Abstract
BackgroundThe Escherichia coli sequence type 131 (ST131) is a well established clone causing significant extraintestinal infections worldwide. However, no studies have been reported the phenotypic and molecular traits of ST131 isolates in comparison to other clones of E. coli from Iran. So, we determined the differences between 69 ST131 strains collected during a one year surveillance study and 84 non-ST131 isolates, including 56 clinical fluoroquinolone resistant and 28 broiler colibacillosis isolates in terms of clonality and genetic background.ResultsST131 isolates were associated with phylogroup B2 (68 out of 69 isolates, 98.4%), while clinical non-ST131 and fluoroquinolone resistant broiler isolates mainly belonged to phylogroup A. The highest virulence score was observed in ST131 clone, while they showed less diversity in virulence profiles than other clinical isolates. Almost all of the ST131 isolates (95.6%) were ExPEC and had the highest virulence scores, but their resistance scores were less than clinical non-ST131 isolates. Broiler isolates showed higher prevalence of ExPEC-associated virulence genes and CTX-M-G1/G9 resistance determinants as compared to clinical non-ST131 isolates. While blaOXA-48/NDM carbapenemases were mostly found in ST131 clone, resistance rate against ertapenem was higher among clinical non-ST131 strains. According to ERIC-based fingerprinting, the ST131 strains were more genetically similar, followed by non-ST131 and broiler isolates.ConclusionsST131 isolates possess the ability to make a balance between clonality and extent of resistance/virulence genes content, so this phenomenon gives a fitness advantage over other E. coli clones. The broilers E. coli population poses a potential zoonotic risk which could be transmitted to the community through the food chain. A number of factors are involved in the dissemination of and infections due to ST131 clone.
Highlights
The Escherichia coli sequence type 131 (ST131) is a well established clone causing significant extraintestinal infections worldwide
Human-sourced E. coli isolates Sixty-nine strains out of 338 collected human E. coli isolates belonged to ST131 clonal group
The prevalence of ST131 and clinical non-ST131 isolates were higher among women, sex distribution did not vary significantly between two groups of clinical isolates
Summary
The Escherichia coli sequence type 131 (ST131) is a well established clone causing significant extraintestinal infections worldwide. Extraintestinal infections caused by Escherichia coli, including urinary tract infections, bloodstream infections and neonatal meningitis are common, costly and are major causes of morbidity and mortality. It has been hypothesized that avian E. coli isolates are reservoirs of virulence and resistance determinants, and strains harboring these elements may be able to cause foodborne diseases in humans. Characterization of overlapping traits between avian pathogenic E. coli (APEC) and urinary pathogenic E. coli (UPEC), such as O-serogroups, virulence markers and assignments to phylogroups, encouraged this hypothesis and subsequent researches comparing APEC and human E. coli isolates including UPEC, neonatal meningitis E. coli (NMEC) and E. coli causing septicemia showed common molecular traits between human and avian strains [4, 6, 7]. Vincent et al had identified E. coli ST131 from retail chicken samples in Canada but at a significant lower prevalence (0.4%) than in Spain [11]
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