Lipid-mediated resistance of Gram-negative bacteria against various pore-forming antimicrobial peptides

Lipopolysaccharides (LPSs) play a dual role as target and as effector molecules. The knowledge of the LPS-induced activation of human immune cells is increasing; however, surprisingly, much less effort seems to be directed towards the understanding of the mechanisms leading to the killing of the bacterial organisms, which eventually results in the release of LPS from the bacterial surface into the blood circulation. We demonstrate mechanisms of interaction of peptides of the innate immune system (e.g. defensins and cathelicidins) as well as of externally administered antibiotics (e.g. Polymyxin B) with Gram-negative bacteria. The main focus is directed on data derived from electrical measurements on a reconstitution system of the outer membrane as an asymmetric bilayer composed on one side of LPS and on the other of phospholipids. All these antimicrobial peptides (AMPs) are membrane-active and induce the permeabilization of the reconstituted membranes by the formation of lesions. We found that differences in the activity of the AMPs against various sensitive and resistant Gram-negative bacteria can be explained solely by variations in the chemical structure of LPS, e.g. in the composition of the sugar head group. A reduction of the net negative charge of LPS is responsible for a reduced interaction with the polycationic AMPs and thus for resistance. A most important side effect of positively charged AMPs is the neutralization of the negatively charged LPS released from the bacterial surface as a consequence of AMP-induced killing.     

Intravenous immunoglobulin therapy in vasculitis

Initially, intravenous immunoglobulins (IVIgs) were used as replacement therapy in primary and secondary antibody-deficiency syndromes. The clinical use of IVIg has been extended during the past decade to a wide variety of clinical conditions, such as infectious processes, neuroimmunological diseases, and different systemic autoimmune diseases. The mode of action of IVIg is complex, involving modulation of the Fc receptors, interference with the complement and cytokine network, and effects on the activation and differentiation of T and B-cells. Kawasaki disease (KD) was one of the first diseases within the group of primary vasculitides in which IVIg were used. Today, there is a clear evidence of benefit for IVIg in the treatment of coronary artery abnormalities related to KD. Subsequently, various reports have suggested a beneficial effect in other vasculitides; however, there are few data from controlled studies. For antineutrophil cytoplasmic antibody-associated vasculitis (AAV) one placebo-controlled and several open-label studies have shown a beneficial effect on the disease activity in patients with Wegener's granulomatosis or microscopic polyangiitis refractory to standard therapy with prednisone and cyclophosphamide. For other vasculitides, such as polyarteritis nodosa or Henoch-Schonlein purpura, only case reports have described an inhibition of a disease progression by IVIg so far. However, the effect was partly only temporary. In conclusion, KD and AAV are the only vasculitides with a definite beneficial use of IVIg. For other vasculitides, the efficacy of IVIg has not been proven properly but may be useful in single cases.     

Colon microflora in infants fed formula with galacto- and fructo-oligosaccharides: more like breast-fed infants

OBJECTIVES: The intestinal flora of breast-fed infants is generally dominated by Bifidobacteria. We aimed to investigate whether an infant formula supplemented with galacto-oligosaccharides and fructo-oligosaccharides (GOS/FOS) is able to establish a bifido-dominant microflora, not only in numbers but also with respect to the metabolic activity in the colon. METHODS: Two groups of infants fed infant formula with 0.8 g/100 ml GOS/FOS in a ratio of 9:1 (OSF group), or control formula (SF group) were evaluated in a randomised, double blind, placebo controlled intervention study. A breast-fed group was studied in parallel. At study onset and after 4 and 6 weeks, faecal samples were examined for the number of bifidobacteria, pH, short chain fatty acids and lactate. RESULTS: After 6 weeks, the mean proportion of bifidobacteria was significantly higher in the OSF group (59.6% versus 49.5% in the SF group; P < 0.05). Compared with controls, infants in the OSF group had a lower stool mean pH and an increased proportion of acetate and a decreased proportion of propionate. The mean pH in the OSF and SF groups were 5.7 and 6.3, respectively (P < 0.001). CONCLUSIONS: The addition of the prebiotic GOS/FOS mixture to an infant formula has a stimulating effect on the growth of bifidobacteria and on the metabolic activity of the total intestinal flora. The changes in short chain fatty acids, lactate and pH in the prebiotic group represent a fermentation profile that is closer to that observed in breast-fed infants compared to infants fed control formula.     

Closed subfascial v.a.C.-therapy in periprosthetic hip infections

Infections after hip arthroplasty can lead to protracted and complicated treatments. A great problem is thereby the persistant secretion after surgical revision. 8 patients (3 x after acetabulum cup replacement, 2 x after Girdlestone hip, 2 x after spacer implantation and one case of rearthroplasty) have been treated with a V.A.C.-therapy after bacterial infection and persistant wound secretion. In all cases a pathogen organism could be identified during the frustrated attempts of sanitation. After meticulous debridement and jet lavage in each case, 1-3 polyvinyl sponges have been placed either periprosthetic or in the resection cavity with a transcutan tube outgoing. The wounds have been closed in layers. Initially a pressure of 200 mm Hg via V.A.C. has been attached. After 48-72 h an alteration from haemorrhagic to serous secret could be observed and afterwards the pressure has been reduced to 150 mm Hg. After a mean period of 11 days (8-13) the infection parameters have been retrogressive, the wound secretion was obviously reduced and the sponges were removed. During the remaining hospitalization of each patient no complications occured. In the mean follow-up of 21 months (2-46) no reinfections have been observed. Although the V.A.C.-therapy does not count to the primary therapy concepts of periprosthetic hip infections, it stands for an effective therapy option in exclusive cases.     

Coronary flow reserve measurements in hypertension

Taken together, the diagnostic algorithm is leaded by a simple ECG stress test. In case of ST-segment depression the preferred image test should be stress ECG to bring patients at high risk for significant epicardial coronary artery stenosis to coronary angiography (and revascularization). In case of the lack of wall motion abnormalities (during stress-echo test) or absence of epicardial stenosis one may further assess coronary flow reserve with noninvasive Doppler harmonic echocardiography. For ultimate quantitative assessment invasive procedures, such as argon dilution or intracoronary Doppler techniques, represent the appropriate approach. Treatment of microvascular disease may be followed-up by these new noninvasive diagnostic approaches in future and also, at present, by monitoring ST-segment depression.     

Pharmacokinetics and cellular uptake of imatinib and its main metabolite CGP74588

Despite the remarkable clinical response rates to imatinib in the treatment of bcr-abl leukemic patients, pharmacokinetic data on this relatively novel substance are needed to improve our understanding of the emergence of resistance, the interindividual variations of clinical response and the clinical and biologic relevance of its main metabolite N-desmethyl-imatinib. We present here pharmacokinetic data obtained with a newly designed HPLC approach in 97 patients with chronic myeloid leukemia or acute lymphatic leukemia (ALL) under treatment with imatinib that allowed us to calculate the AUC (39.5 g·h/ml for an oral dose of 400 mg daily), the t_1/2 (18.2 h) and the peak concentration (1.92 /ml for an oral dose of 400 mg daily) of imatinib in plasma. In a subgroup of patients, the same parameters were analyzed for N-desmethyl-imatinib. We also provide data on the imatinib concentration in the cerebrospinal fluid (CSF) of ALL patients and demonstrate that oral administration of imatinib resulted only in a marginal flux across the blood-brain barrier. Finally, in an in vitro setting, we determined cellular concentrations of imatinib in HL-60 cells and showed an over-proportional uptake both in RPMI medium and in human plasma. Using an arithmetical approach combining all parameters obtained in imatinib-treated patients, we finally provide a conclusive approximation of basic pharmacokinetic data for both imatinib and its main metabolite N-desmethyl-imatinib.     

Fanconi syndrome caused by antiepileptic therapy with valproic Acid

PURPOSE: Valproic acid (VPA) is commonly used as an antiepileptic drug (AED). Regular screening for renal side effects is uncommon. Fanconi syndrome, a generalized dysfunction of renal proximal tubular cells, occurs with some inborn errors of metabolism. In addition, it can be acquired by exposure to several toxic substances. We report a case of Fanconi syndrome after long-term therapy with VPA. METHODS: An 8-year-old severely disabled and developmentally retarded boy with epilepsy was treated with VPA over a period of 7 years. He was hospitalized after a status epilepticus with laboratory findings suggesting a Fanconi syndrome. A PubMed-based worldwide review of the literature revealed that Fanconi syndrome is a rare side effect in children during long-term VPA treatment. We analyzed all 10 previously published cases by comparing age, underlying diseases, medication, and outcome. RESULTS: Examination revealed metabolic acidosis suggestive of renal tubular malfunction. Based on typical clinical and laboratory findings, an acquired Fanconi syndrome was diagnosed. This was treated with large doses of sodium bicarbonate. After discontinuation of VPA, renal function completely normalized within 2 months. CONCLUSIONS: Fanconi syndrome appears to be a rare but severe consequence of long-term VPA therapy. Therefore patients treated with VPA should be checked regularly for the possible development of VPA-induced Fanconi syndrome.