Comparative distribution of phylogenetic groups, virulence genes and antimicrobial resistance in Escherichia coli isolated from blood, urine and faeces

Abstract number: P1822

Lee S., Yu J.K., Park K., Oh E.J., Kim S.Y., Park Y.J.

Objectives: We compared the distribution of phyolgenetic groups and virulence genes of Escherichia coli between pathogenic strains (from blood and urine) and commensal strains (from faeces), and antimicrobial resistance of E. coli isolated from blood and urine.

Methods: A total of 550 non-duplicate E. coli isolates (145 from blood, 200 from urine, and 205 from faecal specimens of healthy humans) were consecutively obtained. PCR experiments for phylogenetic groups (A, B1, B2, D) and nine virulence genes (sfsS, fogG, hlyA, cnf1, iutA, fyuA, iroN, traT, PAI) were performed by using published primers for all isolates. Antimicrobial susceptibility tests for ampicillin, piperacillin, amoxicillin/clavulanic acid, piperacillin/tazobactam, cefazolin, cefoxitin, cefotaxim, ceftazidime, cefepime, amikacin, gentamicin, tobramycin, tetracycline, ciprofloxacin, trimethoprim/sulfamethoxazole, imipenem were determined by VITEK 2 automated system (bioM?ieux, VITEK) and ESBL confirmatory test was performed according to the CLSI guideline for 345 E. coli isolates from blood and urine. Statistical analyses were performed by using chi-square tests. A P value of <0.05 was considered statistically significant.

Results: The phylogenetic distribution showed similar pattern between E. coli from blood and urine (B2 (44.8%, 58.5%, respectively) > D (29.0%, 23.0%, respectively) > A(18.6%, 9.5%, respectively) > B1 (7.6% and 9.0%, respectively). However, isolates from faeces revealed different distribution (A (38.0%) > B2 (22.9%) > D (21.0%) > B1 (18.0%).

Out of the nine virulence genes, the prevalence of all but sfaS were significantly higher in pathogenic strains than in commensal strains, and that of PAI, fyuA and traT were significantly higher in E. coli from blood than isolates from urine.

The antimicrobial resistance rate showed no significant difference between in E. coli from blood and E. coli from urine, but in phylogenetic group B2, the prevalence of ESBL (18.5% vs 6.0%) was significantly higher in E. coli from blood than in E. coli from urine.

Conclusion: Most (78.3%) of pathogenic E. coli strains belonged to the phylogenetic groups B2 or D. Unexpectedly, as many as 43.9% of commensal strains belonged to group B2 and D.

The finding that the prevalence of PAI, fyuA and traT were significantly higher in E. coli from blood than E. coli from urine suggests the presence of these virulence factors indicate higher risk of bacteraemia.