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

Abstract

Clinical practice guidelines recommend performing follow-up cultures for patients with candidemia in order to determine the time when Candida is cleared from the bloodstream. Since this requires culturing blood samples from patients undergoing antifungal treatment, we evaluated two blood culture bottles (the Bactec Mycosis IC/F [MICF], specifically adapted to the growth of fungi, and the Bactec Plus Aerobic/F [PAF], containing resins to inactivate anti-infective agents) for their effectiveness in detecting Candida albicans and Candida glabrata when seeded in concentrations of 1 CFU/ml and 10 CFU/ml, respectively, together with human whole blood and various antifungal agents in therapeutic peak serum concentrations (C max ). Significant differences between the MICF and PAF vials for the detection of Candida spp. were found when inoculated with caspofungin (0/12 versus 8/12) (P < 0.001) or amphotericin B (3/12 versus 12/12) (P < 0.001). Inoculation of fluconazole or voriconazole did not influence the effectiveness of detection in the MICF and PAF bottles (P ‫؍‬ 1.0). Neither the MICF nor the PAF bottles detected Candida spp. reliably when seeded together with anidulafungin (1/12 versus 1/12) (P ‫؍‬ 1.0) or micafungin (0/12 versus 1/12) (P ‫؍‬ 1.0). The times to positivity of both bottles were significantly prolonged when antifungal agents were added compared to those of controls without antimycotic drugs (P < 0.001). Overall, the results of this in vitro study indicate that the PAF bottles detected Candida spp. more reliably than the MICF bottles when supplemented with certain antifungal agents. Consequently, clinical studies should evaluate whether this holds true when blood cultures from patients undergoing antifungal treatment are performed.

Evaluation of blood culture media for the detection of fungi

“…The advantage of the application of specialized mycological media is evident when analyzing the TTD of typical and rare etiological factors of fungemia. The most relevant difference in the TTD pertains to C. glabrata , which, in our experimental and clinical samples, similarly to other authors, was mostly detected within 24 h in Mycosis and after 2–3 days in Aerobic media [ 5 – 7 ]. It is also worthwhile to notice a complementary role of Anaerobic media, whose ability to detect C. glabrata is higher compared to other fungal species and the detection time is reliably shorter than in Aerobic media (22–40 h, depending on the study) [ 8 , 9 ].…”

“…Another important factor affecting the results of blood cultures is the presence of antifungals. According to Köck et al [ 7 ], Aerobic media showed better performance than Mycosis in blood samples comprising antimycotics, especially caspofungin or amphotericin B. Also, in the study by Ericson et al [ 22 ], the TTD on Mycosis was significantly shorter than in BacT/Alert FA (bioMérieux) vials in patients who did not receive antifungal therapy, whereas in blood samples taken during therapy, the positivity of Mycosis vials was reduced.…”

Rapid Detection and Identification of Candidemia by Direct Blood Culturing on Solid Medium by Use of Lysis-Centrifugation Method Combined with Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry (MALDI-TOF MS)

“…There was a pronounced delay in detecting growth of Candida glabrata by the automated system using an aerobic bottle, which occurred at the 1 CFU/ml concentration 26.6 h after the successful identification of the species from directly inoculated chocolate agar ( Table 1). The delayed detection of C. glabrata using a Bactec Plus aerobic/F bottle was previously reported (5,12). Using a score of Ն1.7 as a criterion for successful identification on a species level (13) provided reliable results without misidentifications compared to those from internal transcribed spacer (ITS) sequencing.…”

“…While early and appropriate treatment is vital (3), the slow growth of yeasts delays a timely diagnosis (4). The current diagnostic standard includes inoculation of the patient's blood into special bottles with liquid medium and incubation in an automated blood culture (BC) instrument (5). In cases where growth is detected, Gram staining is performed and the broth is subcultivated onto a solid medium to grow colonies for identification and antimicrobial susceptibility testing (AST) (4).…”

Performance of Two Resin-Containing Blood Culture Media in Detection of Bloodstream Infections and in Direct Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry (MALDI-TOF MS) Broth Assays for Isolate Identification: Clinical Comparison of the BacT/Alert Plus and Bactec Plus Systems

“…In earlier studies, resinand charcoal-based systems displayed similar recovery rates and TTDs, regardless of whether antibiotics were being administered when the BCs were drawn (13,27,28), but two more recent studies suggested that, in the presence of antibiotics, resin-containing media are superior (14,15). In several studies, both types of media improved recovery and reduced the TTDs of significant pathogens in simulated BCs inoculated with blood containing therapeutic levels of commonly used antibiotics and antifungal agents (29)(30)(31)(32)(33)(34)(35)(36)(37). However, significant differences emerged between the resin-and charcoalbased media relative to specific microorganism-antimicrobial combinations.…”