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Journal of Clinical Microbiology, November 1998, p. 3444-3445, Vol. 36, No. 11
0095-1137/98/$00.00+0
LETTERS TO THE EDITOR
Catheter Sepsis Due to Mycobacterium chelonae
 |
LETTER |
We read with interest the recent article by Hsueh et al. on
catheter sepsis due to Mycobacterium chelonae
(3).
In the antimicrobial susceptibility section, the clarithromycin MIC is
reported to be 1.5 to 2.0 µg/ml. The authors later state,
"... our isolates were not susceptible to any of the antibiotics tested, including clarithromycin." In another study (1),
which found 100% of M. chelonae isolates to be susceptible
to 
1.0 µg of clarithromycin per ml (by a different susceptibility
method), resistance is defined as >4 µg/ml. This breakpoint for
rapidly growing mycobacteria, although not approved by the National
Committee for Clinical Laboratory Standards (NCCLS), has been
proposed (2). Thus, we would consider these isolates to be
susceptible to clarithromycin and suspect the somewhat higher MICs than
reported by Hsueh et al. (3) could be method dependent (E
test versus broth microdilution). Thus, clarithromycin likely
contributed to the clinical and microbiologic response of the
patient.
| |
REFERENCES |
| 1.
|
Brown, B. A.,
R. J. Wallace, Jr.,
G. Onyi,
V. DeRosas, and R. J. Wallace, III.
1992.
Activities of four macrolides, including clarithromycin, against Mycobacterium fortuitum, Mycobacterium chelonae, and Mycobacterium chelonae-like organisms.
Antimicrob. Agents Chemother.
36:180-184[Abstract/Free Full Text].
|
| 2.
|
Brown, B. A.,
J. M. Swenson, and R. J. Wallace, Jr.
1992.
Broth microdilution MIC test for rapidly growing mycobacteria, p. 5.11.1.
In
H. D. Isenberg (ed.), Clinical microbiology procedures handbook, vol. 1. American Society for Microbiology, Washington, D.C.
|
| 3.
|
Hsueh, P.-R.,
L.-J. Teng,
P.-C. Yang,
Y.-C. Chen,
S.-W. Ho, and K.-T. Luh.
1998.
Recurrent catheter-related infection caused by a single clone of Mycobacterium chelonae with two colonial morphotypes.
J. Clin. Microbiol.
36:1422-1424[Abstract/Free Full Text].
|
| | | | |
Richard J. Wallace Jr.
Barbara A. Brown
Department of Microbiology
The University of Texas Health Center at Tyler
11937 U.S. Hwy. 271
Tyler, Texas 75708
|
| |
AUTHORS' REPLY |
We thank Drs. Wallace and Brown for their interest in our paper and for
their concern about the susceptibility of the Mycobacterium chelonae isolates to clarithromycin (4). The letter
from Drs. Wallace and Brown addresses two important questions that
deserve more attention and need more study. First, the M. chelonae isolates for which E-test clarithromycin MICs were 1.5 to
2 µg/ml should be considered susceptible. Second, clarithromycin
likely contributed to the clinical and microbiologic responses of the
patient.
Before we respond to their comments, we should give a more detailed
description of our patient. In the paper, we stated that the patient
had a satisfactory response to treatment with clarithromycin (500 mg
every 12 h), ciprofloxacin (300 mg every 12 h), and amikacin (750 mg every 12 h) for 1 month, followed by 2 months' treatment with clarithromycin (500 mg every 12 h) and ciprofloxacin (300 mg
every 12 h). We discontinued the antibiotics because the patient suffered severe gastrointestinal upset and abnormal liver function was
noticed. Follow-up examinations disclosed the disappearance of the
lesions over the right lung and the right subclavian vein. However, 2 months after the discontinuance of antimicrobial therapy, the patient
had a fever and developed a subcutaneous mass (2 by 3 cm) over her left
leg. Cultures of the aspirate specimen also yielded the M. chelonae isolate with two morphotypes. The clarithromycin E-test
MIC (2 µg/ml) and the random amplified polymorphic DNA patterns (with
five primers) of the isolates were identical to those of isolates A to
D described previously (4). A whole-body gallium scan
revealed no evidence of other foci of infection. The patient underwent
surgical debridement and is now on the third month of treatment with
clarithromycin (500 mg every 12 h) and ciprofloxacin (300 mg every
12 h).
Determination of MIC breakpoint criteria to define susceptibility for
an antimicrobial agent-microorganism combination is based on
pharmacokinetic data, population distribution of MICs, and studies of
clinical efficacy. As Drs. Wallace and Brown mentioned, the MIC
breakpoint criteria for susceptibility of M. chelonae to
clarithromycin (susceptible, 2 µg/ml; intermediate, 4 µg/ml; resistant, 
8 µg/ml) have not been approved by the NCCLS. The interpretive values that appeared in the ASM handbook were obtained from Abbott Laboratories, Abbott Park, Ill. (3). However,
different MIC breakpoint criteria for rapidly growing mycobacteria
(susceptible, 1 µg/ml; moderately susceptible, 2 µg/ml;
resistant, 4 µg/ml) were also suggested by other investigators
(2). Furthermore, these other investigators found that for
51 (51%) of 100 isolates of rapidly growing mycobacteria,
clarithromycin E-test MICs were 1 to 3 log2 dilutions lower
than MICs determined by the reference agar dilution method
(2).
Until now, no large-scale controlled clinical trials have documented
the clinical efficacy of clarithromycin for treating invasive
infections caused by M. chelonae, and the appropriate regimen for this infection remains undetermined (1). In a
study regarding the clinical efficacy of clarithromycin monotherapy for
treatment of 14 patients with cutaneous (disseminated) M. chelonae infections, 1 patient was initially given clarithromycin at a dosage of 1.0 g twice a day, because of a high clarithromycin MIC of 1 µg/ml (5). The remaining 13 patients, who
received clarithromycin at a dosage of 500 mg or 1 g twice a
day, all had isolates for which clarithromycin MICs were 0.25
µg/ml (5). On the other hand, the clarithromycin MIC for
the isolate recovered from our patient was 2.0 µg/ml. The
contribution of clarithromycin only at the prescribed dosage to the
clinical and microbiologic responses of our patient remains
questionable. In this situation, defining an isolate as susceptible or
resistant to clarithromycin according to the previously declared or
suggested criteria might be inappropriate.
Maybe we should change the statement "In contrast, our isolates were
not susceptible to any of the antibiotics tested, including clarithromycin," to "In contrast, all antibiotics tested except for
clarithromycin had poor activities against our isolates."
| |
REFERENCES |
| 1.
|
American Thoracic Society.
1997.
Diagnosis and treatment of disease caused by nontuberculosis mycobacteria.
Am. J. Respir. Care Med.
156:S21-S25.
|
| 2.
|
Biehle, J. R.,
S. J. Cavalieri,
M. A. Saubiolle, and L. J. Getsinger.
1995.
Evaluation of Etest for susceptibility testing of rapidly growing mycobacteria.
J. Clin. Microbiol.
33:1760-1764[Abstract].
|
| 3.
|
Brown, B. A.,
J. M. Swenson, and R. J. Wallace, Jr.
1992.
Broth microdilution MIC test for rapidly growing mycobacteria, p. 5.11.1-5.11.10.
In
H. D. Isenberg (ed.), Clinical microbiology procedures handbook, vol. 1. American Society for Microbiology, Washington, D.C.
|
| 4.
|
Hsueh, P. R.,
L. J. Teng,
P. C. Yang,
Y. C. Chen,
S. W. Ho, and K. T. Luh.
1998.
Recurrent catheter-related infection caused by a single clone of Mycobacterium chelonae with two colonial morphotypes.
J. Clin. Microbiol.
36:1422-1424.
|
| 5.
|
Wallace, R. J., Jr.,
D. Tanner,
P. J. Brennan, and B. A. Brown.
1993.
Clinical trial of clarithromycin for cutaneous (disseminated) infections due to Mycobacterium chelonae.
Ann. Intern. Med.
119:482-486[Abstract/Free Full Text].
|
| | | | |
Po-Ren Hsueh
Kwen-Tay Luh
Department of
Laboratory Medicine
National Taiwan University Hospital
No. 7, Chung-Shan South Rd.
Taipei, Taiwan
|
Journal of Clinical Microbiology, November 1998, p. 3444-3445, Vol. 36, No. 11
0095-1137/98/$00.00+0
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