Identification of Escherichia coli K1 antigen

Detection of K1 antigen of Escherichia coli rods isolated from pregnant women and neonates

The K1 antigen is an important virulence determinant of Escherichia coli strains and has been shown to be associated particularly with neonatal meningitis, bacteraemia and septicaemia. Thus, its detection seems to be useful, especially in the case of E. coli strains isolated from pregnant women and newborns. In this study, the sensitivity and specificity of the latex agglutination test (Pastorex Meningitis) for identification of E. coli serogroup K1 were assessed, using PCR as the gold standard. Our results showed that consistency of results between latex agglutination test and PCR amounted to 98.5 %. Therefore, Pastorex Meningitis is a good alternative to PCR and could be used for rapid K1 antigen detection, especially in local non-specialized laboratories with limited resources where PCR assay is not applied.

Meningitis caused by Escherichia coli producing TEM-52 extended-spectrum beta-lactamase within an extensive outbreak in a neonatal ward: epidemiological investigation and characterization of the strain

Outbreaks caused by Enterobacteriaceae isolates producing extended-spectrum beta-lactamases (ESBL) in neonatal wards can be difficult to control. We report here an extensive outbreak in a neonatal ward with a case of meningitis caused by an ESBL-producing Escherichia coli strain. Between 24 March and 29 April 2009, among the 59 neonates present in the ward, 26 neonates with ESBL-producing E. coli rectal colonization were detected (44%). One of the colonized neonates developed meningitis with a favorable outcome after treatment combining imipenem, gentamicin, and ciprofloxacin. Despite strict intensification of hygiene and isolation procedures for more than 1 month, ward closure to new admissions was necessary to control the outbreak. Randomly amplified polymorphic DNA and pulsed-field gel electrophoresis analysis performed on 31 isolates recovered from 26 neonates and two mother's milk samples showed a clonal strain. ESBL PCR assays indicated that the strain harbored a TEM-52 ESBL encoded by an IncI1 replicon. Phylogenetic analysis by multilocus sequence typing showed that the strain belonged to rare phylogenetic group C, which is closely related to group B1 but appears as group A by the triplex PCR phylogrouping method. The strain harbored the virulence genes fuyA, aer, and iroN and was virulent in a mouse model of septicemia. This work indicates the high potential of colonization, transmission, and virulence of some ESBL-producing E. coli clones.

Vaginal Escherichia coli share common virulence factor profiles, serotypes and phylogeny with other extraintestinal E. coli

Characteristics of Escherichia coli residing in the vagina and their role in extraintestinal infections are largely unknown. In this study, 88 vaginal E. coli (VEC) isolates from Japanese women were characterized by extraintestinal virulence factor (VF) profiling, O:H serotyping and phylogenetic analysis. The prevalence of papC, hlyA, cnfI, PAI, ibeA and K1 antigen among the VEC strains were 45, 22, 19, 78, 32 and 44%, respectively. Phylogenetic analysis identified 76, 16 and 8% of the VEC strains in groups B2, D and A, respectively. The VEC strains were distributed into 31 serotypes, including 8 common serotypes (O1:K1:H1, O1:K1:H7, O2:K1:H7, O4:H5, O6:H1, O18ac:K1:H7, O25:H1 and O75:HNM) that were identified in three or more isolates. Comparative analysis with 61 stool isolates from healthy Japanese men and women, and with data from previous studies, revealed that, although some geographical specificities do exist, the VEC strains shared common VF profiles, O:K:H serotypes and phylogeny with uropathogenic E. coli and E. coli of neonatal septicaemia and meningitis. This study provides additional evidence for a link among extraintestinal E. coli, supporting the concept that the VEC are a reservoir along the 'faecal-vaginal-urinary/neonatal' course of transmission in the extraintestinal E. coli infections.

Phylogenetic analysis and prevalence of urosepsis strains of Escherichia coli bearing pathogenicity island-like domains

We characterized 100 Escherichia coli urosepsis isolates from adult patients according to host compromise status by means of ribotyping, PCR phylogenetic grouping, and PCR detection of papG alleles and the virulence-related genes sfa/foc, fyuA, irp-2, aer, hly, cnf-1 and hra. We also tested these strains for copies of pap and hly and their direct physical linkage with other virulence genes in an attempt to look for pathogenicity islands (PAIs) described for the archetypal uropathogenic strains J96, CFT073, and 536. Most of the isolates belonged to E. coli phylogenetic groups B2 and D and bore papG allele II, aer, and fyuA/irp-2. papG allele II-bearing strains were more common in noncompromised patients, while papG allele-negative strains were significantly more frequent in compromised patients. Fifteen ribotypes were identified. The three archetypal strains harbored different ribotypes, and only one-third of our urosepsis strains were genetically related to one of the archetypal strains. Three and 18 strains harbored three and two copies of pap, respectively, and 5 strains harbored two copies of hly. papGIII was physically linked to hly, cnf-1, and hra (reported to be PAI II(J96)-like genetic elements) in 14% of the strains. The PAI II(J96)-like domain was inserted within pheR tRNA in 11 strains and near leuX tRNA in 3 strains. Moreover, the colocalized genes cnf-1, hra, and hly were physically linked to papGII in four strains and to no pap gene in three strains. papGII and hly (reported to be PAI I(CFT073)-like genetic elements) were physically linked in 16 strains, pointing to a PAI I(CFT073)-like domain. Three strains contained both a PAI II(J96)-like domain and a PAI I(CFTO73)-like domain. Forty-two strains harbored papGII but not hly, in keeping with the presence of a PAI II(CFT073)-like domain. Only one strain harbored a PAI I(536)-like domain (hly only), and none harbored a PAI I(J96)-like domain (papGI plus hly) or a PAI II(536)-like domain (papGIII plus hly). This study provides new data on the prevalence and variability of physical genetic linkage between pap and certain virulence-associated genes that are consistent with their colocalization on archetypal PAIs.

The link between phylogeny and virulence in Escherichia coli extraintestinal infection

Previous studies suggesting a link between Escherichia coli phylogenetic groups and extraintestinal virulence have been hampered by the difficulty in establishing the intrinsic virulence of a bacterial strain. Indeed, unidentified virulence factors do exist, and the susceptibility of the host to infection is highly variable. To overcome these difficulties, we have developed a mouse model of extraintestinal virulence to test the virulence of the strains under normalized conditions. We then assessed the phylogenetic relationships compared to the E. coli reference (ECOR) collection, the presence of several known virulence determinants, and the lethality to mice of 82 human adult E. coli strains isolated from normal feces and during the course of extraintestinal infections. Commensal strains belong mainly to phylogenetic groups A and B1, are devoid of virulence determinants, and do not kill the mice. Strains exhibiting the same characteristics as the commensal strains can be isolated under pathogenic conditions, thus indicating the role of host-dependent factors, such as susceptibility linked to underlying disease, in the development of infection. Some strains of phylogenetic groups A, B1, and D are able to kill the mice, their virulence being most often correlated with the presence of virulence determinants. Lastly, strains of the B2 phylogenetic group represent a divergent lineage of highly virulent strains which kill the mice at high frequency and possess the highest level of virulence determinants. The observed link between virulence and phylogeny could correspond to the necessity of virulence determinants in a genetic background that is adequate for the emergence of a virulent clone, an expression of the interdependency of pathogenicity and metabolic activities in pathogenic bacteria.

Virulence patterns of Escherichia coli K1 strains associated with neonatal meningitis

The prevalence of the ibe10 gene, of the pap, afa, and sfa adhesin-encoding operons, and of a 14.9-kb rrn-containing HindIII fragment was studied for 67 Escherichia coli neonatal meningitis strains, 58 E. coli K1 commensal strains, and 47 E. coli blood isolates from neonates without meningitis. ibe10, sfa, and the 14.9-kb HindIII fragment were observed significantly more often in the meningitis strains than in blood or commensal strains.

In vitro differentiation of E-N-CAM expressing rat neural precursor cells isolated by FACS during prenatal development

Most fetal rat brain cells expressing the embryonal, highly sialylated form of the cell adhesion molecule N-CAM (E-N-CAM) are precursor cells, as judged from the absence of marker molecules specific for mature neural cell types. However, the detection of E-N-CAM+ cells in frozen sections does not provide information on the lineage-specific differentiation of these cells during development. To investigate their differentiation behaviour in vitro, E-N-CAM+ cells were isolated at different times of brain development by fluorescence-activated cell sorting (FACS), using a monoclonal antibody (Mab RB21-7) which specifically recognizes polysialic acid (PSA) residues on E-N-CAM. Double-immunofluorescence analyses showed that the majority of E-N-CAM+ cells isolated on prenatal days 15 to 18 differentiated into neurons while a small subset of Mab RB21-7 binding cells proved to be astrocytic precursors and/or bipotential. The proportion of E-N-CAM+ astrocytic precursors increased during later development (prenatal day 22) concomitantly with the onset of gliogenesis. While conversion of E-N-CAM to mature forms of N-CAM was never observed in neurons during cultivation, E-N-CAM+ cells of the astrocyte lineage switched to N-CAM soon after the onset of GFAP expression. A lineage-specific transition of E-N-CAM to mature N-CAM expression is, therefore, suggested for these astrocytic progenitor cells during rat brain development.

Clonal diversity among strains of Escherichia coli incriminated in turkey colisepticemia

The extent of genetic differentiation among 80 Escherichia coli isolates collected from turkeys with acute colisepticemia was assessed based on allelic variation at 20 enzyme-encoding loci detected by multilocus enzyme electrophoresis. Isolates were polymorphic at 17 loci and were classified into 32 multilocus genotypes, delineating clones, that differed on average at 36% of the loci. In the total sample, 29 (36%) of the isolates belonged to one of two closely related clones, differing only in a single electromorph, and 11 of these isolates were serogroup O78. Most isolates fell into one of 4 genetically distinct clusters of strains. Three of these clusters represent E. coli clone complexes that have been previously identified in avian diseases and a fourth cluster which is specific to colisepticemia in turkeys. Most (73%) isolates produced aerobactin, whereas none produced hemolysins. Assays for detecting K1 capsules, including the use of polyclonal antisera, monoclonal antibodies, and K1-specific bacteriophages, gave variable results, but showed that overall 18% of the strains from colisepticemia were K1 encapsulated with most of the K1+ isolates found in one clone cluster. The results show that many cases of colisepticemia in turkey flocks are caused by a small number of pathogenic clones representing at least three distinct clone complexes.

Molecular epidemiology unravels the complexity of neonatal Escherichia coli acquisition in twins

Combined analysis of restriction fragment length polymorphism of regions of genes coding for rRNA (ribotyping) and esterase electrophoretic typing was used to document neonatal acquisition of Escherichia coli in twins. Our study shows vertical mother-to-infant transmission of one strain of E. coli to one twin and the development of neonatal septicemia with a distinct nonvirulent carboxylesterase type B1 E. coli strain for the other twin.

Virulence factors in Escherichia coli urinary tract infection

Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans.

K1 antigen, serotype and antibiotic susceptibility of Escherichia coli isolated from cerebrospinal fluid, blood and other specimens from Japanese infants

K1 antigens, serotypes and antibiotic susceptibilities of Escherichia coli isolates from neonates and infants were investigated. The presence of K1 antigen was tested by the K1-specific phage method. The number of K1 positive strains was 27 (84%) of 32 isolates from cerebrospinal fluid, 11 (25%) of 44 from blood and 4 (22%) of 18 from other specimens. Fourteen (33%) of the K1 positive strains were serotyped as O16:H6, and 8, 7 and 5 were serotyped as O18ac:H7, O1:H7 and O7:H-, respectively. One of 5 of the K1 negative strains were distributed into 30 different combinations of O and H antigens. The ampicillin resistance rates were 19% in K1 positive strains and 45% in K1 negative ones. The incidence of chloramphenicol resistance was the same in K1 positive and negative strains (21%). Ampicillin resistance was not noted in O16:H6 strains, but the incidence of antibiotic resistance was high (65% to ampicillin and 53% to chloramphenicol) in the rough-type strains.

Embryonic neural cell adhesion molecule in cerebrospinal fluid of younger children: age-dependent decrease during the first year

Poly-alpha-2,8-N-acetylneuraminic acid (poly-alpha-2,8-NeuAc) is developmentally expressed in neural tissue of higher animals, where it is covalently attached to the neural cell adhesion molecule (NCAM), a large integral membrane glycoprotein mediating cell-cell adhesion during neuronal development. NCAM exists in several molecular forms, of which only embryonic NCAM carries lengthy chains (n greater than 5) of poly-alpha-2,8-NeuAc. Chemically identical poly-alpha-2,8-NeuAc of bacterial origin is an important virulence factor in infections caused by Neisseria meningitidis group B and Escherichia coli K1, the predominant pathogens of bacterial meningitis. A quantitative enzyme-linked immunoassay was developed using monoclonal antibody (MAb) 735, an MAb specifically recognizing poly-alpha-2,8-NeuAc, and applied to CSF specimens from younger children. Poly-alpha-2,8-NeuAc contents were within the range of 20-0.2 micrograms/ml, decreasing from day 1 to day 300. Immunoprecipitation, immunoblot with a rabbit anti-mouse NCAM serum recognizing the protein part of human NCAM by cross-reactivity, affinity enrichment using immobilized MAb 735, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that poly-alpha-2,8-NeuAc in CSF is bound to human NCAM, probably NCAM-120.

Common organization of gene clusters for production of different capsular polysaccharides (K antigens) in Escherichia coli

Southern blot analysis of cloned K5- and K7-antigen genes, using DNA fragments from cloned K1 genes as radiolabeled probes, demonstrated that each K-antigen gene cluster is organized in a manner similar to that shown for the K1 antigen. That is, a central DNA segment unique for a given antigen type is flanked by DNA sequences that encode common functions for the management of intracellular polymer. This has been confirmed by transposon and deletion mutagenesis of plasmids carrying the K5 and K7 genes. We also describe a series of complementation experiments in which transport or postpolymerizational modification functions for one K antigen are used to complement mutations in the corresponding regions of a different K-antigen gene cluster. Thus, postpolymerizational modification of polysaccharide and transport of mature polysaccharide from the periplasmic space are common mechanisms and are independent of polysaccharide structure.

DNA probes for K-antigen (capsule) typing of Escherichia coli

DNA restriction fragments derived from the polysaccharide biosynthesis regions of cloned Escherichia coli K1, K5, and K12 capsular antigen genes hybridized only with DNA of strains determined by conventional methods to be of the same K serotype. A probe derived from the common transport region hybridized to all encapsulated E. coli strains.

Serotyping and genotyping of encapsulated Escherichia coli K1 sepsis isolates with a monoclonal IgG anti K1 antibody and K1 gene probes

Among infectious diseases caused by E. coli the capsular type K1 plays a predominant role. E. coli K1 isolates account for 80% of cases of E. coli neonatal meningitis and 30% of E. coli sepsis strains. Serotyping of K1 strains has conventionally relied upon the use of K1-specific bacteriophages or serum agar methods with polyvalent anti K1 serum. In the study present here, 187 E. coli sepsis isolates have been analysed for production of the K1 antigen using K1 phages, K1 serum agar plates and Latex agglutination and ELISA using an IgG2a anti K1 monoclonal antibody. In total, 33 sepsis isolates (about 18%) were identified as K1 positive, with three of these strains proving negative in all tests except those exploiting the monoclonal antibody. That these three strains elaborate the K1 antigen was confirmed by Southern blot experiments using cloned K1 antigen production genes as probes. The failure of the three strains in all the tests except those that use monoclonal antibody could be explained by apparent disruption of K1 gene sequences that encode functions essential for the export of capsular material to the cell surface. The superiority of tests based on monoclonal antibodies above the conventional methods for detection of K1 antigen is evident.