TABLE 1

Cumulative frequency distributions of cefepime and cefepime-tazobactam (with tazobactam at fixed concentration of 8 μg/ml) MIC results when tested against bacterial isolatesa

Organism (no. of isolates) and antimicrobialNo. of organisms (cumulative % inhibited) at MIC (μg/ml) of:
≤0.030.060.120.250.51248163264>64
Enterobacteriaceae (6,219)
    Cefepime2,625 (42.2)1,469 (65.8)519 (74.2)244 (78.1)155 (80.6)93 (82.1)122 (84.0)92 (85.5)147 (87.9)151 (90.3)131 (92.4)166 (95.1)305 (100.0)
    Cefepime-tazobactam3,175 (51.1)1,585 (76.5)596 (86.1)304 (91.0)141 (93.3)84 (94.6)68 (95.7)40 (96.4)36 (96.9)42 (97.6)26 (98.0)54 (98.9)68 (100.0)
E. coli (2,211)
    Cefepime1,000 (45.2)535 (69.4)162 (76.8)48 (78.9)38 (80.6)20 (81.5)44 (83.5)37 (85.2)67 (88.2)65 (91.2)52 (93.5)58 (96.2)85 (100.0)
    Cefepime-tazobactam1,290 (58.3)551 (83.3)207 (92.6)93 (96.8)27 (98.1)10 (98.5)14 (99.1)7 (99.5)6 (99.7)3 (99.9)1 (99.9)0 (>99.9)2 (100.0)
E. coli with ESBL phenotype (471)
    Cefepime5 (1.1)14 (4.0)18 (7.9)10 (10.0)18 (13.8)12 (16.3)33 (23.4)35 (30.8)66 (44.8)65 (58.6)52 (69.6)58 (82.0)85 (100.0)
    Cefepime-tazobactam87 (18.5)148 (49.9)112 (73.7)65 (87.5)22 (92.1)5 (93.2)14 (96.2)6 (97.5)6 (98.7)3 (99.4)1 (99.6)0 (99.6)2 (100.0)
Klebsiella spp. (2,138)
    Cefepime981 (45.9)343 (61.9)113 (67.2)60 (70.0)39 (71.8)32 (73.3)31 (74.8)27 (76.1)61 (78.9)73 (82.3)72 (85.7)97 (90.2)209 (100.0)
    Cefepime-tazobactam1,139 (53.3)410 (72.5)142 (79.1)87 (83.2)58 (85.9)40 (87.7)34 (89.3)29 (90.7)25 (91.9)36 (93.5)22 (94.6)52 (97.0)64 (100.0)
Klebsiella spp. with ESBL phenotype (661)
    Cefepime2 (0.3)7 (1.4)12 (3.2)16 (5.6)26 (9.5)28 (13.8)31 (18.5)27 (22.5)61 (31.8)73 (42.8)72 (53.7)97 (68.4)209 (100.0)
    Cefepime-tazobactam103 (15.6)103 (31.2)58 (39.9)53 (48.0)46 (54.9)36 (60.4)34 (65.5)29 (69.9)25 (73.7)36 (79.1)22 (82.5)52 (90.3)64 (100.0)
K. pneumoniae (1,788)
    Cefepime747 (41.8)293 (58.2)96 (63.5)50 (66.3)32 (68.1)23 (69.4)23 (70.7)23 (72.0)57 (75.2)70 (79.1)70 (83.0)95 (88.3)209 (100.0)
    Cefepime-tazobactam879 (49.2)372 (70.0)129 (77.2)78 (81.5)51 (84.4)31 (86.1)28 (87.7)26 (89.1)21 (90.3)36 (92.3)21 (93.5)52 (96.4)64 (100.0)
K. pneumoniae with ESBL phenotype (602)
    Cefepime1 (0.2)3 (0.7)5 (1.5)8 (2.8)19 (6.0)19 (9.1)23 (13.0)23 (16.8)57 (26.2)70 (37.9)70 (49.5)95 (65.3)209 (100.0)
    Cefepime-tazobactam92 (15.3)96 (31.2)53 (40.0)47 (47.8)39 (54.3)27 (58.8)28 (63.5)26 (67.8)21 (71.3)36 (77.2)21 (80.7)52 (89.4)64 (100.0)
MEM-nonsusceptible K. pneumoniae (183)
    Cefepime1 (0.5)6 (3.8)6 (7.1)17 (16.4)33 (34.4)120 (100.0)
    Cefepime-tazobactam6 (3.3)10 (8.7)12 (15.3)32 (32.8)16 (41.5)49 (68.3)58 (100.0)
Klebsiella oxytoca (345)
    Cefepime230 (66.7)50 (81.2)16 (85.8)10 (88.7)7 (90.7)9 (93.3)8 (95.7)4 (96.8)4 (98.0)3 (98.8)2 (99.4)2 (100.0)
    Cefepime-tazobactam256 (74.2)38 (85.2)12 (88.7)9 (91.3)7 (93.3)9 (95.9)6 (97.7)3 (98.6)4 (99.7)0 (99.7)1 (100.0)
Klebsiella oxytoca with ESBL phenotype (59)
    Cefepime1 (1.7)4 (8.5)7 (20.3)8 (33.9)7 (45.8)9 (61.0)8 (74.6)4 (81.4)4 (88.1)3 (93.2)2 (96.6)2 (100.0)
    Cefepime-tazobactam11 (18.6)7 (30.5)5 (39.0)6 (49.2)7 (61.0)9 (76.3)6 (86.4)3 (91.5)4 (98.3)0 (98.3)1 (100.0)
P. mirabilis (228)
    Cefepime27 (11.8)144 (75.0)32 (89.0)8 (92.5)1 (93.0)7 (96.1)1 (96.5)1 (96.9)3 (98.2)0 (98.2)0 (98.2)1 (98.7)3 (100.0)
    Cefepime-tazobactam39 (17.1)155 (85.1)29 (97.8)4 (99.6)1 (100.0)
P. mirabilis with ESBL phenotype (19)
    Cefepime2 (10.5)1 (15.8)7 (52.6)1 (57.9)1 (63.2)3 (78.9)0 (78.9)0 (78.9)1 (84.2)3 (100.0)
    Cefepime-tazobactam4 (21.1)10 (73.7)4 (94.7)1 (100.0)
Enterobacter spp. (629)
    Cefepime208 (33.1)151 (57.1)78 (69.5)55 (78.2)39 (84.4)15 (86.8)30 (91.6)19 (94.6)11 (96.3)9 (97.8)4 (98.4)5 (99.2)5 (100.0)
    Cefepime-tazobactam233 (37.0)151 (61.0)92 (75.7)63 (85.7)38 (91.7)25 (95.7)13 (97.8)4 (98.4)3 (98.9)3 (99.4)2 (99.7)1 (99.8)1 (100.0)
CAZ-nonsusceptible Enterobacter spp. (179)
    Cefepime4 (2.2)17 (11.7)33 (30.2)31 (47.5)15 (55.9)28 (71.5)18 (81.6)10 (87.2)9 (92.2)4 (94.4)5 (97.2)5 (100.0)
    Cefepime-tazobactam1 (0.6)11 (6.7)41 (29.6)45 (54.7)32 (72.6)23 (85.5)12 (92.2)4 (94.4)3 (96.1)3 (97.8)2 (98.9)1 (99.4)1 (100.0)
Morganella morganii (165)
    Cefepime104 (63.0)47 (91.5)6 (95.2)4 (97.6)1 (98.2)0 (98.2)1 (98.8)2 (100.0)
    Cefepime-tazobactam129 (78.2)30 (96.4)3 (98.2)3 (100.0)
Citrobacter spp. (311)
    Cefepime197 (63.3)45 (77.8)12 (81.7)14 (86.2)15 (91.0)10 (94.2)6 (96.1)4 (97.4)1 (97.7)1 (98.1)2 (98.7)3 (99.7)1 (100.0)
    Cefepime-tazobactam200 (64.3)57 (82.6)18 (88.4)19 (94.5)7 (96.8)5 (98.4)3 (99.4)0 (99.4)1 (99.7)0 (99.7)0 (99.7)1 (100.0)
Serratia marcescens (245)
    Cefepime8 (3.3)98 (43.3)81 (76.3)31 (89.0)11 (93.5)4 (95.1)4 (96.7)1 (97.1)3 (98.4)2 (99.2)0 (99.2)1 (99.6)1 (100.0)
    Cefepime-tazobactam8 (3.3)116 (50.6)72 (80.0)33 (93.5)10 (97.6)2 (98.4)3 (99.6)0 (99.6)1 (100.0)
Proteus vulgaris (144)
    Cefepime11 (7.6)76 (60.4)31 (81.9)15 (92.4)6 (96.5)1 (97.2)3 (99.3)1 (100.0)
    Cefepime-tazobactam32 (22.2)84 (80.6)26 (98.6)2 (100.0)
Providencia spp. (148)
    Cefepime89 (60.1)30 (80.4)4 (83.1)9 (89.2)5 (92.6)4 (95.3)2 (96.6)0 (96.6)1 (97.3)1 (98.0)1 (98.6)1 (99.3)1 (100.0)
    Cefepime-tazobactam105 (70.9)31 (91.9)7 (96.6)0 (96.6)0 (96.6)2 (98.0)1 (98.6)0 (98.6)0 (98.6)0 (98.6)1 (99.3)0 (99.3)1 (100.0)
P. aeruginosa (1,171)
    Cefepime4 (0.3)4 (0.7)36 (3.8)136 (15.4)414 (50.7)184 (66.4)169 (80.9)110 (90.3)63 (95.6)24 (97.7)27 (100.0)
    Cefepime-tazobactam1 (0.1)5 (0.5)6 (1.0)17 (2.5)171 (17.1)404 (51.6)184 (67.3)177 (82.4)108 (91.6)61 (96.8)15 (98.1)22 (100.0)
CAZ-nonsusceptible P. aeruginosa (252)
    Cefepime1 (0.4)3 (1.6)17 (8.3)40 (24.2)79 (55.6)61 (79.8)24 (89.3)27 (100.0)
    Cefepime-tazobactam2 (0.8)4 (2.4)24 (11.9)45 (29.8)82 (62.3)58 (85.3)15 (91.3)22 (100.0)
MEM-nonsusceptible P. aeruginosa (244)
    Cefepime1 (0.4)15 (6.6)23 (16.0)52 (37.3)62 (62.7)45 (81.1)20 (89.3)26 (100.0)
    Cefepime-tazobactam4 (1.6)13 (7.0)26 (17.6)56 (40.6)65 (67.2)46 (86.1)14 (91.8)20 (100.0)
A. baumannii (591)
    Cefepime1 (0.2)5 (1.0)8 (2.4)42 (9.5)54 (18.6)25 (22.8)21 (26.4)42 (33.5)105 (51.3)288 (100.0)
    Cefepime-tazobactam53 (9.0)17 (11.8)11 (13.7)14 (16.1)9 (17.6)15 (20.1)18 (23.2)8 (24.5)9 (26.1)31 (31.3)55 (40.6)90 (55.8)261 (100.0)
  • a Tazobactam was used at a fixed concentration of 8 μg/ml, and the results are for 7,981 bacterial isolates from all geographic regions combined. Values in bold indicate MIC50s and MIC90s. Abbreviations: ESBL phenotype, extended-spectrum β-lactamase (ESBL)-screen-positive phenotype, defined as an MIC of ≥2 μg/ml for ceftriaxone, ceftazidime, and/or aztreonam; CAZ nonsusceptible, ceftazidime nonsusceptible (MICs, ≥8 μg/ml for Enterobacteriaceae and ≥16 μg/ml for P. aeruginosa); MEM nonsusceptible, meropenem nonsusceptible (MICs, ≥2 μg/ml for Enterobacteriaceae and ≥4 μg/ml for P. aeruginosa) (7).