Why the discovery of adherent-invasive Escherichia coli molecular markers is so challenging?

Table 1 Phenotype, phylogroup and prevalence of virulence genes found to be more frequent in adherent-invasive Escherichia coli than non-adherent-invasive Escherichia coli strains in PCR-based and genomic studies

Virulence gene	Group of study (n)		Phylogroup (n)1					Prevalence (%)
	AIEC	non-AIEC	A	B1	B2	D	Others	AIEC	non-AIEC
malX[37]	49	1342	39	19	98	19	8	71	47
kpsMTII[37]	49	1342	39	19	98	19	8	71	52
pduC[31]	24	25	14	16	10	9	0	50	20
lpfA[31]	24	25	14	16	10	9	0	71	20
lpfA + gipA[39]	35	103	Undetermined					31	0
chuA[13]	15	37	11	5	18	18	0	93	59
ibeA[40]	19	57	Undetermined					37	3
colV[40]	19	57	Undetermined					42	16
vat[38]	22	37	9	8	29	12	1	59	30
pic[38]	22	37	9	8	29	12	1	41	16
papGII/III[38]	22	37	9	8	29	12	1	18	0
iss[38]	22	37	9	8	29	12	1	32	11

¹Based on house-keeping genes identified by triplex PCR[41] or by structure analysis included in the multilocus sequence typing analyses[42].

²Nineteen intestinal pathogenic Escherichia coli strains and 78 ExPEC strains isolated from animals and 37 human mucosal-associated non-AIEC strains. AIEC: Adherent-invasive Escherichia coli.