“The clone Escherichia coli O25 ST131, typically producing extended-spectrum beta-lactamases (ESBLs), has spread globally and became the dominant type among extraintestinal isolates at many parts of the world. However, the reasons behind the emergence and success of this clone are only partially understood. We compared the core
type genes by PCR of ESBL-producing and ESBL-nonproducing strains isolated from urinary tract infections in the United Arab Emirates and found a surprisingly high frequency of the K-12 core type (44.6%) among members of the former group, while in the latter one, it was as low (3.7%), as reported earlier. The high figure was almost entirely attributable to the presence of members of the clone O25 ST131 among ESBL producers. Strains from Bleomycin the same clone isolated in Europe also carried the K-12 core type genes. Sequencing selleck chemical the entire core operon of an O25 ST131 isolate revealed a high level of similarity to known K-12 core gene sequences and an almost complete identity with a recently sequenced
non-O25 ST131 fecal isolate. The exact chemical structure and whether and how this unusual core type contributed to the sudden emergence of ST131 require further investigations. In Escherichia coli, the core oligosaccharide (OS) part of the lipopolysaccharide (LPS) molecule occurs in five different types: R1–4 and K-12, respectively
(Muller-Loennies et al., 2007). The core has a crucial role in maintaining the structure of the cell wall, although to what extent and how its specific type affects the colonizing capacity or the virulence of a pathogen remains to be elucidated. Nevertheless, earlier studies consistently found a highly disproportional distribution of these core types among commensal and clinical E. coli isolates (Gibb et al., 1992; Appelmelk et al., 1994; Amor et al., Vitamin B12 2000; Gibbs et al., 2004). Among strains recovered from extraintestinal infections, the frequency of R1 core type reached 61.0–81.0%, while that of the K-12 type was found the least or the second least common (2.2–5.6%) (Gibb et al., 1992; Appelmelk et al., 1994; Amor et al., 2000). These frequencies were well reflected by the distribution of core-type-specific antibodies in the population (Gibbs et al., 2004). In the past decade, the spread of extended-spectrum beta-lactamase (ESBL)-producing E. coli strains considerably altered the epidemiology and treatment options of extraintestinal infections (Woodford et al., 2011; Van der Bij et al., 2012). A significant percentage of these isolates belong to a limited number of clones, some considerably differing in their panel of virulence factors from those described earlier (Totsika et al., 2011; Van der Bij et al., 2012).