Escherichia coli O157:H7, other verotoxin-producing E coli and the hemolytic uremic syndrome in childhood

Simulation of Escherichia coli Dynamics in Biofilms and Submerged Colonies with an Individual-Based Model Including Metabolic Network Information

Clustered microbial communities are omnipresent in the food industry, e.g., as colonies of microbial pathogens in/on food media or as biofilms on food processing surfaces. These clustered communities are often characterized by metabolic differentiation among their constituting cells as a result of heterogeneous environmental conditions in the cellular surroundings. This paper focuses on the role of metabolic differentiation due to oxygen gradients in the development of Escherichia coli cell communities, whereby low local oxygen concentrations lead to cellular secretion of weak acid products. For this reason, a metabolic model has been developed for the facultative anaerobe E. coli covering the range of aerobic, microaerobic, and anaerobic environmental conditions. This metabolic model is expressed as a multiparametric programming problem, in which the influence of low extracellular pH values and the presence of undissociated acid cell products in the environment has been taken into account. Furthermore, the developed metabolic model is incorporated in MICRODIMS, an in-house developed individual-based modeling framework to simulate microbial colony and biofilm dynamics. Two case studies have been elaborated using the MICRODIMS simulator: (i) biofilm growth on a substratum surface and (ii) submerged colony growth in a semi-solid mixed food product. In the first case study, the acidification of the biofilm environment and the emergence of typical biofilm morphologies have been observed, such as the mushroom-shaped structure of mature biofilms and the formation of cellular chains at the exterior surface of the biofilm. The simulations show that these morphological phenomena are respectively dependent on the initial affinity of pioneer cells for the substratum surface and the cell detachment process at the outer surface of the biofilm. In the second case study, a no-growth zone emerges in the colony center due to a local decline of the environmental pH. As a result, cellular growth in the submerged colony is limited to the colony periphery, implying a linear increase of the colony radius over time. MICRODIMS has been successfully used to reproduce complex dynamics of clustered microbial communities.

Escherichia coli, cattle and the propagation of disease

Several early models describing host–pathogen interaction have assumed that each individual host has approximately the same likelihood of becoming infected or of infecting others. More recently, a concept that has been increasingly emphasized in many studies is that for many infectious diseases, transmission is not homogeneous but highly skewed at the level of populations. In what became known as the ‘20/80 rule’, about 20% of the hosts in a population were found to contribute to about 80% of the transmission potential. These heterogeneities have been described for the interaction between many microorganisms and their human or animal hosts. Several epidemiological studies have reported transmission heterogeneities for Escherichia coli by cattle, a phenomenon with far-reaching agricultural, medical and public health implications. Focusing on E. coli as a case study, this paper will describe super-spreading and super-shedding by cattle, review the main factors that shape these transmission heterogeneities and examine the interface with human health. Escherichia coli super-shedding and super-spreading by cattle are shaped by microorganism-specific, cattle-specific and environmental factors. Understanding the factors that shape heterogeneities in E. coli dispersion by cattle and the implications for human health represent key components that are critical for targeted infection control initiatives.

Kawasaki Disease Presenting with Bloody Diarrhea and Acute Renal Failure: First Case

Kawasaki disease (KD) is an acute febrile vasculitis of an unknown cause. It affects children <5 year of age, even if cases over 5 years old have been also reported. It is the commonest cause of acquired heart diseases in children which may lead to serious morbidity and mortality. The complications and mortality increase when the diagnosis is delayed. One of the main reasons leading to delayed diagnosis and consequent delayed treatment is the unusual presentation of KD. Its unusual manifestations have been increasingly reported to jeopardize the timely diagnosis and proper treatment. As there is not yet available blood test to diagnose it, low threshold should be taken into account for considering KD, when the clinical criteria are not typical. KD with renal manifestations is infrequently described. We present and discuss a case of an unusual presentation of KD presenting as bloody diarrhea and acute renal failure.

A galactose-binding lectin isolated from Aplysia kurodai (sea hare) eggs inhibits streptolysin-induced hemolysis

A specific galactose-binding lectin was shown to inhibit the hemolytic effect of streptolysin O (SLO), an exotoxin produced by Streptococcus pyogenes. Commercially available lectins that recognize N-acetyllactosamine (ECA), T-antigen (PNA), and Tn-antigen (ABA) agglutinated rabbit erythrocytes, but had no effect on SLO-induced hemolysis. In contrast, SLO-induced hemolysis was inhibited by AKL, a lectin purified from sea hare (Aplysia kurodai) eggs that recognizes α-galactoside oligosaccharides. This inhibitory effect was blocked by the co-presence of d-galactose, which binds to AKL. A possible explanation for these findings is that cholesterol-enriched microdomains containing glycosphingolipids in the erythrocyte membrane become occupied by tightly stacked lectin molecules, blocking the interaction between cholesterol and SLO that would otherwise result in penetration of the membrane. Growth of S. pyogenes was inhibited by lectins from a marine invertebrate (AKL) and a mushroom (ABA), but was promoted by a plant lectin (ECA). Both these inhibitory and promoting effects were blocked by co-presence of galactose in the culture medium. Our findings demonstrate the importance of glycans and lectins in regulating mechanisms of toxicity, creation of pores in the target cell membrane, and bacterial growth.