Duke University Medical Center
Clinical Microbiology Laboratory
Durham, North Carolina 27710
SUMMARY OF
ANTIMICROBIAL SUSCEPTIBILITY
TEST RESULTS
2003
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
2/2004
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 (957)
E. faecalis (126)
E. faecium (90)
Enterococcus spp. (741)
82
99
14
88
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
80
98
28
83
NT
NT
NT
NT
Staphylococcus aureus (1948)
MSSA (960)
MRSA (988)
NT
NT
NT
49
100
0
49
100
0
39
70
8
39
70
8
100
100
100
91
98
85
Staphylococcus spp., coagulasenegative (339)
NT
29c
29
NT
NT
100
NT
________________________________________________________________________________________________________________________
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/TAZ (piperacillin/tazobactam - $$$$$)
TOB (tobramycin - $)
T/S (trimethoprim/sulfamethoxazole - $)
VAN (vancomycin - $$)
________________________________________________________________________________________________________________________
TABLE 2. Percent Susceptible, Gram-negative Bacilli
(MIC breakpoint, µg per ml)
Other
Antimicrobials
______________
Beta-lactams
Aminoglycosides
_____________________________________________
___________________
AMP/
PIP/
Microorganism (No. tested)
AMP
SUL
CFZ
CAZ
CROb
IMP TAZ
GEN
AMK
TOB
CIP
T/S
(8)
(8/4)
(8)
(8)
(8)
(4) (16/4)
(4)
(16)
(4)
(1)
(2/38)
_________________________________________________________________________________________________________________________
Alcaligenes xylosoxidans (65)
NT
NT
NT
52
NT
88
86
0
0
0
23
68
Acinetobacter baumannii (58)
NT
NT
0
72
58
100
80
88
97
97
83
86
Burkholderia cepacia (89)
NT
NT
NT
46
NT
32
62
0
0
0
18
31
0
99
99
100
100
100
97
100
100
100
100
99
35
46
0
74
74
99
91
89
100
87
80
74
Enterobacter aerogenes (144)
0
0
0
83
85
99
88
97
99
98
93
97
Enterobacter cloacae (241)
0
0
0
67
65
100
76
92
100
95
85
86
Escherichia coli (2702)
64
88
92
98
99
100
97
94
100
95
92
83
Klebsiella oxytoca (83)
0
82
54
98
91
100
85
94
100
96
93
92
Klebsiella pneumoniae (718)
0
89
92
96
97
100
94
97
100
97
93
89
Morganella morganii (34)
0
0
0
88
100
97
100
94
100
100
88
88
Proteus mirabilis (365)
93
99
97
100
100
100
100
94
100
96
79
87
Pseudomonas aeruginosa (1217)
NT
NT
NT
77a
NT
74
86c
58
67
81
58
NT
0
0
0
97
98
99
96
97
98
90
87
99
Citrobacter koserii (84)
Citrobacter freundii (122)
Serratia marcescens (168)
Stenotrophomonas maltophilia (166) NT
NT
0
38
0
0
0
0
0
0
21
78
_______________________________________________________________________________________________________________________
Numbers in boldface indicate >10% decrease in susceptibility from 2002 to 2003.
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 = 118)
_________________________________________________________________
Ampicillin-sulbactam ($$$$$)
8/4
83
Cefoxitin ($$$)
16
69
Clindamycin ($)
2
80
Imipenem (Meropenem) ($$$$$$)
4
99
Metronidazole ($ - $$)
8
100
Piperacillin-tazobactam ($$$$$)
32/4
100
__________________________________________________________________
$ = 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.
Streptococcus pneumoniae. (No. tested = 101).
Meningitis Caused by Streptococcus pneumoniae, MIC Breakpoint (µg per ml)
Penicillin
Ceftriaxone or cefotaxime
% Susceptible
64 (<0.06)
88 (<0.5)
% Intermediate
23 (0.1-1)
9 (1.0)
% Resistant
13 (>2.0)
3 (>2.0)
Other Infections Caused by Streptococcus pneumoniae, MIC Breakpoint (µg per ml)
Ceftriaxone or cefotaxime
97 (<1.0)
1 (2.0)
2 (>4.0)
Erythromycin
68 (<0.25)
0 (0.5)
32 (>1.0)
Levofloxacin
98 (<2.0)
0(4.0)
2 (>8.0)
2.
Haemophilus influenzae. (No. tested = 125). All isolates were non-type b: 99 (79%) were ß-lactamase negative
and predictably susceptible to ampicillin (amoxicillin); 26 (21%) were -lactamase positive and, therefore, resistant
to ampicillin (amoxicillin). H. influenzae is predictably susceptible to cefotaxime and ceftriaxone and usually to
cefuroxime.
TABLE 5. Percent Susceptible, Yeasts (1999-2003)a
(MIC breakpoint, µg per ml)
Microorganism
(No. tested =
Amphotericin B
Fluconazole
amphotericin B/
(<1)c
(<8)
fluconazole)b
Candida albicans
(52/125)
100
82d
C. tropicalis
(26/78)
100
77
C. parapsilosis
(23/53)
100
91
C. krusei
(--)


C. glabrata
(25/79)
100
65
C. lusitaniae
(--)


Cryptococcus neoformans (1/21)

86
 = usually susceptible  = often resistant  = 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.