Prevalence of Motility and Hemolytic Activity in E. coli
The prevalence of motility in clinical E. coli isolates varies significantly by infection type, with higher-motility strains (motility diameter ≥6.6 mm) found in 59% of spontaneous bacterial peritonitis cases, 34% of urosepsis, 32% of colonization, 29% of biliary tract infections, and only 16% of urinary tract infections. 1
Motility Prevalence
The distribution of motile E. coli strains is infection-specific and clinically relevant:
- Spontaneous bacterial peritonitis shows the highest prevalence of higher-motility strains at 59%, significantly exceeding other infection types 1
- Urosepsis demonstrates 34% higher-motility strains 1
- Colonization isolates contain 32% higher-motility strains 1
- Biliary tract infections show 29% higher-motility strains 1
- Urinary tract infections have the lowest prevalence at only 16% higher-motility strains 1
Motility Characteristics by Phylogenetic Group
Higher-motility E. coli strains belong to different phylogenetic groups compared to lower-motility strains, with significantly lower prevalence of phylogenetic groups A and B1 among higher-motility isolates. 1
- Lower-motility strains show higher prevalence of specific virulence factors including afa and ompT genes 1
- Pathogenic E. coli strains employ mechanosensory regulation to conditionally activate flagellar expression under high loads while repressing it in liquid culture 2
- Even traditionally "nonmotile" enteroinvasive E. coli (EIEC) can produce functional flagella with an unusually large 77 kDa flagellin that enables swimming in modified motility agar 3
Regulatory Mechanisms
E. coli maintains approximately 4-5 flagella per cell across diverse growth conditions, representing the minimum number needed to keep the majority of cells motile. 4
- Cells up-regulate motility gene expression at slow growth to compensate for reduced cell size, maintaining consistent flagella numbers per cell 4
- Pathogenic E. coli strains activate flagellar genes upon surface contact or in porous media while repressing them in liquid culture, likely reflecting adaptation to different infection stages 2
Hemolytic Activity Prevalence
The provided evidence does not contain specific prevalence data for hemolytic activity in E. coli clinical isolates. The available studies focus exclusively on motility characteristics, flagellar regulation, and associated virulence factors without addressing hemolytic properties.
Clinical Pitfall
Do not assume that all E. coli isolates traditionally classified as "nonmotile" lack motility capability—EIEC can produce functional flagella under specific conditions 3, which has important implications for epidemiology and infection control.