Phylogenetic backgrounds and virulence profiles of atypical enteropathogenic Escherichia coli strains from a case-control study using multilocus sequence typing and DNA microarray analysis.
Atypical enteropathogenetic Escherichia coli (EPEC) strains are frequently detected in children with diarrhea but are also a common finding in healthy children. The aim of this study was to compare the phylogenetic ancestry and virulence characteristics of atypical (eae positive, stx and bfpA negative) EPEC strains from Norwegian children with (n = 37) or without (n = 19) diarrhea and to search for an association between phylogenetic ancestry and diarrhea. The strains were classified in phylogenetic groups by phylogenetic marker genes and in sequence types (STs) by multilocus sequence typing. Phylogenetic ancestry was compared to virulence characteristics based on DNA microarray analysis. Serotyping and pulsed-field gel electrophoresis (PFGE) were also performed. All four phylogenetic groups, 26 different STs, and 20 different clonal groups were represented among the 56 atypical EPEC strains. The strains were separated into three clusters by overall virulence gene profile; one large cluster with A, B1, and D strains and two clusters with group B2 strains. There was considerable heterogeneity in the PFGE profiles and serotypes, and almost half of the strains were O nontypeable. The efa1/lifA gene, previously shown to be statistically linked with diarrhea in this strain collection (J. E. Afset et al., J. Clin. Microbiol. 44:3703-3711, 2006), was present in 8 of 26 STs. The two phylogenetic groups B1 and D were weakly associated with diarrhea (P = 0.06 and P = 0.09, respectively). In contrast, group B2 was isolated most frequently from healthy controls (P = 0.05). In conclusion, the atypical EPEC strains were heterogeneous both phylogenetically and by virulence profile. Phylogenetic ancestry was less useful as a predictor of diarrhea than were specific virulence genes.
Afset
Jan Egil
JE
Department of Medical Microbiology, Children's and Women's Health, St Olavs University Hospital, Trondheim, Norway. jan.afset@ntnu.no
Anderssen
Endre
E
Bruant
Guillaume
G
Harel
Josée
J
Wieler
Lothar
L
Bergh
Kåre
K
D018829:Adhesins, Bacterial / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D016022:Case-Control Studies; D002675:Child, Preschool; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics*; D003967:Diarrhea / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D054308:Enteropathogenic Escherichia coli / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D036781:Fimbriae Proteins / Q000235:genetics; D005838:Genotype; D006801:Humans; D046228:Microarray Analysis; D009664:Norway; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012703:Serotyping; D022603:Shiga Toxins / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics*
D018829:Adhesins, Bacterial; D001427:Bacterial Toxins; C104901:BfpA protein, E coli; D004269:DNA, Bacterial; C404907:Efa1 protein, E coli; D029968:Escherichia coli Proteins; D022603:Shiga Toxins; D037521:Virulence Factors; C406587:lymphostatin protein, E coli; C073819:eaeA protein, E coli; D036781:Fimbriae Proteins