TABLE 1.

Prevalence of capsular (K) antigens according to clonal subset among 128 archival ST131 Escherichia coli isolates (1968 to 2011)

K antigen(s)	No. (column %) of isolates harboring K antigens				P valuea
	Total (n = 128)	Non-H30 (n = 62)	H30 (non-Rx) (n = 17)	H30-Rx (n = 49)	Non-H30 vs H30 (non-Rx)	Non-H30 vs H30-Rx	H30 (non-Rx) vs H30-Rx
K2	22 (17)	14 (23)	0 (0)	8 (16)	0.03
K4	1 (1)	1 (2)	0 (0)	0 (0)
K5	10 (8)	1 (2)	6 (35)	3 (6)	<0.001
K12	1 (1)	1 (2)	0 (0)	0 (0)
K13	2 (2)	2 (3)	0 (0)	0 (0)
K14	2 (2)	2 (3)	0 (0)	0 (0)
K16	14 (11)	14 (23)	0 (0)	0 (0)	0.03	<0.001
K20	2 (2)	0 (0)	1 (6)	1 (2)
K20, K23	1 (1)	0 (0)	0 (0)	1 (2)
K22	1 (1)	0 (0)	0 (0)	1 (2)
K97	1 (1)	1 (2)	0 (0)	0 (0)
K98	1 (1)	0 (0)	0 (0)	1 (2)
K100	27 (21)	0 (0)	0 (0)	27 (55)		<0.001	<0.001
K+b	28 (22)	20 (32)	5 (29)	3 (6)		<0.001	0.022
K−c	15 (12)	6 (10)	5 (29)	4 (8)			0.042

^aP values, by Fisher's (2-tailed) exact test, are shown where P < 0.05.

^bCapsular antigen of unknown type present.

^cNo capsular antigen present.