E. coli Bacteremia Strains - High diversity and Associations with Agerelated Clinical Phenomena

Advanced age is associated with an increased proportion of Escherichia coli in bacteremia as well as an increased risk of death from E. coli blood stream infection. Age-associated differences in normal flora E. coli indicate that elderly persons may be diseased by other groups of E. coli than do younger patients. We studied a historical cohort of 212 patients with community-acquired E. coli bacteremia. The bacterial strains were tested for antimicrobial resistance and analyzed by a generic Multi-Locus Variable-Tandem Repeats Analysis (MLVA). The available 212 strains showed a great diversity, and clustered into ten different MLVA-type complexes (MTC). MTC-b, containing 97 of the strains, was associated with ≥1 comorbid illness (OR 2.02, 95% CI 1.12-3.64), and with to ≥1 atypical symptom (OR 0.46, 95% CI 0.27-0.80). MTC-c, containing 31 strains, was associated with urinary origin of infection (OR 3.28, 95% CI 1.345-8.00) and was preventive against gastrointestinal origin of infection (OR 0.11, 95% CI 0.01-0.83). MTC-g, containing only eight strains, was associated with leukopenia (OR 6.43, 95% CI 1.15-36.00). The strains showed low level of antimicrobial resistance. Fifteen of the 212 patients (7.1%) died within 14 days after admission to hospital. Neither MTC nor antimicrobial resistance was associated with hospital mortality. In conclusion, our study showed a great degree of diversity of the strains and that one of the MTCs was associated with age-related clinical phenomena. None of the MTCs were associated with outcome, indicating that patient characteristics are more important than microbial characteristics.