Staphylococcus epidermidis is a leading cause of hospital-acquired and biofilm-associated infections. Interactions of peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages with planktonic or biofilm phase S. epidermidis cells were studied. Biofilm phase bacteria exhibited higher attachment, as well as, a 10-fold higher intracellular survival in monocyte-derived macrophages than their planktonic counterparts. Stimulation of PBMCs and monocyte-derived macrophages was performed with live or formalin-fixed bacterial cells. Supernatant concentration of selected cytokines was measured by Luminex(®) xMAP(™) technology at different time points. As compared to planktonic phase, biofilm phase bacteria elicited lower amounts of proinflammatory cytokines and Th1 response cytokines, such as TNFα, IL-12p40, IL-12p70 and IFN-γ, whereas they enhanced production of IL-8, GM-CSF and IL-13. This phenomenon was independent of formalin pretreatment. Taken together, these results may contribute to interpretation of observed silent course of biofilm-associated infections.

BackgroundThe skin commensal and opportunistic pathogen Staphylococcus epidermidis is a leading cause of hospital-acquired and biomaterial-associated infections. The polysaccharide intercellular adhesin (PIA), a homoglycan composed of β-1,6-linked N-acetylglucosamine residues, synthesized by enzymes encoded in icaADBC is a major functional factor in biofilm accumulation, promoting virulence in experimental biomaterial-associated S. epidermidis infection. Extracellular mucous layer extracts of S. epidermidis contain another major polysaccharide, referred to as 20-kDa polysaccharide (20-kDaPS), composed mainly out of glucose, N-acetylglucosamine, and being partially sulfated. 20-kDaPS antiserum prevents adhesion of S. epidermidis on endothelial cells and development of experimental keratitis in rabbits. Here we provide experimental evidence that 20-kDaPS and PIA represent distinct molecules and that 20-kDaPS is implicated in endocytosis of S. epidermidis bacterial cells by human monocyte-derived macrophages.ResultsAnalysis of 75 clinical coagulase-negative staphylococci from blood-cultures and central venous catheter tips indicated that 20-kDaPS is expressed exclusively in S. epidermidis but not in other coagulase-negative staphylococcal species. Tn917-insertion in various locations in icaADBC in mutants M10, M22, M23, and M24 of S. epidermidis 1457 are abolished for PIA synthesis, while 20-kDaPS expression appears unaltered as compared to wild-type strains using specific anti-PIA and anti-20-kDaPS antisera. While periodate oxidation and dispersin B treatments abolish immuno-reactivity and intercellular adhesive properties of PIA, no abrogative activity is exerted towards 20-kDaPS immunochemical reactivity following these treatments. PIA polysaccharide I-containing fractions eluting from Q-Sepharose were devoid of detectable 20-kDaPS using specific ELISA. Preincubation of non-20-kDaPS-producing clinical strain with increasing amounts of 20-kDaPS inhibits endocytosis by human macrophages, whereas, preincubation of 20-kDaPS-producing strain ATCC35983 with 20-kDaPS antiserum enhances bacterial endocytosis by human macrophages.ConclusionsIn conclusion, icaADBC is not involved in 20-kDaPS synthesis, while the chemical and chromatographic properties of PIA and 20-kDaPS are distinct. 20-kDaPS exhibits anti-phagocytic properties, whereas, 20-kDaPS antiserum may have a beneficial effect on combating infection by 20-kDaPS-producing S. epidermidis.

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The extracellular slime of Staphylococcus epidermidis contains, amongst various macromolecules, an acidic polysaccharide (PS) of a molecular mass of 20 kDa with significant antigenic and biological properties. The isolation procedure used so far includes multiple fractionations in anion-exchange chromatographic columns before its final purification by gel filtration chromatography. This protocol is laborious, time-consuming and includes the risk of unnecessary loss of PS quantities. Because of the significance of this PS, a modified protocol resulting in an easier and quicker isolation procedure was developed. Furthermore, identification, purity, charge density and molecular integrity of the isolated polysaccharide were evaluated by a reverse-polarity capillary electrophoresis method.

Introduction: Nocardiosis is an acute, subacute or chronic suppurative infection caused by Nocardia.It can be localised or systemic. Localised cutaneous or lymphocutaneous form occurs after an abrasion. Disseminated or systemic infection is seen in immunocompromised individuals. The primary disease occurs in the lung and subsequently haematogenous dissemination may occur to all organs of the body.Case Report: A 55 year old male presented with symptoms of pain in the left loin for 4 years, easy fatiguability since 2 years and fever for 1 year. His pain abdomen was intermittent, crampy and was associated with burning micturition.Two years back the patient was evaluated for extreme fatiguability and was found to be seropositive for HIV and was started on anti-retroviral drugs. His CD4 count was 38 cells/microliter (CD 4% −11.42). CT-KUB showed multiple multiple left renal calculi and left ureteric calculi with hydroureter. In view of left non-functioning kiney with stones, nephrectomy was performed. Gross examination of the excised nephro-ureterectomy specimen showed effacement of the entire kidney by tumorous mass with friable necrotic debris along with impacted calculi in the ureter. Microscopic examination showed numerous basophilic filamentous bacterial colonies surrounded by neutrophilic abscesses and dense infiltration by chronic inflammatory cells, which stained positive with acid fast bacilli. Kidney parenchyma showed sclerosed glomeruli, atrophic tubules and dense interstitial inflammatory infiltrate.A diagnosis of Renal nocardiosis was made.A detailed evaluation ruled out pulmonary or systemic involvement. He was started treatment with cotrimoxizole and doxycycline.Discussion: Majority of the cases present as invasive pulmonary infection,disseminated disease or brain abscess. Nocardiosis of kidney is seen in disseminated disease and presents as multiple pyelonephritic microabcesses.Our case had no evidence of pulmonary disease or any other organ involvement. Isolated renal Nocardiosis manifesting as a large tumorous mass is a rare presentation not described in literature to the best of our knowledge.