionally, ten spa types were identified. Although no enterotoxins and their associated genes were detected in the samples and isolates, respectively, the Panton-Valentine leukocidin gene (lukS-lukF) was found in 39% of the isolates. The presence of MDR pathogens in the artisanal raw milk cheese production chain underscores the need for quality management to prevent the contamination and dissemination of S. aureus strains.

Molecular characterization and antibiotic resistance of Staphylococcus aureus strains isolated from patients with diarrhea in Korea between the years 2007 and 2022

To investigate the molecular characteristics and antibiotic resistance of Staphylococcus aureus isolates from patients with diarrhea in Korea, 327 S. aureus strains were collected between 2007 and 2022. The presence of staphylococcal enterotoxin (SE) and toxic shock syndrome toxin-1 (TSST-1) genes in S. aureus isolates was determined by PCR. The highest expression of the TSST-1 gene was found in the GIMNO type (43.1% of GIMNO type). GIMNO type (Type I) refers to each staphylococcal enterotoxin (SE) gene gene (initials of genes): G = seg; I = sei; M = selm; N = seln; O = selo. Moreover, Type I isolates showed a significantly higher resistance to most antibiotics. A total of 195 GIMNO-type S. aureus strains were analyzed using multilocus sequence typing (MLST), and 18 unique sequence types (STs) were identified. The most frequent sequence type was ST72 (36.9%), followed by ST5 (22.1%) and ST30 (16.9%). Interestingly, ST72 strains showed a higher prevalence of MRSA than the other STs. In conclusion, our results were the first reported for S. aureus strains in Korea, which significantly expanded S. aureus genotype information for the surveillance of pathogenic S. aureus and may provide important epidemiological information to resolve several infectious diseases caused by S. aureus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01478-9.

Zoonotic linkage and environmental contamination of Methicillin-resistant Staphylococcus aureus (MRSA) in dairy farms: A one health perspective

Methicillin-Resistant Staphylococcus aureus (MRSA) is a ubiquitous public health challenge, with its prevalence in human, animal, and environmental interfaces posing significant concerns. This study aimed to characterize and detect the zoonotic linkages of MRSA within the cow-environment-human interfaces in dairy farms to address the One Health perspective. A comprehensive investigation, involving 636 samples (an equal number of raw milk and cow nasal swab samples, along with varying numbers of human nasal swab and environmental samples), revealed an overall MRSA prevalence of 13.4% (n = 271/636). Notably, environmental samples exhibited the highest prevalence (19.3%), emphasizing the potential role of farm surroundings in MRSA transmission, while the lowest prevalence was found in raw milk at 11.8% (n = 31/263). The prevalence in cow nasal swabs and human nasal swabs was 13.3% (n = 35/263) and 15.1% (n = 8/53), respectively. Multiplex PCR analysis revealed the presence of different Staphylococcal enterotoxin (SEa, SEb, SEc, and SEd), and exfoliative toxin-producing genes (Eta, Etb) within the MRSA isolates underlining their potential to induce public health threats. All MRSA isolates exhibited complete resistance to Oxacillin (100%) and Amoxicillin (100%), while the highest sensitivity was observed for Vancomycin (85.8%). Furthermore, these MRSA strains demonstrated varying degrees of resistance to other commonly used antimicrobial drugs, including Cefoxitin (75.3%), Ceftarolin (71.2%), Sulfamethoxazole-Trimethoprim (63.5%), Ciprofloxacin (60%), and Gentamicin (49.5%). Detection of MRSA in cow, human, and environmental samples within the same farm vicinity highlights the risk of zoonotic transmission of MRSA from cows to humans through environmental interfaces. Phylogenetic analysis of the mecA gene in MRSA isolates from all sources within the same farm revealed a high similarity index (>84%) among them suggesting a shared evolutionary origin. Moreover, the MRSA isolates from milk samples showed a close evolutionary relationship with isolates from Kenya and Brazil, while the isolates from humans and the environment displayed noticeable resemblance to isolates from several Asian countries. The findings emphasize the importance of collaborative efforts under the One Health framework to address this multifaceted issue and ensure the safety of our food supply and public health.

Jellyfish protein hydrolysates: Multifunctional bioactivities unveiled in the battle against diabetes, inflammation, and bacterial pathogenesis

This study investigates the multifunctional bioactivities of pepsin-hydrolyzed jellyfish by-products (Rhopilema hispidum and Lobonema smithii), focusing on their anti-α-glucosidase activity, anti-inflammatory effects, anti-bacterial properties, and ability to inhibit biofilm formation of Staphylococcus aureus. Our findings revealed that jellyfish protein hydrolysates, particularly from Rhopilema hispidum, exhibit significant anti-α-glucosidase activity, surpassing the well-known α-glucosidase inhibitor Acarbose. Furthermore, we demonstrated the anti-inflammatory capabilities of these hydrolysates in suppressing lipopolysaccharide (LPS)-induced nitric oxide production in murine macrophage cells. This effect was dose-dependent and non-cytotoxic, highlighting the hydrolysate potential in treating inflammation-related conditions. Regarding anti-bacterial activity, pepsin-hydrolyzed jellyfish selectively exhibited a potent effect against S. aureus, including Methicillin-susceptible and Methicillin-resistant strains. This activity was evident at minimum inhibitory concentrations (MIC) of 25 μg/mL for S. aureus ATCC10832, while a modest effect was observed against other Gram-positive strains. The hydrolysates effectively delayed bacterial growth dose-dependently, suggesting their use as alternative agents against bacterial infections. Most notably, pepsin-hydrolyzed jellyfish showed significant anti-biofilm activity against S. aureus. The umbrella section hydrolysate of Rhopilema hispidum was particularly effective, reducing biofilm formation through downregulating the icaA gene, crucial for biofilm development. Furthermore, the hydrolysates modulated the expression of the agrA gene, a key regulator in the pathogenesis of S. aureus. In conclusion, pepsin-hydrolyzed jellyfish protein hydrolysates exhibit promising multifunctional bioactivities, including anti-diabetic, anti-inflammatory, antibacterial, and anti-biofilm properties. These findings suggest their potential application in pharmaceutical and nutraceutical fields, particularly in managing diabetic risks, inflammation, bacterial infections, and combating the biofilm-associated pathogenicity of S. aureus.

In vitro selection of DNA aptamers against staphylococcal enterotoxin A

Staphylococcal enterotoxin A (SEA) is the most frequently reported in staphylococcal food poisoning (SFP) outbreaks. Aptamers are single-stranded nucleic acids that are seen as promising alternatives to antibodies in several areas, including diagnostics. In this work, systematic evolution of ligands by exponential enrichment (SELEX) was used to select DNA aptamers against SEA. The SELEX protocol employed magnetic beads as an immobilization matrix for the target molecule and real-time quantitative PCR (qPCR) for monitoring and optimizing sequence enrichment. After 10 selection cycles, the ssDNA pool with the highest affinity was sequenced by next generation sequencing (NGS). Approximately 3 million aptamer candidates were identified, and the most representative cluster sequences were selected for further characterization. The aptamer with the highest affinity showed an experimental dissociation constant (KD) of 13.36 ± 18.62 nM. Increased temperature negatively affected the affinity of the aptamer for the target. Application of the selected aptamers in a lateral flow assay demonstrated their functionality in detecting samples containing 100 ng SEA, the minimum amount capable of causing food poisoning. Overall, the applicability of DNA aptamers in SEA recognition was demonstrated and characterized under different conditions, paving the way for the development of diagnostic tools.

Staphylococcal food poisoning outbreaks occurred in Sicily (Italy) from 2009 to 2016

Notification of foodborne outbreaks has been mandatory in Europe since 2005, and surveillance is carried out along the entire food chain. Here we report the results obtained from laboratory investigations about four cases of foodborne outbreaks that occurred in Sicily between 2009 and 2016, deemed to be related to staphylococcal enterotoxins (SEs) and coagulase-positive Staphylococci (CPS) by the Local Public Health Authority. Primosale cheese samples were processed by culture methods for enumeration of CPS and immunoenzymatic assays for detection and differentiation of the SEs possibly contained in food samples. In all cases, the mistrusted foods were found to be contaminated by CPS at bacterial loads between 5 and 8 log CFU/g and contained SE type C (SEC). The reported data confirm the risk of staphylococcal food poisoning associated with the consumption of raw milk cheese. SEC is the most commonly occurring SE in goat milk and dairy products and the most represented enterotoxin in Sicilian dairy products. Our results highlighted the need for improving the current monitoring efficiency and implementing the available laboratory methods to collect more faithful epidemiological data on the current prevalence of staphylococcal toxins in the food chain, including SEs currently not detectable by validated analytical methods.

Distribution and prevalence of enterotoxigenic Staphylococcus aureus and staphylococcal enterotoxins in raw ruminants' milk: A systematic review

Enterotoxins produced by Staphylococcus aureus are a common cause of food poisoning, leading to significant gastrointestinal symptoms and even hospitalization. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched three electronic databases for studies on detection of staphylococcal enterotoxins or enterotoxigenic S. aureus in raw ruminant milk. The 128 studies included in this systematic review showed a worldwide distribution of studies on staphylococcal enterotoxins and enterotoxigenic S. aureus, with an increase in the number from 1980 to 2021, a shift in detection methods from enterotoxins to enterotoxin genes, and a preponderance of studies from Europe and South America. Most studies focused on milk from individual animals with mastitis, especially cattle. Based on 24 studies, the within-herd prevalence of enterotoxigenic S. aureus in raw milk samples was 11.6%. Many studies failed to report the health status of sampled animals, or the numerator and denominator data needed for prevalence calculation. Cultural and legislative differences, economic status, diagnostic capabilities, and public awareness are all likely factors contributing to the observed distribution of studies. Our review highlighted a significant gap in quality and completeness of data reporting, which limits full assessment of prevalence and distribution of hazards posed by raw milk.

Isolation and genetic characterization of Staphylococcus aureus from wild animal feces and game meats

The populations of Japanese deer and boar have increased dramatically and have a serious impact on farming and mountain villages. Although the Japanese government promotes the use of captured wild animals, game meat is not subject to sanitary control considering that it is not subject to meat inspection or quality control. Here, we have attempted to isolate Staphylococcus aureus, a typical foodborne pathogen, as a part of an investigation of contamination in the meats of wild animals and their processing stages. We examined 390 samples of deer feces, 117 samples of wild boar feces, and 75 samples of disemboweled deer meat for isolation of S. aureus; ultimately, 30 (positive rate: 7.7%), 2 (1.7%), and 21 (28.0%) strains were isolated, respectively, from the samples. The genome sequences of these isolates were analyzed and were subjected to multilocus sequence typing. We identified 12 new sequence types (STs) and a dominant population of S. aureus with a characteristic genetic background in wild animals, namely, the ST groups derived from CC121 (number of strains = 39). These strains did not harbor the enterotoxin gene or only harbored egc-related enterotoxin, which is of low involvement in Staphylococcal food poisoning. However, one ST2449 strain, which produces causative enterotoxins, was isolated from a deer's feces. Since there are several common STs isolated from feces and dismembered meat and because fecal contamination during dismemberment is suspected, continuous monitoring and guidance for improving sanitary management conditions during processing and handling of the meat are highly warranted with immediate effect.

Coordination of prophage and global regulator leads to high enterotoxin production in staphylococcal food poisoning-associated lineage

Staphylococcus species in food produce Staphylococcal enterotoxins (SEs) that cause Staphylococcal food poisoning (SFP). More than 20 SE types have been reported, among which Staphylococcal enterotoxin A (SEA) has been recognized as one of the most important SEs associated with SFP. However, the regulatory mechanisms underlying its production remain unclear. Previously, we identified a major SFP clone in Japan, CC81 subtype-1, which exhibits high SEA production. In this study, we attempted to identify the factors contributing to this phenomenon. Thus, we demonstrated that the attenuation of the activity of endogenous regulator, Staphylococcal accessory regulator S (SarS), and the lysogenization of a high SEA-producing phage contributed to this phenomenon in CC81 subtype-1. Furthermore, our results indicated that SarS could directly bind to the promoter upstream of the sea gene and suppress SEA expression; this low SarS repression activity was identified as one of the reasons for the high SEA production observed. Therefore, we revealed that both exogenous and endogenous factors may probably contribute to the high SEA production. Our results confirmed that SE production is a fundamental and critical factor in SFP and clarified the associated production mechanism while enhancing our understanding as to why a specific clone frequently causes SFP.

IMPORTANCE

The importance of this study lies in its unveiling of a molecular regulatory mechanism associated with the most important food poisoning toxin and the evolution of Staphylococcal food poisoning (SFP)-associated clone. SFP is primarily caused by Staphylococcus aureus, with Staphylococcal enterotoxin A (SEA) being commonly involved in many cases. Thus, SEA has been recognized as a major toxin type. However, despite almost a century since its discovery, the complete mechanism of SEA production is as yet unknown. In this study, we analyzed an SEA-producing SFP clone isolated in East Asia and discovered that this strain, besides acquiring the high SEA-producing phage, exhibits remarkably high SEA production due to the low activity of SarS, an intrinsic regulatory factor. This is the first report documenting the evolution of the SFP clone through the coordinated action of exogenous mobile genetic factors and endogenous regulators on this notorious toxin.

Side-stream lignins: Potential antioxidant and antimicrobial agents in milk

In recent years, lignin has drawn increasing attention due to its intrinsic antibacterial and antioxidant activities, biodegradability, and biocompatibility. Yet, like several other biogenic structures, its compositional heterogeneity represents a challenge to overcome. In addition, there are few studies regarding food applications of lignin. Herein, we evaluate the antimicrobial and antioxidant effects of lignin from two different sources. These lignins were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) and hydrogen nuclear magnetic resonance (1H NMR) spectroscopies. Their antibacterial and antioxidant capacities (DPPH and Folin-Ciocalteu methods) were also investigated. Susceptibility tests were performed with the minimal inhibitory (MIC) and bactericidal (MBC) concentrations using the micro-broth dilution technique. Kraft lignin presented higher radical-scavenging and antibacterial activities than alkali lignin, indicating the dependence of antioxidant and antibacterial activities on the precursor biomass. Scanning electron microscopy shows morphologic changes in the bacteria after exposure to lignin, while confocal microscopy suggests that kraft lignin has affinity towards bacterial surfaces and the ability to cause cell membrane destabilization. Lignin inhibited the growth of Staphylococcus aureus and Salmonella Enteritidis in skimmed milk, herein taken as food model. Our results suggest that lignins are promising candidates for green additives to improve quality and safety within the food chain.

Rapid Antibacterial Activity Assessment of Chimeric Lysins

Various chimeric lysins have been developed as efficacious antibiotics against multidrug-resistant bacteria, but direct comparisons of their antibacterial activities have been difficult due to the preparation of multiple recombinant chimeric lysins. Previously, we reported an Escherichia coli cell-free expression method to better screen chimeric lysins against Staphylococcus aureus, but we still needed to increase the amounts of expressed proteins enough to be able to detect them non-isotopically for quantity comparisons. In this study, we improved the previous cell-free expression system by adding a previously reported artificial T7 terminator and reversing the different nucleotides between the T7 promoter and start codon to those of the T7 phage. The new method increased the expressed amount of chimeric lysins enough for us to detect them using Western blotting. Therefore, the qualitative comparison of activity between different chimeric lysins has become possible via the adjustment of the number of variables between samples without protein purification. We applied this method to select more active chimeric lysins derived from our previously reported chimeric lysin (ALS2). Finally, we compared the antibacterial activities of our selected chimeric lysins with reported chimeric lysins (ClyC and ClyO) and lysostaphin and determined the rank orders of antibacterial activities on different Staphylococcus aureus strains in our experimental conditions.

Biological characterization and genomic analysis of a novel methicillin-resistant Staphylococcus aureus phage, SauPS-28

Staphylococcus aureus, a representative gram-positive bacterium, is a common infectious pathogen widely present in the natural environment. The increasing application of antibiotics is witnessing an increment in the number of clinically resistant strains (such as methicillin-resistant S. aureus [MRSA]), which has posed a great challenge to antimicrobial therapy. In this study, a novel MRSA phage, SauPS-28, was isolated from the lake water of the Guangxi Zhuang Autonomous Region. This phage has an incubation period of approximately 30 min, a lysis period of approximately 40 min, and a burst size of approximately 25 PFU/cell. The isolated phage exhibited good biological stability at a pH range of 6.0-9.0 and temperature range of 4°C-37°C. In addition, the identification of an elongated tail using transmission electron microscopy confirmed that SauPS-28 belongs to the long-tailed phage family. Whole-genome sequencing analysis revealed that SauPS-28 has a 43,286-bp-long genome with 31.03% G + C content. Moreover, SauPS-28 exhibited 95.69% sequence identity with ECel-2020k, while the query coverage was only 66%, which is a newly discovered phage. Whole-genome functional annotation results revealed that SauPS-28 had 68 open reading frames (ORFs). Of these, 30 ORFs are unknown proteins. The results suggest that SauPS-28 could be a lysogenic phage strain. This study thus provides preliminary data to conduct further in-depth analysis of the mechanism of phage-host interaction and provides a reference value for phage therapy.IMPORTANCEIn recent years, drug-resistant bacterial infections have become increasingly serious. As a kind of virus with the ability to infect and lyse drug-resistant bacteria, phage is expected to be a new therapeutic method. In this study, we isolated and purified a new methicillin-resistant Staphylococcus aureus bacteriophage SauPS-28, studied a series of biological characteristics of the bacteriophage, analyzed the genome and structural proteome data of the bacteriophage, and provided reference data for further study of the interaction mechanism between bacteriophage and host bacteria and promoted new antibacterial strategies.

De novo design of a protein binder against Staphylococcus enterotoxin B

Staphylococcus enterotoxin B (SEB) interacts with MHC-II molecules to overactivate immune cells and thereby to produce excessive pro-inflammatory cytokines. Disrupting the interactions between SEB and MHC-II helps eliminate the lethal threat posed by SEB. In this study, a de novo computational approach was used to design protein binders targeting SEB. The MHC-II binding domain of SEB was selected as the target, and the possible promising binding mode was broadly explored. The obtained original binder was folded into triple-helix bundles and contained 56 amino acids with molecular weight 5.9 kDa. The interface of SEB and the binder was highly hydrophobic. ProteinMPNN optimization further enlarged the hydrophobic region of the binder and improved the stability of the binder-SEB complex. In vitro study demonstrated that the optimized binder significantly inhibited the inflammatory response induced by SEB. Overall, our research demonstrated the applicability of this approach in de novo designing protein binders against SEB, and thereby providing potential therapeutics for SEB induced diseases.

Prevalence of virulence- and antibiotic resistance-associated genotypes and phenotypes in Staphylococcus aureus strains from the food sector compared to clinical and cow mastitis isolates

Background

Infections by the pathogen Staphylococcus aureus currently represent one of the most serious threats to human health worldwide, especially due to the production of enterotoxins and the ability to form biofilms. These structures and the acquisition of antibiotic resistance limit the action of antibiotics and disinfectants used to combat this microorganism in the industry and the clinic.

Methods

This work reports a comparative phenotypic and genotypic study of 18 S. aureus strains from different origins: clinical samples, milk from mastitic cows and food industry surfaces, most of which were isolated in Northern Spain.

Results

Genetically, the strains were very diverse but, in most cases, a closer proximity was observed for those from the same source. Notably, the average number of virulence genes was not significantly different in strains from the food sector. Of the 18 strains, 10 coded for at least one enterotoxin, and four of them carried 6 or 7 enterotoxin genes. The latter were all veterinary or clinical isolates. Most strains carried prophages, plasmids and/or pathogenicity islands. Regarding antibiotic resistance, although phenotypically all strains showed resistance to at least one antibiotic, resistance genes were only identified in 44.5% of strains, being mastitis isolates those with the lowest prevalence. Virulence-related phenotypic properties such as haemolytic activity, staphyloxanthin production, biofilm-forming capacity and spreading ability were widely distributed amongst the isolates.

Conclusions

Our results indicate that production of virulence factors, antibiotic resistance and biofilm formation can be found in S. aureus isolates from diverse environments, including the food industry, although some of these traits are more prevalent in strains isolated from infections in cows or humans. This emphasizes on the importance of monitoring the spread of these determinants not only in samples from the clinical environment, but also along the food chain, a strategy that falls under the prism of a one-health approach.

Comparative genomic analysis of antibiotic resistance and virulence genes in Staphylococcus aureus isolates from patients and retail meat

Introduction

Staphylococcus aureus is a significant human pathogen that poses a threat to public health due to its association with foodborne contamination and a variety of infections. The factors contributing to the pathogenicity of S. aureus include virulence, drug resistance, and toxin production, making it essential to monitor their prevalence and genetic profiles. This study investigated and compared the genomic characteristics of S. aureus isolates from retail meat and patients in Saudi Arabia.

Methods

A total of 136 S. aureus isolates were obtained between October 2021 and June 2022:84 from patients and 53 from meat samples in Riyadh, Saudi Arabia. S. aureus isolates were identified using conventional methods and MALDI-TOF MS, and methicillin-resistant S. aureus (MRSA) was identified using VITEK2 and BD Phoenix systems. MRSA was confirmed phenotypically using chromogenic agar, and genotypically by detecting mecA. Genomic data were analyzed using BactopiaV2 pipeline, local BLAST, and MLST databases.

Results

Antibiotic resistance genes were prevalent in both meat and patient S. aureus isolates, with high prevalence of tet38, blaZ, and fosB. Notably, all S. aureus isolates from patients carried multidrug-resistant (MDR) genes, and a high percentage of S. aureus isolates from meat also harbored MDR genes. Phenotypically, 43% of the S. aureus isolates from meat and 100% of the patients' isolates were MDR. Enterotoxin genes, including selX, sem, and sei, exhibited high compatibility between meat and patient S. aureus isolates. Virulence genes such as cap, hly/hla, sbi, and isd were found in all S. aureus isolates from both sources.

Conclusion

Our study established a genetic connection between S. aureus isolates from meat and patients, showing shared antibiotic resistance and virulence genes. The presence of these genes in meat derived isolates underscores its role as a reservoir. Genomic relatedness also suggests potential transmission of resistance between different settings. These findings emphasize the necessity for a comprehensive approach to monitor and control S. aureus infections in both animals and humans.

Detection of Staphylococcus Isolates and Their Antimicrobial Resistance Profiles and Virulence Genes from Subclinical Mastitis Cattle Milk Using MALDI-TOF MS, PCR and Sequencing in Free State Province, South Africa

Staphylococcus species are amongst the bacteria that cause bovine mastitis worldwide, whereby they produce a wide range of protein toxins, virulence factors, and antimicrobial-resistant properties which are enhancing the pathogenicity of these organisms. This study aimed to detect Staphylococcus spp. from the milk of cattle with subclinical mastitis using MALDI-TOF MS and 16S rRNA PCR as well as screening for antimicrobial resistance (AMR) and virulence genes. Our results uncovered that from 166 sampled cows, only 33.13% had subclinical mastitis after initial screening, while the quarter-level prevalence was 54%. Of the 50 cultured bacterial isolates, MALDI-TOF MS and 16S rRNA PCR assay and sequencing identified S. aureus as the dominant bacteria by 76%. Furthermore, an AMR susceptibility test showed that 86% of the isolates were resistant to penicillin, followed by ciprofloxacin (80%) and cefoxitin (52%). Antimicrobial resistance and virulence genes showed that 16% of the isolates carried the mecA gene, while 52% of the isolates carried the Lg G-binding region gene, followed by coa (42%), spa (40%), hla (38%), and hlb (38%), whereas sea and bap genes were detected in 10% and 2% of the isolates, respectively. The occurrence of virulence factors and antimicrobial resistance profiles highlights the need for appropriate strategies to control the spread of these pathogens.

Red foxes (Vulpes vulpes) as a specific and underappreciated reservoir of resistant and virulent coagulase-positive Staphylococcus spp. strains

The aim of the study was to analyze the presence of coagulase-positive Staphylococcus in swabs collected from red foxes and to characterize the drug resistance and virulence of these bacteria. In total, 415 rectal and oral swabs were collected, and coagulase-positive strains of S. pseudintermedius (n = 104) and S. aureus (n = 27) were identified using multiplex-PCR and MALDI TOF MS. Subsequent analyses showed the highest phenotypic resistance of the strains to penicillin (16.8%) and tetracycline (30.5%) confirmed by the presence of the blaZ, tetM, and tetK genes. Slightly lower resistance to erythromycin (6.9%), clindamycin (9.2%), gentamicin, streptogramins, rifampicin, nitrofurantoin, and sulphamethoxazol/trimetophrim was exhibited by single strains. Several virulence genes in a few different combinations were detected in S. aureus; LukE-LukD, and seB were the most frequent genes (37%), LukE-LukD, seB, and seC were detected in 11% of the strains, and PVL, etA, etB, and tst genes were present in two or single strains. The results of our research have confirmed that the red fox is an underestimated reservoir of coagulase-positive Staphylococcus strains, with approximately 50% of carriers of at least one resistance gene. In turn, 88.8% of the S. aureus strains had one or more virulence genes; therefore, this species of wildlife animals should be monitored as part of epidemiological surveillance.

Screening of antibiogram, virulence factors, and biofilm production of Staphylococcus aureus and the bio-control role of some probiotics as alternative antibiotics

Background

Food safety is a serious challenge in the face of increasing population and diminishing resources. Staphylococcus aureus is a critical foodborne pathogen characterized by its capability to secret a diverse range of heat-resistant enterotoxins. Antibiotic usage in dairy herds resulted in the occurrence of antimicrobial resistance (AMR) patterns among bacterial species, which were consequently transmitted to humans via dairy products. Lactic acid bacteria (LAB) produce bacteriocins, which provide an excellent source of natural antimicrobials with the further advantage of being environmentally friendly and safe.

Aim

Detection of multidrug resistance (MDR) S. aureus isolates in concerned samples, molecular characteristics, biofilm production, and the inhibitory role of LAB against it.

Methods

Random samples of raw milk and other dairy products were analyzed for S. aureus isolation. Phenotypic and genotypic assessment of AMR was performed, in addition to detection of classical enterotoxin genes of S. aureus. Finally, evaluation of the antimicrobial action of some Lactobacillus strains against S. aureus.

Results

Incidence rates of presumptive S. aureus in raw milk, Kariesh cheese, and yogurt samples were 50%, 40%, and 60%, respectively. The highest resistance of S. aureus was to Kanamycin (100%) and Nalidixic acid (89.3%), respectively. (78.66%) of S. aureus were MDR. 11.1% of S. aureus carried mecA gene. In concern with enterotoxins genes, PCR showed that examined isolates harbored sea with a percentage of (22.2%), while sed was found in (11.1%) of isolates. Regarding biofilm production, (88.88%) of S. aureus were biofilm producers. Finally, agar well diffusion showed that Lactobacillus acidophilus had the strongest antimicrobial action against S. aureus with inhibition zone diameter ranging from 18 to 22 mm.

Conclusion

There is a widespread prevalence of MDR S. aureus in raw milk and dairy products. Production of staphylococcal enterotoxins, as well as biofilm production are responsible for public health risks. Therefore, installing proper hygienic routines and harsh food safety policies at food chain levels is substantial.

Putative staphylococcal enterotoxin possesses two common structural motifs for MHC-II binding

Staphylococcus aureus has become a significant cause of health risks in humankind. Staphylococcal superantigens (SAgs) or enterotoxins are the key virulent factors that can exhibit acute diseases to severe life-threatening conditions. Recent literature reports S. aureus has steadily gained new enterotoxin genes over the past few decades. In spite of current knowledge of the established SAgs, several questions on putative enterotoxins are still remaining unanswered. Keeping that in mind, this study sheds light on a putative enterotoxin SEl26 to characterize its structural and functional properties. In-silico analyses indicate its close relation with the conventional SAgs, especially the zinc-binding SAgs. Additionally, important residues that are vital for the T-cell receptor (TcR) and major histocompatibility complex class II (MHC-II) interaction were predicted and compared with established SAgs. Besides, our biochemical analyses exhibited the binding of this putative enterotoxin with MHC-II, followed by regulating pro-inflammatory and anti-inflammatory cytokines.

Development of nanobodies against Staphylococcus enterotoxin B through yeast surface display

Staphylococcus enterotoxin B (SEB) is one of the primary virulence factors of Staphylococcus aureus but there is still a lack of targeted drugs. SEB activates immune cells via interacting with MHC-II on antigen-presenting cells, leading to the production of large amounts of pro-inflammatory cytokines. Blocking the interaction between SEB and MHC-II can avert the overactivation of immune cells. Nanobodies are the smallest functional antibodies that can bind stably to antigens. In this study, an ideal approach to obtain specific nanobodies without immunizing camelids was introduced. We constructed a library containing up to 5 × 108 nanobodies, and then screened those targeting SEB by using yeast surface display (YSD) technique and fluorescence-activated cell sorting (FACS). A total of 8 nanobodies with divergent complementarity-determining regions (CDRs) sequences were identified and one candidate Nb8 with high affinity to SEB was isolated. In vitro study demonstrated that Nb8 significantly inhibited SEB-induced inflammatory response. Molecular docking simulation indicated that the unique CDR3 sequence contributed to the binding of Nb8 to the MHC-II binding domain of SEB and accordingly cut off the connection between SEB and MHC-II. Our efforts contributed to the development of specific nanobodies for eliminating the threats of SEB.

Identification of the Enterotoxigenic Potential of Staphylococcus spp. from Raw Milk and Raw Milk Cheeses

This study aimed to genotypic and phenotypic analyses of the enterotoxigenic potential of Staphylococcus spp. isolated from raw milk and raw milk cheeses. The presence of genes encoding staphylococcal enterotoxins (SEs), including the classical enterotoxins (sea-see), non-classical enterotoxins (seg-seu), exfoliative toxins (eta-etd) and toxic shock syndrome toxin-1 (tst-1) were investigated. Isolates positive for classical enterotoxin genes were then tested by SET-RPLA methods for toxin expression. Out of 75 Staphylococcus spp. (19 Staphylococcus aureus and 56 CoNS) isolates from raw milk (49/65.3%) and raw milk cheese samples (26/34.7%), the presence of enterotoxin genes was confirmed in 73 (97.3%) of them. Only one isolate from cheese sample (1.3%) was able to produce enterotoxin (SED). The presence of up to eight different genes encoding enterotoxins was determined simultaneously in the staphylococcal genome. The most common toxin gene combination was sek, eta present in fourteen isolates (18.7%). The tst-1 gene was present in each of the analyzed isolates from cheese samples (26/34.7%). Non-classical enterotoxins were much more frequently identified in the genome of staphylococcal isolates than classical SEs. The current research also showed that genes tagged in S. aureus were also identified in CoNS, and the total number of different genes detected in CoNS was seven times higher than in S. aureus. The obtained results indicate that, in many cases, the presence of a gene in Staphylococcus spp. is not synonymous with the ability of enterotoxins production. The differences in the number of isolates with genes encoding SEs and enterotoxin production may be mainly due to the limit of detection of the toxin production method used. This indicates the need to use high specificity and sensitivity methods for detecting enterotoxin in future studies.

Synthesizing Carbon Quantum Dots via Hydrothermal Reaction to Produce Efficient Antibacterial and Antibiofilm Nanomaterials

This study aimed to synthesize antibacterial carbon quantum dots (SP-CDs) from polyethyleneimine and spermidine via hydrothermal reaction. It was revealed that SP-CDs, with small size (7.18 nm) and high positive charge (+31.15 mV), had good fluorescence properties and lots of amino groups on their surfaces. The inhibition effect of SP-CDs on Staphylococcus aureus was better than that towards Escherichia coli, and the SP-CDs also had an inhibitory effect on multi-drug-resistant E. coli. The mechanism of SP-CDs shows that the SP-CDs were adsorbed on the surface of the negatively charged cell membrane through electrostatic interaction. SP-CDs can cause changes in membrane permeability, resulting in a shift of the cell membrane from order to disorder and the decomposition of chemical components, followed by the leakage of cell contents, resulting in bacterial death. SP-CDs can also significantly inhibit biofilm formation, destroy mature biofilms and reduce the number of living cells. Moreover, SP-CDs had negligible antimicrobial resistance even after 18 generations of treatment. This study proves that SP-CDs effectively inhibit the proliferation of foodborne pathogens, providing new feasibility for the application of carbon-based nanomaterials in the food industry.

Comparison of genotyping methods and toxin gene profiles of Staphylococcus aureus isolates from clinical specimens

Staphylococcus aureus is a frequent cause of infections worldwide. Methicillin-resistant S. aureus (MRSA) is one of the main causes of Gram-positive infections, and methicillin-susceptible strains (MSSA) primarily colonize and infect community hosts. Multiple virulence factors are involved, with toxins playing a significant role in several diseases. In this study, we assess the prevalence of toxin genes in 89 S. aureus clinical isolates (31 MRSA and 58 MSSA). We evaluated the discriminatory power of the association of internal transcribed spacer-PCR (ITS-PCR) and 3'- end coa gene ( coa-PCR) when compared with other more commonly used and costly techniques. The isolates showed a high level of genetic diversity, and toxins were found in all the isolates. While most toxin classes displayed no statistically significant correlations and were equally distributed in isolates regardless of their resistance status, classic enterotoxins ( sea-see) showed a positive correlation with MSSA isolates. The combination of coa-PCR with ITS-PCR showed a discriminatory index of 0.84, discriminating 22 genotypes that agree with previously determined data by PFGE and MLST. This association between the two PCR-based methods suggests that they can be useful for an initial molecular epidemiological investigation of S. aureus in hospitals, providing significant information while requiring fewer resources.

Enterotoxigenic and Antimicrobic Susceptibility Profile of Staphylococcus aureus Isolates from Fresh Cheese in Croatia

Certain Staphylococcus aureus strains harbour staphylococcal enterotoxin genes and hence can produce enterotoxin during their growth in food. Therefore, food can be a source of staphylococcal food poisoning, one of the most common food-borne diseases worldwide. Epidemiological data show that S. aureus is often present in raw milk cheeses, and consequently, cheeses are often the source of staphylococcal food poisoning outbreaks. The aim of this study was to determine the phenotypic characteristics of S. aureus isolates from fresh cheese, including antibiotic susceptibility; the presence of classical sea-see enterotoxin genes through molecular methods; and the isolate's ability to produce SEA-SEE enterotoxins in vitro through reversed passive latex agglutination. A total of 180 coagulase-positive staphylococci were isolated from 18 out of 30 cheese samples, and 175 were confirmed as S. aureus through latex agglutination and API STAPH tests. All isolates possessed phenotypic characteristics typical for S. aureus, with certain variations in the egg yolk reaction (18.3% of the isolates showed a weak reaction and 28% no reaction at all) and haemolysis pattern (36.6% of the isolates produced double-haemolysis and 4.6% were non-haemolytic). Antibiotic resistance was observed in 1.1% of the isolates and to mupirocin only. Real-time PCR detected the sec gene in 34 (19.4%) isolates, but most isolates (80.6%) were not enterotoxigenic. For all 34 (19.4%) strains that carried the sec gene, the RPLA method detected the production of the SEC enterotoxin in vitro. For those enterotoxigenic strains, the possibility of enterotoxin production in fresh cheese could not be ruled out.

Engineered probiotic Lactobacillus plantarum WCSF I for monitoring and treatment of Staphylococcus aureus infection

IMPORTANCE

Bacterial infection and the emergence of drug-resistant strains are major problems in clinical treatment. Staphylococcus aureus, which typically infects the skin and blood of animals, is also a potential intestinal pathogen that needs to be addressed by the emergence of a new treatment approach. Probiotic therapy is the most likely alternative to antibiotic therapy to solve the problem of bacterial drug resistance in clinical practice. In this study, the engineered Lactobacillus plantarum can not only sense the signal AIP to detect S. aureus but also kill S. aureus by secreting the lysostaphin enzyme. Our strategy employed an Agr quorum-sensing genetic circuit to simultaneously detect and treat pathogenic bacteria, which provided a theoretical possibility for solving practical clinical bacterial infection cases in the future.

Prevalence and Characterization of Staphylococcus aureus Isolated from Retail Raw Milk Samples in Chennai, India

Milk is an important source of food, and it is also a nutrient-rich medium, which can harbor multiple microorganisms. Staphylococcus aureus is an important foodborne pathogen in food-producing animals, and there have been many reports on its infection and antimicrobial resistance (AMR), which has significant global public health concerns. This study was designed to isolate, characterize, and analyze the AMR pattern of S. aureus from milk samples collected in Chennai, India. A total of 259 raw milk samples from 3 groups: dairy farms, local vendors, and retail outlets were analyzed, and it was found that 34% (89/259) were positive for S. aureus. Positive isolates were further characterized by pulsed-field gel electrophoresis and isolates recovered from different sources, study areas, and locations showed high genetic diversity with no similarity. The presence of AMR has been further assessed by phenotypic methods as per CLSI-M100 performance standards, and all the isolates were susceptible to ampicillin/sulbactam, mupirocin, and tylosin. Additionally, all of the isolates were resistant to ampicillin. There were 28 isolates categorized as multidrug-resistant, which showed resistance to more than 2-3 classes of antimicrobials. This is the first report of inducible clindamycin resistance and mupirocin sensitivity pattern from S. aureus isolates recovered from milk. This study established the occurrence varied with genetic diversity in the isolates prevalent in the study area and divergence pattern of AMR S. aureus. The AMR in these isolates and with methicillin-resistant S. aureus could pose a serious threat to food safety and economic implications.

Metal-ruthenium complex based on dipyridylamine group as membrane-active antibacterial agent effectively decrease the development of drug-resistance on Staphylococcus aureus

Staphylococcus aureus (S. aureus), one of the Gram-positive bacteria, is easily to develop drug-resistance. Drug-resistant S. aureus infection leads to high morbidity and mortality. The complexes, namely [Ru(dpa)2(PSPIP)](PF6)2 (Ru1), [Ru(dpa)2(TSPIP)](PF6)2 (Ru2), and [Ru(dpa)2(TBPIP)](PF6)2 (Ru3), were synthesized using 2, 2'-dipyridylamine as an auxiliary ligand and three main ligands PSPIP, TSPIP, TBPIP. In vitro studies demonstrated that the Ru1-3 exhibited excellent antibacterial activity against S. aureus while showing low hemolytic toxicity to rabbit red blood cells. Notably, Ru3 was found to disrupt the bacterial cell membrane and alter its permeability through fluorescence staining and scanning electron microscopy (SEM) analysis. Furthermore, Ru3 displayed low toxicity in G. mellonella Larvae. Ru3 exhibited good activity against S. aureus in G. mellonella Larvae infection model and mouse skin infection model.To some extent, Ru3 inhibited biofilm formation on S. aureus as well as hemolytic toxin production, thereby attenuating the development of drug resistance without cross-resistance with other antibiotics. In addition, complex Ru3 exhibited a synergistic effect when combined with antibiotics amikacin, kanamycin, tobramycin and chloramphenicol, making it a valuable antibiotics adjuvant.

Microbial Profile of Fresh and Semicooked Nile Tilapia (Oreochromis niloticus) and Hygienic Practice of Fish Handlers in Hawassa, Ethiopia

Despite its high nutritional quality, fish is a highly perishable food item. This study aimed at assessing the microbial quality and safety of fresh and semicooked Nile tilapia fish fillets and the food safety practices of fish handlers in Hawassa City. The microbial load of 40 for each of raw and semicooked fillet samples was estimated by the standard plate count method, and the dominant flora as well as common bacterial pathogens were identified following phenotypic procedures. Moreover, a survey was conducted to assess the hygienic conditions and food safety practices of 30 fish handlers. The mean microbial load of the raw fillet samples in log10CFUg-1 was 8.42 for aerobic mesophilic bacteria (AMBC), 2.52 for total coliforms (TCC), and 3.41 for a count of staphylococci (CS). On the other hand, the respective parameters for the semicooked fillets in log10CFUg-1 were 6.68 (AMBC), 2.52 (TCC), and 3.17 (CS). The mean AMBC of all the fresh raw fillet samples exceeded the recommended maximum permissible limits. The mean SC of raw fillets from three of the eight vendors and one semicooked fillet were at a potentially hazardous level (>4 log units). Moreover, Salmonella species were isolated from 30% to 25% of raw and semicooked samples, respectively. The mesophilic bacterial flora of both types of samples was dominated by Bacillus species, Salmonella species, E coli, and Staphylococcus species. Most fish handlers did not practice hygienic food handling and lacked basic sanitation amenities like clean water and soap for hand washing. Moreover, nearly all the fish handlers did not have any formal education. These findings call for public health intervention measures like the provision of training in good hygienic practices and certification for fish vendors in the chain.

The Enterotoxin Gene Profiles and Enterotoxin Production of Staphylococcus aureus Strains Isolated from Artisanal Cheeses in Belgium

A Staphyloccoccus aureus is one of the leading causes of food poisoning outbreaks (FPOs) worldwide. Staphylococcal food poisoning (SFP) is induced by the ingestion of food containing sufficient levels of staphylococcal enterotoxins (SEs). Currently, 33 SEs and SE-like toxins (SEls) have been described in the literature, but only five named "classical" enterotoxins are commonly investigated in FPOs due to lack of specific routine analytical techniques. The aims of this study were to (i) establish the genetic profile of strains in a variety of artisanal cheeses (n = 30) in Belgium, (ii) analyze the expression of the SE(l)s by these strains and (iii) compare the output derived from the different analytical tools. Forty-nine isolates of S. aureus were isolated from ten Belgian artisanal cheeses and were analyzed via microbiological, immunological, liquid chromatography mass spectrometry, molecular typing and genetic methods. The results indicated that classical SEs were not the dominant SEs in the Belgian artisanal cheeses that were analyzed in this study, and that all S. aureus isolates harbored at least one gene encoding a new SE(l). Among the new SE(l)s genes found, some of them code for enterotoxins with demonstrated emetic activity and ecg-enterotoxins. It is worth noting that the involvement of some of these new SEs has been demonstrated in SFP outbreaks. Thus, this study highlighted the importance of the development of specific techniques for the proper investigation of SFP outbreaks.

Stability and emetic activity of enterotoxin like X (SElX) with high carrier rate of food poisoning Staphylococcus aureus

In order to analyze and clarify the thermal stability of food poisoning Staphylococcus aureus (S. aureus) enterotoxin-like X (SElX) and the biological characteristics of digestive enzymes, and to evaluate the risk of S. aureus carrying selx gene in food poisoning, the selx gene carrying rates of 165 strains isolated from 95 food poisoning events from 2006 to 2019 were first statistically analyzed. Subsequently, the purified recombinant SElX protein was digested and heated, and the superantigen activity was verified with mouse spleen cells and peripheral blood mononuclear cells of kittens. At the same time, the emetic activity and toxicity of SElX were evaluated using the kitten vomiting animal model, mice toxin model and in vitro cell models. The results showed the selx gene carrying rate of 165 food poisoning S. aureus strains was 90.30 %. SElX had significant resistance to heat treatment and pepsin digestion (pH = 4.0 and pH = 4.5), and had good superantigen activity and emetic activity. However, there is no significant lethal effect on mice and no significant toxicity to cells. Importantly, we found that SElX had an inhibitory effect on acidic mucus of goblet cells in various segments of the small intestine. The present study investigated the stability of SElX, and confirmed the emetic activity of SElX by establishing a kitten vomiting model for the first time, suggesting that SElX is a high risk toxin of food poisoning, which will provide new ideas for the prevention and control of S. aureus food poisoning.

A Single-Laboratory Performance Evaluation of MALDI-TOF MS in Rapid Identification of Staphylococcus aureus, Cronobacter sakazakii, Vibrio parahaemolyticus, and Some Closely Related Bacterial Species of Public Health Importance

BACKGROUND

Staphylococcus is a genus of Gram-positive bacteria, known to cause food poisoning and gastrointestinal illness in humans. Additionally, the emergence of methicillin-resistant S. aureus (MRSA) strains has caused a major health care burden worldwide. Cronobacter is a group of Gram-negative bacteria that can survive in extreme dry conditions. Cronobacter sakazakii is known to contaminate powdered infant formula and cause life-threatening infections in neonates. Vibrio is a genus of human-pathogenic Gram-negative bacteria that can cause foodborne illness by consuming undercooked or raw seafood. Vibrio parahaemolyticus can cause serious gastrointestinal disease in humans. Thus, rapid identification of Staphylococcus spp., Cronobacter spp., and Vibrio spp. is crucial for the source tracking of contaminated food, as well as to measure the transmission dynamics of these bacterial pathogens causing foodborne diseases and outbreaks.

OBJECTIVE

This single-laboratory performance evaluation study used the VITEK MS system to evaluate the potential of MALDI-TOF MS technology for rapid identification of S. aureus-like, C. sakazakii-like, and V. parahaemolyticus-like isolates of public health importance.

METHOD

A total of 226 isolates recovered from various food, environmental surveillance samples, and other sources were identified by bioMérieux VITEK 2 and VITEK MS systems as Staphylococcus spp., Cronobacter spp., and Vibrio spp. Five American Type Culture Collection (ATCC) reference Gram-positive and Gram-negative bacterial isolates were also tested to complete the study. In addition, for some Staphylococcus spp. isolates, whole genome sequencing (WGS) and DNA sequencing of 16S rRNA partial region were also performed for species identification.

RESULTS

The VITEK MS system was able to provide species identification to all 96 isolates of Staphylococcus spp. and to all 29 isolates of Vibrio spp. examined with a high confidence value (99.9%). Similarly, species identification was observed for the majority of spots (245 of 303) for the 101 Cronobacter spp. isolates (∼82.0%) with a high confidence value (99.9%), and genus level identification was noticed for the rest of the Cronobacter spp. isolates (18.0%; 58 of the 303 spots) analyzed. Species identification data generated by VITEK 2 system were comparable to data obtained by the VITEK MS system.

CONCLUSIONS

The VITEK MS system is a reliable high-throughput platform that can rapidly identify Staphylococcus, Vibrio, and Cronobacter to the genus level, as well as S. aureus, C. sakazakii, V. parahaemolyticus, and other closely related foodborne isolates and bacterial isolates from additional sources, in most cases.

HIGHLIGHTS

The VITEK MS system can be used in the rapid genus and species identification of human-pathogenic Staphylococcus spp., Cronobacter spp., and Vibrio spp. isolates.

Characterization and pathogenicity of multidrug-resistant coagulase-negative Staphylococci isolates in chickens

The pathogenic potential of vancomycin and methicillin-resistant coagulase-negative Staphylococci (VMRCoNS) on Egyptian poultry farms has received little attention. Therefore, this study aims to study the prevalence of CoNS in imported poultry flocks and commercial poultry farms, evaluate the presence of virulence and antibiotic resistance genes (sea, seb, sec, sed, see, and mecA), and assess their pathogenicity in broiler chicks. Seven species were identified among 25 isolates, such as 8 S. gallinarum, 5 S. saprophyticus, 5 S. chromogens, 3 S. warneri, 2 S. hominis, 1 S. caprae, and 1 S. epidermidis. All isolates were resistant to clindamycin, doxycycline, vancomycin, methicillin, rifampicin, and penicillin. The mecA gene was confirmed in 14 isolates, while the sed gene was revealed in seven isolates. Commercial 1-day-old Ross broiler chicks were divided into eight groups of three replicates (10 birds/group): group Ӏ was negative control; groups (П, Ш, IV, V, VI, VII, and VIII) were subcutaneously inoculated with 108 CFUml-1 of S. hominis, S. caprae, S. epidermidis, S. gallinarum, S. chromogens, S. warneri, and S. saprophyticus, respectively. Groups VIII and V had mortality rates of 100% and 20%, respectively, with no evidence of mortalities in the other groups. The highest re-isolation of CoNS species was recorded in groups VII, VIII, and V. Postmortem and histopathological examination revealed the common presence of polyserositis in the internal organs, and hepatic and myocardial necrosis in groups IV, V, and VI. These findings revealed the pathogenic potential of CoNS, so special attention must be directed toward their public health impact.

Fast detection of Staphylococcus aureus using thiol-functionalized WS2 quantum dots and Bi2O2Se nanosheets hybrid through a fluorescence recovery mechanism

Ultrafast and sensitive detection of Staphylococcus aureus (S. aureus), a harmful Gram-positive human pathogenic bacterium, by two-dimensional layered materials continues to be a challenge. Herein, we have studied the sensing of S. aureus using a tungsten disulfide (WS2) quantum dot (QD) and bismuth oxyselenide (Bi2O2Se) nanosheet (NS) hybrid through their unique optical functionalities. The WS2 QDs of a mean diameter of 2.5 nm were synthesized by liquid exfoliation. Due to the quantum confinement and functional groups, the WS2 QDs exhibit high fluorescence (FL) yield under UV excitation. The addition of Bi2O2Se NSs resulted in the adsorption of WS2 QDs on their surface, resulting in quenching of the FL emission due to nonfluorescent complex formation between the WS2 QDs and Bi2O2Se NSs. A specific sequencing single-standard DNA (ssDNA) aptamer, which identifies and explicitly binds with S. aureus, was attached to the defect sites of the WS2 QDs for selective detection. The thiol-modified ssDNA aptamers attach covalently to the WS2 QD defect sites, which was confirmed by Raman and X-ray photoelectron spectroscopy (XPS). The interaction of S. aureus with the aptamer functionalized WS2 QDs weakens the van der Waals interaction between the WS2 QDs and Bi2O2Se NSs, which results in the detachment of the WS2 QDs from the Bi2O2Se NS surface and restores the FL intensity of the WS2 QDs, thus allowing the efficient detection of S. aureus. Similar measurements with non-targeted bacteria show that the system is quite selective towards S. aureus. Our FL-based biosensor has a linear response in the range of 103-107 CFU mL-1 (colony formation unit mL-1) with a detection limit of 580 CFU mL-1. We have observed a fast response time of 15 minutes for sensing, which is superior to the previous reports. The proposed system was tested in human urine and can detect S. aureus in human urine samples selectively, proving its potential in real-life applications. The reported approach is versatile enough for sensing other biomolecules and metal ions by choosing suitable receptors.

Radiation processing of papad - A sustainable method to improve safety and shelf life

Papad is a popular traditional Indian snack food that is also consumed as an accompaniment to meals. The papad industry in India is predominantly a cottage industry, mainly run by women. Due to microbial contamination and infestation, papad has a shelf life of only a few months. However, increased domestic consumption and export requirements necessitate a longer shelf life. Chemical preservatives are generally added to increase shelf life. Our studies have shown that radiation processing (2 kGy) can be used to extend the shelf life. Unirradiated samples spoiled in three months with visible fungal growth and insect infestation. Irradiated (2 kGy) papad had a shelf life of one year, was sensorily acceptable, showed no microbial counts, and hence has great export potential.

Emerging challenges in maintaining marine food-fish availability and food safety

The marine finfish and crustaceans contribute immensely to human nutrition. Harvesting marine food-fish to meet the global demand has become a challenge due to reduction of the fishery areas and food safety hazards associated with increased pre-harvest and post-harvest contaminations. The causes of low fish availability and contaminations were reviewed following the published literature from 2000 to 2023. The marine fish yields are stressed due to spread of contaminants triggered by rising sea temperatures, transport of microorganisms by marine vessels across the oceans, anthropogenic activities leading to increase in the toxic microorganisms, and the entry of toxic chemicals and antibiotic residues into the seawater through rivers or directly. Processing adds pyrogenic chemicals to foods. The hazardous materials may accumulate in the food-fish, beyond tolerance limits permitted for human foods. While the research and control measures focus on minimizing the hazards due to pathogenic microorganisms and chemicals in market fish, there is less discussion on the unhealthy changes occurring in the oceans affecting the quantity and quality of food-fish, and the origins of microbial and chemical contaminations. This review examines the factors affecting availability of wild food-fish and increased contaminations. It aims to bridge the knowledge gaps between the spread of hazardous agents in the marine environment, and their effects on the food-fish. Meeting the future human food security and safety through marine fish and fish products may need marine cage farming, introduction of genetically modified high yielding food-fish, and cultured contaminant free finless fish muscles as options.

Prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates in frozen flour and rice products in Shanghai, China

Staphylococcus aureus is widely recognized as a highly hazardous pathogen that poses significant threats to food safety and public health. This study aimed to assess the prevalence, antimicrobial resistance, and genetic characteristics of S. aureus isolates recovered from 288 frozen flour and rice product samples in Shanghai, China, between September 2019 and May 2020. A total of 81 S. aureus isolates were obtained, representing 25 sequence types (STs), with ST7 being the most prevalent (17.28%, n = 14). The majority of S. aureus isolates (85.19%, n = 69) carried at least one enterotoxin gene, with the seg gene being the most frequently detected (51.85%, n = 42). Additionally, 12 isolates (14.81%) were identified as methicillin-resistant S. aureus (MRSA) through mecA gene detection. Notably, this study reported the presence of an ST398 MRSA isolate in frozen flour and rice products for the first time. All MRSA isolates displayed multidrug resistance, with the highest resistance observed against cefoxitin (100.00%), followed by penicillin (91.67%) and erythromycin (66.67%). Genomic analysis of the 12 MRSA isolates revealed the presence of twenty distinct acquired antimicrobial resistance genes (ARGs), eight chromosomal point mutations, and twenty-four unique virulence genes. Comparative genome analysis indicated close genetic relationships between these MRSA isolates and previously reported MRSA isolates from clinical infections, highlighting the potential transmission of MRSA through the food chain and its implications for public health. Significantly, the identification of three plasmids harboring ARGs, insertion sequences (ISs), the origin of transfer site (oriT), and the relaxase gene suggested the potential for horizontal transfer of ARGs via conjugative plasmids in S. aureus. In conclusion, this study revealed significant contamination of retail frozen flour and rice products with S. aureus, and provided essential data for ensuring food safety and protecting public health.

Silver Bionanocomposites as Active Food Packaging: Recent Advances & Future Trends Tackling the Food Waste Crisis

Food waste is a pressing global challenge leading to over $1 trillion lost annually and contributing up to 10% of global greenhouse gas emissions. Extensive study has been directed toward the use of active biodegradable packaging materials to improve food quality, minimize plastic use, and encourage sustainable packaging technology development. However, this has been achieved with limited success, which can mainly be attributed to poor material properties and high production costs. In the recent literature, the integration of silver nanoparticles (AgNPs) has shown to improve the properties of biopolymer, prompting the development of bionanocomposites. Furthermore, the antibacterial properties of AgNPs against foodborne pathogens leads towards food shelf-life improvement and provides a route towards reducing food waste. However, few reviews have analyzed AgNPs holistically throughout a portfolio of biopolymers from an industrial perspective. Hence, this review critically analyses the antibacterial, barrier, mechanical, thermal, and water resistance properties of AgNP-based bionanocomposites. These advanced materials are also discussed in terms of food packaging applications and assessed in terms of their performance in enhancing food shelf-life. Finally, the current barriers towards the commercialization of AgNP bionanocomposites are critically discussed to provide an industrial action plan towards the development of sustainable packaging materials to reduce food waste.

Investigation into the prevalence of enterotoxin genes and genetic background of Staphylococcus aureus isolates from retain foods in Hangzhou, China

BACKGROUND

Staphylococcus aureus expresses numerous toxins, many of which are strongly believed to be responsible for specific symptoms and even diseases, making it significant in the pathogenesis of human health. Enterotoxins, which are vital toxins, are associated with foodborne illnesses that manifest through symptoms like vomiting and diarrhea. In the present study, 264 S. aureus isolates obtained from various retail foods in Hangzhou, China were further investigated the profiles of enterotoxin genes and genetic backgrounds.

RESULTS

Approximately, 64.02% of the isolates from diverse sources contained at least one Staphylococcal Enterotoxin (SE) genes, displaying a total of 36 distinct combinations. Enterotoxin gene cluster (egc) encoded enterotoxin genes, normally designated by seg, sei, sem, sen, seo and selu, plus with sep were more frequently detected (33.73%, each). In contrast, see, ses and set were absent in any of the isolates tested. A total of 44 sequence types (STs), 20 clonal complexes (CCs) and 66 different staphylococcal protein A (spa) types (including six novel types) were identified among those 169 SE-positive isolates. Moreover, nineteen methicillin-resistant Staphylococcus aureus (MRSA) isolates were identified. The majority of those isolates belonged to the CC59-Sccmec IVa cluster and carried the seb-sek-seq gene cluster. The egc cluster, either coexisting with or without other enterotoxin genes, was observed in all isolates allocated into CC5, CC9, CC20, CC25, CC72 and ST672. Irrespective of the spa types and origins of the food, it appeared that seh was a distinct genetic element present in isolates belonging to the CC1 clonal lineage.

CONCLUSIONS

The results not only proposed a suspected relationship between distribution of enterotoxigenic strains and genetic backgrounds, but also attributed the presence of novel enterotoxins to potential hazards in food safety.

Prevalence of Foodborne Bacterial Pathogens and Antibiotic Resistance Genes in Sweets from Local Markets in Iran

BACKGROUND

This study aimed to investigate the prevalences of some important antibiotic-resistance genes (ARGs) and foodborne bacterial pathogens in sweet samples collected from local markets in Iran.

METHODS

Forty sweet samples were collected. Foodborne pathogens and ARGs were detected in the sweet samples by conventional and multiplex PCR assays using species-specific primers.

RESULTS

Staphylococcus aureus, Cronobacter sakazakii, Shigella spp., Campylobacter jejuni, and Campylobacter coli were detected and identified in 47.5%, 20%, 45%, 5%, and 30% of the sweet samples, respectively. We found S. aureus and Shigella spp. were the most prevalent bacterial pathogens. S. aureus was found to be the most frequent pathogenic bacteria profiled in these samples. We also found a significant correlation between the presence of C. coli and Cr. sakazakii. We detected the blaSHV resistance gene in 97.5% of the sweet samples; however, blaTEM was detected in only one sample (2.5%).

CONCLUSIONS

Regarding these results, we suggest preventive strategies such as implementing automation of food processing; monitoring the personal hygiene and health of food handlers, and testing regularly for antibiotic resistance in raw materials and products.

spa Types and Staphylococcal Enterotoxin Production of Staphylococcus aureus Isolated from Wild Boar

Little is known about the structure of S. aureus population and the enterotoxin gene content in wild boar. In 1025 nasal swabs from wild boars, 121 S. aureus isolates were identified. Staphylococcal enterotoxin (SE) genes were identified in 18 isolates (14.9%). The seb gene was found in 2 S. aureus isolates, sec in 2 isolates, the see and seh genes were found in 4 and 11 isolates, respectively. The production of SEs was evaluated in bacteria grown in microbial broth. Concentration of SEB reached 2.70 µg/ml after 24 h and 4.46 µg/ml at 48 h. SEC was produced at 952.6 ng/ml after 24 h and 7.2 µg/ml at 48 h. SEE reached 124.1 ng/ml after 24 h and 191.6 ng/ml at 48 h of culture. SEH production reached 4.36 µg/ml at 24 h and 5.42 µg/ml at 48 h of culture. Thirty-nine spa types were identified among S. aureus isolates. The most prevalent spa types were t091 and t1181, followed by t4735 and t742, t3380 and t127. Twelve new spa types, i.e., t20572‒t20583 were identified. The wild boar S. aureus population was shown to contain previously identified animal/human-associated spa types and spa types not identified in humans or animals. We also indicate that wildlife animals can be a significant reservoir of see-positive S. aureus.

Genotypes and virulence factors in Staphylococcus aureus isolated from dairy cows with subclinical mastitis in Serbia

This study aimed to determine the prevalence of Staphylococcus aureus subclinical mastitis and to genotype the S. aureus isolates using the 16S-23S rRNA intergenic spacer (RS-PCR) method. In addition, the genes responsible for adherence, biofilm formation, host evasion, tissue necrosis, methicillin resistance, and enterotoxin production of S. aureus were investigated. The overall prevalence of S. aureus subclinical mastitis in lactating cows was 5.4% (95% confidence interval, CI=4.7-6.1%). An increased risk of S. aureus intramammary infection was observed on small family farms (odds ratio, OR=4.2, 95% CI=2.6-6.6, P < 0.001) and medium-sized farms (OR=3.5, 95% CI=2.2-5.7, P < 0.001). The RS-PCR analysis revealed 44 genotypes and genotype variants, of which 15 new genotypes and five new variants were detected within small and medium-sized farms. S. aureus isolates of new genotypes and genotype variants carried the clfA gene responsible for adherence at a lower frequency (64.8%) and enterotoxin-producing genes sea (20.4%), seb (14.8%) and sec (14.8%) at a higher frequency than the other known genotypes (P < 0.001), and were confirmed to carry the sej and sep genes. The spa gene was detected in all S. aureus isolates, whereas none harbored bap, ser, or tsst-1 genes. Methicillin-resistant strains of S. aureus (MRSA) were also detected, with a higher prevalence (19.2%) on large farms with more than 50 cows (P < 0.001). Using molecular techniques as diagnostic tools provides a better understanding of intramammary staphylococcal infections' occurrence, spread, and eradication.

Whole genome sequence-based characterization of virulence and antimicrobial resistance gene profiles of Staphylococcus aureus isolated from food poisoning incidents in eastern China

Staphylococcus aureus is an opportunistic foodborne pathogen occasionally isolated from diarrhea patients. In recent years, increasing studies have reported the detection of S. aureus in food poisoning incidents due to food contamination in the North and South of China. However, the epidemiology and genetic characteristics of S. aureus from food poisoning incidents in Eastern China remain unknown. The present study examined the genetic characteristics, antimicrobial resistance, and virulent factors of multidrug-resistant S. aureus isolated from 22 food poisoning incidents reported by the hospitals and health centers in Eastern China from 2011 to 2021. A total of 117 resistant and enterotoxigenic S. aureus isolates were collected and sequenced, among which 20 isolates were identified as methicillin resistant. Genetic analysis revealed 19 distinct CC/ST types, with CC6, CC22, CC59, CC88, and CC398 being the most frequent variants in methicillin-resistant S. aureus (MRSA). A considerable shift in CC types from CC1 to CC398 between 2011 and 2021 was observed in this study, indicating that CC398 may be the main epidemic strain circulating in the current food poisoning incidents. Additionally, genes for enterotoxins were detected in 55 isolates, with a prevalence of 27.8% (27/97) for methicillin-sensitive variants and 35.0% (7/20) for MRSA. The scn gene was detected in 59.0% of the isolates, demonstrating diverse contaminations of S. aureus among livestock-to-human transmission. Of the 117 isolates, only ten isolates displayed multi-drug resistance (MDR) to penicillin, tetracycline, and macrolides. None of the 117 foodborne S. aureus isolates tested positive for vanA in this study. Together, the present study provided phylogenetic characteristics of S. aureus from food poisoning incidents that emerged in Eastern China from 2011 to 2021. Our results suggested that these diarrhea episodes were hypotonic and merely transient low-MDR infections, however, further research for continued surveillance given the detection of virulence and antimicrobial resistance determinants is required to elucidate the genomic characteristics of pathogenic S. aureus in food poisoning incidents in the context of public health.

An approach to zwitterionic peptide design for colorimetric detection of the Southampton norovirus SV3CP protease

Noroviruses are highly contagious and are one of the leading causes of acute gastroenteritis worldwide. Due to a lack of effective antiviral therapies, there is a need to diagnose and surveil norovirus infections to implement quarantine protocols and prevent large outbreaks. Currently, the gold standard of diagnosis uses reverse transcription polymerase chain reaction (RT-PCR), but PCR can have limited availability. Here, we propose a combination of a tunable peptide substrate and gold nanoparticles (AuNPs) to colorimetrically detect the Southampton norovirus 3C-like protease (SV3CP), a key protease in viral replication. Careful design of the substrate employs a zwitterionic peptide with opposite charged moieties on the C- and N- termini to induce a rapid color change visible to the naked eye; thus, this color change is indicative of SV3CP activity. This work expands on existing zwitterionic peptide strategies for protease detection by systematically evaluating the effects of lysine and arginine on nanoparticle charge screening. We also determine a limit of detection for SV3CP of 28.0 nM with comparable results in external breath condensate, urine, and fecal matter for 100 nM of SV3CP. The key advantage of this system is its simplicity and accessibility, thus making it an attractive tool for qualitative point-of-care diagnostics.

First Report of Food Poisoning Due to Staphylococcal Enterotoxin Type B in Döner Kebab (Italy)

Staphylococcal food poisoning results from the consumption of food contaminated by staphylococcal enterotoxins. In July 2022, the Turin local health board was notified of a suspected foodborne outbreak involving six children who had consumed döner kebab purchased from a takeaway restaurant. The symptoms (vomiting and nausea) were observed 2-3 h later. A microbiological analysis of the food samples revealed high levels (1.5 × 107 CFU/g) of coagulase-positive staphylococci (CPS). The immunoassay detected a contamination with staphylococcal enterotoxins type B (SEB). The whole genome sequencing of isolates from the food matrix confirmed the staphylococcal enterotoxin genes encoding for type B, which was in line with the SEB detected in the food. This toxin is rarely reported in staphylococcal food poisoning, however, because there is no specific commercial method of detection. The involvement of enterotoxin type P (SEP) was not confirmed, though the corresponding gene (sep) was detected in the isolates. Nasal swabs from the restaurant food handlers tested positive for CPS, linking them to the likely source of the food contamination.

Contamination of herbal medicinal products in low-and-middle-income countries: A systematic review

The use of herbal medicinal products (HMPs) has grown significantly across low-and-middle-income countries (LMICs). Consequently, the safety of these products due to contamination is a significant public health concern. This systematic review aimed to determine the prevalence, types, and levels of contaminants in HMPs from LMICs. A search was performed in seven online databases, i.e., Africa journal online (AJOL), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Directory of Open Access Journals (DOAJ), Health Inter-Network Access to Research Initiative (HINARI), World Health Organization Global Index Medicus (WHO GIM), Scopus, and PubMed using appropriate search queries and reported as per the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) guidelines. Ninety-one peer-reviewed articles published from 1982 to 2021 from 28 different countries across four continents were included in the study. Although metals, microbial, mycotoxins, pesticides, and residual solvents were the reported contaminants in the 91 articles, metals (56.0%, 51/91), microbial (27.5%, 25/91), and mycotoxins (18.7%, 17/91) were the most predominant. About 16.4% (1236/7518) of the samples had their contaminant levels above the regulatory limits. Samples tested for microbial contaminants had the highest proportion (46.4%, 482/1039) of contaminants exceeding the regulatory limit, followed by mycotoxins (25.8%, 109/423) and metals (14.3%, 591/4128). The proportion of samples that had their average non-essential metal contaminant levels above the regulatory limit was (57.6%, 377/655), 18.3% (88/480), 10.7% (24/225), and 11.3% (29/257) for Pb, Cd, Hg, and As, respectively. The commonest bacteria species found were Escherichia coli (52.3%, 10/19) and Salmonella species (42.1%, 8/19). This review reported that almost 90% of Candida albicans and more than 80% of moulds exceeded the required regulatory limits. HMP consumption poses profound health implications to consumers and patients. Therefore, designing and/or implementing policies that effectively regulate HMPs to minimize the health hazards related to their consumption while improving the quality of life of persons living in LMICs are urgently needed.