Duke University Medical Center
Clinical Microbiology Laboratory
Durham, North Carolina 27710
SUMMARY OF
ANTIMICROBIAL SUSCEPTIBILITY
TEST RESULTS
2002
HOURS OF
OPERATION:
24 hours per day 365 days per year.
TELEPHONE:
684-2089
A certified medical technologist is
on duty at all times.
CONSULTATIONS:
Page 970-8885
A physician (Medical Microbiology
Fellow or Resident) is on call at all times
with faculty backup.
TEACHING:
Teaching Rounds (Clinical correlations)
Monday-Friday 1:15-1:45 PM
1/2003
TABLE 1. Percent Susceptiblea, Gram-positive Cocci
(MIC breakpoint, µg per ml)
Beta-lactams
Other Antimicrobials
________________________
___________________________________________________
Microorganism (No. tested)
AMP
NAF
CFZ
CLI
ERY
VAN
T/S
(8)
(2)
(8)
(0.5)
(0.5)
(4)
(2/38)
________________________________________________________________________________________________________________________
Enterococci b (992)
E. faecalis (126)
E. faecium (80)
Enterococcus spp. (786)
81
100
11
85
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
75
94
23
77
NT
NT
NT
NT
Staphylococcus aureus (1938)
MSSA (1008)
MRSA (930)
NT
NT
NT
52
100
0
52
100
0
40
68
10
40
68
10
100
100
100
91
98
84
Staphylococcus spp., coagulasenegative (297)
NT
24
NT
NT
100
NT
24 c
________________________________________________________________________________________________________________________
These data were obtained by broth microdilution or disk diffusion methods according to National Committee for Clinical Laboratory Standards (NCCLS)
guidelines. Data are based on microorganisms from both inpatients and outpatients. No attempt was made to differentiate nosocomial isolates.
a Susceptible implies that an infection due to the microorganism may be appropriately treated with the dosage of antimicrobial agent recommended for
that type of infection and infecting species, unless otherwise contraindicated.
b For enterococci the designation "susceptible" implies the need for combined therapy (ampicillin or vancomycin plus an aminoglycoside) in endocarditis
or other serious invasive infections to achieve bactericidal action and an improved therapeutic response.
c Susceptible MIC breakpoint is <0.25 µg/ml for coagulase-negative staphylococci.
MIC (minimum inhibitory concentration) is the lowest concentration of a drug which will inhibit growth of a microorganism in vitro. For the drug to be
effective in vivo, a higher concentration than the MIC of the drug (at least 2 to 4 times higher) should be achieved at the site of infection. MIC
breakpoints are based on achievable serum levels in adults with normal renal function.
________________________________________________________________________________________________________________________
NT = Not tested.
$ = Relative daily acquisition cost for recommended doses of parenteral therapy.
AMK (amikacin - $/$$)
AMP (ampicillin - $)
AMP/SUL (ampicillin/sulbactam - $$$$$)
CAZ (ceftazidime - $$$)
CFZ (cefazolin - $)
CIP (ciprofloxacin - $/$$$$)
CLI (clindamycin - $)
CRO (ceftriaxone - $$$)
CTX (cefotaxime - $$$)
ERY (erythromycin - $)
GEN (gentamicin - $)
IMP (imipenem - $$$$$$)
LEV (levofloxacin - $/$$)
NAF (nafcillin - $)
PEN (penicillin - $)
PIP (piperacillin - $$$$$)
TOB (tobramycin - $)
T/S (trimethoprim/sulfamethoxazole - $)
VAN (vancomycin - $$)
________________________________________________________________________________________________________________________
TABLE 2. Percent Susceptible, Gram-negative Bacilli
(MIC breakpoint, µg per ml)
Other
Antimicrobials
______________
Beta-lactams
Aminoglycosides
_____________________________________________
___________________
AMP/
Microorganism (No. tested)
AMP
SUL
CFZ
CAZ
CROb
IMP PIP
GEN
AMK
TOB
CIP
T/S
(8)
(8/4)
(8)
(8)
(8)
(4) (16)
(4)
(16)
(4)
(1)
(2/38)
_________________________________________________________________________________________________________________________
Alcaligenes xylosoxidans (73)
NT
NT
NT
45
NT
86
82
0
0
0
8
55
Acinetobacter baumannii (58)
NT
NT
0
78
54
100
63
86
98
97
78
87
Burkholderia cepacia (71)
NT
NT
NT
61
NT
34
32
0
0
0
15
54
0
88
91
100
97
100
78
100
100
100
100
94
18
50
0
54
60
100
51
85
97
82
70
74
Enterobacter aerogenes (125)
0
0
0
62
71
98
59
96
99
96
86
96
Enterobacter cloacae (199)
0
0
0
70
71
98
66
91
97
91
88
89
Escherichia coli (2803)
62
75
88
97
97
100
63
93
99
93
94
85
Klebsiella oxytoca (116)
0
57
41
93
78
100
60
88
97
87
85
80
Klebsiella pneumoniae (737)
0
79
92
95
96
100
76
96
99
95
91
84
Morganella morganii (49)
0
0
0
79
95
100
67
79
100
92
78
80
Proteus mirabilis (338)
92
97
95
100
100
100
94
93
99
94
82
91
Pseudomonas aeruginosa (1288)
NT
NT
NT
79 a
NT
75
82 c
58
70
81
59
NT
0
0
0
95
92
99
88
96
97
87
88
97
Citrobacter koserii (65)
Citrobacter freundii (100)
Serratia marcescens (181)
Stenotrophomonas maltophilia (165) NT
NT
0
38
0
0
0
0
0
0
27
77
_______________________________________________________________________________________________________________________
Numbers in boldface indicate >10% decrease in susceptibility from 2001 to 2002.
a For P. aeruginosa, ceftazidime (CAZ) usually predicts susceptibility to aztreonam.
b For Enterobacteriaceae, ceftriaxone (CRO) usually predicts susceptibility to cefotaxime.
c For P. aeruginosa, susceptible MIC breakpoint for piperacillin (with or without tazobactam) is < 64 µg/ml which requires high doses.
TABLE 3. Percent Susceptible, Anaerobic Gram-negative Bacillia
Antimicrobial
MIC Breakpoint
B. fragilis groupb
(cost per day)
(µg per ml)
(No. tested = 83)
_________________________________________________________________
Ampicillin-sulbactam ($$$$$)
8/4
82
Cefoxitin ($$$)
16
61
Clindamycin ($)
2
76
Imipenem (Meropenem) ($$$$$$)
4
99
Metronidazole ($ - $$)
8
100
Piperacillin-tazobactam ($$$$$)
32/4
99
__________________________________________________________________
$ = Relative daily acquisition cost for recommended doses of parenteral therapy.
a Pigmented gram-negative bacilli (Prevotella and Porphyromonas spp.), Fusobacterium spp., and grampositive anaerobic cocci and bacilli are usually susceptible to -lactam antibiotics, clindamycin, and
metronidazole.
b Includes B. fragilis, B. thetaiotaomicron, B. ovatus, B. distasonis, B. vulgatus, B. uniformis, B. caccae,
B. eggerthii, B. merdae, and B. stercoris.
TABLE 4. Fastidious Microorganisms
1.
Haemophilus influenzae (No. tested = 115). All isolates were non-type b: 86 (75%) were ß-lactamase negative
and predictably susceptible to ampicillin (amoxicillin); 29 (25%) were -lactamase positive and, therefore, resistant
to ampicillin (amoxicillin). H. influenzae is predictably susceptible to cefotaxime and ceftriaxone and usually to
cefuroxime.
2.
Streptococcus pneumoniae. Rx NOTE: Breakpoints for pneumococci are based on concentrations of
penicillin and ceftriaxone (or cefotaxime) required to treat non-meningitis infections. Consult Infectious
Diseases for patients with meningitis (higher doses required and susceptible breakpoints are lower). High
doses of intravenous penicillins (e.g., at least 2 million units every 4 h in adults with normal renal function) or
similarly ampicillin (e.g., 2 g every 6 h) are effective in treating pneumococcal pneumonia due to strains in the
intermediate category.
MIC Breakpoint (µg/ml) for Non-meningitis Infections with Streptococcus pneumoniae
(No. tested)
Penicillin
(107)
Ceftriaxone or
cefotaxime
(107)
Erythromycin (107)
Levofloxacin
(107)
% Susceptible
55 (<0.06)
95 (<1.0)
65 (<0.25)
99 (<2.0)
% Intermediate
28 (0.1-1)
% Resistant
17 (>2.0)
4 (2.0)
0 (0.5)
0 (4.0)
1 (>4.0)
35 (>1.0)
1 (>8.0)
TABLE 5. Percent Susceptible, Yeasts (1999-2002)a
(MIC breakpoint, µg per ml)
Amphotericin B
Fluconazole
Microorganism (No. tested, AmphB/Flu)b
(<1)c
(<8)
Candida albicans
(52/110)
100
81d
C. tropicalis
(24/70)
100
74
C. parapsilosis
(23/51)
100
90
C. krusei
(--)
l
m
C. glabrata
(24/57)
100
58
C. lusitaniae
(--)

l
Cryptococcus neoformans (1/20)
l
90
l = usually susceptible  = often resistant m = inherently resistant
a Percent susceptibility reflects selected patient population.
b NCCLS M27-A (1997) Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts.
Testing may be useful in serious or persistent infections due to organisms with unpredictable susceptibility
profiles, especially when standard regimens fail or are contraindicated.
c Tentative NCCLS breakpoint.
d Most initial isolates of C. albicans are susceptible.