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Journal of Clinical Microbiology, December 2001, p. 4597-4597, Vol. 39, No. 12
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.12.4597.2001
LETTERS TO THE EDITOR
Relative Sensitivities of Streptococcus pneumoniae
Strains to Penicillin and Ceftriaxone
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LETTER |
Examining the data of Brueggemann et al.
(1), we noticed that among strains of
Streptococcus pneumoniae that are highly sensitive to
penicillin, the sensitivities to penicillin usually exceeds the
sensitivities to ceftriaxone (with MICs calculated in micrograms per
milliliter). By contrast, among strains that are more resistant to
penicillin, sensitivities to ceftriaxone more frequently exceed those
to penicillin (Table 1). This finding emphasizes that mechanisms of resistance to different 
-lactams differ among Streptococcus pneumoniae strains. Alterations
in different penicillin-binding proteins (PBPs) have been
implicated. Altered PBPs 1a, 2x, 2a, and 2b have been pinpointed in
penicillin resistance (2-4, 6, 7), while altered PBPs 1a
and 2x are characteristic of resistance to extended-spectrum
cephalosporins (5). One can speculate that those PBPs that
bind penicillin more avidly than ceftriaxone mediate the rate-limiting
step in cell wall lysis under usual conditions but that, when these
PBPs mutate and bind penicillin poorly, the PBPs that preferentially bind ceftriaxone become rate limiting. This hypothesis requires empirical verification.
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TABLE 1.
Relative sensitivities to ceftriaxone of
Streptococcus pneumoniae strains with various penicillin
sensitivitiesa
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REFERENCES |
| 1.
|
Brueggeman, A. B.,
M. A. Pfaller, and G. Doern.
2001.
Use of penicillin MICs to predict in vitro activity of other -lactam antimicrobial agents against Streptococcus pneumoniae.
J. Clin. Microbiol.
39:367-369[Abstract/Free Full Text].
|
| 2.
|
Hakenbeck, R.,
H. Ellerbrok,
T. Briese,
S. Handwerger, and A. Tomasz.
1986.
Penicillin-binding proteins from penicillin-susceptible and -resistant pneumococci: immunological relatedness of altered proteins and changes in peptides carrying the -lactam binding site.
Antimicrob. Agents Chemother.
30:553-558[Abstract/Free Full Text].
|
| 3.
|
Hakenbeck, R.,
M. Tarpay, and A. Tomasz.
1980.
Multiple changes of penicillin-binding proteins in penicillin-resistant isolates of Streptococcus pneumoniae.
Antimicrob. Agents Chemother.
17:364-371[Abstract/Free Full Text].
|
| 4.
|
Handwereger, A., and A. Tomasz.
1986.
Alterations in kinetic properties of penicillin-binding proteins in penicillin-resistant Streptococcus pneumoniae.
Antimicrob. Agents Chemother.
30:57-63[Abstract/Free Full Text].
|
| 5.
|
Munoz, R.,
C. G. Dowson,
M. Daniels,
T. J. Coffey,
C. Martin,
R. Hakenbeck, and B. G. Spratt.
1992.
Genetics of resistance to third-generation cephalosporins in clinical isolates of Streptococcus pneumoniae.
Mol. Microbiol.
6:2461-2465[Medline].
|
| 6.
|
Percheson, P. B., and L. E. Bryan.
1980.
Penicillin-binding components of penicillin-susceptible and -resistant strains of Streptococcus pneumoniae.
Antimicrob. Agents Chemother.
18:390-396[Abstract/Free Full Text].
|
| 7.
|
Zinghelboim, S., and A. Tomasz.
1980.
Penicillin-binding proteins of multiply antibiotic-resistant South African strains of Streptococcus pneumoniae.
Antimicrob. Agents Chemother.
17:434-442[Abstract/Free Full Text].
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| | | | |
David S. Hodes
Thaddeus E. Sudol
Roche, USA
Nuttley, New Jersey 07110-1199
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AUTHORS' REPLY |
Regarding the comments of Hodes and Sudol, we caution against
overinterpretation of the minor differences between ceftriaxone and
penicillin MICs for isolates of Streptococcus pneumoniae
with low penicillin MICs. As they point out, in our study
(1), ceftriaxone MICs for such strains tended to be
slightly higher than penicillin MICs; however, the differences were
small, i.e., usually ca. 1/2 log2 dilution increment
higher. It is not clear that this difference is meaningful or explained
by different PPP binding affinities. We agree that such a hypothesis
requires further investigation.
| |
REFERENCE |
| 1.
|
Brueggeman, A. B.,
M. A. Pfaller, and G. Doern.
2001.
Use of penicillin MICs to predict in vitro activity of other -lactam antimicrobial agents against Streptococcus pneumoniae.
J. Clin. Microbiol.
39:367-369.
|
| | | | |
Gary V. Doern
Michael Pfaller
Angela A. Brueggeman
Medical Microbiology Division
Department of Pathology
University of Iowa College
of Medicine
Iowa City, Iowa
|
Journal of Clinical Microbiology, December 2001, p. 4597-4597, Vol. 39, No. 12
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.12.4597.2001
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