Detection of Bacterial and Yeast Species with the Bactec 9120 Automated System with Routine Use of Aerobic, Anaerobic, and Fungal Media

Abstract

Despite recent developments in microbiological biomolecular techniques, blood culture remains the most practical and reliable method in the diagnosis of bloodstream infections and one of the most important tools in the clinical microbiology laboratory, taking into account the role played by systemic infections as a major cause of mortality and morbidity, especially within the hospital environment. Various continuously monitoring blood culture systems are extensively used in order to increase the rapidity of isolation and identification of microorganisms in blood samples, and paired aerobic and anaerobic blood culture bottles are commonly used in order to obtain better overall recovery of microorganisms, as well as the recovery of specific types of bacteria. The traditional aerobic and anaerobic bacteriological media also detect episodes of candidemia, although the sensitivity in this case is estimated to be only 50% (12). The efficiency of yeast detection in blood samples can be increased by terminal subcultures, but the practice is time-consuming and the risk of underestimating yeast infections remains high. This is unacceptable if we take into account the expanding role of yeasts as agents of nosocomial infections, particularly in intensive-care units (ICUs) (4, 18, 23), and candidemia-associated mortality (40%), the highest of all hospital bloodstream infections (4). In order to facilitate faster and more efficient isolation of fungi from blood, the Bactec automated blood culture system (Becton Dickinson Diagnostic Systems, Sparks, MD) has media specifically formulated for this purpose. In addition to the traditional aerobicanaerobic bacteriological set, their use has been recommended when blood culture is required for patients at risk of fungal infections (7, 16) and when a concomitant bloodstream bacterial infection is suspected of inhibiting yeast detection (16).Nevertheless, fungal media are not routinely employed by many hospitals, as they require additional blood from patients, an increased amount of incubator space, and the additional costs of processing and purchasing bottles (10). Moreover, even the routine use of anaerobic bacteriological bottles in blood culture has been (21), and still is (13), a subject of discussion because of the reportedly declining rates of anaerobic bloodstream infections (2) and the possibility of recognizing them clinically and treating affected patients empirically for such infections (17,19,22).

Evaluation of Bactec Mycosis IC/F and Plus Aerobic/F Blood Culture Bottles for Detection of Candida in the Presence of Antifungal Agents

“…The rationale for choosing Bactec MICF bottles for these experiments was that in experiments evaluating the general applicability of different commercial blood culture systems for detecting Candida spp., Bactec MICF bottles, which include supplements specifically adapted for the growth of fungi, were shown to be more sensitive and to detect Candida spp. faster than most other conventional blood culture media (4)(5)(6)(7)(8). This finding was confirmed by the results of our study, since for controls inoculated without antifungal agents, we found reduced median TTPs in MICF bottles compared to those in PAF bottles (21.1 h versus 24.4 h for C. albicans and 22.0 h versus 43.2 h for C. glabrata, respectively).…”

“…Therefore, some studies have evaluated the commercial Bactec system for its ability to detect Candida bloodstream infections. With this system, Bactec Mycosis IC/F (MICF) blood culture bottles, which are specifically adapted to the growth of Candida spp., were demonstrated to have a significantly shorter time to positivity (TTP) and a higher Candida detection rate than conventional (an)aerobic media (such as the Bactec Plus Aerobic F [PAF] and Bactec anaerobic bottles) (4)(5)(6)(7)(8).…”

Three Cases of Fungemia in HIV-Infected Patients Diagnosed Through the Use of Mycobacterial Blood Culture Bottles

“…Because diagnosis and treatment with antifungal agents tend to be delayed in such cases, the mortality rate is high (1,2). Part of the reason for this is that the estimated sensitivity of candidemia detection methods using standard aerobic and anaerobic blood culture bottles is only about 50% (3)(4)(5)(6). Blood culture media for mycobacteria, however, are more suitable for detecting fungi in vitro than these traditional media are (7).…”

Retrospective Evaluation of Aerobic Blood Culture Contamination Rates in a Tertiary Care Hospital in One Year

“…Correct interpretation of blood culture results is one of the main responsibilities of the clinical microbiology laboratory for revealing the existence of these infections. For reducing mortality and morbidity rates, it is important to detect growing microorganisms in a short time, to find out whether they are causative agents or contaminants, and to direct the treatment properly by performing antibiotic susceptibility tests for the microorganisms accepted to be causative agents (1,2). Although various molecular methods, such as nucleic acid probes and polymerase chain reaction (PCR), have been developed for rapid diagnosis, blood culture is still the most sensitive and reliable method.…”