Immunological characterization of IgG subclass deficiency reveals decreased Tregs and increased circulating costimulatory and regulatory immune checkpoints

BackgroundImmunoglobulin G subclass deficiencies (IgGsd) comprise a wide clinical spectrum from no symptoms to repeated respiratory infections and risk for the development of lung damage. Our aims were to investigate whether the immunological phenotype of IgGsd patients on and off immunoglobulin replacement therapy (IgRT) was reflected in the clinical features of IgGsd.MethodThirty patients with IgGsd were included in this prospective study of 18 months of IgRT, followed by 7-18 months of IgRT discontinuation. Blood samples were collected when patients were on and off IgRT and compared with samples from 34 cross-sectional healthy controls. An in-depth lymphocyte phenotyping was performed by flow cytometry and plasma levels of immune checkpoints were assessed.ResultsIgG3 subclass deficiency was most common. Patients with IgGsd had decreased levels of activated T cells and B cells and plasma levels of negative immune checkpoint molecules correlated negatively with T cell and B cell activation. The decreased T cell activation level was unaffected by IgRT, while the B cell activation was partly restored. Of note, decreased levels of activated regulatory T cells (Tregs) were found in IgGsd patients and was partly restored during IgRT. The profile of comorbidities did not associate with Treg levels.DiscussionIgGsd is associated with decreased B cell and T cell activation including Tregs, and increased plasma levels of negative immune checkpoint molecules. The consequence of reduced activated Tregs in IgGsd remains unclear. Decreased immune cell activation was partly restored during IgRT, demonstrating that IgRT may contribute to improved immune function in patients with IgGsd

Pathogenic Mechanisms and Host Interactions in Staphylococcus epidermidis Device-Related Infection

Staphylococcus epidermidis is a permanent member of the normal human microbiota, commonly found on skin and mucous membranes. By adhering to tissue surface moieties of the host via specific adhesins, S. epidermidis is capable of establishing a lifelong commensal relationship with humans that begins early in life. In its role as a commensal organism, S. epidermidis is thought to provide benefits to human host, including out-competing more virulent pathogens. However, largely due to its capacity to form biofilm on implanted foreign bodies, S. epidermidis has emerged as an important opportunistic pathogen in patients receiving medical devices. S. epidermidis causes approximately 20% of all orthopedic device-related infections (ODRIs), increasing up to 50%in late-developing infections. Despite this prevalence, it remains underrepresented in the scientific literature, in particular lagging behind the study of the S. aureus. This review aims to provide an overview of the interactions of S. epidermidis with the human host, both as a commensal and as a pathogen. The mechanisms retained by S. epidermidis that enable colonization of human skin as well as invasive infection, will be described, with a particular focus upon biofilm formation. The host immune responses to these infections are also described, including how S. epidermidis seems to trigger low levels of pro-inflammatory cytokines and high levels of interleukin-10, which may contribute to the sub-acute and persistent nature often associated with these infections. The adaptive immune response to S. epidermidis remains poorly described, and represents an area which may provide significant new discoveries in the coming years

Transcriptomic analysis of milk somatic cells in mastitis resistant and susceptible sheep upon challenge with Staphylococcus epidermidis and Staphylococcus aureus

<p>Abstract</p> <p>Background</p> <p>The existence of a genetic basis for host responses to bacterial intramammary infections has been widely documented, but the underlying mechanisms and the genes are still largely unknown. Previously, two divergent lines of sheep selected for high/low milk somatic cell scores have been shown to be respectively susceptible and resistant to intramammary infections by <it>Staphylococcus spp</it>. Transcriptional profiling with an 15K ovine-specific microarray of the milk somatic cells of susceptible and resistant sheep infected successively by <it>S. epidermidis </it>and <it>S. aureus </it>was performed in order to enhance our understanding of the molecular and cellular events associated with mastitis resistance.</p> <p>Results</p> <p>The bacteriological titre was lower in the resistant than in the susceptible animals in the 48 hours following inoculation, although milk somatic cell concentration was similar. Gene expression was analysed in milk somatic cells, mainly represented by neutrophils, collected 12 hours post-challenge. A high number of differentially expressed genes between the two challenges indicated that more T cells are recruited upon inoculation by <it>S. aureus </it>than <it>S. epidermidis</it>. A total of 52 genes were significantly differentially expressed between the resistant and susceptible animals. Further Gene Ontology analysis indicated that differentially expressed genes were associated with immune and inflammatory responses, leukocyte adhesion, cell migration, and signal transduction. Close biological relationships could be established between most genes using gene network analysis. Furthermore, gene expression suggests that the cell turn-over, as a consequence of apoptosis/granulopoiesis, may be enhanced in the resistant line when compared to the susceptible line.</p> <p>Conclusions</p> <p>Gene profiling in resistant and susceptible lines has provided good candidates for mapping the biological pathways and genes underlying genetically determined resistance and susceptibility towards <it>Staphylococcus </it>infections, and opens new fields for further investigation.</p

Coagulase-negative staphylococci in prosthetic hip infections

More than 11,000 primary total hip replacements were performed in Sweden in the year 2000, corresponding to 125 primary total hip replacements per 100,000 inhabitants, according to The Swedish Total Hip Replacement Register. In general, this procedure provides highly satisfactory results. The most common complications associated with prosthetic hip joints are aseptic biomechanical failures and infections. Delayed low-grade infections occur most often, and they are also the most difficult to distinguish from aseptic mechanical failures because of similar symptoms.During the period 1994 to 2001, a prospective study was conducted to compare inflammatory markers in blood, synovial fluid, and histopathological specimens in patients diagnosed with aseptic or septic loosening of hip prostheses. Coagulase-negative staphylococci (CoNS) were found to be the most common pathogens in the patients with prosthetic hip joint infections.Further characterisation of the CoNS revealed that patients were co-infected with the following: (i) CoNS and other bacterial species, (ii) various CoNS species, and (iii) different S. epidermidis clones. Expression of the icaADB gene complex, which is important for the biofilm mode-of-growth characteristic of S. epidermidis, was not necessary to allow S. epidermidis to infect orthopaedic prostheses. The majority of the S. epidermidis isolates, both from prostheses and normal bacteria flora, were able to bind to at least one of the extracellular matrix proteins we tested, this adhesion ability is a probable virulence factor. Histologically, the extent of cell infiltration differed between aseptic and septic loosening of prostheses, and neutrophils in tissue at a rate of ≥ 5 cells/high power field greatly favoured infection. Periprosthetic tissue contained the cells that are required not only for an innate, but also a specific, immune response, which supports the theory that the limited systemic inflammatory response in infections of hip prostheses is not due to failure of inflammatory cells to reach the infected area, but is more likely caused by an inadequate response to the infecting organisms.Therefore, we studied the interactions between neutrophils and S. epidermidis (the most common CoNS species in hip prosthetic infections). Neutrophils phagocytosed both surfaceadherent and planktonic S. epidermidis, but they ingested adherent S. aureus isolates more readily than they consumed adherent S. epidermidis. The reduced phagocytosis of S. epidermidis by neutrophils is viewed as a virulence factor, together with the lack of an ability to prime or sufficiently activate the neutrophil oxidase, and thereby evade adequate killing by neutrophils. The weak oxidative activation agrees with the low inflammatory response seen in patients with S. epidermidis infections related to implanted devices. Furthermore, both planktonic and adherent S. epidermidis delayed neutrophil apoptosis, and we suggest that this leads to the accumulation of neutrophils at the site of inflammation. We propose that the complex interplay between the S. epidermidis-induced delay in apoptosis in neutrophils and the interaction of S. epidermidis-containing neutrophils with macrophages in periprosthetic tissue has negative impact on the outcome in patients with prosthetic hip joint infections, resulting in low grade inflammation, tissue damage, and finally loosening of the prosthesis.Fler än 11.000 primära totala höftutbytesoperationer utfördes i Sverige 2000, detta motsvarar 125 operationer per 100.000 innevånare enligt Svenska Nationella Höftplastikregistret. Höftprotesoperationer uppvisar vanligen mycket goda resultat, men komplikationer förekommer där de vanligaste är aseptisk lossning respektive infektioner i anslutning till proteserna. De sena, läggrarliga infektionerna är vanligast, och det är också dessa, som är svårast att skilja från mekaniska lossningar på grund av liknande symtom.Under perioden 1994 till 2001 utfördes en prospektiv studie för att jämföra inflammatoriska markörer i blod, ledvätska och i vävnad hos patienter med diagnosen aseptisk respektive septisk (infektiös) lossning av höftproteser. Koagulas-negativa stafylokocker (KNS) var den vanligaste sjukdomsframkallande bakterien hos patienter med infekterade höftproteser. Vidare karakterisering av KNS visade att höftprotespatienterna var infekterade enligt följande: (i) KNS plus andra bakteriella arter, (ii) olika KNS arter, och (iii) olika kloner av S. epidermis. Uttryck av icaADB gen komplexet, som är viktigt för utvecklandet av biofilm vilket är ett sätt att växa som är karakteristiskt för S. epidermidis bakterier, visade sig inte vara nödvändigt för att utveckla protesinfektion med S. epidermidis. Majoriteten av S. epidermidis, både de som isolerades från höftproteser respektive från hudens normalflora, hade förmåga att binda in till åtminstone ett av de extracellular matrix proteiner som testades. Denna adhesionsförmåga är en trolig virulensfaktor. Histologiskt (i vävnaden) skiljde sig cellinfiltrationen mellan aseptiska och septiska lossningar, och neutrofiler i ett antal av ≥ 5 celler/högupplösningsfält talade starkt för infektion. Vävnaden kring protesen innehöll celler som behövs, inte bara för ett ospecifikt immunsvar utan också för ett specifikt immunsvar. Detta stödjer hypotesen att de begränsade systemiska inflammatoriska svaret vid höftprotesinfektioner inte beror på att immuncellerna inte förmår ta sig dit, utan troligare beror på att immuncellerna svarar inadekvat på de infekterande bakterierna.Därför studerade vi vidare samspelet mellan neutrofiler och S. epidermidis (den vanligaste KNS-arten vid höftprotesinfektioner). Neutrofiler hade förmåga att fagocytera (äta upp) både ytbundna och i lösning förekommande S. epidermidis, men ytbundna S. aureus fagocyterades lättare än ytbundna S. epidermidis. Den sämre fagocytosen av S. epidermidis tolkas som en virulensfaktor hos S. epidermidis, tillsammans med frånvaro av förmåga att "prima" eller tillräckligt aktivera neutrofilemas oxidas och genom det undvika avdödning. Den svaga oxidativa aktiveringen stämmer med det låga inflammatoriska svar som ses hos patienter med S. epidermidis infektioner i anslutning till inopererade material. Vidare försenade både S. epidermidis i lösning och adhererade bakterier neutrofilemas apoptos (spontan celldöd), vilket föreslås leda till att neutrofilema samlas på stället för inflammation. Vi föreslår att det komplexa sambandet mellan S. epidermidis-inducerad försenad neutrofildöd och interaktionen mellan S. epidermidis-innehållande neutrofiler och makrofager i vävnaden kring proteser resulterar i en låggradig inflammation, vävnadsskada och slutligen lossning av protesen.</p

In vitro antimicrobial synergy testing of coagulase-negative staphylococci isolated from prosthetic joint infections using Etest and with a focus on rifampicin and linezolid

In recent years, coagulase-negative staphylococci (CoNS) have been increasingly recognised as causative agents of various infections, especially in immunocompromised patients and related to implanted foreign body materials. CoNS, and especially Staphylococcus epidermidis, transform into a stationary growth phase and produce biofilm when involved in a foreign body infection, making them difficult to eradicate with antimicrobials. Rifampicin has the ability to penetrate biofilm, but resistance may develop rapidly. To reduce the emergence of resistance, rifampicin should be combined with additional antimicrobials, of which several different ones have been proposed, including the relatively new class of antimicrobials, oxazolidinones, represented by linezolid. Thirty-seven CoNS isolates from patients with prosthetic joint infection were investigated by synergy testing using Etest. Nine antimicrobial combinations, based on either rifampicin or linezolid, were tested. For 16 (43%) of the isolates, a synergistic (n = 5), additive (n = 14) and/or antagonistic (n = 11) effect were identified. In conclusion, Etest is an objective and easily performed in vitro method for antimicrobial synergy testing. However, each isolate requires testing for the specific combination considered for treatment.</p

Prevalence of the ica operon and insertion sequence IS256 among Staphylococcus epidermidis prosthetic joint infection isolates

Joint replacement surgery has improved the quality of life for hundreds of thousands of patients. However, the infection of a joint implant is an important and serious complication, though the prevalence is low. Staphylococcus epidermidis is the most important pathogen involved in foreign-body infections. S. epidermidis is also a commensal that comprises a substantial part of the normal skin flora of humans. The possibility to demonstrate potential specific virulence markers may facilitate the interpretation of the bacteriological findings, as well as the clinical decision. The prevalence of the ica locus and insertion sequence IS256 by using polymerase chain reaction (PCR) among 32 clinical S. epidermidis isolates from prosthetic joint infections (PJIs) and 24 commensal isolates from nares and skin was investigated. Sixteen (50%) of the 32 PJI isolates harbored the ica operon compared with one-third of the commensal isolates obtained from the samples of the skin and nares of healthy individuals. The IS256 was demonstrated in 26 (81%) out of 32 PJI isolates. By contrast, IS256 was found in one of 24 commensal isolates. In conclusion, IS256 may be superior to the ica operon as a marker of the invasive capacity of S. epidermidis, since it was found in most of the PJI isolates, but rarely among commensals.</p

Interaction of <em>staphylococcus epidermidis</em> from infected hip prostheses with neutrophil granulocytes

This study focuses on the interaction of Staphylococcus epidermis isolated from granulation tissue covering infected hip prostheses and neutrophil granulocytes. Bacterial strains isolated from normal flora were used as controls. The bacteria were well characterized with routine methods and further characterized with random amplified polymorphic DNA analyses and slime tests. Phagocytosis and chemiluminescence (CL) assays were used in the neutrophil interaction studies. The prostheses strains were ingested to a lesser extent than strains from normal flora (p ≤ 0.001). There was no significant difference between the prostheses strains and the normal flora strains in terms of total CL response. However, the extracellular CL response from the neutrophils was lower in comparison with the normal flora when interacting with the prostheses strains. The results of this study support the notion that S. epidermidis strains isolated from infected hip prostheses have an enhanced capacity to resist phagocytosis and that most of these strains elicit a reduced inflammatory response, measured as the production of extracellular oxidative metabolites from the neutrophils, compared to normal flora.</p

Cutibacterium acnes (formerly Propionibacterium acnes) isolated from prosthetic joint infections is less susceptible to oxacillin than to benzylpenicillin

Introduction: The frequency of prosthetic joint infections (PJIs) due to Cutibacterium acnes (formerly Propionibacterium acnes) is increasing, especially shoulder PJIs. The recommended antibiotic prophylaxis for hip and knee arthroplasties is beta-lactam antibiotics, predominantly cephalosporins. However, for example in Sweden, isoxazolyl-penicillin cloxacillin is used. No specific recommendations for shoulder arthroplasties are available. The aim of the present study was to determine the minimum inhibitory concentration (MIC) values for different antibiotics for C. acnes; and, more specifically, to compare the MIC values for benzylpenicillin and oxacillin. Materials and methods: Minimum inhibitory concentration (MIC) values for nine different antibiotic agents were obtained by gradient test (Etest) using strains of C. acnes (n= 57) isolated from PJIs from shoulders (n=31), hips (n=21), and knees (n=5). Results: All isolates had low MIC values for most of the tested antibiotic agents, and showed a wild type MIC distribution. The exception was clindamycin with 9% of the isolates displaying decreased susceptibility. The MIC values obtained for benzylpenicillin were significantly lower than the MIC values for isoxazolyl-penicillin (oxacillin). Conclusion: These in vitro results indicate that benzylpenicillin might be a more effective prophylactic treatment to prevent shoulder PJIs caused by C. acnes. However, further studies on the subject are needed, and the effectiveness of the prophylactic treatment should be evaluated using randomized controlled studies and/or register-based studies

In vitro activity of tedizolid and linezolid against Staphylococcus epidermidis isolated from prosthetic joint infections.

Prosthetic joint infections (PJIs) are rare but long-lasting and are serious complications without any spontaneous resolution, requiring additional surgery and long-term treatment with antibiotics. Staphylococci are the most important aetiological agents of PJIs, and among the coagulase-negative staphylococci Staphylococcus epidermidis is the most common. However, S. epidermidis often displays multidrug resistance (MDR), demanding additional treatment options. The objective was to examine the effectiveness of tedizolid and linezolid against S. epidermidis isolated from PJIs. The standard antibiotic susceptibility pattern of S. epidermidis (n = 183) obtained from PJIs was determined by disc diffusion test, and MIC was determined by Etest for tedizolid, linezolid, and vancomycin. Tedizolid displayed MIC values ranging from 0.094 to 0.5 mg/L (MIC50: 0.19 mg/L, MIC90: 0.38 mg/L), linezolid MIC values ranging from 0.25 to 2 mg/L (MIC50: 0.75 mg/L, MIC90: 1 mg/L), and vancomycin MIC values ranging from 0.5 to 3 mg/L (MIC50 and MIC90 both 2 mg/L). According to the disc diffusion test, 153/183 (84%) isolates were resistant to ≥3 antibiotic groups, indicating MDR. In conclusion, S. epidermidis isolates from PJIs were fully susceptible, and the MIC50 and MIC90 values for tedizolid were two- to four-fold dilution steps lower compared with linezolid. Tedizolid is not approved, and there are no reports of long-term treatment, but it may display better tolerability and fewer adverse effects than linezolid; it thus could be a possible treatment option for PJIs, alone or in combination with rifampicin.Funding agencies: Nyckelfonden at Orebro University Hospital</p