Staphylococcal enterocolitis: forgotten but not gone?

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.

Purification, characterization, and cloning of a novel pro-inflammatory secreted protein from Staphylococcus aureus

IMPORTANCE

Staphylococcus aureus causes a myriad of human diseases, ranging from relatively mild soft tissue infections to highly fatal pneumonia, sepsis, and toxic shock syndrome. The organisms primarily cause diseases across mucosal and skin barriers. In order to facilitate penetration of barriers, S. aureus causes harmful inflammation by inducing chemokines from epithelial cells. We report the cloning and characterization of a novel secreted S. aureus protein that induces chemokine production from epithelial cells as its major demonstrable function. This secreted protein possibly helps S. aureus and its secreted proteins to penetrate host barriers.

Inhibition of Toxic Shock Syndrome-Associated Staphylococcus aureus by Probiotic Lactobacilli

Staphylococcus aureus is a human pathogen with many infections originating on mucosal surfaces. One common group of S. aureus is the USA200 (CC30) clonal group, which produces toxic shock syndrome toxin-1 (TSST-1). Many USA200 infections occur on mucosal surfaces, particularly in the vagina and gastrointestinal tract. This allows these organisms to cause cases of menstrual TSS and enterocolitis. The current study examined the ability of two lactobacilli, Lactobacillus acidophilus strain LA-14 and Lacticaseibacillus rhamnosus strain HN001, for their ability to inhibit the growth of TSST-1 positive S. aureus, the production of TSST-1, and the ability of TSST-1 to induce pro-inflammatory chemokines from human vaginal epithelial cells (HVECs). In competition growth experiments, L. rhamnosus did not affect the growth of TSS S. aureus but did inhibit the production of TSST-1; this effect was partially due to acidification of the growth medium. L. acidophilus was both bactericidal and prevented the production of TSST-1 by S. aureus. This effect appeared to be partially due to acidification of the growth medium, production of H2O2, and production of other antibacterial molecules. When both organisms were incubated with S. aureus, the effect of L. acidophilus LA-14 dominated. In in vitro experiments with HVECs, neither lactobacillus induced significant production of the chemokine interleukin-8, whereas TSST-1 did induce production of the chemokine. When the lactobacilli were incubated with HVECs in the presence of TSST-1, the lactobacilli reduced chemokine production. These data suggest that these two bacteria in probiotics could reduce the incidence of menstrual and enterocolitis-associated TSS. IMPORTANCE Toxic shock syndrome (TSS) Staphylococcus aureus commonly colonize mucosal surfaces, giving them the ability to cause TSS through the action of TSS toxin-1 (TSST-1). This study examined the ability of two probiotic lactobacilli to inhibit S. aureus growth and TSST-1 production, and the reduction of pro-inflammatory chemokine production by TSST-1. Lacticaseibacillus rhamnosus strain HN001 inhibited TSST-1 production due to acid production but did not affect S. aureus growth. Lactobacillus acidophilus strain LA-14 was bactericidal against S. aureus, partially due to acid and H2O2 production, and consequently also inhibited TSST-1 production. Neither lactobacillus induced the production of pro-inflammatory chemokines by human vaginal epithelial cells, and both inhibited chemokine production by TSST-1. These data suggest that the two probiotics could reduce the incidence of mucosa-associated TSS, including menstrual TSS and cases originating as enterocolitis.

Methicillin-Resistant Staphylococcus aureus-Associated Diarrhea in a Critically Ill Burn Patient

Described in surgical patients after antibiotic use in the 1950s and 1960s, Staphylococcus aureus (S. aureus) enterocolitis is a rare form of nosocomial diarrhea. However, S. aureus is not routinely tested like Clostridium difficile (C. difficile). We report a case of methicillin-resistant S. aureus (MRSA) enterocolitis found on stool culture in a 22-week pregnant female with a previously negative nasal MRSA culture, and a total burn surface area greater than 60%. She also developed necrotizing MRSA pneumonia and bacteremia. After starting broad-spectrum antibiotic for the necrotizing pneumonia with subsequent acute respiratory distress syndrome, the patient exhibited large voluminous diarrhea that tested positive for MRSA and negative for C. difficile in the stool culture. Similar to other reports of high-volume diarrhea, the diarrhea resolved quickly with enteral vancomycin. S. aureus should be considered along with C. difficile during the workup of nosocomial diarrhea, especially with exposure to broad-spectrum antibiotics in the critically ill patient.

Fatal infection with enterocolitis from methicillin-resistant Staphylococcus aureus and the continued value of culture in the era of molecular diagnostics

MRSA enterocolitis is under-recognized in the setting of PCR testing. In this case report, we describe risk factors, the importance of stool culture, and the third published case of MRSA enterocolitis in a patient with leukemia. In addition, we performed a retrospective analysis of all stool cultures at our institution that have grown Staphylococcus aureus, and we describe an additional five cases. We also report the diagnostic yield of organisms detected by culture, but not on the FilmArray panel. While rare, these cases demonstrate that MRSA in stool may indicate a severe and potentially life-threatening infection, particularly in immunocompromised persons.

A Case of Postoperative Methicillin-Resistant Staphylococcus aureus Enterocolitis in an 81-Year-Old Man and Review of the Literature

Patient: Male, 81-year-old

Final Diagnosis: Methicillin-resistant Staphylococcus aureus bacteremia • Methicillin-resistant Staphylococcus aureus enterocolitis

Symptoms: Diarrhea • sepsis

Medication: —

Clinical Procedure: Computed tomography • echocardiography • polymerase chain reaction • whipple procedure

Specialty: Gastroenterology and Hepatology • Infectious Diseases • Surgery

Glycerol Monolaurate Contributes to the Antimicrobial and Anti-inflammatory Activity of Human Milk

Human milk has antimicrobial compounds and immunomodulatory activities. We investigated glycerol monolaurate (GML) in human milk versus bovine milk and infant formula for antimicrobial and anti-inflammatory activities. Human milk contained approximately 3000 µg/ml of GML, compared to 150 μg/ml in bovine milk and none in infant formula. For bacteria tested (Staphylococcus aureus, Bacillus subtilis, Clostridium perfringens, Escherichia coli), except Enterococcus faecalis, human milk was more antimicrobial than bovine milk and formula. The Enterococcus faecalis strain, which was not inhibited, produced reutericyclin, which is an analogue of GML and functions as a growth stimulant in bacteria that produce it. Removal of GML and other lipophilic molecules from human milk by ethanol extraction resulted in a loss of antibacterial activity, which was restored by re-addition of GML. GML addition caused bovine milk to become antimicrobial. Human milk but not bovine milk or formula inhibited superantigen and bacterial-induced IL-8 production by model human epithelial cells. GML may contribute beneficially to human milk compared to bovine milk or infant formula.

Biocompatible Nanocomposite Tailored to Endure the Gastric Niche Renders Effective in Vitro Elimination of Intestinal Pathogenic Bacteria and Supports Adhesion by Beneficial Bacteria

Bacteriocins produced by lactic acid bacteria (LAB) are potent therapeutic arsenals for targeting gastrointestinal pathogens and a promising alternative to antibiotics, because of their selective activity and reduced propensity to trigger collateral damage to the beneficial gut microbes. However, proteolytic inactivation in the gastric niche renders bacteriocins ineffective. The present study addresses this challenge and demonstrates that a biocompatible milk protein fraction can be leveraged to generate a robust nanocargo, which renders protection from proteolysis in the gastric milieu and facilitates delivery of the encapsulated bacteriocin pediocin. In a simulated gastric transit experiment, pediocin-loaded milk protein nanocomposite (Ped-MNC) could render a 3.0 log reduction in the viability of model gastrointestinal pathogens. Ped-MNC is nontoxic to cultured human intestinal cells (HT-29 cells) and effectively abrogates pathogenic bacteria adhering onto intestinal cells. In a combinatorial regimen, Ped-MNC and the beneficial LAB Lactobacillus plantarum DF9 could substantially reduce the levels of the pathogen Enterococcus faecalis MTCC 439 adhering onto HT-29 cells and interestingly the nanocomposite does not hinder adhesion of intestinal cells by the beneficial LAB. The developed nanocomposite holds promise as a niche specific therapeutic for selective mitigation of intestinal pathogens.

Methicillin-Resistant Staphylococcus aureus as a Probable Cause of Antibiotic-Associated Enterocolitis

Antibiotic-associated diarrhea is typically associated with Clostridium difficile. However, Staphylococcus aureus has also been described as a cause of antibiotic-associated enterocolitis and diarrhea and is likely an underrecognized etiology. We present a case of enterocolitis and urinary tract infection caused by methicillin-resistant S. aureus following antibiotic treatment.

Dual-label flow cytometry-based host cell adhesion assay to ascertain the prospect of probiotic Lactobacillus plantarum in niche-specific antibacterial therapy

Host cell adhesion assays that provide quantitative insight on the potential of lactic acid bacteria (LAB) to inhibit adhesion of intestinal pathogens can be leveraged for the development of niche-specific anti-adhesion therapy. Herein, we report a dual-colour flow cytometry (FCM) analysis to assess the ability of probiotic Lactobacillus plantarum strains to impede adhesion of Enterococcus faecalis, Listeria monocytogenes and Staphylococcus aureus onto HT-29 cells. FCM in conjunction with a hierarchical cluster analysis could discern the anti-adhesion potential of L. plantarum strains, wherein the efficacy of L. plantarum DF9 was on a par with the probiotic L. rhamnosus GG. Combination of FCM with principal component analysis illustrated the relative influence of LAB strains on adhesion parameters kd and em of the pathogen and identified probiotic LAB suitable for anti-adhesion intervention. The analytical merit of the FCM analysis was captured in host cell adhesion assays that measured relative elimination of adhered LAB vis-à-vis pathogens, on exposure to either LAB bacteriocins or therapeutic antibiotics. It is envisaged that the dual-colour FCM-based adhesion assay described herein would enable a fundamental understanding of the host cell adhesion process and stimulate interest in probiotic LAB as safe anti-adhesion therapeutic agents against gastrointestinal pathogens.

A systematic review for pursuing the presence of antibiotic associated enterocolitis caused by methicillin resistant Staphylococcus aureus

BACKGROUND

Although it has received a degree of notoriety as a cause for antibiotic-associated enterocolitis (AAE), the role of methicillin resistant Staphylococcus aureus (MRSA) in the pathogenesis of this disease remains enigmatic despite a multitude of efforts, and previous studies have failed to conclude whether MRSA can cause AAE. Numerous cases of AAE caused by MRSA have been reported from Japan; however, due to the fact that these reports were written in the Japanese language and a good portion lacked scientific rigor, many of these reports went unnoticed.

METHODS

We conducted a systematic review of pertinent literatures to verify the existence of AAE caused by MRSA. We modified and applied methods in common use today and used a total of 9 criteria to prove the existence of AAE caused by Klebsiella oxytoca. MEDLINE/Pubmed, Excerpta Medica Database (EMBASE), the Cochrane Database of Systematic Reviews, and the Japan Medical Abstract Society database were searched for studies published prior to March 2013.

RESULTS

A total of 1,999 articles were retrieved for evaluation. Forty-five case reports/series and 9 basic studies were reviewed in detail. We successfully identified articles reporting AAE with pathological and microscopic findings supporting MRSA as the etiological agent. We also found comparative studies involving the use of healthy subjects, and studies detecting probable toxins. In addition, we found animal models in which enteritis was induced by introducing MRSA from patients. Although we were unable to identify a single study that encompasses all of the defined criteria, we were able to fulfill all 9 elements of the criteria by collectively analyzing multiple studies.

CONCLUSIONS

AAE caused by MRSA-although likely to be rarer than previous Japanese literatures have suggested-most likely does exist.

Effects of the continuous intake of a milk drink containing Lactobacillus casei strain Shirota on abdominal symptoms, fecal microbiota, and metabolites in gastrectomized subjects

OBJECTIVE

This article is based on our previously reported results of irregular bowel movement and disturbances of the intestinal microbiota/environment in gastrectomized patients. A placebo-controlled, double-blind comparative study was carried out to evaluate the effects of a fermented milk beverage containing Lactobacillus casei strain Shirota (LcS) in such patients. The major evaluated factors of this article were "bowel movement" and "quality of life." The secondary evaluated factors were "fecal microbiota" and "enteric environment."

METHODS

Of the 190 gastrectomized subjects who participated in our previously reported defecation survey, 134 subjects judged as having abnormal defecation gave consent to participate in this study. These subjects continuously ingested the test beverage containing 40 billion LcS or placebo (one bottle per day, 4 weeks).

RESULTS

In the LcS-ingested group, among the 118 subjects who completed the tests, the assessments of the subjects were based on their division into groups based on their symptoms with our scoring system for constipation/diarrhea; although there was no significant ingestion effect in total, in the constipation group, LcS reduced the degree of constipation compared with that in the placebo group. In the diarrhea group, LcS ingestion improved diarrhea compared with that in the preingestion state. Fecal Staphylococcus level was decreased.

CONCLUSIONS

The results suggest the possibility that the continuous consumption of LcS-fermented milk relieves irregular bowel movement in gastrectomized patients.

Staphylococcal and streptococcal superantigen exotoxins

SUMMARY This review begins with a discussion of the large family of Staphylococcus aureus and beta-hemolytic streptococcal pyrogenic toxin T lymphocyte superantigens from structural and immunobiological perspectives. With this as background, the review then discusses the major known and possible human disease associations with superantigens, including associations with toxic shock syndromes, atopic dermatitis, pneumonia, infective endocarditis, and autoimmune sequelae to streptococcal illnesses. Finally, the review addresses current and possible novel strategies to prevent superantigen production and passive and active immunization strategies.

Methicillin-resistant staphylococci: implications for our food supply?

Food-borne intoxication, caused by heat-stable enterotoxins produced by Staphylococcus aureus, causes over 240,000 cases of food-borne illness in the United States annually. Other staphylococci commonly associated with animals may also produce these enterotoxins. Foods may be contaminated by infected food handlers during slaughter and processing of livestock or by cross-contamination during food preparation. S. aureus also causes a variety of mild to severe skin and soft tissue infections in humans and other animals. Antibiotic resistance is common in staphylococci. Hospital-associated (HA) S. aureus are resistant to numerous antibiotics, with methicillin-resistant S. aureus (MRSA) presenting significant challenges in health care facilities for over 40 years. During the mid-1990s new human MRSA strains developed outside of hospitals and were termed community-associated (CA). A few years later, MRSA was isolated from horses and methicillin resistance was detected in Staphylococcus intermedius/pseudintermedius from dogs and cats. In 2003, a livestock-associated (LA) MRSA strain was first detected in swine. These methicillin-resistant staphylococci pose additional food safety and occupational health concerns. MRSA has been detected in a small percentage of retail meat and raw milk samples indicating a potential risk for food-borne transmission of MRSA. Persons working with animals or handling meat products may be at increased risk for antibiotic-resistant infections. This review discusses the scope of the problem of methicillin-resistant staphylococci and some strategies for control of these bacteria and prevention of illness.

Enterotoxin-producing staphylococci cause intestinal inflammation by a combination of direct epithelial cytopathy and superantigen-mediated T-cell activation

BACKGROUND

Enterotoxin-producing Staphylococcus aureus may cause severe inflammatory intestinal disease, particularly in infants or immunodeficient or elderly patients. They are also recognized to be associated with sudden infant death syndrome. Little is known, however, about mucosal responses to staphylococci.

METHODS

The mucosal lesion in three infants with staphylococcal enterocolitis was assessed by immunohistochemistry and electron microscopy. The organisms underwent extensive molecular analysis. Their toxins were assessed for capacity to induce T-cell activation and host mucosal responses examined by in vitro organ culture. Epithelial responses were studied by coculture with HEp-2 and Caco-2 cells.

RESULTS

Intestinal biopsies from the patients showed marked epithelial damage with mucosal inflammation. The three staphylococci, representing two distinct clones, were methicillin-sensitive, producing SEG/I enterotoxins and Rho-inactivating EDIN toxins. Their enterotoxins potently activated T cells, but only whole organisms could induce in vitro enteropathy, characterized by remarkable epithelial desquamation uninhibited by tacrolimus. EDIN-producing staphylococci, but not their supernatants, induced striking cytopathy in HEp-2 epithelial cells but not in Caco-2 cells. Although HEp-2 and Caco-2 cells produced similar IL-8, CCL20, and cathelicidin LL37 responses upon bacterial exposure, only Caco-2 cells expressed mRNA for the β-defensins HBD2 and HBD3, while HEp-2 cells were unable to do so.

CONCLUSIONS

Staphylococci induce enterocolitis by a combination of direct enterocyte cytopathy mediated by EDIN toxins, disrupting the epithelial barrier, and enterotoxin superantigen-induced mucosal T-cell activation. Gut epithelial production of β-defensins may contribute to host defense against invasive staphylococcal disease.

17 degrees Celsius body temperature--resuscitation successful?

The resuscitation of patients with accidental profound hypothermia is challenging. A 17-year-old man got lost on the first of January, after a New Year's Eve party in the foothills of the Alps. After a search of four hours, he was found unconscious with fixed pupils, a Glasgow Coma Scale of three points, and a body temperature below 20° Celsius. There were no signs for traumatic injuries. Initial electrocardiogram (ECG) showed no heart activity. Basic life support was begun by the mountain rescue service and continued by the medical helicopter team. The patient was transferred under continuous cardiac massage, airway management with intubation and intravenous line via external jugular vein by helicopter to the nearest hospital for analysis of serum potassium. Body temperature was 17°C measured by urinary bladder electronic thermometer. The serum potassium was 7.55 mmol/L, therefore the patient was transferred by helicopter to the next cardiovascular center for rewarming with extracorporal circulation (ECC). Under the rewarming process with ECC, the heart activity restarted at 25°C with external defibrillation. The patient was rewarmed to 37.2°C after four hours of ECC. Cerebral CT scans after 24 h and 48 h revealed no significant hypoxia and after extubation the early rehabilitation process started. After six weeks, the patient regained the ability to walk and started to communicate on a basic level. After 54 days the patient presented signs of septic shock. After initial stabilization and CT diagnostic, a laparotomy was performed. The intraoperative finding was a total necrosis of the small bowel and colon. The patient died on the same day. Post mortem examination showed a necrotizing enterocolitis with transmural necrosis of the bowel. Survivors of uncontrolled profound hypothermia below 20°C core temperature are rare. The epicrisis is often prolonged by complications of different causes. The present case reports a necrotizing enterocolitis with a non-occlusive mesenteric ischemia (NOMI) as a medium-term complication of profound hypothermia.

Staphylococcal enterotoxins

Staphylococcus aureus (S. aureus) is a Gram positive bacterium that is carried by about one third of the general population and is responsible for common and serious diseases. These diseases include food poisoning and toxic shock syndrome, which are caused by exotoxins produced by S. aureus. Of the more than 20 Staphylococcal enterotoxins, SEA and SEB are the best characterized and are also regarded as superantigens because of their ability to bind to class II MHC molecules on antigen presenting cells and stimulate large populations of T cells that share variable regions on the β chain of the T cell receptor. The result of this massive T cell activation is a cytokine bolus leading to an acute toxic shock. These proteins are highly resistant to denaturation, which allows them to remain intact in contaminated food and trigger disease outbreaks. A recognized problem is the emergence of multi-drug resistant strains of S. aureus and these are a concern in the clinical setting as they are a common cause of antibiotic-associated diarrhea in hospitalized patients. In this review, we provide an overview of the current understanding of these proteins.