The mean annual incidence of hemolytic uremic syndrome in persons <15 years of age in Italy from 1988 to 2000 was 0.28 per 100,000 population. Laboratory investigations showed that Shiga toxin–producing Escherichia coli (STEC) infection occurred in 73.1% of patients. STEC O157 was the most common serotype, but a considerable number of cases were from infections by non-O157 STEC.

SUMMARYGroup B streptococci (GBS ) are an important cause of neonatal sepsis, pneumonia and meningitis. In the early phase of infection, macrophages and polymorphonuclear cells (PMN ) are the first immune cells that interact with GBS. In this in vitro study, to gain insight into GBS-macrophage interaction in the absence of type-specific antibodies, we examined the features of GBS survival in thioglycollate-elicited murine peritoneal macrophages and the effect of GBS on the protein kinase C (PKC )-dependent transduction pathway. Our results demonstrate that type Ia GBS, strain 090 (GBS-Ia) and type III GBS strain COH 31r/s (GBS-III ), after in vitro phagocytosis survive and persist intracellularly in macrophages for up to 24 and 48 hr, respectively. However, macrophage activation by interferon-c (IFN-c) and lipopolysaccharide from Escherichia coli (LPS ) caused a significant reduction in the time of intracellular persistence. Macrophage activation by IFN-c and LPS seems to be a multifactorial event involving multiple intracellular signal pathways also including PKC. Since PKC is one of the components in the signal network leading to macrophage activation and an important target for several intracellular micro-organisms, we wondered whether PKC could have a role in intracellular GBS survival. Both PKC depletion by treatment with phorbol 12-myristate 13-acetate (PMA) for 18 hr and PKC inhibition by Calphostin C rendered macrophages more permissive for the intracellular GBS survival. Furthermore, GBSinfected macrophages were unable to respond to PMA and LPS, activators of PKC, by inducing antimicrobial activity. The ability of GBS to impair PKC-dependent cell signalling was also demonstrated by the reduced c-fos gene expression in GBS-infected macrophages with respect to control macrophages, after LPS stimulation. In conclusion, our results indicate that GBS survive in macrophages and impairment of PKC signal transduction contributes to their intracellular survival. INTRODUCTIONcorrelates with the susceptibility or resistance of neonates to GBS infection.15,16 Group B streptococci (GBS ) are the major cause of pneuThe discovery that macrophages can phagocytose GBS in monia, sepsis and meningitis in neonates and a serious cause the absence of immune serum by C3-dependent binding17 and of mortality or morbidity in immunocompromised adults.1,2 C3-independent binding using complement receptor type three The main virulence factor of GBS is thought to be the capsular (CR3)18 suggests that there is also a potential role for antibodypolysaccharide because of its antiphagocytic properties.3,4 In independent mechanisms in resistance to GBS infection. resistance to GBS infection, a central role is played by antiHowever, the recent demonstration that type III GBS phagobodies to the type-specific capsular polysaccharide and complecytosed by a macrophage-like line J774 in the absence of typement which potentiate in vitro phagocytosis and GBS killing specific antibodies survived within its host cell,19 seems to by phagocytic cells...

This is the first study showing the presence of adhesive-invasive bacteria strains in the inflamed tissues of children with IBD. Collective features of these strains indicate that they belong to the AIEC spectrum, suggesting their possible role in disease pathogenesis.

Hemolytic-uremic syndrome, the main cause of acute renal failure in early childhood, is caused primarily by intestinal infections from some Escherichia coli strains that produce Shiga toxins. The toxins released in the gut are targeted to renal endothelium after binding to polymorphonuclear leukocytes. The presence of Shiga toxins in the feces and the circulating neutrophils of 20 children with hemolytic uremic syndrome was evaluated by the Vero cell cytotoxicity assay and flow cytometric analysis, respectively. The latter showed the presence of Shiga toxins on the polymorphonuclear leukocytes of 13 patients, 5 of whom had no other microbiologic or serologic evidence of infection by Shiga toxin-producing Escherichia coli. A positive relationship was observed between the amounts of Shiga toxins released in the intestinal lumen and those released in the bloodstream. The toxins were detectable on the neutrophils for a median period of 5 days after they were no longer detectable in stools. This investigation confirms that the immunodetection of Shiga toxins on neutrophils is a valuable tool for laboratory diagnosis of Shiga toxin-producing Escherichia coli infection in hemolytic-uremic syndrome and provides clues for further studies on the role of neutrophils in the pathogenesis of this syndrome.Hemolytic-uremic syndrome (HUS) is the most common cause of acute renal failure in children and is characterized by thrombocytopenia and microangiopathic hemolytic anemia (25). Most HUS cases occur as a complication of intestinal infections with Shiga toxin-producing Escherichia coli (STEC) (12,13,24).STEC produce two main types of toxins, Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2), which are composed of A and B subunits. The latter mediates the binding to glycolipid receptors (globotriaosylceramide) present on the surface of target cells (19). After endocytosis, an enzymatically active fragment (9) of the A subunit cleaves the bond connecting adenine to the sugar of 28S rRNA (8) and DNA (3, 4), thus causing the arrest of protein synthesis (8) and the formation of apurinic sites in the nucleus (4, 20). The final result of these intracellular injuries is the triggering of apoptosis (4, 17).The pathogenetic process of STEC infection initially involves colonization of the gut (19). STEC serogroups mainly associated with HUS, like E. coli O157 and E. coli O26 (12, 24), adhere to the intestinal mucosa with a characteristic "attaching-and-effacing" mechanism (18). Afterwards, they release large amounts of Shiga toxins in the intestinal lumen, which damage villus epithelial cells and are absorbed into the circulation and targeted to the renal endothelium (19). The presence of free Shiga toxins in the intestinal lumen can be detected by either cell toxicity or immunological assays, and such a detection represents a useful tool for laboratory diagnosis of STEC infections (13,24).Shiga toxins, during their journey from gut to renal endothelium, bind to circulating polymorphonuclear leukocytes (PMN) through a low-affinity unknown re...

These observations suggest that the extent of renal damage in children with STEC-associated HUS could depend on the concentration of Stx present on their PMN and presumably delivered by them to the kidney. As previously shown by experimental models from our laboratory, high amounts of Stx could induce a reduced release of cytokines by the renal endothelium, with a consequent lower degree of inflammation. Conversely, low toxin amounts can trigger the cytokine cascade, provoking inflammation, thereby leading to tissue damage.