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Journal of Clinical Microbiology, March 1998, p. 657-661, Vol. 36, No. 3
Institut für Klinikhygiene,
Received 2 September 1997/Returned for modification 14 October
1997/Accepted 24 November 1997
A 20-ml blood sample was collected from adult patients with
suspected bloodstream infections and distributed equally into the four
volume-controlled bottles of a blood culture set consisting of aerobic
and anaerobic BACTEC Plus/F bottles and aerobic and anaerobic
BacT/Alert FAN bottles. All bottles were incubated in their respective
instruments for a standard 5-day protocol or until the instruments
signalled positivity. Samples in all bottles with negative results by
these instruments were terminally subcultured. A total of 8,390 blood
culture sets were obtained during the study period, of which 4,402 (52.5%) met the study criteria. Of these, 946 (21.5%) were positive
either by instrument signal or by additional terminal subculture of all
negative bottles and yielded growth of microorganisms. Five hundred
eighty-nine (13.4%) blood culture sets were considered to have
recovered 663 clinically significant organisms. When both the BACTEC
and the BacT/Alert systems were used, 465 positive sets were detected;
BACTEC alone detected 52 positive sets and BacT/Alert alone detected 72 (P = 0.09). No differences were found between the two
systems in microbial recovery rate from blood cultures obtained from
patients on antibiotic therapy. Significantly more members of the
family Enterobacteriaceae (P < 0.01) were
detected from patients without antimicrobial therapy by BacT/Alert than
by BACTEC. The false-negative rates were 0.20% for BACTEC and 0.32%
for BacT/Alert. A significantly higher false-positive rate was found
for BACTEC (P < 0.0001). Both systems were comparable for the time to detection of microorganisms. However, gram-positive bacteria were detected faster by BACTEC and
Enterobacteriaceae were detected faster on average by
BacT/Alert. We concluded that both systems are comparable in their
abilities to recover aerobic and anaerobic organisms from blood
cultures and a terminal subculture might not be necessary for either of
the two systems. The increased positivity rate when using an anaerobic
bottle in a two-bottle blood culture set is due to the additional blood
volume rather than to the use of an anaerobic medium.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Controlled Clinical Laboratory Comparison of Two Supplemented
Aerobic and Anaerobic Media Used in Automated Blood Culture
Systems To Detect Bloodstream Infections
*
Corresponding author. Mailing address: Institut
für Klinikhygiene, Medizinische Mikrobiologie und Klinische
Infektiologie, Klinikum Nürnberg, Flurstr. 17, 90419 Nürnberg, Germany. Phone: (49) 911 398 2522. Fax: (49) 911 398 3266.
Journal of Clinical Microbiology, March 1998, p. 657-661, Vol. 36, No. 3
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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