Humanized Mice Exhibit Exacerbated Abscess Formation and Osteolysis During the Establishment of Implant-Associated Staphylococcus aureus Osteomyelitis.

Staphylococcus aureus is the predominant pathogen causing osteomyelitis. Unfortunately, no immunotherapy exists to treat these very challenging and costly infections despite decades of research, and numerous vaccine failures in clinical trials. This lack of success can partially be attributed to an overreliance on murine models where the immune correlates of protection often diverge from that of humans. Moreover, S. aureus secretes numerous immunotoxins with unique tropism to human leukocytes, which compromises the targeting of immune cells in murine models. To study the response of human immune cells during chronic S. aureus bone infections, we engrafted non-obese diabetic (NOD)-scid IL2Rγnull (NSG) mice with human hematopoietic stem cells (huNSG) and analyzed protection in an established model of implant-associated osteomyelitis. The results showed that huNSG mice have increases in weight loss, osteolysis, bacterial dissemination to internal organs, and numbers of Staphylococcal abscess communities (SACs), during the establishment of implant-associated MRSA osteomyelitis compared to NSG controls (p < 0.05). Flow cytometry and immunohistochemistry demonstrated greater human T cell numbers in infected versus uninfected huNSG mice (p < 0.05), and that T-bet+ human T cells clustered around the SACs, suggesting S. aureus-mediated activation and proliferation of human T cells in the infected bone. Collectively, these proof-of-concept studies underscore the utility of huNSG mice for studying an aggressive form of S. aureus osteomyelitis, which is more akin to that seen in humans. We have also established an experimental system to investigate the contribution of specific human T cells in controlling S. aureus infection and dissemination.

Lytic lesion of skull: a rare presentation of chronic granulomatous disease.

An 18-month-old boy presented with lytic lesion of skull and recurrent abscesses with Serratia marcescens The extensive work up revealed a gene mutation confirming the diagnosis of chronic granulomatous disease (CGD). This case scenario underscores the importance of exploring the possibility of immunodeficiency if there is a history of recurrent abscesses with atypical organism. The case also demonstrates that CGD can present as lytic lesion of skull.

Three-Dimensional In Vitro Staphylococcus aureus Abscess Communities Display Antibiotic Tolerance and Protection from Neutrophil Clearance.

Staphylococcus aureus is a prominent human pathogen in bone and soft-tissue infections. Pathophysiology involves abscess formation, which consists of central staphylococcal abscess communities (SACs), surrounded by a fibrin pseudocapsule and infiltrating immune cells. Protection against the ingress of immune cells such as neutrophils, or tolerance to antibiotics, remains largely unknown for SACs and is limited by the lack of availability of in vitro models. We describe a three-dimensional in vitro model of SACs grown in a human plasma-supplemented collagen gel. The in vitro SACs reached their maximum size by 24 h and elaborated a fibrin pseudocapsule, as confirmed by electron and immunofluorescence microscopy. The in vitro SACs tolerated 100× the MIC of gentamicin alone and in combination with rifampin, while planktonic controls and mechanically dispersed SACs were efficiently killed. To simulate a host response, SACs were exposed to differentiated PLB-985 neutrophil-like (dPLB) cells and to primary human neutrophils at an early stage of SAC formation or after maturation at 24 h. Both cell types were unable to clear mature in vitro SACs, but dPLB cells prevented SAC growth upon early exposure before pseudocapsule maturation. Neutrophil exposure after plasmin pretreatment of the SACs resulted in a significant decrease in the number of bacteria within the SACs. The in vitro SAC model mimics key in vivo features, offers a new tool to study host-pathogen interactions and drug efficacy assessment, and has revealed the functionality of the S. aureus pseudocapsule in protecting the bacteria from host phagocytic responses and antibiotics.

A 27-year-old man with recurrent sinopulmonary and cutaneous infections.

The increasing availability of genetic testing for modern immunologists in the evaluation of immune diseases could provide a definite diagnosis in elusive cases. A 27-year-old white male patient presented to the clinic with recurrent sinopulmonary and cutaneous infections since childhood. The patient's mother had seronegative polyarthritis, and one of two sisters of the patient had chronic sinopulmonary infections. Serum immunoglobulins, immunoglobulin G (IgG) subclasses, lymphocyte subset markers, mannose-binding lectin, mitogen and antigen stimulation, bacteriophage study, and Streptococcus pneumoniae titers to 23 serotypes were all normal. B-cell phenotyping revealed a decrease in both nonswitched memory B cells (CD19+CD27+IgD+) and switched memory B-cells (CD19+CD27+IgD-). Genetic testing and the improvement of clinical symptoms after IgG replacement led to the final diagnosis.

Subarticular Inflammatory Pseudoabscesses: A Pathologic Study With Clinical Correlation.

Abnormal accumulation of neutrophils in a subarticular bone usually raises the concern for osteomyelitis or septic arthritis, a disabling and potentially life-threatening medical condition. At the pathology department of a specialized orthopedic institute, we observed a distinct pattern of subarticular inflammation mimicking infection characterized by collections of neutrophils, macrophages, and fibrin in pseudocystic spaces of variable size and extent in the superficial subarticular bone not accompanied by granulation tissue or necrosis. We coined the term "inflammatory pseudoabscess" to describe these accumulations. From 1997-2015, we reported inflammatory pseudoabscesses in 157 primary arthroplasty/osteotomy specimens from 143 patients without penetrating trauma or hardware in the affected joint. The predominant gross and histologic features were those of destructive/inflammatory joint disease, including lymphoplasmacytic synovitis (95.3%), subchondral osseous chronic inflammation (80.3%), exudative synovitis (58.0%), synovial pannus (52.0%), and marginal erosions of articular cartilage and/or subarticular bone (43.3%). Clinical information was available in 137 (95.8%) patients, 107 (overall: 74.8%) of whom had preoperatively or postoperatively diagnosed inflammatory arthropathy, most commonly rheumatoid arthritis. The remaining 30 (overall: 21.0%) patients had no documented inflammatory disorders, but some had bilateral or multijoint arthropathy, hands/feet involvement, lymphoplasmacytic synovitis, ulcerative colitis, or family history of inflammatory arthropathy. There was no documented infection-associated implant failure. We believe that inflammatory pseudoabscess represents an intraosseous manifestation of noninfectious inflammatory disorders of joints. This feature should be recognized by pathologists and used to suggest further clinical evaluation for undiagnosed inflammatory joint diseases.

Uncommon Association Between Diabetic Ketoacidosis, Thyrotoxicosis, Cutaneous Abscess and Acute Pericarditis in an Immunocompetent Patient: A Single Case Report and Literature Review.

INTRODUCTION: The typical factors precipitating diabetic ketoacidosis (DKA) include infections (30%), cessation of antidiabetic medication (20%), and a new diagnosis of diabetes (25%). The etiology remains unknown in 25% of cases. Less frequent causes cited in the literature include severe thyrotoxicosis and, infrequently, pericarditis. Few publications have described the role of human T lymphotropic virus type 1 (HTLV-1) in endocrine and metabolic disorders. Based on a clinical case associated with several endocrine and metabolic disorders, we suggest a potential role for HTLV-1, an endemic virus in the Amazonian area, and review the literature concerning the role of this virus in thyroiditis, pericarditis and diabetes mellitus. CASE REPORT: A fifty-year-old Surinamese woman without any medical history was admitted for diabetic ketoacidosis. No specific anti-pancreatic autoimmunity was observed, and the C-peptide level was low, indicating atypical type-1 diabetes mellitus. DKA was associated with thyrotoxicosis in the context of thyroiditis and complicated by nonbacterial pericarditis and a Staphylococcus aureus subcutaneous abscess. The patient was infected with HTLV-1. CONCLUSION: To our knowledge, this uncommon association is described for the first time. Few studies have analyzed the implications of HTLV-1 infection in thyroiditis and diabetes mellitus. We did not find any reports describing the association of pericarditis with HTLV-1 infection. Additional studies are necessary to understand the role of HTLV-1 in endocrine and cardiac disorders.

Mechanisms of Immune Evasion and Bone Tissue Colonization That Make Staphylococcus aureus the Primary Pathogen in Osteomyelitis.

PURPOSE OF REVIEW: Staphylococcus aureus is the primary pathogen responsible for osteomyelitis, which remains a major healthcare burden. To understand its dominance, here we review the unique pathogenic mechanisms utilized by S. aureus that enable it to cause incurable osteomyelitis. RECENT FINDINGS: Using an arsenal of toxins and virulence proteins, S. aureus kills and usurps immune cells during infection, to produce non-neutralizing pathogenic antibodies that thwart adaptive immunity. S. aureus also has specific mechanisms for distinct biofilm formation on implants, necrotic bone tissue, bone marrow, and within the osteocyte lacuno-canicular networks (OLCN) of live bone. In vitro studies have also demonstrated potential for intracellular colonization of osteocytes, osteoblasts, and osteoclasts. S. aureus has evolved a multitude of virulence mechanisms to achieve life-long infection of the bone, most notably colonization of OLCN. Targeting S. aureus proteins involved in these pathways could provide new targets for antibiotics and immunotherapies.

The good side of inflammation: Staphylococcus aureus proteins SpA and Sbi contribute to proper abscess formation and wound healing during skin and soft tissue infections.

Staphylococcus aureus is the most prominent cause of skin and soft tissue infections (SSTI) worldwide. Mortality associated with invasive SSTI is a major threat to public health considering the incidence of antibiotic resistant isolates in particular methicillin resistant S. aureus both in the hospital (HA-MRSA) and in the community (CA-MRSA). To overcome the increasing difficulties in the clinical management of SSTI due to MRSA, new prophylactic and therapeutic approaches are urgently needed and a preventive vaccine would be welcome. The rational design of an anti-S. aureus vaccine requires a deep knowledge of the role that the different bacterial virulence factors play according to the type of infection. In the present study, using a set of isogenic deficient mutants and their complemented strains we determined that the staphylococcal surface proteins SpA and Sbi play an important role in the induction of inflammatory cytokines and chemokines in the skin during SSTI. SpA and Sbi initiate signaling cascades that lead to the early recruitment of neutrophils, modulate their lifespan in the skin milieu and contribute to proper abscess formation and bacterial eradication. Moreover, the expression of SpA and Sbi appear critical for skin repair and wound healing. Thus, these results indicate that SpA and Sbi can promote immune responses in the skin that are beneficial for the host and therefore, should not be neutralized with vaccine formulations designed to prevent SSTI.

Disseminated cutaneous chrysosporium infection.

Cutaneous chrysosporium infection is extremely rare and underdiagnosed. We present an immunocompromised patient who presented with recurrent cutaneous abscesses. Histopathology of the abscess showed thick-walled conidia and septate fungal hyphae within the subcutis and fungal culture grew Chrysosporium species.

Hyperimmunoglobulinemia D syndrome with recurrent perianal abscess successfully treated with canakinumab.

Hyperimmunoglobulinaemia D syndrome is an autoinflammatory disease usually representing recurrent episodes of fever, arthralgia/arthritis, cervical lymphadenopathy, vomiting, diarrhoea, abdominal pain and skin rashes lasting 3-7 days every 4-8 weeks since their infancy. Recent reports suggested a link between perianal fistulae/abscess and severe colitis with hyperimmunoglobulinaemia D syndrome resembling an inflammatory bowel disease phenotype. Herein, we report an 18-month-old patient with recurrent attacks of fever and pharyngitis lasting 2-3 days every 10-15 days since the first two weeks of life. Inflammatory attacks were accompanied by diarrhoea, oral aphthous ulcers, cervical lymphadenopathy, maculopapular rash, severe leukocytosis and perianal fistulae/abscess. After the initiation of canakinumab, the patient was clinically improved with complete healing of perianal fistulas/abscesses. In conclusion, hyperimmunoglobulinaemia D syndrome should be considered in differential diagnosis of inflammatory bowel disease and recurrent perianal abscess/fistula in a patient with inflammatory attacks.

Chronic Neutropenia in Children With Abscess Forming Cervical Lymphadenitis Caused by Staphylococcus aureus.

BACKGROUND: Suppurative cervical lymphadenitis is rare in children with limited information about the frequency of neutropenia in any series. METHODS: We conducted a retrospective review of pediatric patients in whom suppurative cervical lymphadenitis was diagnosed between April 2011 and March 2016 at a tertiary children's hospital in Tokyo, Japan. Microbiologically confirmed cases of cervical lymphadenitis with abscess formation were included in the analysis. RESULTS: Twenty-five patients (median age, 1 yr old; 64% female) with abscess formation caused by Staphylococcus aureus were identified. Among these 25 patients, 5 (20%) met the criteria for chronic neutropenia and 4 (80%) received the final diagnosis of autoimmune neutropenia based on the identification of the serum anti-CD16 antibodies. CONCLUSIONS: Chronic neutropenia and autoimmune neutropenia were relatively common among infants with suppurative cervical lymphadenitis caused by S. aureus.

Excessive localized leukotriene B4 levels dictate poor skin host defense in diabetic mice.

Poorly controlled diabetes leads to comorbidities and enhanced susceptibility to infections. While the immune components involved in wound healing in diabetes have been studied, the components involved in susceptibility to skin infections remain unclear. Here, we examined the effects of the inflammatory lipid mediator leukotriene B4 (LTB4) signaling through its receptor B leukotriene receptor 1 (BLT1) in the progression of methicillin-resistant Staphylococcus aureus (MRSA) skin infection in 2 models of diabetes. Diabetic mice produced higher levels of LTB4 in the skin, which correlated with larger nonhealing lesion areas and increased bacterial loads compared with nondiabetic mice. High LTB4 levels were also associated with dysregulated cytokine and chemokine production, excessive neutrophil migration but impaired abscess formation, and uncontrolled collagen deposition. Both genetic deletion and topical pharmacological BLT1 antagonism restored inflammatory response and abscess formation, followed by a reduction in the bacterial load and lesion area in the diabetic mice. Macrophage depletion in diabetic mice limited LTB4 production and improved abscess architecture and skin host defense. These data demonstrate that exaggerated LTB4/BLT1 responses mediate a derailed inflammatory milieu that underlies poor host defense in diabetes. Prevention of LTB4 production/actions could provide a new therapeutic strategy to restore host defense in diabetes.

Macrophage-derived LTB4 promotes abscess formation and clearance of Staphylococcus aureus skin infection in mice.

The early events that shape the innate immune response to restrain pathogens during skin infections remain elusive. Methicillin-resistant Staphylococcus aureus (MRSA) infection engages phagocyte chemotaxis, abscess formation, and microbial clearance. Upon infection, neutrophils and monocytes find a gradient of chemoattractants that influence both phagocyte direction and microbial clearance. The bioactive lipid leukotriene B4 (LTB4) is quickly (seconds to minutes) produced by 5-lipoxygenase (5-LO) and signals through the G protein-coupled receptors LTB4R1 (BLT1) or BLT2 in phagocytes and structural cells. Although it is known that LTB4 enhances antimicrobial effector functions in vitro, whether prompt LTB4 production is required for bacterial clearance and development of an inflammatory milieu necessary for abscess formation to restrain pathogen dissemination is unknown. We found that LTB4 is produced in areas near the abscess and BLT1 deficient mice are unable to form an abscess, elicit neutrophil chemotaxis, generation of neutrophil and monocyte chemokines, as well as reactive oxygen species-dependent bacterial clearance. We also found that an ointment containing LTB4 synergizes with antibiotics to eliminate MRSA potently. Here, we uncovered a heretofore unknown role of macrophage-derived LTB4 in orchestrating the chemoattractant gradient required for abscess formation, while amplifying antimicrobial effector functions.

Parotid abscess at a single institute in Korea.

OBJECTIVE: To investigate clinical features, treatment modality, and outcomes of patients with parotid abscess. METHODS: A retrospective chart review was conducted at Chonnam National University Hwasun Hospital January, 2006 to July, 2017. RESULTS: Among 13 patients, 4 patients had immunocompromised disease, and 3 patients had been diagnosed with pre-existing parotid tumor. Patients were treated with empirical intravenous broad-spectrum antibiotics. Among 13 patients, 7 patients (53.8%) had surgical incision, and drainage was conducted. There was no recurrence or death associated with parotid abscess; however, 1 patient with parotid abscess developed facial nerve palsy that persists, despite adequate treatment. CONCLUSION: After adequate treatment, including antibiotics and surgical drainage, the prognosis of parotid gland is good. In the case of parotid abscess of immunocompromised patients, we suggest rapid surgical procedure for speedy recovery and minimizing adverse effects.

Coagulase-Negative Staphylococcus Skin and Soft Tissue Infections.

Coagulase-negative staphylococcus organisms may be normal flora of human skin, however these bacteria can also be pathogens in skin and soft tissue infections. A summary of skin and soft tissue infections caused by coagulase-negative staphylococcus species is provided in this review. We conducted a search of the PubMed database using the following terms: abscess, auricularis, biofilm, capitis, cellulitis, coagulase, contaminant, cyst, draining, epidermidis, felon, folliculitis, furuncle, haemolyticus, hominis, indolent, infection, lugdunensis, mecA, microbiome, negative, osteomyelitis, paronychia, saprophyticus, skin, simulans, sinus, soft, staphylococcus, systemic, tissue, virulence, virulent, and vulvar. The relevant papers, and their references, generated by the search were reviewed. Skin and soft tissue infections have been observed to be caused by many coagulase-negative staphylococcus organisms: Staphylococcus auricularis, Staphylococcus capitis, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus lugdunensis, Staphylococcus saprophyticus, and Staphylococcus simulans. Coagulase-negative staphylococcus skin infections predominantly present as abscesses and paronychia. They are most common in elderly patients or those individuals who are immunosuppressed, and tend to be broadly susceptible to antibiotic treatment. In conclusion, albeit less common, coagulase-negative staphylococcus organisms can result in skin and soft tissue infections, particularly in older and/or immunocompromised individuals. A review of the literature found that coagulase-negative staphylococcus organisms are most commonly grown in cultures of abscesses and paronychia. Therefore, coagulase-negative staphylococcal organisms should not always be considered as contaminants or normal flora, but rather as causative pathogens. They are usually susceptible to antibiotics used to treat methicillin-sensitive Staphylococcus aureus.

Staphylococcus aureus infection dynamics.

Staphylococcus aureus is a human commensal that can also cause systemic infections. This transition requires evasion of the immune response and the ability to exploit different niches within the host. However, the disease mechanisms and the dominant immune mediators against infection are poorly understood. Previously it has been shown that the infecting S. aureus population goes through a population bottleneck, from which very few bacteria escape to establish the abscesses that are characteristic of many infections. Here we examine the host factors underlying the population bottleneck and subsequent clonal expansion in S. aureus infection models, to identify underpinning principles of infection. The bottleneck is a common feature between models and is independent of S. aureus strain. Interestingly, the high doses of S. aureus required for the widely used "survival" model results in a reduced population bottleneck, suggesting that host defences have been simply overloaded. This brings into question the applicability of the survival model. Depletion of immune mediators revealed key breakpoints and the dynamics of systemic infection. Loss of macrophages, including the liver Kupffer cells, led to increased sensitivity to infection as expected but also loss of the population bottleneck and the spread to other organs still occurred. Conversely, neutrophil depletion led to greater susceptibility to disease but with a concomitant maintenance of the bottleneck and lack of systemic spread. We also used a novel microscopy approach to examine abscess architecture and distribution within organs. From these observations we developed a conceptual model for S. aureus disease from initial infection to mature abscess. This work highlights the need to understand the complexities of the infectious process to be able to assign functions for host and bacterial components, and why S. aureus disease requires a seemingly high infectious dose and how interventions such as a vaccine may be more rationally developed.

INDEXES OF CYTOKINE PROFILE OF BLOOD IN PATIENTS WITH COMPLICATED ERYSIPELAS.

The cytokine blood profile in patients with complicated erysipelas was investigated. It was found that in patients with complications of erysipelas (gangrene, phlegmon, abscess, thrombophlebitis of the subcutaneous veins of the shin) levels of pro-inflammatory cytokines IL-1ß, TNF-α, IL-2, IL-6 in serum significantly increase and level of anti-inflammatory cytokine IL-4 increases slightly, as well as was found a significant increase in coefficients reflecting the ratio of pro-inflammatory and anti-inflammatory cytokines, which indicates the prevalence in the blood of examined patients with complications of erysipelas an anti-inflammatory properties. A more significant increase in pro-inflammatory cytokines serum levels is typical for patients with destructive forms of erysipelas - phlegmonous and gangrenous, a slight increase - for patients without purulent-necrotic component of complication (thrombophlebitis of the subcutaneous veins of the shin). In the future we plan to study pharmacological correction of shifts in cytokine blood profile with drugs with immunomodulating properties in patients with complicated erysipelas.

Activation of mast cells in skin abscess induced by Staphylococcus aureus (S. aureus) infection in mice.

The skin abscess is a common inflammatory disease that occurs following the ubiquitous S. aureus infection. In our study, a skin abscess murine model was established and the dynamics of mast cells chemotaxing was evaluated. In the S. aureus-infected mice, severe infiltration of inflammatory cells in the dermis were observed, and mast cells were markedly accumulated in the skins. Besides, tryptase, the marker for mast cells activation, has a positive correlation with mast cell activity. The mast cells identified in the tissues were likely to be activated since they were associated with cell degranulation and the presence of tryptase. Our results suggested that mast cells and its mediator tryptase contribute to the inflammation of skin abscess induced by S. aureus infection.