Table 2

Characteristics of 351 extended-spectrum-β-lactamase-producing Escherichia coli clinical isolates from the United States, 2000 to 2009

CharacteristicaNo. (%) of isolatesbP valuec
Total (n = 351)Subset
ST131 M15 (group 1; n = 98)ST131 M15+ (group 2; n = 89)ST131+ M15 (group 3; n = 52)ST131+ M15+ (group 4; n = 113)Group 1 vs 2Group 3 vs 4Group 1 vs 3Group 2 vs 4
Group A63 (18)17 (17)46 (52)0 (0)0 (0)< 0.0010.001< 0.001
Group B124 (7)20 (20)4 (5)0 (0)0 (0)0.002< 0.0010.035
Group B2175 (50)10 (10)0 (0)52 (100)113 (100)0.002< 0.001< 0.001
Group D89 (25)51 (52)38 (43)0 (0)0 (0)< 0.001< 0.001
F10 papA allele168 (48)9 (9)8 (9)42 (81)109 (97)0.002< 0.001< 0.001
O25b rfb allele159 (45)0 (0)0 (0)48 (92)110 (97)< 0.001< 0.001
Post-2003 origin338 (96)89 (91)85 (97)51 (98)113 (100)0.100.08
  • a Group, major E. coli phylogenetic group; F10 papA allele, P fimbria structural subunit variant; O25b rfb allele, O25 lipopolysaccharide synthesis.

  • b M15+, positive for blaCTX-M-15; M15, negative for blaCTX-M-15; ST131+, ST131 sequence type; ST131, non-ST131 sequence type.

  • c P values (by Fisher's exact test; two-tailed) are shown where P ≤ 0.10. For all variables, an initial 4-group comparison yielded P ≤ 0.003.