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: We investigated the molecular types of uropathogenic Escherichia coli (UPEC) by using conventional phylogrouping, multilocus sequence typing (MLST), and fimH genotyping. Samples of patients younger than 18 years of age were collected from the Chung-Ang University Hospital over 2 years. Conventional phylogenetic grouping for UPEC strains was performed by polymerase chain reaction (PCR). Bacterial strain sequence types (STs) were classified on the basis of the results of partial sequencing of seven housekeeping genes. In addition, we analyzed nucleotide variations in a 424-base pair fragment of fimH, a major virulence factor in UPEC. Sixty-four UPEC isolates were analyzed in this study. Phylogenetic grouping revealed that group B2 was the most common type (n=54, 84%). We identified 16 distinctive STs using MLST. The most common STs were ST95 (35.9%), ST73 (15.6%), ST131 (12.5%), ST69 (7.8%), and ST14 (6.3%). Fourteen fimH allele types were identified, of which 11 had been previously reported, and the remaining three were identified in this study. f1 (n=28, 45.2%) was found to be the most common allele type, followed by f6 and f9 (n=7, 11.3% each). Comparative analysis of the results from the three different molecular typing techniques revealed that both MLST and fimH typing generated more discriminatory UPEC types than did PCR-based phylogrouping. We characterized UPEC molecular types isolated from Korean children by MLST and fimH genotyping. fimH genotyping might serve as a useful molecular test for large epidemiologic studies of UPEC isolates.Korean Journal of Pediatrics 01/2015; 58(1):20.
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ABSTRACT: To identify possible explanations for the recent global emergence of Escherichia coli sequence type (ST) ST131 we analyzed temporal trends within ST131 O25 for antimicrobial resistance, virulence genes, biofilm formation, and the H30 and H30-Rx subclones. For this, we surveyed the WHO E. coli and Klebsiella Centre's E. coli collection (1957-2011) for ST131 isolates, characterized them extensively, and assessed for temporal trends. Overall, antimicrobial resistance increased temporally in prevalence and extent, due mainly to the recent appearance of the H30 (1997) and H30-Rx (2005) ST131 subclones. In contrast, neither total virulence gene content nor prevalence of biofilm production increased temporally, although non-H30 isolates increasingly qualified as extraintestinal pathogenic E. coli (ExPEC). Whereas virotype D occurred from 1968 forward, virotypes A and C occurred only after 2000 and 2002, respectively, associated with the H30 and H30-Rx subclones, which were characterized by multidrug resistance (including extended-spectrum beta-lactamase [ESBL] production: H30-Rx) and absence of biofilm production. Capsular antigen K100 occurred exclusively among H30-Rx isolates (55% prevalence). Pulsotypes corresponded broadly with subclones and virotypes. Thus, ST131 should be regarded not as a unitary entity but as a group of distinctive subclones, with its increasing antimicrobial resistance having a strong clonal basis, i.e., emergence of the H30 and H30-Rx ST131 subclones, rather than acquisition of resistance by diverse ST131 strains. Distinctive characteristics of the H30-Rx subclone - including specific virulence genes (iutA, afa/dra, kpsII), the K100 capsule, multidrug resistance, and ESBL production - possibly contributed to epidemiologic success, and some (e.g., K100) might serve as vaccine targets.Antimicrobial Agents and Chemotherapy 09/2014; · 4.45 Impact Factor
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ABSTRACT: In 2008, a previously unknown Escherichia coli clonal group, sequence type 131 (ST131), was identified on three continents. Today, ST131 is the predominant E. coli lineage among extraintestinal pathogenic E. coli (ExPEC) isolates worldwide. Retrospective studies have suggested that it may originally have risen to prominence as early as 2003. Unlike other classical group B2 ExPEC isolates, ST131 isolates are commonly reported to produce extended-spectrum β-lactamases, such as CTX-M-15, and almost all are resistant to fluoroquinolones. Moreover, ST131 E. coli isolates are considered to be truly pathogenic, due to the spectrum of infections they cause in both community and hospital settings and the large number of virulence-associated genes they contain. ST131 isolates therefore seem to contradict the widely held view that high levels of antimicrobial resistance are necessarily associated with a fitness cost leading to a decrease in pathogenesis. Six years after the first description of E. coli ST131, this review outlines the principal traits of ST131 clonal group isolates, based on the growing body of published data, and highlights what is currently known and what we need to find out to provide public health authorities with better information to help combat ST131.Clinical Microbiology Reviews 07/2014; 27(3):543-574. · 16.00 Impact Factor