Table 1

Antibiotic resistance and β-lactamase genes in E. coli B2-ST131-O25b, B2-ST131-O16, D-ST405, and OST clonal groupsg

CharacteristicNo. (%) of isolatesP valuea
ST131-O25b (n = 41)ST131-O16 (n = 26)ST405 (n = 41)OST (n = 41)OverallOST vs:
ST131-O25bST131-O16ST405
Antimicrobial resistance
    Ciprofloxacin37 (90)5 (19)41 (100)22 (54)<0.001<0.0010.006<0.001
    Nalidixic acid37 (90)18 (69)41 (100)32 (78)<0.001<0.0010.565<0.001
    Amikacin0 (0)0 (0)2 (5)1 (2)0.6301.0001.0001.000
    Gentamicin18 (44)3 (12)17 (41)6 (15)0.0010.0071.0000.013
    Tobramycin15 (37)3 (12)21 (51)7 (17)0.0010.0800.7290.002
    Minocycline3 (7)15 (58)9 (22)18 (44)<0.001<0.0010.3220.059
    Trimethoprim-sulfamethoxazole18 (44)13 (50)28 (68)26 (63)0.4520.1210.3170.816
    Piperacillin-tazobactam2 (5)3 (12)7 (17)4 (10)0.0380.6751.0000.519
    Multidrug resistance13a (32)2 (8)23a (56)16 (39)<0.0010.6450.0050.184
ESBL genes
    Any blaCTX-M gene39 (95)23 (88)41 (100)39 (95)0.1681.0000.3690.494
    blaCTX-M-1423 (56)19 (73)30b (73)19b (46)0.0410.5080.0440.024
    blaCTX-M-155 (12)2 (8)12b (29)7b,c (17)0.1110.7560.4650.295
    blaCTX-M-278a (20)0 (0)0a (0)2 (5)0.0010.0880.5180.494
    blaCTX-M-22 (5)1 (4)0 (0)5 (12)0.0980.4320.3920.027
    blaCTX-M-31 (2)0 (0)0 (0)4 (10)0.0940.3590.6410.058
    Other blaCTX-M genesd0 (0)1 (2)1 (2)3 (7)0.4420.1161.0000.616
    blaTEMe1 (2)1 (4)0 (0)2c (5)0.6991.0001.0000.494
    blaSHVf1 (2)2 (8)0 (0)1 (2)0.3311.0000.5550.500
Other β-lactamase genes
    blaTEM-128 (68)9 (35)16 (39)15 (37)0.0120.0081.0001.000
    blaOXA-12 (5)0 (0)3 (7)2 (5)0.6541.0001.0001.000
  • a Comparison between the ST131-O25b and ST405 groups revealed that significant differences were found only in multidrug resistance (P = 0.045) and carriage of blaCTX-M-27 (P = 0.005).

  • b Two ST405 isolates and one OST isolate were positive for both blaCTX-M-14 and blaCTX-M-15.

  • c One OST isolate was positive for both blaCTX-M-15 and blaTEM-20.

  • d blaCTX-M-55 was found in one ST131-O16 isolate, and blaCTX-M-24 was found in one ST405 isolate. blaCTX-M-9, blaCTX-M-24, and blaCTX-M-55 were each found in three OST isolates.

  • e blaTEM-20 was found in two OST isolates, and blaTEM-12 was found in the other two isolates.

  • f blaSHV-12 was found in one ST131-O16 isolate, and blaSHV-2 was found in the other three isolates.

  • g All isolates in this study were susceptible to imipenem. Multidrug resistance was defined by resistance to at least one agent in three or more antimicrobial categories.