Staphylococcal enterotoxins

Gold nanocubes etching enhanced light scattering immunoassay for highly sensitive detection of Staphylococcus aureus enterotoxin A

An innovative light scattering immunoassay was developed using an AuNPs etching strategy. Three types of anisotropic gold nanoparticles, including gold nanocubes, nanorods, and nanoflowers with distinct morphologies, were utilized to investigate how these morphological differences affect the sensitivity of light scattering signal transduction. Based on theoretical insights into light scattering and electromagnetic fields, gold nanocubes were identified as the optimal probes for enhancing light scattering signal transduction and were employed to construct an immunoassay for detecting staphylococcal enterotoxin A (SEA). The developed immunoassay achieved ultrahigh sensitivity for SEA detection in milk samples, with a detection limit of 10.39 pg mL-1, which is 190 times lower than that of conventional ELISA. The proposed immunoassay was validated across ten food samples, demonstrating high accuracy and robustness. Given these promising results, we believe this method has significant potential for screening trace levels of SEA in food products.

Prevalence, antibiotic resistance patterns, and virulence factors of Staphylococcus aureus isolates associated with bovine mastitis in northern Bangladesh

Staphylococcus (S.) aureus is a major cause of bovine mastitis and is notorious for its capacity to resist antibiotics, presenting substantial risks to both livestock and human health. The aim of this research was to assess the prevalence of S. aureus in bovine mastitis cases, as well as to examine their patterns of antimicrobial resistance and virulence genes contributing to mastitis in cattle. For this study, 120 milk samples were gathered from clinically mastitis affected cows across three districts in the northern part of Bangladesh. The detection and confirmation of S. aureus involved standard microbiological and biochemical techniques. The antibiotic sensitivity of the strains was evaluated using the disk diffusion method with a variety of antibiotics frequently used in veterinary settings. Furthermore, PCR was utilized to explore the presence of virulence genes linked to the pathogenicity of S. aureus. Findings revealed that out of the sampled cases, 56 strains of S. aureus were isolated, indicating a prevalence rate of 46.66 % in cases of clinical mastitis. The results revealed a diverse range of antibiotic resistance patterns among the isolates, with a notable prevalence of resistance to penicillin (100 %), ampicillin (85 %), amoxicillin (75 %), tetracycline (66 %), chlortetracycline (64 %), azithromycin (57 %), kanamycin (54 %), and gentamicin (50 %). 36 isolates out of 56 (64 %) were multidrug resistant in nature. Furthermore, virulence gene profiling identified the genes responsible for biofilm formation (bap), adhesion, inflammation and tissue damage (seb, pvl), and toxin production (hla and hlb), indicating the potential pathogenicity of the isolates. Notably, 12 isolates (21.42 %) harbored gene linked to methicillin resistance (mecA), raising concerns about the potential transmission of antimicrobial-resistant S. aureus strains from dairy cows to humans through the food chain. These findings underscore the critical importance of implementing stringent antimicrobial stewardship practices and surveillance measures in dairy farming to mitigate the dissemination of antibiotic resistance.

Genomic characterization of healthcare-associated ST5 MRSA causing severe pseudomembranous enteritis in intensive care unit

BACKGROUND

Methicillin resistant Staphylococcus aureus (MRSA) is one of the main causes of hospital-acquired infections, but the diagnosis of MRSA pseudomembranous enteritis has faded in recent years. Here, we reported a pseudomembranous enteritis case in a young male patient caused by ST5 MRSA.

METHODS

Clinical data of the patient were collected from medical records. Mass spectrometry identification, antimicrobial susceptibility testing, whole genome sequencing, as well as resistance and virulence genes detection of MRSA strain were performed.

RESULTS

A 27-year-old young man with acute pancreatitis and septic shock in the intensive care unit passed large volume of intestine-like "stool" with more than 200 centimetres in length. A large number of Gram-positive cocci was persistently found in the stool samples. Histopathological examination of the intestine-like stool revealed that this stool was actually pseudomembrane, consisting of fibrinous exudate, inflammatory cells and clusters of gram-positive cocci adjacent to the luminal border. The patient was suspected for diagnosis of pseudomembranous enteritis. Stool and gastric juice cultures were positive for MRSA. These strains belonged to ST5-SCCmec II-t311, and harbored abundant virulence genes, especially enterotoxin genes. They contained not only sea, sec3, sel, but an enterotoxin gene cluster (egc, seg, sei, sem, sen, seo, yent1 and yent2), which may serve as an enterotoxin gene nursery. Besides, the strains were related to the isolates of the same hospital between 2013 and 2015, and there may be nosocomial transmission.

CONCLUSIONS

The severe clinical symptoms in this patient and the described virulence genes all suggested that these ST5 strains belonged to a kind of hypervirulent MRSA lineage. At the same time, the analysis of cgMLST indicated that there might be nosocomial transmission, which required the society to pay more attention to this highly virulent nosocomial clone.

Sample-to-answer microfluidic device towards the point-of-need detection of Staphylococcus aureus enterotoxin genes in ruminant milk

Milk is commonly screened both for indicators of animal disease and health, but also for foodborne hazards. Included in these analyses is the detection of Staphylococcus aureus, that can produce an enterotoxin, causing staphylococcal food poisoning (SFP), which often leads to sudden onset of significant gastrointestinal symptoms in humans. Epidemiological data on SFP are limited, particularly in low- and middle-income countries. Many conventional assays for the detection of staphylococcal enterotoxins rely on the detection of the genes coding for them, either directly in food samples or after bacterial culture. Currently, many of the nucleic acid-based methods used require specific expertise and equipment, whilst bacterial culture takes 24-48 hours; both are contributory factors that limit efforts either during food safety emergencies or routine screening. Here we present the development of a "sample-to-answer" isothermal nucleic acid loop-mediated amplification (LAMP) assay in a microfluidic device for the detection of Staphylococcus aureus enterotoxin genes in ruminant milk. A multiplex LAMP assay targeting two of the most prevalent S. aureus enterotoxin-encoding genes (A and B) was integrated into a microfluidic device combining simple 1 : 10 dilution for sample preparation and a lateral flow assay for easy readout. We achieved a limit of detection of 104 colony forming units per ml in spiked cow and goat milk samples, an order of magnitude more sensitive than the European recommendation for the maximum allowable presence of coagulase-positive staphylococci in raw milk. The assay showed no cross-reactivity in detecting other tested non-enterotoxigenic S. aureus strains or associated foodborne pathogens. The test integrated the simplicity of use of microfluidic devices with the sensitivity, specificity and rapidity of a nucleic acid-based assay, and a simple lateral flow readout to provide an appropriate device to ensure the safety of milk for human consumption. To illustrate its potential for point-of-need practical applications, the test was performed in agricultural settings in rural Turkey in a limited feasibility exercise.

The quality and technological parameters of milk obtained from dairy cows with subclinical mastitis

Mastitis is one of the most common diseases in dairy cattle. It significantly reduces milk quality and yield, thus incurring economic losses for farmers. This study investigates the impact of various bacterial pathogens on the SCC, milk composition, and technological properties of milk samples from 302 clinically healthy Polish Holstein-Friesian cows kept under intensive rearing conditions. Of the 462 milk samples analyzed, 85.06% were contaminated with bacteria. The majority were coagulase-negative staphylococci (52.60%). Escherichia coli, Streptococcus dysgalactiae, and Streptococcus uberis, (Group 4) and Staphylococcus aureus and Streptococcus agalactiae (Group 5), collectively considered major pathogens, were identified in 16.66% of samples; their presence was associated with higher SCC levels. Additionally, contamination with Staph. aureus or Strep. agalactiae had prolonged clotting time, adversely affected curd and whey quality, with curd yield remaining unaltered. Bacterial contamination did not appear to significantly affect the yield of milk or its main components, namely protein, casein, lactose, fat, TS, solid nonfat, free fatty acid, or citric acid. Although pH, freezing point depression (FPD), and acidity also remained unaffected by bacterial contamination, they were significantly influenced by herd-year-season of calving and herd-year-time of sampling interaction effects. The results indicate that the presence of bacteria causing subclinical mastitis negatively influences milk processing potential. However, fixed linear regression indicated that the number of colony-forming units (cfu/mL) only had a significant influence on FPD and clotting time, and as such, the number of bacteria in a sample did not influence milk yield or quality during subclinical chronic mastitis.

Antimicrobial Resistance, Virulence Gene Profiling, and Spa Typing of Staphylococcus aureus Isolated from Retail Chicken Meat in Alabama, USA

Antibiotic-resistant Staphylococcus aureus (S. aureus) in retail meat poses a public health threat requiring continuous surveillance. This study investigated the frequency of isolation, toxin genes, and antibiotic resistance profile of S. aureus recovered from retail poultry meat samples and presented results beneficial to public health interventions. Of 200 samples collected, 16% (32/200) tested positive for S. aureus, and these were recovered from thigh 37.5% (12/32), wing 34.4% (11/32), gizzard (15.6% (5/32), and liver 12.5% (4/32) samples. Findings of spa typing analysis revealed that 68.8% (22/32), 18.8% (6/32), 9.4% (3/32), and 3.0% (1/32) of the isolates belonged to the spa types t267, t160, t548, and t008, respectively. For antibiotic susceptibility testing, 12.5% (4/32) of the isolates were resistant to only penicillin, but one isolate (1/32; 3%) showed resistance to the antibiotics penicillin, erythromycin, ampicillin, and oxacillin. PCR analysis revealed that 9.4% (3/32) of the isolates carried the mecA gene associated with methicillin-resistant Staphylococcus aureus (MRSA) isolates. One MRSA isolate was identified as a t008 spa type, and harbored a 26,974 bp-sized plasmid, which was the source of its resistance to penicillin, ampicillin, erythromycin, and oxacillin. The staphylococcal enterotoxin (SE) genes seg, sei, sek, seb, selm, and seln were also identified among the isolates, and mostly the antimicrobial and enterotoxin genes were carried on plasmids of the isolates. This study raises awareness on the continuous circulation of pathogenic microbes like S. aureus in retail poultry meat.

Methicillin- and vancomycin-resistant Staphylococcus aureus in chicken carcasses, ready-to-eat chicken meat sandwiches, and buffalo milk

Methicillin-resistant Staphylococcus aureus (MRSA) is a growing public health concern; however, there is limited information about MRSA and VRSA (Vancomycin-resistant S. aureus) among animal-origin food. Therefore, this study intended to elucidate the prevalence, enterotoxin existence, antimicrobial resistance profiles, and antimicrobial resistance genes of S. aureus strains isolated from chicken carcasses, ready-to-eat (RTE) chicken meat sandwiches, and buffalo milk samples marketed in Mansoura City, Egypt. Of the 240 samples examined, 52.1 % were contaminated with S. aureus, with a mean count of 4.11 log10 CFU/g. A total of 250 isolates were verified as S. aureus by PCR targeting nuc gene, of which 39.2 % (98/250) harbored at least one S. aureus enterotoxin (SE) gene. The predominant SE genes were sea (61.2 %, 60/98), followed by sed (58.2 %, 57/98), sec (38.8 %, 38/98), and seb (27.6 %, 27/98). All isolates were resistant to at least one antimicrobial, with an average MAR (multiple antibiotic resistance) index of 0.530. Four isolates exhibited resistance to all antimicrobial agents tested. Interestingly, 100 %, 76.4 %, 35.6 %, 30.8, 10.4 %, 6 %, and 1.6 % of isolates were resistant to penicillin, azithromycin, oxacillin, ceftaroline, vancomycin, linezolid, and daptomycin, respectively. Of the 250 S. aureus strains tested, 38 % were confirmed as MRSA by mecA gene, while 10.4 % were identified as VRSA by vanA gene. The high prevalence of MRSA and VRSA isolates among samples tested is worrisome. Hence, monitoring antimicrobial usage in veterinary medicine and applying strict hygienic measures during food handling and processing is imperative to prevent the spread of such resistant bacteria and protect public health.

Exploring the regulatory role of small RNAs in modulating host-pathogen interactions: implications for bacterial and viral infections

MicroRNAs (miRNAs) and transfer RNA-derived stress-induced RNAs (tiRNAs) have emerged as crucial players in the post-transcriptional regulation of gene expression in various cellular processes, including immunity and host defense against infections. In recent years, increasing evidence has highlighted their complex role in influencing the host response during viral and bacterial infections. miRNAs have been shown to play multiple roles in host-pathogen interaction like TLR activation and altered disease virulence during bacterial infections. In the context of viral infections, miRNAs are involved in regulating viral replication, pathogenesis, and immune evasion. Similarly, tiRNAs have recently emerged as novel players in bacterial and viral infections such as modulating bacterial growth, adaptation to stress conditions, host antiviral responses, and impacting viral replication and pathogenesis. This review provides a comprehensive analysis of the potential of miRNA expression profiles as diagnostic biomarkers to differentiate between bacterial and viral infections. Further discusses the key pathways through which small RNAs regulate bacterial and viral infection-related diseases.

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

Pathogenic potential of meat-borne coagulase negative staphylococci strains from slaughterhouse to fork

This study aimed to determine the prevalence of coagulase-negative staphylococci (CoNS) in meat processing lines for their pathogenic potential associated with biofilm formation, staphylococcal toxin genes, and antibiotic resistance in obtained isolates. Out of 270 samples, 56 isolates were identified as staphylococcal with their species level, and their antimicrobial resistance profiles were also determined with the BD Phoenix™ system. Among these, CoNS were found in 32 isolates, including S. epidermidis (22%), S. warneri (22%), S. cohnii (9%), S. schleiferi (9%), S. capitis (6%), S. haemolyticus (6%), S. lugdunensis (6%), S. chromogenes (6%), S. kloosii (3%), S. sciuri (3%), S. lentus (3%), and S. caprae (3%). Biofilm formation was observed in 78.1% of CoNS isolates, with 56% being strong biofilm producers; and the frequency of the icaA, fnbA, and fnbB genes were 43.7% and 34.3%, and 9.3% in isolates, respectively. Twenty-five (78.1%) of these strains were resistant to at least one antimicrobial agent, 20 (80%) of which exhibited multidrug resistance (MDR). Regarding genotypic analyses, 15.6%, 22.2%, 87.5%, and 9% of isolates, were positive for blaZ, ermC, tetK, and aacA-aphD, respectively. In 8 (25%) of all isolates had one or more staphylococcal toxin genes: the sed gene was the most frequent (12.5%), followed by eta (9.3%), tst-1 (6.25%), and sea (3.1%). In conclusion, this study highlights meat; and meat products might be reservoirs for the biofilm-producing MDR-CoNS, which harbored several toxin genes. Hence, it should not be ignored that CoNS may be related to foodborne outbreaks.

Continuous Oral Administration of the Superantigen Staphylococcal Enterotoxin C2 Activates Intestinal Immunity and Modulates the Gut Microbiota in Mice

Staphylococcal Enterotoxin C2 (SEC2), a classical superantigen, is an antitumor immunotherapy agent. However, the injectable formulation of SEC2 limits its clinical application. Here, it is reported that oral administration of SEC2 activates the intestinal immune system and benefits intestinal health in a mouse model. These results indicate that intact SEC2 is detected in the stomach, intestine, and serum after oral administration. Continuous oral administration of SEC2 activates immune cells in gut-associated lymphoid tissues, promoting extensive differentiation and proliferation of CD4+ and CD8+ T cells and CD19+ B cells, leading to increased production of cytokines and secretory immunoglobulin A. SEC2 also enhances intestinal barrier function, as demonstrated by an increased villus length/crypt depth ratio and elevated expression of mucins and tight junction proteins. Additionally, SEC2 indirectly influenced gut microbiota, reinforcing potential probiotics and short-chain fatty acid synthesis. Enhanced differentiation of T and B cells in the spleen, coupled with elevated serum interleukin-2 levels, suggests systemic immune enhancement following oral administration of SEC2. These findings provide a scientific basis for the development of SEC2 as an oral immunostimulant for immune enhancement and anti-tumor immunotherapy.

Structural insights into the binding of nanobodies to the Staphylococcal enterotoxin B

Staphylococcal Enterotoxin Type B (SEB), produced by Staphylococcus aureus bacteria, is notorious for inducing severe food poisoning and toxic shock syndrome. While nanobody-based treatments hold promises for combating SEB-induced diseases, the lack of structural information between SEB and nanobodies has hindered the development of nanobody-based therapeutics. Here, we present crystal structures of SEB-Nb3, SEB-Nb6, SEB-Nb8, SEB-Nb11, and SEB-Nb20 at resolutions ranging from 1.59 Å to 2.33 Å. Crystallographic analysis revealed that Nb3, Nb8, Nb11, and Nb20 bind to SEB at the T-cell receptor (TCR) interface, while Nb6 binds at the major histocompatibility complex (MHC) interface, suggesting their potential to inhibit SEB function by disrupting interactions with TCR or MHC molecules. Molecular biological analyses confirmed the thermodynamic and kinetic parameters of Nb3, Nb5, Nb6, Nb8, Nb11, Nb15, Nb18, and Nb20 to SEB. The competitive inhibition was further confirmed by cell-based experiments demonstrating nanobody neutralization. These findings elucidate the structural basis for developing specific nanobodies to neutralize SEB threats, providing crucial insights into the underlying mechanisms and offering significant assistance for further optimization towards future therapeutic strategies.

Antimicrobial resistance, enterotoxin and biofilm production genes in Staphylococcus spp. isolated from facilities and fomites in veterinary hospital in the Caatinga biome

The Caatinga biome occurs only in Brazil and offers epidemiological conditions that should be assessed differently from other regions of Brazil and the world. Thus, the aim of this survey was to identify antimicrobial resistance, enterotoxin and biofilm production genes in Staphylococcus spp. isolated from facilities and fomites in a veterinary hospital in Caatinga biome. Samples were collected from surfaces of small animal clinical care tables (n =8), cages in the dog and cat hospitalisation sector and animals with infectious diseases (n = 21), small animal surgical centre (n =8), sterilisation sector (n =7) and stethoscopes (n = 32) by using sterile swabs. Bacterial isolation and identification, antimicrobial resistance phenotypic test and molecular detection of antimicrobial resistance, biofilm formation and enterotoxin genes were carried out. Ninety-five bacterial isolates were obtained, and 29 (30.5%) were identified as Staphylococcus spp. Overall, 13 isolates (44.8%) of six species of Staphylococcus spp. showed antimicrobial resistance profile, as well as S. haemolyticus expressed phenotypic profile of multidrug resistance. The antimicrobials with the highest resistance rates were penicillin and tetracycline. The most frequent resistance genes were blaZ and tetM, both detected in 10 (76.9%) isolates. The mecA, tetL and tetK genes had frequencies of 38.5% (5/13), 23.1% (3/13) and 15.4% (2/13), respectively. The biofilm production marker, icaD gene, was detected in one S. sciuri strain. SEE gene, which encodes enterotoxins, was detected in 15.4% (2/13) of the strains (S. pseudintermedius and S. intermedius). The occurrence of Staphylococcus spp. carrying resistance genes to diferent classes of antimicrobials, presenting MDR phenotypic pattern and carrying enterotoxins and biofim encoding genes recovered from veterinary hospital facilities and fomites in the Caatinga biome reinforce the need to implement prevention cares in veterinary practices to avoid One Health-concerning conditions.

Detection of Staphylococcal Enterotoxins A and E and Methicillin Resistance in Staphylococcus aureus Strains From Moroccan Broiler Chicken Meat

Foodborne epidemics have become a serious public health emergency worldwide. Foods of animal origin, in particular chicken meat, are considered to be potential vectors of pathogenic bacteria, particularly Staphylococcus aureus. This bacterium can be resistant in the form of methicillin-resistant S. aureus (MRSA) or produce enterotoxins leading to food poisoning when ingested. This study is aimed at exploring the virulence genes in S. aureus responsible for producing enterotoxins (staphylococcal enterotoxin [SE] A [sea] and SE E [see]) and determining the prevalence of MRSA in raw broiler meat in the Casa-Rabat region in Morocco. A quantitative (q) PCR (qPCR) assay, using specific primers for S. aureus (nuc) confirmation and detection of enterotoxin genes (sea and see), as well as the methicillin-resistant gene (mecA), was employed. Our findings indicated that all tested strains were positively identified as S. aureus. Among them, one isolate (1/54) tested positive for the see gene (1.85%), while none carried the sea gene. Furthermore, the mecA gene, indicative of MRSA, was present in 12/54 of the isolates (22.22%). The potential presence of MRSA in Moroccan poultry meat underscores a public health risk. Thus, stringent measures are imperative to curtail the contamination and proliferation of this bacterium during the slaughtering process, underscoring the importance of continuing research into the prevalence of MRSA colonization among poultry slaughterhouse personnel.

Staphylococcal Enterotoxins: Description and Importance in Food

Staphylococcus aureus stands out as one of the most virulent pathogens in the genus Staphylococcus. This characteristic is due to its ability to produce a wide variety of staphylococcal enterotoxins (SEs) and exotoxins, which in turn can cause staphylococcal food poisoning (SFP), clinical syndromes such as skin infections, inflammation, pneumonia, and sepsis, in addition to being associated with the development of inflammation in the mammary glands of dairy cattle, which results in chronic mastitis and cell necrosis. SEs are small globular proteins that combine superantigenic and emetic activities; they are resistant to heat, low temperatures, and proteolytic enzymes and are tolerant to a wide pH range. More than 24 SE genes have been well described (SEA-SEE, SEG, SEH, SEI, SEJ, SElK, SElL, SElM, SElN, SElO, SElP, SElQ, SElR, SElS, SElT, SElU, SElV, SElW, SElX, SElY, and SElZ), being a part of different SFP outbreaks, clinical cases, and isolated animal strains. In recent years, new genes (sel26, sel27, sel28, sel31, sel32, and sel33) from SEs have been described, as well as two variants (seh-2p and ses-3p) resulting in a total of thirty-three genes from Ses, including the nine variants that are still in the process of genetic and molecular structure evaluation. SEs are encoded by genes that are located in mobile genetic elements, such as plasmids, prophages, pathogenicity islands, and the enterotoxin gene cluster (egc), and housed in the genomic island of S. aureus. Both classical SEs and SE-like toxins (SEls) share phylogenetic relationships, structure, function, and sequence homology, which are characteristics for the production of new SEs through recombination processes. Due to the epidemiological importance of SEs, their rapid assessment and detection have been crucial for food security and public health; for this reason, different methods of identification of SEs have been developed, such as liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS), molecular methods, and whole-genome sequencing; providing the diagnosis of SEs and a better understanding of the occurrence, spread, and eradication of SEs. This review provides scientific information on the enterotoxins produced by S. aureus, such as structural characteristics, genetic organization, regulatory mechanisms, superantigen activity, mechanisms of action used by SEs at the time of interaction with the immune system, methods of detection of SEs, and recent biocontrol techniques used in food.

High toxinogenic potential of Staphylococcus aureus from wild ungulates in Brandenburg, Germany with a low level of antibiotic resistance

INTRODUCTION

Data regarding the occurrence and virulence of Staphylococcus (S.) aureus in wild living animals is rare. However, S. aureus may carry a multitude of virulence factors and express resistance to several antimicrobial substances. Handling game meat may thus lead to serious infections or food poisoning. The aim of this study was to provide insights into the occurrence and characteristics of S. aureus in wild ungulates from Brandenburg, Germany.

METHODS

Nasal swabs of externally healthy-looking wild boars, roe, fallow and red deer were collected in hunts during season 2021/2022 and analyzed for S. aureus by selective enrichment. Species were determined using matrix assisted laser desorption ionization mass spectrometry and tested for phenotypic antimicrobial resistance. Whole-genome sequencing was conducted for genotyping, determination of virulence associated genes and analysis of phylogenetic relationships.

RESULTS

S. aureus were recovered from approximately 8% of nasal swabs. However, the strains were only obtained from the sampled wild ruminants. S. aureus isolates were associated with sequence types (ST) 1, ST30, ST133, ST425, ST582 and ST6238. Isolates of ST1 clustered closely together in the phylogenetic analysis. Genes encoding staphylococcal enterotoxin (SE) or SE-like (SEl) were found in 14/17 isolates. In particular, a seh gene was present in 12/17 isolates. Moreover, two isolates harbored a multiplicity of genes encoding SE or SEl. In addition, the toxic shock syndrome toxin encoding tst gene was detected in one isolate. This isolate was resistant to penicillin and cefoxitin and accordingly harbored the blaZ gene.

DISCUSSION

Wild ungulates intended for human consumption may carry potentially virulent S. aureus. In one case, the close phylogenetic relationship of S. aureus isolates indicates a possible intraspecific spread within a common territory. However, for others, the origin or the spread pattern can only be inferred. Handling of animals or their carcasses might contribute to staphylococcal infections in humans. Moreover, food poisoning due to SE producing strains may occur, if recommended hygiene practices are not applied during processing of game meat.

Effective degradation of various bacterial toxins using ozone ultrafine bubble water

Infectious and foodborne diseases pose significant global threats, with devastating consequences in low- and middle-income countries. Ozone, derived from atmospheric oxygen, exerts antimicrobial effects against various microorganisms, and degrades fungal toxins, which were initially recognized in the healthcare and food industries. However, highly concentrated ozone gas can be detrimental to human health. In addition, ozonated water is unstable and has a short half-life. Therefore, ultrafine-bubble technology is expected to overcome these issues. Ultrafine bubbles, which are nanoscale entitles that exist in water for considerable durations, have previously demonstrated bactericidal effects against various bacterial species, including antibiotic-resistant strains. This present study investigated the effects of ozone ultrafine bubble water (OUFBW) on various bacterial toxins. This study revealed that OUFBW treatment abolished the toxicity of pneumolysin, a pneumococcal pore-forming toxin, and leukotoxin, a toxin that causes leukocyte injury. Silver staining confirmed the degradation of pneumolysin, leukotoxin, and staphylococcal enterotoxin A, which are potent gastrointestinal toxins, following OUFB treatment. In addition, OUFBW treatment significantly inhibited NF-κB activation by Pam3CSK4, a synthetic triacylated lipopeptide that activates Toll-like receptor 2. Additionally, OUFBW exerted bactericidal activity against Staphylococcus aureus, including an antibiotic-resistant strain, without displaying significant toxicity toward human neutrophils or erythrocytes. These results suggest that OUFBW not only sterilizes bacteria but also degrades bacterial toxins.

Genetic Complexity of CC5 Staphylococcus aureus Isolates Associated with Sternal Bursitis in Chickens: Antimicrobial Resistance, Virulence, Plasmids, and Biofilm Formation

Sternal bursitis, a common inflammatory condition in poultry, poses significant challenges to both animal welfare and public health. This study aimed to investigate the prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates associated with sternal bursitis in chickens. Ninety-eight samples were collected from affected chickens, and 24 S. aureus isolates were identified. Antimicrobial susceptibility testing revealed resistance to multiple agents, with a notable prevalence of aminoglycoside resistance genes. Whole genome sequencing elucidated the genetic diversity and virulence profiles of the isolates, highlighting the predominance of clonal complex 5 (CC5) strains. Additionally, biofilm formation assays demonstrated moderate biofilm production capacity among the isolates. These findings underscore the importance of vigilant monitoring and targeted interventions to mitigate the impact of sternal bursitis in poultry production systems.

Mechanisms of host adaptation by bacterial pathogens

The emergence of new infectious diseases poses a major threat to humans, animals, and broader ecosystems. Defining factors that govern the ability of pathogens to adapt to new host species is therefore a crucial research imperative. Pathogenic bacteria are of particular concern, given dwindling treatment options amid the continued expansion of antimicrobial resistance. In this review, we summarize recent advancements in the understanding of bacterial host species adaptation, with an emphasis on pathogens of humans and related mammals. We focus particularly on molecular mechanisms underlying key steps of bacterial host adaptation including colonization, nutrient acquisition, and immune evasion, as well as suggest key areas for future investigation. By developing a greater understanding of the mechanisms of host adaptation in pathogenic bacteria, we may uncover new strategies to target these microbes for the treatment and prevention of infectious diseases in humans, animals, and the broader environment.

Molecular characterization of antimicrobial resistance genes of Staphylococcus aureus isolated from mastitic camel milk in Egypt

Staphylococcus aureus is one of the most common causes of mastitis worldwide. This study aimed to determine the prevalence and antimicrobial resistance (AMR) patterns of S. aureus in mastitic milk samples collected from camel farms in Matrouh Governorate, Egypt. A total of 200 mastitic camel milk samples were evaluated for S. aureus using both conventional culture-based and molecular-based methods. Antibiotic susceptibility testing of S. aureus isolates was conducted using disc diffusion and agar dilution methods, with antibiotic resistance genes identified through polymerase chain reaction with specific primers. Out of samples tested, 60 (30.00%) were positive for S. aureus. The isolates displayed the highest of resistance against piperacillin-tazobactam (55.00%) followed by trimethoprim- sulfamethoxazole (45.00%) and amoxicillin (40.00%). Half of the isolates were multidrug-resistant (MDR). The AMR genes included methicillin-resistant gene (mecA), β-lactamase gene (blaZ), tetracycline resistance gene (tetK), erythromycin resistance gene (ermB) and vancomycin resistant gene (vanA) were detected in 100%, 100%, 95.00%, 90.00% and 20.00% of the isolates, respectively. In conclusion, the presence of MDRS aureus as a cause of clinical camel mastitis is a significant veterinary and public health concern. These findings highlight the importance of proper antibiotic use in Egyptian camel farms and the need for molecular techniques to fully understand the genetic profile of antimicrobial-resistant S. aureus isolates.

Contribution of staphylococcal virulence factors in the pathogenesis of thrombosis

Staphylococci are responsible for many infections in humans, starting with skin and soft tissue infections and finishing with invasive diseases such as endocarditis, sepsis and pneumonia, which lead to high mortality. Patients with sepsis often demonstrate activated clotting pathways, decreased levels of anticoagulants, decreased fibrinolysis, activated endothelial surfaces and activated platelets. This results in disseminated intravascular coagulation and formation of a microthrombus, which can lead to a multiorgan failure. This review describes various staphylococcal virulence factors that contribute to vascular thrombosis, including deep vein thrombosis in infected patients. The article presents mechanisms of action of different factors released by bacteria in various host defense lines, which in turn can lead to formation of blood clots in the vessels.

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.

Antimicrobial resistance of Enterobacteriaceae and Staphylococcus spp. isolated from raw cow's milk from healthy, clinical and subclinical mastitis udders

Mastitis is the most common disease of dairy cattle and can be manifested in clinical and subclinical forms. The overuse of antimicrobials in the treatment and prevention of mastitis favours antimicrobial resistance and milk can be a potential route of dissemination. This study aimed to evaluate the biological quality of bulk tank milk (BTM) and the microbiological quality and signs of mastitis of freshly milked raw milk. In addition, to evaluate antimicrobial resistance in Enterobacteriaceae and Staphylococcus spp. isolated from freshly milked raw milk. None of the farms were within the official Brazilian biological quality limits for BTM. Freshly milked raw milk with signs of clinical (CMM), subclinical (SCMM) and no signs (MFM) of mastitis were detected in 6.67%, 27.62% and 65.71% samples, respectively. Most samples of freshly milked raw milk showed acceptable microbiological quality, when evaluating the indicators total coliforms (78.10%), Escherichia coli (88.57%) and Staphylococcus aureus (100%). Klebsiella oxytoca and S. aureus were the most prevalent microorganisms in SCMM and MFM samples. Antimicrobial resistance and multidrug resistance (MDR) were observed in 65.12% and 13.95% of Enterobacteriaceae and 84.31% and 5.88% of Staphylococcus spp., respectively, isolated from both SCMM and MFM samples. Enterobacteriaceae resistant to third-generation cephalosporin (3GCR) (6.98%) and carbapenems (CRE) (6.98%) and methicillin-resistant S. aureus (MRSA) (4.88%) were observed. Antimicrobial-resistant bacteria can spread resistance genes to previously susceptible bacteria. This is a problem that affects animal, human and environmental health and should be evaluated within the one-health concept.

The mobilome of Staphylococcus aureus from wild ungulates reveals epidemiological links at the animal-human interface

Staphylococcus aureus thrives at animal-human-environment interfaces. A large-scale work from our group indicated that antimicrobial resistance (AMR) in commensal S. aureus strains from wild ungulates is associated with agricultural land cover and livestock farming, raising the hypothesis that AMR genes in wildlife strains may originate from different hosts, namely via exchange of mobile genetic elements (MGE). In this work, we generate the largest available dataset of S. aureus draft genomes from wild ungulates in Portugal and explore their mobilome, which can determine important traits such as AMR, virulence, and host specificity, to understand MGE exchange. Core genome multi-locus sequence typing based on 98 newly generated draft genomes and 101 publicly available genomes from Portugal demonstrated that the genomic relatedness of S. aureus from wild ungulates assigned to livestock-associated sequence types (ST) is greater compared to wild ungulate isolates assigned to human-associated STs. Screening of host specificity determinants disclosed the unexpected presence in wildlife of the immune evasion cluster encoded in φSa3 prophage, described as a human-specific virulence determinant. Additionally, two plasmids, pAVX and pETB, previously associated with avian species and humans, respectively, and the Tn553 transposon were detected. Both pETB and Tn553 encode penicillin resistance through blaZ. Pangenome analysis of wild ungulate isolates shows a core genome fraction of 2133 genes, with isolates assigned to ST72 and ST3224 being distinguished from the remaining by MGEs, although there is no reported role of these in adaptation to wildlife. AMR related gene clusters found in the shell genome are directly linked to resistance against penicillin, macrolides, fosfomycin, and aminoglycosides, and they represent mobile ARGs. Altogether, our findings support epidemiological interactions of human and non-human hosts at interfaces, with MGE exchange, including AMR determinants, associated with putative indirect movements of S. aureus among human and wildlife hosts that might be bridged by livestock.

Investigation of activation-induced markers (AIM) in porcine T cells by flow cytometry

Activation-induced markers (AIMs) are frequently analyzed to identify re-activated human memory T cells. However, in pigs the analysis of AIMs is still not very common. Based on available antibodies, we designed a multi-color flow cytometry panel comprising pig-specific or cross-reactive antibodies against CD25, CD69, CD40L (CD154), and ICOS (CD278) combined with lineage/surface markers against CD3, CD4, and CD8α. In addition, we included an antibody against tumor necrosis factor alpha (TNF-α), to study the correlation of AIM expression with the production of this abundant T cell cytokine. The panel was tested on peripheral blood mononuclear cells (PBMCs) stimulated with phorbol 12-myristate 13-acetate (PMA)/ionomycin, Staphylococcus enterotoxin B (SEB) or PBMCs from African swine fever virus (ASFV) convalescent pigs, restimulated with homologous virus. PMA/ionomycin resulted in a massive increase of CD25/CD69 co-expressing T cells of which only a subset produced TNF-α, whereas CD40L expression was largely associated with TNF-α production. SEB stimulation triggered substantially less AIM expression than PMA/ionomycin but also here CD25/CD69 expressing T cells were identified which did not produce TNF-α. In addition, CD40L-single positive and CD25+CD69+CD40L+TNF-α- T cells were identified. In ASFV restimulated T cells TNF-α production was associated with a substantial proportion of AIM expressing T cells but also here ASFV-reactive CD25+CD69+TNF-α- T cells were identified. Within CD8α+ CD4 T cells, several CD25/CD40L/CD69/ICOS defined phenotypes expanded significantly after ASFV restimulation. Hence, the combination of AIMs tested will allow the identification of primed T cells beyond the commonly used cytokine panels, improving capabilities to identify the full breadth of antigen-specific T cells in pigs.

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.

Trauma-toxicology: concepts, causes, complications

Trauma and toxic substances are connected in several aspects. On the one hand, toxic substances can be the reason for traumatic injuries in the context of accidental or violent and criminal circumstances. Examples for the first scenario is the release of toxic gases, chemicals, and particles during house fires, and for the second scenario, the use of chemical or biological weapons in the context of terroristic activities. Toxic substances can cause or enhance severe, life-threatening trauma, as described in this review for various chemical warfare, by inducing a tissue trauma accompanied by break down of important barriers in the body, such as the blood-air or the blood-gut barriers. This in turn initiates a "vicious circle" as the contribution of inflammatory responses to the traumatic damage enhances the macro- and micro-barrier breakdown and often results in fatal outcome. The development of sophisticated methods for detection and identification of toxic substances as well as the special treatment of the intoxicated trauma patient is summarized in this review. Moreover, some highly toxic substances, such as the protein toxins from the pathogenic bacterium Clostridioides (C.) difficile, cause severe post-traumatic complications which significantly worsens the outcome of hospitalized patients, in particular in multiply injured trauma patients. Therefore, novel pharmacological options for the treatment of such patients are necessarily needed and one promising strategy might be the neutralization of the toxins that cause the disease. This review summarizes recent findings on the molecular and cellular mechanisms of toxic chemicals and bacterial toxins that contribute to barrier breakdown in the human body as wells pharmacological options for treatment, in particular in the context of intoxicated trauma patients. "trauma-toxicology" comprises concepts regrading basic research, development of novel pharmacological/therapeutic options and clinical aspects in the complex interplay and "vicious circle" of severe tissue trauma, barrier breakdown, pathogen and toxin exposure, tissue damage, and subsequent clinical complications.

In vitro co-culture of Clostridium scindens with primary human colonic epithelium protects the epithelium against Staphylococcus aureus

A complex and dynamic network of interactions exists between human gastrointestinal epithelium and intestinal microbiota. Therefore, comprehending intestinal microbe-epithelial cell interactions is critical for the understanding and treatment of intestinal diseases. Primary human colonic epithelial cells derived from a healthy human donor were co-cultured with Clostridium scindens (C. scindens), a probiotic obligate anaerobe; Staphylococcus aureus (S. aureus), a facultative anaerobe and intestinal pathogen; or both bacterial species in tandem. The co-culture hanging basket platform used for these experiments possessed walls of controlled oxygen (O2) permeability to support the formation of an O2 gradient across the intestinal epithelium using cellular O2 consumption, resulting in an anaerobic luminal and aerobic basal compartment. Both the colonic epithelial cells and C. scindens remained viable over 48 h during co-culture. In contrast, co-culture with S. aureus elicited significant damage to colonic epithelial cells within 24 h. To explore the influence of the intestinal pathogen on the epithelium in the presence of the probiotic bacteria, colonic epithelial cells were inoculated sequentially with the two bacterial species. Under these conditions, C. scindens was capable of repressing the production of S. aureus enterotoxin. Surprisingly, although C. scindens converted cholic acid to secondary bile acids in the luminal medium, the growth of S. aureus was not significantly inhibited. Nevertheless, this combination of probiotic and pathogenic bacteria was found to benefit the survival of the colonic epithelial cells compared with co-culture of the epithelial cells with S. aureus alone. This platform thus provides an easy-to-use and low-cost tool to study the interaction between intestinal bacteria and colonic cells in vitro to better understand the interplay of intestinal microbiota with human colonic epithelium.

Comprehensive whole genome analysis of Staphylococcus aureus isolates from dairy cows with subclinical mastitis

Staphylococcus species are the primary cause of mastitis in dairy cows across the world. Staphylococcus aureus has recently become a pathogen that is zoonotic and multidrug resistant. This study aimed to sequence whole genomes of 38 S. aureus isolates from 55 subclinical mastitis dairy cows of 7 small-scale farmers in the Free State Province, South Africa and document and their antimicrobial and virulence genes. The 38 isolates were grouped by the in silico multi-locus sequencing types (MLST) into seven sequence types (STs), that is (ST 97, 352, 152, 243) and three new STs (ST8495, ST8500, and ST8501). Thirty-three S. aureus isolates were divided into 7 core single-nucleotide polymorphism (SNP) clusters. Among the 9 distinct spa-types that were detected, Spa-types t2883 accounted for the majority of isolates at 12 (31.57%), followed by t416 with 11 (28.94%) and t2844 with 5 (13.15%). The data also revealed the identification of four (4) plasmids, with Rep_N (rep20) accounting for the majority of isolates with 17 (44.73%), followed by Inc18 (repUS5) with 2 (5.26%). These isolates included 11 distinct antimicrobial resistance genes and 23 genes linked to bacterial virulence. Surprisingly, no methicillin resistance associated genes were detected in these isolates. Genome data of the current study will contribute to understanding epidemiology S. aureus genotypes and ultimately aid in developing treatment and control plans to stop the spread of mastitis in the Free State province and South Africa as a whole.

Staphylococcus Scalded Skin Syndrome-Induced Thrombosis Leading to Free Flap Complications: A Case Report and Review

Staphylococcal scalded skin syndrome (SSSS) is a clinical term used for a spectrum of blistering skin conditions induced by the epidermolytic toxins of the Staphylococcus aureus bacteria. The complications of SSSS include thrombosis; however, the pathophysiology of this is still poorly understood. We present a case of free anterolateral thigh (ALT) flap failure in a patient as a result of widespread flap thrombosis associated with staphylococcal scalded skin syndrome (SSSS). This is the first reported case of free flap failure associated with SSSS. Free flap failure due to acquired prothrombotic conditions, such as infection, is a rare and potentially under-reported phenomenon. This article aims to further explore the role of both thrombophilias and provoked thrombotic events in free flap failure. A review of the literature will also be presented, and cases of free flap failure in patients with infection-induced vascular complications will be summarised.

Targeting staphylococcal enterotoxin B binding to CD28 as a new strategy for dampening superantigen-mediated intestinal epithelial barrier dysfunctions

Staphylococcus aureus is a gram-positive bacterium that may cause intestinal inflammation by secreting enterotoxins, which commonly cause food-poisoning and gastrointestinal injuries. Staphylococcal enterotoxin B (SEB) acts as a superantigen (SAg) by binding in a bivalent manner the T-cell receptor (TCR) and the costimulatory receptor CD28, thus stimulating T cells to produce large amounts of inflammatory cytokines, which may affect intestinal epithelial barrier integrity and functions. However, the role of T cell-mediated SEB inflammatory activity remains unknown. Here we show that inflammatory cytokines produced by T cells following SEB stimulation induce dysfunctions in Caco-2 intestinal epithelial cells by promoting actin cytoskeleton remodelling and epithelial cell-cell junction down-regulation. We also found that SEB-activated inflammatory T cells promote the up-regulation of epithelial-mesenchymal transition transcription factors (EMT-TFs) in a nuclear factor-κB (NF-κB)- and STAT3-dependent manner. Finally, by using a structure-based design approach, we identified a SEB mimetic peptide (pSEB116-132) that, by blocking the binding of SEB to CD28, dampens inflammatory-mediated dysregulation of intestinal epithelial barrier.

From Host Defense to Metabolic Signatures: Unveiling the Role of γδ T Cells in Bacterial Infections

The growth of antibiotic-resistant bacterial infections necessitates focusing on host-derived immunotherapies. γδ T cells are an unconventional T cell subset, making up a relatively small portion of healthy circulating lymphocytes but a substantially increased proportion in mucosal and epithelial tissues. γδ T cells are activated and expanded in response to bacterial infection, having the capability to produce proinflammatory cytokines to recruit neutrophils and clear infection. They also play a significant role in dampening immune response to control inflammation and protecting the host against secondary challenge, making them promising targets when developing immunotherapy. Importantly, γδ T cells have differential metabolic states influencing their cytokine profile and subsequent inflammatory capacity. Though these differential metabolic states have not been well studied or reviewed in the context of bacterial infection, they are critical in understanding the mechanistic underpinnings of the host's innate immune response. Therefore, this review will focus on the context-specific host defense conferred by γδ T cells during infection with Staphylococcus aureus, Streptococcus pneumoniae, Listeria monocytogenes, and Mycobacterium tuberculosis.

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.

Ophthalmic implications of biological threat agents according to the chemical, biological, radiological, nuclear, and explosives framework

As technology continues to evolve, the possibility for a wide range of dangers to people, organizations, and countries escalate globally. The United States federal government classifies types of threats with the capability of inflicting mass casualties and societal disruption as Chemical, Biological, Radiological, Nuclear, and Energetics/Explosives (CBRNE). Such incidents encompass accidental and intentional events ranging from weapons of mass destruction and bioterrorism to fires or spills involving hazardous or radiologic material. All of these have the capacity to inflict death or severe physical, neurological, and/or sensorial disabilities if injuries are not diagnosed and treated in a timely manner. Ophthalmic injury can provide important insight into understanding and treating patients impacted by CBRNE agents; however, improper ophthalmic management can result in suboptimal patient outcomes. This review specifically addresses the biological agents the Center for Disease Control and Prevention (CDC) deems to have the greatest capacity for bioterrorism. CBRNE biological agents, encompassing pathogens and organic toxins, are further subdivided into categories A, B, and C according to their national security threat level. In our compendium of these biological agents, we address their respective CDC category, systemic and ophthalmic manifestations, route of transmission and personal protective equipment considerations as well as pertinent vaccination and treatment guidelines.

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.

Species comparison: human and minipig PBMC reactivity under the influence of immunomodulating compounds in vitro

Considering the similarities between swine and humans, it is a logical consequence to use swine as a translational model in research and drug development, including non-clinical safety. Here, we compared the reactivity of peripheral blood mononuclear cells (PBMCs) from humans and minipigs under the influence of different compounds in vitro. We conducted a flow cytometry-based proliferation assay that focused on the T-cell response to three different stimuli: concanavalin A (ConA), phytohemagglutinin-L (PHA-L), and staphylococcal Enterotoxin B (SEB). Furthermore, four approved immunosuppressive drugs-abatacept, belatacept, rapamycin, and tofacitinib-which are used for the treatment of rheumatoid arthritis or rejection in transplant recipients, were combined with the different stimuli. This allowed us to study the effect of suppressive drugs in comparison with the different stimuli in both species. We examined proliferating T cells (CD3+) and investigated the presence of TCR-αβ+ and TCR-γδ+ T cells. Differences in the response of T cells of the two species under these various conditions were evident. CD4+ T cells were more activated within humans, whereas CD8+ T cells were generally more abundant in swine. The effectiveness of the used humanized antibodies is most likely related to the conserved structure of CTLA-4 as abatacept induced a much stronger reduction in swine compared with belatacept. The reduction of proliferation of rapamycin and tofacitinib was highly dependent on the used stimuli. We further investigated the effect of the immunosuppressive compounds on antigen-specific restimulation of pigs immunized against porcine circovirus 2 (PCV2). Treatment with all four compounds resulted in a clear reduction of the proliferative response, with rapamycin showing the strongest effect. In conclusion, our findings indicate that the effectiveness of suppressive compounds is highly dependent on the stimuli used and must be carefully selected to ensure accurate results. The results highlight the importance of considering the response of T cells in different species when evaluating the potential of an immunomodulatory drug.

Genotypic diversity of staphylococcal enterotoxin B gene (seb) and its association with molecular characterization and antimicrobial resistance of Staphylococcus aureus from retail food

To investigate the expression pattern of staphylococcal enterotoxin B (SEB) in food and the genotypic diversity of SEB-encoding gene in association with molecular characteristics and antimicrobial resistance of S. aureus, 498 isolates from retail food were screened for seb gene and detected for SEB production in S. aureus. In addition, the seb nucleotide sequences, virulence genes, resistance genes, antimicrobial susceptibility and molecular characteristics of S. aureus were examined. A total of 45 (9.0 %) seb-positive S. aureus strains were identified, all of which expressed SEB. The detection rate of SEB-production strains was significantly higher from dairy-related sources than those from other sources (P < 0.05). In vitro simulations showed that S. aureus could grow and express SEB in both milk and pork, with SEB expression exceeding 20 ng/g after 1 day of storage at room temperature. There were 2 distinct SEB genotyping (SEB1 and SEB2) in the SEB amino acid sequences of the 45 isolates, including 4 amino acid differences (Ala-13Val, Ser14Ala, Asn192Ser, and Met222Leu). There was no significant difference (P > 0.05) in SEB production between SEB1 and SEB2 genotyping strains. Based on MLST clustering analysis, the same molecular type strains were found to have the same SEB genotyping, virulence gene profile, resistance gene profile and drug resistance profile. Among them, the dominant molecular types of SEB1 and SEB2 strains were CC1-ST188-t189 and CC59-ST59-t437, respectively. Compared to the CC1-ST188-t189 clonal strain, the CC59-ST59-t437 clonal strain carried a higher number of virulence and resistance genes and exhibited a broader resistance profile. Therefore, understanding the characteristics of the strains and their expression patterns in food can be effective in preventing food poisoning incidents.

Staphylococcus aureus-derived virulent phenol-soluble modulin α triggers alarmin release to drive IL-36-dependent corneal inflammation

Methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients with keratitis produces substantial amounts of phenol-soluble modulin α (PSMα). However, the role of PSMα in S. aureus keratitis remains unclear. We observed that PSMα-producing and PSMα-deficient strains could infect the cornea in our experimental mouse keratitis model; however, only the PSMα-producing strain delayed epithelial wound healing and induced stromal inflammation. PSMα induced damage to the epithelium, the release of alarmins IL-1α and IL-36α, and the expression of inflammatory chemokines by resident corneal cells in the mouse corneal organ culture. The IL-36 (but not IL-1) receptor antagonist attenuated mouse keratitis induced by PSMα-containing bacterial culture supernatants, as well as by infection with PSMα-producing S. aureus, suggesting that the corneal inflammations were dependent on IL-36. Recombinant PSMα elicited IL-36-dependent corneal inflammation in mice. Thus, PSMα and the subsequently released IL-36 are critical factors triggering inflammation during S. aureus keratitis.

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.

Clonal Diversity, Antibiotic Resistance, and Virulence Factor Prevalence of Community Associated Staphylococcus aureus in Southeastern Virginia

Staphylococcus aureus is a significant human pathogen with a formidable propensity for antibiotic resistance. Worldwide, it is the leading cause of skin and soft tissue infections (SSTI), septic arthritis, osteomyelitis, and infective endocarditis originating from both community- and healthcare-associated settings. Although often grouped by methicillin resistance, both methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) strains are known to cause significant pathologies and injuries. Virulence factors and growing resistance to antibiotics play major roles in the pathogenicity of community-associated strains. In our study, we examined the genetic variability and acquired antibiograms of 122 S. aureus clinical isolates from SSTI, blood, and urinary tract infections originating from pediatric patients within the southeast region of Virginia, USA. We identified a suite of clinically relevant virulence factors and evaluated their prevalence within these isolates. Five genes (clfA, spA, sbi, scpA, and vwb) with immune-evasive functions were identified in all isolates. MRSA isolates had a greater propensity to be resistant to more antibiotics as well as significantly more likely to carry several virulence factors compared to MSSA strains. Further, the carriage of various genes was found to vary significantly based on the infection type (SSTI, blood, urine).

Microbiome in Cancer Development and Treatment

Targeting the microbiome, microbiota-derived metabolites, and related pathways represents a significant challenge in oncology. Microbiome analyses have confirmed the negative impact of cancer treatment on gut homeostasis, resulting in acute dysbiosis and severe complications, including massive inflammatory immune response, mucosal barrier disruption, and bacterial translocation across the gut epithelium. Moreover, recent studies revealed the relationship between an imbalance in the gut microbiome and treatment-related toxicity. In this review, we provide current insights into the role of the microbiome in tumor development and the impact of gut and tumor microbiomes on chemo- and immunotherapy efficacy, as well as treatment-induced late effects, including cognitive impairment and cardiotoxicity. As discussed, microbiota modulation via probiotic supplementation and fecal microbiota transplantation represents a new trend in cancer patient care, aiming to increase bacterial diversity, alleviate acute and long-term treatment-induced toxicity, and improve the response to various treatment modalities. However, a more detailed understanding of the complex relationship between the microbiome and host can significantly contribute to integrating a microbiome-based approach into clinical practice. Determination of causal correlations might lead to the identification of clinically relevant diagnostic and prognostic microbial biomarkers. Notably, restoration of intestinal homeostasis could contribute to optimizing treatment efficacy and improving cancer patient outcomes.

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.

Meta-Analysis of the Prevalence of Porcine Zoonotic Bacterial Pathogens in India: A 13-Year (2010-2023) Study

The presence of bacterial pathogens such as Brucella spp., Clostridium spp., E. coli, Listeria monocytogenes, Salmonella spp., Staphylococcus spp., and Streptococcus suis not only hampers pig production but also carries significant zoonotic implications. The present study aims to conduct a comprehensive meta-analysis spanning over 13 years (2010-2023) to ascertain the prevalence of these zoonotic bacterial pathogens in Indian pig populations. The study seeks to synthesize data from diverse geographic regions within India and underscores the relevance of the One Health framework. A systematic search of electronic databases was meticulously performed. Inclusion criteria encompassed studies detailing zoonotic bacterial pathogen prevalence in pigs within India during the specified timeframe. Pertinent information including authors, publication year, geographical location, sampling techniques, sample sizes, and pathogen-positive case counts were meticulously extracted. The meta-analysis of zoonotic bacterial pathogens in Indian pig populations (2010-2023) unveiled varying prevalence rates: 9% Brucella spp., 22% Clostridium spp., 19% E. coli, 12% Listeria monocytogenes, 10% Salmonella spp. and Streptococcus suis, and 24% Staphylococcus spp. The application of random effects further revealed additional variability: 6% Brucella spp., 23% Clostridium spp., 24% E. coli, 14% Listeria monocytogenes, 10% Salmonella spp. and Streptococcus suis, and 35% Staphylococcus spp. Notably, the observed heterogeneity (I2) varied significantly from 87% to 99%. The meta-analysis findings underscore the pervasive nature of these diseases throughout India's pig populations, accentuating the substantial impact of these pathogens on pig health and the potential for zoonotic transmission. The present study reinforces the importance of the adoption of a comprehensive One Health approach that acknowledges the intricate interplay between animal, human and environmental health.

Macrolide-Lincosamide Resistance and Virulence Genes in Staphylococcus aureus Isolated from Clinical Specimens in Ardabil, Iran

Background & Objective

Staphylococcus aureus causes various hospital- and community-acquired infections. This study aimed to investigate the phenotypic and genotypic characteristics of erythromycin and inducible clindamycin resistance, virulence gene profiles, and spa types of S. aureus isolates collected from patients in Ardabil Province, Iran.

Methods

A total of 118 clinical S. aureus isolates, including 50 (42.4%) methicillin-resistant S. aureus (MRSA) and 68 (57.6%) methicillin-susceptible S. aureus (MSSA) strains, were investigated. Resistance patterns were determined by the disk diffusion method and minimum inhibitory concentration (MIC) test. Inducible macrolide-lincosamide-streptogramin B (iMLSB) resistance was detected using D-test method. The polymerase chain reaction (PCR) was used to identify the virulence and resistance-encoding genes. Additionally, the spa types of the isolates were determined using the PCR, followed by sequencing.

Results

In total, 49.1% (58/118) and 44% (52/118) of the isolates were resistant to erythromycin and clindamycin, respectively. Overall, 13.5% (16/118) of the isolates showed the iMLSB resistance phenotype. The ermC gene (72.4% [42]) was the most frequent erythromycin resistance-encoding gene, followed by ermA (60.3% [35]), ermB (60.3% [35]), ermTR (51.7% [30]), and msrA (15.5% [9]) genes among erythromycin-resistant isolates. The virulence genes hla, hld, sea, LukS PV, tst, seb, sed, eta, sec, and etb were detected in 93.2%, 74.5%, 70.3%, 32.2%, 29.6%, 17%, 8.5%, 8.5%, 5.9%, and 4.2% of the isolates, respectively. Ten different spa types were identified for 58 erythromycin-resistant S. aureus strains, of which t030 and t078 types were the most common types.

Conclusion

A high frequency of macrolide- and lincosamide-resistant S. aureus isolates with different genetic backgrounds of resistance and virulence may be found in patients in Ardabil Province, Iran.

Low-Dose Staphylococcal Enterotoxin C2 Mutant Maintains Bone Homeostasis via Regulating Crosstalk between Bone Formation and Host T-Cell Effector Immunity

Studies in recent years have highlighted an elaborate crosstalk between T cells and bone cells, suggesting that T cells may be alternative therapeutic targets for the maintenance of bone homeostasis. Here, it is reported that systemic administration of low-dose staphylococcal enterotoxin C2 (SEC2) 2M-118, a form of mutant superantigen, dramatically alleviates ovariectomy (OVX)-induced bone loss via modulating T cells. Specially, SEC2 2M-118 treatment increases trabecular bone mass significantly via promoting bone formation in OVX mice. These beneficial effects are largely diminished in T-cell-deficient nude mice and can be rescued by T-cell reconstruction. Neutralizing assays determine interferon gamma (IFN-γ) as the key factor that mediates the beneficial effects of SEC2 2M-118 on bone. Mechanistic studies demonstrate that IFN-γ stimulates Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling, leading to enhanced production of nitric oxide, which further activates p38 mitogen-activated protein kinase (MAPK) and Runt-related transcription factor 2 (Runx2) signaling and promotes osteogenic differentiation. IFN-γ also directly inhibits osteoclast differentiation, but this effect is counteracted by proabsorptive factors tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) secreted from IFN-γ-stimulated macrophages. Taken together, this work provides clues for developing innovative approaches which target T cells for the prevention and treatment of osteoporosis.

Prevalence and Characteristics of Invasive Staphylococcus argenteus among Patients with Bacteremia in Hong Kong

Staphylococcus argenteus is a novel Staphylococcus species derived from Staphylococcus aureus. Information on the prevalence and genetic characteristics of invasive S. argenteus in Asia is limited. In this study, 275 invasive S. aureus complex strains were retrieved from blood culture specimens in Hong Kong and re-analyzed using MALDI-TOF mass spectrometry and an in-house multiplex real-time PCR for S. argenteus. The prevalence of invasive S. argenteus in Hong Kong was found to be 4.0% (11/275). These strains were primarily susceptible to commonly used antibiotics, except penicillin. Whole-genome sequencing revealed the circulation of three S. argenteus genotypes (ST-2250, ST-1223, and ST-2854) in Hong Kong, with ST-2250 and ST-1223 being the predominant genotypes. The local ST-2250 and ST-1223 strains showed close phylogenetic relationships with isolates from mainland China. Antimicrobial-resistant genes (fosB, tet-38, mepA, blaI, blaZ) could be found in nearly all local S. argenteus strains. The ST-1223 and ST-2250 genotypes carried multiple staphylococcal enterotoxin genes that could cause food poisoning and toxic shock syndrome. The CRISPR/Cas locus was observed only in the ST-2250 strains. This study provides the first report on the molecular epidemiology of invasive S. argenteus in Hong Kong, and further analysis is needed to understand its transmission reservoir.

Staphylococcus aureus enterotoxin A- and B-specific IgE in chronic obstructive pulmonary disease

Sensitization to Staphylococcus aureus enterotoxins A (SEA) and B (SEB) has been associated with asthma severity, exacerbations, and disease control. Our study aimed to investigate if there are differences in serum SEA-IgE and SEB-IgE levels between patients with chronic obstructive pulmonary disease (COPD), asthma, and controls, and to assess the association between SE sensitization and COPD clinical parameters and Th2 inflammation biomarkers in two well-defined COPD cohorts. Our findings suggest that COPD patients do not exhibit higher SEA and SEB sensitization compared to asthma patients and controls. However, in COPD patients, the presence of atopy and allergy is associated with positivity for SEA-IgE and SEB-IgE. Consequently, these allergens may aid in identifying atopic or allergic subgroups within the COPD population, but they are not directly associated with the diagnosis of COPD, elevated circulating blood eosinophils, or fractional exhaled nitric oxide (FENO) levels.

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.

Genomic characterization of Staphylococcus aureus from Canastra Minas Artisanal Cheeses

Canastra Minas Artisanal Cheese is produced in the Brazilian State of Minas Gerais using raw milk, rennet, and pingo, a natural endogenous starter culture (fermented whey) collected from the previous day's production. Due to the use of raw milk, the product can carry microorganisms that may cause foodborne diseases (FBD), including Staphylococcus aureus. Genomic characterization of S. aureus is an important tool to assess diversity, virulence, antimicrobial resistance, and the potential for causing food poisoning due to enterotoxin production. This study is aimed at exploring the genomic features of S. aureus strains isolated from Canastra Minas Artisanal Cheeses. Multilocus sequence typing (MLST) classified these strains as ST1, ST5, and a new profile ST7849 (assigned to the clonal complex CC97). These strains belonged to four spa types: t008, t127, t359, and t992. We identified antimicrobial resistance genes with phenotypic correlation against methicillin (MRSA) and tetracycline. Virulome analysis revealed genes associated with iron uptake, immune evasion, and potential capacity for adherence and biofilm formation. The toxigenic potential included cyto- and exotoxins genes, and all strains presented the genes that encode for Panton-Valentine toxin and hemolysin, and two strains encoded 4 and 8 Staphylococcal enterotoxin (SE) genes. The results revealed the pathogenic potential of the evaluated S. aureus strains circulating in the Canastra region, representing a potential risk to public health. This study also provides useful information to monitor and guide the application of control measures to the artisanal dairy food production chain.