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BACTEC™ // I. PRINCIPLE. The detection of microorganisms in a patient’s blood has diagnostic and prognostic importance. Bactec Plus blood culture bottles were preincubated at 35°C or at room temperature before entry into the Bactec instrument to determine the influence of. The overall recovery of organisms and time to detection with the BACTEC and BACTEC systems were compared in a multicenter.

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A direct comparison of two automated blood culture systems was conducted to compare their ability to detect Candida growth. The aerobic, anaerobic, and mycology media for each system were evaluated: Each blood culture bottle was inoculated with fresh blood from healthy donors. Fifty isolates of Candida spp. The six different blood culture bottles were each inoculated with 1, yeasts per bottle and then incubated in the corresponding automated system.

Growth was detected in all BacT and Bactec mycology bottles, all BacT aerobic bottles, and by terminal subculture of all bottles. The mean time to growth detection in the BacT system was Both automated blood culture systems detected all episodes of simulated candidemia when specialized mycology media were used. However, when only standard aerobic and anaerobic media were used, the BacT performed better than the Bactec in overall growth detection, time to growth detection, and number of false-negatives.

Episodes of candidemia are most commonly detected with standard aerobic and anaerobic blood culture media in automated blood culture systems. Multiple studies have demonstrated effective recovery of Candida spp. Several studies also exist that compare the BacT and Bactec automated blood culture systems 10121417212326 However, these studies address only a small number of candidemia episodes, primarily secondary to Candida albicans.

The predominant cause of candidemia had been C. The ability of automated blood culture systems to detect growth of NAC species has not been thoroughly evaluated. The growth requirements and characteristics may be different than C. In the course of performing a separate study on simulated candidemia in the Bactec, we noted some difficulty in growth detection and time to growth detection among both C.

We therefore performed this study to directly compare the ability of two automated blood culture systems in the detection of the five most common species implicated in candidemia, specifically evaluating growth detection, time to growth detection, and the utility of terminal subcultures with a simulated candidemia model.

Aerobic, anaerobic, and mycology media were evaluated in each automated blood culture system.

This protocol was approved by the institutional review board bacetc Brooke Army Medical Center. Fresh, bachec blood was drawn from healthy volunteers after obtaining written informed consent. All aerobic and anaerobic bottles were inoculated with 10 ml of blood, while mycology bottles were inoculated with 5 ml of blood, per the manufacturer’s recommendations.

Prior to inoculation with blood, the MB bottles were also inoculated with 1 ml of enrichment fluid as recommended by the manufacturer for use with this medium. Fifty clinical isolates of Candida were used in this study, including 10 isolates of each of the following species: A suspension of each specimen was made in 5 ml of normal saline and adjusted to a 0. After the addition of 0. Individual blood culture bottles were removed from the automated blood culture systems when growth was detected and time to detection was recorded.


Blood culture bottles in which no growth was detected were removed from the automated system after 12 days, seven days after the last bottle had growth detected in either automated blood culture system. Terminal subculture was performed on all bottles in which no growth was detected; a 0. Multifactor analysis of variance was followed by Student-Newman-Keuls tests. All bottles were subcultured and demonstrated heavy growth of pure yeast colonies and were therefore true positives.

Three of the six types of media were able to detect growth of all 50 Candida isolates. Growth detection results for each Candida spp. Detection of Candida spp. Terminal subculture was performed on all 65 of the bottles that had no growth detected by the automated blood bactev systems; all of these cultures demonstrated heavy growth of pure yeast colonies, representing 65 false-negatives.

The time to growth detection varied widely depending on the automated blood culture system, type of medium, and Candida spp.

The mean time to growth detection for all Candida spp. Time to Candida spp. Most of the Candida spp. The mean time to growth detection of C. Time to 99240 detection for C. However, few institutions routinely utilize a mycology bottle as a part of all blood culture sets, secondary to the requirement for extra blood and laboratory space.

Additionally, the routine use of mycology media adds a substantial expense; each mycology bottle is approximately three times more expensive than bactce aerobic or anaerobic blood culture bottle.

Unfortunately, candidal and bacterial sepsis can have identical clinical presentations; in order to use the mycology media in a cost-effective manner, the clinician needs to have a high clinical suspicion of candidemia or rely on standard aerobic and anaerobic media for the detection of candidemia. It is interesting that the five isolates not detected by the Bactec aerobic media were all NAC species, including one Bqctec.

This potentially poses a problem for many American hospitals where C.

Interestingly, the only Candida sp. Conversely, all Candida spp. All bactef determined to be false-negatives upon terminal subculture. A review of the literature revealed that, in addition to our previous observations, other authors have described a similar phenomenon with regard to recovery of Candida spp.

There is no consensus in the literature concerning the optimal incubation period required for recovery of yeasts from automated blood culture systems 318 However, there is data to suggest that a 3-day incubation period is sufficient for isolation of clinically relevant bacterial and fungal pathogens, and laboratories may adopt a 3-day incubation period in the future 3. Therefore, time to detection of Candida growth is an important consideration.

The overall difference in time to detection between the two systems can be solely attributed to the delayed time to growth detection of C. We feel these statistical differences do not likely represent clinically significant differences. Bacctec, the mean time to aerobic growth detection is strikingly slower for C.

The aerobic detection of C. The BacT aerobic medium detected C. A closer review of the data also reveals an important finding.

BD BACTEC™ Blood Culture Media – BD

The corresponding time to growth detection of C. Is it actually important for both the aerobic and anaerobic media to detect Candida growth? After all, as long as one bottle of a standard aerobic and anaerobic blood culture set detects Candida growth, the clinician will be able to treat the patient appropriately. It is therefore important to also look at the overlap of missed isolates to determine if there were any missed episodes of simulated candidemia.


Though this may seem adequate, three episodes of candidemia were missed, one C.

Bactec 9240 Blood Culture System, BD Bactec 9240

The BacT batec missed no episodes of candidemia. Recall, bactce, that our isolates were all incubated for a total of 12 days. If a standard 5-day incubation period were employed, the Bactec would have missed an additional episode of C.

Bbactec the incubation period were decreased to only 3 days, two more episodes of C. The BacT system missed no episodes of candidemia, even with the above criteria. However, most clinical laboratories do not routinely use mycology media for all blood cultures. Under these circumstances, when only aerobic and anaerobic media are gactec, the BacT performed better than the BACTEC in overall detection, time to detection, number of false-negatives, and missed episodes of simulated candidemia.

With the increasing prevalence of candidemia among hospitalized patients, particularly secondary to NAC, further investigation is necessary to improve the recovery of all Candida spp. Until improvements in these systems are made, we may need to encourage clinical microbiology laboratories to routinely use mycology media and terminally subculture negative bottles to ensure that episodes of candidemia are not missed.

We also thank Walter Mika for assistance with phlebotomy and John A.

Ward for assistance with statistical analysis of the data. The views expressed are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.

National Center for Biotechnology InformationU. Journal List J Clin Microbiol v. George1 Clinton K. Murray1 Linda S. Harrison2 and Duane R. Author information Article notes Copyright and License information Disclaimer. This article has been cited by other articles in PMC. Abstract A direct comparison of two automated blood culture systems was conducted to compare their ability to detect Candida growth.

Open in a separate window. 2940 time to growth detection of C. Secular trends in the epidemiology of nosocomial fungal infections in the United States, Value of terminal subculture of automated blood cultures in patients with bactc. Nosocomial bloodstream infections in United States hospitals: Controlled clinical comparison of three commercial blood culture systems.

Use of simulated blood cultures to compare a specific fungal medium with a standard microorganism medium for yeast detection. National Committee for Clinical Laboratory Standards. Reference method for broth dilution antifungal susceptibility testing of yeasts; approved standard.

A prospective observational study of candidemia: De La Maza, and E. Clinical comparison of two commercial blood culture systems. Secular trend of hospital-acquired candidemia among intensive care unit patients in the United States during Controlled clinical laboratory comparison of two supplemented 920 and anaerobic media used in automated blood culture systems to detect bloodstream infections. Support Center Support Center.