Phenotypic microarrays suggest Escherichia coli ST131 is not a metabolically distinct lineage of extra-intestinal pathogenic E. coli

Extraintestinal pathogenic E. coli (ExPEC) are the major aetiological agent of urinary tract infections (UTIs) in humans. The emergence of the CTX-M producing clone E. coli ST131 represents a major challenge to public health worldwide. A recent study on the metabolic potential of E. coli isolates demonstrated an association between the E. coli ST131 clone and enhanced utilisation of a panel of metabolic substrates. The studies presented here investigated the metabolic potential of ST131 and other major ExPEC ST isolates using 120 API test reagents and found that ST131 isolates demonstrated a lower metabolic activity for 5 of 120 biochemical tests in comparison to non-ST131 ExPEC isolates. Furthermore, comparative phenotypic microarray analysis showed a lack of specific metabolic profile for ST131 isolates countering the suggestion that these bacteria are metabolically fitter and therefore more successful human pathogens

Genome Sequence of AvianEscherichia coliStrain IHIT25637, an Extraintestinal PathogenicE. coliStrain of ST131 Encoding Colistin Resistance Determinant MCR-1

Sequence type 131 (ST131) is one of the predominant Escherichia coli lineages among extraintestinal pathogenic E. coli (ExPEC) that causes a variety of diseases in humans and animals and frequently shows multidrug resistance. Here, we report the first genome sequence of an ST131-ExPEC strain from poultry carrying the plasmid-encoded colistin resistance gene mcr-1

Comparative Genomics of Escherichia coli Isolated from Skin and Soft Tissue and Other Extraintestinal Infections

Escherichia coli, an intestinal Gram-negative bacterium, has been shown to be associated with a variety of diseases in addition to intestinal infections, such as urinary tract infections (UTIs), meningitis in neonates, septicemia, skin and soft tissue infections (SSTIs), and colisepticemia. Thus, for nonintestinal infections, it is categorized as extraintestinal pathogenic E. coli (ExPEC). It is also an opportunistic pathogen, causing cross infections, notably as an agent of zoonotic diseases. However, comparative genomic data providing functional and genetic coordinates for ExPEC strains associated with these different types of infections have not proven conclusive. In the study reported here, ExPEC E. coli isolated from SSTIs was characterized, including virulence and drug resistance profiles, and compared with isolates from patients suffering either pyelonephritis or septicemia. Results revealed that the majority of the isolates belonged to two pathogenic phylogroups, B2 and D. Approximately 67% of the isolates were multidrug resistant (MDR), with 85% producing extended-spectrum beta-lactamase (ESBL) and 6% producing metallo- beta-lactamase (MBL). The blaCTX-M-15 genotype was observed in at least 70% of the E. coli isolates in each category, conferring resistance to an extended range of beta-lactam antibiotics. Whole-genome sequencing and comparative genomics of the ExPEC isolates revealed that two of the four isolates from SSTIs, NA633 and NA643, belong to pandemic sequence type ST131, whereas functional characteristics of three of the ExPEC pathotypes revealed that they had equal capabilities to form biofilm and were resistant to human serum. Overall, the isolates from a variety of ExPEC infections demonstrated similar resistomes and virulomes and did not display any disease-specific functional or genetic coordinates. IMPORTANCE Infections caused by extraintestinal pathogenic E. coli (ExPEC) are of global concern as they result in significant costs to health care facilities management. The recent emergence of a multidrug-resistant pandemic clone, Escherichia coli ST131, is of primary concern as a global threat. In developing countries, such as India, skin and soft tissue infections (SSTIs) associated with E. coli are marginally addressed. In this study, we employed both genomic analysis and phenotypic assays to determine relationships, if any, among the ExPEC pathotypes. Similarity between antibiotic resistance and virulence profiles was observed, ST131 isolates from SSTIs were reported, and genomic similarities among strains isolated from different disease conditions were detected. This study provides functional molecular infection epidemiology insight into SSTI- associated E. coli compared with ExPEC pathotypes

Distances in random graphs with finite variance degrees

In this paper we study a random graph with $N$ nodes, where node $j$ has degree $D_j$ and $\{D_j\}_{j=1}^N$ are i.i.d. with \prob(D_j\leq x)=F(x). We assume that $1-F(x)\leq c x^{-\tau+1}$ for some $\tau>3$ and some constant $c>0$. This graph model is a variant of the so-called configuration model, and includes heavy tail degrees with finite variance. The minimal number of edges between two arbitrary connected nodes, also known as the graph distance or the hopcount, is investigated when $N\to \infty$. We prove that the graph distance grows like $\log_{\nu}N$, when the base of the logarithm equals \nu=\expec[D_j(D_j -1)]/\expec[D_j]>1. This confirms the heuristic argument of Newman, Strogatz and Watts \cite{NSW00}. In addition, the random fluctuations around this asymptotic mean $\log_{\nu}{N}$ are characterized and shown to be uniformly bounded. In particular, we show convergence in distribution of the centered graph distance along exponentially growing subsequences.Comment: 40 pages, 2 figure

Neumonía necrotizante inducida por Escherichia coli extraintestinal patogénica (ExPEC) en felinos

La Escherichia coli extraintestinal patogénica (ExPEC) es una de las bacterias más comunes encontradas enel tracto gastrointestinal de humanos y animales. ExPEC se caracteriza por producir enfermedad en otrosórganos fuera del tracto gastrointestinal. Este grupo ha sido implicado en infecciones del tracto urinario,meningitis, septicemia y neumonía en humanos y animales. En este estudio se muestran las implicancias dedistintas ExPEC en el desarrollo de neumonía en un refugio para gatos, en donde mueren de manera abrupta13 de 35 gatos; y en un tigre recientemente destetado y transportado en una caja para un programa detelevisión. En todos los casos, se observa neumonía necrotizante y fibrinosa, con la presencia de coloniasbacterianas intralesionales. El cultivo y la tipificación de los genotipos de virulencia demuestran la presenciade factores que son comunes para estas bacterias, como son hemolisina D, papGI y papGIII y cnf-1. Comopatogenia, se propone que una vez inhalada la bacteria, la presencia de hemolisina y cnf-1 reduce larespuesta inflamatoria aguda en pulmón, bloqueando la llegada e induciendo muerte de neutrófilos,disparando además edema, necrosis e inflamación. Interesantemente, hemolisinas y cnf-1 son encontrados enExPEC aisladas de humanos que padecen infecciones del tracto urinario y otros sitios extraintestinales. Enconclusión, Las infecciones por ExPEC en felinos es una entidad emergente, que se caracteriza por eldesarrollo de neumonía necrotizante que es frecuentemente fatal, y que este agente tiene un potencialzoonótico debido a su similitud entre las bacterias aisladas en humanos y animales, sumado a la cercaníaentre ambas especies.  

Detection of cytotoxic necrotizing factor types 1 and 2 among fecal Escherichia coli isolates from brazilian children with and without diarrhea

The enteropathogenic role of cytotoxic necrotizing factor (CNF)-producing Escherichia coli was investigated by searching cnf genes among 2074 isolates from 200 children with and 200 without acute diarrhea in Brazil. Fourteen (7%) cases versus 10 (5%) control children carried at least one cnf positive isolate (P = 0.50) and most isolates expressed CNF type 1. DNA sequences of virulence factors of extraintestinal pathogenic E. coli (ExPEC) were detected in 78.6% of CNF1-producing isolates. Besides not being associated with human acute diarrhea, the CNF1-producing isolates here identified may represent potential ExPEC transitorily composing the normal intestinal flora.Instituto Adolfo Lutz Seção de BacteriologiaUniversidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM) Departamento de Microbiologia, Imunologia e ParasitologiaUNIFESP, EPM, Depto. de Microbiologia, Imunologia e ParasitologiaSciEL

Mean-Variance Cointegration and the Expectations Hypothesis

The present paper sheds further light on a well-known (alleged) violation of the expec- tations hypothesis of the term structure (EHT) - the frequent finding of unit roots in interest rate spreads. We show that the EHT implies (i) that the nonstationarity stems from the holding premium, which is hence (ii) cointegrated with the spread. In a stochas- tic discount factor framework we model the premium as being driven by the integrated variance of excess returns. Introducing the concept of mean-variance cointegration we actually find cointegration relations between spreads and premia in US data.Expectations Hypothesis, Holding Premium, Persistence, Cointegration, GARCH

Assessing the diversity of the virulence potential of Escherichia coli isolated from bacteremia in São Paulo, Brazil

Most of the knowledge of the virulence determinants of extraintestinal pathogenic Escherichia coli (ExPEC) comes from studies with human strains causing urinary tract infections and neonatal meningitis and animal strains causing avian colibacillosis. In this research, we analyzed the phylogenetic background, the presence of 20 ExPEC virulence factors, and the intrinsic virulence potential of 74 E. coli strains isolated in São Paulo, Brazil, from 74 hospitalized patients (43 males and 31 females) with unknown-source bacteremia. Unlike other places in the world, the bacteremic strains originated equally from phylogroups B2 (35%) and D (30%). A great variability in the profiles of virulence factors was noted in this survey. Nevertheless, 61% of the strains were classified as ExPEC, meaning that they possessed intrinsic virulent potential. Accordingly, these strains presented high virulence factor scores (average of 8.7), and were positively associated with 12 of 17 virulence factors detected. On the contrary, the non-ExPEC strains, isolated from 39% of the patients, presented a generally low virulence capacity (medium virulence factor score of 3.1), and were positively associated with only the colicin cvaC gene. These results show the importance of discriminating E. coli isolates that possess characteristics of true pathogens from those that may be merely opportunistic in order to better understand the virulence mechanisms involved in extraintestinal E. coli infections. Such knowledge is essential for epidemiological purposes as well as for development of control measures aimed to minimize the incidence of these life-threatening and costly infections.Universidade Federal de São Paulo (UNIFESP) Imunologia e Parasitologia Departamento de MicrobiologiaUniversidade Federal de São Paulo (UNIFESP) Departamento de Medicina Laboratorio Especial de Microbiologia ClinicaUNIFESP, Imunologia e Parasitologia Depto. de MicrobiologiaUNIFESP, Depto. de Medicina Laboratorio Especial de Microbiologia ClinicaSciEL

Human extraintestinal pathogenic Escherichia coli strains differ in prevalence of virulence factors, phylogroups, and bacteriocin determinants

Table S4. Differences in the distribution of virulence factors, E. coli phylogroups, bacteriocin production, and bacteriocin determinants between subgroups of ExPEC strains and fecal strains. (XLSX 14 kb