Adherent/invasive Escherichia coli (AIEC) isolates from asymptomatic people: new E. coli ST131 O25:H4/H30-Rx virotypes

Table 4 Characterization of E. coli ST131 O25:H4/H30-Rx strains with traits of the AIEC pathotype

Strain	Adherence rate^a	Invasion rate^b	Survival within macrophages^c	Biofilm formation rate^d
C7223	60.4 b/c	1.8 × 10²	3.3 × 10²	48.13
C7225	17.3 b/c	1.2 × 10⁸	2.3 × 10⁵	51.44
C7236	18.9 b/c	1.4 × 10⁸	2.0 × 10⁵	46.9
C7230	12.6 b/c	3.2 × 10⁴	4.4 × 10³	46.47

Determination of E. coli strains as belonging to the AIEC pathotype was performed using the following criteria: (1) the ability to adhere to HeLa cells with an adhesion index equal or superior to 1 bacteria per cell (b/c), (2) the ability of the bacteria to invade HeLa cells with an invasion index equal or superior to 0.1% of the original inoculum, (3) the ability to survive and to replicate within J774 macrophages
^aAdherence rate is expressed as the mean of bacteria adhered to one HeLa cell
^bInvasion is the mean CFUs after 1 h rifampicin treatment of infected HeLa cells
^cMean of intracellular bacteria at 3 h post infection relative to the number after 1 h rifampicin treatment, defined as 100% (MOI of 100)
^dBiofilm formation rate is defined as milligrams per grams of total protein

ISSN: 1476-0711