Staphylococcal enterotoxins

Secretory proteins in the orchestration of microbial virulence: The curious case of Staphylococcus aureus

Microbial virulence showcases an excellent model for adaptive changes that enable an organism to survive and proliferate in a hostile environment and exploit host resources to its own benefit. In Staphylococcus aureus, an opportunistic pathogen of the human host, known for the diversity of the disease conditions it inflicts and the rapid evolution of antibiotic resistance, virulence is a consequence of having a highly plastic genome that is amenable to quick reprogramming and the ability to express a diverse arsenal of virulence factors. Virulence factors that are secreted to the host milieu effectively manipulate the host conditions to favor bacterial survival and growth. They assist in colonization, nutrient acquisition, immune evasion, and systemic spread. The structural and functional characteristics of the secreted virulence proteins have been shaped to assist S. aureus in thriving and disseminating effectively within the host environment and exploiting the host resources to its best benefit. With the aim of highlighting the importance of secreted virulence proteins in bacterial virulence, the present chapter provides a comprehensive account of the role of the major secreted proteins of S. aureus in orchestrating its virulence in the human host.

Aggregation-Induced Red Emission Nanoparticle-Based Lateral Flow Immunoassay for Highly Sensitive Detection of Staphylococcal Enterotoxin A

Staphylococcal enterotoxin A (SEA) has presented enormous difficulties in dairy food safety and the sensitive detection of SEA provides opportunities for effective food safety controls and staphylococcal food poisoning tracebacks. Herein, a novel aggregation-induced emission (AIE)-based sandwich lateral flow immunoassay (LFIA) was introduced to detect SEA by using red-emissive AIE nanoparticles (AIENPs) as the fluorescent nanoprobe. The nanoprobe was constructed by directly immobilising antibodies on boronate-tagged AIENPs (PBA-AIENPs) via a boronate affinity reaction, which exhibited a high SEA-specific affinity and remarkable fluorescent performance. Under optimal conditions, the ultrasensitive detection of SEA in pasteurised milk was achieved within 20 min with a limit of detection of 0.04 ng mL^-1. The average recoveries of the PBA-AIENP-LFIA ranged from 91.3% to 117.6% and the coefficient of variation was below 15%. It was also demonstrated that the PBA-AIENP-LFIA had an excellent selectivity against other SE serotypes. Taking advantage of the excellent sensitivity of this approach, real chicken and salad samples were further analysed, with a high versatility and accuracy. The proposed PBA-AIENP-LFIA platform shows promise as a potent tool for the identification of additional compounds in food samples as well as an ideal test method for on-site detections.

The Role of Staphylococcus aureus and Its Toxins in the Pathogenesis of Allergic Asthma

Bronchial asthma is one of the most common chronic diseases worldwide and affects more than 300 million patients. Allergic asthma affects the majority of asthmatic children as well as approximately 50% of adult asthmatics. It is characterized by a Th2-mediated immune response against aeroallergens. Many aspects of the overall pathophysiology are known, while the underlying mechanisms and predisposing factors remain largely elusive today. Over the last decade, respiratory colonization with Staphylococcus aureus (S. aureus), a Gram-positive facultative bacterial pathogen, came into focus as a risk factor for the development of atopic respiratory diseases. More than 30% of the world’s population is constantly colonized with S. aureus in their nasopharynx. This colonization is mostly asymptomatic, but in immunocompromised patients, it can lead to serious complications including pneumonia, sepsis, or even death. S. aureus is known for its ability to produce a wide range of proteins including toxins, serine-protease-like proteins, and protein A. In this review, we provide an overview of the current knowledge about the pathophysiology of allergic asthma and to what extent it can be affected by different toxins produced by S. aureus. Intensifying this knowledge might lead to new preventive strategies for atopic respiratory diseases.

Review on skeletal disorders caused by Staphylococcus spp. in poultry

Lameness or leg weakness is the main cause of poor poultry welfare and serious economic losses in meat-type poultry production worldwide. Disorders related to the legs are often associated with multifactorial aetiology which makes diagnosis and proper treatment difficult. Among the infectious agents, bacteria of genus Staphylococcus are one of the most common causes of bone infections in poultry and are some of the oldest bacterial infections described in poultry. Staphylococci readily infect bones and joints and are associated with bacterial chondronecrosis with osteomyelitis (BCO), spondylitis, arthritis, tendinitis, tenosynovitis, osteomyelitis, turkey osteomyelitis complex (TOC), bumblefoot, dyschondroplasia with osteomyelitis and amyloid arthropathy. Overall, 61 staphylococcal species have been described so far, and 56% of them (34/61) have been isolated from clinical cases in poultry. Although Staphylococcus aureus is the principal cause of poultry staphylococcosis, other Staphylococcus species, such as S. agnetis, S. cohnii, S. epidermidis, S. hyicus, S. simulans, have also been isolated from skeletal lesions. Antimicrobial treatment of staphylococcosis is usually ineffective due to the location and type of lesion, as well as the possible occurrence of multidrug-resistant strains. Increasing demand for antibiotic-free farming has contributed to the use of alternatives to antibiotics. Other prevention methods, such as better management strategies, early feed restriction or use of slow growing broilers should be implemented to avoid rapid growth rate, which is associated with locomotor problems. This review aims to summarise and address current knowledge on skeletal disorders associated with Staphylococcus spp. infection in poultry.

Phage display for the detection, analysis, disinfection, and prevention of Staphylococcus aureus

The World Health Organization has designated Staphylococcus aureus as a global health concern. This designation stems from the emergence of multiple drug-resistant strains that already account for hundreds of thousands of deaths globally. The development of novel treatment strategies to eradicate S. aureus or mitigate its pathogenic potential is desperately needed. In the effort to develop emerging strategies to combat S. aureus, phage display is uniquely positioned to assist in this endeavor. Leveraging bacteriophages, phage display enables researchers to better understand interactions between proteins and their antagonists. In doing so, researchers have the capacity to design novel inhibitors, biosensors, disinfectants, and immune modulators that can target specific S. aureus strains. In this review, we highlight how phage display can be leveraged to design novel solutions to combat S. aureus. We further discuss existing uses of phage display as a detection, intervention, and prevention platform against S. aureus and provide outlooks on how this technology can be optimized for future applications.

Superantigens, a Paradox of the Immune Response

Staphylococcal enterotoxins are a wide family of bacterial exotoxins with the capacity to activate as much as 20% of the host T cells, which is why they were called superantigens. Superantigens (SAgs) can cause multiple diseases in humans and cattle, ranging from mild to life-threatening infections. Almost all S. aureus isolates encode at least one of these toxins, though there is no complete knowledge about how their production is triggered. One of the main problems with the available evidence for these toxins is that most studies have been conducted with a few superantigens; however, the resulting characteristics are attributed to the whole group. Although these toxins share homology and a two-domain structure organization, the similarity ratio varies from 20 to 89% among different SAgs, implying wide heterogeneity. Furthermore, every attempt to structurally classify these proteins has failed to answer differential biological functionalities. Taking these concerns into account, it might not be appropriate to extrapolate all the information that is currently available to every staphylococcal SAg. Here, we aimed to gather the available information about all staphylococcal SAgs, considering their functions and pathogenicity, their ability to interact with the immune system as well as their capacity to be used as immunotherapeutic agents, resembling the two faces of Dr. Jekyll and Mr. Hyde.

Virulence Potential and Antibiotic Susceptibility of S. aureus Strains Isolated from Food Handlers

Staphylococcus spp. are common members of the normal human flora. However, some Staphylococcus species are recognised as human pathogens due to the production of several virulence factors and enterotoxins that are particularly worrisome in food poisoning. Since many of Staphylococcal food poisoning outbreaks are typically associated with cross-contamination, the detection of S. aureus on food handlers was performed. Hand swabs from 167 food handlers were analysed for the presence of S. aureus. More than 11% of the samples were positive for S. aureus. All S. aureus strains were isolated and analysed for the presence of virulence and enterotoxin genes, namely, sea, seb, sec, sed, seg, sei, tsst-1 and pvl. The same strains were phenotypically characterised in terms of antibiotic susceptibility using the disc diffusion method and antimicrobial agents from 12 different classes. A low prevalence of antibiotic-resistant strains was found, with 55.6% of the strains being sensitive to all of the antimicrobial agents tested. However, a high prevalence of resistance to macrolides was found, with 44.4% of the strains showing resistance to erythromycin. At least one of the virulence or toxin genes was detected in 61.1% of the strains, and seg was the most prevalent toxin gene, being detected in 44.4% of the strains.

Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China

Methicillin-resistant Staphylococcus aureus (MRSA) causes an enormous illness burden, including skin and soft tissue infections (SSTIs), pneumonia, bloodstream infections (BSI), and sepsis. BSI are associated with significant patient morbidity and mortality worldwide. However, limited information is available on MRSA-related BSI in China. This study aimed to investigate the molecular characterization of 77 MRSA isolates recovered from hospitalized patients with BSI between 2012 and 2020 at three first-class tertiary hospitals in southern China based on multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, 13 clonal complexes (CCs) were identified, with CC59 and CC5 being the largest clusters, indicating high genetic diversity among BSI-causing MRSA isolates. ST59 was the most prevalent MLST type (22.1%). ST5/ST764-MRSA SCCmec II was the predominant adult MRSA clone, whereas ST59-MRSA SCCmec IV was the most common pediatric MRSA clone. ST5-t2460, ST764-t1084, and ST59-t437 were the most common types of adult MRSA isolates, whereas ST59-t437 and ST59-t172 were the predominant types of children’s MRSA isolates. ST59-SCCmec IV/V represented the most common clone among community acquired-MRSA isolates. ST5/ST764-SCCmec II was the most common type of hospital-associated MRSA isolate. The most prevalent toxin-encoding genes detected were hla, hld, icaA, and clfA (96.1–100%). Forty-three (100%, 43/43) isolates harbored more than 18 of the tested virulence genes in adults and eight virulence genes (23.5%, 8/34) in children. Virulence gene analysis revealed diversity among different clones: the positivity rates for the Panton-Valentine leukocidin (PVL) gene were 55.8 and 35.3% in adult and pediatric MRSA isolates, respectively; the genes seb–sei were present in all adult strains; seb–seg–sei–seo were present in all ST5, ST59, ST15, ST45, and ST22 adult strains; and seg–sei–sem–sen–seo were present in different clones, including ST15, ST45, and ST22 adult MRSA isolates and ST25, ST30, ST546, and ST72 children’s MRSA isolates. Adult MRSA isolates had significantly higher antibiotic resistance rates and virulence gene prevalence than pediatric MRSA isolates. For 8 years, this study provided epidemiological data on the molecular characteristics and virulence genes in different groups of MRSA BSI in China. Our findings may provide critical information for a better understanding of MRSA BSI.

A Sensitive Immunodetection Assay Using Antibodies Specific to Staphylococcal Enterotoxin B Produced by Baculovirus Expression

Staphylococcal enterotoxin B (SEB) is a potent bacterial toxin that causes inflammatory stimulation and toxic shock, thus it is necessary to detect SEB in food and environmental samples. Here, we developed a sensitive immunodetection system using monoclonal antibodies (mAbs). Our study is the first to employ a baculovirus expression vector system (BEVS) to produce recombinant wild-type SEB. BEVS facilitated high-quantity and pure SEB production from suspension-cultured insect cells, and the SEB produced was characterized by mass spectrometry analysis. The SEB was stable at 4 °C for at least 2 years, maintaining its purity, and was further utilized for mouse immunization to generate mAbs. An optimal pair of mAbs non-competitive to SEB was selected for sandwich enzyme-linked immunosorbent assay-based immunodetection. The limit of detection of the immunodetection method was 0.38 ng/mL. Moreover, it displayed higher sensitivity in detecting SEB than commercially available immunodetection kits and retained detectability in various matrices and S. aureus culture supernatants. Thus, the results indicate that BEVS is useful for producing pure recombinant SEB with its natural immunogenic property in high yield, and that the developed immunodetection assay is reliable and sensitive for routine identification of SEB in various samples, including foods.

Virulence genes distributed among Staphylococcus aureus causing wound infections and their correlation to antibiotic resistance

Background

Staphylococcus aureus causes many human infections, including wound infections, and its pathogenicity is mainly influenced by several virulence factors.

Aim

This study aimed to detect virulence genes (hla, sea, icaA, and fnbA) in S. aureus isolated from different wound infections among Egyptian patients admitted to Minia University Hospital. This study also aimed to investigate the prevalence of these genes in methicillin-resistant S. aureus (MRSA), methicillin-susceptible S. aureus (MSSA), and vancomycin-resistant S. aureus isolates and the resistance and sensitivity to different antibiotic classes.

Methods

A cross-sectional study was carried out from November 2019 to September 2021. Standard biochemical and microbiological tests revealed 59 S. aureus isolates. The Kirby-Bauer disc diffusion method was used to determine antibiotic susceptibility. DNA was extracted using a DNA extraction kit, and polymerase chain reaction was used to amplify all genes.

Results

A total of 59 S. aureus isolates were detected from 51 wound samples. MRSA isolates accounted for 91.5%, whereas MSSA isolates accounted for 8.5%. The multidrug resistance (MDR) percentage in S. aureus isolates was 54.2%. S. aureus showed high sensitivity pattern against vancomycin, linezolid, and chloramphenicol. However, a high resistance pattern was observed against oxacillin and piperacillin. sea was the most predominant gene (72.9%), followed by icaA (49.2%), hla (37.3%), and fnbA (13.6%). sea was the commonest virulence gene among MRSA isolates (72.2%), and a significant difference in the distribution of icaA was found. However, sea and icaA were the commonest genes among MSSA isolates (79.9%). The highest distribution of sea was found among ciprofloxacin-resistant isolates (95.2%).

Conclusion

The incidence of infections caused by MDR S. aureus significantly increased with MRSA prevalence. sea is the most predominant virulence factor among antibiotic-resistant strains with a significant correlation to piperacillin, gentamicin, and levofloxacin.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07624-8.

Antibiotics Resistance and Virulence of Staphylococcus aureus Isolates Isolated from Raw Milk from Handmade Dairy Retail Stores in Hefei City, China

Handmade dairy products, which retain the nutrients in milk to the greatest extent, have become popular in China recently. However, no investigation regarding the characteristics of Staphylococcus aureus (S. aureus) in raw milk of handmade dairy retail stores has been reported. Here, we investigated the antimicrobial susceptibility, virulence, biofilm formation, and genetic diversity of S. aureus in raw milk from handmade dairy retail stores in Hefei, China. After 10 months of long-term monitoring, 50 S. aureus strains were isolated from 69 different raw milk samples, of which 6 were positive for methicillin-resistant S. aureus (MRSA). The resistance rates of these isolates to ampicillin, erythromycin, kanamycin, tetracycline, sulfamethoxazole-trimethoprim, gentamicin, ofloxacin, oxacillin, chloramphenicol, and doxycycline were 56, 54, 40, 24, 22, 22, 18, 14, 8 and 6%, respectively. All 50 isolates were susceptible to vancomycin and 29 strains (58%) showed multidrug resistance phenotype. For enterotoxins genes, selp (14%) was detected the most frequently, followed by sea (6%), sec (4%), sei (4%), ser (4%), selj (4%), and seh (2%). By microplate assay, 32 and 68% of the strains showed moderate and strong biofilm formation ability, respectively. Fifty isolates were discriminated into nine spa types, and the most common spa typing was t034 (42%). The results of this study indicate that S. aureus from raw milk may constitute a risk concerning food poisoning, and more attention must be given to awareness and hygienic measures in the food industry.

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

Food, particularly milk and cheese, may be a reservoir of multi-drug resistant Staphylococcus aureus strains, which can be considered an important issue in terms of food safety. Furthermore, foods of animal origin can be a cause of staphylococcal food poisoning via the production of heat-stable enterotoxins (SE). For this reason, we investigated the prevalence of and characterized Staphylococcus aureus strains isolated from milk and fresh soft cheese obtained from farms located in Wielkopolskie and Zachodniopomorskie Provinces in Poland. Overall, 92% of S. aureus isolates were positive for at least one of the 18 enterotoxin genes identified, and 26% of the strains harbored 5 to 8 enterotoxin genes. Moreover, the S. aureus strains contained genes conferring resistance to antibiotics that are critically important in both human and veterinary medicine, i.e., β-lactams (mecA), aminoglycosides (aac(6′)/aph(2″), aph(3′)-IIIa, ant(4′)-Ia) and MLS_B (erm(A), msr(A), lun(A)). The antimicrobial susceptibility of S. aureus to 16 antibiotics representing 11 different categories showed that 74% of the strains were resistant to at least 1 antibiotic. Moreover, 28% of the strains showed multidrug resistance; in particular, two methicillin-resistant S. aureus strains (MRSA) exhibited significant antibiotic resistance. In summary, our results show that dairy products are contaminated by S. aureus strains carrying genes encoding a variety of enterotoxins as well genes conferring resistance to antibiotics. Both MRSA strains and MSSA isolates showing multidrug resistance were present in foods of animal origin.

Comparison of Transcriptional Signatures of Three Staphylococcal Superantigenic Toxins in Human Melanocytes

Staphylococcus aureus, a gram-positive bacterium, causes toxic shock through the production of superantigenic toxins (sAgs) known as Staphylococcal enterotoxins (SE), serotypes A-J (SEA, SEB, etc.), and toxic shock syndrome toxin-1 (TSST-1). The chronology of host transcriptomic events that characterizes the response to the pathogenesis of superantigenic toxicity remains uncertain. The focus of this study was to elucidate time-resolved host responses to three toxins of the superantigenic family, namely SEA, SEB, and TSST-1. Due to the evolving critical role of melanocytes in the host’s immune response against environmental harmful elements, we investigated herein the transcriptomic responses of melanocytes after treatment with 200 ng/mL of SEA, SEB, or TSST-1 for 0.5, 2, 6, 12, 24, or 48 h. Functional analysis indicated that each of these three toxins induced a specific transcriptional pattern. In particular, the time-resolved transcriptional modulations due to SEB exposure were very distinct from those induced by SEA and TSST-1. The three superantigens share some similarities in the mechanisms underlying apoptosis, innate immunity, and other biological processes. Superantigen-specific signatures were determined for the functional dynamics related to necrosis, cytokine production, and acute-phase response. These differentially regulated networks can be targeted for therapeutic intervention and marked as the distinguishing factors for the three sAgs.

Enterotoxin- and Antibiotic-Resistance-Encoding Genes Are Present in Both Coagulase-Positive and Coagulase-Negative Foodborne Staphylococcus Strains

Food poisoning by staphylococcal enterotoxins (SE) is a major cause of foodborne illness, often associated with coagulase-positive staphylococci (CPS). The increase in the number of methicillin-resistant Staphylococcus aureus (MRSA) strains is another major problem associated with CPS. However, reports of the association of SE and methicillin-resistant Staphylococcus with coagulase-negative staphylococci (CNS) are beginning to re-emerge. In this context, the aim of this study is to investigate the presence of staphylococcal enterotoxin genes and to characterize the phenotypic and genotypic antimicrobial resistance in 66 isolates of Staphylococcus spp. (47 CNS and 19 CPS) recovered from ready-to-eat (RTE) street food sold in Maputo, Mozambique. Seven virulence genes encoding SE (sea, seb, sec, sed and see) and two toxins (hlb and sak) were screened by multiplex PCR (MPCR). Antimicrobial resistance against 12 antibiotics was evaluated by the disk diffusion method. The presence of genes encoding resistance to penicillin, methicillin, vancomycin and erythromycin (blaZ, mecA, vancA, vancB, ermA, ermB and ermC) were also screened by PCR. At least one of the seven virulence genes assessed in this study was detected in 57.9% and 51% of CPS and CNS isolates, respectively. In CPS isolates, the most frequent gene was hlb (47.4%), followed by sec (15.8%) and sea, seb and sed genes with 5.3% each. In CNS isolates, the most frequent gene was sec (36.2%) followed by sak (17%), hlb (14.9%), sed (12.8%) and seb (6.4%). Five of the twelve CPS in which virulence genes were detected were also antibiotic-resistant. All the CNS isolates harboring virulence genes (n = 27, 57.4%) were antimicrobial-resistant. The prevalence of multidrug resistance was higher (59.6%) in CNS than in CPS (26.3%) isolates. Regarding the presence of antibiotic-resistance genes, blaZ (penicillin-resistant) was the most frequent in both CPS (42.1%) and CNS (87.2%), followed by the mecA (encoding methicillin resistance) and vancA genes (vancomycin-resistant), which represented 36.8% and 31.6% in CPS isolates and 46.8% in CNS isolates, respectively. The prevalence of vancomycin-resistant staphylococci has been increasing worldwide and, to our knowledge, this is the first study to report the occurrence of vancomycin-resistant staphylococci in Mozambique. These results emphasize the need to investigate CNS isolates in parallel with CPS, as both constitute public health hazards, given their potential to produce SE and spread antimicrobial resistance genes.

Whole-genome sequence analysis of Staphylococcus aureus from retail fish acknowledged the incidence of highly virulent ST672-MRSA-IVa/t1309, an emerging Indian clone, in Assam, India

The epidemiology and toxigenicity of MRSA in the fishery environment are poorly understood. In this study, methicillin-resistant Staphylococcus aureus (MRSA) (n = 1) and methicillin-susceptible S. aureus (MSSA) (n = 2) from retail fish were subjected to comprehensive genome analysis. Here, we report the occurrence of ST672-MRSA-IV/t1309 and ST5-MSSA/t105 for the first time from India in the fishery environment. The resistome of the isolates was in concordance with their phenotypic resistance pattern. Phenotypically, the resistance profile of MSSA isolates (n = 2) was AMP-CLI-ERY-NOR-PEN. For MRSA (n = 1), it was AMP-CFZ-CLI-ERY-NOR-OXA-PEN. The antibiotic efflux genes and mutations in the antibiotic target accounted for fluoroquinolone resistance whereas methicillin resistance was conferred through possession of a mecA gene. Similarly, all three isolates carried a similar array of virulence factors. The conjugative plasmid inc18 and rep family 10 plasmids were found in two of the three isolates. This study documents the MRSA carrying SCCmec IVa elements which are the markers of community-associated MRSA (CA-MRSA). Through the possession of SCCmec IV elements, which are smaller than other types of SCCmec, MRSA can contribute to the rapid dissemination of antimicrobial resistance and virulence factors. In short, our findings highlighted that the presence of ST672-MRSA in fishery environments may pose a risk to human health.

Periodontal connection with intestinal inflammation: Microbiological and immunological mechanisms

Humans have coevolved with the trillions of resident microbes that populate every nook and cranny of the body. At each site, the resident microbiota creates a unique ecosystem specialized to its environment, benefiting the development and maintenance of human physiology through harmonious symbiotic relationships with the host. However, when the resident microbiota is perturbed, significant complications may arise with disastrous consequences that affect the local and distant ecosystems. In this context, periodontal disease results in inflammation beyond the oral cavity, such as in the gastrointestinal tract. Accumulating evidence indicates that potentially harmful oral resident bacteria (referred to as pathobionts) and pathogenic immune cells in the oral mucosa can migrate to the lower gastrointestinal tract and contribute to intestinal inflammation. We will review the most recent advances concerning the periodontal connection with intestinal inflammation from microbiological and immunological perspectives. Potential therapeutic approaches that target the connection between the mouth and the gut to treat gastrointestinal diseases, such as inflammatory bowel disease, will be examined. Deciphering the complex interplay between microbes and immunity along the mouth-gut axis will provide a better understanding of the pathogenesis of both oral and gut pathologies and present therapeutic opportunities.

Genotypes and phenotypes of methicillin-resistant staphylococci isolated from shrimp aquaculture farms

The population of methicillin-resistant (MR) staphylococci in aquatic environment is rarely investigated. Here, we characterized a collection of MR staphylococci recovered from shrimp aquaculture farms (n = 37) in Kerala, India. A total of 261 samples yielded 47 MR isolates (16 S. aureus, 13 S. haemolyticus, 11 S. epidermidis, 3 S. saprophytics and 2 each of S.intermedius and S. kloosii). Multi-drug resistance was evident in 72.3% of the isolates, with resistance mainly towards erythromycin (78.7%), norfloxacin and trimethoprim-sulfamethoxazole (53.2%), and gentamicin (34%). Major resistance genes identified included mecA (100%), ermC (38.3%), aacA-aphD (21.3%), tetK (14.9%) and tetM (21.3%). Almost 60% of the isolates carried type V SCCmec (Staphylococcal Cassette Chromosome mec), and the remaining harboured untypeable SCCmec elements. Comprehensive genotyping of the methicillin-resistant Staphylococcus aureus isolates revealed high prevalence of ST772-t345-V (sequence type-spa type-SCCmec type) (75%), followed by minor representations of ST6657-t345-V and ST3190-t12353. The isolates of S. haemolyticus and S. epidermidis were genotypically diverse as shown by their pulsed-field gel electrophoresis (PFGE) profiles. Genes encoding staphylococcal enterotoxins were observed in 53.2% of the isolates. Various genes involved in adhesion and biofilm formation were also identified. In conclusion, our findings provide evidence that shrimp aquaculture settings can act as reservoirs of methicillin-resistant staphylococci.

Detection of Resistant and Enterotoxigenic Strains of Staphylococcus warneri Isolated from Food of Animal Origin

The topic of this work is the detection of antimicrobial resistance to Staphylococcus warneri strains and the genes encoding staphylococcal enterotoxins. It is considered a potential pathogen that can cause various—mostly inflammatory—diseases in immunosuppressed patients. The experimental part of the paper deals with the isolation of individual isolates from meat samples of Oryctolagus cuniculus, Oncorhynchus mykiss, Scomber scombrus, chicken thigh, beef thigh muscle, pork thigh muscle, and bryndza cheese. In total, 45 isolates were obtained and subjected to phenotypic (plasma coagulase activity, nuclease, pigment, hemolysis, lecithinase, and lipase production) and genotypic analyses to confirm the presence of the S. warneri species. The presence of genes encoding staphylococcal enterotoxins A (three isolates) and D (six isolates) was determined by PCR. Using the Miditech system, the minimum inhibitory concentration for various antibiotics or antibiotics combinations was determined, namely for ampicillin; ampicillin + sulbactam; oxacillin; cefoxitin; piperacillin + tazobactam; erythromycin; clindamycin; linezolid; rifampicin; gentamicin; teicoplanin; vancomycin; trimethoprim; chloramphenicol; tigecycline; moxifloxacin; ciprofloxacin; tetracycline; trimethoprim + sulfonamide; and nitrofurantoin. Resistance to ciprofloxacin and tetracycline was most common (73%). At the same time, out of a total of 45 isolates, 22% of the isolates were confirmed as multi-resistant. Isolates that showed phenotypic resistance to β-lactam antibiotics were subjected to mecA gene detection by PCR.

The Complex Role of Lactic Acid Bacteria in Food Detoxification

Toxic ingredients in food can lead to serious food-related diseases. Such compounds are bacterial toxins (Shiga-toxin, listeriolysin, Botulinum toxin), mycotoxins (aflatoxin, ochratoxin, zearalenone, fumonisin), pesticides of different classes (organochlorine, organophosphate, synthetic pyrethroids), heavy metals, and natural antinutrients such as phytates, oxalates, and cyanide-generating glycosides. The generally regarded safe (GRAS) status and long history of lactic acid bacteria (LAB) as essential ingredients of fermented foods and probiotics make them a major biological tool against a great variety of food-related toxins. This state-of-the-art review aims to summarize and discuss the data revealing the involvement of LAB in the detoxification of foods from hazardous agents of microbial and chemical nature. It is focused on the specific properties that allow LAB to counteract toxins and destroy them, as well as on the mechanisms of microbial antagonism toward toxigenic producers. Toxins of microbial origin are either adsorbed or degraded, toxic chemicals are hydrolyzed and then used as a carbon source, while heavy metals are bound and accumulated. Based on these comprehensive data, the prospects for developing new combinations of probiotic starters for food detoxification are considered.

S. aureus and IgE-mediated diseases: pilot or copilot? A narrative review

INTRODUCTION

S. aureus is a major opportunistic pathogen that has been implicated in the pathogenesis of several chronic inflammatory diseases including bronchial asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), chronic spontaneous urticaria (CSU), and atopic dermatitis. S. aureus can induce the production of both polyclonal and specific IgE that can elicit an inflammatory cascade.

AREAS COVERED

The link between the sensitization to S. aureus enterotoxins and the severity of several chronic inflammatory diseases is reviewed in detail, as well as its therapeutic implications.

EXPERT OPINION

An anti-IgE strategy to inhibit S. aureus enterotoxins would be a valid approach to treat several endotypes of severe asthma, CRSwNP and CSU in which IgE against S. aureus enterotoxins should represent, not only a marker of severity of the diseases but also a target of a treatment.

Multiple Domains of Staphylococcal Superantigen-like Protein 11 (SSL11) Contribute to Neutrophil Inhibition

Staphylococcus aureus is an opportunistic pathogen producing many immune evasion molecules targeting various components of the host immune defense, including the Staphylococcal superantigen-like protein (SSL 1-14) family. Despite sharing similar structures with the powerful superantigens (SAgs), which cause massive T cell activation, SSLs interfere with a wide range of innate immune defenses. SSLs are divided into two subgroups, SSLs that contain a conserved carbohydrate Sialyl Lewis X [Neu5Acα2-3Galβ1-4(Fucα1-3) GlcNAcβ, SLeX] binding site and SSLs that lack the SLeX binding site. SSL2-6 and SSL11 possess the SLeX binding site. Our previous studies showed that SSL11 arrests cell motility by inducing cell adhesion in differentiated HL60 (dHL60) cells, while SSL7 did not bind dHL60 cells. SSL7-based chimeras were engineered by exchanging the SSL7 sequence with the corresponding SSL11 sequence and assaying for a gain of SSL11 function, namely, the induction of cell spreading and motility arrest. In addition to the SLeX-binding site, we observed that three beta-strands β6, β7, and β9 and the N-terminal residues, Y16 and Y17, transitioned SSL7 to gain SSL11 activities. These studies define the structure-function properties of SSL11 that may allow SSL11 to inhibit S. aureus clearance by the host innate immune system, allowing S. aureus to maintain a carrier state in humans, an understudied aspect of S. aureus pathogenesis.

Identification of nuc nuclease and sea enterotoxin genes in Staphylococcus aureus isolates from nasal mucosa of burn hospital staff: a cross-sectional study

Background

Staphylococcus aureus is one of the main causes of nosocomial infections. The hospital staff as carriers of Staphylococcus aureus have an important role in spreading it among patients. This study aimed to isolate and identify the sea and nuc genes that encode enterotoxin in Staphylococcus aureus isolates, isolated from the Nasal mucosa of staff in Sari Burn hospital by PCR method.

Methods

A gene nasal mucosa of Sari Burn hospital staff. In this cross-sectional study, a nasal swab of 40 staff of Burn hospital of Sari was collected and isolated. The S. aureus was detected by biochemical tests such as Gram stain, catalase, and coagulase. Then nuc and sea genes were identified after the extraction of DNA, by PCR technique and gel electrophoresis with a specific primer.

Results

From the 40 strains obtained from nasal carriers, 20 S. aureus strains were isolated, and all of them included the nuc gene, while 6 samples included the sea gene. Given that every 20 samples had the nuc gene, therefore this gene is a strong marker for S. aureus. Also, the presence of sea genes in some samples suggested the presence of enterotoxin A in hospital staff as a healthy carrier.

Conclusions

PCR techniques can be used to detect the genes encoding enterotoxins in S. aureus. Given that hospital staff can be carriers of Staphylococcus aureus and spread nosocomial infections, therefore identification of the carriers to prevent the spread of infection is essential.

Molecular Typing, Antibiotic Resistance and Enterotoxin Gene Profiles of Staphylococcus aureus Isolated from Humans in South Korea

The emergence of antimicrobial-resistant Staphylococcus aureus has become a grave concern worldwide. In this study, 95 strains of S. aureus isolated from stool samples were collected from Busan, South Korea to characterize their antimicrobial susceptibility, enterotoxin genes, and molecular typing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and random amplification of polymorphic DNA (RAPD) assay. Only two strains showed no drug resistance, whereas resistance to three or more antibiotics was observed in 87.4% of strains. Ampicillin resistance was the most common at 90% and all strains were susceptible to vancomycin. The distribution of enterotoxin genes encoded in isolates was sea (32.6%), sec (11.6%), seg (19%), sea & sec (2.1%), and sec & seg (34.7%). Molecular typing using both MALDI-TOF MS and RAPD indicated that S. aureus exhibited diverse clonal lineages and no correlations were observed among the profiling of enterotoxin, MALDI-TOF MS, and RAPD. This investigation provides useful information on foodborne pathogenic S. aureus that has a significant public health impact in South Korea.

Comparative Genomic Analysis of Statistically Significant Genomic Islands of Helicobacter pylori strains for better understanding the disease prognosis

Bacterial virulence factors are often located in their genomic islands (GIs). Helicobacter pylori, a highly diverse organism is reported to be associated with several gastrointestinal diseases like, gastritis, gastric cancer, peptic ulcer, duodenal ulcer etc. A novel similarity score-based comparative analysis with GIs of fifty H. pylori strains revealed clear idea of the various factors which promote disease progression. Two putative pathogenic GIs in some of the H. pylori strains were identified. One GI, having a putative labile enterotoxin and other dynamin-like proteins (DLPs), is predicted to increase the release of toxin by membrane vesicular formation. Another island contains a virulence-associated protein D (vapD) which is a component of a type-II toxin-antitoxin system (TAs), leads to enhance the severity of the H. pylori infection. Besides the well-known virulence factors like CagA, and VacA, several GIs have been identified which showed to have direct or indirect impact on H. pylori clinical outcomes. One such GI, containing lipopolysaccharide (LPS) biosynthesis genes was revealed to be directly connected with disease development by inhibiting the immune response. Another collagenase-containing GI worsens ulcers by slowing down the healing process. GI consisted of fliD operon was found to be connected to flagellar assembly and biofilm production. By residing in biofilms, bacteria can avoid antibiotic therapy, resulting in chronic infection. Along with well-studied CagA and VacA virulent genes, it is equally important to study these identified virulence factors for better understanding H. pylori induced disease prognosis.

Hazard of Staphylococcal Enterotoxins in Food and Promising Strategies for Natural Products against Virulence

Staphylococcal enterotoxins (SEs) secreted by Staphylococcus aureus frequently contaminate food and cause serious foodborne diseases but are ignored during food processing and even cold-chain storage. Notably, SEs are stable and resistant to harsh sterilization environments, which can induce more serious hazards to public health than the bacterium itself. Therefore, it is necessary to develop promising strategies to control SE contamination in food and improve food safety. Natural products not only have various pharmaceutical properties, such as antimicrobial and antitoxin activities, but they are also eco-friendly, safe, nutritive, and barely drug-resistant. Here, the hazards of SEs and the promising natural compounds with different inhibitory mechanisms are summarized and classified. The key points of future research and applications for natural products against bacterial toxin contamination in food are also prospected. Overall, this review may provide enlightening insights for screening effective natural compounds to prevent foodborne diseases caused by bacterial toxins.

Risk of Bacteriophage Therapeutics to Transfer Genetic Material and Contain Contaminants Beyond Endotoxins with Clinically Relevant Mitigation Strategies

Bacteriophage therapy is a promising adjuvant therapeutic in the treatment of multidrug-resistant infections and chronic biofilm infections. However, there is limited knowledge about how to best utilize these agents in vivo, leading to a wide range of treatment protocols. Moreover, while bacteriophages are similar to antibiotics in their antimicrobial effects, these are active viruses and are very different from conventional antibiotics. One main difference that clinicians should be cognizant about is the potential ability of these therapeutics to horizontally transfer genetic material, and the clinical ramifications of such events. In addition, while bacteriophage therapeutics are readily tested for sterility and endotoxins, clinicians should also be aware of other contaminants, such as exotoxins, pathogenicity islands and prophages, that can contaminate bacteriophage therapeutics, and their clinical ramifications. While the perception may be that these are only theoretical issues, regulatory agencies are starting to recommend their evaluation when using bacteriophage therapy and subsequently these topics are discussed herein, as are ways to test for and mitigate the adverse effects of these issues.

Control of Foodborne Staphylococcus aureus by Shikonin, a Natural Extract

Foodborne Staphylococcus aureus (S. aureus) has attracted widespread attention due to its foodborne infection and food poisoning in human. Shikonin exhibits antibacterial activity against a variety of microorganisms, but there are few studies on its antibacterial activity against S. aureus. This study aims to explore the antibacterial activity and mechanism of shikonin against foodborne S. aureus. The results show that the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of shikonin were equal for all tested strains ranging from 35 μg/mL to 70 μg/mL. Shikonin inhibited the growth of S. aureus by reducing intracellular ATP concentrations, hyperpolarizing cell membrane, destroying the integrity of cell membrane, and changing cell morphology. At the non-inhibitory concentrations (NICs), shikonin significantly inhibited biofilm formation of S. aureus, which was attributed to inhibiting the expression of cidA and sarA genes. Moreover, shikonin also markedly inhibited the transcription and expression of virulence genes (sea and hla) in S. aureus. In addition, shikonin has exhibited antibacterial ability against both planktonic and biofilm forms of S. aureus. Importantly, in vivo results show that shikonin has excellent biocompatibility. Moreover, both the heat stability of shikonin and the antimicrobial activity of shikonin against S. aureus were excellent in food. Our findings suggest that shikonin are promising for use as a natural food additive, and it also has great potential in effectively controlling the contamination of S. aureus in food and reducing the number of illnesses associated with S. aureus.

Endocannabinoid Anandamide Attenuates Acute Respiratory Distress Syndrome through Modulation of Microbiome in the Gut-Lung Axis

Acute respiratory distress syndrome (ARDS) is a serious lung condition characterized by severe hypoxemia leading to limitations of oxygen needed for lung function. In this study, we investigated the effect of anandamide (AEA), an endogenous cannabinoid, on Staphylococcal enterotoxin B (SEB)-mediated ARDS in female mice. Single-cell RNA sequencing data showed that the lung epithelial cells from AEA-treated mice showed increased levels of antimicrobial peptides (AMPs) and tight junction proteins. MiSeq sequencing data on 16S RNA and LEfSe analysis demonstrated that SEB caused significant alterations in the microbiota, with increases in pathogenic bacteria in both the lungs and the gut, while treatment with AEA reversed this effect and induced beneficial bacteria. AEA treatment suppressed inflammation both in the lungs as well as gut-associated mesenteric lymph nodes (MLNs). AEA triggered several bacterial species that produced increased levels of short-chain fatty acids (SCFAs), including butyrate. Furthermore, administration of butyrate alone could attenuate SEB-mediated ARDS. Taken together, our data indicate that AEA treatment attenuates SEB-mediated ARDS by suppressing inflammation and preventing dysbiosis, both in the lungs and the gut, through the induction of AMPs, tight junction proteins, and SCFAs that stabilize the gut-lung microbial axis driving immune homeostasis.

Virulence and enterotoxin gene profile of methicillin-resistant Staphylococcus aureus isolates from bovine mastitis

Bovine mastitis is a major infectious disease affecting dairy animals resulting in enormous economic losses, prolonged antibiotic treatment, reduced milk yield and death of livestock. Emergence of Methicillin-resistant Staphylococcus aureus (MRSA) among bovine mastitis is matter of concern for animal health and dairy industry. The present study was conducted to detect the distribution of virulence and enterotoxin genes among MRSA isolates from bovine mastitis. Out of 500 milk samples, 126 isolates were identified as Staphylococcus and from these only 56 were S. aureus. S.aureus were resistant to cefoxitin (75%), ceftazidime (75%), amoxicillin (71.4%), cefodaxime (67.8%), cefepime (66.1%), oxacillin (64.3%), norfloxacin (60.7%) and gentamicin (58.9%). Only 42 isolates were identified as MRSA strains among staphylococci isolates. MRSA were harbouring virulence genes; mecA (100%), coa (100%) and nuc (100%). The other virulence factors such as hlg (80.9%, 34/42), pvl (47.6%, 20/42) and spa (92.8%, 39/42) were also reported. Molecular characterisation of enterotoxin genes revealed that out of 42 tested isolates 11 were found negative (26%) for any enterotoxin gene whereas 7 (16.6%), 6 (14.3%), 18 (42.8%), 1 (2.3%), 26 (61.9%),27(64.2%),3 (7.1%) were found positive for sea, seb, sec, sed, seg, sei, and seq enterotoxin respectively.

Molecular Epidemiology, Virulence Factors, Antibiotic Resistance and Risk Factors for Nasal Carriage of Staphylococcus aureus in A Teenage Student Population: High Prevalence of Oxacillin Susceptible MRSA Isolates

Background: Asymptomatic carriage of Staphylococcus aureus can lead to endogenous infections and cross-transmission to other individuals. Objectives: The prevalence, molecular epidemiology, antibiotic resistance, and risk factors for nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) were studied in school children in Ardabil, Iran. Methods: Totally, 510 nasal samples were collected during 2017. Isolates were identified and subjected to antimicrobial susceptibility testing, identification of oxacillin resistance, and molecular typing. Results: Totally, 13.5% of volunteers were positive for methicillin-susceptible Staphylococcus aureus (MSSA) and 17.5% colonized with mecA positive S. aureus strains, including 6.07% oxacillin-resistant MRSA (OR-MRSA) and 11.56% oxacillin-susceptible MRSA (OS-MRSA). Excluding β-lactam antibiotics, high resistance rate was observed for erythromycin (71%), tetracycline (25.8%), clindamycin (35%) in our isolates. Surprisingly, 11% of the isolates [OR-MRSA (25.8%), OS-MRSA (10.1%), and MSSA (5.7%) isolates] were resistant to mupirocin. Moreover, 18 (58%), 29 (49%), and 29 (42%) of OR-MRSA, OS-MRSA, and MSSA isolates were multidrug-resistant (MDR), respectively. Overall, 97.48% of isolates carried ≥ 3 toxin encoding genes. The pvl gene was found in 46 (29%) isolates. In comparison, 25.50% of MRSA (9.60% OR-MRSA and 34% OS-MRSA) and 33% of MSSA isolates carried pvl gene. SCCmec type IV had the highest rate among OR-MRSA (87%) and OS-MRSA (74.5%) isolates, which indicates CA-MRSA phenotype. Eleven and 21 spa types were identified in OR-MRSA, and OS-MRSA isolates, respectively. The most common spa types were t11332 (14.3%) and t012 (11.4%) in OS-MRSA isolates. ERIC-PCR revealed high genetic diversity among isolates. The number of students in classroom and incomplete antibiotic course were associated with OS-MRSA nasal carriage. Conclusions: This study showed a high proportion of MDR CA-MRSA nasal carriage among Iranian healthy school children community.

Evaluation of virulence potential of methicillin-sensitive and methicillin-resistant Staphylococcus aureus isolates from a German refugee cohort

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) seem to be highly transmissible, often infect otherwise healthy humans and frequently occur in hospital outbreaks.

METHODS

Refugees, living in accommodations in Germany were screened for nasal carriage of S. aureus. The isolates were investigated regarding resistance and virulence, phenotypically and by whole genome data analysis.

RESULTS

5.6% (9/161) of the refugees are carriers of S. aureus. 2.5% (4/161) are MRSA carriers. Among the refugees, spa-types t021, t084, t304, t991 and t4983 were detected, as well as the new spa-types t18794 and t18795. t304 and t991 are assumed to be local spa-types from the middle east. The isolates are less resistant and marginal biofilm formers. Each isolate has a remarkable set of virulence genes, although genes, encoding for proteins strongly associated with invasive S. aureus infections, like Panton-Valentine leucocidin, were not detected.

CONCLUSION

The detection of strains from the middle east, supports the assumption that strains co-travel with the refugees and persist despite a transition of the host's living conditions. Whole genome data analysis does not permit to finally evaluate a germ's virulence. Nevertheless, an impression of the virulence potential of the strains, regarding skills in colonization, resistance, immune evasion, and host cell damaging can be pictured.

Machine Learning for Prediction of Drug Targets in Microbe Associated Cardiovascular Diseases by Incorporating Host-pathogen Interaction Network Parameters

Host-pathogen interactions play a crucial role in invasion, infection, and induction of immune response in humans. In this work, four machine learning algorithms, namely Logistic regression, K-nearest neighbor, Support Vector Machine, and Random Forest were implemented for the classification of drug targets. The algorithms were trained using 3400 hosts and 3800 pathogen drug and non-drug target proteins as learning instances. For each protein, 68 pathogen and 73 host features were computed that included sequence, structure, biological and host-pathogen network centrality characteristics. The Random Forest classifier model achieved the best accuracy after 10-fold cross-validation. 99 % accuracy was achieved with a ROC-AUC score of 0.99±0.01 for both pathogen and host training sets. The Eigenvector Centrality of host-pathogen interactions and host-host interactions was the top feature in performing classification of pathogen and host targets respectively. Other features important for classification were the presence of catalytic and binding sites, low instability/aliphatic index, and cellular location. The Random Forest classifier was then used for prediction of drug targets involved in Microbe Associated Cardiovascular Diseases. 331 host and 743 pathogen proteins were predicted as drug targets by the random forest model and can be validated experimentally for therapeutic intervention in Microbe Associated Cardiovascular Diseases.

Gram-Negative Bacterial Lipopolysaccharide Promotes Tumor Cell Proliferation in Breast Implant-Associated Anaplastic Large-Cell Lymphoma

Breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL) is a distinct malignancy associated with textured breast implants. We investigated whether bacteria could trigger the activation and multiplication of BIA-ALCL cells in vitro. BIA-ALCL patient-derived BIA-ALCL tumor cells, BIA-ALCL cell lines, cutaneous ALCL cell lines, an immortal T-cell line (MT-4), and peripheral blood mononuclear cells (PBMC) from BIA-ALCL, capsular contracture, and primary augmentation patients were studied. Cells were subjected to various mitogenic stimulation assays including plant phytohemagglutinin (PHA), Gram-negative bacterial lipopolysaccharide (LPS), Staphylococcal superantigens enterotoxin A (SEA), toxic shock syndrome toxin-1 (TSST-1), or sterilized implant shells. Patient-derived BIA-ALCL tumor cells and BIA-ALCL cell lines showed a unique response to LPS stimulation. This response was dampened significantly in the presence of a Toll-like receptor 4 (TLR4) inhibitor peptide. In contrast, cutaneous ALCL cells, MT-4, and PBMC cells from all patients responded significantly more to PHA, SEA, and TSST-1 than to LPS. Breast implant shells of all surface grades alone did not produce a proliferative response of BIA-ALCL cells, indicating the breast implant does not act as a pro-inflammatory stimulant. These findings indicate a possible novel pathway for LPS to promote BIA-ALCL cell proliferation via a TLR4 receptor-mediated bacterial transformation of T-cells into malignancy.

Immunoinformatics analysis and evaluation of recombinant chimeric triple antigen toxoid (r-HAB) against Staphylococcus aureus toxaemia in mouse model

Abstract

Staphylococcus aureus is a serious pathogen unleashing its virulence through several classes of exotoxins such as hemolysins and enterotoxins. In this study, we designed a novel multi-antigen subunit vaccine which can induce innate, humoral and cellular immune responses. Alpha hemolysin, enterotoxins A and B were selected as protective antigens for combining into a triple antigen chimeric protein (HAB). Immunoinformatics analysis predicted HAB protein as a suitable vaccine candidate for inducing both humoral and cellular immune responses. Tertiary structure of the HAB protein was predicted and validated through computational approaches. Docking studies were performed between the HAB protein and mice TLR2 receptor. Furthermore, we constructed and generated recombinant HAB (r-HAB) protein in E. coli and studied its toxicity, immunogenicity and protective efficacy in a mouse model. Triple antigen chimeric protein (r-HAB) was found to be highly immunogenic in mouse as the anti-r-HAB hyperimmune serum was strongly reactive to all three native exotoxins on Western blot. In vitro toxin neutralization assay using anti-r-HAB antibodies demonstrated > 75% neutralization of toxins on RAW 264.7 cell line. Active immunization with r-HAB toxoid gave ~ 83% protection against 2 × lethal dosage of secreted exotoxins. The protection was mediated by induction of strong antibody responses that neutralized the toxins. Passive immunization with anti-r-HAB antibodies gave ~ 50% protection from lethal challenge. In conclusion, in vitro and in vivo testing of r-HAB found the molecule to be nontoxic, highly immunogenic and induced excellent protection towards native toxins in actively immunized and partial protection to passively immunized mice groups.

Key points

• HAB protein was computationally designed to induce humoral and cellular responses.

• r-HAB protein was found to be nontoxic, immunogenic and protective in mouse model.

• r-HAB conferred protection against lethal challenge in active and passive immunization.

Eleutheroside K Isolated from Acanthopanax henryi (Oliv.) Harms Inhibits the Expression of Virulence-Related Exoproteins in Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus (S.) aureus (MRSA) is a representative pathogen that produces numerous virulence factors involving manifold cytotoxins and exotoxins. The present study was designed to investigate the influence of Eleutheroside K (ETSK), a single compound isolated from the leaves of Acanthopanax (A.) henryi (Oliv.) Harms, on the exotoxins secreted by MRSA. The transcription and translation of the exotoxins (α-hemolysin and staphylococcal enterotoxins) related to virulence in S. aureus were determined via quantitative RT-PCR and western blot analysis. The effect of ETSK on the production of tumor necrosis factor (TNF)-α was evaluated using enzyme-linked immunosorbent assay. As a result, ETSK at sub-MIC concentrations could reduce the protein expression of α-hemolysin and enterotoxin, and the expression of genes that regulate virulence factors was also inhibited. In addition, the TNF-inducing activity of S. aureus was attenuated by ETSK in a dose-dependent manner. These results revealed that ETSK not only reduced the protein and gene expression levels of related exotoxins but also suppressed the ability of S. aureus to induce macrophages to release cytokines. This study indicated that the inhibition of MRSA infection by ETSK may be achieved by reducing the virulence of S. aureus and highlighted the potential of ETSK as an innovative strategy for the prevention and treatment of MRSA infections.

Staphylococcus aureus Toxins: An Update on Their Pathogenic Properties and Potential Treatments

Staphylococcus aureus is a clinically important pathogen that causes a wide range of human infections, from minor skin infections to severe tissue infection and sepsis. S. aureus has a high level of antibiotic resistance and is a common cause of infections in hospitals and the community. The rising prevalence of community-acquired methicillin-resistant S. aureus (CA-MRSA), combined with the important severity of S. aureus infections in general, has resulted in the frequent use of anti-staphylococcal antibiotics, leading to increasing resistance rates. Antibiotic-resistant S. aureus continues to be a major health concern, necessitating the development of novel therapeutic strategies. S. aureus uses a wide range of virulence factors, such as toxins, to develop an infection in the host. Recently, anti-virulence treatments that directly or indirectly neutralize S. aureus toxins have showed promise. In this review, we provide an update on toxin pathogenic characteristics, as well as anti-toxin therapeutical strategies.

Characterization of antibiotic resistance and virulence genes of ocular methicillin-resistant Staphylococcus aureus strains through complete genome analysis

Virulence-factor encoding genes (VFGs) and antimicrobial resistance genes (ARGs) of ocular Methicillin-Resistant Staphylococcus aureus (MRSA), are the reason behind the common cause of severe and untreatable ocular infection and are largely unknown. The unavailability of the complete genome sequence of ocular MRSA strains hinders the unambiguous determination of ARGs and VRGs role in disease pathogenesis and their genomic location. To fulfill this critical need, we achieved the high-quality complete genome of four ocular MRSA strains (AMRF3 - AMRF6) by combining MinION nanopore sequencing technology, followed by polishing with Illumina sequence reads. We obtained a single chromosome and a plasmid in each strain. Sequence typing revealed that AMRF3 and AMRF5 strains harbored ST772, whereas AMRF4 and AMRF6 harbored ST 2066. All plasmids carried heavy metal cadmium resistance genes cadC and cadD, while cadA was detected only in the plasmid pSaa6159 of AMRF4 and AMRF6 strains. Further, pSaa6159 contains a complete Tn552 transposon with beta-lactamase genes, blaI, blaR1, and blaZ. Interestingly, pSaa6159 in AMRF6 carried five copies of Tn552 transposon. Several exotoxins and enterotoxins were identified across ocular MRSA strains and ST2066 strains found to be not carried any enterotoxins; this finding suggests that these two strains are exotoxigenic. Besides, ST2066 strains carried serine proteases (splA, splB, splD, splE and spIF) and exotoxin (seb and set 21) for their virulence, while ST772 carried antimicrobial resistance genes (blaZ, dfrG, msrA, mphC and fosB) and enterotoxin sec for virulence, suggesting sequence type-specific resistance and virulence. Also, we identified many VFGs and ARGs, that provided multi-drug resistance, enterotoxigenic, exotoxigenic, biofilm-forming, host tissue adhesion and immune response evasion in ocular MRSA strains. Thus, our study provides a better insight into the genomes of ocular MRSA strains that would provide more effective treatment strategies for ocular MRSA infection.

Bacterial proteomics and its application for pathogenesis studies

Bacteria build their structures by implementing several macromolecules such as proteins, polysaccharides, phospholipids, and nucleic acids, which leads to preserve their lives and play an essential role in their pathogenesis. There are two genomic and proteomic methods to study various macromolecules of bacteria, which are complementary methods and provide comprehensive information. Proteomic approaches are used to identify proteins and their cell applications. Furthermore, to study bacterial proteins, macromolecules are involved in the bacteria's structures and functions. These protein-based methods provide comprehensive information about the cells, such as the external structures, internal compositions, post-translational modifications, and mechanisms of particular actions such as biofilm formation, antibiotic resistance, and adaptation to the environment, which are helpful in promoting bacterial pathogenesis. These methods use various devices such as MALDI-TOF MS, LC-MS, and two-dimensional electrophoresis, which are valuable tools for studying different structural and functional proteins of the bacteria and their mechanisms of pathogenesis that causes rapid, easy, and accurate diagnosis of the infections.

Virulence and intermediate resistance to high-end antibiotic (teicoplanin) among coagulase-negative staphylococci sourced from retail market fish

This study reports the distribution of enterotoxigenic determinants among staphylococci and the susceptibility of staphylococci to various classes of antibiotics. We observed all the isolates as resistant to beta-lactam antibiotics and a few as resistant to non-beta-lactam antibiotics such as clindamycin (47.4%), erythromycin (44.7%), gentamicin (23.7%), norfloxacin (34.2%), tetracycline (26.3%), trimethoprim-sulfamethoxazole (15.8%) etc. The resistance of S. sciuri (n = 1) and S. haemolyticus (n = 1) to rifampicin and intermediate resistance of S. gallinarum (n = 2) to teicoplanin, a high-end antibiotic, are also observed in this study. The multidrug-resistance (≥ 3 classes of antibiotics) was recorded in 23 (60.5%) isolates. The virulomes such as sea, seb, seg and sei were identified predominantly in S. haemolyticus. Surprisingly, certain isolates which were phenotypically confirmed as biofilm-producers by Congo red agar (CRA) test did not harbor biofilm-associated loci. This implies the protein-mediated mechanism of biofilm formation as an alternative to polysaccharide intercellular adhesin (PIA) in staphylococci. However, icaAD locus which encodes PIA was identified in 10 (26.3%) isolates and the eno locus, encoding elastin-binding protein which can accelerate the biofilm production, is identified in all the isolates. The possession of type V SCCmec elements by the S. haemolyticus (15.8%) raised the concern about the rapid dissemination of mecA gene to other species of staphylococci including the virulent S. aureus. In short, this study acknowledges the toxigenicity of coagulase-negative staphylococci (CoNS). Through this study, surveillance of antimicrobial resistance and transference of virulomes in staphylococci is warranted.

Effect of (-)-Epigallocatechin Gallate on Activation of JAK/STAT Signaling Pathway by Staphylococcal Enterotoxin A

Staphylococcal enterotoxin A (SEA), which is a superantigen toxin protein, binds to cytokine receptor gp130. Gp130 activates intracellular signaling pathways, including the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway. The effects of SEA on the JAK/STAT signaling pathway in mouse spleen cells were examined. After treatment with SEA, mRNA expression levels of interferon gamma (IFN-γ) and suppressor of cytokine-signaling 1 (SOCS1) increased. SEA-induced IFN-γ and SOCS1 expression were decreased by treatment with (-)-epigallocatechin gallate (EGCG). The phosphorylated STAT3, Tyr705, increased significantly in a SEA concentration-dependent manner in mouse spleen cells. Although (-)-3″-Me-EGCG did not inhibit SEA-induced phosphorylated STAT3, EGCG and (-)-4″-Me-EGCG significantly inhibited SEA-induced phosphorylated STAT3. It was thought that the hydroxyl group at position 3 of the galloyl group in the EGCG was responsible for binding to SEA and suppressing SEA-induced phosphorylation of STAT3. Through protein thermal shift assay in vitro, the binding of the gp130 receptor to SEA and the phosphorylation of STAT3 were inhibited by the interaction between EGCG and SEA. As far as we know, this is the first report to document that EGCG inhibits the binding of the gp130 receptor to SEA and the associated phosphorylation of STAT3.

The Role of Atopy in COPD and Asthma

Common to several allergic diseases is the generation of immunoglobulin E (IgE) by plasma cells, when exposed to an innocuous antigen. Asthma and chronic obstructive pulmonary disease (COPD) are two prevalent chronic airway inflammatory diseases. Asthma is mediated in some patients through eosinophilic inflammatory mechanisms that include allergic sensitization and Th2-mediated immune airway response. COPD, on the other hand is mainly considered a Th1-mediated inflammatory process with neutrophilic predominance or a non-Th2 inflammation, occasionally associated with the presence of airway bacteria or viruses. IgE production appears to play an important role in the development of both COPD and asthma, as it has been associated to respiratory symptoms, lung function, bacterial and viral infections, airway remodeling and bronchial hyperreactivity in both diseases. The aim of this review is to summarize all current data concerning the role of specific and total IgE in COPD and asthma and to highlight similarities and differences in view of possible therapeutic interventions.

Development and validation of the Standard method EN ISO 19020 - microbiology of the food chain - Horizontal method for the immunoenzymatic detection of staphylococcal enterotoxins in foodstuffs

In the frame of the CEN Mandate M/381 from the European Commission to CEN (European Committee for Standardization), a method for the detection of staphylococcal enterotoxins in foodstuffs has been developed, validated and standardized. An extraction procedure based on dialysis concentration followed by an immuno-enzymatic detection has been defined. In addition, performance criteria (minimum values of sensitivity, specificity and level of detection) to be achieved by the commercially available immuno-enzymatic kits that could be used to detect staphylococcal enterotoxins in food matrices, were developed. A 2-stage validation study was conducted: The first stage aimed at selecting the commercial kits to be included in the second stage, which consisted in an interlaboratory study, using eight matrices covering five food categories (ready-to-eat food, meat products, milk products, dessert and fish). Results showed that two detection kits included in the study met the pre-defined performance criteria. The implementation of dialysis concentration step increased significantly the sensitivity of the method. The method developed allowed to achieve the Benchmark Dose lower limit (BMD₁₀) estimated at 6.1 ng. In 2019, finally, the European Commission recognized this standard as the European Union reference method for the detection of staphylococcal enterotoxins in food.

Genomic epidemiology of methicillin-resistant and -susceptible Staphylococcus aureus from bloodstream infections

Background

Bloodstream infections due to Staphylococcus aureus cause significant patient morbidity and mortality worldwide. Of major concern is the emergence and spread of methicillin-resistant S. aureus (MRSA) in bloodstream infections, which are associated with therapeutic failure and increased mortality.

Methods

We generated high quality draft genomes from 323 S. aureus blood culture isolates from patients diagnosed with bloodstream infection at the Dartmouth-Hitchcock Medical Center, New Hampshire, USA in 2010–2018.

Results

In silico detection of antimicrobial resistance genes revealed that 133/323 isolates (41.18%) carry horizontally acquired genes conferring resistance to at least three antimicrobial classes, with resistance determinants for aminoglycosides, beta-lactams and macrolides being the most prevalent. The most common resistance genes were blaZ and mecA, which were found in 262/323 (81.11%) and 104/323 (32.20%) isolates, respectively. Majority of the MRSA (102/105 isolates or 97.14%) identified using in vitro screening were related to two clonal complexes (CC) 5 and 8. The two CCs emerged in the New Hampshire population at separate times. We estimated that the time to the most recent common ancestor of CC5 was 1973 (95% highest posterior density (HPD) intervals: 1966–1979) and 1946 for CC8 (95% HPD intervals: 1924–1959). The effective population size of CC8 increased until the late 1960s when it started to level off until late 2000s. The levelling off of CC8 in 1968 coincided with the acquisition of SCCmec Type IV in majority of the strains. The plateau in CC8 also coincided with the acceleration in the population growth of CC5 carrying SCCmec Type II in the early 1970s, which eventually leveled off in the early 1990s. Lastly, we found evidence for frequent recombination in the two clones during their recent clonal expansion, which has likely contributed to their success in the population.

Conclusions

We conclude that the S. aureus population was shaped mainly by the clonal expansion, recombination and co-dominance of two major MRSA clones in the last five decades in New Hampshire, USA. These results have important implications on the development of effective and robust strategies for intervention, control and treatment of life-threatening bloodstream infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06293-3.

High frequency of enterotoxin encoding genes of Staphylococcus aureus isolated from food and clinical samples

BACKGROUND

Staphylococcus aureus is recognized as an important cause of food poisoning related to the consumption of raw, undercooked, or mishandled foods worldwide.

METHODS

A total of 90 individual meat samples and 200 clinical specimens were collected and investigated the frequency of S. aureus and classical enterotoxin genes. The samples were cultured on Baird-Parker and Mannitol salt agar and subjected for confirmatory biochemical tests and molecular detection of femA, sea, seb, sec, sed, and see genes.

RESULTS

A total of 31 (34.5%) meat samples and 81 (40.5%) clinical specimens were positive for the presence of S. aureus. These isolates were detected with slightly higher frequency in clinical specimens than food samples (P> 0.05). Furthermore, the frequency of S. aureus in raw meat (23.4%) was higher than that in cooked meat samples (11.1%) (P< 0.05). Staphylococcal enterotoxin (SE) genes were identified in 18 (58.1%) of 31 meat isolates and 42 (51.8%) of 81 clinical isolates. The frequency of SE genes (except see) in meat isolates was slightly higher than that in clinical isolates (P> 0.05). We found sea and see genes with higher frequency than others in both meat and clinical samples. Furthermore, 55.5% of meat isolates and 38.1% of clinical isolates possessed more than one se gene.

CONCLUSION

Detection of enterotoxigenic S. aureus in clinical and raw meat samples shows a probable risk for public health. Therefore, intensive and continuous monitoring of potentially pathogenic S. aureus is strongly recommended in order to evaluate the human health risk arising from food consumption.

Comparison of Antivirulence Activities of Black Ginseng against Methicillin-Resistant Staphylococcus aureus According to the Number of Repeated Steaming and Drying Cycles

Korean ginseng has been widely used in Eastern medicine for thousands of years. The contents of the compounds in ginseng roots change depending on the amount of steaming and drying, and the drying method used. Black ginseng (BG) is the Korean ginseng processed by repeated steaming and drying. In this study, 5-year-old fresh Korean ginseng roots were steamed and dried 3 or 5 times, and we investigated how many cycles of steaming and drying are preferable for antivirulence activities against methicillin-resistant Staphylococcus aureus (MRSA). As a result, the antivirulence activities was increased by the treatment of BG that was steamed and dried three times, and the effect was further increased by five-time processed BG. Moreover, an ELISA showed that the TNF-α production of RAW264.7 cells stimulated by MRSA supernatants was inhibited by subinhibitory concentrations of BG extract. The expression of Hla, staphylococcal enterotoxin A (SEA), and staphylococcal enterotoxin B (SEB), an important virulence factor in the pathogenicity of MRSA, was found to decrease when bacterial cells were treated with BG extract. The antivirulence activities of BG were not simply due to pathogen growth inhibition; the BG extract was shown to decrease agrA, hla, sea, and seb expression in MRSA. Therefore, BG strongly reduces the secretion of the virulence factors produced by Staphylococcus aureus, suggesting that a BG-based structure may be used for the development of drugs aimed at staphylococcal virulence-related exoproteins. This study suggests that BG could be used as a promising natural compound in the food and pharmaceutical industry.