Table 1: In Vitro Susceptibilities of C. freundii and C. koseri Isolates from Blood Cultures at M.D. Anderson Hospital and Tumor Institute, 1977-1985
MIC of C. freundii
MIC of C. koseri
Antibiotic
Range
MIC50
MIC90
% Susceptible
Range
MIC50
MIC90
% Susceptible
Ampicillin
1->128
16
64
26
2-32
16
32
28
Timentin
0.5->128
64
128
37
0.5->128
2
>128
71
Piperacillin
0.25->128
32
128
41
0.5->128
4
64
78
Cephalothin
8-128
>128
>128
4
2->128
4
>128
50
Cefamandole
0.25->128
64
>128
41
0.5->128
1
128
64
Cefoperazone
≤0.06-128
32
64
45
≤0.06-128
0.25
32
70
Ceftriaxone
≤0.06-128
16
64
41
≤0.06-32
≤0.06
32
71
Ceftizoxime
≤0.06-128
4
32
48
≤0.06-32
≤0.06
32
71
Ceftazidime
≤0.06-128
32
128
41
≤0.06-64
0.25
32
71
Aztreonam
≤0.06-64
8
32
52
≤0.06-16
≤0.06
16
79
Imipenem
0.125-1
0.25
0.5
100
0.125-1
0.25
0.5
100
Gentamicin
≤0.06-16
0.5
8
89
0.25-64
0.25
1
92
Netilmicin
≤0.06-32
0.5
2
96
0.25-2
0.25
1
100
Amikacin
0.25-4
1
2
100
0.3-2
1
2
100
Enoxacin
≤0.06-0.25
≤0.06
0.25
100
≤0.06-0.125
≤0.06
≤0.06
100
Ciprofloxacin
≤0.06
≤0.06
≤0.06
100
≤0.06
≤0.06
≤0.06
100
Adapted from Samonis G, Ho DH, Gooch DF, Rolston KVI, Bodey GP. In vitro susceptibility of Citrobacter species to various antimicrobial agents.
Table 2: In Vitro Susceptibilities of C. freundii Isolates Collected at the National Taiwan University Hospital, 1987-1988 and 1997-1998
MIC of 1987-1988 isolates
MIC of 1997-1998 isolates
Antibiotic
Range
MIC50
MIC90
% Susceptible
Range
MIC50
MIC90
% Susceptible
Ticarcillin
1-≥256
≥256
≥256
27.9
1-≥256
≥256
≥256
27.9
Piperacillin
1-≥256
32
128
36.1
1-≥256
64
≥256
29.5
Cefazolin
0.5-≥256
≥256
≥256
23.0
1-≥256
≥256
≥256
19.7
Cefuroxime
1-≥256
64
≥256
36.1
1-≥256
128
≥256
26.2
Ceftriaxone
≤0.03-128
8
64
50.8
≤0.03-≥256
16
≥256
42.6
Ceftazidime
≤0.03-≥256
16
64
49.2
≤0.03-≥256
16
≥256
42.6
Cefepime
≤0.03-8
0.125
1
100
≤0.03-8
0.25
4
100
Cefpirome
≤0.03-16
0.25
2
98.4
≤0.03-32
0.5
8
93.4
Aztreonam
≤0.03-128
8
64
50.8
≤0.03-128
8
64
42.6
Imipenem
0.06-2
0.125
0.25
100
0.06-2
0.125
1
100
Meropenem
≤0.03-1
≤0.03
0.125
100
≤0.03-1
≤0.03
0.5
100
Gentamicin
0.25-≥256
0.5
≥256
63.9
0.125-≥256
8
≥256
44.2
Tobramycin
0.25-≥256
0.5
32
77.0
0.25-≥256
8
≥256
49.2
Amikacin
0.5-64
1
8
93.4
0.5-128
2
64
73.8
Ciprofloxacin
≤0.03-8
0.06
2
88.5
≤0.03-16
0.125
4
67.2
Adapted from Wang JT, Chang SC, Chen YC, Luh KT. Comparison of antimicrobial susceptibility of Citrobacter freundii isolates in two different time periods.
Table 3: In Vitro Susceptibility of Clinical Isolates of Citrobacter by Routine Disk Susceptibility Test at National Taiwan University Hospital
Susceptible % C. freundii isolates
Susceptible % C. koseri isolates
Antibiotic
1994
(n=169)
1997
(n=244)
2000
(n=351)
1994
(n=8)
1997
(n=51)
2000
(n=98)
Ampicillin
9
2
1
0
2
3
Amoxicillin＋clavulanic acid
12
5
4
75
90
85
Cefazolin
19
4
2
67
88
87
Cefmetazole
18
12
11
100
98
94
Cefotaxime
55
38
52
100
94
94
Aztreonam
59
41
50
100
94
97
Imipenem
99
98
99
100
100
100
Gentamicin
76
64
71
100
98
91
Tobramycin
76
-
-
100
-
-
Amikacin
91
88
93
100
100
96
Nalidixic acid
77
45
71
100
100
100
Norfloxacin
91
77
83
100
100
100
Ciprofloxacin
89
81
88
100
100
100
Trimethoprim/sulfamethoxazole
63
33
62
100
94
68
Tetracycline
48
-
-
100
-
-
Chloramphenicol
58
-
-
100
-
-