H. A. Verbrugh

Methicillin-resistant and -susceptible Staphylococcus aureus sequence type 398 in pigs and humans.

Methicillin-resistant Staphylococcus aureus sequence type 398 (ST398 MRSA) was identified in Dutch pigs and pig farmers. ST398 methicillin-susceptible S. aureus circulates among humans at low frequency (0.2%) but was isolated in 3 human cases of bacteremia (2.1%; p = 0.026). Although its natural host is probably porcine, ST398 MRSA likely causes infections in humans.

Biocompatibility of a Glucose-Polymer-Containing Peritoneal Dialysis Fluid

The currently available glucose-containing peritoneal dialysis fluids (PDF), which are all hyperosmolar, are toxic to the cells present in the peritoneal cavity. However, glucose-polymer solutions, being isosmolar, may have improved biocompatibility in this respect. We therefore compared in vitro the effects of PDF containing glucose-polymers with that of glucose solutions on the function of donor granulocytes and monocytes (MN), and on the viability of mesothelial cells. In addition, the function of peritoneal macrophages (PMO) of eight patients was studied in a randomized cross-over setting following intraperitoneal exposure to glucose-polymer-versus glucose-monomer-containing fluid of comparable ultrafiltration capacity. Donor granulocytes, as well as MN, showed significantly better phagocytosis of both Staphylococcus epidermidis and Escherichia coli after incubation in the glucose-polymer solution as compared with the 3.86% glucose-containing fluid. Their oxidative metabolism, as measured by chemiluminescence, also showed that the glucose-polymer solution was less inhibitory than fluids containing 2.27 or 3.86% glucose. Patient-derived PMO showed a significantly better phagocytic capacity for S epidermidis and E coli, a significantly higher killing of E coli, and a significantly higher chemiluminescence response after intraperitoneal exposure to the glucose-polymer solution as compared with the glucose-monomer-based fluid. Increasing the osmolality of the glucose-polymer solution to that of the respective glucose solutions blunted the favorable effect on phagocyte function, suggesting the beneficial effect to be osmolality-mediated. However, no major difference was observed between the glucose-polymer solution and the glucose-based fluid in their effects on mesothelial viability.(ABSTRACT TRUNCATED AT 250 WORDS)

Dialysis fluids and local host resistance in patients on continuous ambulatory peritoneal dialysis

The ability of polymorphonuclear leukocytes, monocytes and peritoneal macrophages to mount a respiratory burst in continuous ambulatory peritoneal dialysis (CAPD) fluids was tested in a phorbolmyristate acetate stimulated chemiluminescence assay. Fresh CAPD fluids depressed the chemiluminescence response of all three types of phagocytes tested to less than 18% of their chemiluminescence response in control buffer. When tested in spent CAPD fluids the suppression of chemiluminescence was 30–32%. Oxygen consumption of polymorphonuclear leukocytes was depressed in fresh CAPD fluids to below 40%. Both phagocytosis ofEscherichia coli by and bactericidal capacity of polymorphonuclear leukocytes and monocytes were suppressed in fresh CAPD fluids but not in spent effluents. The influence of acidic pH and hyperosmolality on phagocytic functions were studied separately by modifying the acidity or the glucose content of the control buffer. pH values below 6.0 significantly inhibited chemiluminescence but not phagocytosis. Under hypertonic conditions, both phagocytosis and chemiluminescence were inhibited. We conclude that the currently available CAPD solutions are beyond the limits of acid and osmotic tolerance of human phagocytic cells, and may thus compromise the peritoneal defenses of CAPD patients.

Defective Complement-Mediated Opsonization and Lysis of Bacteria in Commercial Peritoneal Dialysis Solutions

Complement-mediated opsonization and lysis of bacteria were studied in peritoneal dialysis solutions. Opsonization was assessed by the uptake of 3 H-labeled E. coli (serum-resistant strain ON2) by human blood leukocytes. Bacteriolysis was evaluated by the release of label from 3H-labeled E. coli (serum-sensitive strain K12). Uptake of ON2 was 46% after opsonization with 1% serum in control buffer, but only 2 to 15% of the bacteria were taken up after opsonization in peritoneal dialysis solutions. In contrast to complement-mediated opsonization bacterial opsonization with antibody was not reduced in dialysis solutions. Lysis of K12 was 26% and 78% in control buffer with 10% and 20% serum, respectively. In contrast, serum did not lyse K12 in dialysis solutions. Both the classical and alternative complement pathways functioned poorly in peritoneal dialysis solutions. Complement-mediated opsonization and lysis of E. coli was not dependent on the glucose concentration of the media but could largely be restored by increasing the pH of dialysis solutions from <5.5 to over 6.5. The amount of titrateable acid in commercial dialysis solutions varied from 0.055 to 0.167 mEq NaOH/dl among different suppliers. We conclude that commercial peritoneal dialysis solutions severely compromise the opsonic and bacteriolytic functions of serum complement which may be important in the peritoneal defense against infection.

Host — parasite relationship in staphylococcal infections: the role of the staphylococcal cell wall during the process of phagocytosis

Evidence is presented that antibodies against staphylococcal peptidoglycan are important opsonins for phagocytosis of staphylococci. Cell wall protein A inhibits opsonization by IgG through its interaction with the Fc fragment of the IgG molecule and preventing therefore the binding between the Fc fragment and the Fc receptor of the cell membrane of the leukocyte. Extracellular protein A interferes with opsonization presumably through depletion of complement.

Low-calcium peritoneal dialysis fluid should not impact peritonitis rates in continuous ambulatory peritoneal dialysis.

It has been suggested that reducing the calcium content of peritoneal dialysis fluid (PDF) to 2.5 mEq/L decreases peritoneal macrophage (PMO) function and increases the incidence of peritonitis (especially Staphylococcus epidermidis peritonitis) in continuous ambulatory peritoneal dialysis patients. We studied the uptake and killing of S epidermidis and Escherichia coli by PMOs and peripheral blood leukocytes incubated in control buffer (Hanks balanced salt solution containing 0.1% gelatin [GHBSS]) and PDF containing varying concentrations of calcium (O to 3.5 mEq/L) and magnesium (O to 1.5 mEq/L) using ether diamine tetraacetic acid and ethylenediaminetetraacetic acid chelation, respectively. In addition, interleukin-1-beta-induced interleukin-6 production by human mesothelial cells was measured in the presence of concentrations of calcium increasing from 0 to 3.0 mmol/L. Fc receptor- mediated uptake of S epidermidis by PMO in the complete absence of Ca++ was comparable to that by PMO incubated in GHBSS with calcium. In contrast, the complement-dependent uptake of E coli was significantly lower in GHBSS devoid of Ca++ (46% +/- 5% v 24% +/- 3%; 0.05 < P < 0.02). No effect on intracellular killing of either microorganism by PMO was observed. The same held true for the phagocytic and killing capacity of polymorphonuclear granulocytes and monocytes obtained from healthy donors. Using Ca++ (2 to 3.5 mEq/L) and Mg++ (0.5 to 1.5 mEq/L) concentrations as applied in commercial PDFs, however, phagocytes performed as well as in control buffer. Interleukin-6 production by stimulated human mesothelial cells also required a small amount of Ca++ only, being normal above the 0.1 to 3 mmol/L Ca+ + range tested. Thus, complement- dependent uptake of bacteria by phagocytes is calcium dependent, whereas antibody-dependent uptake of S epidermidis is not. The concentrations of calcium in the current PDFs, however, will not compromise human mesothelial cells and leukocyte functions, and therefore should not impact the peritonitis rate.

CAPD, a Permanent State of Peritonitis: A Study on Peroxidase Activity

In vivo in the animal model peritoneal macrophages can be divided by their peroxidase activity (PA) pattern in exudate-, exudate-resident-, resident- and PA-negative macrophages. In the normal steady state 90% of the macrophages are resident cells. After acute inflammation, exudate and exudate-resident macrophages appear, whereas after chronic inflammation exudate and PA-negative macrophages appear. CAPD patients with clear peritoneal effluent were studied because they are considered to be in a normal steady state. However, in only one of six patients resident macrophages were found. Exudate and PA-negative macrophages were always found, suggesting that in otherwise asymptomatic CAPD chronic inflammation exists. The clinical significance of the presence of resident macrophages is discussed.

The Effect of Influenza Virus on Oxygen-Dependent Metabolism of Human Neutrophils

Many viral infections predispose to bacterial superinfectionsl. The increased susceptibility to bacterial infections has been explained by the effect of viruses on the phagocytic host defense2–9. Controversy exits about the mechanism of action of influenza virus on the phagocytic cell function. Some studies showed a defect in uptake of bacteria by virus-treated PMN with intact O2 dependent microbicidal activity9, while other studies showed the opposite7,10. Because of these discrepancies we studied the effect of influenza virus on the respiratory burst of human neutrophils.

Survival and Growth of Staphylococcus epidermidis within Phagocytes in Relation to Recurrent Peritonitis in Continuous Ambulatory Peritoneal Dialysis Patients

Staphylococcus epidermidis is the most prevalent pathogen in continuous ambulatory peritoneal dialysis (CAPD) peritonitis.(1, 2) Peritonitis episodes recur or relapse in up to 36% of cases.(2–4) and a considerable proportion of the recurrent peritonitis episodes is seen in patients infected with either Staph. epidermidis or Staph. aureus. Little is known about the pathogenetic mechanisms that lead to the recurrence of peritonitis.

The Biology of the Peritoneal Membrane During Chronic Peritoneal Dialysis

The peritoneal cavity is lined by a membrane consisting of a single layer of mesothelial cells resting on a thin basement membrane; underneath the mesothelial cell layer loose connective tissues contain the capillaries that are essential for dialysis. The mesothelial cell layer is rather unique, it is of mesodermal origin and covers the large body cavities. Morphologic studies have shown that mesothelial cells have microvilli on their apical surface and that their surfaces are covered with slippery glycocalix1,2.