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Journal of Clinical Microbiology, February 2000, p. 943-943, Vol. 38, No. 2
0095-1137/00/$04.00+0
LETTERS TO THE EDITOR
PCR for Detection of Bacteremia
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LETTER |
This letter refers to the article by Heininger et al.
(1). In the introduction section, the authors mention that
bacteremia is diagnosed in only approximately 4 to 12% of all blood
cultures inoculated in patients with sepsis.
Generally, the denominator for calculating the rate of positivity in
blood cultures is the number of blood cultures processed by the
laboratory. However, one should keep in mind that blood cultures are
inoculated not only to confirm the clinical diagnosis of sepsis
but also to rule out sepsis in other clinical situations, such as
patients with fever and clinical diagnosis of lymphoma, patients with
malaria returning from a tropical country where typhoid fever needs to
be ruled out, etc. If the denominator for calculating the rate of
positive blood cultures is the number of patients with the clinical
diagnosis of sepsis, then up to 63% of blood cultures yield a pathogen
of clinical significance, as we have shown in a prospective study
(2).
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REFERENCES |
| 1.
|
Heininger, A.,
M. Binder,
S. Schmidt,
K. Unertl,
K. Botzenhart, and G. Döring.
1999.
PCR and blood culture for detection of Escherichia coli bacteremia in rats.
J. Clin. Microbiol.
37:2479-2482[Abstract/Free Full Text].
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| 2.
|
Shah, P. M., and R. F. Schaumann.
1997.
Positivitätsrate von Blutkulturen bei Sepsis.
J. Lab. Med.
21:120-121.
|
| | | | |
Pramod M. Shah
Medizinische Klinik III
Schwerpunkt Infectiologie
Johann Wolfgang Goethe-Universität
D-60590 Frankfurt am Main, Germany
|
| |
AUTHOR'S REPLY |
My colleagues and I thank Dr. Pramod Shah for his thoughtful comments
on our publication (1). We agree that the calculation of
positive blood culture (BC) rates strongly depends on the denominator. The rate of 4 to 12% positive mentioned for BCs in our publication (1) refers to BCs in general, without consideration
of the suspected diagnosis of the patients, whereas the rate of
63% positive BC results observed by Dr. Shah refers to samples
collected from patients with clinically diagnosed sepsis. Thus, Dr.
Shah's data are not necessarily in conflict with ours. However,
Dr. Shah's intention most probably was to underline the
suitability of BC, with which we fully agree.
Nevertheless, when BCs are taken from patients treated with
antimicrobial chemotherapy, positive results are rarely obtained. As we
have convincingly described (1), PCR overcomes this problem. Yet, this new method has not been evaluated in the clinical context, and the true rate of bacteremia in patients treated with antibiotics is
still unknown. Also, the PCR technique may create false-negative results. For instance, it is not clear whether human serum DNase degrades bacterial DNA once it has been released after lysis of microorganisms by serum complement or antibiotics in the bloodstream. Little information is available on DNase concentrations and activities on eucaryotic or procaryotic DNA in human blood. Likewise, we do not
know the percentage of DNA released from bacteria during antibiotic
therapy in humans.
False-negative results obtained by BC or PCR might tempt clinicians to
underestimate the spread of a localized infection or to adhere to
an inadequate antimicrobial treatment regimen. Therefore, as a
prerequisite for the assessment of the true rate of bacteremia in
antibiotic-treated patients, further studies need to address the
potential limitations of the PCR method.
| |
REFERENCE |
| 1.
|
Heininger, A.,
M. Binder,
S. Schmidt,
K. Unertl,
K. Botzenhart, and G. Döring.
1999.
PCR and blood culture for detection of Escherichia coli bacteremia in rats.
J. Clin. Microbiol.
37:2479-2482.
|
| | | | |
Alexandra Heininger
Klinik für Anästhesiologie
Universität Tübingen
Hoppe-Seyler Str. 3
D72076 Tübingen, Germany
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Journal of Clinical Microbiology, February 2000, p. 943-943, Vol. 38, No. 2
0095-1137/00/$04.00+0
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[Full Text]
