Escherichia coli isolates causing bacteremia via gut translocation and urinary tract infection in young infants exhibit different virulence genotypes.

Escherichia coli bacteremia in young infants may arise via either urinary tract infection or gut translocation (GT). E. coli GT isolates have rarely been investigated. Molecular analysis of 100 E. coli isolates recovered from bacteremic infants revealed that GT isolates had multilocus sequence types similar to those of urosepsis isolates but different prevalences of PapGII adhesin, TcpC protectin, and ibeA invasin. Compared with late-onset GT isolates, early-onset isolates were associated with significantly different rates of the conserved virulence plasmidic region common to human and avian pathogenic strains and α-hemolysin. We identified genetic determinants potentially involved in specific pathophysiological steps preceding E. coli bloodstream invasion.

The plasmid of Escherichia coli strain S88 (O45:K1:H7) that causes neonatal meningitis is closely related to avian pathogenic E. coli plasmids and is associated with high-level bacteremia in a neonatal rat meningitis model.

A new Escherichia coli virulent clonal group, O45:K1, belonging to the highly virulent subgroup B2(1) was recently identified in France, where it accounts for one-third of E. coli neonatal meningitis cases. Here we describe the sequence, epidemiology and function of the large plasmid harbored by strain S88, which is representative of the O45:K1 clonal group. Plasmid pS88 is 133,853 bp long and contains 144 protein-coding genes. It harbors three different iron uptake systems (aerobactin, salmochelin, and the sitABCD genes) and other putative virulence genes (iss, etsABC, ompT(P), and hlyF). The pS88 sequence is composed of several gene blocks homologous to avian pathogenic E. coli plasmids pAPEC-O2-ColV and pAPEC-O1-ColBM. PCR amplification of 11 open reading frames scattered throughout the plasmid was used to investigate the distribution of pS88 and showed that a pS88-like plasmid is present in other meningitis clonal groups such as O18:K1, O1:K1, and O83:K1. A pS88-like plasmid was also found in avian pathogenic strains and human urosepsis strains belonging to subgroup B2(1). A variant of S88 cured of its plasmid displayed a marked loss of virulence relative to the wild-type strain in a neonatal rat model, with bacteremia more than 2 log CFU/ml lower. The salmochelin siderophore, a known meningovirulence factor, could not alone explain the plasmid's contribution to virulence, as a salmochelin mutant displayed only a minor fall in bacteremia (0.9 log CFU/ml). Thus, pS88 is a major virulence determinant related to avian pathogenic plasmids that has spread not only through meningitis clonal groups but also human urosepsis and avian pathogenic strains.

Population snapshot of Streptococcus pneumoniae serotype 19A isolates before and after introduction of seven-valent pneumococcal Vaccination for French children.

Serotype 19A Streptococcus pneumoniae strains are now more frequent in French children than before the introduction of a seven-valent conjugate vaccine (PCV7). By applying multilocus sequence typing to 144 serotype 19A isolates collected before and after beginning PCV7 vaccination, we detected clonal expansion of the preexisting penicillin-intermediate sequence type 276.

OXA-48 carbapenemase-producing Klebsiella pneumoniae isolated from Libyan patients.

Six multidrug-resistant Klebsiella pneumoniae isolates were recovered from injured Libyan combatants. Production of carbapenemase was screened by using commercial combination tablets from Rosco combined with a temocillin disk. Polymerase chain reaction (PCR) and sequencing were used to detect several carbapenemase genes and to characterize their genetic environment. Genetic support was studied by mating-out assays. Plasmid size was identified by the KADO method. PCR and sequencing allowed characterization of plasmid scaffold. Genotyping was performed by pulse-field gel electrophoresis (PFGE) and multilocus sequence typing. PCR was used to check for the presence of nine genes linked to virulence in K. pneumoniae. No carbapenemase was identified by Rosco disks, but all isolates showed high-level temocillin resistance. All of them harbored blaOXA-48 in the transposon Tn1999.2, on a self-conjugative plasmid of about 60 kb, similar to pOXA-48. PFGE revealed three clusters in which isolates were genetically related: The first comprised FM9 and FM10, and the second comprised FM1, FM4, and FM5. FM2 formed a third distinct clone. Sequence types ST101, ST11, and ST147 were identified in keeping with PFGE results. The entB, ycfM, ybtS, and mrkD genes were detected in all isolates, and kfu gene was present in the three ST101 strains. This work confirms the current and successful spread of blaOXA-48 by horizontal dissemination of a single IncL/M plasmid through different genetic backbones with strong epidemic potential. It also highlights the need for rapid and reliable phenotypic detection methods. Attempts to link virulence factors and the production of this carbapenemase deserve further studies.

A conserved virulence plasmidic region contributes to the virulence of the multiresistant Escherichia coli meningitis strain S286 belonging to phylogenetic group C.

Recent isolation of the non-K1 Escherichia coli neonatal meningitis strain S286, belonging to phylogroup C, which is closely related to major group B1, and producing an extended-spectrum beta-lactamase, encouraged us to seek the genetic determinants responsible for its virulence. We show that S286 belongs to the sequence O type ST23O78 and harbors 4 large plasmids. The largest one, pS286colV (~120 kb), not related to resistance, contains genes characteristic of a Conserved Virulence Plasmidic (CVP) region initially identified in B2 extra-intestinal avian pathogenic E. coli (APEC) strains and in the B2 neonatal meningitis E. coli strain S88. The sequence of this CVP region has a strong homology (98%) with that of the recently sequenced plasmid pChi7122-1 of the O78 APEC strain Chi7122. A CVP plasmid-cured variant of S286 was less virulent than the wild type strain in a neonatal rat sepsis model with a significant lower level of bacteremia at 24 h (4.1 ± 1.41 versus 2.60 ± 0.16 log CFU/ml, p = 0.001) and mortality. However, the mortality in the model of adult mice was comparable between wild type and variant indicating that pS286colV is not sufficient by itself to fully explain the virulence of S286. Gene expression analysis of pS286colV in iron depleted environment was very close to that of pS88, suggesting that genes of CVP region may be expressed similarly in two very different genetic backgrounds (group C versus group B2). Screening a collection of 178 human A/B1 extraintestinal pathogenic E. coli (ExPEC) strains revealed that the CVP region is highly prevalent (23%) and MLST analysis indicated that these CVP positive strains belong to several clusters and mostly to phylogroup C. The virulence of S286 is explained in part by the presence of CVP region and this region has spread in different clusters of human A/B1 ExPEC, especially in group C.

Evolving microbiology of complicated acute otitis media before and after introduction of the pneumococcal conjugate vaccine in France.

We compare the microbiology of otopathogens causing recurrent acute otitis media (AOM) or AOM treatment failure in 600 children during 2000 to 2008 before and after the introduction of 7-valent pneumococcal conjugate vaccine (PCV-7). Streptococcus pneumoniae predominated before PCV-7 introduction and during 2007 to 2008, whereas Haemophilus influenzae predominated during 2005 to 2006. S. pneumoniae 19A became the most frequent serotype after PCV-7 introduction.

Epidemiology of pediatric community-acquired bloodstream infections in a children hospital in Paris, France, 2001 to 2008.

In 2001 to 2008, we documented 483 cases of pediatric community-acquired bacteremia mostly because of Streptococcus agalactiae (< 4 days), Escherichia coli (4 days to 3 months), pneumococci (3 months to 5 years), and Staphylococcus aureus (> 5 years). Pneumococcal conjugate vaccination affected the serotype distribution of pneumococcal bacteremia but not its frequency. Serotype 19A represented 12% and 22% of pneumococci in the prevaccine and vaccine periods, respectively.

Combined multilocus sequence typing and O serogrouping distinguishes Escherichia coli subtypes associated with infant urosepsis and/or meningitis.

The genetic relatedness of 223 invasive Escherichia coli strains that cause either meningitis or urosepsis without meningitis in young infants was determined by multilocus sequence typing (MLST), ribotyping, and phylogenetic polymerase chain reaction grouping. We also determined the serotypes and virulence genotypes (on the basis of 11 virulence genes). The strains belonged to 29 sequence type complexes (STc), 20 ribotypes, 26 O serogroups, and 39 virulence genotypes. MLST combined with O serogrouping identified 49 subtypes, or "sequence O types." Some sequence O types were almost exclusively associated with either urosepsis (STc27(O2), STc27(O6), and STc29(O2)) or meningitis (STc29(O18)). In contrast, STc29(O45) was equally frequent in these 2 infection sites. Similarly, several virulence genotypes were specifically associated with one of these syndromes. These results point to the existence of specialized invasive subtypes that cause urosepsis or meningitis in infants and identify a new dually virulent invasive clone.

Detection and identification by PCR of a highly virulent phylogenetic subgroup among extraintestinal pathogenic Escherichia coli B2 strains.

Closely related Escherichia coli B2 strains O1:K1, O2:K1, O18:K1, and O45:K1 constitute a major subgroup causing extraintestinal infections. A DNA pathoarray analysis was used to develop a PCR specific for this subgroup that was included in the multiplex phylogenetic-grouping PCR method. Our PCR may serve to identify this virulent subgroup among different ecological niches.

Comparative prevalence of virulence factors in Escherichia coli causing urinary tract infection in male infants with and without bacteremia.

Escherichia coli isolates causing urinary tract infection in 83 male infants younger than 90 days with and without bacteremia were compared for phylogenetic groups and the presence of 10 virulence factors. Our result suggest that the absence of both hemolysin and antigen K1 may be used as a negative predictive factor for bacteremia.