E. coli

Introduction

E.coli are extremely common bowel flora bacteria and commonly are a cause of urinary tract infections (UTIs) / cystitis and urosepsis
- a US 2025 study ¹⁾ suggests that ~20% of UTIs are caused by extraintestinal pathogenic E.coli strains (ExPEC) spread from contaminated meats, especially poultry
they sometimes can cause invasive disease such as meningitis, especially in infants
although E. coli is commonly found in a variety of extraintestinal infections, it doesn’t have a substantial array of virulence factors that might account for its invasive and persistence characteristics
in many infectious scenarios it enters the body and persists through stealth
this “invasiveness” seems mainly due to the presence of a K1 capsule that surrounds the bacteria and which evades immune systems by mimicking natural antigens in the body
pathogenic E.coli spread by fecal-oral route can cause “silent” pandemics as have occurred such as:
- clade ST131-B expanded in the 1990s
- clades ST131-A, ST131-C1 and ST131-C2
  - these clones likely expanded in parallel in the host population around early 2000s
  - estimated R0 for each of these is 1.47, 1.18 and 1.13 respectively, with C1 and C2 being more antibiotic resistant and more an issue in hospitalized or frail residential care patients ²⁾

the capsule genes have been acquired over and over again by many different lineages of this pathogen species over the centuries
25% of all current E. coli strains responsible for blood infections contain the genetic information needed to develop the K1 capsule ³⁾

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