Pathogenicity Island Markers, Virulence Determinants
 malX
 and
 usp
 , and the Capacity of
 Escherichia coli
 To Persist in Infants' Commensal Microbiotas

Östblom, Anna; Adlerberth, Ingegerd; Wold, Agnes E.; Nowrouzian, Forough L.

doi:10.1128/aem.02405-10

Cited by 72 publications

(82 citation statements)

References 50 publications

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“…1). These data support the notion that extraintestinal virulence may be a by-product of commensalism: numerous "extraintestinal virulence genes" (coding for adhesins, iron capture systems, toxins, and protectins) exhibited by phylogroup B2 strains (6,46) may have evolved primarily to allow the bacteria to be good intestinal colonizers (24,28,(47)(48)(49). When phylogroup B2 is dominant, it does not cooccur with the residence of other phylogroup strains, possibly due to higher fitness (50,51).…”

Section: Discussionsupporting

confidence: 65%

Real-Time PCR for Quantitative Analysis of Human Commensal Escherichia coli Populations Reveals a High Frequency of Subdominant Phylogroups

Smati

Clermont

Gal³

et al. 2013

Appl Environ Microbiol

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e Escherichia coli is divided into four main phylogenetic groups, which each exhibit ecological specialization. To understand the population structure of E. coli in its primary habitat, we directly assessed the relative proportions of these phylogroups from the stools of 100 healthy human subjects using a new real-time PCR method, which allows a large number of samples to be studied. The detection threshold for our technique was 0.1% of the E. coli population, i.e., 10 5 CFU/g of feces; in other methods based on individual colony analysis, the threshold is 10%. One, two, three, or four phylogenetic groups were simultaneously found in 21%, 48%, 21%, and 8% of the subjects, respectively. Phylogroups present at a threshold of less than 10% of the population were found in 40% of the subjects, revealing high within-individual diversity. Phylogroups A and B2 were detected in 74% and 70% of the subjects, respectively; phylogroups B1 and D were detected in 36% and 32%, respectively. When phylogroup B2 was dominant, it tended not to cooccur with other phylogroups. In contrast, other phylogroups were present when phylogroup A was dominant. These data indicate a complex pattern of interactions between the members of a single species within the human gut and identify a reservoir of clones that are present at a low frequency. The presence of these minor clones could explain the fluctuation in the composition of the E. coli microbiota within single individuals that may be seen over time. They could also constitute reservoirs of virulent and/or resistant strains. Escherichia coli is the most common commensal aerobic bacterium in the human gut microbiota (1); it is also the Gramnegative bacillus most frequently implicated in human extraintestinal infections (2). This apparent paradox, which characterizes opportunistic pathogens, is classically associated with host deficiencies (for example, as a result of immune-compromising illness, surgery, or catheterization). However, there are still questions concerning the role of the intrinsic properties of the parasite and the conditions that may cause commensal intestinal E. coli strains to become extraintestinal pathogens.Four main phylogenetic groups named A, B1, B2, and D have been distinguished among E. coli strains (3, 4), and distribution within these groups appears to correlate with the origin of the strains. Phylogroup B2 has been shown to include extraintestinal virulent strains (extraintestinal pathogenic E. coli [ExPEC]), which express numerous virulence factors (5, 6), whereas phylogroups A and B1 contain mostly human and animal commensal strains, respectively (7,8,9). However, more recently, an increase in B2 phylogroup strains was observed in human commensal strains originating from industrialized countries (10,11,12,13).Little is known about the diversity, transmission, and persistence of E. coli commensal strains within human populations (1). An individual can be colonized by more than one distinct strain at any given time (14,15,16). However, the few available studies ...

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Section: Discussionsupporting

confidence: 65%

Real-Time PCR for Quantitative Analysis of Human Commensal Escherichia coli Populations Reveals a High Frequency of Subdominant Phylogroups

Smati

Clermont

Gal³

et al. 2013

Appl Environ Microbiol

View full text Add to dashboard Cite

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“…The iut gene was common in 6/7 strains, and was always associated with other VFs. Moreover, the presence of some virulence genes, such as hh/A, cnfl, fimA,fyuA and malX, suggests the presence of PAIs 24 , 26 in all E. coli strains tested, except in one isolate (cat 3). Five CTX-M-type E. coli strains contained class 1 inte-grons; however, the gene cassettes aadA and dfrAl+aadA (conferring resistance to trimethoprim and streptomy-cin-spectinomycin, respectively) were found in only two isolates.…”

Section: Resultsmentioning

confidence: 99%

Genetic and phenotypic characterisation of Escherichia coli producing cefotaximase-type extended-spectrum β-lactamases: first evidence of the ST131 clone in cats with urinary infections in Italy

Nebbia

Tramuta

Odore

et al. 2014

Journal of Feline Medicine and Surgery

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The incidence of cefotaximase (CTX-M)-type extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has increased dramatically in humans and animals since the middle of the last century. E coli that produce CTX-M β-lactamase represent a major cause of urinary tract infections, and pose a significant therapeutic challenge to both human and veterinary medicine. As data on uropathogenic CTX-M-producing strains in cats are limited, the aim of this study was to describe the genetic character and antibiotic resistance phenotypes of CTX-M-producing E coli isolated from cats with cystitis. Seven of 15 E coli bacteria isolated from 138 urine samples had the CTX-M gene and were therefore included in this study. These isolates were screened by polymerase chain reaction for the presence of 14 extra-intestinal virulence factors, class 1 and class 2 integrons, and to identify their phylogenetic groups. Multi-locus sequence typing (MLST) of the strains and susceptibility testing (disc diffusion method) were also performed. Virulence factor iutA was the most frequent determinant identified (86.7%), and the majority of CTX-M-producing strains (n = 5) carried class 1 integrons. MLST allowed us to discriminate four known sequence types (ST131, ST555, ST602, ST155) and three novel sequence types (ST3847, ST3848, ST4181). To the best of our knowledge, this is the first study to report uropathogenic CTX-M-producing E coli ST131 in cats in Italy. Accurate diagnostics and prudent use of antimicrobials are recommended to avoid the spread of multidrug-resistant pathogens in veterinary medicine and to prevent their transmission to humans.

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“…Studies that compared the levels of ExPEC and IPEC VGs in isolates recovered from stool samples of healthy humans found Ͼ31% and Ͻ5% of these isolates to carry ExPEC and IPEC VGs, respectively (10,53). Studies of specific clones showed that dominant or resident clones have more ExPEC VGs than minor or transient ones (54)(55)(56)(57). Finally, a study using E. coli strain 536 (UPEC) in which the seven PAIs had been deleted showed that the wild-type strain had a marked advantage for intestinal colonization in a mouse model, while the PAI-deleted mutant had a competitive advantage in laboratory batch cultures (58).…”

Section: Discussionmentioning

confidence: 99%

Biological and Physicochemical Wastewater Treatment Processes Reduce the Prevalence of Virulent Escherichia coli

Frigon

Biswal

Mazza

et al. 2013

Appl Environ Microbiol

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bEffluents discharged from wastewater treatment plants are possible sources of pathogenic bacteria, including Escherichia coli, in the freshwater environment, and determining the possible selection of pathogens is important. This study evaluated the impact of activated sludge and physicochemical wastewater treatment processes on the prevalence of potentially virulent E. coli. A total of 719 E. coli isolates collected from four municipal plants in Québec before and after treatment were characterized by using a customized DNA microarray to determine the impact of treatment processes on the frequency of specific pathotypes and virulence genes. The percentages of potentially pathogenic E. coli isolates in the plant influents varied between 26 and 51%, and in the effluents, the percentages were 14 to 31%, for a reduction observed at all plants ranging between 14 and 45%. Pathotypes associated with extraintestinal pathogenic E. coli (ExPEC) were the most abundant at three of the four plants and represented 24% of all isolates, while intestinal pathogenic E. coli pathotypes (IPEC) represented 10% of the isolates. At the plant where ExPEC isolates were not the most abundant, a large number of isolates were classified as both ExPEC and IPEC; overall, 6% of the isolates were classified in both groups, with the majority being from the same plant. The reduction of the proportion of pathogenic E. coli could not be explained by the preferential loss of one virulence gene or one type of virulence factor; however, the quinolone resistance gene (qnrS) appears to enhance the loss of virulence genes, suggesting a mechanism involving the loss of pathogenicity islands.

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Pathogenicity Island Markers, Virulence Determinants malX and usp , and the Capacity of Escherichia coli To Persist in Infants' Commensal Microbiotas

Cited by 72 publications

References 50 publications

Real-Time PCR for Quantitative Analysis of Human Commensal Escherichia coli Populations Reveals a High Frequency of Subdominant Phylogroups

Real-Time PCR for Quantitative Analysis of Human Commensal Escherichia coli Populations Reveals a High Frequency of Subdominant Phylogroups

Genetic and phenotypic characterisation of Escherichia coli producing cefotaximase-type extended-spectrum β-lactamases: first evidence of the ST131 clone in cats with urinary infections in Italy

Biological and Physicochemical Wastewater Treatment Processes Reduce the Prevalence of Virulent Escherichia coli

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