Genotypic and Phenotypic Characterization of Escherichia coli Isolates From Children With Urinary Tract Infection and From Healthy Carriers
ABSTRACT BACKGROUND:: Urinary tract infections (UTI) are common in children and contribute significantly to morbidity and mortality. The major cause is Escherichia coli, carrying multiple virulence-associated factors (VFs). However, the specific traits that distinguish childhood uropathogenic Escherichia coli (UPEC) from fecal commensals of healthy children are incompletely defined. METHODS:: We used a multiplex PCR-based reverse line blot assay, several additional PCRs, and phenotypic methods to compare distributions of virulence traits (22 VF genes; UTI-associated O types; phylogenetic groups; sequence type (ST) 131; and expression of selected VFs), between 212 E. coli isolates from children ≤ 5 years with UTI (109 cystitis; 103 pyelonephritis) and 115 fecal isolates from healthy children of similar age, collected during the same time period. RESULTS:: The studied traits were most prevalent among pyelonephritis, followed closely by cystitis isolates and were uncommon among fecal isolates. Eight VF genes differentiated pyelonephritis from cystitis isolates, but aggregate VF scores in these two UTI groups were similar. Most of the studied phenotypic characteristics showed a similar descending prevalence gradient from pyelonephritis, through cystitis, to fecal isolates. Co-expression of biofilm components, curli and cellulose, was strongly associated with pyelonephritis, phylogenetic group B2, individual VF genes, and higher VF scores. Two-thirds (67%) of clinical isolates belonged to phylogenetic group B2 and, of these, 12% belonged to the ST131 clonal group, compared with 14% and 1%, respectively, of fecal isolates. CONCLUSIONS:: These findings identify specific virulence factors, O types, and a virulent clonal group (ST131), as potential targets for UTI prevention strategies in children.
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ABSTRACT: Uropathogenic E. coli (UPEC) are the major causative agents of urinary tract infection and engage in a coordinated genetic and molecular cascade to colonize the urinary tract. Disrupting the assembly and/or function of virulence factors and bacterial biofilms has emerged as an attractive target for the development of new therapeutic strategies to prevent and treat urinary tract infection, particularly in the era of increasing antibiotic resistance among human pathogens. UPEC vary widely in their genetic and molecular phenotypes and more data are needed to understand the features that distinguish isolates as more or less virulent and as more robust biofilm formers or poor biofilm formers. Curli are extracellular functional amyloid fibers produced by E. coli that contribute to pathogenesis and influence the host response during urinary tract infection (UTI). We have examined the production of curli and curli-associated phenotypes including biofilm formation among a specific panel of human clinical UPEC that has been studied extensively in the mouse model of UTI. Motility, curli production, and curli-associated biofilm formation attached to plastic were the most prevalent behaviors, shared by most clinical isolates. We discuss these results in the context on the previously reported behavior and phenotypes of these isolates in the murine cystitis model in vivo.Biochemical and Biophysical Research Communications 11/2013; 443(2). DOI:10.1016/j.bbrc.2013.11.026 · 2.28 Impact Factor
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ABSTRACT: The recent emergence of multidrug-resistant Escherichia coli sequence type (ST) 131, has coincided with an increase in antibiotic resistance among E. coli generally, suggesting a contributing role for ST131 in resistance. However, there is little information about the contribution of ST131 to different clinical syndromes or the basis for its impressive emergence and epidemic spread. To investigate this, we studied 953 E. coli isolates, from women of reproductive-age in the Central West region of New South Wales, Australia: 623 urinary isolates from patients with cystitis (322) or pyelonephritis (301), and 330 fecal isolates from healthy controls. The characteristics studied included ST131 clonal group status, antibiotic resistance, virulence factor (VF) genes, and biofilm production. As expected, fecal isolates differed significantly from urinary (cystitis and pyelonephritis) isolates for most of the studied characteristics. Antibiotic resistance was significantly more common among ST131 than non-ST131 isolates. Both antibiotic resistance and ST131 were more common among pyelonephritis than cystitis isolates and least so among fecal isolates. Within each source group, individual VF genes were more prevalent, and VF scores higher, for ST131 than non-ST131 isolates. For ST131 only, the prevalence of most individual VF genes, and VF scores increased from lowest among fecal, through cystitis, to pyelonephritis isolates. Biofilm production was strongly associated with ST131 and antibiotic resistance. These results clarify the distribution of the ST131 clonal group, and its epidemiological associations in our region and suggest that it exhibits both enhanced virulence and increased antibiotic resistance, compared with other E. coli UTI and fecal isolates from reproductive-age women.Journal of clinical microbiology 07/2013; 51(10). DOI:10.1128/JCM.01315-13 · 4.23 Impact Factor
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ABSTRACT: Determining the prevalence of children in day-care centres (DCCs) carrying faecal extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and molecularly characterizing those belonging to the Escherichia coli species. Stools were collected from children's diapers (January-April 2012) in randomly chosen DCCs and plated onto ChromID(™) ESBL. Colonies growing on this medium were identified by the Vitek 2(®) system and tested for antibiotic susceptibility and for ESBL production by the double-disc synergy test. ESBL genotypes were determined as well as phylogenetic groups, ERIC-2 (enterobacterial repetitive intergenic consensus) PCR profiles and sequence types (STs) for the E. coli isolates. Serotypes, virotypes, fimH alleles, ESBL-carrying plasmids and PFGE patterns were determined for the ST131 E. coli isolates. Among 419 children from 25 participating DCCs, 1 was colonized by CTX-M-15-producing Klebsiella pneumoniae and 27 (6.4%) by E. coli, which all produced CTX-M enzymes [CTX-M-15 (37%), CTX-M-1 (26%), CTX-M-14 (22%), CTX-M-27 (11%) and CTX-M-22 (4%)]. The 27 E. coli isolates, 55.5% belonging to group B2, displayed 20 ERIC-2 PCR profiles and 16 STs. The ST131 E. coli isolates were dominant (44%), displayed serotypes O25b:H4 and O16:H5, fimH alleles 30 and 41 and virotypes A and C. According to the PFGE patterns, one strain of E. coli ST131 producing a CTX-M-15 enzyme carried by an IncF F2:A1:B- plasmid had spread within one DCC. This study shows a notable prevalence (6.4%) of DCC children with faecal CTX-M-producing E. coli isolates comprising a high proportion of E. coli ST131 isolates, suggesting that these children might be a reservoir of this clone.Journal of Antimicrobial Chemotherapy 01/2014; DOI:10.1093/jac/dkt519 · 5.44 Impact Factor